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Sample records for blazar 1es 1101-232

  1. A Hard X-ray View on Two Distant VHE Blazars: 1ES 1101-232 and 1ES 1553+113

    Energy Technology Data Exchange (ETDEWEB)

    Reimer, A.; Costamente, L.; /Stanford U., HEPL /KIPAC, Menlo Park; Madejski, G.; /KIPAC, Menlo Park /SLAC; Reimer, O.; /Stanford U., HEPL /KIPAC, Menlo Park; Dorner, D.; /Wurzburg U.

    2008-05-02

    TeV-blazars are known as prominent non-thermal emitters across the entire electromagnetic spectrum with their photon power peaking in the X-ray and TeV-band. If distant, absorption of -ray photons by the extragalactic background light (EBL) alters the intrinsic TeV spectral shape, thereby affecting the overall interpretation. Suzaku observations for two of the more distant TeV-blazars known to date, 1ES 1101-232 and 1ES 1553+113, were carried out in May and July 2006, respectively, including a quasi-simultaneous coverage with the state of the art Cherenkov telescope facilities. We report on the resulting data sets with emphasis on the X-ray band, and set into context to their historical behavior. During our campaign, we did not detect any significant X-ray or {gamma}-ray variability. 1ES 1101-232 was found in a quiescent state with the lowest X-ray flux ever measured. The combined XIS and HXD PIN data for 1ES 1101-232 and 1ES 1553+113 clearly indicate spectral curvature up to the highest hard X-ray data point ({approx} 30 keV), manifesting as softening with increasing energy. We describe this spectral shape by either a broken power law or a log-parabolic fit with equal statistical goodness of fits. The combined 1ES 1553+113 very high energy spectrum (90-500 GeV) did not show any significant changes with respect to earlier observations. The resulting contemporaneous broadband spectral energy distributions of both TeV-blazars are discussed in view of implications for intrinsic blazar parameter values, taking into account the {gamma}-ray absorption in the EBL.

  2. Detection of VHE gamma-ray emission from the distant blazar 1ES 1101-232 with H.E.S.S. and broadband characterisation

    CERN Document Server

    Akhperjanian, A G; Beilicke, M; Benbow, W; Berge, D; Bernlöhr, K; Boisson, C; Bolz, O; Borrel, V; Braun, I; Brion, E; Brown, A M; Buhler, R; Büsching, I; Boutelier, T; Carrigan, S; Chadwick, P M; Chounet, L M; Coignet, G; Cornils, R; Costamante, L; Degrange, B; Dickinson, H J; Djannati-Atai, A; O'Connor-Drury, L; Dubus, G; Egberts, K; Emmanoulopoulos, D; Espigat, P; Farnier, C; Feinstein, F; Ferrero, E; Fiasson, A; Fontaine, G; Funk, Seb; Funk, S; Fussling, M; Gallant, Y A; Giebels, B; Glicenstein, J F; Glück, B; Goret, P; Hadjichristidis, C; Hauser, D; Hauser, M; Heinzelmann, G; Henri, G; Hermann, G; Hinton, J A; Hoffmann, A; Hofmann, W; Holleran, M; Hoppe, S; Horns, D; Jacholkowska, A; De Jager, O C; Kendziorra, E; Kerschhaggl, M; Khelifi, B; Komin, Nu; Kosack, K; Lamanna, G; Latham, I J; Le Gallou, R; Lemiere, A; Lemoine-Goumard, M; Lohse, T; Martin, J M; Martineau-Huynh, O; Marcowith, A; Masterson, C; Maurin, G; McComb, T J L; Moulin, E; De Naurois, Mathieu; Nedbal, D; Nolan, S J; Noutsos, A; Olive, J P; Orford, K J; Osborne, J L; Panter, M; Pelletier, G; Petrucci, P O; Pita, S; Pühlhofer, G; Punch, M; Ranchon, S; Raubenheimer, B C; Raue, M; Rayner, S M; Ripken, J; Rob, L; Rolland, L; Rosier-Lees, S; Rowell, G; Sahakian, V V; Santangelo, A; Sauge, L; Schlenker, S; Schlickeiser, R; Schroder, R; Schwanke, U; Schwarzburg, S; Schwemmer, S; Shalchi, A; Sol, H; Spangler, D; Spanier, F; Steenkamp, R; Stegmann, C; Superina, G; Tam, P H; Tavernet, J P; Terrier, R; Tluczykont, M; Van Eldik, C; Vasileiadis, G; Venter, C; Vialle, J P; Vincent, P; Völk, H J; Wagner, S J; Ward, M

    2007-01-01

    The blazar 1ES 1101-232 was observed with the High Energy Stereoscopic System (H.E.S.S.) of Atmospheric Cherenkov Telescopes (ACT) in 2004 and 2005, for a live time of 43 hours. VHE (E > 10^11 eV) gamma-rays were detected for the first time from this object. VHE observations of blazars are used to investigate the inner parts of the blazar jets, and also to study the extragalactic background light (EBL) in the near-infrared band. Observations in 2005 were conducted in a multiwavelength campaign, together with the RXTE satellite and optical observations. In 2004, simultaneous observations with XMM-Newton were obtained. 1ES 1101-232 was detected with H.E.S.S. with an excess of 722 photons, at a significance of 12 sigma. The measured VHE gamma-ray flux amounts to dN/dE = (5.63 +- 0.89) x 10^-13 (E/TeV)^-(2.94 +- 0.20) cm^-2 s^-1 TeV^-1, above a spectral energy threshold of 225 GeV. No significant variation of the VHE gamma-ray flux on any time scale was found. 1ES 1101-232 exhibits a very hard spectrum, and at a ...

  3. Hard synchrotron BL Lacs: the case of 1ES 1101-232

    OpenAIRE

    Wolter, Anna; Ghisellini, Gabriele; Tagliaferri, Gianpiero; Tavecchio, Fabrizio; Caccianiga, Alessandro

    2000-01-01

    The bright X-ray selected BL Lac object 1ES1101--232 shows a flat X-ray spectrum, making it detectable with high statistics over the wide BeppoSAX energy range. We have observed it in two different epochs with BeppoSAX, and found a variation of the flux of about 30% that can be explained by a change in the spectral index above the synchrotron peak. We present here the data and infer limits on the strength of the magnetic field based on models of emission for High-frequency peaked BL Lacs.

  4. X-ray variability and prediction of TeV emission in the HBL 1ES1101-232

    OpenAIRE

    Wolter, A.; Tavecchio, F.; Caccianiga, A.; Ghisellini, G.; Tagliaferri, G.

    2000-01-01

    1ES1101-232 is a bright BL Lac of the High frequency peak class. We present here the results of two BeppoSAX observations in which the source has shown a variation of about 30% in flux with a corresponding spectral variability. We interpret the overall spectral energy distribution in terms of an homogeneous SSC model and, by using also the TeV upper limit from a short Mark 6 pointing, derive constraints on the physical parameters of the source, in particular on the magnetic field strength. Th...

  5. -Ray Emission from the Extreme Blazar 1ES 0229+200

    Indian Academy of Sciences (India)

    J. Li; T. Kang; Y. G. Zheng

    2014-09-01

    Based on the traditional Synchrotron Self-Compton (SSC) model, we consider a secondary γ -ray emission component to an extreme blazar 1ES 0229 + 200 for the multiwavelength radiation. By assuming a suitable electron spectra and Inter-Galactic Magnetic Field (IGMF), we obtained excellent fits to observed spectra of the source. This indicated that the observed excess GeV -rays emission can be explained by secondary -rays produced through inverse Compton scattering of ± pairs against Cosmic Microwave Background (CMB) photons.

  6. Investigating Broadband Variability of the TeV Blazar 1ES 1959+650

    CERN Document Server

    Aliu, E; Arlen, T; Aune, T; Barnacka, A; Beilicke, M; Benbow, W; Berger, K; Bird, R; Bouvier, A; Buckley, J H; Bugaev, V; Cerruti, M; Chen, X; Ciupik, L; Collins-Hughes, E; Connolly, M P; Cui, W; Dumm, J; Eisch, J D; Falcone, A; Federici, S; Feng, Q; Finley, J P; Fleischhack, H; Fortin, P; Fortson, L; Furniss, A; Galante, N; Gillanders, G H; Griffin, S; Griffiths, S T; Grube, J; Gyuk, G; Hakansson, N; Hanna, D; Holder, J; Hughes, G; Humensky, T B; Johnson, C A; Kaaret, P; Kar, P; Kertzman, M; Khassen, Y; Kieda, D; Krawczynski, H; Krennrich, F; Lang, M J; Madhavan, A S; Majumdar, P; McArthur, S; McCann, A; Meagher, K; Millis, J; Moriarty, P; Mukherjee, R; Nelson, T; Nieto, D; de Bhroithe, A O'Faolain; Ong, R A; Otte, A N; Park, N; Perkins, J S; Pohl, M; Popkow, A; Prokoph, H; Quinn, J; Ragan, K; Rajotte, J; Reyes, L C; Reynolds, P T; Richards, G T; Roache, E; Sadun, A; Santander, M; Sembroski, G H; Shahinyan, K; Sheidaei, F; Smith, A W; Staszak, D; Telezhinsky, I; Theiling, M; Tyler, J; Varlotta, A; Vassiliev, V V; Vincent, S; Wakely, S P; Weekes, T C; Weinstein, A; Welsing, R; Wilhelm, A; Williams, D A; Zitzer, B; Böttcher, M; Fumagalli, M

    2014-01-01

    We summarize broadband observations of the TeV-emitting blazar 1ES 1959+650, including optical R-band observations by the robotic telescopes Super-LOTIS and iTelescope, UV observations by Swift UVOT, X-ray observations by the Swift X-ray Telescope (XRT), high-energy gamma-ray observations with the Fermi Large Area Telescope (LAT) and very-high-energy (VHE) gamma-ray observations by VERITAS above 315 GeV, all taken between 17 April 2012 and 1 June 2012 (MJD 56034 and 56079). The contemporaneous variability of the broadband spectral energy distribution is explored in the context of a simple synchrotron self Compton (SSC) model. In the SSC emission scenario, we find that the parameters required to represent the high state are significantly different than those in the low state. Motivated by possible evidence of gas in the vicinity of the blazar, we also investigate a reflected-emission model to describe the observed variability pattern. This model assumes that the non-thermal emission from the jet is reflected b...

  7. Multiwavelength Observations of the VHE Blazar 1ES 2344+514

    CERN Document Server

    Acciari, V A; Arlen, T; Aune, T; Beilicke, M; Benbow, W; Boltuch, D; Bugaev, V; Cannon, A; Ciupik, L; Cogan, P; Colin, P; Dickherber, R; Falcone, A; Fegan, S J; Finley, J P; Fortin, P; Fortson, L F; Furniss, A; Gall, D; Gillanders, G H; Grube, J; Guenette, R; Gyuk, G; Hanna, D; Holder, J; Horan, D; Hui, C M; Humensky, T B; Imran, A; Kaaret, P; Karlsson, N; Kertzman, M; Kieda, D; Kildea, J; Konopelko, A; Krawczynski, H; Krennrich, F; Lang, M J; LeBohec, S; Maier, G; Moriarty, P; Mukherjee, R; Ong, R A; Otte, A N; Pandel, D; Perkins, J S; Pichel, A; Pohl, M; Quinn, J; Ragan, K; Reynolds, P T; Rose, H J; Schroedter, M; Sembroski, G H; Smith, A W; Steele, D; Swordy, S P; Theiling, M; Toner, J A; Varlotta, A; Vassiliev, V V; Vincent, S; Wagner, R; Wakely, S P; Ward, J E; Weekes, T C; Weinstein, A; Weisgarber, T; Williams, D A; Wissel, S; Wood, M; Zitzer, B

    2011-01-01

    Multiwavelength observations of the high-frequency-peaked blazar 1ES2344+514 were performed from 2007 October to 2008 January. The campaign represents the first contemporaneous data on the object at very high energy (VHE, E >100 GeV) {\\gamma}-ray, X-ray, and UV energies. Observations with VERITAS in VHE {\\gamma}-rays yield a strong detection of 20 {\\sigma} with 633 excess events in a total exposure of 18.1 hours live-time. A strong VHE {\\gamma}-ray flare on 2007 December 7 is measured at F(>300 GeV) = (6.76 \\pm 0.62) \\times 10-11 ph cm-2 s-1, corresponding to 48% of the Crab Nebula flux. Excluding this flaring episode, nightly variability at lower fluxes is observed with a time-averaged mean of F(>300 GeV) = (1.06 \\pm 0.09) \\times 10-11 ph cm-2 s-1 (7.6% of the Crab Nebula flux). The differential photon spectrum between 390 GeV and 8.3 TeV for the time-averaged observations excluding 2007 December 7 is well described by a power law with a photon index of {\\Gamma} = 2.78 \\pm 0.09stat \\pm 0.15syst. Over the ful...

  8. Evidence for the Secondary Emission as the Origin of Hard Spectra in TeV Blazars

    CERN Document Server

    Zheng, Y G

    2016-01-01

    We develop a model for a possible origin of hard very high energy spectra from a distant blazar. In the model, both the primary photons produced in the source and secondary photons produced outside the source contribute to the observed high energy $\\gamma$-rays emission. That is, the primary photons are produced in the source through the synchrotron self-Compton (SSC) process, and the secondary photons are produced outside the source through high energy protons interaction with the background photons along the line of sight. We apply the model to a characteristic case was the very high energy (VHE) $\\gamma$-ray emissions in distant blazar 1ES 1101-232. Assuming a suitable electron and proton spectra, we obtain excellent fits to observed spectra of distant blazar 1ES 1101-232. This indicated that the surprisingly low attenuation of high energy $\\gamma$-rays, especially for the shape of the very high energy $\\gamma$-rays tail of the observed spectra, can be explained by secondary $\\gamma$-rays produced in inter...

  9. Multiwavelength observations of the blazar 1ES 1011+496 in Spring 2008

    Science.gov (United States)

    Ahnen, M. L.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Babic, A.; Banerjee, B.; Bangale, P.; de Almeida, U. Barres; Barrio, J. A.; González, J. Becerra; Bednarek, W.; Bernardini, E.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Carmona, E.; Carosi, A.; Chatterjee, A.; Clavero, R.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Caneva, G.; De Lotto, B.; de Oña Wilhelmi, E.; Mendez, C. Delgado; Pierro, F. Di; Prester, D. Dominis; Dorner, D.; Doro, M.; Einecke, S.; Elsaesser, D.; Fernández-Barral, A.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Frantzen, K.; Fruck, C.; Galindo, D.; López, R. J. García; Garczarczyk, M.; Terrats, D. Garrido; Gaug, M.; Giammaria, P.; (Eisenacher), D. Glawion; Godinović, N.; Muñoz, A. González; Guberman, D.; Hanabata, Y.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Hughes, G.; Idec, W.; Kodani, K.; Konno, Y.; Kubo, H.; Kushida, J.; Barbera, A. La; Lelas, D.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; López-Coto, R.; López-Oramas, A.; Lorenz, E.; Majumdar, P.; Makariev, M.; Mallot, K.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Nakajima, D.; Neustroev, V.; Niedzwiecki, A.; Rosillo, M. Nievas; Nilsson, K.; Nishijima, K.; Noda, K.; Orito, R.; Overkemping, A.; Paiano, S.; Palacio, J.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Persic, M.; Poutanen, J.; Moroni, P. G. Prada; Prandini, E.; Puljak, I.; Reinthal, R.; Rhode, W.; Ribó, M.; Rico, J.; Garcia, J. Rodriguez; Rügamer, S.; Saito, T.; Satalecka, K.; Scapin, V.; Schultz, C.; Schweizer, T.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Stamerra, A.; Steinbring, T.; Strzys, M.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Thaele, J.; Torres, D. F.; Toyama, T.; Treves, A.; Verguilov, V.; Vovk, I.; Ward, J. E.; Will, M.; Wu, M. H.; Zanin, R.; Lucarelli, F.; Pittori, C.; Vercellone, S.; Berdyugin, A.; Carini, M. T.; Lähteenmäki, A.; Pasanen, M.; Pease, A.; Sainio, J.; Tornikoski, M.; Walters, R.

    2016-07-01

    The BL Lac object 1ES 1011+496 was discovered at very high energy (VHE, E > 100GeV) γ-rays by Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) in Spring 2007. Before that the source was little studied in different wavelengths. Therefore, a multiwavelength (MWL) campaign was organized in Spring 2008. Along MAGIC, the MWL campaign included the Metsähovi Radio Observatory, Bell and Kungliga Vetenskapsakademien (KVA) optical telescopes and the Swift and AGILE satellites. MAGIC observations span from 2008 March to May for a total of 27.9 h, of which 19.4 h remained after quality cuts. The light curve showed no significant variability yielding an integral flux above 200 GeV of (1.3 ± 0.3) × 10-11 photons cm-2 s-1. The differential VHE spectrum could be described with a power-law function with a spectral index of 3.3 ± 0.4. Both results were similar to those obtained during the discovery. Swift X-ray Telescope observations revealed an X-ray flare, characterized by a harder-when-brighter trend, as is typical for high synchrotron peak BL Lac objects (HBL). Strong optical variability was found during the campaign, but no conclusion on the connection between the optical and VHE γ-ray bands could be drawn. The contemporaneous spectral energy distribution shows a synchrotron-dominated source, unlike concluded in previous work based on non-simultaneous data, and is well described by a standard one-zone synchrotron self-Compton model. We also performed a study on the source classification. While the optical and X-ray data taken during our campaign show typical characteristics of an HBL, we suggest, based on archival data, that 1ES 1011+496 is actually a borderline case between intermediate and high synchrotron peak frequency BL Lac objects.

  10. Simultaneous Multiwavelength Observations of the Blazar 1ES 1959+650 at a Low TeV Flux

    International Nuclear Information System (INIS)

    We present the results from a multiwavelength campaign on the TeV blazar 1ES 1959+650, performed in 2006 May. Data from the optical, UV, soft- and hard-X-ray, and very high energy (VHE) gamma-ray (E > 100 GeV) bands were obtained with the Suzaku and Swift satellites, the MAGIC telescope, and other ground-based facilities. The source spectral energy distribution (SED), derived from Suzaku and MAGIC observations at the end of 2006 May, shows the usual double hump shape, with the synchrotron peak at a higher flux level than the Compton peak. With respect to historical values, during our campaign the source exhibited a relatively high state in X-rays and optical, while in the VHE band it was at one of the lowest level so far recorded. We also monitored the source for flux spectral variability on a time window of 10 days in the optical-UV and X-ray bands and 7 days in the VHE band. The source varies more in the X-ray than in the optical band, with the 2-10 keV X-ray flux varying by a factor of ∼2. The synchrotron peak is located in the X-ray band and moves to higher energies as the source gets brighter, with the X-ray fluxes above it varying more rapidly than the X-ray fluxes at lower energies. The variability behavior observed in the X-ray band cannot be produced by emitting regions varying independently and suggests instead some sort of 'standing shock' scenario. The overall SED is well represented by a homogeneous one-zone synchrotron inverse Compton emission model, from which we derive physical parameters that are typical of high-energy peaked blazars.

  11. Multi-Wavelength Observations of the Blazar 1ES 1011+496 in Spring 2008

    CERN Document Server

    Ahnen, M L; Antonelli, L A; Antoranz, P; Babic, A; Banerjee, B; Bangale, P; de Almeida, U Barres; Barrio, J A; Gonzalez, J Becerra; Bednarek, W; Bernardini, E; Biasuzzi, B; Biland, A; Blanch, O; Bonnefoy, S; Bonnoli, G; Borracci, F; Bretz, T; Carmona, E; Carosi, A; Chatterjee, A; Clavero, R; Colin, P; Colombo, E; Contreras, J L; Cortina, J; Covino, S; Da Vela, P; Dazzi, F; De Angelis, A; De Caneva, G; De Lotto, B; Wilhelmi, E de Ona; Mendez, C Delgado; Di Pierro, F; Prester, D Dominis; Dorner, D; Doro, M; Einecke, S; Elsaesser, D; Fernandez-Barral, A; Fidalgo, D; Fonseca, M V; Font, L; Frantzen, K; Fruck, C; Galindo, D; Lopez, R J Garcia; Garczarczyk, M; Terrats, D Garrido; Gaug, M; Giammaria, P; Glawion, D; Godinovic, N; Munoz, A Gonzalez; Guberman, D; Hanabata, Y; Hayashida, M; Herrera, J; Hose, J; Hrupec, D; Hughes, G; Idec, W; Kodani, K; Konno, Y; Kubo, H; Kushida, J; La Barbera, A; Lelas, D; Lindfors, E; Lombardi, S; Longo, F; Lopez, M; Lopez-Coto, R; Lopez-Oramas, A; Lorenz, E; Majumdar, P; Makariev, M; Mallot, K; Maneva, G; Manganaro, M; Mannheim, K; Maraschi, L; Marcote, B; Mariotti, M; Martinez, M; Mazin, D; Menzel, U; Miranda, J M; Mirzoyan, R; Moralejo, A; Nakajima, D; Neustroev, V; Niedzwiecki, A; Rosillo, M Nievas; Nilsson, K; Nishijima, K; Noda, K; Orito, R; Overkemping, A; Paiano, S; Palacio, J; Palatiello, M; Paneque, D; Paoletti, R; Paredes, J M; Paredes-Fortuny, X; Persic, M; Poutanen, J; Moroni, P G Prada; Prandini, E; Puljak, I; Reinthal, R; Rhode, W; Ribo, M; Rico, J; Garcia, J Rodriguez; Rugamer, S; Saito, T; Satalecka, K; Scapin, V; Schultz, C; Schweizer, T; Shore, S N; Sillanpaa, A; Sitarek, J; Snidaric, I; Sobczynska, D; Stamerra, A; Steinbring, T; Strzys, M; Takalo, L; Takami, H; Tavecchio, F; Temnikov, P; Terzic, T; Tescaro, D; Teshima, M; Thaele, J; Torres, D F; Toyama, T; Treves, A; Verguilov, V; Vovk, I; Ward, J E; Will, M; Wu, M H; Zanin, R; Lucarelli, F; Pittori, C; Berdyugin, A; Carini, M T; Lahteenmaki, A; Pasanen, M; Pease, A; Sainio, J; Tornikoski, M; Walters, R

    2016-01-01

    The BL Lac object 1ES 1011+496 was discovered at Very High Energy gamma-rays by MAGIC in spring 2007. Before that the source was little studied in different wavelengths. Therefore a multi-wavelength (MWL) campaign was organized in spring 2008. Along MAGIC, the MWL campaign included the Metsahovi radio observatory, Bell and KVA optical telescopes and the Swift and AGILE satellites. MAGIC observations span from March to May, 2008 for a total of 27.9 hours, of which 19.4 hours remained after quality cuts. The light curve showed no significant variability. The differential VHE spectrum could be described with a power-law function. Both results were similar to those obtained during the discovery. Swift XRT observations revealed an X-ray flare, characterized by a harder when brighter trend, as is typical for high synchrotron peak BL Lac objects (HBL). Strong optical variability was found during the campaign, but no conclusion on the connection between the optical and VHE gamma-ray bands could be drawn. The contempo...

  12. LONG-TERM OPTICAL POLARIZATION VARIABILITY OF THE TeV BLAZAR 1ES 1959+650

    Energy Technology Data Exchange (ETDEWEB)

    Sorcia, Marco; Benitez, Erika; Cabrera, Jose I. [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Apdo. 70-264, Mexico D.F. 04510 (Mexico); Hiriart, David; Lopez, Jose M. [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Apdo. 810, Ensenada, B.C. 22800 (Mexico); Mujica, Raul [Instituto Nacional de Astrofisica, Optica y Electronica, Apdo. Postal 51 y 216, 72000 Tonantzintla, Puebla (Mexico); Heidt, Jochen; Mommert, Michael [ZAH, Landessternwarte Heidelberg, Koenigstuhl, D-69117 Heidelberg (Germany); Agudo, Ivan [Instituto Nacional de Astrofisica de Andalucia, CSIC, Apartado 3004, E-18080 Granada (Spain); Nilsson, Kari, E-mail: msorcia@astro.unam.mx [Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Vaeisaelaentie 20, FI-21500 Piikkioe (Finland)

    2013-06-01

    A detailed analysis of the optical polarimetric variability of the TeV blazar 1ES 1959+650 from 2007 October 18 to 2011 May 5 is presented. The source showed maximum and minimum brightness states in the R band of 14.08 {+-} 0.03 mag and 15.20 {+-} 0.03 mag, respectively, with a maximum variation of 1.12 mag, and a maximum polarization degree of P = (12.2 {+-} 0.7)%, with a maximum variation of 10.7%. From 2009 August to November, a correlation between the optical R-band flux and the degree of linear polarization was found with a correlation coefficient r {sub pol} = 0.984 {+-} 0.025. The source presented a preferential position angle of optical polarization of {approx}153 Degree-Sign , with variations of 10 Degree-Sign -50 Degree-Sign , which is in agreement with the projected position angle of the parsec-scale jet found at 43 GHz. From the Stokes parameters we infer the existence of two optically thin synchrotron components that contribute to the polarized flux. One of them is stable with a constant polarization degree of 4%. Assuming a stationary shock for the variable component, we estimated some parameters associated with the physics of the relativistic jet: the magnetic field, B {approx} 0.06 G, the Doppler factor, {delta}{sub 0} {approx} 23, the viewing angle, {Phi} {approx} 2. Degree-Sign 4, and the size of the emission region r{sub b} {approx} 5.6 Multiplication-Sign 10{sup 17} cm. Our study is consistent with the spine-sheath model of explaining the polarimetric variability displayed by this source during our monitoring.

  13. Discovery of very high energy gamma-ray emission from the blazar 1ES 0033+595 by the MAGIC telescopes

    CERN Document Server

    Aleksić, J; Antonelli, L A; Antoranz, P; Babic, A; Bangale, P; de Almeida, U Barres; Barrio, J A; González, J Becerra; Bednarek, W; Berger, K; Bernardini, E; Biland, A; Blanch, O; Bonnefoy, S; Bonnoli, G; Borracci, F; Bretz, T; Carmona, E; Carosi, A; Fidalgo, D Carreto; Colin, P; Colombo, E; Contreras, J L; Cortina, J; Covino, S; Da Vela, P; Dazzi, F; De Angelis, A; De Caneva, G; De Lotto, B; Mendez, C Delgado; Doert, M; Domínguez, A; Prester, D Dominis; Dorner, D; Doro, M; Einecke, S; Eisenacher, D; Elsaesser, D; Farina, E; Ferenc, D; Fonseca, M V; Font, L; Frantzen, K; Fruck, C; López, R J García; Garczarczyk, M; Terrats, D Garrido; Gaug, M; Godinović, N; Muñoz, A González; Gozzini, S R; Hadasch, D; Hayashida, M; Herrera, J; Herrero, A; Hildebrand, D; Hose, J; Hrupec, D; Idec, W; Kadenius, V; Kellermann, H; Kodani, K; Konno, Y; Krause, J; Kubo, H; Kushida, J; La Barbera, A; Lelas, D; Lewandowska, N; Lindfors, E; Lombardi, S; López, M; López-Coto, R; López-Oramas, A; Lorenz, E; Lozano, I; Makariev, M; Mallot, K; Maneva, G; Mankuzhiyil, N; Mannheim, K; Maraschi, L; Marcote, B; Mariotti, M; Martínez, M; Mazin, D; Menzel, U; Meucci, M; Miranda, J M; Mirzoyan, R; Moralejo, A; Munar-Adrover, P; Nakajima, D; Niedzwiecki, A; Nilsson, K; Nishijima, K; Noda, K; Nowak, N; Orito, R; Overkemping, A; Paiano, S; Palatiello, M; Paneque, D; Paoletti, R; Paredes, J M; Paredes-Fortuny, X; Partini, S; Persic, M; Prada, F; Moroni, P G Prada; Prandini, E; Preziuso, S; Puljak, I; Reinthal, R; Rhode, W; Ribó, M; Rico, J; Garcia, J Rodriguez; Rügamer, S; Saggion, A; Saito, T; Saito, K; Satalecka, K; Scalzotto, V; Scapin, V; Schultz, C; Schweizer, T; Shore, S N; Sillanpää, A; Sitarek, J; Snidaric, I; Sobczynska, D; Spanier, F; Stamatescu, V; Stamerra, A; Steinbring, T; Storz, J; Sun, S; Surić, T; Takalo, L; Takami, H; Tavecchio, F; Temnikov, P; Terzić, T; Tescaro, D; Teshima, M; Thaele, J; Tibolla, O; Torres, D F; Toyama, T; Treves, A; Uellenbeck, M; Vogler, P; Wagner, R M; Zandanel, F; Zanin, R; Tronconi, V; Buson, S

    2014-01-01

    The number of known very high energy (VHE) blazars is $\\sim\\,50$, which is very small in comparison to the number of blazars detected in other frequencies. This situation is a handicap for population studies of blazars, which emit about half of their luminosity in the $\\gamma$-ray domain. Moreover, VHE blazars, if distant, allow for the study of the environment that the high-energy $\\gamma$-rays traverse in their path towards the Earth, like the extragalactic background light (EBL) and the intergalactic magnetic field (IGMF), and hence they have a special interest for the astrophysics community. We present the first VHE detection of 1ES\\,0033+595 with a statistical significance of 5.5\\,$\\sigma$. The VHE emission of this object is constant throughout the MAGIC observations (2009 August and October), and can be parameterized with a power law with an integral flux above 150 GeV of $(7.1\\pm1.3)\\times 10^{-12} {\\mathrm{ph\\,cm^{-2}\\,s^{-1}}}$ and a photon index of ($3.8\\pm0.7$). We model its spectral energy distrib...

  14. H.E.S.S and Fermi-LAT discovery of gamma rays from the blazar 1ES 1312-423

    CERN Document Server

    Abramowski, A; Aharonian, F; Akhperjanian, A G; Angüner, E; Anton, G; Balenderan, S; Balzer, A; Barnacka, A; Becherini, Y; Tjus, J Becker; Bernlöhr, K; Birsin, E; Bissaldi, E; Biteau, J; Boisson, C; Bolmont, J; Bordas, P; Brucker, J; Brun, F; Brun, P; Bulik, T; Carrigan, S; Casanova, S; Cerruti, M; Chadwick, P M; Chalme-Calvet, R; Chaves, R C G; Cheesebrough, A; Chrétien, M; Colafrancesco, S; Cologna, G; Conrad, J; Couturier, C; Dalton, M; Daniel, M K; Davids, I D; Degrange, B; Deil, C; deWilt, P; Dickinson, H J; Djannati-Ataï, A; Domainko, W; Drury, L O'C; Dubus, G; Dutson, K; Dyks, J; Dyrda, M; Edwards, T; Egberts, K; Eger, P; Espigat, P; Farnier, C; Fegan, S; Feinstein, F; Fernandes, M V; Fernandez, D; Fiasson, A; Fontaine, G; Förster, A; Füßling, M; Gajdus, M; Gallant, Y A; Garrigoux, T; Gast, H; Giebels, B; Glicenstein, J F; Göring, D; Grondin, M -H; Grudzińska, M; Häffner, S; Hague, J D; Hahn, J; Harris, J; Heinzelmann, G; Henri, G; Hermann, G; Hervet, O; Hillert, A; Hinton, J A; Hofmann, W; Hofverberg, P; Holler, M; Horns, D; Jacholkowska, A; Jahn, C; Jamrozy, M; Janiak, M; Jankowsky, F; Jung, I; Kastendieck, M A; Katarzyński, K; Katz, U; Kaufmann, S; Khélifi, B; Kieffer, M; Klepser, S; Klochkov, D; Kluźniak, W; Kneiske, T; Kolitzus, D; Komin, Nu; Kosack, K; Krakau, S; Krayzel, F; Krüger, P P; Laffon, H; Lamanna, G; Lefaucheur, J; Lemoine-Goumard, M; Lenain, J -P; Lennarz, D; Lohse, T; Lopatin, A; Lu, C -C; Marandon, V; Marcowith, A; Maurin, G; Maxted, N; Mayer, M; McComb, T J L; Medina, M C; Méhault, J; Menzler, U; Meyer, M; Moderski, R; Mohamed, M; Moulin, E; Murach, T; Naumann, C L; de Naurois, M; Nedbal, D; Niemiec, J; Nolan, S J; Oakes, L; Ohm, S; de OñaWilhelmi, E; Opitz, B; Ostrowski, M; Oya, I; Panter, M; Parsons, R D; Arribas, M Paz; Pekeur, N W; Pelletier, G; Perez, J; Petrucci, P -O; Peyaud, B; Pita, S; Poon, H; Pühlhofer, G; Punch, M; Quirrenbach, A; Raab, S; Raue, M; Reimer, A; Reimer, O; Renaud, M; Reyes, R de los; Rieger, F; Rob, L; Rosier-Lees, S; Rowell, G; Rudak, B; Rulten, C B; Sahakian, V; Sanchez, D A; Santangelo, A; Schlickeiser, R; Schüssler, F; Schulz, A; Schwanke, U; Schwarzburg, S; Schwemmer, S; Sol, H; Spengler, G; Spieß, F; Stawarz, {Ł }; Steenkamp, R; Stegmann, C; Stinzing, F; Stycz, K; Sushch, I; Szostek, A; Tavernet, J -P; Terrier, R; Tluczykont, M; Trichard, C; Valerius, K; van Eldik, C; Vasileiadis, G; Venter, C; Viana, A; Vincent, P; Völk, H J; Volpe, F; Vorster, M; Wagner, S J; Wagner, P; Ward, M; Weidinger, M; White, R; Wierzcholska, A; Willmann, P; Wörnlein, A; Wouters, D; Zacharias, M; Zajczyk, A; Zdziarski, A A; Zech, A; Zechlin, H -S; Perkins, J S; Ojha, R; Stevens, J; Edwards, P G; Kadler, M

    2013-01-01

    A deep observation campaign carried out by the High Energy Stereoscopic System (H.E.S.S.) on Centaurus A enabled the discovery of gamma rays from the blazar 1ES 1312-423, two degrees away from the radio galaxy. With a differential flux at 1 TeV of (1.9 +/-0.6(stat) +/-0.4(sys)) x 10^{-13} /cm^2 /s /TeV corresponding to 0.5% of the Crab nebula differential flux and a spectral index of 2.9 +/- 0.5 (stat) +/- 0.2 (sys), 1ES 1312-423 is one of the faintest sources ever detected in the very high energy (E>100 GeV) extragalactic sky. A careful analysis using three and a half years of Fermi-LAT data allows the discovery at high energies (E>100 MeV) of a hard spectrum (index of 1.4 +/- 0.4 (stat) +/- 0.2 (sys)) source coincident with 1ES 1312-423. Radio, optical, UV and X-ray observations complete the spectral energy distribution of this blazar, now covering 16 decades in energy. The emission is successfully fitted with a synchrotron self Compton model for the non-thermal component, combined with a black-body spectru...

  15. Discovery of very high energy gamma-ray emission from the blazar 1ES 1727+502 with the MAGIC Telescopes

    CERN Document Server

    Aleksić, J; Antoranz, P; Asensio, M; Backes, M; de Almeida, U Barres; Barrio, J A; González, J Becerra; Bednarek, W; Berger, K; Bernardini, E; Biland, A; Blanch, O; Bock, R K; Boller, A; Bonnefoy, S; Bonnoli, G; Tridon, D Borla; Borracci, F; Bretz, T; Carmona, E; Carosi, A; Fidalgo, D Carreto; Colin, P; Colombo, E; Contreras, J L; Cortina, J; Cossio, L; Covino, S; Da Vela, P; Dazzi, F; De Angelis, A; De Caneva, G; De Lotto, B; Mendez, C Delgado; Doert, M; Domínguez, A; Prester, D Dominis; Dorner, D; Doro, M; Eisenacher, D; Elsaesser, D; Farina, E; Ferenc, D; Fonseca, M V; Font, L; Fruck, C; López, R J García; Garczarczyk, M; Terrats, D Garrido; Gaug, M; Giavitto, G; Godinović, N; Muñoz, A González; Gozzini, S R; Hadamek, A; Hadasch, D; Häfner, D; Herrero, A; Hose, J; Hrupec, D; Idec, W; Jankowski, F; Kadenius, V; Klepser, S; Knoetig, M L; Krähenbühl, T; Krause, J; Kushida, J; La Barbera, A; Lelas, D; Lewandowska, N; Lindfors, E; Lombardi, S; López, M; López-Coto, R; López-Oramas, A; Lorenz, E; Lozano, I; Makariev, M; Mallot, K; Maneva, G; Mankuzhiyil, N; Mannheim, K; Maraschi, L; Marcote, B; Mariotti, M; Martínez, M; Masbou, J; Mazin, D; Meucci, M; Miranda, J M; Mirzoyan, R; Moldón, J; Moralejo, A; Munar-Adrover, P; Nakajima, D; Niedzwiecki, A; Nilsson, K; Nowak, N; Orito, R; Paiano, S; Palatiello, M; Paneque, D; Paoletti, R; Paredes, J M; Partini, S; Persic, M; Prada, F; Moroni, P G Prada; Prandini, E; Puljak, I; Reichardt, I; Reinthal, R; Rhode, W; Ribó, M; Rico, J; Rügamer, S; Saggion, A; Saito, K; Saito, T Y; Salvati, M; Satalecka, K; Scalzotto, V; Scapin, V; Schultz, C; Schweizer, T; Shore, S N; Sillanpää, A; Sitarek, J; Snidaric, I; Sobczynska, D; Spanier, F; Spiro, S; Stamatescu, V; Stamerra, A; Steinke, B; Storz, J; Sun, S; Surić, T; Takalo, L; Takami, H; Tavecchio, F; Temnikov, P; Terzić, T; Tescaro, D; Teshima, M; Tibolla, O; Torres, D F; Toyama, T; Treves, A; Uellenbeck, M; Vogler, P; Wagner, R M; Weitzel, Q; Zandanel, F; Zanin, R

    2013-01-01

    Motivated by the Costamante & Ghisellini (2002) predictions we investigated if the blazar 1ES 1727+502 (z=0.055) is emitting very high energy (VHE, E>100 GeV) gamma rays. We observed the BL Lac object 1ES 1727+502 in stereoscopic mode with the two MAGIC telescopes during 14 nights between May 6th and June 10th 2011, for a total effective observing time of 12.6 hours. For the study of the multiwavelength spectral energy distribution (SED) we use simultaneous optical R-band data from the KVA telescope, archival UV/optical and X-ray observations by instruments UVOT and XRT on board of the Swift satellite and high energy (HE, 0.1 GeV - 100 GeV) gamma-ray data from the Fermi-LAT instrument. We detect, for the first time, VHE gamma-ray emission from 1ES 1727+502 at a statistical significance of 5.5 sigma. The integral flux above 150 GeV is estimated to be (2.1\\pm0.4)% of the Crab Nebula flux and the de-absorbed VHE spectrum has a photon index of (2.7\\pm0.5). No significant short-term variability was found in an...

  16. Insights into the emission of the blazar 1ES 1011+496 through unprecedented broadband observations during 2011 and 2012

    CERN Document Server

    Aleksić, J; Antonelli, L A; Antoranz, P; Babic, A; Bangale, P; de Almeida, U Barres; Barrio, J A; González, J Becerra; Bednarek, W; Bernardini, E; Biasuzzi, B; Biland, A; Blanch, O; Bonnefoy, S; Bonnoli, G; Borracci, F; Bretz, T; Carmona, E; Carosi, A; Colin, P; Colombo, E; Contreras, J L; Cortina, J; Covino, S; Da Vela, P; Dazzi, F; De Angelis, A; De Caneva, G; De Lotto, B; Wilhelmi, E de O na; Mendez, C Delgado; Di Pierro, F; Prester, D Dominis; Dorner, D; Doro, M; Einecke, S; Eisenacher, D; Elsaesser, D; Fernández-Barral, A; Fidalgo, D; Fonseca, M V; Font, L; Frantzen, K; Fruck, C; Galindo, D; López, R J García; Garczarczyk, M; Terrats, D Garrido; Gaug, M; Godinović, N; noz, A González Mu; Gozzini, S R; Hadasch, D; Hanabata, Y; Hayashida, M; Herrera, J; Hose, J; Hrupec, D; Idec, W; Kadenius, V; Kellermann, H; Knoetig, M L; Kodani, K; Konno, Y; Krause, J; Kubo, H; Kushida, J; La Barbera, A; Lelas, D; Lewandowska, N; Lindfors, E; Lombardi, S; Longo, F; López, M; López-Coto, R; López-Oramas, A; Lorenz, E; Lozano, I; Makariev, M; Mallot, K; Maneva, G; Mannheim, K; Maraschi, L; Marcote, B; Mariotti, M; Martínez, M; Mazin, D; Menzel, U; Miranda, J M; Mirzoyan, R; Moralejo, A; Munar-Adrover, P; Nakajima, D; Neustroev, V; Niedzwiecki, A; Rosillo, M Nievas; Nilsson, K; Nishijima, K; Noda, K; Orito, R; Overkemping, A; Paiano, S; Palatiello, M; Paneque, D; Paoletti, R; Paredes, J M; Paredes-Fortuny, X; Persic, M; Poutanen, J; Moroni, P G Prada; Prandini, E; Puljak, I; Reinthal, R; Rhode, W; Ribó, M; Rico, J; Garcia, J Rodriguez; Saito, T; Saito, K; Satalecka, K; Scalzotto, V; Scapin, V; Schultz, C; Schweizer, T; Shore, S N; Sillanpää, A; Sitarek, J; Snidaric, I; Sobczynska, D; Stamerra, A; Steinbring, T; Strzys, M; Takalo, L; Takami, H; Tavecchio, F; Temnikov, P; Terzić, T; Tescaro, D; Teshima, M; Thaele, J; Torres, D F; Toyama, T; Treves, A; Vogler, P; Will, M; Zanin, R; Buson, S; D'Ammando, F; Lähteenmäki, A; Hovatta, T; Kovalev, Y Y; Lister, M L; Max-Moerbeck, W; Mundell, C; Pushkarev, A B; Rastorgueva-Foi, E; Readhead, A C S; Richards, J L; Tammi, J; Sanchez, D A; Tornikoski, M; Savolainen, T; Steele, I

    2016-01-01

    1ES 1011+496 $(z=0.212)$ was discovered in very high energy (VHE, E >100 GeV) $\\gamma$-rays with MAGIC in 2007. The absence of simultaneous data at lower energies led to a rather incomplete characterization of the broadband spectral energy distribution (SED). We study the source properties and the emission mechanisms, probing whether a simple one-zone synchrotron-self-Compton (SSC) scenario is able to explain the observed broadband spectrum. We analyzed VHE to radio data from 2011 and 2012 collected by MAGIC, $Fermi$-LAT, $Swift$, KVA, OVRO, and Mets\\"{a}hovi in addition to optical polarimetry data and radio maps from the Liverpool Telescope and MOJAVE. The VHE spectrum was fit with a simple power law with a photon index of $3.69\\pm0.22$ and a flux above 150 GeV of $(1.46\\pm0.16)\\times10^{-11}$ ph cm$^{-2}$ s$^{-1}$. 1ES 1011+496 was found to be in a generally quiescent state at all observed wavelengths, showing only moderate variability from radio to X-rays. A low degree of polarization of less than 10\\% was...

  17. Insights into the emission of the blazar 1ES 1011+496 through unprecedented broadband observations during 2011 and 2012

    Science.gov (United States)

    Aleksić, J.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Arcaro, C.; Babic, A.; Bangale, P.; Barres de Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Bernardini, E.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Carmona, E.; Carosi, A.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Caneva, G.; De Lotto, B.; de Oña Wilhelmi, E.; Delgado Mendez, C.; Di Pierro, F.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher, D.; Elsaesser, D.; Fernández-Barral, A.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Frantzen, K.; Fruck, C.; Galindo, D.; García López, R. J.; Garczarczyk, M.; Garrido Terrats, D.; Gaug, M.; Godinović, N.; González Muñoz, A.; Gozzini, S. R.; Hadasch, D.; Hanabata, Y.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Idec, W.; Kadenius, V.; Kellermann, H.; Knoetig, M. L.; Kodani, K.; Konno, Y.; Krause, J.; Kubo, H.; Kushida, J.; La Barbera, A.; Lelas, D.; Lewandowska, N.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; López-Coto, R.; López-Oramas, A.; Lorenz, E.; Lozano, I.; Makariev, M.; Mallot, K.; Maneva, G.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Munar-Adrover, P.; Nakajima, D.; Neustroev, V.; Niedzwiecki, A.; Nievas Rosillo, M.; Nilsson, K.; Nishijima, K.; Noda, K.; Orito, R.; Overkemping, A.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Persic, M.; Poutanen, J.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Reinthal, R.; Rhode, W.; Ribó, M.; Rico, J.; Rodriguez Garcia, J.; Saito, T.; Saito, K.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schweizer, T.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Stamerra, A.; Steinbring, T.; Strzys, M.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Thaele, J.; Torres, D. F.; Toyama, T.; Treves, A.; Vogler, P.; Will, M.; Zanin, R.; Buson, S.; D'Ammando, F.; Lähteenmäki, A.; Hovatta, T.; Kovalev, Y. Y.; Lister, M. L.; Max-Moerbeck, W.; Mundell, C.; Pushkarev, A. B.; Rastorgueva-Foi, E.; Readhead, A. C. S.; Richards, J. L.; Tammi, J.; Sanchez, D. A.; Tornikoski, M.; Savolainen, T.; Steele, I.

    2016-06-01

    Context. 1ES 1011+496 (z = 0.212) was discovered in very high-energy (VHE, E> 100 GeV) γ rays with MAGIC in 2007. The absence of simultaneous data at lower energies led to an incomplete characterization of the broadband spectral energy distribution (SED). Aims: We study the source properties and the emission mechanisms, probing whether a simple one-zone synchrotron self-Compton (SSC) scenario is able to explain the observed broadband spectrum. Methods: We analyzed data in the range from VHE to radio data from 2011 and 2012 collected by MAGIC, Fermi-LAT, Swift, KVA, OVRO, and Metsähovi in addition to optical polarimetry data and radio maps from the Liverpool Telescope and MOJAVE. Results: The VHE spectrum was fit with a simple power law with a photon index of 3.69 ± 0.22 and a flux above 150 GeV of (1.46 ± 0.16) × 10-11 ph cm-2 s-1. The source 1ES 1011+496 was found to be in a generally quiescent state at all observed wavelengths, showing only moderate variability from radio to X-rays. A low degree of polarization of less than 10% was measured in optical, while some bright features polarized up to 60% were observed in the radio jet. A similar trend in the rotation of the electric vector position angle was found in optical and radio. The radio maps indicated a superluminal motion of 1.8 ± 0.4 c, which is the highest speed statistically significant measured so far in a high-frequency-peaked BL Lac. Conclusions: For the first time, the high-energy bump in the broadband SED of 1ES 1011+496 could be fully characterized from 0.1 GeV to 1 TeV, which permitted a more reliable interpretation within the one-zone SSC scenario. The polarimetry data suggest that at least part of the optical emission has its origin in some of the bright radio features, while the low polarization in optical might be due to the contribution of parts of the radio jet with different orientations of the magnetic field with respect to the optical emission.

  18. A Three-Year Multi-Wavelength Study of the Very High Energy Gamma-ray Blazar 1ES 0229+200

    CERN Document Server

    Aliu, E; Arlen, T; Aune, T; Behera, B; Beilicke, M; Benbow, W; Berger, K; Bird, R; Bouvier, A; Buckley, J H; Bugaev, V; Byrum, K; Cerruti, M; Chen, X; Ciupik, L; Connolly, M P; Cui, W; Duke, C; Dumm, J; Errando, M; Falcone, A; Federici, S; Feng, Q; Finley, J P; Fleischhack, H; Fortin, P; Fortson, L; Furniss, A; Galante, N; Gillanders, G H; Griffin, S; Griffiths, S T; Grube, J; Gyuk, G; Hanna, D; Holder, J; Hughes, G; Humensky, T B; Johnson, C A; Kaaret, P; Kertzman, M; Khassen, Y; Kieda, D; Krawczynski, H; Krennrich, F; Lang, M J; Madhavan, A S; Maier, G; Majumdar, P; McArthur, S; McCann, A; Meagher, K; Millis, J; Moriarty, P; Mukherjee, R; Nieto, D; de Bhroithe, A O'Faolain; Ong, R A; Otte, A N; Park, N; Perkins, J S; Pohl, M; Popkow, A; Prokoph, H; Quinn, J; Ragan, K; Reyes, L C; Reynolds, P T; Richards, G T; Roache, E; Sembroski, G H; Smith, A W; Staszak, D; Telezhinsky, I; Theiling, M; Varlotta, A; Vassiliev, V V; Vincent, S; Wakely, S P; Weekes, T C; Weinstein, A; Welsing, R; Williams, D A; Zajczyk, A; Zitzer, B

    2013-01-01

    The high-frequency-peaked BL Lacertae object 1ES 0229+200 is a relatively distant (z = 0.1396), hard-spectrum (Gamma ~ 2.5), very-high-energy-emitting (E > 100 GeV) gamma-ray blazar. Very-high-energy measurements of this active galactic nucleus have been used to place constraints on the intensity of the extragalactic background light and the intergalactic magnetic field. A multi-wavelength study of this object centered around very-high-energy observations by VERITAS is presented. This study obtained, over a period of three years, an 11.7 standard deviation detection and an average integral flux F(E>300 GeV) = (23.3 +- 2.8_stat +- 5.8_sys) x 10^-9 photons m^-2 s^-1, or 1.7% of the Crab Nebula's flux (assuming the Crab Nebula spectrum measured by H.E.S.S). Supporting observations from Swift and RXTE are analyzed. The Swift observations are combined with previously published Fermi observations and the very-high-energy measurements to produce an overall spectral energy distribution which is then modeled assuming ...

  19. Resolving the Extragalactic Background Light with gamma-ray spectra from distant blazars

    CERN Document Server

    Aharonian, F; Bazer-Bachi, A R; Beilicke, M; Benbow, W; Berge, D; Bernlöhr, K; Boisson, C; Bolz, O; Borrel, V; Braun, I; Breitling, F; Brown, A M; Chadwick, P M; Chounet, L M; Cornils, R; Costamante, L; Degrange, B; Dickinson, H J; Djannati-Ata, A; O'Connor-Drury, L; Dubus, G; Emmanoulopoulos, D; Espigat, P; Feinstein, F; Fontaine, G; Fuchs, Y; Funk, S; Gallant, Y A; Giebels, B; Gillessen, S; Glicenstein, J F; Goret, P; Hadjichristidis, C; Hauser, D; Hauser, M; Heinzelmann, G; Henri, G; Hermann, G; Hinton, J A; Hofmann, W; Holleran, M; Horns, D; Jacholkowska, A; De Jager, O C; Khelifi, B; Klages, S; Komin, Nu; Konopelko, A; Latham, I J; Le Gallou, R; Lemiere, A; Lemoine-Goumard, M; Leroy, N; Lohse, T; Martin, J M; Martineau--, O; Huynh; Marcowith, A; Masterson, C; McComb, T J L; De Naurois, Mathieu; Nolan, S J; Noutsos, A; Orford, K J; Osborne, J L; Ouchrif, M; Panter, M; Pelletier, G; Pita, S; Pühlhofer, G; Punch, M; Raubenheimer, B C; Raue, M; Raux, J; Rayner, S M; Reimer, A; Reimer, O; Ripken, J; Rob, L; Rolland, L; Rowell, G; Sahakian, V V; Sauge, L; Schlenker, S; Schlickeiser, R; Schuster, C; Schwanke, U; Siewert, M; Sol, H; Spangler, D; Steenkamp, R; Stegmann, C; Tavernet, J P; Terrier, R; Theoret, C G; Tluczykont, M; Van Eldik, C; Vasileiadis, G; Venter, C; Vincent, P; Völk, H J; Wagner, S J

    2006-01-01

    The diffuse Extragalactic Background Light (EBL) contains unique information about the epochs of formation and the history of evolution of galaxies. Unfortunately, direct measurements are subject to large systematic uncertainties due to the difficulties in the accurate model-based subtraction of the bright foregrounds. An alternative approach is based on the detection and identification of EBL absorption features in high-energy spectra of objects of known redshift. Here we exploit this method on the blazars H 2356-309 (z=0.165) and 1ES 1101-232 (z=0.186), newly discovered at TeV energies by the H.E.S.S. Collaboration. They are the most distant sources with measured spectra known so far at these energies. Their hard spectra provide the most stringent upper limit to date on the EBL in the Opt--NIR band, which appears significantly lower than expected from the current "direct" estimates and very close to the absolute lower limit represented by the integrated light of resolved galaxies. In addition to important c...

  20. Discovery of VHE gamma-rays from the blazar 1ES 1215+303 with the MAGIC Telescopes and simultaneous multi-wavelength observations

    CERN Document Server

    Aleksić, J; Antonelli, L A; Antoranz, P; Asensio, M; Backes, M; de Almeida, U Barres; Barrio, J A; Bastieri, D; González, J Becerra; Bednarek, W; Berger, K; Bernardini, E; Biland, A; Blanch, O; Bock, R K; Boller, A; Bonnoli, G; Tridon, D Borla; Bretz, T; Cañellas, A; Carmona, E; Carosi, A; Colin, P; Colombo, E; Contreras, J L; Cortina, J; Cossio, L; Covino, S; Da Vela, P; Dazzi, F; De Angelis, A; De Caneva, G; del Pozo, E De Cea; De Lotto, B; Mendez, C Delgado; Ortega, A Diago; Doert, M; Domínguez, A; Prester, D Dominis; Dorner, D; Doro, M; Eisenacher, D; Elsaesser, D; Ferenc, D; Fonseca, M V; Font, L; Fruck, C; López, R J García; Garczarczyk, M; Terrats, D Garrido; Giavitto, G; Godinović, N; Muñoz, A González; Gozzini, S R; Hadasch, D; Häfner, D; Herrero, A; Hildebrand, D; Hose, J; Hrupec, D; Huber, B; Jankowski, F; Jogler, T; Kadenius, V; Kellermann, H; Klepser, S; Krähenbühl, T; Krause, J; La Barbera, A; Lelas, D; Leonardo, E; Lewandowska, N; Lindfors, E; Lombardi, S; López, M; López-Coto, R; López-Oramas, A; Lorenz, E; Makariev, M; Maneva, G; Mankuzhiyil, N; Mannheim, K; Maraschi, L; Mariotti, M; Martínez, M; Mazin, D; Meucci, M; Miranda, J M; Mirzoyan, R; Moldón, J; Moralejo, A; Munar-Adrover, P; Niedzwiecki, A; Nieto, D; Nilsson, K; Nowak, N; Orito, R; Paiano, S; Paneque, D; Paoletti, R; Pardo, S; Paredes, J M; Partini, S; Perez-Torres, M A; Persic, M; Pilia, M; Pochon, J; Prada, F; Moroni, P G Prada; Prandini, E; Gimenez, I Puerto; Puljak, I; Reichardt, I; Reinthal, R; Rhode, W; Ribó, M; Rico, J; Rügamer, S; Saggion, A; Saito, K; Saito, T Y; Salvati, M; Satalecka, K; Scalzotto, V; Scapin, V; Schultz, C; Schweizer, T; Shore, S N; Sillanpää, A; Sitarek, J; Snidaric, I; Sobczynska, D; Spanier, F; Spiro, S; Stamatescu, V; Stamerra, A; Steinke, B; Storz, J; Strah, N; Sun, S; Surić, T; Takalo, L; Takami, H; Tavecchio, F; Temnikov, P; Terzić, T; Tescaro, D; Teshima, M; Tibolla, O; Torres, D F; Treves, A; Uellenbeck, M; Vogler, P; Wagner, R M; Weitzel, Q; Zabalza, V; Zandanel, F; Zanin, R; Berdyugin, A; Buson, S; Järvelä, E; Larsson, S; Lähteenmäki, A; Tammi, J; de Lausanne, now at: Ecole polytechnique fédérale; Lausanne,; Switzerland,; Padova, supported by INFN; Energéticas, now at: Centro de Investigaciones; Tecnológicas, Medioambientales y; Madrid,; Spain,; KIPAC, now at:; Laboratory, SLAC National Accelerator; USA,; ESO, now at: Finnish Centre for Astronomy with; Turku, University of; Finland,; Observatory, Aalto University Metsähovi Radio; Metsähovintie,; Finland,; Physics, Department of; University, Stockholm; Stockholm,; Sweden,; Physics, The Oskar Klein Centre for Cosmoparticle; Stockholm,; Sweden,; Astronomy, Department of; University, Stockholm; Stockholm,; Sweden),

    2012-01-01

    Context. We present the discovery of very high energy (VHE, E > 100GeV) gamma-ray emission from the BL Lac object 1ES 1215+303 by the MAGIC telescopes and simultaneous multi-wavelength data in a broad energy range from radio to gamma-rays. Aims. We study the VHE gamma-ray emission from 1ES 1215+303 and its relation to the emissions in other wavelengths. Methods. Triggered by an optical outburst, MAGIC observed the source in January-February 2011 for 20.3 hrs. The target was monitored in the optical R-band by the KVA telescope that also performed optical polarization measurements. We triggered target of opportunity observations with the Swift satellite and obtained simultaneous and quasi-simultaneous data from the Fermi Large Area Telescope and from the Mets\\"ahovi radio telescope. We also present the analysis of older MAGIC data taken in 2010. Results. The MAGIC observations of 1ES 1215+303 carried out in January-February 2011 resulted in the first detection of the source at VHE with a statistical significanc...

  1. Search for TeV $\\gamma$--ray emission from blazar 1ES1218+304 with TACTIC telescope during March-April 2013

    CERN Document Server

    Singh, K K; Tickoo, A K; Rannot, R C; Chandra, P; Agarwal, N K; Gaur, K K; Goyal, A; Goyal, H C; Kumar, N; Marandi, P; Kothari, M; Bhatt, H; Chanchalani, K; Chouhan, N; Dhar, V K; Ghosal, B; Kaul, S R; Koul, M K; Koul, R; Venugopal, K; Bhat, C K; Borwankar, C; Bhagwan, J; Gupta, A C

    2014-01-01

    In this paper, we present results of TeV $\\gamma$--ray observations of the high synchrotron peaked BL Lac object 1ES 1218+304 (z=0.182) with the $TACTIC$ (TeV Atmospheric Cherenkov Telescope with Imaging Camera). The observations are primarily motivated by the unusually hard GeV-TeV spectrum of the source despite its relatively large redshift. The source is observed in the TeV energy range with the $TACTIC$ from March 1, 2013 to April 15, 2013 (MJD 56352--56397) for a total observation time of 39.62 h and no evidence of TeV $\\gamma$--ray activity is found from the source. The corresponding 99$\\%$ confidence level upper limit on the integral flux above a threshold energy of 1.1 TeV is estimated to be 3.41 $\\times10^{-12}$ photons cm$^{-2}$ s$^{-1}$ (i.e $<23\\%$ Crab Nebula flux) assuming a power law differential energy spectrum with photon index 3.0, as previously observed by the $MAGIC$ and $VERITAS$ telescopes. For the study of multi-wavelength emission from the source, we use nearly simultaneous optical,...

  2. Observation of the BL Lac objects 1ES 1215+303 and 1ES 1218+304 with the MAGIC telescopes

    OpenAIRE

    Colin, Pierre; Gonzalez, Josefa Becerra; Lindfors, Elina; Lombardi, Saverio; Sitarek, Julian; Stamera, Antonio; collaboration, for the MAGIC

    2011-01-01

    The two BL Lac objects 1ES 1215+303 and 1ES 1218+304, separated by 0.8 deg, were observed with the MAGIC telescopes in 2010 and 2011. The 20 hours of data registered in January 2011 resulted in the first detection at Very High Energy (>100 GeV) of 1ES 1215+303 (also known as ON-325). This observation was triggered by a high optical state of the source reported by the Tuorla blazar monitoring program. Comparison with the 25 hours of data carried out from January to May 2010 suggests that 1ES 1...

  3. Hadronic Modeling of Blazars

    Directory of Open Access Journals (Sweden)

    Weidinger Matthias

    2013-12-01

    Full Text Available The ongoing systematic search for sources of extragalactic gamma rays has now revealed many blazars in which the very high energy output can not consistently be described as synchrotron self-Compton radiation. In this paper a self consistent hybrid model is described, explaining the very high energy radiation of those blazars as proton synchrotron radiation accompanied by photo-hadronic cascades. As the model includes all relevant radiative processes it naturally includes the synchrotron self-Compton case as well, depending on the chosen parameters. This paper focuses on rather high magnetic fields to be present within the jet, hence the hadronically dominated case. To discriminate the hadronic scenario against external photon fields being upscattered within the jet to produce the dominating gamma-ray output, the temporal behavior of blazars may be exploited with the presented model. Variability reveals both, the highly non-linear nature caused by the photohadronic cascades and typical timescales as well as fingerprints in the inter-band lightcurves of the involved hadrons. The modeling of two individual sources is shown : 1 ES 1011+496, a high frequency peaked blazar at redshift z = 0.212, which is well described within the hybrid scenario using physically reasonable parameters. The short term variability of the second example, namely 3C 454.3, a Flat Spectrum Radio Quasar at z = 0.859, reveals the limitations of the gamma-rays being highly dominated by proton synchrotron radiation.

  4. Discovery of Very High Energy Gamma Rays from 1ES 1440+122

    OpenAIRE

    VERITAS Collaboration; Archambault, S.; Archer, A.; Barnacka, A.; Behera, B.; Beilicke, M.; Benbow, W.; Berger, K; Bird, R.; Boettcher, M.; J. H. Buckley(Department of Physics, Washington University, St. Louis, USA); Bugaev, V.; Cardenzana, J. V; M. Cerruti(Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645, USA); Chen, X.

    2016-01-01

    The BL Lacertae object 1ES 1440+122 was observed in the energy range from 85 GeV to 30 TeV by the VERITAS array of imaging atmospheric Cherenkov telescopes. The observations, taken between 2008 May and 2010 June and totalling 53 hours, resulted in the discovery of $\\gamma$-ray emission from the blazar, which has a redshift $z$=0.163. 1ES 1440+122 is detected at a statistical significance of 5.5 standard deviations above the background with an integral flux of (2.8$\\pm0.7_{\\mathrm{stat}}\\pm0.8...

  5. Monitoring of bright blazars with MAGIC telescope

    OpenAIRE

    Hsu, C. C.; Satalecka, K.; Thom, M; Backes, M.; Bernardini, E.; Bonnoli, G.; Galante, N.; Goebel, F; Lindfors, E.; Majumdar, P.; Stamerra, A.; Wagner, R. M.

    2009-01-01

    Blazars, a class of Active Galactic Nuclei (AGN) characterized by a close orientation of their relativistic outflows (jets) towards the line of sight, are a well established extragalactic TeV $\\gamma$-ray emitters. Since 2006, three nearby and TeV bright blazars, Markarian (Mrk) 421, Mrk 501 and 1ES 1959+650, are regularly observed by the MAGIC telescope with single exposures of 30 to 60 minutes. The sensitivity of MAGIC allows to establish a flux level of 30% of the Crab flux for each such o...

  6. High Energy Neutrinos from Recent Blazar Flares

    CERN Document Server

    Halzen, Francis

    2016-01-01

    The energy density of cosmic neutrinos measured by IceCube matches the one observed by Fermi in extragalactic photons that predominantly originate in blazars. This has inspired attempts to match Fermi sources with IceCube neutrinos. A spatial association combined with a coincidence in time with a flaring source may represent a smoking gun for the origin of the IceCube flux. In June 2015, the Fermi Large Area Telescope observed an intense flare from blazar 3C 279 that exceeded the steady flux of the source by a factor of forty for the duration of a day. We show that IceCube is likely to observe neutrinos, if indeed hadronic in origin, in data that are still blinded at this time. We also discuss other opportunities for coincident observations that include a recent flare from blazar 1ES 1959+650 that previously produced an intriguing coincidence with AMANDA observations.

  7. Blazar Monitoring List

    Data.gov (United States)

    National Aeronautics and Space Administration — This is a compilation of sources in major blazar monitoring programs. This list contains all blazars known to be regularly monitored, plus all the MOJAVE- &...

  8. Hadronic-Origin orphan TeV flare from the 1ES 1959+650

    CERN Document Server

    Sahu, Sarira; Sanabria, Juan Carlos

    2013-01-01

    The 1ES 1959+650 is a high-peaked BL Lacertae object. On 4th of June, 2002, it exhibited a strong TeV flare without any low energy counterpart, providing for the first time an example of an orphan flare from a blazar. Observation of this orphan flare is in striking disagreement with the predictions of the leptonic models thus challenging the conventional synchrotron self-Compton (SSC) interpretation of the TeV emission. Here we propose that, the low energy tail of the SSC photons in the blazar jet serve as the target for the Fermi-accelerated high energy protons of energy . 100 TeV, within the jet to produce the TeV photons through the decay of neutral pions from the delta resonance. Our model explains very nicely the observed TeV flux from this orphan flare and we also estimate the high energy neutrino flux from this flaring event.

  9. Monitoreo de blazares con el Telescopio Whipple de rayos gamma

    Science.gov (United States)

    Pichel, A.; Rovero, A. C.

    Since September 2005, the Whipple 10 m Gamma-ray Telescope has been used primarily to monitor known TeV blazars. The five blazars that have been previously detected at Whipple: Markarian 421, H1426+428, Markarian 501, 1ES 1959+650 and 1ES 2344+514, are monitored each night that they are visible. Alerts are sent to VERITAS any time these objects are flaring to trigger ToO observations. The light curves for these blazars are produced and combined with observations in radio, optical and X-ray in the frame of Multiwavelengths Campaigns. We present here the results for the 2005-08 observations on Mrk421. FULL TEXT IN SPANISH

  10. Blazar Sequence in Fermi Era

    Indian Academy of Sciences (India)

    Liang Chen

    2014-09-01

    In this paper, we review the latest research results on the topic of blazar sequence. It seems that the blazar sequence is phenomenally ruled out, while the theoretical blazar sequence still holds. We point out that black hole mass is a dominated parameter accounting for high-power-high-synchrotron-peaked and low-power-low-sychrotron-peaked blazars. Because most blazars have similar size of emission region, theoretical blazar sequence implies that the break of Spectral Energy Distribution (SED) is a cooling break in nature.

  11. High redshift blazars

    CERN Document Server

    Ghisellini, G

    2013-01-01

    Blazars are sources whose jet is pointing to us. Since their jets are relativistic, the flux is greatly amplified in the direction of motion, making blazars the most powerful persistent objects in the Universe. This is true at all frequencies, but especially where their spectrum peaks. Although the spectrum of moderate powerful sources peaks in the ~GeV range, extremely powerful sources at high redshifts peak in the ~MeV band. This implies that the hard X-ray band is the optimal one to find powerful blazars beyond a redshift of ~4. First indications strongly suggest that powerful high-z blazars harbor the most massive and active early black holes, exceeding a billion solar masses. Since for each detected blazars there must exist hundreds of similar, but misaligned, sources, the search for high-z blazars is becoming competitive with the search of early massive black holes using radio-quiet quasars. Finding how the two populations of black holes (one in jetted sources, the other in radio-quiet objects) evolve i...

  12. Tev Blazars: Status of Observations

    OpenAIRE

    Krennrich, F.; Biller, S. D.; Bond, I. H.; Boyle, P. J.; Bradbury, S. M.; Breslin, A. C.; J. H. Buckley(Department of Physics, Washington University, St. Louis, USA); Burdett, A. M.; Bussons-Gordo, J.; Carter-Lewis, D. A.; Catanese, M.; Cawley, M. F.; Fegan, D. J.; Finley, J. P.; Gaidos, J. A.

    1998-01-01

    The close relation between ground-based TeV observations and satellite borne $\\gamma$-ray measurements has been important for the understanding of blazars. The observations which involve the TeV component in blazar studies are reviewed.

  13. 1ES 0033+595 found in a very high state by INTEGRAL

    DEFF Research Database (Denmark)

    Bassani, L.; Malizia, A.; Chenevez, Jérôme;

    2014-01-01

    ; the source has recently been reported as one of the 50 or so blazars detected at TeV energies (Aleksic et al. 2014, http://arxiv.org/abs/1410.7059v1 ). 1ES 0033+595 was found in the combined JMX1+2 mosaic (effective exposure of 3.1 ksec, 3-10 keV band) with a flux of 20 +/-2 mCrab (3.4 x 10^-10 erg/cm2/s......) corresponding to a 10 sigma significance. It is also detected at higher energies ((in JEM-X2 only), with a flux of 21 +/-5 mCrab (or 2.5 x 10^-10 erg/cm2/s) at 4 sigma level (effective exposure of 1.2 ksec, 10-25 keV band). At even higher energies, IBIS/ISGRI found 1ES 0033+595Â at a flux level of 13.6+/-2 m......Crab (10^-10 erg/cm2/s) in the 18-40 keV band (13 sec, about 7 sigma) while a 3 sigma upper limit of 11 mCrab (10^-10 erg/cm2/s) is provided in the 40-100 keV band. Using data collected from the ASDC SED Builder tool (http://tools.asdc.asi.it/SED/) we notice that this is the highest X-ray flux so far...

  14. Discovery of very high energy gamma rays from 1ES 1440+122

    Science.gov (United States)

    Archambault, S.; Archer, A.; Barnacka, A.; Behera, B.; Beilicke, M.; Benbow, W.; Berger, K.; Bird, R.; Böttcher, M.; Buckley, J. H.; Bugaev, V.; Cardenzana, J. V.; Cerruti, M.; Chen, X.; Christiansen, J. L.; Ciupik, L.; Collins-Hughes, E.; Connolly, M. P.; Cui, W.; Dickinson, H. J.; Dumm, J.; Eisch, J. D.; Errando, M.; Falcone, A.; Federici, S.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Fortson, L.; Furniss, A.; Gillanders, G. H.; Godambe, S.; Griffin, S.; Griffiths, S. T.; Grube, J.; Gyuk, G.; Håkansson, N.; Hanna, D.; Holder, J.; Hughes, G.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kertzman, M.; Khassen, Y.; Kieda, D.; Krawczynski, H.; Kumar, S.; Lang, M. J.; Madhavan, A. S.; Maier, G.; McArthur, S.; McCann, A.; Meagher, K.; Millis, J.; Moriarty, P.; Nelson, T.; Nieto, D.; de Bhróithe, A. O'Faoláin; Ong, R. A.; Otte, A. N.; Park, N.; Perkins, J. S.; Pohl, M.; Popkow, A.; Prokoph, H.; Pueschel, E.; Quinn, J.; Ragan, K.; Rajotte, J.; Reyes, L. C.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Sembroski, G. H.; Shahinyan, K.; Smith, A. W.; Staszak, D.; Sweeney, K.; Telezhinsky, I.; Tucci, J. V.; Tyler, J.; Varlotta, A.; Vassiliev, V. V.; Wakely, S. P.; Welsing, R.; Wilhelm, A.; Williams, D. A.; Zitzer, B.

    2016-09-01

    The BL Lacertae object 1ES 1440+122 was observed in the energy range from 85 GeV to 30 TeV by the VERITAS array of imaging atmospheric Cherenkov telescopes. The observations, taken between 2008 May and 2010 June and totalling 53 h, resulted in the discovery of γ-ray emission from the blazar, which has a redshift z = 0.163. 1ES 1440+122 is detected at a statistical significance of 5.5 standard deviations above the background with an integral flux of (2.8 ± 0.7stat ± 0.8sys) × 10-12 cm-2 s-1 (1.2 per cent of the Crab Nebula's flux) above 200 GeV. The measured spectrum is described well by a power law from 0.2 to 1.3 TeV with a photon index of 3.1 ± 0.4stat ± 0.2sys. Quasi-simultaneous multiwavelength data from the Fermi Large Area Telescope (0.3-300 GeV) and the Swift X-ray Telescope (0.2-10 keV) are additionally used to model the properties of the emission region. A synchrotron self-Compton model produces a good representation of the multiwavelength data. Adding an external-Compton or a hadronic component also adequately describes the data.

  15. VERITAS and Multiwavelength Observations of the BL Lacertae Object 1ES 1741+196

    CERN Document Server

    Abeysekara, A U; Archer, A; Benbow, W; Bird, R; Biteau, J; Buchovecky, M; Buckley, J H; Bugaev, V; Byrum, K; Cardenzana, J V; Cerruti, M; Chen, X; Christiansen, J L; Ciupik, L; Connolly, M P; Cui, W; Dickinson, H J; Dumm, J; Eisch, J D; Errando, M; Falcone, A; Feng, Q; Finley, J P; Fleischhack, H; Flinders, A; Fortin, P; Fortson, L; Furniss, A; Gillanders, G H; Griffin, S; Grube, J; Gyuk, G; Hütten, M; Hanna, D; Holder, J; Humensky, T B; Johnson, C A; Kaaret, P; Kar, P; Kelley-Hoskins, N; Kertzman, M; Kieda, D; Krause, M; Krennrich, F; Kumar, S; Lang, M J; Maier, G; McArthur, S; McCann, A; Meagher, K; Moriarty, P; Mukherjee, R; Nieto, D; O'Brien, S; de Bhróithe, A O'Faoláin; Ong, R A; Otte, A N; Park, N; Pelassa, V; Petrashyk, A; Pohl, M; Popkow, A; Pueschel, E; Quinn, J; Ragan, K; Ratliff, G; Reyes, L C; Reynolds, P T; Richards, G T; Roache, E; Rulten, C; Santander, M; Sembroski, G H; Shahinyan, K; Smith, A W; Staszak, D; Telezhinsky, I; Tucci, J V; Tyler, J; Vincent, S; Wakely, S P; Weiner, O M; Weinstein, A; Wilhelm, A; Williams, D A; Zitzer, B

    2016-01-01

    We present results from multiwavelength observations of the BL Lacertae object 1ES 1741+196, including results in the very-high-energy $\\gamma$-ray regime using the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The VERITAS time-averaged spectrum, measured above 180 GeV, is well-modelled by a power law with a spectral index of $2.7\\pm0.7_{\\mathrm{stat}}\\pm0.2_{\\mathrm{syst}}$. The integral flux above 180 GeV is $(3.9\\pm0.8_{\\mathrm{stat}}\\pm1.0_{\\mathrm{syst}})\\times 10^{-8}$ m$^{-2}$ s$^{-1}$, corresponding to 1.6% of the Crab Nebula flux on average. The multiwavelength spectral energy distribution of the source suggests that 1ES 1741+196 is an extreme-high-frequency-peaked BL Lacertae object. The observations analysed in this paper extend over a period of six years, during which time no strong flares were observed in any band. This analysis is therefore one of the few characterizations of a blazar in a non-flaring state.

  16. Discovery of Very High Energy Gamma Rays from 1ES 1440+122

    CERN Document Server

    Archambault, S; Barnacka, A; Behera, B; Beilicke, M; Benbow, W; Berger, K; Bird, R; Boettcher, M; Buckley, J H; Bugaev, V; Cardenzana, J V; Cerruti, M; Chen, X; Christiansen, J L; Ciupik, L; Collins-Hughes, E; Connolly, M P; Cui, W; Dickinson, H J; Dumm, J; Eisch, J D; Errando, M; Falcone, A; Federici, S; Feng, Q; Finley, J P; Fleischhack, H; Fortson, L; Furniss, A; Gillanders, G H; Godambe, S; Griffin, S; Griffiths, S T; Grube, J; Gyuk, G; Haakansson, N; Hanna, D; Holder, J; Hughes, G; Johnson, C A; Kaaret, P; Kar, P; Kertzman, M; Khassen, Y; Kieda, D; Krawczynski, H; Kumar, S; Lang, M J; Madhavan, A S; Maier, G; McArthur, S; McCann, A; Meagher, K; Millis, J; Moriarty, P; Nelson, T; Nieto, D; de Bhroithe, A O'Faolain; Ong, R A; Otte, A N; Park, N; Perkins, J S; Pohl, M; Popkow, A; Prokoph, H; Pueschel, E; Quinn, J; Ragan, K; Rajotte, J; Reyes, L C; Reynolds, P T; Richards, G T; Roache, E; Sembroski, G H; Shahinyan, K; Smith, A W; Staszak, D; Sweeney, K; Telezhinsky, I; Tucci, J V; Tyler, J; Varlotta, A; Vassiliev, V V; Wakely, S P; Welsing, R; Wilhelm, A; Williams, D A; Zitzer, B

    2016-01-01

    The BL Lacertae object 1ES 1440+122 was observed in the energy range from 85 GeV to 30 TeV by the VERITAS array of imaging atmospheric Cherenkov telescopes. The observations, taken between 2008 May and 2010 June and totalling 53 hours, resulted in the discovery of $\\gamma$-ray emission from the blazar, which has a redshift $z$=0.163. 1ES 1440+122 is detected at a statistical significance of 5.5 standard deviations above the background with an integral flux of (2.8$\\pm0.7_{\\mathrm{stat}}\\pm0.8_{\\mathrm{sys}}$) $\\times$ 10$^{-12}$ cm$^{-2}$ s$^{-1}$ (1.2\\% of the Crab Nebula's flux) above 200 GeV. The measured spectrum is described well by a power law from 0.2 TeV to 1.3 TeV with a photon index of 3.1 $\\pm$ 0.4$_{\\mathrm{stat}}$ $\\pm$ 0.2$_{\\mathrm{sys}}$. Quasi-simultaneous multi-wavelength data from the Fermi Large Area Telescope (0.3--300 GeV) and the Swift X-ray Telescope (0.2--10 keV) are additionally used to model the properties of the emission region. A synchrotron self-Compton model produces a good repr...

  17. Core Dominance Parameter for -Ray Loud Blazars

    Indian Academy of Sciences (India)

    S. H. Li; J. H. Fan; D. X. Wu

    2014-09-01

    In this paper, we compiled 572 blazars that have known core dominance parameter (log ), out of which 121 blazars are -ray loud blazars. We compared log between 121 blazars and the rest with non -ray detections, and found that -ray loud blazars showed a different distribution, and their average value of log is greater than that for non -ray blazars. Our analysis suggests that the -ray emissions are strongly beamed.

  18. Synchrotron pair halo and echo emission from blazars in the cosmic web: application to extreme TeV blazars

    CERN Document Server

    Oikonomou, Foteini; Kotera, Kumiko

    2014-01-01

    High frequency peaked high redshift blazars, are extreme in the sense that their spectrum is particularly hard and peaks at TeV energies. Standard leptonic scenarios require peculiar source parameters and/or a special setup in order to account for these observations. Electromagnetic cascades seeded by ultra-high energy cosmic rays (UHECR) in the intergalactic medium have also been invoked, assuming a very low intergalactic magnetic field (IGMF). Here we study the synchrotron emission of UHECR secondaries produced in blazars located in magnetised environments, and show that it can provide an alternative explanation to these challenged channels, for sources embedded in structured regions with magnetic field strengths of the order of $10^{-7}$ G. To demonstrate this, we focus on three extreme blazars: 1ES 0229+200, RGB J0710+591, and 1ES 1218+304. We model the expected gamma-ray signal from these sources through a combination of numerical Monte Carlo simulations and solving the kinetic equations of the particles...

  19. The Proton Blazar

    OpenAIRE

    Mannheim, Karl

    1993-01-01

    Considering shock-accelerated protons in addition to electrons in a synchrotron radio jet naturally produces the observed X- through gamma ray continuum emission of flat-spectrum radio-loud AGN, whereas the corresponding shock-accelerated electrons produce the infrared through optical continuum. All of these emission components are rapidly variable on short time scales which can be accounted for by a common origin of the blazar emission in a relativistic sub-parsec scale jet. Moreover, neutri...

  20. Variability of Blazars

    Indian Academy of Sciences (India)

    J. H. Fan; Y. Liu; Y. Li; Q. F. Zhang; J. Tao; O. Kurtanidze

    2011-03-01

    Variability is one of the characteristics of blazars. The rapid variability is superposed on the long term variation. In this work, the variability on different time scales, such as intra-day (IDV), short-term (STV) and long-term (LTV) variations are presented for some sources. We also presented our own observations of some selected objects, for which the historical data were compiled for periodicity analysis using several methods. The parameters of the binary black hole system OJ 287 are determined.

  1. Chasing extreme blazars with INTEGRAL

    CERN Document Server

    Bassani, Loredana; Landi, R; Malizia, A; Bird, A J; Bazzano, A; Ubertini, P

    2013-01-01

    Within the blazar population, hard X-ray selected objects are of particular interest as they tend to lie at each end of the blazar sequence. In particular, flat spectrum radio quasars located at high redshifts display the most powerful jets, the largest black hole masses and the most luminous accretion disks: their spectral energy distribution has a Compton peak in the sub-MeV region which favours their detection by instruments like INTEGRAL/IBIS and Swift/BAT. These sources are even more extreme than blazars selected in other wavebands, like, for example, the gamma-ray range explored by Fermi. Here we report on a sample of 12 high redshift blazars detected so far by INTEGRAL, including 3 newly identified objects. Some properties of the combined IBIS/BAT sample of high redshift blazars (z>2) are also compared to those of a similar similar sample obtained by Fermi.

  2. The nature of transition blazars

    Energy Technology Data Exchange (ETDEWEB)

    Ruan, J. J.; Anderson, S. F. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Plotkin, R. M. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Brandt, W. N.; Schneider, D. P. [Department of Astronomy and Astrophysics, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802 (United States); Burnett, T. H. [Department of Physics, University of Washington, Seattle, WA 98195-1560 (United States); Myers, A. D., E-mail: jruan@astro.washington.edu [Department of Physics and Astronomy 3905, University of Wyoming, 1000 East University, Laramie, WY 82071 (United States)

    2014-12-10

    Blazars are classically divided into the BL Lacertae (BLL) and flat-spectrum radio quasar (FSRQ) subclasses, corresponding to radiatively inefficient and efficient accretion regimes, respectively, largely based on the equivalent width (EW) of their optical broad emission lines (BELs). However, EW-based classification criteria are not physically motivated, and a few blazars have previously transitioned' from one subclass to the other. We present the first systematic search for these transition blazars in a sample of 602 unique pairs of repeat spectra of 354 blazars in the Sloan Digital Sky Survey, finding six clear cases. These transition blazars have bolometric Eddington ratios of ∼0.3 and low-frequency synchrotron peaks, and are thus FSRQ-like. We show that the strong EW variability (up to an unprecedented factor of >60) is due to swamping of the BELs from variability in jet continuum emission, which is stronger in amplitude and shorter in timescale than typical blazars. Although these transition blazars appear to switch between FSRQ and BLL according to the phenomenologically based EW scheme, we show that they are most likely rare cases of FSRQs with radiatively efficient accretion flows and especially strongly beamed jets. These results have implications for the decrease of the apparent BLL population at high redshifts, and may lend credence to claims of a negative BLL redshift evolution.

  3. Gamma Rays From Blazars

    CERN Document Server

    Tavecchio, F

    2016-01-01

    Blazars are high-energy engines providing us natural laboratories to study particle acceleration, relativistic plasma processes, magnetic field dynamics, black hole physics. Key informations are provided by observations at high-energy (in particular by Fermi/LAT) and very-high energy (by Cherenkov telescopes). I give a short account of the current status of the field, with particular emphasis on the theoretical challenges connected to the observed ultra-fast variability events and to the emission of flat spectrum radio quasars in the very high energy band.

  4. AGN Winds and Blazar Phenomenology

    Science.gov (United States)

    Kazanas, Demos

    2012-01-01

    The launch of {\\em Fermi} produced a significant number of AGN detections to allow statistical treatment of their properties. One of the first such systematics was the "Blazar Divide" in FSRQs and BL Lacs according to their gamma-ray spectral index and luminosity. Further data accumulation indicated this separation to be less clear than thought before. An MHD wind model which can model successfully the Seyfert X-ray absorber properties provides the vestiges of an account of the observed blazar classification. We propose to employ this model to model in detail the broad band blazar spectra and their statistical properties in terms of the physical parameters of these MHD winds.

  5. Mrk 421, Mrk 501, and 1ES 1426+428 at 100 GeV with the CELESTE Cherenkov Telescope

    CERN Document Server

    Smith, D A; Britto, R; Bruel, P; Gordo, J B; Dumora, D; Durand, E; Eschstruth, P; Espigat, P; Holder, J; Jacholkowska, A; Lavalle, J; Le Gallou, R; Lott, B; Manseri, H; Munz, F; Nuss, E; Piron, Frédéric; Reposeur, T; Sako, T

    2006-01-01

    We have measured the gamma-ray fluxes of the blazars Mrk 421 and Mrk 501 in the energy range between 50 and 350 GeV (1.2 to 8.3 x 10^25 Hz). The detector, called CELESTE, used first 40, then 53 heliostats of the former solar facility "Themis" in the French Pyrenees to collect Cherenkov light generated in atmospheric particle cascades. The signal from Mrk 421 is often strong. We compare its flux with previously published multi-wavelength studies and infer that we are straddling the high energy peak of the spectral energy distribution. The signal from Mrk 501 in 2000 was weak (3.4 sigma). We obtain an upper limit on the flux from 1ES 1426+428 of less than half that of the Crab flux near 100 GeV. The data analysis and understanding of systematic biases have improved compared to previous work, increasing the detector's sensitivity.

  6. STACEE Observations of 1ES 1218+304

    CERN Document Server

    Mukherjee, R; Ball, J; Carson, J E; Covault, C E; Driscoll, D D; Fortin, P; Gingrich, D M; Hanna, D S; Jarvis, A; Kildea, J; Lindner, T; Müller, C; Ong, R A; Ragan, K; Williams, D A; Zweerink, J

    2007-01-01

    We present the analysis and results of recent high-energy gamma-ray observations of the high energy-peaked BL Lac (HBL) object 1ES 1218+304 with the Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE). 1ES 1218+304 is an X-ray bright HBL at a redshift z=0.182. It has been predicted to be a gamma-ray emitter above 100 GeV, detectable by ground-based Cherenkov telescopes. Recently this source has been detected by MAGIC and VERITAS, confirming these predictions. STACEE's sensitivity to astrophysical sources at energies above 100 GeV allows it to explore high energy sources such as X-ray bright active galaxies and gamma-ray bursts. We present results from STACEE observations of 1ES 1218+304 in the 2006 and 2007 observing seasons.

  7. Blazar jets the spectra

    CERN Document Server

    Ghisellini, G

    2000-01-01

    The radiation observed by blazars is believed to originate from the transformation of bulk kinetic energy of relativistic jets into random energy. A simple way to achieve this is to have an intermittent central power source, producing shells of plasma with different bulk Lorentz factors. These shells will collide at some distance from the center, producing shocks and then radiation. This scenario, called internal shock model, is thought to be at the origin of the gamma-rays observed in gamma-ray bursts and can work even better in blazars. It accounts for the observed key characteristics of these objects, including the fact that radiation must be preferentially produced at a few hundreds of Schwarzschild radii from the center, but continues to be produced all along the jet. At the kpc scale and beyond, the slowly moving parts of a (straight) jet can be illuminated by the beamed radiation of the core, while the fast parts of the jet will see enhanced cosmic microwave radiation. In both cases the Inverse Compton...

  8. AGILE and blazar studies

    CERN Document Server

    Marisaldi, M; Vercellone, S; Donnarumma, I; Bulgarelli, A; Chen, A W; Giuliani, A; Longo, F; Pacciani, L; Pucella, G; Tavani, M; Vittorini, V

    2009-01-01

    During the first two years of observation, AGILE detected several blazars at high significance: 3C 279, 3C 454.3, PKS 1510-089, S5 0716+714, 3C 273, W Comae, Mrk 421 and PKS 0537-441. We obtained long-term coverage of 3C 454.3, for a total of more than three months at energies above 100 MeV. 3C 273 was the first blazar detected simultaneously by the AGILE gamma-ray detector and by its hard X-ray monitor. S5 0716+714, an intermediate BL Lac object, exhibited a very fast and intense gamma-ray transient during an optical high-state phase, challenging the current theoretical models for energy extraction from a rotating black hole, while W Comae and Mkn 421 were detected during an AGILE Target of Opportunity (ToO) repointing, and were simultaneously detected by Cherenkov telescopes. Thanks to the rapid dissemination of our alerts, we were able to obtain multi-wavelength ToO data from other observatories such as Spitzer, Swift, RXTE, Suzaku, INTEGRAL, MAGIC, VERITAS, as well as radio-to-optical coverage by means of...

  9. Chandra view of the warm-hot intergalactic medium toward 1ES 1553+113: Absorption-line detections and identifications. I

    OpenAIRE

    F. Nicastro; Barcons, Xavier; Paerels, F. B. S.

    2013-01-01

    We present the first results from our pilot 500 ks Chandra Low Energy Transmission Grating Large Program observation of the soft X-ray brightest source in the z ≳ 0.4 sky, the blazar 1ES 1553+113, aimed to secure the first uncontroversial detections of the missing baryons in the X-rays. We identify a total of 11 possible absorption lines, with single-line statistical significances between 2.2σ and 4.1σ. Six of these lines are detected at high single-line statistical significance (3.6 ≤ σ ≤ 4....

  10. Quasi Periodic Oscillations in Blazars

    Indian Academy of Sciences (India)

    Alok C. Gupta

    2014-09-01

    Here we report our recent discoveries of Quasi-Periodic Oscillations (QPOs) in blazars time series data in X-ray and optical electromagnetic bands. Any such detection can give important clues of the location and nature of the processes of emission mechanism. In the case of radio-quiet AGN, the detected QPOs are very likely to be associated with the accretion disk. But in the case of blazars, it may be associated with jets in the high and outburst states, and in the low-state, it is probably associated with the accretion disk. In this brief review, I summarize the recent QPO detections in blazars. There is one strong evidence of QPO detection in XMM–Newton time series data of narrow line Seyfert 1 galaxy RE J1034+396 about which we will also discuss briefly.

  11. Blazars at Low Radio Frequencies

    Science.gov (United States)

    Trüstedt, J.; Kadler, M.; Brüggen, M.; Falcke, H.; Heald, G.; McKean, J.; Mueller, C.; Ros, E.; Schulz, R.; Wilms, J.

    We explore the low radio-frequency properties of the MOJAVE 1 blazar sample using the LOFAR Multi-Frequency Snapshot Sky Survey (MSSS). We find the characteristically flat blazar spectrum to extend down to the LOFAR bands, demonstrating that the emission at these low radio frequencies is still dominated by relativistically beamed emission. As most sources remain unresolved at the MSSS angular resolution, we are reimaging these data using LOFAR baselines beyond the standard MSSS uv-range resulting in an angular resolution of ~24 arcsec. We present first LOFAR images of MOJAVE sources from this project.

  12. Intergalactic Magnetic Fields and Gamma Ray Observations of Extreme TeV Blazars

    CERN Document Server

    Arlen, Timothy C; Weisgarber, Thomas; Wakely, Scott P; Shafi, S Yusef

    2012-01-01

    The intergalactic magnetic field (IGMF) can be indirectly probed through its effect on electromagnetic cascades initiated by a source of TeV gamma-rays, such as active galactic nuclei (AGN). AGN that are sufficiently luminous at TeV energies, extreme TeV blazars, can produce detectable levels of secondary radiation from Inverse Compton (IC) scattering of the electrons in the cascade, provided that the IGMF is not too large. We review recent work in the literature which utilizes this idea to derive constraints on the IGMF for three TeV-detected blazars-1ES 0229+200, 1ES 1218+304, and RGB J0710+591, and we also investigate four other hard-spectrum TeV blazars in the same context. Through a recently developed detailed Monte Carlo code, incorporating all major effects of QED and cosmological expansion, we research effects of major uncertainties such as the spectral properties of the source, uncertainty in the UV - far IR extragalactic background light (EBL), undersampled Very High Energy (VHE; energy > 100 GeV) c...

  13. Debeamed Sequence of LBAS Blazars

    Indian Academy of Sciences (India)

    Bangrong Huang; Xiong Zhang; Dingrong Xiong; Haojin Zhang

    2014-09-01

    We have collected a sample of 71 -ray blazars selected from the Fermi LAT Bright AGN Sample (LBAS). The correlation between synchrotron peak luminosities p and synchrotron peak frequencies p have been studied and there is a weak negative correlation. But after correcting the effect of redshift and Doppler boosting, the relation between intrinsic 'p and 'p show significant positive correlation.

  14. Bethe-Heitler cascades as a plausible origin of hard spectra in distant TeV blazars

    CERN Document Server

    Zheng, Y G; Kang, S J

    2016-01-01

    Context. Very high-energy (VHE) $\\gamma$-ray measurements of distant TeV blazars can be nicely explained by TeV spectra induced by ultra high-energy cosmic rays. Aims. We develop a model for a plausible origin of hard spectra in distant TeV blazars. Methods. In the model, the TeV emission in distant TeV blazars is dominated by two mixed components. The first is the internal component with the photon energy around 1 TeV produced by inverse Compton scattering of the relativistic electrons on the synchrotron photons (SSC) with a correction for extragalactic background light absorbtion and the other is the external component with the photon energy more than 1 TeV produced by the cascade emission from high-energy protons propagating through intergalactic space. Results. Assuming suitable model parameters, we apply the model to observed spectra of distant TeV blazars of 1ES 0229+200. Our results show that 1) the observed spectrum properties of 1ES 0229+200, especially the TeV $\\gamma$-ray tail of the observed spect...

  15. Radio core dominance of Fermi blazars

    Science.gov (United States)

    Pei, Zhi-Yuan; Fan, Jun-Hui; Liu, Yi; Yuan, Yi-Hai; Cai, Wei; Xiao, Hu-Bing; Lin, Chao; Yang, Jiang-He

    2016-07-01

    During the first 4 years of mission, Fermi/LAT detected 1444 blazars (3FGL) (Ackermann et al. in Astrophys. J. 810:14, 2015). Fermi/LAT observations of blazars indicate that Fermi blazars are luminous and strongly variable with variability time scales, for some cases, as short as hours. Those observations suggest a strong beaming effect in Fermi/LAT blazars. In the present work, we will investigate the beaming effect in Fermi/LAT blazars using a core-dominance parameter, R = S_{core}/ S_{ext.}, where S_{core} is the core emission, while S_{ext.} is the extended emission. We compiled 1335 blazars with available core-dominance parameter, out of which 169 blazars have γ-ray emission (from 3FGL). We compared the core-dominance parameters, log R, between the 169 Fermi-detected blazars (FDBs) and the rest non-Fermi-detected blazars (non-FDBs), and we found that the averaged values are ext.} = 0.70 (a photon spectral index of α_{γ}^{ph}|_{ext.} = 1.70). Some discussions are also presented.

  16. Optical Spectral Variability of Blazars

    Indian Academy of Sciences (India)

    Haritma Gaur

    2014-09-01

    It is well established that blazars show flux variations in the complete electromagnetic (EM) spectrum on all possible time scales ranging from a few tens of minutes to several years. Here, we report the review of optical flux and spectral variability properties of different classes of blazars on IDV and STV time-scales. Our analysis show HSPs are less variable in optical bands as compared to LSPs. Also, we investigated the spectral slope variability and found that the average spectral slopes of LSPs showed a good agreement with the synchrotron self-Compton loss-dominated model. However, spectra of the HSPs and FSRQs have significant additional emission components. In general, spectra of BL Lacs get flatter when they become brighter, while for FSRQs the opposite trend appears to hold.

  17. VERITAS detection of $\\gamma$-ray flaring activity from the BL Lac object 1ES 1727+502 during bright moonlight observations

    CERN Document Server

    Archambault, S; Beilicke, M; Benbow, W; Bird, R; Biteau, J; Bouvier, A; Bugaev, V; Cardenzana, J V; Cerruti, M; Chen, X; Ciupik, L; Connolly, M P; Cui, W; Dickinson, H J; Dumm, J; Eisch, J D; Errando, M; Falcone, A; Feng, Q; Finley, J P; Fleischhack, H; Fortin, P; Fortson, L; Furniss, A; Gillanders, G H; Griffin, S; Griffiths, S T; Grube, J; Gyuk, G; Håkansson, N; Hanna, D; Holder, J; Humensky, T B; Johnson, C A; Kaaret, P; Kar, P; Kertzman, M; Khassen, Y; Kieda, D; Krause, M; Krennrich, F; Kumar, S; Lang, M J; Maier, G; McArthur, S; McCann, A; Meagher, K; Millis, J; Moriarty, P; Mukherjee, R; Nieto, D; de Bhróithe, A O'Faoláin; Ong, R A; Otte, A N; Park, N; Pohl, M; Popkow, A; Prokoph, H; Pueschel, E; Quinn, J; Ragan, K; Reyes, L C; Reynolds, P T; Richards, G T; Roache, E; Santander, M; Sembroski, G H; Shahinyan, K; Smith, A W; Staszak, D; Telezhinsky, I; Tucci, J V; Tyler, J; Varlotta, A; Vincent, S; Wakely, S P; Weinstein, A; Welsing, R; Wilhelm, A; Williams, D A; Zitzer, B; Hughes, Z D

    2015-01-01

    During moonlit nights, observations with ground-based Cherenkov telescopes at very high energies (VHE, $E>100$ GeV) are constrained since the photomultiplier tubes (PMTs) in the telescope camera are extremely sensitive to the background moonlight. Observations with the VERITAS telescopes in the standard configuration are performed only with a moon illumination less than 35$\\%$ of full moon. Since 2012, the VERITAS collaboration has implemented a new observing mode under bright moonlight, by either reducing the voltage applied to the PMTs (reduced-high-voltage configuration, RHV), or by utilizing UV-transparent filters. While these operating modes result in lower sensitivity and increased energy thresholds, the extension of the available observing time is useful for monitoring variable sources such as blazars and sources requiring spectral measurements at the highest energies. In this paper we report the detection of $\\gamma$-ray flaring activity from the BL Lac object 1ES 1727+502 during RHV observations. Thi...

  18. On the classification of flaring states of blazar

    CERN Document Server

    Resconi, E; Gross, A; Costamante, L; Flaccomio, E

    2009-01-01

    The time evolution of the electromagnetic emission from blazars, in particular high frequency peaked sources (HBLs), displays irregular activity not yet understood. In this work we report a methodology capable of characterizing the time behavior of these variable objects. The Maximum Likelihood Blocks (MLBs) is a model-independent estimator which sub-divides the light curve into time blocks, whose length and amplitude are compatible with states of constant emission rate of the observed source. The MLBs yields the statistical significance in the rate variations and strongly suppresses the noise fluctuations in the light curves. We apply the MLBs for the first time on the long term X-ray light curves (RXTE/ASM) of Mkn~421,Mkn~501, 1ES 1959+650 and 1ES 2155-304, which consist of more than 10 years of observational data (1996-2007). Using the MLBs interpretation of RXTE/ASM data, the integrated time flux distribution is determined for each single source considered. We identify in these distributions the character...

  19. HIGH ENERGY POLARIZATION OF BLAZARS: DETECTION PROSPECTS

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, N. [Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany); Pavlidou, V. [Department of Physics, University of Crete, 71003 Heraklion (Greece); Fields, B. D. [Department of Astronomy and Department of Physics, University of Illinois, Urbana, IL 61801 (United States)

    2015-01-01

    Emission from blazar jets in the ultraviolet, optical, and infrared is polarized. If these low-energy photons were inverse-Compton scattered, the upscattered high-energy photons retain a fraction of the polarization. Current and future X-ray and gamma-ray polarimeters such as INTEGRAL-SPI, PoGOLITE, X-Calibur, Gamma-Ray Burst Polarimeter, GEMS-like missions, ASTRO-H, and POLARIX have the potential to discover polarized X-rays and gamma-rays from blazar jets for the first time. Detection of such polarization will open a qualitatively new window into high-energy blazar emission; actual measurements of polarization degree and angle will quantitatively test theories of jet emission mechanisms. We examine the detection prospects of blazars by these polarimetry missions using examples of 3C 279, PKS 1510-089, and 3C 454.3, bright sources with relatively high degrees of low-energy polarization. We conclude that while balloon polarimeters will be challenged to detect blazars within reasonable observational times (with X-Calibur offering the most promising prospects), space-based missions should detect the brightest blazars for polarization fractions down to a few percent. Typical flaring activity of blazars could boost the overall number of polarimetric detections by nearly a factor of five to six purely accounting for flux increase of the brightest of the comprehensive, all-sky, Fermi-LAT blazar distribution. The instantaneous increase in the number of detections is approximately a factor of two, assuming a duty cycle of 20% for every source. The detectability of particular blazars may be reduced if variations in the flux and polarization fraction are anticorrelated. Simultaneous use of variability and polarization trends could guide the selection of blazars for high-energy polarimetric observations.

  20. Stochastic Particle Acceleration in Blazar Jets

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The bulk kinetic energy of jets can be dissipated via generating tur bulent plasma waves. We examine stochastic particle acceleration in blazar jets to explain the emissions of all blazars. We show that acceleration of electrons by plasma turbulence waves with a spectrum W(k) ~ k-4/3 produces a nonthermal population of relativistic electrons whose peak frequency of synchrotron emission can fit the observational trends in the spectral energy distribution of all blazars.The plasma nonlinear processes responsible for the formation of turbulent spectrum are investigated. Increases in the interaction time of turbulent waves can produce a flatter speckrum leading to efficient particle acceleration.

  1. Variability along the Blazar-Sequence - Hints for extragalactic Cosmic Rays?

    CERN Document Server

    Weidinger, Matthias

    2011-01-01

    The spectral energy distribution and variability of several blazars (Mkn 501, 1 ES 2344+51.4, PKS 2155-30.4, 1 ES 1218+30.4, 3C 454.3) along the blazar sequence is investigated using a selfconsistent and timedependent lepto-hadronic hybrid emission model. The BL Lac objects in the list are successfully modelled with purely leptonic radiation processes (essentially Synchrotron Self-Compton emission), while the Flat Spectrum Radio Quasar requires highly relativistic hadrons to be present within the jet. Variability is exploited as well with our model to distinguish between Self-Compton and hadronic gamma radiation making use of their different signatures in lightcurves. As a consequence active galactic nuclei with z > 0.5 are the best candidates as sources of extragalactic consmic rays, since High-Peaked BL Lac objects do not seem to accelerate protons to energies above thermal. Furthermore the parameters found during the modelling of the objects agree very well with obervations of e.g. superluminal motion or t...

  2. A model for periodic blazars

    CERN Document Server

    Sobacchi, Emanuele; Stamerra, Antonio

    2016-01-01

    We describe a scenario to explain blazar periodicities with timescales of $\\sim$ few years. The scenario is based on a binary super-massive black hole (SMBH) system in which one of the two SMBH carries a jet. We discuss the various mechanisms that can cause the jet to precess and produce corkscrew patterns through space with a scale of $\\sim$ few pc. It turns out that the dominant mechanism responsible for the precession is simply the imprint of the jet-carrying SMBH orbital speed on the jet. Gravitational deflection and Lense-Thirring precession (due to the gravitational field of the other SMBH) are second order effects. We complement the scenario with a kinematical jet model which is inspired to the spine-sheath structure observed in M87. One of the main advantages of such a structure is that it allows the peak of the synchrotron emission to scale with frequency according to $\

  3. Fourier Analysis of Blazar Variability

    CERN Document Server

    Finke, Justin D

    2014-01-01

    Blazars display strong variability on multiple timescales and in multiple radiation bands. Their variability is often characterized by power spectral densities (PSDs) and time lags plotted as functions of the Fourier frequency. We develop a new theoretical model based on the analysis of the electron transport (continuity) equation, carried out in the Fourier domain. The continuity equation includes electron cooling and escape, and a derivation of the emission properties includes light travel time effects associated with a radiating blob in a relativistic jet. The model successfully reproduces the general shapes of the observed PSDs and predicts specific PSD and time lag behaviors associated with variability in the synchrotron, synchrotron self-Compton (SSC), and external Compton (EC) emission components, from sub-mm to gamma-rays. We discuss applications to BL Lacertae objects and to flat-spectrum radio quasars (FSRQs), where there are hints that some of the predicted features have already been observed. We a...

  4. Constraining Emission Models of Luminous Blazar Sources

    International Nuclear Information System (INIS)

    Many luminous blazars which are associated with quasar-type active galactic nuclei display broad-band spectra characterized by a large luminosity ratio of their high-energy (γ-ray) and low-energy (synchrotron) spectral components. This large ratio, reaching values up to 100, challenges the standard synchrotron self-Compton models by means of substantial departures from the minimum power condition. Luminous blazars have also typically very hard X-ray spectra, and those in turn seem to challenge hadronic scenarios for the high energy blazar emission. As shown in this paper, no such problems are faced by the models which involve Comptonization of radiation provided by a broad-line-region, or dusty molecular torus. The lack or weakness of bulk Compton and Klein-Nishina features indicated by the presently available data favors production of γ-rays via up-scattering of infrared photons from hot dust. This implies that the blazar emission zone is located at parsec-scale distances from the nucleus, and as such is possibly associated with the extended, quasi-stationary reconfinement shocks formed in relativistic outflows. This scenario predicts characteristic timescales for flux changes in luminous blazars to be days/weeks, consistent with the variability patterns observed in such systems at infrared, optical and γ-ray frequencies. We also propose that the parsec-scale blazar activity can be occasionally accompanied by dissipative events taking place at sub-parsec distances and powered by internal shocks and/or reconnection of magnetic fields. These could account for the multiwavelength intra-day flares occasionally observed in powerful blazars sources.

  5. CONSTRAINING EMISSION MODELS OF LUMINOUS BLAZAR SOURCES

    International Nuclear Information System (INIS)

    Many luminous blazars which are associated with quasar-type active galactic nuclei display broadband spectra characterized by a large luminosity ratio of their high-energy (γ-ray) and low-energy (synchrotron) spectral components. This large ratio, reaching values up to 100, challenges the standard synchrotron self-Compton models by means of substantial departures from the minimum power condition. Luminous blazars also typically have very hard X-ray spectra, and those in turn seem to challenge hadronic scenarios for the high-energy blazar emission. As shown in this paper, no such problems are faced by the models which involve Comptonization of radiation provided by a broad-line region, or dusty molecular torus. The lack or weakness of bulk-Compton and Klein-Nishina features indicated by the presently available data favors the production of γ-rays via upscattering of infrared photons from hot dust. This implies that the blazar emission zone is located at parsec-scale distances from the nucleus, and as such is possibly associated with the extended, quasi-stationary reconfinement shocks formed in relativistic outflows. This scenario predicts characteristic timescales for flux changes in luminous blazars to be days/weeks, consistent with the variability patterns observed in such systems at infrared, optical, and γ-ray frequencies. We also propose that the parsec-scale blazar activity can be occasionally accompanied by dissipative events taking place at sub-parsec distances and powered by internal shocks and/or reconnection of magnetic fields. These could account for the multiwavelength intraday flares occasionally observed in powerful blazar sources.

  6. Constraining Emission Models of Luminous Blazar Sources

    Energy Technology Data Exchange (ETDEWEB)

    Sikora, Marek; /Warsaw, Copernicus Astron. Ctr.; Stawarz, Lukasz; /Kipac, Menlo Park /Jagiellonian U., Astron. Observ. /SLAC; Moderski, Rafal; Nalewajko, Krzysztof; /Warsaw, Copernicus Astron. Ctr.; Madejski, Greg; /KIPAC, Menlo Park /SLAC

    2009-10-30

    Many luminous blazars which are associated with quasar-type active galactic nuclei display broad-band spectra characterized by a large luminosity ratio of their high-energy ({gamma}-ray) and low-energy (synchrotron) spectral components. This large ratio, reaching values up to 100, challenges the standard synchrotron self-Compton models by means of substantial departures from the minimum power condition. Luminous blazars have also typically very hard X-ray spectra, and those in turn seem to challenge hadronic scenarios for the high energy blazar emission. As shown in this paper, no such problems are faced by the models which involve Comptonization of radiation provided by a broad-line-region, or dusty molecular torus. The lack or weakness of bulk Compton and Klein-Nishina features indicated by the presently available data favors production of {gamma}-rays via up-scattering of infrared photons from hot dust. This implies that the blazar emission zone is located at parsec-scale distances from the nucleus, and as such is possibly associated with the extended, quasi-stationary reconfinement shocks formed in relativistic outflows. This scenario predicts characteristic timescales for flux changes in luminous blazars to be days/weeks, consistent with the variability patterns observed in such systems at infrared, optical and {gamma}-ray frequencies. We also propose that the parsec-scale blazar activity can be occasionally accompanied by dissipative events taking place at sub-parsec distances and powered by internal shocks and/or reconnection of magnetic fields. These could account for the multiwavelength intra-day flares occasionally observed in powerful blazars sources.

  7. High Energy Polarization of Blazars : Detection Prospects

    CERN Document Server

    Chakraborty, Nachiketa; Fields, Brian

    2015-01-01

    Emission from blazar jets in the ultraviolet, optical, and infrared is polarized. If these low-energy photons were inverse-Compton scattered, the upscattered high-energy photons retain a fraction of the polarization. Current and future X-ray and gamma-ray polarimeters such as INTEGRAL-SPI, PoGOLITE, X-Calibur, Gamma-Ray Burst Polarimeter, GEMS-like missions, ASTRO-H, and POLARIX have the potential to discover polarized X-rays and gamma-rays from blazar jets for the first time. Detection of such polarization will open a qualitatively new window into high-energy blazar emission; actual measurements of polarization degree and angle will quantitatively test theories of jet emission mechanisms. We examine the detection prospects of blazars by these polarimetry missions using examples of 3C 279, PKS 1510-089, and 3C 454.3, bright sources with relatively high degrees of low-energy polarization. We conclude that while balloon polarimeters will be challenged to detect blazars within reasonable observational times (wit...

  8. Fermi detected blazars seen by INTEGRAL

    CERN Document Server

    Beckmann, V; Soldi, S

    2009-01-01

    Multiwavelength observations are essential to constrain physical parameters of the blazars observed by Fermi/LAT. Among the 187 AGN significantly detected in public INTEGRAL data above 20 keV by the imager IBIS/ISGRI, 20 blazars were detected. 15 of these sources allowed significant spectral extraction. They show hard X-ray spectra with an average photon index of 2.1+-0.1 and a hard X-ray luminosity of L(20-100 keV) = 1.3e46 erg/s. 15 of the INTEGRAL blazars are also visible in the first 16 months of the Fermi/LAT data, thus allowing to constrain the inverse Compton branch in these cases. Among others, we analyse the LAT data of four blazars which were not included in the Fermi LAT Bright AGN Sample based on the first 3 months of the mission: QSO B0836+710, H 1426+428, RX J1924.8-2914, and PKS 2149-306. Especially for blazars during bright outbursts, as already observed simultaneously by INTEGRAL and Fermi (e.g. 3C 454.3 and Mrk 421), INTEGRAL provides unique spectral coverage up to several hundred keV. We pr...

  9. Recent highlights in the X-ray study of blazars

    CERN Document Server

    Pian, E

    2002-01-01

    Blazars exhibit flux and spectral variations of largest amplitude at the highest frequencies. Therefore, monitoring their variability at X- and gamma-rays is the most effective tool to peer into the mighty powerhouse of these sources. High energy observations of the brightest blazars with the latest generation of satellites have allowed a detailed study of their behavior and have critically improved our understanding of the physics of blazar jets. I will review some of the recent results of blazar multiwavelength monitoring with emphasis on the X-ray campaigns accomplished with BeppoSAX and I will describe some of the future programs for blazar investigation from space, particularly with INTEGRAL.

  10. Steady-state emission of blazars at very high energies

    Energy Technology Data Exchange (ETDEWEB)

    Hoehne-Moench, Daniel

    2010-07-01

    One key scientific program of the MAGIC telescope project is the discovery and detection of blazars. They constitute the most prominent extragalactic source class in the very high energy (VHE) {gamma}-ray regime with 29 out of 34 known objects. Therefore a major part of the available observation time was spent in the last years on high-frequency peaked blazars. The selection criteria were chosen to increase the detection probability. As the X-ray flux is believed to be correlated to the VHE {gamma}-ray flux, only X-ray selected sources with a flux F{sub X}>2 {mu}Jy at 1 keV were considered. To avoid strong attenuation of the -rays in the extragalactic infrared background, the redshift was restricted to values between z<0.15 and z<0.4, depending on the declination of the objects. The latter determines the zenith distance during culmination which should not exceed 30 (for z<0.4) and 45 (for z<0.15), respectively. Between August 2005 and April 2009, a sample of 24 X-ray selected high-frequency peaked blazars has been observed with the MAGIC telescope. Three of them were detected including 1ES 1218+304 being the first high-frequency peaked BL Lacertae object (HBL) to be discovered with MAGIC in VHE {gamma}-rays. One previously detected object was not confirmed as VHE emitter in this campaign by MAGIC. A set of 20 blazars previously not detected is treated more closely in this work. In this campaign, during almost four years {proportional_to}450 hrs or {proportional_to}22% of the available observation time for extragalactic objects were dedicated to investigate the baseline emission of blazars and their broadband spectral properties in this emission state. For the sample of 20 objects in a redshift range of 0.018

  11. Multiwavelength Emission from Blazars – Conference Summary

    Indian Academy of Sciences (India)

    Meg Urry

    2011-03-01

    Presentations at the Guangzhou Conference on Multiwave-length Emission from Blazars confirmed our understanding of blazars as relativistic jets closely aligned with the line of sight. Powerful new studies have been enabled by the Fermi gamma-ray satellite and new ground-based TeV facilities, which are an order of magnitude more sensitive than their predecessors. Combining gamma-ray data with VLBA radio and with optical/IR photometry has shed new light on the emission mechanisms and the jet geometry. This conference summary sets the context for the 4th blazar conference and presents some of the highlights from the meeting, as well as the questions that remain outstanding.

  12. Relativistic Beaming Effect in Fermi Blazars

    Indian Academy of Sciences (India)

    J. H. Fan; D. Bastieri; J. H. Yang; Y. Liu; D. X. Wu; S. H. Li

    2014-09-01

    The most identified sources observed by Fermi/LAT are blazars, based on which we can investigate the emission mechanisms and beaming effect in the -ray bands for blazars. Here, we used the compiled around 450 Fermi blazars with the available X-ray observations to estimate their Doppler factors and compared them with the integral -ray luminosity in the range of 1–100 GeV. It is interesting that the integral -ray luminosity is closely correlated with the estimated Doppler factor, log = (2.95 ± 0.09) log + 43.59 ± 0.08 for the whole sample. When the dependence of the correlation between them and the X-ray luminosity is removed, the correlation is still strong, which suggests that the -ray emissions are strongly beamed.

  13. Powers and Magnetization of Blazar Jets

    CERN Document Server

    Sikora, Marek

    2016-01-01

    In this work I review the observational constraints imposed on the energetics and magnetisation of quasar jets, in the context of theoretical expectations. The discussion is focused on issues regarding the jet production efficiency, matter content, and particle acceleration. I show that if the ratio of electron-positron-pairs to protons is of order $15$, as is required to achieve agreement between jet powers computed using blazar spectral fits and those computed using radio-lobe calorimetry, the magnetization of blazar jets in flat-spectrum-radio-quasars (FSRQ) must be significant. This result favors the reconnection mechanism for particle acceleration and explains the large Compton-dominance of blazar spectra that is often observed, without the need to postulate very low jet magnetization.

  14. What determines the observational differences of blazars?

    CERN Document Server

    Fan, Xu-Liang; Mao, Jirong

    2016-01-01

    We examine the scenario that the Doppler factor determines the observational differences of blazars in this paper. Significantly negative correlations are found between the observational synchrotron peak frequency and the Doppler factor. After correcting the Doppler boosting, the intrinsic peak frequency further has a tightly linear relation with the Doppler factor. It is more interesting that this relation is consistent with the scenario that the black hole mass governs both the bulk Lorentz factor and the synchrotron peak frequency. In addition, the distinction of the kinetic jet powers between BL Lacs and FSRQs disappears after the boosting factor $\\delta^2$ is considered. The negative correlation between the peak frequency and the observational isotropic luminosity, known as the blazar sequence, also disappears after the Doppler boosting is corrected. We also find that the correlation between the Compton dominance and the Doppler factor exists for all types of blazars. Therefore, this correlation is unsui...

  15. TeV blazars and their distance

    CERN Document Server

    Prandini, Elisa; Maraschi, Laura; Mariotti, Mose'; Tavecchio, Fabrizio

    2011-01-01

    Recently, a new method to constrain the distance of blazars with unknown redshift using combined observations in the GeV and TeV regimes has been developed, with the underlying assumption that the Very High Energy (VHE) spectrum corrected for the absorption of TeV photons by the Extragalactic Background Light (EBL) via photon-photon interaction should still be softer than the gamma-ray spectrum observed by Fermi/LAT. The constraints found are related to the real redshifts by a simple linear relation, that has been used to infer the unknown distance of blazars. The sample will be revised with the up-to-date spectra in both TeV and GeV bands, the method tested with the more recent EBL models and finally applied to the unknown distance blazars detected at VHE.

  16. Modeling the Emission Processes in Blazars

    CERN Document Server

    Böttcher, M

    2006-01-01

    Blazars are the most violent steady/recurrent sources of high-energy gamma-ray emission in the known Universe. They are prominent emitters of electromagnetic radiation throughout the entire electromagnetic spectrum. The observable radiation most likely originates in a relativistic jet oriented at a small angle with respect to the line of sight. This review starts out with a general overview of the phenomenology of blazars, including results from a recent multiwavelength observing campaign on 3C279. Subsequently, issues of modeling broadband spectra will be discussed. Spectral information alone is not sufficient to distinguish between competing models and to constrain essential parameters, in particular related to the primary particle acceleration and radiation mechanisms in the jet. Short-term spectral variability information may help to break such model degeneracies, which will require snap-shot spectral information on intraday time scales, which may soon be achievable for many blazars even in the gamma-ray ...

  17. Core shifts in blazar jets

    CERN Document Server

    Zdziarski, Andrzej A; Pjanka, Patryk; Tchekhovskoy, Alexander

    2014-01-01

    We study the effect of core shift in jets, which is the dependence of the position of the jet radio core on the frequency. We derive a new method to measure the jet magnetic field based on both the value of the shift and the observed flux, which compliments the standard method assuming equipartition. Using both methods, we re-analyse the blazar sample of Zamaninasab et al. We find that equipartition is satisfied only if the jet opening angle in the radio core region is close to the values found observationally, $\\simeq$0.1--0.2 divided by the bulk Lorentz factor, $\\Gamma_{\\rm j}$. Larger values, e.g., $1/\\Gamma_{\\rm j}$, would imply very strong departures from equipartition. A small jet opening angle implies in turn the magnetization parameter of $\\ll 1$. We determine the jet magnetic flux taking this effect into account. We find that the average jet magnetic flux is compatible with the model of jet formation due to black-hole spin energy extraction and accretion being magnetically arrested. We calculate the ...

  18. The Spectral Energy Distributions of Fermi Blazars

    Science.gov (United States)

    Fan, J. H.; Yang, J. H.; Liu, Y.; Luo, G. Y.; Lin, C.; Yuan, Y. H.; Xiao, H. B.; Zhou, A. Y.; Hua, T. X.; Pei, Z. Y.

    2016-10-01

    In this paper, multiwavelength data are compiled for a sample of 1425 Fermi blazars to calculate their spectral energy distributions (SEDs). A parabolic function, {{log}}{(ν {F}ν )={P}1({{log}}ν -{P}2)}2+{P}3, is used for SED fitting. Synchrotron peak frequency ({log}{ν }{{p}}), spectral curvature (P1), peak flux ({ν }{{p}}{F}{ν {{p}}}), and integrated flux (ν {F}ν ) are successfully obtained for 1392 blazars (461 flat-spectrum radio quasars [FSRQs], 620 BL Lacs [BLs], and 311 blazars of uncertain type [BCUs]; 999 sources have known redshifts). Monochromatic luminosity at radio 1.4 GHz, optical R band, X-ray at 1 keV and γ-ray at 1 GeV, peak luminosity, integrated luminosity, and effective spectral indices of radio to optical ({α }{{RO}}) and optical to X-ray ({α }{{OX}}) are calculated. The “Bayesian classification” is employed to log {ν }{{p}} in the rest frame for 999 blazars with available redshift, and the results show that three components are enough to fit the log {ν }{{p}} distribution; there is no ultra-high peaked subclass. Based on the three components, the subclasses of blazars using the acronyms of Abdo et al. are classified, and some mutual correlations are also studied. Conclusions are finally drawn as follows: (1) SEDs are successfully obtained for 1392 blazars. The fitted peak frequencies are compared with common sources from available samples. (2) Blazars are classified as low synchrotron peak sources if log {ν }{{p}}({Hz})≤slant 14.0, intermediate synchrotron peak sources if 14.0\\lt {log} {ν }{{p}}({Hz})≤slant 15.3, and high synchrotron peak sources if {log} {ν }{{p}}({Hz})\\gt 15.3. (3) Gamma-ray emissions are strongly correlated with radio emissions. Gamma-ray luminosity is also correlated with synchrotron peak luminosity and integrated luminosity. (4) There is an anticorrelation between peak frequency and peak luminosity within the whole blazar sample. However, there is a marginally positive correlation for high

  19. Probes of the inner jets of blazars.

    OpenAIRE

    A. P. Marscher(Institute for Astrophysical Research, Boston University, Boston, USA)

    1995-01-01

    I review models for the "inner jet" in blazars, the section that connects the central engine with the radio jet. I discuss how the structure and physics of the inner jet can be explored using millimeter-wave VLBI (very-long-baseline radio interferometry) as well as multiwaveband observations of blazars. Flares at radio to gamma-ray frequencies should exhibit time delays at different wavebands that can test models for both the high-energy emission mechanisms and the nature of the inner jet in ...

  20. General physical properties of bright Fermi blazars

    CERN Document Server

    Ghisellini, G; Foschini, L; Ghirlanda, G; Maraschi, L; Celotti, A

    2009-01-01

    We studied all blazars of known redshift detected by the Fermi satellite during its first three months survey. For the majority of them, pointed Swift observations ensures a good multiwavelength coverage, enabling us to to reliably construct their spectral energy distributions (SED). We model the SEDs using a one-zone leptonic model and study the distributions of the derived interesting physical parameters as a function of the observed gamma-ray luminosity. We confirm previous findings concerning the relation of the physical parameters with source luminosity which are at the origin of the blazar sequence. The SEDs allow to estimate the luminosity of the accretion disk for the majority of broad emitting line blazars, while for the line-less BL Lac objects in the sample upper limits can be derived. We find a positive correlation between the jet power and the luminosity of the accretion disk in broad line blazars. In these objects we argue that the jet must be proton-dominated, and that the total jet power is of...

  1. Estimating Black Hole Masses of Blazars

    Indian Academy of Sciences (India)

    Xue-Bing Wu; F. K. Liu; M. Z. Kong; R. Wang; J. L. Han

    2011-03-01

    Estimating black hole masses of blazars is still a big challenge. Because of the contamination of jets, using the previously suggested size–continuum luminosity relation can overestimate the broad line region (BLR) size and black hole mass for radio-loud AGNs, including blazars. We propose a new relation between the BLR size and emission line luminosity and present evidences for using it to get more accurate black hole masses of radio-loud AGNs. For extremely radio-loud AGNs such as blazars with weak/absent emission lines, we suggest the use of fundamental plane relation of their elliptical host galaxies to estimate the central velocity dispersions and black hole masses, if their velocity dispersions are not known but the host galaxies can be mapped. The black hole masses of some well-known blazars, such as OJ 287, AO 0235+164 and 3C 66B are obtained using these two methods and the – relation. The implications of their black hole masses on other related studies are also discussed.

  2. The GTN-AAVSO Blazar Program

    Science.gov (United States)

    Cominsky, L. R.; Spear, G. G.; Graves, T.; Slater, G.; Price, A.

    2004-08-01

    The GLAST Telescope Network (GTN) is a collaboration among students, teachers, amateur astronomers, small college observatories, and professional astronomers who will obtain observations of base-line activity levels and follow-up observations for bright blazars, one of the key science objectives for NASA's Gamma-ray Large Area Space Telescope (GLAST) mission. A key partner in the GTN is the American Association of Variable Star Observers (AAVSO, a non-profit international scientific and educational organization that has considerable experience with handling, processing, and displaying large amounts of data and with coordinating observers from every corner of the globe. The GTN-AAVSO blazar program will recommend observing sequences, and provide advice and mentoring for observing techniques and data reduction. The program will archive magnitude estimates using the AAVSO database system and lightcurve generator, as well as CCD images of blazar fields. The program will also employ the online image archiving system developed by the GTN. Images of blazar fields will be available for subsequent analysis by contributors to the program, and by the GLAST science team for mission planning and follow-up studies. We will present examples of the AAVSO lightcurve generator, examples of the GTN image archive system, plus examples of the data we are currently accumulating. The GTN-AAVSO collaboration is partially funded by the NASA's GLAST Education and Public Outreach Program.

  3. The blazar sequence 2.0

    CERN Document Server

    Ghisellini, Gabriele

    2016-01-01

    I discuss the spectral energy distribution (SED) of all blazars with redshift detected by the {\\it Fermi} satellite and listed in the 3LAC catalog. I will update the so called "blazar sequence" from the phenomenological point of view, with no theory or modelling. I will show that: i) pure data show that jet and accretion power are related; ii) the updated blazar sequence maintains the properties of the old version, albeit with a less pronounced dominance of the $\\gamma$--ray emission; iii) at low bolometric luminosities, two different type of objects have the same high energy power: low black hole mass flat spectrum radio quasars and high mass BL Lacs. Therefore, at low luminosities, there is a very large dispersion of SED shapes; iv) in low power BL Lacs, the contribution of the host galaxy is important. Remarkably, the luminosity distribution of the host galaxies of BL Lacs are spread in a very narrow range; v) a simple sum of two smoothly joining power laws can describe the blazar SEDs very well.

  4. Chandra View of the Warm-Hot IGM toward 1ES 1553+113: Absorption Line Detections and Identifications (Paper I)

    CERN Document Server

    Nicastro, F; Krongold, Y; Mathur, S; Gupta, A; Danforth, C; Barcons, X; Borgani, S; Branchini, E; Cen, R; Davé, R; Kaastra, J; Paerels, F; Piro, L; Shull, J M; Takei, Y; Zappacosta, L

    2012-01-01

    About 30-40 percent of the expected number of baryons is still missing in the local Universe (z \\lesssim 0.4). They are predicted to be hiding in a web of intergalactic gas at temperatures of about 10^5-10^7 K (the WHIM). Detecting this matter has had limited success so far, because of its low-density and high temperature, which makes it difficult to detect with current far-ultraviolet and X-ray instrumentation. Here we present the first results from our pilot 500 ks Chandra-LETG observation of the soft X-ray brightest source in the z > 0.4 sky, the blazar 1ES 1553+113. We identify a total of 11 possible absorption lines, with single-line statistical significances between 2.2-4.1 sigma. Six of these lines are detected at high significance (3.6 < \\sigma < 4.1), while the remaining five are regarded as marginal detections in association with either other X-ray lines detected at higher significance and/or FUV signposts. Three of these lines are consistent with metal absorption at z~0. The remaining 8 lines...

  5. UV and X-ray Variability of Blazars

    Indian Academy of Sciences (India)

    Alok C. Gupta

    2011-03-01

    It is well established that the blazars show flux variations in the complete electromagnetic (EM) spectrum on all possible time scales ranging from a few tens of minutes to several years. Here we report the review of various UV and X-ray flux variability properties of blazars. Our analysis show that UV variability amplitude is smaller than X-rays, mostly soft X-rays hardness ratio show correlations with blazar luminosity and different modes of variability might be operating for different time scales and epochs. Quasi periodic oscillations are seen on a few occasions in blazars, higher fraction of high energy peaked blazars show intra day and short term variabilities in X-rays but variability duty cycle is much less in optical bands on intra day time scale compared to low energy peaked blazars. But these results are yet to be established.

  6. Correlation Analysis of Multi-Wavelength Luminosity of Fermi Blazars

    Indian Academy of Sciences (India)

    Xiongwei Bi; Wanquan He; Jiajin Tian; Zhimei Ding; Shuping Ge

    2014-09-01

    We have studied the correlations between luminosities (R, O, X, ) in radio, optical, X-ray and -ray wave bands for Fermi blazars, and found that there are significant correlations between R and , X and and O and for blazars, BL Lacs and FSRQs, but no correlation between and O for BL Lacs. These results suggest that for Fermi blazars, the high energy -ray emission can be related with radio, X-ray and optical emissions.

  7. Neutral Beams from Blazar Jets

    Science.gov (United States)

    Atoyan, Armen M.; Dermer, Charles D.

    2003-03-01

    We treat the production of neutrons, photons, and neutrinos through photomeson interactions of relativistic protons with ambient photons in the compact inner jets of blazars. Internal synchrotron and external isotropic radiation due to scattered optical/UV accretion-disk radiation are considered as target photon fields. Protons are assumed to be accelerated to a maximum energy limited by the size scale and magnetic field of the jet, and by competing energy losses. We characterize the conditions when the photomeson interactions of ultrarelativistic protons become effective, and show that the presence of the external radiation field makes possible strong energy losses for protons with energies Ep>~1015 eV. Without this component, effective energy losses of protons begin at Ep>~1018 eV, and would rapidly disappear with expansion of the blob. We develop a model describing the production and escape of neutrons from a comoving spherical blob, which continue to interact with the ambient external radiation field on the parsec-scale broad-line region (BLR). Neutrons may carry ~10% of the overall energy of the accelerated protons with Ep>~1015 eV outside the BLR. Ultra-high-energy gamma rays produced by photomeson interaction of neutrons outside the blob can also escape the BLR. The escaping neutrons, gamma rays, and neutrinos form a collimated neutral beam with a characteristic opening angle θ~1/Γ, where Γ is the bulk Lorentz factor of the inner jet. Energy and momentum is deposited in the extended jet from the decay of neutrons at distances ld(En)~(En/1017eV) kpc, and through pair-production attenuation of gamma rays with energies Eγ>~1015 eV which propagate to ~10-100 kpc distances. In this scenario, neutral beams of ultra-high-energy gamma rays and neutrons can be the reason for straight extended jets, such as in Pictor A. Fluxes of neutrinos detectable with kilometer-scale neutrino telescopes are predicted from flat-spectrum radio quasars such as 3C 279.

  8. APEX sub-mm monitoring of gamma-ray blazars

    CERN Document Server

    Larsson, S; Weiss, A; Angelakis, E; Krichbaum, T P; Nestoras, I; Zensus, J A; Axelsson, M; Nilsson, D; Ryde, F; Hjalmarsdotter, L; Larsson, J; Lundgren, A; Mac-Auliffe, F; Parra, R; Siringo, G

    2012-01-01

    So far, no systematic long-term blazar monitoring programs and detailed variability studies exist at sub-mm wavelengths. Here, we present a new sub-mm blazar monitoring program using the APEX 12-m telescope. A sample of about 40 gamma-ray blazars has been monitored since 2007/2008 with the LABOCA bolometer camera at 345 GHz. First light curves, preliminary variability results and a first comparison with the longer cm/mm bands (F-GAMMA program) are presented, demonstrating the extreme variability characteristics of blazars at such short wavelengths.

  9. ELECTROPORATION OF CONFLUENT HM-1 ES CELLS LEADS TO HIGHER AMOUNT COLONIES

    Directory of Open Access Journals (Sweden)

    A.ALENA BENCSIK

    2013-12-01

    Full Text Available Electroporation is used to induce homologous recombination in the genome of the murine ES (embryonic stem cells. Routinelly subconfluent ES cells are recommended to be used in such experiments. Electroporation of immunoglobulin specific targeting vectors with different length of homology leads to reduced number of selected colonies. The enrichment of double selected colonies is high and thus the amount of HM-1 ES cell colonies for the analysis is very low. Here we show that the electroporation of confluent HM-1 ES cells leads to an increased amount of simple and double selected colonies.

  10. 2WHSP: A catalog of HE and VHE gamma-ray blazars and blazar candidates

    CERN Document Server

    Chang, Yu-Ling; Giommi, Paolo; Padovani, Paolo

    2016-01-01

    Aims. High Synchrotron Peaked blazars (HSPs) dominate the -ray sky at energies larger than a few GeV; however, only a few hundred blazars of this type have been catalogued so far. In this paper we present the 2WHSP sample, the largest and most complete list of HSP blazars available to date, which is an expansion of the 1WHSP catalog of gamma-ray source candidates off the Galactic plane. Methods. We cross-matched a number of multi-wavelength surveys (in the radio, infrared and X-ray bands) and applied selection criteria based on the radio to IR and IR to X-ray spectral slopes. To ensure the selection of genuine HSPs we examined the SED of each candidate and estimated the peak frequency of its synchrotron emission ($\

  11. Multi-Waveband Emission Maps of Blazars

    Indian Academy of Sciences (India)

    Alan Marscher; Svetlana G. Jorstad; Valeri M. Larionov; Margo F. Aller; Anne Lähteenmäki

    2011-03-01

    We are leading a comprehensive multi-waveband monitoring program of 34 -ray bright blazars designed to locate the emission regions of blazars from radio to -ray frequencies. The `maps’ are anchored by sequences of images in both total and polarized intensity obtained with the VLBA at an angular resolution of ∼ 0.1 milliarcseconds. The time-variable linear polarization at radio to optical wavelengths and radio to -ray light curves allow us to specify the locations of flares relative to bright stationary features seen in the images and to infer the geometry of the magnetic field in different regions of the jet. Our data reveal that some flares occur simultaneously at different wavebands and others are only seen at some of the frequencies. The flares are often triggered by a superluminal knot passing through the stationary `core’ on the VLBA images. Other flares occur upstream or even parsecs downstream of the core.

  12. Gravitational microlensing of gamma-ray blazars

    DEFF Research Database (Denmark)

    F. Torres, Diego; E. Romero, Gustavo; F. Eiroa, Ernesto;

    2003-01-01

    We present a detailed study of the effects of gravitational microlensing on compact and distant $\\gamma$-ray blazars. These objects have $\\gamma$-ray emitting regions which are small enough as to be affected by microlensing effects produced by stars lying in intermediate galaxies. We analyze...... the temporal evolution of the gamma-ray magnification for sources moving in a caustic pattern field, where the combined effects of thousands of stars are taken into account using a numerical technique. We propose that some of the unidentified $\\gamma$-ray sources (particularly some of those lying at high...... galactic latitude whose gamma-ray statistical properties are very similar to detected $\\gamma$-ray blazars) are indeed the result of gravitational lensing magnification of background undetected Active Galactic Nuclei (AGNs)....

  13. Astronomical Plate Archives and Binary Blazars Studies

    Indian Academy of Sciences (India)

    Rene Hudec

    2011-03-01

    There are about 3 million astronomical photographic plates around the globe, representing an important data source for various aspects of astrophysics. The main advantage is the large time coverage of 100 years or even more. Recent digitization efforts, together with the development of dedicated software, enables for the first time, effective data mining and data analyses by powerful computers with these archives. Examples of blazars proposed and/or investigated on the astronomical plates are presented and discussed.

  14. Blazar microvariability at hard X-rays

    OpenAIRE

    Foschini, L.; Gliozzi, M.; Pian, E.; Tagliaferri, G.; Tavecchio, F.; Bianchin, V.; L. Maraschi(INAF National Institute for Astrophysics, I-00136 Rome, Italy); Sambruna, R. M.; Di Cocco, G.; Ghisellini, G.; Malaguti, G.; Tosti, G.; Treves, A.

    2007-01-01

    Blazars are known to display strong and erratic variability at almost all the wavelengths of electromagnetic spectrum. Presently, variability studies at high-energies (hard X-rays, gamma-rays) are hampered by low sensitivity of the instruments. Nevertheless, the latest generation of satellites (INTEGRAL, Swift) have given suggestions not yet fully confirmed of variability on intraday timescales. Some specific cases recently observed are presented and physical implications are discussed (e.g. ...

  15. Ringo2 Optical Polarimetry of Blazars

    Directory of Open Access Journals (Sweden)

    Helen Jermak

    2016-10-01

    Full Text Available We present polarimetric and photometric observations from a sample of 15 γ-ray bright blazars with data from the Tuorla blazar monitoring program (KVA DIPOL and Liverpool Telescope (LT Ringo2 polarimeters (supplemented with γ-ray data from Fermi-LAT. We find that (1 The optical magnitude and γ-ray flux are positively correlated; (2 electric vector position angle rotations can occur in any blazar subclass; (3 there is no difference in the γ-ray flaring rates in the sample between subclasses; flares can occur during and outside of rotations with no preference for this behaviour; (4 the average degree of polarisation (P, optical magnitude and γ-ray flux are lower during a rotation compared with during non-rotation; (5 the number of observed flaring events and optical polarisation rotations are correlated and (6 the maximum observed P increases from ∼10% to ∼30% to ∼40% for subclasses with synchrotron peaks at high, intermediate and low frequencies respectively.

  16. Radio Band Observations of Blazar Variability

    Indian Academy of Sciences (India)

    Margo F. Aller; Hugh D. Aller; Philip A. Hughes

    2011-03-01

    The properties of blazar variability in the radio band are studied using the unique combination of temporal resolution from single dish monitoring and spatial resolution from VLBA imaging. Such measurements now available in all four Stokes parameters, together with theoretical simulations, identify the origin of radio band variability and probe the characteristics of the radio jet where the broadband blazar emission originates. Outbursts in total flux density and linear polarization in the optical-to-radio bands are attributed to shocks propagating within the jet spine, in part, based on limited modelling invoking transverse shocks; new radiative transfer simulations allowing for shocks at arbitrary angle to the flow direction confirm this picture by reproducing the observed centimeter-band variations observed more generally, and are of current interest since these shocks may play a role in the -ray flaring detected by Fermi. Recent UMRAO multifrequency Stokes V studies of bright blazars identify the spectral variability properties of circular polarization for the first time and demonstrate that polarity flips are relatively common. All-Stokes data are consistent with the production of circular polarization by linear-to-circular mode conversion in a region that is at least partially selfabsorbed. Detailed analysis of single-epoch, multifrequency, all-Stokes VLBA observations of 3C 279 support this physical picture and are best explained by emission from an electron-proton plasma.

  17. The Spectral Index Distribution of EGRET Blazars: Prospects for GLAST

    Energy Technology Data Exchange (ETDEWEB)

    Venters, Tonia M.; Pavlidou, Vasiliki; /SLAC

    2011-11-29

    The intrinsic distribution of spectral indices in GeV energies of gamma-ray-loud blazars is a critical input in determining the spectral shape of the unresolved blazar contribution to the diffuse extragalactic gamma-ray background, as well as an important test of blazar emission theories. We present a maximum-likelihood method of determining the intrinsic spectral index distribution (ISID) of a population of {gamma}-ray emitters which accounts for error in measurement of individual spectral indices, and we apply it to EGRET blazars. We find that the most likely Gaussian ISID for EGRET blazars has a mean of 2.27 and a standard deviation of 0.20. We additionally find some indication that FSRQs and BL Lacs may have different ISIDs (with BL Lacs being harder). We also test for spectral index hardening associated with blazar variability for which we find no evidence. Finally, we produce simulated GLAST spectral index datasets and perform the same analyses. With improved statistics due to the much larger number of resolvable blazars, GLAST data will help us determine the ISIDs with much improved accuracy. Should any difference exist between the ISIDs of BL Lacs and FSRQs or between the ISIDs of blazars in the quiescent and flaring states, GLAST data will be adequate to separate these ISIDs at a significance better than 3{sigma}.

  18. Gamma-Ray and Multiwavelength Emission from Blazars

    Indian Academy of Sciences (India)

    Meg Urry

    2011-03-01

    Blazars are now well understood as approaching relativistic jets aligned with the line of sight. The long-time uncertainty about the demographics of blazars is starting to become clearer: since the Fermi blazar sample includes a larger fraction of high-frequency peaked blazars (like the typical X-ray-selected blazars in, say, the Einstein Slew Survey sample) than did the higher-flux-limit EGRET blazar sample, these low-luminosity sources must be more common than their higher luminosity, low-frequency-peaked cousins. Blazar spectral energy distributions have a characteristic two-component form, with synchrotron radiation at radio through optical (UV, X-ray) frequencies and gamma-rays from X-ray through GeV (TeV) energies.Multiwavelength monitoring has suggested that gamma-ray flares can result from acceleration of electrons at shocks in the jet, and there appears to be an association between the creation of outflowing superluminal radio components in VLBI maps and the gamma-ray flares. In many cases, the gamma-ray emission is produced by inverse Compton upscattering of ambient optical-UV photons, although the contribution from energetic hadrons cannot be ruled out. The next few years of coordinated gamma-ray, X-ray, UV, optical, infrared and radio monitoring of blazars will be important for characterizing jet content, structure, and total power.

  19. Search for Extended {\\gamma}-ray Emission around AGN with H.E.S.S. and Fermi-LAT

    CERN Document Server

    Abramowski, A; Benkhali, F Ait; Akhperjanian, A G; Angüner, E; Anton, G; Backes, M; Balenderan, S; Balzer, A; Barnacka, A; Becherini, Y; Tjus, J Becker; Bernlöhr, K; Birsin, E; Bissaldi, E; Biteau, J; Böttcher, M; Boisson, C; Bolmont, J; Bordas, P; Brucker, J; Brun, F; Brun, P; Bulik, T; Carrigan, S; Casanova, S; Chadwick, P M; Chalme-Calvet, R; Chaves, R C G; Cheesebrough, A; Chrétien, M; Colafrancesco, S; Cologna, G; Conrad, J; Couturier, C; Cui, Y; Dalton, M; Daniel, M K; Davids, I D; Degrange, B; Deil, C; deWilt, P; Dickinson, H J; Djannati-Ataï, A; Domainko, W; Drury, L O'C; Dubus, G; Dutson, K; Dyks, J; Dyrda, M; Edwards, T; Egberts, K; Eger, P; Espigat, P; Farnier, C; Fegan, S; Feinstein, F; Fernandes, M V; Fernandez, D; Fiasson, A; Fontaine, G; Förster, A; Füßling, M; Gajdus, M; Gallant, Y A; Garrigoux, T; Giavitto, G; Giebels, B; Glicenstein, J F; Grondin, M -H; Grudzińska, M; Häffner, S; Hahn, J; Harris, J; Heinzelmann, G; Henri, G; Hermann, G; Hervet, O; Hillert, A; Hinton, J A; Hofmann, W; Hofverberg, P; Holler, M; Horns, D; Jacholkowska, A; Jahn, C; Jamrozy, M; Janiak, M; Jankowsky, F; Jung, I; Kastendieck, M A; Katarzyński, K; Katz, U; Kaufmann, S; Khélifi, B; Kieffer, M; Klepser, S; Klochkov, D; Kluźniak, W; Kneiske, T; Kolitzus, D; Komin, Nu; Kosack, K; Krakau, S; Krayzel, F; Krüger, P P; Laffon, H; Lamanna, G; Lefaucheur, J; Lemière, A; Lemoine-Goumard, M; Lenain, J -P; Lohse, T; Lopatin, A; Lu, C -C; Marandon, V; Marcowith, A; Marx, R; Maurin, G; Maxted, N; Mayer, M; McComb, T J L; Méhault, J; Meintjes, P J; Menzler, U; Meyer, M; Moderski, R; Mohamed, M; Moulin, E; Murach, T; Naumann, C L; de Naurois, M; Niemiec, J; Nolan, S J; Oakes, L; Odaka, H; Ohm, S; Wilhelmi, E de Oña; Opitz, B; Ostrowski, M; Oya, I; Panter, M; Parsons, R D; Arribas, M Paz; Pekeur, N W; Pelletier, G; Perez, J; Petrucci, P -O; Peyaud, B; Pita, S; Poon, H; Pühlhofer, G; Punch, M; Quirrenbach, A; Raab, S; Raue, M; Reichardt, I; Reimer, A; Reimer, O; Renaud, M; Reyes, R de los; Rieger, F; Rob, L; Romoli, C; Rosier-Lees, S; Rowell, G; Rudak, B; Rulten, C B; Sahakian, V; Sanchez, D A; Santangelo, A; Schlickeiser, R; Schüssler, F; Schulz, A; Schwanke, U; Schwarzburg, S; Schwemmer, S; Sol, H; Spengler, G; Spies, F; Stawarz, Ł; Steenkamp, R; Stegmann, C; Stinzing, F; Stycz, K; Sushch, I; Tavernet, J -P; Tavernier, T; Taylor, A M; Terrier, R; Tluczykont, M; Trichard, C; Valerius, K; van Eldik, C; van Soelen, B; Vasileiadis, G; Venter, C; Viana, A; Vincent, P; Völk, H J; Volpe, F; Vorster, M; Vuillaume, T; Wagner, S J; Wagner, P; Ward, M; Weidinger, M; Weitzel, Q; White, R; Wierzcholska, A; Willmann, P; Wörnlein, A; Wouters, D; Yang, R; Zabalza, V; Zacharias, M; Zdziarski, A A; Zech, A; Zechlin, H -S; Malyshev, D

    2014-01-01

    Context: Very-high-energy (VHE; E>100 GeV) {\\gamma}-ray emission from blazars inevitably gives rise to electron-positron pair production through the interaction of these {\\gamma}-rays with the Extragalactic Background Light (EBL). Depending on the magnetic fields in the proximity of the source, the cascade initiated from pair production can result in either an isotropic halo around an initially beamed source or a magnetically broadened cascade flux. Aims: Both extended pair halo (PH) and magnetically broadened cascade (MBC) emission from regions surrounding the blazars 1ES 1101-232, 1ES 0229+200 and PKS 2155-304 were searched for, using VHE {\\gamma}-ray data taken with the High Energy Stereoscopic System (H.E.S.S.), and high energy (HE; 100 MeV 10$^{-12}$G, this limits the production of pair halos developing from electromagnetic cascades. For weaker magnetic fields, in which electromagnetic cascades would result in magnetically broadened cascades, EGMF strengths in the range (0.3 - 3)$\\times 10^{-15}$G were e...

  20. A hadronic origin for ultra-high-frequency-peaked BL Lac objects

    CERN Document Server

    Cerruti, M; Boisson, C; Inoue, S

    2014-01-01

    Current Cherenkov telescopes have identified a population of ultra-high-frequency peaked BL Lac objects (UHBLs), also known as extreme blazars, that exhibit exceptionally hard TeV spectra, including 1ES 0229+200, 1ES 0347-121, RGB J0710+591, 1ES 1101-232, and 1ES 1218+304. Although one-zone synchrotron-self-Compton (SSC) models have been generally successful in interpreting the high-energy emission observed in other BL Lac objects, they are problematic for UHBLs, necessitating very large Doppler factors and/or extremely high minimum Lorentz factors of the emitting leptonic population. In this context, we have investigated alternative scenarios where hadronic emission processes are important, using a newly developed (lepto-)hadronic numerical code to systematically explore the physical parameters of the emission region that reproduces the observed spectra while avoiding the extreme values encountered in pure SSC models. Assuming a fixed Doppler factor $\\delta=30$, two principal parameter regimes are identified...

  1. A new highest historical X-ray State in 1ES 1959+650

    Science.gov (United States)

    Kapanadze, Bidzina; Dorner, Daniela; Kapanadze, Sergo

    2016-07-01

    The nearby HBL source 1ES 1959+650 (z=0.047) shows a prolonged strong X-ray flaring activity since 2016 May 6, observed by X-ray Telescope onboard the Swift satellite (Swift-XRT) mostly in the framework of our Target of Opportunity (ToO) requests of different urgencies (ToO Request Number: 8051, 8099, 8178, 8192, 8204, 8224, 8230, 8257, 8261).

  2. -Rays Radiation of High Redshift Fermi Blazars

    Indian Academy of Sciences (India)

    W. G. Liu; S. H. Fu; X. Zhang; L. Ma; Y. B. Li; D. R. Xiong

    2014-09-01

    Based on the 31 high redshift ( > 2) Flat Spectral Radio Quasars (FSRQs), which is from the second Fermi-LAT AGNs catalogue (2LAC), we studied the correlation between flux densities (R, K, ) in the radio, infrared and -ray wave bands. We found that there is a significant positive correlation between and R, and a weak anticorrelation between and K in the average state. For high redshift blazars, we argue that the seed photon of -ray emission mainly comes from the jet itself and partially from the dusty torus.

  3. Looking for High Energy Peaked Blazars

    OpenAIRE

    Costamante, L.; Ghisellini, G.; Celotti, A.; Giommi, P.; Padovani, P.; Tagliaferri, G.; Wolter, A.; Chiaberge, M.; Fossati, G; Pian, E.; L. Maraschi(INAF National Institute for Astrophysics, I-00136 Rome, Italy); Tavecchio, F.; Treves, A.

    2000-01-01

    Blazars can be classified on the basis of their overall Spectral Energy Distribution (SED). BL Lac objects are usually divided in LBL or HBL (Low or High energy peaked BL Lacs), according to the peak frequency of the synchrotron emission, if in the optical or UV-soft-X band respectively. FSRQs instead are characterized by synchrotron peaks mainly at IR-optical frequencies, similarly to LBLs. Here we report on recent BeppoSAX observations which are unveiling the high energy branch of the range...

  4. Correlation between -Ray and Radio Bands for -Ray Loud Blazars

    Indian Academy of Sciences (India)

    D. X. Wu; J. H. Fan; S. H. Li

    2014-09-01

    The most identified sources observed by Fermi are blazars (Flat Spectrum Radio Quasars (FSRQs) and BL Lacertae objects (BLs). In this paper, we obtained 124 -ray loud blazars with available -ray and radio (core and total) data. It is interesting that the -ray luminosity have a good correlation with the radio luminosity. This phenomenon exists in the core radio luminosity (c) and total radio luminosity (t). The correlation between the -ray and the radio luminosities is still stronger even after we eliminated the redshift effect, which suggests that the -ray radiations in the -ray loud blazars are strongly beamed.

  5. The Spectral Energy Distribution of Fermi bright blazars

    CERN Document Server

    Abdo, A A; Ajello, M; Axelsson, M; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Baughman, B M; Bechtol, K; Bellazzini, R; Berenji, B; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A; Bregeon, J; Brez, A; Brigida, M; Bruel, P; Burnett, T H; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Cavazzuti, E; Cecchi, C; Celik, O; Charles, E; Chaty, S; Chekhtman, A; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Colafrancesco, S; Cominsky, L R; Conrad, J; Costamante, L; Cutini, S; Dermer, C D; de Angelis, A; de Palma, F; Digel, S W; Silva, E do Couto e; Drell, P S; Dubois, R; Dumora, D; Farnier, C; Favuzzi, C; Fegan, S J; Focke, W B; Fortin, P; Frailis, M; Fuhrmann, L; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giebels, B; Giglietto, N; Giommi, P; Giordano, F; Glanzman, T; Godfrey, G; Grenier, I A; Grove, J E; Guillemot, L; Guiriec, S; Hadasch, D; Hanabata, Y; Harding, A K; Hayashida, M; Hays, E; Healey, S E; Horan, D; Hughes, R E; Itoh, R; Jackson, M S; Johannesson, G; Johnson, A S; Johnson, W N; Kadler, M; Kamae, T; Katagiri, H; Kataoka, J; Kawai, N; Kerr, M; Knodlseder, J; Kocian, M L; Kuss, M; Lande, J; Latronico, L; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Makeev, A; Max-Moerbeck, W; Mazziotta, M N; McConville, W; McEnery, J E; Meurer, C; Michelson, P F

    2009-01-01

    (Abridged) We have conducted a detailed investigation of the broad-band spectral properties of the \\gamma-ray selected blazars of the Fermi LAT Bright AGN Sample (LBAS). By combining our accurately estimated Fermi gamma-ray spectra with Swift, radio, infra-red, optical and other hard X-ray/gamma-ray data, collected within three months of the LBAS data taking period, we were able to assemble high-quality and quasi-simultaneous Spectral Energy Distributions (SED) for 48 LBAS blazars.The SED of these gamma-ray sources is similar to that of blazars discovered at other wavelengths, clearly showing, in the usual Log $\

  6. FACT. Flare alerts from blazar monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Dorner, Daniela [Universitaet Wuerzburg (Germany); Bretz, Thomas [RWTH Aachen (Germany); Collaboration: FACT-Collaboration

    2015-07-01

    One of the major goals of the First G-APD Cherenkov Telescope is the longterm monitoring of bright TeV blazars. For more than three years, FACT has observed the blazars Mrk 421 and Mrk 501 and a few other sources on a regular basis. To understand these highly variable objects, simultaneous data at different wavelengths are very useful. FACT is not only taking part in multi-wavelength campaigns, but also sending alerts to other instruments in case of enhanced flux, to study flares within the multi-wavelength frame. To send fast alerts, an automatic quick look analysis was set up on site. Once the data are written on disk, they are automatically processed, and the analysis results are published on a website where other observers can monitor the activity of the source in the very high energy band. In addition, alerts are sent in case the flux is higher than a certain predefined value. In 2014, more than five alerts have been sent. Results from three years of monitoring are presented.

  7. Central black hole mass determination for blazars

    Institute of Scientific and Technical Information of China (English)

    Yuan Yu-Hai; Fan Jun-Hui; Huang Yong

    2008-01-01

    In this paper, we use a method to determine some basic parameters for the (r)-ray loud blazars. The parameters include the central black mass (M), the boosting factor (δ), the propagation angle (φ), the distance along the axis to the site of the (r)-ray production (d). A sample including 32 (r)-ray loud blazars with available variability time scaleshas been used to discuss the above properties. In this method, the (r)-ray energy, the emission size and the property of the accretion disc determine the absorption effect. If we take the intrinsic(γ)-ray luminosity to be λ Times the Eddington luminosity, I.e. Lin(r) =λLedd, then we have the following results: the mass of the black hole is in the range of (0.59 - 67.99) ⊙ (λ= 1.0) or (0.90 - 104.13) ⊙ (λ = 0.1); the boosting factor (δ) in the range of 0.16 - 2.09(λ=1.0) or 0.24 - 2.86 (λ=0.1); the angle (φ) in the range of 9.53 (λ =1.0) or 7.36°=0.1); and the distance (d/Rg) in the range of 22.39 - 609.36 (λ= 1.0) or 17.54 - 541.88 (λ = 0.1).

  8. Superluminal Motion and Polarization in Blazars

    Institute of Scientific and Technical Information of China (English)

    Jun-Hui Fan; Yong-Jiu Wang; Jiang-He Yang; Cheng-Yue Su

    2004-01-01

    A relativistic beaming model has been successfully used to explain the observed properties of active galactic nuclei (AGNs). In this model there are two emission components, a boosted one and an unbeamed one, shown up in the radio band as the core and lobe components. The luminosity ratio of the core to the lobe is defined as the core-dominance parameter (R = LCore/LLobe) The de-beamed radio luminosity (Ldbjet) in the jet is assumed to be proportional to the unbeamed luminosity (Lub) in the co-moving frame, i.e., f = Ldbjet/Lub and f is determined in our previous paper. We further discuss the relationship between BL Lacertae objects(BLs) and flat spectrum radio quasars (FSRQs), which are subclasses of blazars with different degrees of polarization, using the calculated values of the ratio f for a sample of superluminal blazars. We found 1) that the BLs show smaller averaged Doppler factors and Lorentz factors, larger viewing angles and higher coredominance parameters than do the FSRQs, and 2) that in the polarization-core dominance parameter plot (P - log R) the BLs and FSRQs occupy a scattered region, but in a revised plot (logP/c(m) - logR), they gather around two different lines, suggesting that they have some different intrinsic properties.

  9. Detecting the Elusive Blazar Counter-Jets

    CERN Document Server

    Liodakis, I; Angelakis, E

    2016-01-01

    Detection of blazar pc scale counter-jets is difficult, but it can provide invaluable insight into the relativistic effects, radiative processes and the complex mechanisms of jet production, collimation and accelation in blazars. We build on recent populations models (optimized using the MOJAVE apparent velocity and redshift distributions) in order to derive the distribution of jet-to-counter-jet ratios and the flux densities of the counter-jet at different frequencies, in an effort to set minimum sensitivity limits required for existing and future telescope arrays in order to detect these elusive counter-jets. We find that: for the BL Lacs $5\\%$ of their counter-jets have a flux-density higher than 100mJy, $15\\%$ are higher than 10 mJy, and $32\\%$ have higher flux-density than 1 mJy, whereas for the FSRQs $8\\%$ have a flux-density higher than 10mJy, $17\\%$ are higher than 1 mJy, and $32\\%$ are higher than 0.1 mJy (at 15 GHz). Future telescopes like the SKA and newly operating like e-MERLIN and JVLA may detec...

  10. The blazar paradigm and its discontents

    CERN Document Server

    Dermer, C D

    2014-01-01

    The standard blazar paradigm consists of a supermassive black hole that expels relativistic jets of magnetized plasma in our direction. This plasma entrains nonthermal synchrotron-emitting electrons that furthermore scatter internally-produced synchrotron photons as well as externally-produced photons from the accretion-disk, the broad-line region, and the infrared-emitting torus. This picture has been very successful in reproducing the two-humped blazar spectral energy distribution. Yet various discontents persist, including (1) ultra-short variability at TeV energies that is much shorter than the black hole's dynamical timescale; (2) very-high energy (VHE; >100 GeV) radiation from FSRQs; (3) evidence for a hard spectral component in high-synchrotron peaked objects, found when deabsorbing the measured VHE spectrum using conventional extragalactic background light (EBL) models; (4) an unusual slowly varying class of BL Lac objects; (5) location of the gamma-ray emission region. Some of these problems can be r...

  11. FACT. Flare alerts from blazar monitoring

    International Nuclear Information System (INIS)

    One of the major goals of the First G-APD Cherenkov Telescope is the longterm monitoring of bright TeV blazars. For more than three years, FACT has observed the blazars Mrk 421 and Mrk 501 and a few other sources on a regular basis. To understand these highly variable objects, simultaneous data at different wavelengths are very useful. FACT is not only taking part in multi-wavelength campaigns, but also sending alerts to other instruments in case of enhanced flux, to study flares within the multi-wavelength frame. To send fast alerts, an automatic quick look analysis was set up on site. Once the data are written on disk, they are automatically processed, and the analysis results are published on a website where other observers can monitor the activity of the source in the very high energy band. In addition, alerts are sent in case the flux is higher than a certain predefined value. In 2014, more than five alerts have been sent. Results from three years of monitoring are presented.

  12. INVESTIGATING BROADBAND VARIABILITY OF THE TeV BLAZAR 1ES 1959+650

    Energy Technology Data Exchange (ETDEWEB)

    Aliu, E. [Department of Physics and Astronomy, Barnard College, Columbia University, NY 10027 (United States); Archambault, S. [Physics Department, McGill University, Montreal, QC H3A 2T8 (Canada); Arlen, T.; Aune, T. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States); Barnacka, A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Beilicke, M.; Buckley, J. H.; Bugaev, V. [Department of Physics, Washington University, St. Louis, MO 63130 (United States); Benbow, W.; Cerruti, M. [Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645 (United States); Berger, K. [Department of Physics and Astronomy and the Bartol Research Institute, University of Delaware, Newark, DE 19716 (United States); Bird, R.; Collins-Hughes, E. [School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland); Bouvier, A. [Santa Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz, CA 95064 (United States); Chen, X. [Institute of Physics and Astronomy, University of Potsdam, D-14476 Potsdam-Golm (Germany); Ciupik, L. [Astronomy Department, Adler Planetarium and Astronomy Museum, Chicago, IL 60605 (United States); Connolly, M. P. [School of Physics, National University of Ireland Galway, University Road, Galway (Ireland); Cui, W. [Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907 (United States); Dumm, J. [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States); Eisch, J. D., E-mail: amy.furniss@gmail.com, E-mail: Markus.Bottcher@nwu.ac.za [Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States); Collaboration: VERITAS Collaboration; and others

    2014-12-20

    We summarize broadband observations of the TeV-emitting blazar 1ES 1959+650, including optical R-band observations by the robotic telescopes Super-LOTIS and iTelescope, UV observations by Swift Ultraviolet and Optical Telescope, X-ray observations by the Swift X-ray Telescope, high-energy gamma-ray observations with the Fermi Large Area Telescope, and very-high-energy (VHE) gamma-ray observations by VERITAS above 315 GeV, all taken between 2012 April 17 and 2012 June 1 (MJD 56034 and 56079). The contemporaneous variability of the broadband spectral energy distribution is explored in the context of a simple synchrotron self Compton (SSC) model. In the SSC emission scenario, we find that the parameters required to represent the high state are significantly different than those in the low state. Motivated by possible evidence of gas in the vicinity of the blazar, we also investigate a reflected emission model to describe the observed variability pattern. This model assumes that the non-thermal emission from the jet is reflected by a nearby cloud of gas, allowing the reflected emission to re-enter the blob and produce an elevated gamma-ray state with no simultaneous elevated synchrotron flux. The model applied here, although not required to explain the observed variability pattern, represents one possible scenario which can describe the observations. As applied to an elevated VHE state of 66% of the Crab Nebula flux, observed on a single night during the observation period, the reflected emission scenario does not support a purely leptonic non-thermal emission mechanism. The reflected emission model does, however, predict a reflected photon field with sufficient energy to enable elevated gamma-ray emission via pion production with protons of energies between 10 and 100 TeV.

  13. Discovery of VHE gamma-rays from the distant BL Lac 1ES 0347-121

    CERN Document Server

    Aharonian, F; Barres de Almeida, U; Bazer-Bachi, A R; Behera, B; Beilicke, M; Benbow, W; Bernlöhr, K; Boisson, C; Bolz, O; Borrel, V; Braun, I; Brion, E; Brown, A M; Buhler, R; Bulik, T; Büsching, I; Boutelier, T; Carrigan, S; Chadwick, P M; Chounet, L M; Clapson, A C; Coignet, G; Cornils, R; Costamante, L; Dalton, M; Degrange, B; Dickinson, H J; Djannati-Ata:, A; Domainko, W; O'Connor-Drury, L; Dubois, F; Dubus, G; Dyks, J; Egberts, K; Emmanoulopoulos, D; Espigat, P; Farnier, C; Feinstein, F; Fiasson, A; Förster, A; Fontaine, G; Funk, Seb; Fuling, M; Gallant, Y A; Giebels, B; Glicenstein, J F; Glück, B; Goret, P; Hadjichristidis, C; Hauser, D; Hauser, M; Heinzelmann, G; Henri, G; Hermann, G; Hinton, J A; Hoffmann, A; Hofmann, W; Holleran, M; Hoppe, S; Horns, D; Jacholkowska, A; De Jager, O C; Jung, I; Katarzynski, K; Kendziorra, E; Kerschhaggl, M; Khelifi, B; Keogh, D; Komin, Nu; Kosack, K; Lamanna, G; Latham, I J; Lemiere, A; Lemoine-Goumard, M; Lenain, J P; Lohse, T; Martin, J M; Martineau-Huynh, O; Marcowith, A; Masterson, C; Maurin, D; Maurin, G; McComb, T J L; Moderski, R; Moulin, E; De Naurois, Mathieu; Nedbal, D; Nolan, S J; Ohm, S; Olive, J P; De Ona Wilhelmi, E; Orford, K J; Osborne, J L; Ostrowski, M; Panter, M; Pedaletti, G; Pelletier, G; Petrucci, P O; Pita, S; Pühlhofer, G; Punch, M; Ranchon, S; Raubenheimer, B C; Raue, M; Rayner, S M; Renaud, M; Ripken, J; Rob, L; Rolland, L; Rosier-Lees, S; Rowell, G; Rudak, B; Ruppel, J; Sahakian, V V; Santangelo, A; Schlickeiser, R; Schock, F; Schroder, R; Schwanke, U; Schwarzburg, S; Schwemmer, S; Shalchi, A; Sol, H; Spangler, D; Stawarz,; Steenkamp, R; Stegmann, C; Superina, G; Tam, P H; Tavernet, J P; Terrier, R; Van Eldik, C; Vasileiadis, G; Venter, C; Vialle, J P; Vincent, P; Vivier, M; Völk, H J; Volpe, F; Wagner, S J; Ward, M; Zdziarski, A A; Zech, A

    2007-01-01

    Aims: Our aim is to study the production mechanism for very-high-energy (VHE; >100GeV) gamma-rays in distant active galactic nuclei (AGN) and use the observed VHE spectrum to derive limits on the Extragalactic Background Light (EBL). We also want to determine physical quantities through the modeling of the object's broad-band spectral energy distribution (SED). Methods: VHE observations (~25h live time) of the BL Lac 1ES 0347-121 (redshift z=0.188) were conducted with the High Energy Stereoscopic System (H.E.S.S.) between August and December 2006. Contemporaneous X-ray and UV/optical observations from the SWIFT satellite are used to interpret the SED of the source in terms of a synchrotron self Compton (SSC) model. Results: An excess of 327 events, corresponding to a statistical significance of 10.1 standard deviations, is detected from 1ES 0347-121. Its photon spectrum, ranging from ~250GeV to ~3TeV, is well described by a power law with a photon index of Gamma = 3.10 +/- 0.23_stat +/- 0.10_sys. The integral...

  14. Six-year Optical Monitoring of BL Lacertae Object 1ES 0806+52.4

    CERN Document Server

    Man, Zhongyi; Wu, Jianghua; Zhou, Xu; Yuan, Qirong

    2014-01-01

    We present the results of the first systematic long-term multi-color optical monitoring of the BL Lacertae object 1ES 0806+52.4. The monitoring was performed in multiple passbands with a 60/90 cm Schmidt telescope from December 2005 to February 2011. The overall brightness of this object decreased from 2005 December to 2008 December, and regained after that. A sharp outburst probably occurred around the end of our monitoring program. Overlapped on the long-term trend are some short-term small-amplitude oscillations. No intra-night variability was found in the object, which is in accord with the historical observations before 2005. By investigating the color behavior, we found strong bluer-when-brighter chromatism for the long-term variability of 1ES 0806+52.4. The total amplitudes at the c, i and o bands are 1.18, 1.12, and 1.02 mags, respectively. The amplitudes tend to increase toward shorter wavelength, which may be the major cause of bluer-when-brighter. Such bluer-when-brighter is also found in other bla...

  15. VERITAS observations of the BL Lac 1ES 1218+304

    CERN Document Server

    Acciari, V A; Arlen, T; Beilicke, M; Benbow, W; Bradbury, S M; Buckley, J H; Bugaev, V; Butt, Y; Byrum, K L; Celik, O; Cesarini, A; Ciupik, L; Chow, Y C K; Cogan, P; Colin, P; Cui, W; Daniel, M K; Ergin, T; Falcone, A D; Fegan, S J; Finley, J P; Fortin, P; Fortson, L F; Furniss, A; Gillanders, G H; Grube, J; Guenette, R; Gyuk, G; Hanna, D; Hays, E; Holder, J; Horan, D; Hui, C M; Humensky, T B; Imran, A; Kaaret, Philip; Karlsson, N; Kertzman, M; Kieda, D B; Kildea, J; Konopelko, A; Krawczynski, H; Krennrich, F; Lang, M J; Le Bohec, S; Maier, G; McCann, A; McCutcheon, M; Moriarty, P; Mukherjee, R; Nagai, T; Niemiec, J; Ong, R A; Pandel, D; Perkins, J S; Pohl, M; Quinn, J; Ragan, K; Reyes, L C; Reynolds, P T; Rose, H J; Schroedter, M; Sembroski, G H; Smith, A W; Steele, D; Swordy, S P; Toner, J A; Valcarcel, L; Vasilev, V V; Wagner, R; Wakely, S P; Ward, J E; Weekes, T C; Weinstein, A; White, R J; Williams, D A; Wissel, S A; Wood, M; Zitzer, B

    2009-01-01

    The VERITAS collaboration reports the detection of very-high-energy (VHE) gamma-ray emission from the high-frequency-peaked BL Lac object 1ES 1218+304 located at a redshift of z=0.182. A gamma-ray signal was detected with a statistical significance of 10.4 standard deviations (10.4 sigma) for the observations taken during the first three months of 2007, confirming the discovery of this object made by the MAGIC collaboration. The photon spectrum between ~160 GeV and ~1.8 TeV is well described by a power law with an index of Gamma = 3.08 +/- 0.34_stat +/- 0.2_sys. The integral flux is Phi(E > 200 GeV) = (12.2 +/- 2.6) X 10^-12 cm^-2 s^-1, which corresponds to ~6% of that of the Crab Nebula. The light curve does not show any evidence for VHE flux variability. Using lower limits on the density of the extragalactic background light in the near to mid-infrared we are able to limit the range of intrinsic energy spectra for 1ES 1218+304. We show that the intrinsic photon spectrum has an index that is harder than Gamm...

  16. Blazar flares powered by plasmoids in relativistic reconnection

    CERN Document Server

    Petropoulou, Maria; Sironi, Lorenzo

    2016-01-01

    Powerful flares from blazars with short ($\\sim$ min) variability timescales are challenging for current models of blazar emission. Here, we present a physically motivated ab initio model for blazar flares based on the results of recent particle-in-cell (PIC) simulations of relativistic magnetic reconnection. PIC simulations demonstrate that quasi-spherical plasmoids filled with high-energy particles and magnetic fields are a self-consistent by-product of the reconnection process. By coupling our PIC-based results (i.e., plasmoid growth, acceleration profile, particle and magnetic content) with a kinetic equation for the evolution of the electron distribution function we demonstrate that relativistic reconnection in blazar jets can produce powerful flares whose temporal and spectral properties are consistent with the observations. In particular, our model predicts correlated synchrotron and synchrotron self-Compton flares of duration of several hours--days powered by the largest and slowest moving plasmoids th...

  17. Cosmic ray loading and PeV neutrino production in blazars

    CERN Document Server

    Zhang, B Theodore

    2016-01-01

    IceCube has reported the detection of PeV neutrinos, for which blazars are strong candidate sources. The stacking search of neutrinos for known individual blazars by IceCube, however, puts stringent upper limit to their neutrino flux. Here using the upper limit we constrain the cosmic ray loading factor in blazars, i.e., the ratio of the cosmic ray to bolometric radiation luminosity of blazar jets is $\\xi_{\\rm cr}\\la2$ for flat cosmic ray spectrum. Combined with the blazar density measured by Fermi-LAT, we compute the limit to the diffuse PeV neutrino flux produced by all-sky blazars, and find that blazars, dominated by flat spectrum radio quasars, can only contribute a fraction $\\la10\\%$ of the IceCube detected diffuse PeV neutrino flux. Thus blazars can hardly be the sources of the bulk PeV neutrinos.

  18. Photohadronic scenario in interpreting the February-March 2014 flare of 1ES 1011+496

    CERN Document Server

    Sahu, Sarira; Miranda, Luis Salvador

    2016-01-01

    The extraordinary multi-TeV flare from 1ES 1011 +496 during February-March 2014 was observed by MAGIC telescopes for 17 nights and the average spectrum of the whole period has a non-trivial shape. We have used the photohadronic model and a template EBL model to explain the average spectrum which fits well to the flare data. The spectral index $\\alpha$ is the only free parameter in our model. We have also shown that the non-trivial nature of the spectrum is due to the change in the behavior of the optical depth above $\\sim 600$ GeV $\\gamma$-ray energy accompanied with the high SSC flux.

  19. Multi-waveband Behavior of Blazars

    Directory of Open Access Journals (Sweden)

    Marscher Alan P.

    2013-12-01

    Full Text Available The author reviews recent progress toward understanding blazars that multi-waveband monitoring observations have advanced. The primary techniques include the compilation of multi-waveband light curves, multi-epoch VLBI images at radio wavelengths, plots of linear polarization vs. time at radio through optical wavelengths, and spectral energy distributions (SEDs. Correlations and the coincidence or lag of events across wavebands and in the images indicate where the events take place relative to the “core” that lies ≳ 0.5 pc from the central engine. Rotations of the polarization electric vector suggest a helical geometry of the magnetic field upstream of the millimeter-wave core, while rapid fluctuations in degree and position angle of polarization imply that the jet plasma is turbulent in and downstream of the core. The author is developing a numerical model that simulates the emission from such turbulence as it interacts with a conical standing shock in the core region.

  20. Cyclotron Maser Emission from Blazar Jets?

    CERN Document Server

    Begelman, M C; Rees, Martin J; Begelman, Mitchell C.; Ergun, Robert E.; Rees, Martin J.

    2005-01-01

    We consider the production of electron cyclotron maser emission by low-density, highly magnetized plasmas in relativistic jets. The population inversion required to drive cyclotron maser instability could occur in localized, transient sites where hydromagnetic instabilities, shocks, and/or turbulence lead to magnetic mirroring along current-carrying flux tubes. The maser is pumped as electrons are accelerated by the parallel electric field that develops as a result of the mirror. We estimate the maximum brightness temperatures that can be obtained in a single maser site and in an array of many masers operating simultaneously, under conditions likely to apply in blazar jets. Synchrotron absorption, by relativistic electrons within the jet, presents the largest obstacle to the escape of the maser radiation, and may render most of it invisible. However, we argue that a high brightness temperature could be produced in a thin boundary layer outside the synchrotron photosphere, perhaps in the shear layer along the ...

  1. BLAZAR MONITORING WITH THE WATCHER ROBOTIC TELESCOPE

    Directory of Open Access Journals (Sweden)

    Pete Tisdall

    2014-01-01

    Full Text Available Presentamos informaci ́on sobre una intensa campa ̃na de obs ervaciones de blazars de rayos gamma en el ́optico que estamos llevando a cabo capaz de observar variabilidad ́ optica de corta y larga duraci ́on para fuentes del hemisferio sur. Diez fuentes est ́an siendo observadas dent ro de este programa con ́enfasis en PKS 2155-304 y PKS 2005-489 durante el invierno austral de 2013. Ambas fuen tes fueron observadas con 3 filtros (V, R e I obteniendo alrededor de 20,000 im ́agenes durante un period o de 5 meses. Un an ́alisis preliminar parcial de los datos indica que no hubo episodios de gran actividad en la ban da ́optica.

  2. The line emissions and polarization in blazars

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The correlations between broad-line emission,polarization,and core-dominance parameters are investigated for a sample of 148 blazars(BL Lacertae objects-BLs and flat spectrum radio quasars-FSRQs). An anti-correlation between the broad-line luminosity and the linear polarization is found. The broad-line and polarization relation can be explained by using a relativistic beaming model,which perhaps suggests that BL Lacs and FSRQs are a single class. We also investigated the relation between the ratio of the broad-line luminosity to the Eddington luminosity and linear polarization,and that between the ratio of the broad-line luminosity to the Eddington luminosity and the core-dominance parameter.

  3. FACT - Monitoring Blazars at Very High Energies

    CERN Document Server

    Dorner, D; Bergmann, M; Biland, A; Balbo, M; Bretz, T; Buss, J; Einecke, S; Freiwald, J; Hempfling, C; Hildebrand, D; Hughes, G; Lustermann, W; Mannheim, K; Meier, K; Mueller, S; Neise, D; Neronov, A; Overkemping, A -K; Paravac, A; Pauss, F; Rhode, W; Steinbring, T; Temme, F; Thaele, J; Toscano, S; Vogler, P; Walter, R; Wilbert, A

    2015-01-01

    The First G-APD Cherenkov Telescope (FACT) was built on the Canary Island of La Palma in October 2011 as a proof of principle for silicon based photosensors in Cherenkov Astronomy. The scientific goal of the project is to study the variability of active galatic nuclei (AGN) at TeV energies. Observing a small sample of TeV blazars whenever possible, an unbiased data sample is collected. This allows to study the variability of the selected objects on timescales from hours to years. Results from the first three years of monitoring will be presented. To provide quick flare alerts to the community and trigger multi-wavelength observations, a quick look analysis has been installed on-site providing results publicly online within the same night. In summer 2014, several flare alerts were issued. Results of the quick look analysis are summarized.

  4. The hard synchrotron X-ray spectrum of the TeV BL Lac 1ES 1426+428

    CERN Document Server

    Wolter, A; Ghisellini, G; Tavecchio, F; Maraschi, L; Costamante, L; Celotti, A; Ghirlanda, G

    2007-01-01

    We have observed 1ES 1426+428 with INTEGRAL detecting it up to $\\sim$150 keV. The spectrum is hard, confirming that this source is an extreme BL Lac object, with a synchrotron component peaking, in a $\

  5. CHANDRA VIEW OF THE WARM-HOT INTERGALACTIC MEDIUM TOWARD 1ES 1553+113: ABSORPTION-LINE DETECTIONS AND IDENTIFICATIONS. I

    Energy Technology Data Exchange (ETDEWEB)

    Nicastro, F.; Zappacosta, L. [Osservatorio Astronomico di Roma-INAF, Via di Frascati 33, I-00040 Monte Porzio Catone, RM (Italy); Elvis, M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., MS-04, Cambridge, MA 02138 (United States); Krongold, Y. [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Mexico City Mexico (Mexico); Mathur, S.; Gupta, A. [Ohio State University, Columbus, OH (United States); Danforth, C.; Shull, J. M. [CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, 389-UCB, Boulder, CO 80309 (United States); Barcons, X. [Instituto de Fisica de Cantabria (CSIC-UC), E-39005 Santander (Spain); Borgani, S. [Dipartimento di Astronomia dell' Universita di Trieste, Via G.B. Tiepolo 11, I-34131 Trieste (Italy); Branchini, E. [Dipartimento di Fisica ' ' E. Amaldi' ' , Universita degli Studi ' ' Roma Tre' ' , via della Vasca Navale 84, I-00146 Roma (Italy); Cen, R. [Princeton University Observatory, Princeton, NJ 08544 (United States); Dave, R. [Astronomy Department, University of Arizona, Tucson, AZ 85721 (United States); Kaastra, J. [SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA, Utrecht (Netherlands); Paerels, F. [Columbia Astrophysics Laboratory and Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Piro, L. [INAF-IAPS, Via del Fosso del Cavaliere 100, I-00133 Roma (Italy); Takei, Y. [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)

    2013-06-01

    We present the first results from our pilot 500 ks Chandra Low Energy Transmission Grating Large Program observation of the soft X-ray brightest source in the z {approx}> 0.4 sky, the blazar 1ES 1553+113, aimed to secure the first uncontroversial detections of the missing baryons in the X-rays. We identify a total of 11 possible absorption lines, with single-line statistical significances between 2.2{sigma} and 4.1{sigma}. Six of these lines are detected at high single-line statistical significance (3.6 {<=} {sigma} {<=} 4.1), while the remaining five are regarded as marginal detections in association with either other X-ray lines detected at higher significance and/or far-ultraviolet (FUV) signposts. Three of these lines are consistent with metal absorption at z {approx_equal} 0, and we identify them with Galactic O I and C II. The remaining eight lines may be imprinted by intervening absorbers and are all consistent with being high-ionization counterparts of FUV H I and/or O VI intergalactic medium signposts. In particular, five of these eight possible intervening absorption lines (single-line statistical significances of 4.1{sigma}, 4.1{sigma}, 3.9{sigma}, 3.8{sigma}, and 2.7{sigma}), are identified as C V and C VI K{alpha} absorbers belonging to three WHIM systems at z{sub X} = 0.312, z{sub X} = 0.237, and (z{sub X} ) = 0.133, which also produce broad H I (and O VI for the z{sub X} = 0.312 system) absorption in the FUV. For two of these systems (z{sub X} = 0.312 and 0.237), the Chandra X-ray data led the a posteriori discovery of physically consistent broad H I associations in the FUV (for the third system the opposite applies), so confirming the power of the X-ray-FUV synergy for WHIM studies. The true statistical significances of these three X-ray absorption systems, after properly accounting for the number of redshift trials, are 5.8{sigma} (z{sub X} = 0.312; 6.3{sigma} if the low-significance O V and C V K{beta} associations are considered), 3.9{sigma} (z

  6. Chandra View of the Warm-hot Intergalactic Medium toward 1ES 1553+113: Absorption-line Detections and Identifications. I.

    Science.gov (United States)

    Nicastro, F.; Elvis, M.; Krongold, Y.; Mathur, S.; Gupta, A.; Danforth, C.; Barcons, X.; Borgani, S.; Branchini, E.; Cen, R.; Davé, R.; Kaastra, J.; Paerels, F.; Piro, L.; Shull, J. M.; Takei, Y.; Zappacosta, L.

    2013-06-01

    We present the first results from our pilot 500 ks Chandra Low Energy Transmission Grating Large Program observation of the soft X-ray brightest source in the z >~ 0.4 sky, the blazar 1ES 1553+113, aimed to secure the first uncontroversial detections of the missing baryons in the X-rays. We identify a total of 11 possible absorption lines, with single-line statistical significances between 2.2σ and 4.1σ. Six of these lines are detected at high single-line statistical significance (3.6 X-ray lines detected at higher significance and/or far-ultraviolet (FUV) signposts. Three of these lines are consistent with metal absorption at z ~= 0, and we identify them with Galactic O I and C II. The remaining eight lines may be imprinted by intervening absorbers and are all consistent with being high-ionization counterparts of FUV H I and/or O VI intergalactic medium signposts. In particular, five of these eight possible intervening absorption lines (single-line statistical significances of 4.1σ, 4.1σ, 3.9σ, 3.8σ, and 2.7σ), are identified as C V and C VI Kα absorbers belonging to three WHIM systems at zX = 0.312, zX = 0.237, and langzX rang = 0.133, which also produce broad H I (and O VI for the zX = 0.312 system) absorption in the FUV. For two of these systems (zX = 0.312 and 0.237), the Chandra X-ray data led the a posteriori discovery of physically consistent broad H I associations in the FUV (for the third system the opposite applies), so confirming the power of the X-ray-FUV synergy for WHIM studies. The true statistical significances of these three X-ray absorption systems, after properly accounting for the number of redshift trials, are 5.8σ (zX = 0.312; 6.3σ if the low-significance O V and C V Kβ associations are considered), 3.9σ (zX = 0.237), and 3.8σ (langzX rang = 0.133), respectively.

  7. Analysis of the activity of the blazar BL Lacertae over the period 1998-2011

    Science.gov (United States)

    Strigunov, K. S.; Zhovtan, A. V.

    2016-07-01

    In 1998-2011 the blazar (active galactic nucleus) BL Lacertae was observed at Crimean Astrophysical Observatory (CrAO) with the second-generation GT-48 Cherenkov telescope at energies >1 TeV with a total significance of 11.8σ. More than 20 flares and a fourfold change in yearly mean fluxes (>1 TeV) were recorded. The optical ( B band) data obtained at CrAO and the TeV data are shown to correlate in some time intervals. The optical data are also compared with the X-ray RXTE/ASM (2-10 keV) data. In addition, the data from GT-48 are compared with the gamma-ray fluxes recorded by the Fermi LAT space telescope (0.1-300 GeV). The 2009 flare at TeV and Fermi energies has been studied. As a result, it has been found that as the activity rises the increase in flux at high energies exceeds its increase at low energies. This conclusion may be related to the conversion mechanism of particle acceleration. This is consistent with the results of studies for a similar object, 1ES 1426+428.

  8. Features of a knowledge based system REPSA1ES for probabilistic safety analysis

    International Nuclear Information System (INIS)

    This paper addresses the description of features of a knowledge based system REPSA1ES (Reliability Evaluation and Probabilistic Safety Analysis - level 1 - Expert System). The prototype software system has been designed for facilitating the probabilistic safety analysis (PSA) of complex hazardous industrial systems and to support the safety oriented decision making, during the design phase and operation of process systems. Taking into account known difficulties to manage complexity of logical and probabilistic modelling of nuclear power plants using the conventional PSA software packages we decided to represent information in a graphical form, whenever it is justified, and to automate the process of coding of objects to avoid errors. The software system consists of CAD modules, data bases, a shell for building expert systems and several other modules to enable: the effective communication with the user, data and knowledge acquisition, the initiation of inferring to support logical modelling of safety oriented systems, selection of reliability models with input parameters as well as the quantitative probabilistic evaluation of accident sequences. Due to the fact that the modelling and assessment process in PSA including the human reliability analysis (HRA) is complex and iterative, and can be automated only in some of its parts, it was assumed that the user can build the logic models himself or modify, in permissible cases, the event and fault trees created by relevant modules of the expert system. (author). 46 refs, 9 figs

  9. Multiwavelength observations and modeling of 1ES 1959+650 in a low flux state

    CERN Document Server

    Aliu, E; Arlen, T; Aune, T; Beilicke, M; Benbow, W; Bird, R; Boettcher, M; Bouvier, A; Bugaev, V; Byrum, K; Cesarini, A; Ciupik, L; Collins-Hughes, E; Connolly, M P; Cui, W; Dickherber, R; Duke, C; Dumm, J; Errando, M; Falcone, A; Federici, S; Feng, Q; Finley, J P; Finnegan, G; Fortson, L; Furniss, A; Galante, N; Gall, D; Gillanders, G H; Griffin, S; Grube, J; Gyuk, G; Hanna, D; Holder, J; Hughes, G; Humensky, T B; Kaaret, P; Kertzman, M; Khassen, Y; Kieda, D; Krawczynski, H; Krennrick, F; Lang, M J; Madhavan, A S; Maier, G; Majumdar, P; McArthur, S; McCann, A; Moriarty, P; Mukherjee, R; Nelson, T; de Bhroithe, A O'Faolain; Ong, R A; Orr, M; Otte, A N; Park, N; Perkins, J S; Pichel, A; Pohl, M; Popkow, A; Prokoph, H; Quinn, J; Ragan, K; Reyes, L C; Reynolds, P T; Roache, E; Saxon, D B; Schroedter, M; Sembroski, G H; Skole, C; Smith, A W; Staszak, D; Telezhinsky, I; Theiling, M; Tyler, J; Varlotta, A; Vassiliev, V V; Wakely, S P; Weekes, T C; Weinstein, A; Welsing, R; Williams, D A; Zitzer, B

    2013-01-01

    We report on the VERITAS observations of the high-frequency peaked BL Lac object 1ES 1959+650 in the period 2007-2011. This source is detected at TeV energies by VERITAS at 16.4 standard deviation (sigma) significance in 7.6 hours of observation in a low flux state. A multiwavelength spectral energy distribution (SED) is constructed from contemporaneous data from VERITAS, Fermi-LAT, RXTE PCA, and Swift UVOT. Swift XRT data is not included in the SED due to a lack of simultaneous observations with VERITAS. In contrast to the orphan gamma-ray flare exhibited by this source in 2002, the X-ray flux of the source is found to vary by an order of magnitude, while other energy regimes exhibit less variable emission. A quasi-equilibrium synchrotron self-Compton model with an additional external radiation field is used to describe three SEDs corresponding to the lowest, highest, and average X-ray states. The variation in the X-ray spectrum is modeled by changing the electron injection spectral index, with minor adjustm...

  10. Broadband Observations of High Redshift Blazars

    Science.gov (United States)

    Paliya, Vaidehi S.; Parker, M. L.; Fabian, A. C.; Stalin, C. S.

    2016-07-01

    We present a multi-wavelength study of four high redshift blazars, S5 0014+81 (z = 3.37), CGRaBS J0225+1846 (z = 2.69), BZQ J1430+4205 (z = 4.72), and 3FGL J1656.2‑3303 (z = 2.40) using quasi-simultaneous data from the Swift, Nuclear Spectroscopic Telescope Array (NuSTAR) and the Fermi-Large Area Telescope (LAT) and also archival XMM-Newton observations. Other than 3FGL J1656.2‑3303, none of the sources were known as γ-ray emitters, and our analysis of ∼7.5 yr of LAT data reveals the first time detection of statistically significant γ-ray emission from CGRaBS J0225+1846. We generate the broadband spectral energy distributions (SED) of all the objects, centering at the epoch of NuSTAR observations and reproduce them using a one-zone leptonic emission model. The optical‑UV emission in all the objects can be explained by radiation from the accretion disk, whereas the X-ray to γ-ray windows of the SEDs are found to be dominated by inverse Compton scattering off the broad line region photons. All of them host black holes that are billions of solar masses. Comparing the accretion disk luminosity and the jet power of these sources with a large sample of blazars, we find them to occupy a high disk luminosity–jet power regime. We also investigate the X-ray spectral properties of the sources in detail with a major focus on studying the causes of soft X-ray deficit, a feature generally seen in high redshift radio-loud quasars. We summarize that this feature could be explained based on the intrinsic curvature in the jet emission rather than being due to the external effects predicted in earlier studies, such as host galaxy and/or warm absorption.

  11. Probing Acceleration and Turbulence at Relativistic Shocks in Blazar Jets

    CERN Document Server

    Baring, Matthew G; Summerlin, Errol J

    2016-01-01

    Diffusive shock acceleration (DSA) at relativistic shocks is widely thought to be an important acceleration mechanism in various astrophysical jet sources, including radio-loud active galactic nuclei such as blazars. Such acceleration can produce the non-thermal particles that emit the broadband continuum radiation that is detected from extragalactic jets. An important recent development for blazar science is the ability of Fermi-LAT spectroscopy to pin down the shape of the distribution of the underlying non-thermal particle population. This paper highlights how multi-wavelength spectra spanning optical to X-ray to gamma-ray bands can be used to probe diffusive acceleration in relativistic, oblique, magnetohydrodynamic (MHD) shocks in blazar jets. Diagnostics on the MHD turbulence near such shocks are obtained using thermal and non-thermal particle distributions resulting from detailed Monte Carlo simulations of DSA. These probes are afforded by the characteristic property that the synchrotron $\

  12. Spectral and Polarization Signatures of Relativistic Shocks in Blazars

    CERN Document Server

    Boettcher, Markus

    2016-01-01

    Relativistic shocks are one of the most plausible sites of the emission of strongly variable, polarized multi-wavelength emission from relativistic jet sources such as blazars, via diffusive shock acceleration (DSA) of relativistic particles. This paper summarizes recent results on a self-consistent coupling of diffusive shock acceleration and radiation transfer in blazar jets. We demonstrate that the observed spectral energy distributions (SEDs) of blazars strongly constrain the nature of hydromagnetic turbulence responsible for pitch-angle scattering by requiring a strongly energy-dependent pitch-angle mean free path. The prominent soft X-ray excess ("Big Blue Bump") in the SED of the BL Lac object AO 0235+164 can be modelled as the signature of bulk Compton scattering of external radiation fields by the thermal electron population, which places additional constraints on the level of hydromagnetic turbulence. It has further been demonstrated that internal shocks propagating in a jet pervaded by a helical ma...

  13. Blazar origin of some IceCube events

    CERN Document Server

    Miranda, Luis Salvador; Sahu, Sarira

    2015-01-01

    Recently ANTARES collaboration presented a time dependent analysis to a selected number of flaring blazars to look for upward going muon events produced from the charge current interaction of the muon neutrinos. We use the same list of flaring blazars to look for possible positional correlation with the IceCube neutrino events. We observed that six FSRQs and two BL Lac objects from the list are within the error circles of eight IceCube events. We also observed that three FSRQs are within the error circles of more than one event. In the context of photohadronic model we propose that these neutrinos are produced within the nuclear region of the blazar where Fermi accelerated high energy protons interact with the background synchrotron/SSC photons.

  14. Multiwavelength behavior of blazars in the AGILE era

    CERN Document Server

    Vercellone, S

    2009-01-01

    The AGILE gamma-ray satellite accumulated data over two years on several blazars. Moreover, for all of the sources detected by AGILE, we exploited multiwavelength observations involving both space and ground based telescopes and consortia, obtaining in several cases broad-band spectral energy distributions (SEDs) which span from the radio wavelengths up to the TeV energy band. I will review both published and yet unpublished AGILE results on gamma-ray blazars, discussing their time variability, their gamma-ray flare durations and the theoretical modeling of the SEDs. I will also highlight the GASP-WEBT and Swift fundamental contributions to the simultaneous and long-term studies of gamma-ray blazars.

  15. Polarization Swings Reveal Magnetic Energy Dissipation in Blazars

    CERN Document Server

    Zhang, Haocheng; Boettcher, Markus; Guo, Fan; Li, Hui

    2015-01-01

    The polarization signatures of the blazar emissions are known to be highly variable. In addition to small fluctuations of the polarization angle around a mean value, sometimes large (> 180^o) polarization angle swings are observed. We suggest that such p henomena can be interpreted as arising from light-travel-time effects within an underlying axisymmetric emission region. We present the first simultaneous fitting of the multi-wavelength spectrum, variability and time-dependent polarization features of a correlated optical and gamma-ray flaring event of the prominent blazar 3C279, which was accompanied by a drastic change of its polarization signatures. This unprecedented combination of spectral, variability, and polarization information in a coherent physical model allows us to place stringent constraints on the particle acceleration and magnetic-field topology in the relativistic jet of a blazar, strongly favoring a scenario in which magnetic energy dissipation is the primary driver of the flare event.

  16. Broadband Observations of High Redshift Blazars

    CERN Document Server

    Paliya, Vaidehi S; Fabian, A C; Stalin, C S

    2016-01-01

    We present a multi-wavelength study of four high redshift blazars, S5 0014+81 ($z=3.37$), CGRaBS J0225+1846 ($z=2.69$), BZQ J1430+4205 ($z=4.72$), and 3FGL J1656.2$-$3303 ($z=2.40$), using the quasi-simultaneous data from {\\it Swift}, {\\it NuSTAR}, and {\\it Fermi}-Large Area Telescope (LAT) and also the archival {\\it XMM-Newton} observations. Other than 3FGL J1656.2$-$3303, none of the sources were known as $\\gamma$-ray emitters and our analysis of $\\sim$7.5 years of LAT data reveals the first time detection of the statistically significant $\\gamma$-ray emission from CGRaBS J0225+1846. We generate the broadband spectral energy distributions (SED) of all the objects, centering at the epoch of {\\it NuSTAR} observations and reproduce them using a one zone leptonic emission model. The optical$-$UV emission in all the objects can be explained by the radiation from the accretion disk, whereas, X-ray to $\\gamma$-ray window of the SEDs are found to be dominated by the inverse Compton scattering off the broad line reg...

  17. Applying Relativistic Reconnection to Blazar Jets

    CERN Document Server

    Nalewajko, Krzysztof

    2016-01-01

    Rapid and luminous flares of non-thermal radiation observed in blazars require an efficient mechanism of energy dissipation and particle acceleration in relativistic active galactic nuclei (AGN) jets. Particle acceleration in relativistic magnetic reconnection is being actively studied by kinetic numerical simulations. Relativistic reconnection produces hard power-law electron energy distributions N(gamma) = N_0 gamma^(-p) exp(-gamma/gamma_max) with index p -> 1 and exponential cut-off Lorentz factor gamma_max ~ sigma in the limit of magnetization sigma = B^2/(4 pi w) >> 1 (where w is the relativistic enthalpy density). Reconnection in electron-proton plasma can additionally boost gamma_max by the mass ratio m_p/m_e. Hence, in order to accelerate particles to gamma_max ~ 10^6 in the case of BL Lacs, reconnection should proceed in plasma of very high magnetization sigma_max >~ 10^3. On the other hand, moderate mean jet magnetization values are required for magnetic bulk acceleration of relativistic jets, sigma...

  18. The Lyman α forest in a blazar-heated Universe

    Science.gov (United States)

    Puchwein, Ewald; Pfrommer, Christoph; Springel, Volker; Broderick, Avery E.; Chang, Philip

    2012-06-01

    It has been realized only recently that TeV emission from blazars can significantly heat the intergalactic medium (IGM) by pair-producing high-energy electrons and positrons, which in turn excite vigorous plasma instabilities, leading to a local dissipation of the pairs' kinetic energy. In this work, we use cosmological hydrodynamical simulations to model the impact of this blazar heating on the Lyman α forest at intermediate redshifts (z˜ 2-3). We find that blazar heating produces an inverted temperature-density relation in the IGM and naturally resolves many of the problems present in previous simulations of the forest that included photoionization heating alone. In particular, our simulations with blazar heating simultaneously reproduce the observed effective optical depth and temperature as a function of redshift, the observed probability distribution functions (PDFs) of the transmitted flux, and the observed flux power spectra, over the full redshift range 2 sum of thermally broadened individual lines, we find superb agreement with the observed lower cut-off of the linewidth distribution and abundances of neutral hydrogen column densities per unit redshift. Using the most recent constraints on the cosmic ultraviolet (UV) background, this excellent agreement with observations does not require rescaling the amplitude of the UV background - a procedure that was routinely used in the past to match the observed level of transmitted flux. We also show that our blazar-heated model matches the data better than standard simulations even when such a rescaling is allowed. This concordance between Lyman α data and simulation results, which are based on the most recent cosmological parameters, also suggests that the inclusion of blazar heating alleviates previous tensions on constraints for σ8 derived from Lyman α measurements and other cosmological data. Finally, we show that blazar heating dramatically alters the volume-weighted temperature PDF, implying an

  19. From the Blazar Sequence to the Blazar Envelope: Revisiting the Relativistic Jet Dichotomy in Radio-Loud AGN

    Science.gov (United States)

    Meyer, Eileen T.; Fossati, Giovanini; Georganopoulos, Markos; Lister, Matthew L.

    2012-01-01

    We revisit the concept of a blazar sequence that relates the synchrotron peak frequency (Vpeak) in blazars with synchrotron peak luminosity (Lpeak, in vLv) using a large sample of radio-loud AGN. We present observational evidence that the blazar sequence is formed from two populations in the synchrotron Vpeak - Lpeak plane, each forming an upper edge to an envelope of progressively misaligned blazars, and connecting to an adjacent group of radio galaxies having jets viewed at much larger angles to the line of sight. When binned by jet kinetic power (Lkin; as measured through a scaling relationship with extended radio power), we find that radio core dominance decreases with decreasing synchrotron Lpeak, revealing that sources in the envelope are generally more misaligned. We find population-based evidence of velocity gradients in jets at low kinetic powers (approximately 10(exp 42) - 10(exp 44.5) erg s(exp -1)), corresponding to FR I radio galaxies and most BL Lacs. These low jet power 'weak jet' sources, thought to exhibit radiatively inefficient accretion, are distinguished from the population of non-decelerating, low synchrotron-peaking (LSP) blazars and FR II radio galaxies ('strong' jets) which are thought to exhibit radiatively efficient accretion. The two-population interpretation explains the apparent contradiction of the existence of highly core-dominated, low-power blazars at both low and high synchrotron peak frequencies, and further implies that most intermediate synchrotron peak (ISP) sources are not intermediate in intrinsic jet power between LSP and high synchrotron-peaking (HSP) sources, but are more misaligned versions of HSP sources with similar jet powers.

  20. MAGIC detection of short-term variability of the high-peaked BL Lac object 1ES 0806+524

    CERN Document Server

    Aleksić, J; Antonelli, L A; Antoranz, P; Babic, A; Bangale, P; Barrio, J A; González, J Becerra; Bednarek, W; Bernardini, E; Biasuzzi, B; Biland, A; Blanch, O; Bonnefoy, S; Bonnoli, G; Borracci, F; Bretz, T; Carmona, E; Carosi, A; Colin, P; Colombo, E; Contreras, J L; Cortina, J; Covino, S; Da Vela, P; Dazzi, F; De Angelis, A; De Caneva, G; De Lotto, B; Wilhelmi, E de O na; Mendez, C Delgado; Di Pierro, F; Prester, D Dominis; Dorner, D; Doro, M; Einecke, S; Eisenacher, D; Elsaesser, D; Fernández-Barral, A; Fidalgo, D; Fonseca, M V; Font, L; Frantzen, K; Fruck, C; Galindo, D; López, R J García; Garczarczyk, M; Terrats, D Garrido; Gaug, M; Godinović, N; noz, A González Mu; Gozzini, S R; Hadasch, D; Hanabata, Y; Hayashida, M; Herrera, J; Hose, J; Hrupec, D; Idec, W; Kadenius, V; Kellermann, H; Knoetig, M L; Kodani, K; Konno, Y; Krause, J; Kubo, H; Kushida, J; La Barbera, A; Lelas, D; Lewandowska, N; Lindfors, E; Lombardi, S; Longo, F; López, M; López-Coto, R; López-Oramas, A; Lorenz, E; Lozano, I; Makariev, M; Mallot, K; Maneva, G; Mannheim, K; Maraschi, L; Marcote, B; Mariotti, M; Martínez, M; Mazin, D; Menzel, U; Miranda, J M; Mirzoyan, R; Moralejo, A; Munar-Adrover, P; Nakajima, D; Neustroev, V; Niedzwiecki, A; Rosillo, M Nievas; Nilsson, K; Nishijima, K; Noda, K; Orito, R; Overkemping, A; Paiano, S; Palatiello, M; Paneque, D; Paoletti, R; Paredes, J M; Paredes-Fortuny, X; Persic, M; Poutanen, J; Moroni, P G Prada; Prandini, E; Puljak, I; Reinthal, R; Rhode, W; Ribó, M; Rico, J; Garcia, J Rodriguez; Saito, T; Saito, K; Satalecka, K; Scalzotto, V; Scapin, V; Schultz, C; Schweizer, T; Shore, S N; Sillanpää, A; Sitarek, J; Snidaric, I; Sobczynska, D; Stamerra, A; Steinbring, T; Strzys, M; Takalo, L; Takami, H; Tavecchio, F; Temnikov, P; Terzić, T; Tescaro, D; Teshima, M; Thaele, J; Torres, D F; Toyama, T; Treves, A; Vogler, P; Will, M; Zanin, R; Berger, K; Buson, S; D'Ammando, F; Gasparrini, D; Hovatta, T; Max-Moerbeck, W; Readhead, A; Richards, J

    2015-01-01

    The high-frequency-peaked BL Lac (HBL) 1ES 0806+524 (z = 0.138) was discovered in VHE $\\gamma$ rays in 2008. Until now, the broad-band spectrum of 1ES 0806+524 has been only poorly characterized, in particular at high energies. We analysed multiwavelength observations from $\\gamma$ rays to radio performed from 2011 January to March, which were triggered by the high activity detected at optical frequencies. These observations constitute the most precise determination of the broad-band emission of 1ES 0806+524 to date. The stereoscopic MAGIC observations yielded a $\\gamma$-ray signal above 250 GeV of $(3.7 \\pm 0.7)$ per cent of the Crab Nebula flux with a statistical significance of 9.9 $\\sigma$. The multiwavelength observations showed significant variability in essentially all energy bands, including a VHE $\\gamma$-ray flare that lasted less than one night, which provided unprecedented evidence for short-term variability in 1ES 0806+524. The spectrum of this flare is well described by a power law with a photon...

  1. A Catalog of Candidate High-redshift Blazars for GLAST

    Energy Technology Data Exchange (ETDEWEB)

    Arias, Tersi M.; /SLAC /San Francisco State U.

    2006-09-27

    High-redshift blazars are promising candidates for detection by the Gamma-ray Large Area Space Telescope (GLAST). GLAST, expected to be launched in the Fall of 2007, is a high-energy gamma-ray observatory designed for making observations of celestial gamma-ray sources in the energy band extending from 10 MeV to more than 200 GeV. It is estimated that GLAST will find several thousand blazars. The motivations for measuring the gamma-ray emission from distant blazars include the study of the high-energy emission processes occurring in these sources and an indirect measurement of the extragalactic background light. In anticipation of the launch of GLAST we have compiled a catalog of candidate high-redshift blazars. The criteria for sources chosen for the catalog were: high radio emission, high redshift, and a flat radio spectrum. A preliminary list of 307 radio sources brighter than 70mJy with a redshift z {ge} 2.5 was acquired using data from the NASA Extragalactic Database. Flux measurements of each source were obtained at two or more radio frequencies from surveys and catalogs to calculate their radio spectral indices {alpha}. The sources with a flat-radio spectrum ({alpha} {le} 0.5) were selected for the catalog, and the final catalog includes about 200 sources.

  2. Long-term optical-infrared color variability of blazars

    International Nuclear Information System (INIS)

    The long-term optical and infrared color variability of blazars has been investigated with monitoring data from the Small and Moderate Aperture Research Telescope System (SMARTS). The sample in this study consists of 49 flat spectrum radio quasars (FSRQs) and 22 BL Lacertae objects (BL Lacs). The fractional variability amplitudes of each source have been calculated in both optical R band and infrared J band. Overall, the variability amplitudes of FSRQs are larger than those of BL Lacs. The results also suggest that the variability amplitude of most FSRQs is larger at a lower energy band (J band) than at a higher one (R band), but the variability amplitude of BL Lacs is larger at the higher energy band. Both types of blazars display color variation along with variability in brightness. However, they show different variation behaviors in general. In the whole data set, 35 FSRQs exhibit redder-when-brighter trends, and 11 FSRQs exhibit opposite trends; 11 BL Lacs follow bluer-when-brighter trends, and seven BL Lacs follow opposite trends. A detailed examination indicates that there are 10 blazars showing redder-when-brighter trends in their low state, and bluer-when-brighter or stable-when-brighter trends in their high state. Some more complicated color behaviors have also been detected in several blazars. The non-thermal jet emission and the thermal emission from the accretion disk are employed to explain the observed color behaviors. (paper)

  3. Relation between Radio Polarization and Spectral Index of Blazars

    Indian Academy of Sciences (India)

    Yuhai Yuan

    2014-09-01

    University Michigan RAdio Observatory (UMRAO) supply many radio photometries and polarimetries. We select a sample of 81 blazars from UMRAO and analyse the correlations between their spectral index and polarizations. Out of 35 BL Lacs and 46 FSRQs in the sample, 8 and 15 show strong correlation.

  4. Modeling Fermi Large Area Telescope and Multiwavelength Data from Blazars

    CERN Document Server

    Finke, Justin

    2016-01-01

    Blazars are active galactic nuclei with relativistic jets pointed at the Earth, making them extremely bright at essentially all wavelengths, from radio to gamma rays. I review the modeling of this broadband spectral energy distributions of these objects, and what we have learned, with a focus on gamma rays.

  5. A search of CO emission lines in blazars: the low molecular gas content of BL Lac objects compared to quasars

    Science.gov (United States)

    Fumagalli, Michele; Dessauges-Zavadsky, Miroslava; Furniss, Amy; Prochaska, J. Xavier; Williams, David A.; Kaplan, Kyle; Hogan, Matthew

    2012-08-01

    BL Lacertae (Lac) objects that are detected at very high energies (VHE) are of fundamental importance to study multiple astrophysical processes, including the physics of jets, the properties of the extragalactic background light and the strength of the intergalactic magnetic field. Unfortunately, since most blazars have featureless optical spectra that preclude a redshift determination, a substantial fraction of these VHE extragalactic sources cannot be used for cosmological studies. To assess whether molecular lines are a viable way to establish distances, we have undertaken a pilot programme at the Institut of Millimétrique (IRAM) 30 m telescope to search for CO lines in three BL Lac objects with known redshifts. We report a positive detection of 12 MH_2 ˜ 3 × 10>8 M⊙ towards 1ES 1959+650, but due to the poor quality of the baseline, this value is affected by a large systematic uncertainty. For the remaining two sources, W Comae and RGB J0710+591, we derive 3σ upper limits at, respectively, H2 conversion factor α = 4 M⊙ (K km s-1 pc2)-1. If these low molecular gas masses are typical for blazars, blind redshift searches in molecular lines are currently unfeasible. However, deep observations are still a promising way to obtain precise redshifts for sources whose approximate distances are known via indirect methods. Our observations further reveal a deficiency of molecular gas in BL Lac objects compared to quasars, suggesting that the host galaxies of these two types of active galactic nuclei (AGN) are not drawn from the same parent population. Future observations are needed to assess whether this discrepancy is statistically significant, but our pilot programme shows how studies of the interstellar medium in AGN can provide key information to explore the connection between the active nuclei and the host galaxies. Based on observations carried out with the IRAM 30 m telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).

  6. VARIABILITY OF GAMMA-RAY EMISSION FROM BLAZARS ON BLACK HOLE TIMESCALES

    International Nuclear Information System (INIS)

    We investigate the variability properties of blazars in the GeV band using data from the Fermi/Large Area Telescope (LAT) telescope. We find that blazars exhibit variability down to the minimum timescale resolvable by Fermi; this variability is a function of the peak photon count rate in the LAT. This implies that the real minimum variability timescales for the majority of blazars are typically shorter than those resolvable by the LAT. We find that for several blazars these minimum variability timescales reach those associated with the blazar central engine, the supermassive black hole. At the same time, none of the blazars exhibits variability on a timescale shorter than the black hole horizon light-crossing time and/or the period of rotation around the last stable circular orbit. Based on this fact, we argue that the timing properties of the γ-ray signal could be determined by the processes in the direct vicinity of the supermassive black hole.

  7. Lorentz factor distribution of blazars from the optical Fundamental plane of black hole activity

    CERN Document Server

    Saikia, Payaswini; Falcke, Heino

    2016-01-01

    Blazar radiation is dominated by a relativistic jet which can be modeled at first approximation using just two intrinsic parameters - the Lorentz factor $\\Gamma$ and the viewing angle $\\theta$. Blazar jet observations are often beamed due to relativistic effects, complicating the understanding of these intrinsic properties. The most common way to estimate blazar Lorentz factors needs the estimation of apparent jet speeds and Doppler beaming factors. We present a new and independent method of constructing the blazar Lorentz factor distribution, using the optical fundamental plane of black hole activity. The optical fundamental plane is a plane stretched out by both the supermassive black holes and the X-ray binaries, in the 3D space provided by their [OIII] line luminosity, radio luminosity and black hole mass. We use the intrinsic radio luminosity obtained from the optical fundamental plane to constrain the boosting parameters of the VLBA Imaging and Polarimetry Survey (VIPS) blazar sample. We find a blazar b...

  8. Position Angle Changes of Inner-Jets in a Sample of Blazars

    Indian Academy of Sciences (India)

    Ligong Mi; Xiang Liu

    2014-09-01

    We have carried out the Gaussian model-fitting to 15 GHz VLBAcores for a sample of blazars from the MOJAVE database, analysed the correlations in the model-fitted parameters and studied the variability properties for different group of sources. We found that the Fermi LAT-detected blazars have on an average higher position angle changes of cores than the non-LAT detected blazars, and that the LAT-detected ones are associated with more variable cores in flux density.

  9. Data reduction and analysis of the multiband optical images of the blazar Mrk180

    OpenAIRE

    M Sabzi Sarvestani; AR Aghaee

    2012-01-01

     Nearly simultaneous multiband monitoring of blazars is very limited and most studies reported in literature are conflicting, too. Although optical variability on intra-night timescales is now a well established phenomenon for blazars, its relationship to long-term variability remains unclear. Possible clues could come from monitoring the optical spectrum for correlation with brightness. The presence or absence of bluer color in blazar color index, when its luminosity is increased on intra-ni...

  10. Data reduction and analysis of the multiband optical images of the blazar Mrk180

    Directory of Open Access Journals (Sweden)

    M Sabzi Sarvestani

    2012-09-01

    Full Text Available  Nearly simultaneous multiband monitoring of blazars is very limited and most studies reported in literature are conflicting, too. Although optical variability on intra-night timescales is now a well established phenomenon for blazars, its relationship to long-term variability remains unclear. Possible clues could come from monitoring the optical spectrum for correlation with brightness. The presence or absence of bluer color in blazar color index, when its luminosity is increased on intra-night and inter-night timescales, can provide interesting clues to the origin of blazar variability from hourly to much longer timescales. Luminosity of blazars varies at all wavelengths over a variety of timescales. Various models have been proposed to explain blazar variability. However, the mechanism responsible for variability is not conclusively understood. One factor which can discriminate the various variability models is that of color (spectral index variations of blazars. This factor may help to better understand the mechanism of blazar variability. Therefore, it was initially proposed, by the second author of this paper to the OHP observatory, to carry out quasi-simultaneous multiband monitoring of one of the brightest blazer, Mrk180. Fortunately, it was accepted by the scientific team of the observatory and the 1.20m telescope time was allocated to the project from 23 to 28 April 2009. Because of the weather conditions, we could only monitor this blazar for three nights. Raw data processing and data reduction were performed using the standard system of Europe Southerner Observatory, ESO-MIDAS. We considered two reference stars and measured the magnitudes of the reference stars and the blazar Mrk 180 and then plotted the light curves and the color index diagrams. The light curves showed the optical variations of the blazar. The maximum amplitude value of its variations was 0.185 mag for the V filter. Investigating the blazar color index shows its

  11. Peak of spectral energy distribution play an important role in intra-day variability of Blazars?

    OpenAIRE

    Gupta, Alok C.; Kalita, Nibedita; Gaur, Haritma; Duorah, Kalpana

    2016-01-01

    Blazars can be divided into two sub-classes namely high energy and low energy peaked blazars. In spectral energy distribution, the first synchrotron hump of the former class peaks in UV/X-rays and in IR/optical bands for the latter class. The peak of the spectral energy distribution seems to be responsible for variability properties of these classes of blazars in X-ray and optical bands. Since, in low energy peaked blazars, the X-ray bands lies well below the synchrotron hump, one expects tha...

  12. VERITAS results from a three-year observing campaign on the BL Lac object 1ES 0229+200

    CERN Document Server

    Cerruti, Matteo

    2013-01-01

    The BL Lac object 1ES 0229+200 is a firmly established very-high-energy (VHE; E >100 GeV) source. Located at a redshift of 0.1396, its published VHE spectrum is particularly hard (Gamma ~2.5) and is widely used to perform studies on the extragalactic background light (EBL) and the intergalactic magnetic field (IGMF). We present here the results of a long-term observing campaign on 1ES 0229+200 with VERITAS, lasting from 2009 to 2012, supported by multi-wavelength observations. We discuss the VERITAS results with a particular emphasis on the implications for the synchrotron-self-Compton modeling of the source emission and for the theoretical studies (especially on the intergalactic magnetic field) based on its VHE spectrum.

  13. HST/COS Observations of the Ly alpha Forest toward the BL Lac Object 1ES1553+113

    CERN Document Server

    Danforth, Charles W; Stocke, John T; Shull, J Michael; Yao, Yangsen

    2010-01-01

    We present new far-ultraviolet spectra from the Cosmic Origins Spectrograph (HST/COS) of the BL Lac object 1ES1553+113 covering the wavelength range 1135-1795 A. The data show a smooth continuum with a wealth of narrow absorption features arising in the ISM and IGM. These features include 41 Lya absorbers at 00.6 for the strongest component of the absorber complex. Galaxy redshift surveys show a number of massive galaxies at approximately the same redshift as this absorption complex, suggesting that it arises in a large-scale galaxy filament. As one of the brightest extragalactic X-ray and gamma-ray sources, 1ES1553+113 is of great interest to the high-energy astrophysics community. With no intrinsic emission or absorption features, 1ES1553+113 has no direct redshift determination. We use intervening Lya absorbers to place a direct limit on the redshift: z_em>0.395 based on a confirmed Lya+OVI absorber and z_em>0.433 based on a single-line detection of Lya. COS/FUV data are only sensitive to Lya absorbers at ...

  14. Blazar Jets Push Closer to Cosmic Speed Limit

    Science.gov (United States)

    2005-01-01

    Astronomers using the National Science Foundation's Very Long Baseline Array (VLBA) have discovered jets of plasma blasted from the cores of distant galaxies at speeds within one-tenth of one percent of the speed of light, placing these plasma jets among the fastest objects yet seen in the Universe. "This tells us that the physical processes at the cores of these galaxies, called blazars, are extremely energetic and are capable of propelling matter very close to the absolute cosmic speed limit," said Glenn Piner of Whittier College in Whittier, California. Piner, who worked on the project with student Dipesh Bhattari, also of Whittier College, Philip Edwards of the Japan Aerospace Exploration Agency, and Dayton Jones of NASA's Jet Propulsion Laboratory, presented their findings to the American Astronomical Society's meeting in San Diego, California. According to Einstein's Special Theory of Relativity, no object with mass can be accelerated to the speed of light. To get even close to the speed of light requires enormous amounts of energy. "For example, to accelerate a bowling ball to the speed newly measured in these blazars would require all the energy produced in the world for an entire week," Piner said, "and the blobs of plasma in these jets are at least as massive as a large planet". Blazars are active galactic nuclei -- energetic regions surrounding massive black holes at the centers of galaxies. Material being drawn into the black hole forms a spinning disk called an accretion disk. Powerful jets of charged particles are ejected at high speeds along the poles of accretion disks. When these jets happen to be aimed nearly toward the Earth, the objects are called blazars. Taking advantage of the extremely sharp radio "vision" of the continent-wide VLBA, the scientists tracked individual features in the jets of three blazars at distances from Earth ranging from 7.3 to 9 billion light-years. A Boston University team led by Svetlana Jorstad earlier had identified

  15. Models for High-Energy Radiation from Blazars

    Indian Academy of Sciences (India)

    G. E. Romero; M. M. Reynoso

    2011-03-01

    We discuss on the modelling of blazar jets as emitters of multiwavelength radiation with the implementation of a lepto-hadronic treatment. Assuming that injection of non-thermal electrons and protons can take place at the base of the jet, the stationary particle distributions can be found using an inhomogeneous one-dimensional transport equation with cooling and convection. The goal of this approach is to replace the widely used one-zone purely leptonic approximation by a more realistic model. We argue that the rapid variability observed in emission from blazars can be obtained as a result of interaction of the jet with obstacles, i.e., molecular clouds and stars. Long term variability is likely related to changes in the injection and physical conditions in the acceleration region.

  16. Optical flux behaviour of a sample of Fermi blazars

    CERN Document Server

    Marchesini, E J; Cellone, S A; Combi, J A; Zibecchi, L; Martí, J; Romero, G E; Muñoz-Arjonilla, A J; Luque-Escamilla, P; Sánchez-Sutil, J R

    2016-01-01

    Aims: We aim at investigating the time-behaviour of a sample of gamma-ray blazars. We present the results from a 13 month-long optical photometry monitoring campaign of the blazars PKS 0048-097, PKS 0754+100, HB89 0827+243, PKS 0851+202, PKS 1253-055, PKS1510-089, PKS 1749+096, PKS 2230+114 and PKS 2251+158. Methods: We analyse the variability of each object, focusing on different time-scales (long term, short term, and microvariability), in an attempt to achieve a statistical comparison of the results. Results: After applying a geometric model to explain the variability results, we found that it is possible that a slight change in the direction of the jet generates the variations detected in some objects during this campaign.

  17. Properties of Blazar Jets Defined by an Economy of Power

    Science.gov (United States)

    Petropoulou, Maria; Dermer, Charles D.

    2016-07-01

    The absolute power of a relativistic black hole jet includes the power in the magnetic field, the leptons, the hadrons, and the radiated photons. A power analysis of a relativistic radio/γ-ray blazar jet leads to bifurcated leptonic synchrotron-Compton (LSC) and leptohadronic synchrotron (LHS) solutions that minimize the total jet power. Higher Doppler factors with increasing peak synchrotron frequency are implied in the LSC model. Strong magnetic fields {B}\\prime ≳ 100 {{G}} are found for the LHS model with variability times ≲ {10}3 {{s}}, in accord with highly magnetized, reconnection-driven jet models. Proton synchrotron models of ≳ 100 {GeV} blazar radiation can have sub-Eddington absolute jet powers, but models of dominant GeV radiation in flat spectrum radio quasars require excessive power.

  18. QUASI-PERIODICITIES AT YEAR-LIKE TIMESCALES IN BLAZARS

    Energy Technology Data Exchange (ETDEWEB)

    Sandrinelli, A.; Treves, A. [Università degli Studi dell’Insubria, Dipartimento di Scienza ed Alta Tecnologia, Via Valleggio 11, I-22100 Como (Italy); Covino, S. [INAF—Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Brera, Via Emilio Bianchi 46, I-23807 Merate (Italy); Dotti, M. [Università degli Studi di Milano Bicocca, Dipartimento di Fisica G. Occhialini, Piazza della Scienza 3, I-20126 Milano (Italy)

    2016-03-15

    We searched for quasi-periodicities on year-like timescales in the light curves of six blazars in the optical—near-infrared bands and we made a comparison with the high energy emission. We obtained optical/NIR light curves from Rapid Eye Mounting photometry plus archival Small and Moderate Aperture Research Telescope System data and we accessed the Fermi light curves for the γ-ray data. The periodograms often show strong peaks in the optical and γ-ray bands, which in some cases may be inter-related. The significance of the revealed peaks is then discussed, taking into account that the noise is frequency dependent. Quasi-periodicities on a year-like timescale appear to occur often in blazars. No straightforward model describing these possible periodicities is yet available, but some plausible interpretations for the physical mechanisms causing periodic variabilities of these sources are examined.

  19. The disk-jet connection of Fermi 2LAC blazars

    Science.gov (United States)

    Du, L. M.; Xie, Zh. H.; Yi, T. F.; Xue, R.; Xu, Y. B.; Liu, W. G.; Wang, X. H.

    2016-07-01

    In this article, an estimator of the radiative power for blazars is proposed and is used in the study of the link between the accretion disk power and jet power. The results lend support to the disk-jet symbiosis. Since the blazars are strongly beamed sources, our results suggest that the Doppler enhancement of the sources needs to be removed to obtain physically reasonable results in the disk-jet connection study. The results after de-beaming suggest that FSRQs are accreting in the radiatively efficient regime, while the BL Lac population shows a flatter dependence between jet power and disk power, possibly due to a mixture of sources in the radiatively efficient (the broad lined BL Lacs) and inefficient (the bulk of the BL Lac population) regimes.

  20. Extremely violent optical microvariability in blazars: fact or fiction?

    CERN Document Server

    Cellone, S A; Araudo, A T; Cellone, Sergio A.; Romero, Gustavo E.; Araudo, Anabella T.

    2006-01-01

    Variability amplitudes larger than 1 magnitude over time-scales of a few tens of minutes have recently been reported in the optical light-curves of several blazars. In order to independently verify the real occurrence of such extremely violent events, we undertook an observational study of a selected sample of three blazars: PKS 0048-097, PKS 0754+100, and PKS 1510-089. Possible systematic error sources during data acquisition and reduction were carefully evaluated. We indeed found flux variability at intra-night time-scales in all three sources, although no extremely violent behaviour, as reported by other authors, was detected. We show that an incorrect choice of the stars used for differential photometry will, under fairly normal conditions, lead to spurious variability with large amplitudes on short time-scales. Wrong results of this kind can be avoided with the use of simple error-control techniques.

  1. A BLAZAR-LIKE RADIO FLARE IN MRK 231

    International Nuclear Information System (INIS)

    Radio monitoring of the broad absorption line quasar (BALQSO) Mrk 231 from 13.9 GHz to 17.6 GHz detected a strong flat spectrum flare. Even though BALQSOs are typically weak radio sources, the 17.6 GHz flux density doubled in ≈150 days, from ≈135 mJy to ≈270 mJy. It is demonstrated that the elapsed rise time in the quasar rest frame and the relative magnitude of the flare is typical of some of the stronger flares in blazars that are usually associated with the ejection of discrete components on parsec scales. The decay of a similar flare was found in a previous monitoring campaign at 22 GHz. We conclude that these flares are not rare. The implication is that Mrk 231 seems to be a quasar in which the physical mechanism that produces the broad absorption line wind is in tension with the emergence of a fledgling blazar

  2. A BLAZAR-LIKE RADIO FLARE IN MRK 231

    Energy Technology Data Exchange (ETDEWEB)

    Reynolds, Cormac; Hurley-Walker, Natasha [ICRAR-Curtin University, GPO Box U1987, Perth, Western Australia, 6102 (Australia); Punsly, Brian [1415 Granvia Altamira, Palos Verdes Estates, CA 90274 (United States); O' Dea, Christopher P., E-mail: brian.punsly1@verizon.net, E-mail: brian.punsly@comdev-usa.com [Laboratory for Multiwavelength Astrophysics, School of Physics and Astronomy, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States)

    2013-10-20

    Radio monitoring of the broad absorption line quasar (BALQSO) Mrk 231 from 13.9 GHz to 17.6 GHz detected a strong flat spectrum flare. Even though BALQSOs are typically weak radio sources, the 17.6 GHz flux density doubled in ≈150 days, from ≈135 mJy to ≈270 mJy. It is demonstrated that the elapsed rise time in the quasar rest frame and the relative magnitude of the flare is typical of some of the stronger flares in blazars that are usually associated with the ejection of discrete components on parsec scales. The decay of a similar flare was found in a previous monitoring campaign at 22 GHz. We conclude that these flares are not rare. The implication is that Mrk 231 seems to be a quasar in which the physical mechanism that produces the broad absorption line wind is in tension with the emergence of a fledgling blazar.

  3. The TANAMI Multiwavelength Program: Dynamic SEDs of Southern Blazars

    OpenAIRE

    Krauß, Felicia; Wilms, Joern; Kadler, Matthias; Ojha, Roopesh; Schulz, Robert; Trüstedt, Jonas; Edwards, Philip G.; Stevens, Jamie; Ros, Eduardo; Baumgartner, Wayne; Beuchert, Tobias; Blanchard, Jay; Buson, Sara; Carpenter, Bryce; Dauser, Thomas

    2016-01-01

    Simultaneous broadband spectral and temporal studies of blazars are an important tool for investigating active galactic nuclei (AGN) jet physics. We study the spectral evolution between quiescent and flaring periods of 22 radio-loud AGN through multi-epoch, quasi-simultaneous broadband spectra. For many of these sources these are the first broadband studies. We use a Bayesian block analysis of \\Fermi/LAT light curves in order to determine time ranges of constant flux for constructing quasi-si...

  4. Observing Blazar Variability: The GTN-AAVSO Collaboration

    Science.gov (United States)

    Spear, G.; Price, A.; Plait, P.; Graves, T.; Cominsky, L.; Mattei, J.

    2004-05-01

    The NASA/EPO group at Sonoma State University is creating the GLAST Ground-Based Telescope Network (GTN). The GTN is a series of telescopes and observers which will support the science and education goals of NASA's Gamma-Ray Large Area Space Telescope. The GTN is a collaboration with the American Association of Variable Star Observers (AAVSO), other amateurs, schools, and professionals. GLAST will observe gamma rays from high-energy sources such as blazars. The ground-based telescopes will observe GLAST targets to provide a multi-year baseline of variability characteristics. During the mission the network will observe these targets simultaneously with GLAST to provided multi-wavelength coverage. Because of recent improvements in the sensitivity of CCD detectors and the improved reliability of computer controlled (robotic) telescopes, amateurs and students can now obtain professional quality data, and can make substantial contributions to the science goals of space observatories such as GLAST. Because of the unpredictability of blazar variability it is important to obtain as many observations as possible. A distributed network of committed observers is ideally suited. Indeed, such a network is essential to accumulate the data needed to ultimately understand the variability mechanism and the production of the gamma rays in this type of active galaxy. Amateurs are ideally suited to provide this type of coverage while professionals are finding it increasingly difficult to obtain telescope time on small telescopes. We will describe the resource materials and tutorials that are available through the GTN and the AAVSO, the GTN blazar image archive, the AAVSO international database of magnitudes, and the various levels of contributions to provide the required science data. We will also show comparisons of blazar data accumulated by professionals, by the AAVSO, and by students. Finally we will provide a status report for the 0.3 meter robotic telescope system being

  5. Probing Acceleration and Turbulence at Relativistic Shocks in Blazar Jets

    Science.gov (United States)

    Baring, Matthew G.; Böttcher, Markus; Summerlin, Errol J.

    2016-09-01

    Diffusive shock acceleration (DSA) at relativistic shocks is widely thought to be an important acceleration mechanism in various astrophysical jet sources, including radio-loud active galactic nuclei such as blazars. Such acceleration can produce the non-thermal particles that emit the broadband continuum radiation that is detected from extragalactic jets. An important recent development for blazar science is the ability of Fermi-LAT spectroscopy to pin down the shape of the distribution of the underlying non-thermal particle population. This paper highlights how multi-wavelength spectra spanning optical to X-ray to gamma-ray bands can be used to probe diffusive acceleration in relativistic, oblique, magnetohydrodynamic (MHD) shocks in blazar jets. Diagnostics on the MHD turbulence near such shocks are obtained using thermal and non-thermal particle distributions resulting from detailed Monte Carlo simulations of DSA. These probes are afforded by the characteristic property that the synchrotron νFν peak energy does not appear in the gamma-ray band above 100 MeV. We investigate self-consistently the radiative synchrotron and inverse Compton signatures of the simulated particle distributions. Important constraints on the diffusive mean free paths of electrons, and the level of electromagnetic field turbulence are identified for three different case study blazars, Mrk 501, BL Lacertae and AO 0235+164. The X-ray excess of AO 0235+164 in a flare state can be modelled as the signature of bulk Compton scattering of external radiation fields, thereby tightly constraining the energy-dependence of the diffusion coefficient for electrons. The concomitant interpretations that turbulence levels decline with remoteness from jet shocks, and the probable significant role for non-gyroresonant diffusion, are posited.

  6. Localizing the $\\gamma$ rays from blazar PKS 1502+106

    CERN Document Server

    Karamanavis, Vassilis; Krichbaum, T P; Angelakis, E; Hodgson, J; Myserlis, I; Nestoras, I; Zensus, J A; Ungerechts, H; Sievers, A

    2015-01-01

    Blazars are among the most variable objects in the universe. They feature energetic jets of plasma that launch from the cores of these active galactic nuclei (AGN), triggering activity from radio up to gamma-ray energies. Spatial localization of the region of their MeV/GeV emission is a key question in understanding the blazar phenomenon. The flat spectrum radio quasar (FSRQ) PKS 1502+106 has exhibited extreme and correlated, radio and high-energy activity that triggered intense monitoring by the Fermi-GST AGN Multi-frequency Monitoring Alliance (F-GAMMA) program and the Global Millimeter VLBI Array (GMVA) down to $\\lambda$3 mm (or 86 GHz), enabling the sharpest view to date towards this extreme object. Here, we report on preliminary results of our study of the gamma-ray loud blazar PKS 1502+106, combining VLBI and single dish data. We deduce the critical aspect angle towards the source to be $\\theta_{\\rm c} = 2.6^{\\circ}$, calculate the apparent and intrinsic opening angles and constrain the distance of the ...

  7. The RINGO2 and DIPOL Optical Polarisation Catalogue of Blazars

    CERN Document Server

    Jermak, H; Lindfors, E; Hovatta, T; Nilsson, K; Lamb, G P; Mundell, C; de Almeida, U Barres; Berdyugin, A; Kadenius, V; Reinthal, R; Takalo, L

    2016-01-01

    We present ~2000 polarimetric and ~3000 photometric observations of 15 gamma-ray bright blazars over a period of 936 days (11/10/2008 - 26/10/2012) using data from the Tuorla blazar monitoring program (KVA DIPOL) and Liverpool Telescope (LT) RINGO2 polarimeters (supplemented with data from SkyCamZ (LT) and Fermi-LAT gamma-ray data). In 11 out of 15 sources we identify a total of 19 electric vector position angle (EVPA) rotations and 95 flaring episodes. We group the sources into subclasses based on their broadband spectral characteristics and compare their observed optical and gamma-ray properties. We find that (1) the optical magnitude and gamma-ray flux are positively correlated, (2) EVPA rotations can occur in any blazar subclass, 4 sources show rotations that go in one direction and immediately rotate back, (3) we see no difference in the gamma-ray flaring rates in the sample; flares can occur during and outside of rotations with no preference for this behaviour, (4) the average degree of polarisation (Do...

  8. The power and production efficiency of blazar jets

    CERN Document Server

    Pjanka, Patryk; Sikora, Marek

    2016-01-01

    We use published data on the power and production efficiency of jets in blazars with double radio lobes in order to compare results obtained using different methods. In order to eliminate selection effects, we use cross-matched sub-samples containing only luminous blazars. We compare the three main existing methods, namely those based on the emission of radio lobes, on spectral fitting, and on radio core shift. We find the average jet power obtained for identical samples with the radio-lobe method is $\\sim10$ times lower than that from the spectral fitting. In turn, the power from spectral fitting is compatible with that from core-shift modelling for plausible parameters of the latter. We also consider a phenomenological estimator based on the {\\gamma}-ray luminosity. We examine uncertainties of those methods and discuss two alternative hypotheses. In one, the blazar-fit and core-shift methods are assumed to be correct, and the lower power from radio lobes is caused by intermittency of accretion. Long periods...

  9. Blazars distance indications from Fermi and TeV data

    CERN Document Server

    Prandini, Elisa; Maraschi, Laura; Mariotti, Mose'; Tavecchio, Fabrizio

    2011-01-01

    A new method to constrain the distance of blazars with unknown redshift using combined observations in the GeV and TeV regimes will be presented. The underlying assumption is that the Very High Energy (VHE) spectrum corrected for the absorption of TeV photons by the Extragalactic Background Light (EBL) via photon-photon interaction should still be softer than the extrapolation of the gamma-ray spectrum observed by Fermi/LAT. Starting from the observed spectral data at VHE, the EBL-corrected spectra are derived as a function of the redshift z and fitted with power laws. Comparing the redshift dependent VHE slopes with the power law fits to the LAT data an upper limit to the source redshift can be derived. The method is applied to all TeV blazars detected by LAT with known distance and an empirical law describing the relation between the upper limits and the true redshifts is derived. This law can be used to estimate the distance of unknown redshift blazars: as an example, the distance of PKS 1424+240 is inferr...

  10. Blazar candidates beyond redshift 4 observed with GROND

    CERN Document Server

    Sbarrato, T; Nardini, M; Tagliaferri, G; Greiner, J; Rau, A; Schady, P

    2013-01-01

    The search for extremely massive high redshift blazars is essential to put strong constraints on the supermassive black holes formation theories. Up to now, the few blazars known to have a redshift larger than 4 have been discovered serendipitously. We try a more systematic approach. Assuming radio-loudness as a proxy for the jet orientation, we select a sample of extremely radio-loud quasars. We measure their black hole masses with a method based on fitting the thermal emission from the accretion disc. We achieve a precision of a factor of two for our measures, thanks to the observations performed with the Gamma-Ray Burst Optical Near-Infrared Detector (GROND). The infrared to optical GROND data allow us to observe directly the peak of the disc emission, thus constraining the overall disc luminosity. We obtain a small range of masses, that peaks at 10^{9.3}Msun. If some of our candidates will be confirmed as blazars, these results would introduce interesting constraints on the mass function of extremely mass...

  11. High redshift Fermi blazars observed by GROND and Swift

    CERN Document Server

    Ghisellini, G; Tagliaferri, G; Greiner, J; Schady, P; Rau, A; Foschini, L; Tavecchio, F; Ghirlanda, G; Sbarrato, T

    2012-01-01

    We observed 5 gamma-ray loud blazars at redshift greater than 2 with the X-Ray Telescope (XRT) and the UltraViolet and Optical Telescope (UVOT) onboard the Swift satellite, and the Gamma-Ray burst Optical Near-Infrared Detector (GROND) instrument. These observations were quasi simultaneous, usually within a few hours. For 4 of these blazars the near-IR to UV data show the presence of an accretion disc, and we could reliably estimate its accretion rate and black hole mass. One of them, PKS 1348+007, was found in an extraordinarily high IR-optical state, almost two orders of magnitude brighter than at the epoch of the Sloan Digital Sky Survey observations. For all the 5 quasars the physical parameters of the jet emitting zone, derived by applying a one-zone emission model, are similar to that found for the bulk of other gamma-ray loud quasars. With our observations we have X-ray data for the full sample of blazars at z>2 present in the Fermi 2-yrs (2LAC) catalog. This allows to have a rather complete view of th...

  12. Blazar candidates beyond redshift 4 observed by Swift

    CERN Document Server

    Sbarrato, T; Tagliaferri, G; Foschini, L; Nardini, M; Tavecchio, F; Gehrels, N

    2014-01-01

    We have selected SDSS J222032.50+002537.5 and SDSS J142048.01+120545.9 as best blazar candidates out of a complete sample of extremely radio-loud quasars at z>4, with highly massive black holes. We observed them and a third serendipitous candidate with similar features (PMN J2134-0419) in the X-rays with the Swift/XRT telescope, to confirm their blazar nature. We observed strong and hard X-ray fluxes in all three cases. This allowed us to classify our candidates as real blazars, being characterized by large Lorentz factors (~13) and very small viewing angles (~3deg). All three sources have black hole masses exceeding 10^9Msun and their classification provides intriguing constraints on supermassive black hole formation and evolution models. We confirm our earlier suggestion that there are different formation epochs of extremely massive black holes hosted in jetted (z~4) and non-jetted systems (z~2.5).

  13. Leptonic and Hadronic Modeling of Fermi-Detected Blazars

    Directory of Open Access Journals (Sweden)

    Böttcher Markus

    2013-12-01

    Full Text Available We describe new implementations of leptonic and hadronic models for the broadband emission from relativistic jets in AGN in a temporary steady state. The new model implementations are used to fit snap-shot spectral energy distributions of a representative set of Fermi-LAT detected blazars from the first LAT AGN catalogue. We find that the leptonic model is capable of producing acceptable fits to the SEDs of almost all blazars with reasonable parameters close to equipartition between the magnetic field and the relativistic electron population. If charge neutrality in leptonic models is provided by cold protons, our fits indicate that the kinetic energy carried by the jet should be dominated by protons. We also find satisfactory representations of the snapshot SEDs of most blazars in our sample with the hadronic model presented here. All of our hadronic model fits require powers in relativistic protons in the range 1047 – 1049 erg/s. As a potential way to distinguish between the leptonic and hadronic high-energy emission models considered here, we suggest diagnostics based on the predicted X-ray and γ-ray polarization, which are drastically different for the two types of models.

  14. 2WHSP: A multi-frequency selected catalog of VHE gamma-ray blazars and blazar candidates

    Science.gov (United States)

    Chang, Yu Lin; Arsioli, Bruno; Giommi, Paolo; Padovani, Paolo

    2016-08-01

    High Synchrotron Peaked Blazars (HSPs) are extremely important for VHE astronomy. We built the largest existing catalog of High Synchrotron Blazars (2WHSP) based on multi-frequency data. The catalog is an extension of the 1WHSP list. We compared several general properties of HSPs such as the synchrotron peak, the redshift and IR the color-color diagram. We also built the logN-logS for the sources, trying to see the evolution and the deficiency of the catalog. The catalog will provide a unique sample of targets for VHE observations in future since the HSPs are the dominant extra-Galactic sources in VHE sky. This might help find more VHE sources later. In the future, we will use this catalog to estimate other VHE properties of HSPs.

  15. The Correlation between -Ray and Radio Emissions for the Fermi Blazars

    Indian Academy of Sciences (India)

    J. H. Yang; J. H. Fan

    2011-03-01

    Based upon the Fermi blazars sample, the radio and -ray emissions are compiled for a sample of 74 -ray loud blazars to calculate the radio to -ray effective spectrum index R . The correlations between R and -ray luminosity, and between radio and -ray luminosity are also investigated.

  16. The Extremes in Intra-Night Blazar Variability: The S4 0954+65 Case

    CERN Document Server

    Bachev, Rumen; Semkov, Evgeni; Dimitrova, Rosa Victoria Muñoz; Latev, Georgi; Spassov, Borislav; Petrov, Blagovest

    2016-01-01

    We present results of optical observations of the extremely violently variable blazar S4 0954+65 on intra-night time scales. The object showed flux changes of up to 100% within a few hours. Time delays between optical bands, color changes and "rms-flux" relations are investigated and the results are discussed in terms of existing models of blazar variability.

  17. Correlation between Spectral Index and Doppler Factor for a Sample of Fermi Blazars

    Indian Academy of Sciences (India)

    J. Tao; J. H. Fan; H. J. Pan; D. X. Wu; S. H. Li

    2014-09-01

    Relativistic beaming effect is important for blazars. In a very recent work, -ray Doppler factors were calculated for a sample of Fermi blazars (Fan et al. 2013). In this work, we investigated the correlation between the Doppler factor and the effective spectral index, 4OX, and found an anticorrelation between them.

  18. The contribution of blazars to the extragalactic diffuse gamma-ray background

    DEFF Research Database (Denmark)

    Mücke, A.; Pohl, M.; Dermer, C.D.

    1997-01-01

    We present results of a calculation of the blazar contribution to the extragalactic diffuse gamma-ray background (EGRB) in the EGRET-energy range. Our model is based on the non-thermal emission processes known to be important in blazar jets, and on the unification scheme of radio-loud AGN. The...

  19. A search of CO emission lines in blazars: the low molecular gas content of BL Lac objects compared to quasars

    CERN Document Server

    Fumagalli, Michele; Furniss, Amy; Prochaska, J Xavier; Williams, David; Kaplan, Kyle; Hogan, Matthew

    2012-01-01

    BL Lacertae (Lac) objects that are detected at very-high energies (VHE) are of fundamental importance to study multiple astrophysical processes, including the physics of jets, the properties of the extragalactic background light and the strength of the intergalactic magnetic field. Unfortunately, since most blazars have featureless optical spectra that preclude a redshift determination, a substantial fraction of these VHE extragalactic sources cannot be used for cosmological studies. To assess whether molecular lines are a viable way to establish distances, we have undertaken a pilot program at the IRAM 30m telescope to search for CO lines in three BL Lac objects with known redshifts. We report a positive detection of M_H2 ~ 3x10^8 Msun toward 1ES 1959+650, but due to the poor quality of the baseline, this value is affected by a large systematic uncertainty. For the remaining two sources, W Comae and RGB J0710+591, we derive 3sigma upper limits at, respectively, M_H2 < 8.0x10^8 Msun and M_H2 < 1.6x10^9 ...

  20. Time-Resolved Spectral Analysis of Blazar 0716+714

    Science.gov (United States)

    Diaz, Rosamaria; Harp, Gerald

    2016-01-01

    As electromagnetic (EM) waves from sources such as blazars travel through the intergalactic medium (IGM), they are slowed by electrons; a phenomenon called dispersion delay [2]. We study the propagation effects in emissions of EM waves from blazar source BL 0716+714 by estimating the average electron density, or dispersion measure (DM), of the IGM on a line of sight to the blazar. Measuring the variations in these effects with time allow us to understand the properties of the intervening material. Toward this goal we analyzed months of archived observations of BL 0716+714 taken by the Allen Telescope Array (ATA). The ATA's correlator produces cross-power vs. frequency spectra for every baseline (distance between a pair of antennas) in ten-second intervals. To reduce this immense load of data we used a technique based on interferometry called bispectrum, which does not depend on complicated array calibration and simplifies our work. The bispectrum multiplies baselines, three at a time, so that they form a closed loop, then the cube root of spectra are averaged [1]. This technique is independent of phase errors associated with any individual antenna and has a better SNR ratio than simply taking the average of all the baselines. We developed a numerical analysis program that takes in archived blazar files containing correlation data, computes the bispectrum, and outputs FITS images for each day of observations. The results show that our observations do not have sufficient sensitivity to reveal blazar variations in the frequency ranges that were studied. It is suggested that future observations at higher frequencies and/or with another telescope having greater sensitivity would reveal the time/frequency dependence of emission structure that would allow measurements of electron content. This work shows that but bispectrum is a useful tool for rapid characterization of interferometer data that does not require interferometer caclibration which could introduce artifacts

  1. Systematic Study of Gamma-ray bright Blazars with Optical Polarization and Gamma-ray Variability

    CERN Document Server

    Itoh, Ryosuke; Fukazawa, Yasushi; Uemura, Makoto; Tanaka, Yasuyuki T; Kawabata, Koji S; Madejski, Grzegorz M; Schinzel, Frank K; Kanda, Yuka; Shiki, Kensei; Akitaya, Hiroshi; Kawabata, Miho; Moritani, Yuki; Nakaoka, Tatsuya; Ohsugi, Takashi; Sasada, Mahito; Takaki, Katsutoshi; Takata, Koji; Ui, Takahiro; Yamanaka, Masayuki; Yoshida, Michitoshi

    2016-01-01

    Blazars are highly variable active galactic nuclei which emit radiation at all wavelengths from radio to gamma-rays. Polarized radiation from blazars is one key piece of evidence for synchrotron radiation at low energies and it also varies dramatically. The polarization of blazars is of interest for understanding the origin, confinement, and propagation of jets. However, even though numerous measurements have been performed, the mechanisms behind jet creation, composition and variability are still debated. We performed simultaneous gamma-ray and optical photopolarimetry observations of 45 blazars between Jul. 2008 and Dec. 2014 to investigate the mechanisms of variability and search for a basic relation between the several subclasses of blazars. We identify a correlation between the maximum degree of optical linear polarization and the gamma-ray luminosity or the ratio of gamma-ray to optical fluxes. Since the maximum polarization degree depends on the condition of the magnetic field (chaotic or ordered), thi...

  2. The Gamma-ray Blazar Quest: new optical spectra, state of art and future perspectives

    CERN Document Server

    Massaro, F; D'Abrusco, R; Landoni, M; Masetti, N; Ricci, F; Milisavljevic, D; Paggi, A; Chavushyan, V; Jiménez-Bailón, E; Patiño-Álvarez, V; Strader, J; Chomiuk, L; La Franca, F; Smith, Howard A; Tosti, G

    2016-01-01

    We recently developed a procedure to recognize gamma-ray blazar candidates within the positional uncertainty regions of the unidentified/unassociated gamma-ray sources (UGSs). Such procedure was based on the discovery that Fermi blazars show peculiar infrared colors. However, to confirm the real nature of the selected candidates, optical spectroscopic data are necessary. Thus, we performed an extensive archival search for spectra available in the literature in parallel with an optical spectroscopic campaign aimed to reveal and confirm the nature of the selected gamma-ray blazar candidates. Here, we first search for optical spectra of a selected sample of gamma-ray blazar candidates that can be potential counterparts of UGSs using the Sloan Digital Sky Survey (SDSS DR12). This search enables us to update the archival search carried out to date. We also describe the state-of-art and the future perspectives of our campaign to discover previously unknown gamma-ray blazars.

  3. Extended Radio Emission in MOJAVE Blazars: Challenges to Unification

    Science.gov (United States)

    Kharb, P.; Lister, M. L.; Cooper, N. J.

    2010-02-01

    We present the results of a study on the kiloparsec-scale radio emission in the complete flux density limited MOJAVE sample, comprising 135 radio-loud active galactic nuclei. New 1.4 GHz Very Large Array (VLA) radio images of six quasars and previously unpublished images of 21 blazars are presented, along with an analysis of the high-resolution (VLA A-array) 1.4 GHz emission for the entire sample. While extended emission is detected in the majority of the sources, about 7% of the sources exhibit only radio core emission. We expect more sensitive radio observations, however, to detect faint emission in these sources, as we have detected in the erstwhile "core-only" source, 1548+056. The kiloparsec-scale radio morphology varies widely across the sample. Many BL Lac objects exhibit extended radio power and kiloparsec-scale morphology typical of powerful FRII jets, while a substantial number of quasars possess radio powers intermediate between FRIs and FRIIs. This poses challenges to the simple radio-loud unified scheme, which links BL Lac objects to FRIs and quasars to FRIIs. We find a significant correlation between extended radio emission and parsec-scale jet speeds: the more radio powerful sources possess faster jets. This indicates that the 1.4 GHz (or low-frequency) radio emission is indeed related to jet kinetic power. Various properties such as extended radio power and apparent parsec-scale jet speeds vary smoothly between different blazar subclasses, suggesting that, at least in terms of radio jet properties, the distinction between quasars and BL Lac objects, at an emission-line equivalent width of 5 Å, is essentially an arbitrary one. While the two blazar subclasses display a smooth continuation in properties, they often reveal differences in the correlation test results when considered separately. This can be understood if, unlike quasars, BL Lac objects do not constitute a homogeneous population, but rather include both FRI and FRII radio galaxies for

  4. RoboPol: Unveiling the Physics of Blazar Jets from Skinakas

    Science.gov (United States)

    Pavlidou, V.

    2016-06-01

    Blazars are powered by relativistic jets and radiate exclusively through extreme, nonthermal particle interactions, energized by accretion onto supermassive black holes. Despite intensive observational and theoretical efforts over the last four decades, the details of blazar astrophysics remain elusive. The launch of NASA's Fermi Gammaray Space Telescope in 2008 provided an unprecedented opportunity for the systematic study of blazar jets and has prompted large-scale blazar monitoring efforts across wavelengths. In such a multi-wavelength campaign, a novel effect was discovered: fast changes in the optical polarization during gamma-ray flares. Optical emission from blazars is significantly polarized and the polarization probes the magnetic field structure in the jet. For this reason, such polarization rotations reveal important information about the evolution of disturbances responsible for blazar flares. The RoboPol program for the polarimetric monitoring of statistically complete samples of blazars was developed in 2013 to systematically study this class of events. RoboPol is a collaboration between the University of Crete, Caltech, the Max-Planck Institute for Radio Astronomy, the Inter-University Centre for Astronomy and Astrophysics in India, and the Nicolaus Copernicus University in Poland. Using a novel polarimeter operating at the 1.3m telescope of the Skinakas Observatory in Crete, it has succeeded in its 3 years of operation in taking optopolarimetric rotations of blazars from novelty status to a well-studied phenomenon that can be used to answer long-standing questions in our theoretical understanding of jets. We review the RoboPol program and its most important results in the classification of the optopolarimetric properties of blazars, the statistical properties of polarization rotations, and their relation to gamma-ray activity in blazar jets.

  5. Long term lightcurve of the BL Lac object 1ES 0229+200 at TeV energies

    CERN Document Server

    Cologna, Gabriele; Wagner, Stefan J; Wierzcholska, Alicja; Romoli, Carlo; Kurtanidze, Omar

    2015-01-01

    The high-frequency peaked BL Lac object 1ES 0229+200 (z = 0.14) was first detected in very high energy (VHE, E > 100 GeV) $\\gamma$-rays by the H.E.S.S. (High Energy Stereoscopic System) collaboration in 2006. No flux variability was reported in the initial study and its spectral characteristics have been used to derive constraints on the extragalactic background light (EBL) and on the intergalactic magnetic field (IGMF). 1ES 0229+200 has been observed with H.E.S.S. for $\\sim$130 hours from 2004 to 2013: the full dataset analysed with a more sensitive method will be presented here. The results indicate that the source is not constant and displays flux variability on yearly and monthly timescales. The existence of flux variability affects the derivation of the constraints on the IGMF. The H.E.S.S. observations cover several simultaneous multi-frequency campaigns and the VHE variations are compared with those reported in different bands.

  6. Very High Energy $\\gamma$-ray and Near Infrared observations of 1ES2344+514 during 2004-05

    CERN Document Server

    Godambe, S V; Baliyan, K S; Tickoo, A K; Thoudam, S; Dhar, V K; Chandra, P; Yadav, K K; Venugopal, K; Bhatt, N; Bhattacharya, S; Chanchalani, K; Ganesh, S; Goyal, H C; Joshi, U C; Kaul, R K; Kothari, M; Kotwal, S; Koul, M K; Koul, R; Sahaynathan, S; Shah, C; Sharma, M

    2007-01-01

    We have observed the BL Lac object 1ES2344+514 (z = 0.044) in Very High Energy (VHE) gamma-ray and near-infrared wavelength bands with TACTIC and MIRO telescopes respectively. The observations were made from 18th October to 9th December 2004 and 27th October 2005 to 1st January 2006. Detailed analysis of the TACTIC data indicates absence of a statistically significant gamma-ray signal both in overall data and on a nightly basis from the source direction. We estimate an upper limit of I($\\geq$1.5 TeV)$\\leq 3.84 \\times 10^{-12}$ photons cm$^{-2}$ s$^{-1}$ at a 3$\\sigma$ confidence level on the integrated $\\gamma$-ray flux. In addition, we have also compared TACTIC TeV light curves with those of the RXTE ASM (2-12keV) for the contemporary period and find that there are no statistically significant increases in the signal strengths from the source in both these energy regions. During 2004 IR observations, 1ES2344+514 shows low level (~0.06 magnitude) day-to-day variation in both, J & H bands. However, during ...

  7. Discovery of Very High-Energy Gamma-Ray Radiation from the BL Lac 1ES 0806+524

    CERN Document Server

    Aliu, E; Bautista, M; Beilicke, M; Benbow, W; Böttcher, M; Bradbury, S M; Buckley, J H; Bugaev, V; Butt, Y; Byrum, K; Cannon, A; Celik, O; Cesarini, A; Chow, Y C; Ciupik, L; Cogan, P; Colin, P; Cui, W; Dickherber, R; Duke, C; Ergin, T; Falcone, A; Fegan, S J; Finley, J P; Finnegan, G; Fortin, P; Fortson, L; Furniss, A; Gall, D; Gibbs, K; Gillanders, G H; Grube, J; Guenette, R; Gyuk, G; Hanna, D; Hays, E; Holder, J; Horan, D; Hui, C M; Humensky, T B; Imran, A; Kaaret, Philip; Karlsson, N; Kertzman, M; Kieda, D; Kildea, J; Konopelko, A; Krawczynski, H; Krennrich, F; Lang, M J; Le Bohec, S; Maier, G; McCann, A; McCutcheon, M; Millis, J; Moriarty, P; Mukherjee, R; Nagai, T; Ong, R A; Otte, A N; Pandel, D; Perkins, J S; Petry, D; Pohl, M; Quinn, J; Ragan, K; Reyes, L C; Reynolds, P T; Roache, E; Rose, J; Schroedter, M; Sembroski, G H; Smith, A W; Steele, D; Swordy, S P; Theiling, M; Toner, J A; Valcarcel, L; Varlotta, A; Vasilev, V V; Wagner, R G; Wakely, S P; Ward, J E; Weekes, T C; Weinstein, A; White, R J; Williams, D A; Wissel, S; Wood, M; Zitzer, B

    2008-01-01

    The high-frequency-peaked BL-Lacertae object \\objectname{1ES 0806+524}, at redshift z=0.138, was observed in the very-high-energy (VHE) gamma-ray regime by VERITAS between November 2006 and April 2008. These data encompass the two-, and three-telescope commissioning phases, as well as observations with the full four-telescope array. \\objectname{1ES 0806+524} is detected with a statistical significance of 6.3 standard deviations from 245 excess events. Little or no measurable variability on monthly time scales is found. The photon spectrum for the period November 2007 to April 2008 can be characterized by a power law with photon index $3.6 \\pm 1.0_{\\mathrm{stat}} \\pm 0.3_{\\mathrm{sys}}$ between $\\sim$300 GeV and $\\sim$700 GeV. The integral flux above 300 GeV is $(2.2\\pm0.5_{\\mathrm{stat}}\\pm0.4_{\\mathrm{sys}})\\times10^{-12}\\:\\mathrm{cm}^{2}\\:\\mathrm{s}^{-1}$ which corresponds to 1.8% of the Crab Nebula flux. Non contemporaneous multiwavelength observations are combined with the VHE data to produce a broadband ...

  8. Relation between the "Double-Hump" Behavior in the Radio Band and the Broad-Line Luminosity for Blazars

    Institute of Scientific and Technical Information of China (English)

    Zhao-Hua Xie; Hong Dai; Jian-Ming Hao; Lei-Ming Du; Xiong Zhang

    2007-01-01

    The physics behind the spectral energy distribution (SED) of blazars remains open.We assembled 36 blazars to tackle the factors that control their SED. Now, many blazar spectra have the "double hump" feature in the radio and far-IR frequencies. For these a parameter,△, is created to characterize the behavior of the SED. We found a significant correlation between the broad-line luminosity (LBLR) and △. Because LBLR is an indicator of the accreting power of the source in blazars, we derived a linear correlation,△∝ (M)1/3. 18, which suggests that the SED of blazars may depend on the accretion rate, like that of BL Lac objects. We also found a significant correlation between (m) and△ for a sample of 11 blazars (out of one of 36)with available black hole masses. This implies the Eddington accretion ratio may influence the shape of the SED of blazars.

  9. The simultaneous low state spectral energy distribution of 1ES 2344+514 from radio to very high energies

    Science.gov (United States)

    Aleksić, J.; Antonelli, L. A.; Antoranz, P.; Asensio, M.; Backes, M.; Barres de Almeida, U.; Barrio, J. A.; Bednarek, W.; Berger, K.; Bernardini, E.; Biland, A.; Blanch, O.; Bock, R. K.; Boller, A.; Bonnefoy, S.; Bonnoli, G.; Borla Tridon, D.; Bretz, T.; Carmona, E.; Carosi, A.; Carreto Fidalgo, D.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Cossio, L.; Covino, S.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Caneva, G.; De Lotto, B.; Delgado Mendez, C.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Eisenacher, D.; Elsaesser, D.; Ferenc, D.; Fonseca, M. V.; Font, L.; Fruck, C.; García López, R. J.; Garczarczyk, M.; Garrido Terrats, D.; Gaug, M.; Giavitto, G.; Godinović, N.; González Muñoz, A.; Gozzini, S. R.; Hadamek, A.; Hadasch, D.; Herrero, A.; Hose, J.; Hrupec, D.; Jankowski, F.; Kadenius, V.; Klepser, S.; Knoetig, M. L.; Krähenbühl, T.; Krause, J.; Kushida, J.; La Barbera, A.; Lelas, D.; Leonardo, E.; Lewandowska, N.; Lindfors, E.; Lombardi, S.; López, M.; López-Coto, R.; López-Oramas, A.; Lorenz, E.; Lozano, I.; Makariev, M.; Mallot, K.; Maneva, G.; Mankuzhiyil, N.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martínez, M.; Masbou, J.; Mazin, D.; Meucci, M.; Miranda, J. M.; Mirzoyan, R.; Moldón, J.; Moralejo, A.; Munar-Adrover, P.; Nakajima, D.; Niedzwiecki, A.; Nieto, D.; Nilsson, K.; Nowak, N.; Orito, R.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Partini, S.; Persic, M.; Pilia, M.; Prada, F.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Reichardt, I.; Reinthal, R.; Rhode, W.; Ribó, M.; Rico, J.; Rügamer, S.; Saggion, A.; Saito, K.; Saito, T. Y.; Salvati, M.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schultz, C.; Schweizer, T.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Spanier, F.; Spiro, S.; Stamatescu, V.; Stamerra, A.; Steinke, B.; Storz, J.; Sun, S.; Surić, T.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Tibolla, O.; Torres, D. F.; Toyama, T.; Treves, A.; Uellenbeck, M.; Vogler, P.; Wagner, R. M.; Weitzel, Q.; Zandanel, F.; Zanin, R.; MAGIC Collaboration; Longo, F.; Lucarelli, F.; Pittori, C.; Vercellone, S.; AGILE Team; Bastieri, D.; Sbarra, C.; Fermi-LAT Collaboration; Angelakis, E.; Fuhrmann, L.; Nestoras, I.; Krichbaum, T. P.; Sievers, A.; Zensus, J. A.; F-GAMMA program; Antonyuk, K. A.; Baumgartner, W.; Berduygin, A.; Carini, M.; Cook, K.; Gehrels, N.; Kadler, M.; Kovalev, Yu. A.; Kovalev, Y. Y.; Krauss, F.; Krimm, H. A.; Lähteenmäki, A.; Lister, M. L.; Max-Moerbeck, W.; Pasanen, M.; Pushkarev, A. B.; Readhead, A. C. S.; Richards, J. L.; Sainio, J.; Shakhovskoy, D. N.; Sokolovsky, K. V.; Tornikoski, M.; Tueller, J.; Weidinger, M.; Wilms, J.

    2013-08-01

    Context. BL Lacertae objects are variable at all energy bands on time scales down to minutes. To construct and interpret their spectral energy distribution (SED), simultaneous broad-band observations are mandatory. Up to now, the number of objects studied during such campaigns is very limited and biased towards high flux states. Aims: We present the results of a dedicated multi-wavelength study of the high-frequency peaked BL Lacertae (HBL) object and known TeV emitter 1ES 2344+514 by means of a pre-organised campaign. Methods: The observations were conducted during simultaneous visibility windows of MAGIC and AGILE in late 2008. The measurements were complemented by Metsähovi, RATAN-600, KVA+Tuorla, Swift and VLBA pointings. Additional coverage was provided by the ongoing long-term F-GAMMA and MOJAVE programs, the OVRO 40-m and CrAO telescopes as well as the Fermi satellite. The obtained SEDs are modelled using a one-zone as well as a self-consistent two-zone synchrotron self-Compton model. Results: 1ES 2344+514 was found at very low flux states in both X-rays and very high energy gamma rays. Variability was detected in the low frequency radio and X-ray bands only, where for the latter a small flare was observed. The X-ray flare was possibly caused by shock acceleration characterised by similar cooling and acceleration time scales. MOJAVE VLBA monitoring reveals a static jet whose components are stable over time scales of eleven years, contrary to previous findings. There appears to be no significant correlation between the 15 GHz and R-band monitoring light curves. The observations presented here constitute the first multi-wavelength campaign on 1ES 2344+514 from radio to VHE energies and one of the few simultaneous SEDs during low activity states. The quasi-simultaneous Fermi-LAT data poses some challenges for SED modelling, but in general the SEDs are described well by both applied models. The resulting parameters are typical for TeV emitting HBLs

  10. 1ES 1113+432: Luminous, soft X-ray outburst from a nearby cataclysmic variable (AR Ursae Majoris)

    Science.gov (United States)

    Remillard, R. A.; Schachter, J. F.; Silber, A. D.; Slane, P.

    1994-01-01

    A remarkable X-ray transient from the Einstein Slew Survey, 1 ES 1113+432, is identified with a nearby, short-period cataclysmic variable. Wenzel (1993) has confirmed that the optical counterpart is the variable star, AR UMa (cataloged as 'semiregular'), erroneously reported 5.7 min southeast of the true position. One of the Einstein slew observations recorded a flux of 43 IPC counts/s, which is an order of magnitude above the flux observed from the brightest cataclysmic variables in other X-ray surveys. The outburst spectrum is extremely 'soft,' with an implied blackbody temperature of approximately 22 eV. The optical counterpart (V = 16.5) exhibits a strong UV component, TiO bands from an M star, and broadened Balmer emission lines. Optical states as bright as V approx. 13 were found on photographs from the Harvard Plate Library, confirming outburst behavior in the optical counterpart. The historical photographic record suggests that 1ES 1113+432 remains in a low-accretion state most of the time. Both of the soft X-ray spectrum and the transitions between high and low-accretion states are suggestive of the AM Her (magnetic) subclass. Photometric observations in the I band show 0.18 mag modulations at a period of 0.966 hr. These are interpreted as ellipsiodal variations in the secondary star for a binary period of 1.932 hr, which is near the lower boundary of the 'period gap' in the histogram, of orbital periods of accreting white dwarfs. Thus 1ES 1113+432 provides the rare opportunity to study a secondary star in a cataclysmic binary that has evolved through the period gap. The optical spectral features from the secondary imply a spectral type of approximately M6 and a distance of approximately 88 pc. The peak luminosity in the soft X-ray component (unabsorbed) is then estimated to be 3 X 10(exp 33) ergs/s, assuming emission from a blackbody slab with a temperature of 22 eV. While this luminosity is higher than previous measures of the soft X-ray component, it

  11. Lorentz factor distribution of blazars from the optical Fundamental Plane of black hole activity

    Science.gov (United States)

    Saikia, Payaswini; Körding, Elmar; Falcke, Heino

    2016-09-01

    Blazar radiation is dominated by a relativistic jet which can be modelled at first approximation using just two intrinsic parameters - the Lorentz factor Γ and the viewing angle θ. Blazar jet observations are often beamed due to relativistic effects, complicating the understanding of these intrinsic properties. The most common way to estimate blazar Lorentz factors needs the estimation of apparent jet speeds and Doppler beaming factors. We present a new and independent method of constructing the blazar Lorentz factor distribution, using the optical Fundamental Plane of black hole activity. The optical Fundamental Plane is a plane stretched out by both the supermassive black holes and the X-ray binaries, in the 3D space provided by their [O III] line luminosity, radio luminosity and black hole mass. We use the intrinsic radio luminosity obtained from the optical Fundamental Plane to constrain the boosting parameters of the VLBA Imaging and Polarimetry Survey blazar sample. We find a blazar bulk Lorentz factor distribution in the form of a power law as N(Γ) ∝ Γ-2.1 ± 0.4 for the Γ range of 1-40. We also discuss the viewing angle distribution of the blazars and the dependence of our results on the input parameters.

  12. Target of Opportunity observations of blazars with H.E.S.S.$\\ $

    CERN Document Server

    Cerruti, M; Chakraborty, N; Davids, I D; Füßling, M; Jankowsky, F; Lenain, J P; Meyer, M; Prokoph, H; Wagner, S; Zaborov, D; Zacharias, M

    2016-01-01

    The very high energy (VHE, E > 100 GeV) sky is dominated by blazars, radio-loud active galactic nuclei whose relativistic jet is closely aligned with the line of sight. Blazars are characterized by rapid variability at all wavelengths and thus an important part of the H.E.S.S. blazar program is devoted to target of opportunity (ToO) observations. H.E.S.S. triggers blazar ToOs on the basis of publicly available blazar observations at longer wavelengths (optical, X-rays, and $\\gamma$-rays), from private optical observations with the ATOM telescope, and from private communications by $\\gamma$-ray partners in the context of MoUs. In 2015, about 70 hours of H.E.S.S. data were taken in the form of blazar ToOs, which represents ~15$\\%$ of all extragalactic observations. In this contribution, we present the H.E.S.S. blazar ToO status, and we focus on two major results from the 2015 season: the detection of VHE emission from 3C 279 during the June 2015 flare, and the discovery of PKS 0736+017 as a new VHE quasar.

  13. INTEGRAL and Swift Observations of Blazars in Outburst

    OpenAIRE

    Pian, Elena; Foschini, Luigi; Ghisellini, Gabriele

    2007-01-01

    The blazars 3C 454.3, PKS 0537-441 and PKS 2155-304 are traditionally known to be among the most active sources of this class. They emit at all frequencies, up to the gamma-rays, and are good probes of multiwavelength nuclear variability. The first two have also luminous broad emission line regions. We have recently monitored them with various facilities, including Swift and INTEGRAL, and have interpreted their variations with models of non-thermal radiation from a relativistic jet. In partic...

  14. Visual Method for Spectral Energy Distribution Calculation of Blazars

    Indian Academy of Sciences (India)

    Y. Huang; J. H. Fan

    2014-09-01

    In this work, we propose to use `The Geometer’s Sketchpad’ to the fitting of a spectral energy distribution of blazar based on three effective spectral indices, RO, OX, and RX and the flux density in the radio band. It can make us to see the fitting in detail with both the peak frequency and peak luminosity given immediately. We used our method to those sources whose peak frequency and peak luminosity are given and found that our results are consistent with those given in the work of Sambruna et al. (1996).

  15. Optical and X-ray Variability of Blazars

    CERN Document Server

    Gupta, A C

    2015-01-01

    Here we report our recent results of variability studies in optical and X-ray bands of three blazars namely 3C 273, PKS 2155 - 304 and BL Lacertae with XMM-Newton. We found large amplitude optical to X-rays variability in 3C 273, and PKS 2155 - 304 on year time scale. In 3C 273, we noticed that synchrotron cooling and particle acceleration are at work at different epoch of observations. In PKS 2155 - 304, spectral energy distribution from optical to X-ray is fitted with LPPL (log parabolic + power law) model. In BL Lacertae, optical flux and degree of polarization were anti-correlated.

  16. Optical and X-ray Variability of Blazars

    Science.gov (United States)

    Gupta, A. C.

    Here we report our recent results of variability studies in optical and X-ray bands of three blazars namely 3C 273, PKS 2155 -- 304 and BL Lacertae with XMM-Newton. We found large amplitude optical to X-rays variability in 3C 273, and PKS 2155 -- 304 on year time scale. In 3C 273, we noticed that synchrotron cooling and particle acceleration are at work at different epoch of observations. In PKS 2155 -- 304, spectral energy distribution from optical to X-ray is fitted with LPPL (log parabolic + power law) model. In BL Lacertae, optical flux and degree of polarization were anti-correlated.

  17. Spectral Index Changes with Brightness for -Ray Loud Blazars

    Indian Academy of Sciences (India)

    J. H. Yang; R. S. Yang; J. J. Nie; J. H. Fan

    2014-09-01

    Based on Fermi 1FGL and 2FGL data, a sample of 572 -ray loud blazars are selected, in which each source has both -ray flux and spectral index in 1FGL and 2FGL, respectively. Theoretic relation of spectral index changes depending on -ray brightness is obtained. The correlations between the ratio of -ray flux densities and the differences of the -ray spectral indices are discussed for the three subclasses of HBL, LBL and FSRQs. Results show that the ratio is related with the differences for the three subclasses. It is consistent with the theoretical result and it indicates that the spectrum becomes flat as the source brightens in the -ray band.

  18. Photopolarimetry of Blazar 3C454.3 from MIRO

    Science.gov (United States)

    Baliyan, Ks; Ganesh, S.; Chandra, Sunil; Joshi, Uc

    2009-12-01

    The Blazar 3C 454.3 has been active in Gamma-rays, optical and X- rays since Sept. 2009 ( Atel #2181, #2200, #2201). Very recently, it has been reported to be flaring up in the optical, X-ray and gamma-ray energy regimes(ATel #2322; #2325; #2326; #2328; #2329; #2330; #2332). In Atel #2333, Sasada et al report optical behaviour of this source on Dec 1.9 with brightness (V=14.06+/-0.02 and degree of polarization 6.0+/-0.1% on the same epoch.

  19. VERITAS long-term (2006-2014) observations of the BL Lac object 1ES 0806+524

    CERN Document Server

    Cerruti, Matteo

    2015-01-01

    The discovery of the high-frequency-peaked BL Lac object 1ES 0806+524 (z=0.138) as a source of very-high-energy (VHE, E>100 GeV) gamma-ray photons was announced in 2008 by the VERITAS Collaboration, at a level of 1.8% of the Crab Nebula flux above 300 GeV. Since then, VERITAS has continued observing the source over multiple seasons, significantly improving the significance of the detection. We report the results of the analysis of the 2006-2014 VERITAS data, corresponding to a total exposure of about 70 hours. We present the new, average VHE spectrum of the source, together with the multi-year light-curve constraining long-term VHE variability.

  20. The gamma-ray Doppler factor determinations for a Fermi blazar sample

    Institute of Scientific and Technical Information of China (English)

    Jun-Hui Fan; Jiang-He Yang; Yi Liu; Jing-Yi Zhang

    2013-01-01

    Observations suggest that γ-ray loud blazars are strongly beamed.The Fermi mission has detected many of blazars,which provide us with a good opportunity to investigate the emission mechanism and the beaming effect in the γ-ray region.We compiled the X-ray observations for 138 Fermi blazars (54 flat spectrum radio quasars,36 low-peaked BL Lacertae objects,and 48 high-peaked BL Lacertae objects) and calculated their Doppler factors,δγ.It is interesting that the calculated Doppler factors,δγ,are strongly correlated with the γ-ray luminosity.

  1. Extragalactic radio source evolution & unification clues to the demographics of blazars

    CERN Document Server

    Jackson, C A

    2001-01-01

    In this paper we discuss the demographics of the radio blazar population: (i) what are their parent (`unbeamed') sources and (ii) what magnitude and/or type of evolution have they undergone ? The discussion is based on models of radio source evolution and beaming based on a `dual population' unification paradigm. These models, developed from radio blazar properties in bright samples, predict blazar demographic trends at the lower flux-density levels; samples from deep mJy-level surveys (e.g. NVSS and FIRST) may now provide direct tests of these predictions.

  2. RCT photometry and HCT spectroscopy of blazar candidates in the Kepler field of view

    Science.gov (United States)

    Carini, Michael T.; Goyal, A.; Jose, J.

    2014-01-01

    The results of photometric and spectroscopic monitoring of 9 blazar candidates in the Kepler field of view are presented. These sources were identified as blazar candidates based on their position in the so-called WISE blazar strip. Finding charts and comparison sequences were created using the NOMAD database. R band photometric monitoring was begun in spring 2013 with the Robotically Controlled Telescope(RCT), and spectroscopic observations of 7 of the sources were obtained with the Himalayan Chandra Telescope (HCT) in September, 2013. Light curves for all 9 sources and preliminary spectroscopic classifications for the 7 sources with spectra will be presented.

  3. Radio Variability of First 3-Month Fermi Blazars at 5 GHz: Affected by Interstellar Scintillation?

    Indian Academy of Sciences (India)

    X. Liu; Z. Ding; J. Liu; N. Marchili; T. P. Krichbaum

    2011-03-01

    Blazars from the first-three-months Fermi-AGN list were observed with the Urumqi 25-m radio telescope at 5 GHz in IDV (Intra-Day Variability) mode and inter-month observation mode. A significant correlation between the flux density at 5 GHz and the -ray intensity for the Fermi-LAT detected blazars is seen. There is a higher IDV detection rate in Fermi detected blazars than those reported for other samples. Stronger variability appears at lower galactic latitudes; IDV appears to be stronger in weaker sources, indicating that the variability is affected by interstellar scintillation.

  4. Correlated variability in the blazar 3C 454.3

    CERN Document Server

    Bonning, E W; Urry, C M; Buxton, M; Fossati, G; Maraschi, L; Coppi, P; Scalzo, R; Isler, J; Kaptur, A

    2008-01-01

    The blazar 3C 454.3 was revealed by the Fermi Gamma-ray Space Telescope to be in an exceptionally high flux state in July 2008. Accordingly, we performed a multi-wavelength monitoring campaign on this blazar using IR and optical observations from the SMARTS telescopes, optical, UV and X-ray data from the Swift satellite, and public-release gamma-ray data from Fermi. We find an excellent correlation between the IR, optical, UV and gamma-ray light curves, with a time lag of less than one day. The amplitude of the infrared variability is comparable to that in gamma-rays, and larger than at optical or UV wavelengths. The X-ray flux is not strongly correlated with either the gamma-rays or longer wavelength data. These variability characteristics find a natural explanation in the external Compton model, in which electrons with Lorentz factor gamma~10^(3-4) radiate synchrotron emission in the infrared-optical and also scatter accretion disk or emission line photons to gamma-ray energies, while much cooler electrons ...

  5. The TANAMI Multiwavelength Program: Dynamic SEDs of Southern Blazars

    CERN Document Server

    Krauß, Felicia; Kadler, Matthias; Ojha, Roopesh; Schulz, Robert; Trüstedt, Jonas; Edwards, Philip G; Stevens, Jamie; Ros, Eduardo; Baumgartner, Wayne; Beuchert, Tobias; Blanchard, Jay; Buson, Sara; Carpenter, Bryce; Dauser, Thomas; Falkner, Sebastian; Gehrels, Neil; Gräfe, Christina; Gulyaev, Sergei; Hase, Hayo; Horiuchi, Shinji; Kreikenbohm, Annika; Kreykenbohm, Ingo; Langejahn, Marcus; Leiter, Katharina; Lovell, Jim E J; Müller, Cornelia; Natusch, Tim; Nesci, Roberto; Pursimo, Tapio; Phillips, Chris; Plötz, Christian; Quick, Jonathan; Tzioumis, Anastasios K; Weston, Stuart

    2016-01-01

    Simultaneous broadband spectral and temporal studies of blazars are an important tool for investigating active galactic nuclei (AGN) jet physics. We study the spectral evolution between quiescent and flaring periods of 22 radio-loud AGN through multi-epoch, quasi-simultaneous broadband spectra. For many of these sources these are the first broadband studies. We use a Bayesian block analysis of \\Fermi/LAT light curves in order to determine time ranges of constant flux for constructing quasi-simultaneous SEDs. The shapes of the resulting 81 SEDs are described by two logarithmic parabolas and a blackbody spectrum where needed. For low states the peak frequencies and luminosities agree well with the blazar sequence, higher luminosity implying lower peak frequencies. This is not true for sources in a high state. The $\\gamma$-ray photon index in Fermi/LAT correlates with the synchrotron peak frequency in low and intermediate states. No correlation is present in high states. The black hole mass cannot be determined ...

  6. A Blazar-Like Radio Flare in Mrk 231

    CERN Document Server

    Reynolds, Cormac; O'Dea, Christopher; Hurley-Walker, Natasha; Wrobel, Joan

    2013-01-01

    Radio monitoring of the broad absorption line quasar (BALQSO) Mrk 231 from 13.9 GHz to 17.6 GHz detected a strong flat spectrum flare. Even though BALQSOs are typically weak radio sources, the 17.6 GHz flux density doubled in ~150 days, from ~135 mJy to ~270 mJy. It is demonstrated that the elapsed rise time in the quasar rest frame and the relative magnitude of the flare is typical of some of the stronger flares in blazars that are associated with the ejection of discrete components on parsec scales. The decay of a similar flare was found in a previous monitoring campaign at 22 GHz. We conclude that these flares are not rare and indicate the likely ejection of a new radio component that can be resolved from the core with Very Long Baseline Interferometry. The implication is that Mrk 231 seems to be a quasar in which the physical mechanism that produces the BAL wind is in tension with the emergence of a fledgling blazar.

  7. Seed Photon Fields of Blazars in the Internal Shock Scenario

    CERN Document Server

    Joshi, Manasvita; Boettcher, Markus

    2014-01-01

    We extend our approach of modeling spectral energy distribution (SED) and lightcurves of blazars to include external Compton (EC) emission due to inverse Compton scattering of an external anisotropic target radiation field. We describe the time-dependent impact of such seed photon fields on the evolution of multifrequency emission and spectral variability of blazars using a multi-zone time-dependent leptonic jet model, with radiation feedback, in the internal shock model scenario. We calculate accurate EC-scattered high-energy spectra produced by relativistic electrons throughout the Thomson and Klein-Nishina regimes. We explore the effects of varying the contribution of (1) a thermal Shakura-Sunyaev accretion disk, (2) a spherically symmetric shell of broad-line clouds, the broad line region (BLR), and (3) a hot infrared emitting dusty torus (DT), on the resultant seed photon fields. We let the system evolve to beyond the BLR and within the DT and study the manifestation of the varying target photon fields o...

  8. Optical flux behaviour of a sample of Fermi blazars

    Science.gov (United States)

    Marchesini, E. J.; Andruchow, I.; Cellone, S. A.; Combi, J. A.; Zibecchi, L.; Martí, J.; Romero, G. E.; Muñoz-Arjonilla, A. J.; Luque-Escamilla, P.; Sánchez-Sutil, J. R.

    2016-06-01

    Aims: We aim at investigating the time-behaviour of a sample of gamma-ray blazars. We present the results from a 13 month-long optical photometry monitoring campaign of the blazars PKS 0048-097, PKS 0754+100, [HB89] 0827+243, PKS 0851+202, PKS 1253-055, PKS 1510-089, PKS 1749+096, PKS 2230+114 and PKS 2251+158. Methods: We analyse the variability of each object, focusing on different time-scales (long term, short term, and microvariability), in an attempt to achieve a statistical comparison of the results. Results: After applying a geometric model to explain the variability results, we found that it is possible that a slight change in the direction of the jet generates the variations detected in some objects during this campaign. Differential photometry results used in the statistical analysis reported in Table 2 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/591/A21

  9. Shaping the GeV-spectra of bright blazars

    CERN Document Server

    Hunger, Lars

    2016-01-01

    The non-thermal spectra of jetted active galactic nuclei show a variety of shapes in their low- and high energy components. In some of the brightest Fermi-LAT blazars, prominent spectral breaks at a few GeV have been regularly detected, which is inconsistent with conventional cooling effects. We study the effects of continuous time-dependent injection of electrons into the jet with differing rates, durations, locations, and power-law spectral indices, and evaluate its impact on the ambient emitting particle spectrum at a given snapshot time in the framework of a leptonic blazar emission model. The emitting electron spectrum is calculated by Compton cooling the continuously injected electrons, where target photons are assumed to be provided by the accretion disk and broad line region. We calculate the non-thermal photon spectra produced by inverse Compton scattering of these external target radiation fields using the full Compton cross-section in the head-on approximation. By means of a comprehensive parameter...

  10. Long-term optical-infrared color variability of blazars

    CERN Document Server

    Zhang, Bing-Kai; Zhao, Xiao-Yun; Dai, Ben-Zhong

    2015-01-01

    The long-term optical and infrared color variability of blazars has been investigated with the SMARTS monitoring data. The sample in this study consists of 49 flat spectrum radio quasars and 22 BL Lac objects. The fractional variability amplitudes of each source have been calculated in both optical R band and infrared J band. Overall, the variability amplitudes of FSRQs are larger than those of BL Lac objects. The results also suggest that the variability amplitude of most FSRQs is larger at lower energy band (J band) than at higher one (R band), while the variability amplitude of BL Lacs are larger at higher energy band. Two types of blazars both display color variation along with the variability in brightness. However, they show different variation behaviors in general. With the whole data set, 35 FSRQs exhibit redder-when-brighter trends, and 11 FSRQs exhibit opposite trends; 11 BL Lacs follow bluer-when-brighter trends, and 7 BL Lacs follow opposite trends. The examination in detail shows that there are 1...

  11. Effect of Particle Acceleration Process on the Flare Characteristics of Blazars

    Indian Academy of Sciences (India)

    S. Bhattacharyya; S. Sahayanathan; C. L. Kaul

    2002-03-01

    Following the kinetic equation approach, we study the flare processes in blazars in the optical-to-X-ray region, considering energy dependent acceleration time-scale of electrons and synchrotron and adiabatic cooling as their dominant energy loss processes.

  12. RoboPol: Do optical polarization rotations occur in all blazars?

    CERN Document Server

    Blinov, D; Papadakis, I; Kiehlmann, S; Liodakis, I; Panopoulou, G V; Pearson, T J; Angelakis, E; Baloković, M; Hovatta, T; Joshi, V; King, O G; Kus, A; Kylafis, N; Mahabal, A; Marecki, A; Myserlis, I; Paleologou, E; Papamastorakis, I; Pazderski, E; Prabhudesai, S; Ramaprakash, A; Readhead, A C S; Reig, P; Tassis, K; Zensus, J A

    2016-01-01

    We present a new set of optical polarization plane rotations in blazars, observed during the third year of operation of RoboPol. The entire set of rotation events discovered during three years of observations is analysed with the aim of determining whether these events are inherent in all blazars. It is found that the frequency of the polarization plane rotations varies widely among blazars. This variation cannot be explained either by a difference in the relativistic boosting or by selection effects caused by a difference in the average fractional polarization. We conclude that the rotations are characteristic of a subset of blazars and that they occur as a consequence of their intrinsic properties.

  13. The jets-accretion relation, mass-luminosity relation in Fermi blazars

    Science.gov (United States)

    Yu, Xiaoling; Zhang, Xiong; Zhang, Haojing; Xiong, Dingrong; Li, Bijun; Cha, Yongjuan; Chen, Yongyun; Huang, Xia; Wang, Yuwei

    2015-05-01

    A sample of 111 Fermi blazars each with a well-established radio core luminosity, broad-line luminosity, bolometric luminosity and black hole mass has been compiled from the literatures. We present a significant correlation between radio core and broad-line emission luminosities that supports a close link between accretion processes and relativistic jets. Analysis reveals a relationship of which is consistant with theoretical predicted coefficient and supports that blazar jets are powered by energy extraction from a rapidly spinning Kerr black hole through the magnetic field provided by the accretion disk. Through studying the correlation between the intrinsic bolometric luminosity and the black hole mass, we find a relationship of which supports mass-luminosity relation for Fermi blazars derived in this work is a powerlaw relation similar to that for main-sequence stars. Finally, EVOLUTIONARY SEQUENCE OF BLAZARS is discussed.

  14. Patchy blazar heating: diversifying the thermal history of the intergalactic medium

    CERN Document Server

    Lamberts, Astrid; Pfrommer, Christoph; Puchwein, Ewald; Broderich, Avery E; Shalaby, Mohamad

    2015-01-01

    TeV-blazars potentially heat the intergalactic medium (IGM) as their gamma rays interact with photons of the extragalactic background light to produce electron-positron pairs, which lose their kinetic energy to the surrounding medium through plasma instabilities. This results in a heating mechanism that is only weakly sensitive to the local density, and therefore approximately spatially uniform, naturally producing an inverted temperature-density relation in underdense regions. In this paper we go beyond the approximation of uniform heating and quantify the heating rate fluctuations due to the clustered distribution of blazars and how this impacts on the thermal history of the IGM. We analytically compute a filtering function that relates the heating rate fluctuations to the underlying dark matter density field. We implement it in the cosmological code GADGET-3 and perform large scale simulations to determine the impact of inhomogeneous heating. We show that, because of blazar clustering, blazar heating is in...

  15. Quasi-Periodic Oscillations in the X-ray Light Curves of Blazars

    Indian Academy of Sciences (India)

    Paul J. Wiita

    2011-03-01

    Any quasi-periodic variations discovered in blazar light curves would contain important information on the location and nature of the processes within the emission regions. In non-blazar active galactic nuclei, particularly Seyfert galaxies, any such fluctuations are very likely to be associated with the accretion disks, but in blazars they would almost certainly have to emanate from jets. This brief review summarizes recent claims for the presence of quasi-periodic variability in the X-ray emission of several AGN, focusing on blazars. Although no individual claim of the presence of a QPO in AGN X-ray light curves is absolutely convincing, there are some good cases for the presence of QPOs, including the Narrow Line Seyfert 1 galaxy, RE J1034+396, the quasar, 3C 273 and the BL Lac, PKS 2155−304.

  16. Extremes of the jet-accretion power relation of blazars, as explored by NuSTAR

    CERN Document Server

    Sbarrato, T; Tagliaferri, G; Perri, M; Madejski, G M; Stern, D; Boggs, S E; Christensen, F E; Craig, W W; Hailey, C J; Harrison, F A; Zhang, W W

    2015-01-01

    Hard X-ray observations are crucial to study the non-thermal jet emission from high-redshift, powerful blazars. We observed two bright z>2 flat spectrum radio quasars (FSRQs) in hard X-rays to explore the details of their relativistic jets and their possible variability. S5 0014+81 (at z=3.366) and B0222+185 (at z=2.690) have been observed twice by the Nuclear Spectroscopic Telescope Array (NuSTAR) simultaneously with Swift/XRT, showing different variability behaviours. We found that NuSTAR is instrumental to explore the variability of powerful high-redshift blazars, even when no gamma-ray emission is detected. The two sources have proven to have respectively the most luminous accretion disk and the most powerful jet among known blazars. They are located at the extreme end of the jet-accretion disk relation previously found for gamma-ray detected blazars.

  17. Collision-induced magnetic reconnection and a unified interpretation of polarization properties of GRBs and blazars

    CERN Document Server

    Deng, Wei; Zhang, Bing; Li, Hui

    2016-01-01

    The jet composition and energy dissipation mechanism of Gamma-ray bursts (GRBs) and Blazars are fundamental questions which remain not fully understood. One plausible model is to interpret the $\\gamma$-ray emission of GRBs and optical emission of blazars as synchrotron radiation of electrons accelerated from the collision-induced magnetic dissipation regions in Poynting-flux-dominated jets. The polarization observation is an important and independent information to test this model. Based on our recent 3D relativistic MHD simulations of collision-induced magnetic dissipation of magnetically dominated blobs, here we perform calculations of the polarization properties of the emission in the dissipation region and apply the results to model the polarization observational data of GRB prompt emission and blazar optical emission. We show that the same numerical model with different input parameters can reproduce well the observational data of both GRBs and blazars, especially the $90^{\\circ}$ polarization angle (PA)...

  18. Herschel PACS and SPIRE observations of blazar PKS 1510-089: a case for two blazar zones

    CERN Document Server

    Nalewajko, Krzysztof; Madejski, Greg M; Exter, Katrina; Szostek, Anna; Szczerba, Ryszard; Kidger, Mark R; Lorente, Rosario

    2012-01-01

    We present the results of observations of blazar PKS 1510-089 with the Herschel Space Observatory PACS and SPIRE instruments, together with multiwavelength data from Fermi/LAT, Swift, SMARTS and SMA. The source was found in a quiet state, and its far-infrared spectrum is consistent with a power-law with a spectral index of alpha ~ 0.7. Our Herschel observations were preceded by two 'orphan' gamma-ray flares. The near-infrared data reveal the high-energy cut-off in the main synchrotron component, which cannot be associated with the main gamma-ray component in a one-zone leptonic model. This is because in such a model the luminosity ratio of the External-Compton and synchrotron components is tightly related to the frequency ratio of these components, and in this particular case an unrealistically high energy density of the external radiation would be implied. Therefore, we consider a well-constrained two-zone blazar model to interpret the entire dataset. In this framework, the observed infrared emission is asso...

  19. Herschel PACS and SPIRE Observations of Blazar PKS 1510-089: A Case for Two Blazar Zones

    Science.gov (United States)

    Nalewajko, Krzysztof; Sikora, Marek; Madejski, Greg M.; Exter, Katrina; Szostek, Anna; Szczerba, Ryszard; Kidger, Mark R.; Lorente, Rosario

    2012-11-01

    We present the results of observations of blazar PKS 1510-089 with the Herschel Space Observatory PACS and SPIRE instruments, together with multiwavelength data from Fermi/LAT, Swift, SMARTS, and Submillimeter Array. The source was found in a quiet state, and its far-infrared spectrum is consistent with a power law with a spectral index of α ~= 0.7. Our Herschel observations were preceded by two "orphan" gamma-ray flares. The near-infrared data reveal the high-energy cutoff in the main synchrotron component, which cannot be associated with the main gamma-ray component in a one-zone leptonic model. This is because in such a model the luminosity ratio of the external-Compton (EC) and synchrotron components is tightly related to the frequency ratio of these components, and in this particular case an unrealistically high energy density of the external radiation would be implied. Therefore, we consider a well-constrained two-zone blazar model to interpret the entire data set. In this framework, the observed infrared emission is associated with the synchrotron component produced in the hot-dust region at the supra-parsec scale, while the gamma-ray emission is associated with the EC component produced in the broad-line region at the sub-parsec scale. In addition, the optical/UV emission is associated with the accretion disk thermal emission, with the accretion disk corona likely contributing to the X-ray emission.

  20. CHARACTERIZING THE OPTICAL VARIABILITY OF BRIGHT BLAZARS: VARIABILITY-BASED SELECTION OF FERMI ACTIVE GALACTIC NUCLEI

    International Nuclear Information System (INIS)

    We investigate the use of optical photometric variability to select and identify blazars in large-scale time-domain surveys, in part to aid in the identification of blazar counterparts to the ∼30% of γ-ray sources in the Fermi 2FGL catalog still lacking reliable associations. Using data from the optical LINEAR asteroid survey, we characterize the optical variability of blazars by fitting a damped random walk model to individual light curves with two main model parameters, the characteristic timescales of variability τ, and driving amplitudes on short timescales σ-circumflex. Imposing cuts on minimum τ and σ-circumflex allows for blazar selection with high efficiency E and completeness C. To test the efficacy of this approach, we apply this method to optically variable LINEAR objects that fall within the several-arcminute error ellipses of γ-ray sources in the Fermi 2FGL catalog. Despite the extreme stellar contamination at the shallow depth of the LINEAR survey, we are able to recover previously associated optical counterparts to Fermi active galactic nuclei with E ≥ 88% and C = 88% in Fermi 95% confidence error ellipses having semimajor axis r < 8'. We find that the suggested radio counterpart to Fermi source 2FGL J1649.6+5238 has optical variability consistent with other γ-ray blazars and is likely to be the γ-ray source. Our results suggest that the variability of the non-thermal jet emission in blazars is stochastic in nature, with unique variability properties due to the effects of relativistic beaming. After correcting for beaming, we estimate that the characteristic timescale of blazar variability is ∼3 years in the rest frame of the jet, in contrast with the ∼320 day disk flux timescale observed in quasars. The variability-based selection method presented will be useful for blazar identification in time-domain optical surveys and is also a probe of jet physics.

  1. A Large NIR flare of the Blazar TXS 2241+406

    Science.gov (United States)

    Carrasco, L.; Gonzalez, R.; Recillas, E.; Porras, A.; Chavushyan, V.; Carraminana, A.

    2015-11-01

    We report on the recent NIR flare of the Blazar BZBJ2244+4057 a high redshift blazar (z=1.171) associated with the Gamma-ray source 2FGLJ 2244.1+4059, On November 22nd, 2015 (JD 2457348.654), We determined the flux from this object to correspond to J = 13.414 +/- 0.04, H = 12.580 +/- 0.06 and Ks = 11.774 +/- 0.06.

  2. Are Radio-Loud Narrow-Line Seyfert 1 Galaxies Blazar-like?

    Indian Academy of Sciences (India)

    Renyi Ma; Chong Ping

    2014-09-01

    The similarities between blazars and radio-loud narrow-line Seyfert 1 galaxies (RLNLS1s) have received much attention. In this paper, by using the magnetized slim disk model, we calculate the jet power and disk luminosity. It is found that the jet power is only a very small fraction of the disk luminosity, < 10%. This indicates that the jet orientation of RLNLS1 is close to the line-of-sight, which is similar to blazars.

  3. A recent strong X-ray flaring activity of 1ES 1959+650 with possibly less efficient stochastic acceleration

    Science.gov (United States)

    Kapanadze, B.; Dorner, D.; Vercellone, S.; Romano, P.; Kapanadze, S.; Mdzinarishvili, T.

    2016-09-01

    We present an X-ray flaring activity of 1ES 1959+650 in 2015 August-2016 January, which was the most powerful and prolonged during the 10.75 yr period since the start of its monitoring with X-ray Telescope onboard Swift. A new highest historical 0.3-10 keV count rate was recorded three times that makes this object the third BL Lacertae source exceeding the level of 20 counts s-1. Along with the overall variability by a factor of 5.7, this epoch was characterized by fast X-ray flares by a factor of 2.0-3.1, accompanied with an extreme spectral variability. The source also shows a simultaneous flaring activity in the optical - UV and 0.3-100 GeV bands, although a fast γ-ray flare without significant optical - X-ray counterparts is also found. In contrast to the X-ray flares in the previous years, the stochastic acceleration seems be less important for the electrons responsible for producing X-ray emission during this flare that challenges the earlier suggestion that the electrons in the jets of TeV-detected BL Lacertae objects should undergo an efficient stochastic acceleration resulting in a lower X-ray spectral curvature.

  4. MAGIC observations of the February 2014 flare of 1ES 1011+496 and ensuing constraint of the EBL density

    CERN Document Server

    Ahnen, M L; Antonelli, L A; Antoranz, P; Babic, A; Banerjee, B; Bangale, P; de Almeida, U Barres; Barrio, J A; González, J Becerra; Bednarek, W; Bernardini, E; Biasuzzi, B; Bil, A; Blanch, O; Bonnefoy, S; Bonnoli, G; Borracci, F; Bretz, T; Carmona, E; Carosi, A; Chatterjee, A; Clavero, R; Colin, P; Colombo, E; Contreras, J L; Cortina, J; Covino, S; Da Vela, P; Dazzi, F; De Angelis, A; De Lotto, B; Wilhelmi, E de O na; Mendez, C Delgado; Di Pierro, F; Prester, D Dominis; Dorner, D; Doro, M; Einecke, S; Glawion, D Eisenacher; Elsaesser, D; Fernández-Barral, A; Fidalgo, D; Fonseca, M V; Font, L; Frantzen, K; Fruck, C; Galindo, D; López, R J García; Garczarczyk, M; Terrats, D Garrido; Gaug, M; Giammaria, P; Godinovic, N; Muñoz, A González; Guberman, D; Hahn, A; Hanabata, Y; Hayashida, M; Herrera, J; Hose, J; Hrupec, D; Hughes, G; Idec, W; Kodani, K; Konno, Y; Kubo, H; Kushida, J; La Barbera, A; Lelas, D; Lindfors, E; Lombardi, S; Longo, F; López, M; López-Coto, R; López-Oramas, A; Lorenz, E; Majumdar, P; Makariev, M; Mallot, K; Maneva, G; Manganaro, M; Mannheim, K; Maraschi, L; Marcote, B; Mariotti, M; Martínez, M; Mazin, D; Menzel, U; Mira, J M; Mirzoyan, R; Moralejo, A; Moretti, E; Nakajima, D; Neustroev, V; Niedzwiecki, A; Rosillo, M Nievas; Nilsson, K; Nishijima, K; Noda, K; Orito, R; Overkemping, A; Paiano, S; Palacio, J; Palatiello, M; Paneque, D; Paoletti, R; Paredes, J M; Paredes-Fortuny, X; Persic, M; Poutanen, J; Moroni, P G Prada; Prini, E; Puljak, I; Rhode, W; Ribó, M; Rico, J; Garcia, J Rodriguez; Saito, T; Satalecka, K; Schultz, C; Schweizer, T; Shore, S N; Sillanpaa, A; Sitarek, J; Snidaric, I; Sobczynska, D; Stamerra, A; Steinbring, T; Strzys, M; Takalo, L; Takami, H; Tavecchio, F; Temnikov, P; Terzic, T; Tescaro, D; Teshima, M; Thaele, J; Torres, D F; Toyama, T; Treves, A; Verguilov, V; Vovk, I; Ward, J E; Will, M; Wu, M H; Zanin, R

    2016-01-01

    In February-March 2014, the MAGIC telescopes observed the high-frequency peaked BL Lac 1ES 1011+496 (z=0.212) in flaring state at very-high energy (VHE, E>100GeV). The flux reached a level more than 10 times higher than any previously recorded flaring state of the source. We present the description of the characteristics of the flare presenting the light curve and the spectral parameters of the night-wise spectra and the average spectrum of the whole period. From these data we aim at detecting the imprint of the Extragalactic Background Light (EBL) in the VHE spectrum of the source, in order to constrain its intensity in the optical band. For this we implement the method developed by the H.E.S.S. collaboration in which the intrinsic energy spectrum of the source is modeled with a simple function, and the EBL-induced optical depth is calculated using a template EBL model. The likelihood of the observed spectrum is then maximized, including a normalization factor for the EBL opacity among the free parameters. F...

  5. The Simultaneous Low State Spectral Energy Distribution of 1ES 2344+514 from Radio to Very High Energies

    CERN Document Server

    Longo, F; Pittori, C; Vercellone, S; Bastieri, D; Angelakis, E; Fuhrmann, L; Nestoras, I; Krichbaum, T P; Sievers, A; Antonyuk, K A; Baumgartner, W; Berduygin, A; Carini, M; Cook, K; Gehrels, N; Kadler, M; Kovalev, Yu A; Kovalev, Y Y; Krauss, F; Krimm, H A; Lähteenmäki, A; Lister, M L; Max-Moerbeck, W; Pasanen, M; Pushkarev, A B; Readhead, A C S; Richards, J L; Sainio, J; Shakhovskoy, D N; Sokolovsky, K V; Tornikoski, M; Tueller, J; Weidinger, M; Wilms, J

    2012-01-01

    [Abridged] Context. To construct and interpret the spectral energy distribution (SED) of BL Lacertae objects, simultaneous broad-band observations are mandatory. Aims. We intend to study the simultaneous broad-band emission of the high-frequency peaked BL Lac object and known TeV emitter 1ES 2344+514 by means of a pre-organised multi-wavelength campaign independently of the current flux state. By correlating the obtained light curves and describing the corresponding SEDs with state-of-the-art models we intend to derive physical parameters of the emission region. Methods. The observations were conducted during simultaneous visibility windows of MAGIC and AGILE in late 2008. The measurements were complemented by Mets\\"ahovi, RATAN-600, KVA+Tuorla, Swift and VLBA pointings. Additional coverage was provided by the ongoing long-term F-GAMMA and MOJAVE programs, the OVRO 40-m and CrAO telescopes as well as the Fermi satellite. The obtained SEDs are modelled using a one-zone as well as a self-consistent two-zone syn...

  6. Discovery of hard-spectrum \\gamma-ray emission from the BL Lac object 1ES 0414+009

    CERN Document Server

    Abramowski, A; Aharonian, F; Akhperjanian, A G; Anton, G; Balzer, A; Barnacka, A; de Almeida, U Barres; Becherini, Y; Becker, J; Behera, B; Bernlöhr, K; Birsin, E; Biteau, J; Bochow, A; Boisson, C; Bolmont, J; Bordas, P; Brucker, J; Brun, F; Brun, P; Bulik, T; Büsching, I; Carrigan, S; Casanova, S; Cerruti, M; Chadwick, P M; Charbonnier, A; Chaves, R C G; Cheesebrough, A; Chounet, L -M; Clapson, A C; Coignet, G; Cologna, G; Conrad, J; Dalton, M; Daniel, M K; Davids, I D; Degrange, B; Deil, C; Dickinson, H J; Djannati-Ataï, A; Domainko, W; Drury, L O'C; Dubois, F; Dubus, G; Dutson, K; Dyks, J; Dyrda, M; Egberts, K; Eger, P; Espigat, P; Fallon, L; Farnier, C; Feinstein, F; Fernandes, M V; Fiasson, A; Fontaine, G; Förster, A; Füßling, M; Gallant, Y A; Gast, H; Gérard, L; Gerbig, D; Giebels, B; Glicenstein, J F; Glück, B; Goret, P; Göring, D; Häffner, S; Hague, J D; Hampf, D; Hauser, M; Heinz, S; Heinzelmann, G; Henri, G; Hermann, G; Hinton, J A; Hoffmann, A; Hofmann, W; Hofverberg, P; Holler, M; Horns, D; Jacholkowska, A; de Jager, O C; Jahn, C; Jamrozy, M; Jung, I; Kastendieck, M A; Katarzynski, K; Katz, U; Kaufmann, S; Keogh, D; Khangulyan, D; Khélifi, B; Kluźniak, D Klochkov W; Kneiske, T; Komin, Nu; Kosack, K; Kossakowski, R; Laffon, H; Lamanna, G; Lennarz, D; Lohse, T; Lopatin, A; Lu, C -C; Marandon, V; Marcowith, A; Masbou, J; Maurin, D; Maxted, N; Mayer, M; McComb, T J L; Medina, M C; Méhault, J; Moderski, R; Moulin, E; Naumann, C L; Naumann-Godo, M; de Naurois, M; Nedbal, D; Nekrassov, D; Nguyen, N; Nicholas, B; Niemiec, J; Nolan, S J; Ohm, S; Wilhelmi, E de Ona; Opitz, B; Ostrowski, M; Oya, I; Panter, M; Arribas, M Paz; Pedaletti, G; Pelletier, G; Petrucci, P -O; Pita, S; Pühlhofer, G; Punch, M; Quirrenbach, A; Raue, M; Rayner, S M; Reimer, A; Reimer, O; Renaud, M; Reyes, R de los; Rieger, F; Ripken, J; Rob, L; Rosier-Lees, S; Rowell, G; Rudak, B; Rulten, C B; Ruppel, J; Sahakian, V; Sanchez, D A; Santangelo, A; Schlickeiser, R; Schöck, F M; Schulz, A; Schwanke, U; Schwarzburg, S; Schwemmer, S; Sheidaei, F; Sikora, M; Skilton, J L; Sol, H; Spengler, G; Stawarz, L; Steenkamp, R; Stegmann, C; Stinzing, F; Stycz, K; Sushch, I; Szostek, A; Tavernet, J -P; Terrier, R; Tluczykont, M; Valerius, K; van Eldik, C; Vasileiadis, G; Venter, C; Vialle, J P; Viana, A; Vincent, P; Völk, H J; Volpe, F; Vorobiov, S; Vorster, M; Wagner, S J; Ward, M; White, R; Wierzcholska, A; Zacharias, M; Zajczyk, A; Zdziarski, A A; Zech, A; Zechlin, H -S; Costamante, L; Fegan, S; Ajello, M

    2012-01-01

    1ES 0414+009 (z = 0.287) is a distant high-frequency-peaked BL Lac object, and has long been considered a likely emitter of very-high energy (VHE, E>100 GeV) gamma-rays due to its high X-ray and radio flux. Observations in the VHE gamma-ray band and across the electromagnetic spectrum can provide insights into the origin of highly energetic particles present in the source and the radiation processes at work. Because of the distance of the source, the gamma-ray spectrum might provide further limits on the level of the Extragalactic Background Light (EBL). We report observations made between October 2005 and December 2009 with H.E.S.S., an array of four imaging atmospheric Cherenkov telescopes. Observations at high energies (HE, 100 MeV - 100 GeV) with the Fermi-LAT instrument in the first 20 months of its operation are also reported. To complete the multi-wavelength picture, archival UV and X-ray observations with the Swift satellite and optical observations with the ATOM telescope are also used. Based on the ...

  7. COLLISION-INDUCED MAGNETIC RECONNECTION AND A UNIFIED INTERPRETATION OF POLARIZATION PROPERTIES OF GRBs AND BLAZARS

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Wei; Zhang, Bing [Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, NV 89154 (United States); Zhang, Haocheng; Li, Hui, E-mail: deng@physics.unlv.edu, E-mail: zhang@physics.unlv.edu, E-mail: hli@lanl.gov, E-mail: hz193909@ohio.edu [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2016-04-10

    The jet composition and energy dissipation mechanism of gamma-ray bursts (GRBs) and blazars are fundamental questions that remain not fully understood. One plausible model is to interpret the γ-ray emission of GRBs and optical emission of blazars as synchrotron radiation of electrons accelerated from the collision-induced magnetic dissipation regions in Poynting-flux-dominated jets. The polarization observation is an important and independent information to test this model. Based on our recent 3D relativistic MHD simulations of collision-induced magnetic dissipation of magnetically dominated blobs, here we perform calculations of the polarization properties of the emission in the dissipation region and apply the results to model the polarization observational data of GRB prompt emission and blazar optical emission. We show that the same numerical model with different input parameters can reproduce well the observational data of both GRBs and blazars, especially the 90° polarization angle (PA) change in GRB 100826A and the 180° PA swing in blazar 3C279. This supports a unified model for GRB and blazar jets, suggesting that collision-induced magnetic reconnection is a common physical mechanism to power the relativistic jet emission from events with very different black hole masses.

  8. High-energy sources at low radio frequency: the Murchison Widefield Array view of Fermi blazars

    CERN Document Server

    Giroletti, M; D'Abrusco, R; Lico, R; Burlon, D; Hurley-Walker, N; Johnston-Hollitt, M; Morgan, J; Pavlidou, V; Bell, M; Bernardi, G; Bhat, R; Bowman, J D; Briggs, F; Cappallo, R J; Corey, B E; Deshpande, A A; Ewall-Rice, A; Emrich, D; Gaensler, B M; Goeke, R; Greenhill, L J; Hazelton, B J; Hindson, L; Kaplan, D L; Kasper, J C; Kratzenberg, E; Feng, L; Jacobs, D; Kurdryavtseva, N; Lenc, E; Lonsdale, C J; Lynch, M J; McKinley, B; McWhirter, S R; Mitchell, D A; Morales, M F; Morgan, E; Oberoi, D; Offringa, A R; Ord, S M; Pindor, B; Prabu, T; Procopio, P; Riding, J; Rogers, A E E; Roshi, A; Shankar, N Udaya; Srivani, K S; Subrahmanyan, R; Tingay, S J; Waterson, M; Wayth, R B; Webster, R L; Whitney, A R; Williams, A; Williams, C L

    2016-01-01

    Low-frequency radio arrays are opening a new window for the study of the sky, both to study new phenomena and to better characterize known source classes. Being flat-spectrum sources, blazars are so far poorly studied at low radio frequencies. We characterize the spectral properties of the blazar population at low radio frequency compare the radio and high-energy properties of the gamma-ray blazar population, and search for radio counterparts of unidentified gamma-ray sources. We cross-correlated the 6,100 deg^2 Murchison Widefield Array Commissioning Survey catalogue with the Roma blazar catalogue, the third catalogue of active galactic nuclei detected by Fermi-LAT, and the unidentified members of the entire third catalogue of gamma-ray sources detected by \\fermilat. When available, we also added high-frequency radio data from the Australia Telescope 20 GHz catalogue. We find low-frequency counterparts for 186 out of 517 (36%) blazars, 79 out of 174 (45%) gamma-ray blazars, and 8 out of 73 (11%) gamma-ray bl...

  9. Major Optical Outburst of Two Blazars: 3C66A and OJ287

    Science.gov (United States)

    Ghosh, K. K.; Ramsey, B. D.; Soundararajaperumal, S.; Pukalenthi, S.; Rosario, M. J.

    1999-01-01

    Differential CCD photometric observations of 3C66A and OJ287 were carried out on 16 and 35 nights between December 1995 and March 1996, at the Vainu Bappu Observatory, India, as part of the blazar monitoring program. During this period we detected major optical outbursts (brightness of 3C66A and OJ287 increased by 0.8 and 1 mag, respectively) of these two blazars on timescales of two months. Integrating the outburst profiles we find that both the blazars released around 10(exp 53) erg. Such large amount of energy may come from the release of binding energy of a compact star when tidally disrupted by a super-massive black hole at the center of these blazars. Also we extend this model to explain the observed multifrequency (radio through gamma-ray) outburst of these two blazars and show that this model will be able to explain the outburst phenomena of other blazars. These new results will be presented with a detailed discussion of the suggested model.

  10. OPTICAL SPECTROSCOPIC OBSERVATIONS OF GAMMA-RAY BLAZAR CANDIDATES. V. TNG, KPNO, AND OAN OBSERVATIONS OF BLAZAR CANDIDATES OF UNCERTAIN TYPE IN THE NORTHERN HEMISPHERE

    Energy Technology Data Exchange (ETDEWEB)

    Álvarez Crespo, N.; Massaro, F. [Dipartimento di Fisica, Università degli Studi di Torino, via Pietro Giuria 1, I-10125 Torino (Italy); Masetti, N. [INAF—Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, via Gobetti 101, I-40129, Bologna (Italy); Ricci, F.; La Franca, F. [Dipartimento di Matematica e Fisica, Università Roma Tre, via della Vasca Navale 84, I-00146, Roma (Italy); Landoni, M. [INAF-Osservatorio Astronomico di Brera, Via Emilio Bianchi 46, I-23807 Merate (Italy); Patiño-Álvarez, V.; Chavushyan, V.; Torrealba, J. [Instituto Nacional de Astrofisica, Óptica y Electrónica, Apartado Postal 51-216, 72000 Puebla, México (Mexico); D’Abrusco, R.; Paggi, A.; Smith, Howard A. [Harvard—Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Jiménez-Bailón, E. [Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 877, Ensenada, 22800 Baja California, México (Mexico); Latronico, L. [Istituto Nazionale di Fisica Nucleare, Sezione di Torino, I-10125 Torino (Italy); Tosti, G. [Dipartimento di Fisica, Università degli Studi di Perugia, I-06123 Perugia (Italy)

    2016-02-15

    The extragalactic γ-ray sky is dominated by emission from blazars, a peculiar class of active galactic nuclei. Many of the γ-ray sources included in the Fermi-Large Area Telescope Third Source catalog (3FGL) are classified as blazar candidates of uncertain type (BCUs) because there are no optical spectra available in the literature to confirm their nature. In 2013, we started a spectroscopic campaign to look for the optical counterparts of the BCUs and of the unidentified γ-ray sources to confirm their blazar nature. Whenever possible we also determine their redshifts. Here, we present the results of the observations carried out in the northern hemisphere in 2013 and 2014 at the Telescopio Nazionale Galileo, Kitt Peak National Observatory, and Observatorio Astronómico Nacional in San Pedro Mártir. In this paper, we describe the optical spectra of 25 sources. We confirmed that all of the 15 BCUs observed in our campaign and included in our sample are blazars and we estimated the redshifts for three of them. In addition, we present the spectra for three sources classified as BL Lacs in the literature but with no optical spectra available to date. We found that one of them is a quasar (QSO) at a redshift of z = 0.208 and the other two are BL Lacs. Moreover, we also present seven new spectra for known blazars listed in the Roma-BZCAT that have an uncertain redshift or are classified as BL Lac candidates. We found that one of them, 5BZB J0724+2621, is a “changing look” blazar. According to the spectrum available in the literature, it was classified as a BL Lac, but in our observation we clearly detected a broad emission line that led us to classify this source as a QSO at z = 1.17.

  11. Location and origin of gamma-rays in blazars

    CERN Document Server

    Rani, B; Hodgson, J A; Zensus, J A

    2016-01-01

    One of the most intriguing and challenging quests of current astrophysics is to understand the physical conditions and processes responsible for production of high-energy particles, and emission of \\gamma-rays. A combination of high-resolution Very Long Baseline Interferometry (VLBI) images with broadband flux variability measurements is a unique way to probe the emission mechanisms at the bases of jets. Our analysis of \\gamma-ray flux variability observed by the Fermi-LAT (Large Area Telescope) along with the parsec-scale jet kinematics suggests that the $\\gamma$-ray emission in blazar S5 0716+714 has a significant correlation with the mm-VLBI core flux and the orientation of jet outflow on parsec scales. These results indicate that the inner jet morphology has a tight connection with the observed $\\gamma$-ray flares. An overview of our current understanding on high-energy radiation processes, their origin, and location is presented here.

  12. Particle-acceleration timescales in TeV blazar flares

    CERN Document Server

    Tammi, Joni

    2008-01-01

    Observations of minute-scale flares in TeV Blazars place constraints on particle acceleration mechanisms in those objects. The implications for a variety of radiation mechanisms have been addressed in the literature; in this paper we compare four different acceleration mechanisms: diffusive shock acceleration, second-order Fermi, shear acceleration and the converter mechanism. When the acceleration timescales and radiative losses are taken into account, we can exclude shear acceleration and the neutron-based converted mechanism as possible acceleration processes in these systems. The first-order Fermi process and the converter mechanism working via SSC photons are still practically instantaneous, however, provided sufficient turbulence is generated on the timescale of seconds. We propose stochastic acceleration as a promising candidate for the energy-dependent time delays in recent gamma-ray flares of Markarian 501.

  13. Implications of very rapid TeV variability in blazars

    CERN Document Server

    Begelman, Mitchell C; Rees, Martin J

    2007-01-01

    We discuss the implications of rapid (few-minute) variability in the TeV flux of blazars, which has been observed recently with the HESS and MAGIC telescopes. The variability timescales seen in PKS 2155-304 and Mrk 501 are much shorter than inferred light-crossing times at the black hole horizon, suggesting that the variability involves enhanced emission in a small region within an outflowing jet. The enhancement could be triggered by dissipation in part of the black hole's magnetosphere at the base of the outflow, or else by instabilities in the jet itself. By considering the energetics of the observed flares, along with the requirement that TeV photons escape without producing pairs, we deduce that the bulk Lorentz factors in the jets must be >50. The distance of the emission region from the central black hole is less well-constrained. We discuss possible consequences for multi-wavelength observations.

  14. Spectral evolution of flaring blazars from numerical simulations

    CERN Document Server

    Fromm, C M; Mimica, P; Ros, E

    2016-01-01

    High resolution Very Long Baseline Interferometry (VLBI) observations of Active Galactic Nuclei (AGN) revealed traveling and stationary or quasi-stationary radio-components in several blazar jets. The traveling ones are in general interpreted as shock waves generated by pressure perturbations injected at the jet nozzle. The stationary features can be interpreted as recollimation shocks in non-pressure matched jets if they show a quasi-symmetric bump in the spectral index distribution. In some jets there may be interactions between the two kinds of shocks. These shock--shock interactions are observable with VLBI techniques, and their signature should also be imprinted on the single--dish light curves. We performed relativistic hydrodynamic (RHD) simulations of over-pressured and pressure-matched jets. To simulate the shock interaction we injected a perturbation at the jet nozzle once a steady-state was reached. We computed the non-thermal emission (including adiabatic and synchotron losses) resulting from the ...

  15. Shaping the GeV-spectra of bright blazars

    Science.gov (United States)

    Hunger, L.; Reimer, A.

    2016-05-01

    Aims: The non-thermal spectra of jetted active galactic nuclei (AGN) show a variety of shapes and degrees of curvature in their low- and high energy components. From some of the brightest Fermi-LAT blazars, prominent spectral breaks at a few GeV have been regularly detected, which is inconsistent with conventional cooling effects. We study the effects of continuous time-dependent injection of electrons into the jet with differing rates, durations, locations, and power-law spectral indices, and evaluate its impact on the ambient emitting particle spectrum that is observed at a given snapshot time in the framework of a leptonic blazar emission model. With this study, we provide a basis for analyzing ambient electron spectra in terms of injection requirements, with implications for particle acceleration modes. Methods: The emitting electron spectrum is calculated by Compton cooling the continuously injected electrons, where target photons are assumed to be provided by the accretion disk and broad line region (BLR). From this setup, we calculate the non-thermal photon spectra produced by inverse Compton scattering of these external target radiation fields using the full Compton cross-section in the head-on approximation. Results: By means of a comprehensive parameter study we present the resulting ambient electron and photon spectra, and discuss the influence of each injection parameter individually. We found that varying the injection parameters has a notable influence on the spectral shapes, which in turn can be used to set interesting constraints on the particle injection scenarios. By applying our model to the flare state spectral energy distribution (SED) of 3C 454.3, we confirm a previous suggestion that explained the observed spectral changes at a few GeV by a combination of the Compton-scattered disk and BLR radiation. We determine the required injection parameters for this scenario. We also show that this spectral turn-over can also be understood as Compton

  16. Through the Looking Glass: Faraday Conversion in Turbulent Blazar Jets

    Directory of Open Access Journals (Sweden)

    Nicholas Roy MacDonald

    2016-10-01

    Full Text Available Faint levels of circular polarization (Stokes V have been detected in several relativistic jets. While typically less than a few percent, circular polarization can give us critical insight into the underlying nature of the jet plasma. Circular polarization can be produced through a process known as linear birefringence, in which initially linearly polarized emission produced in one region of the jet is altered by Faraday rotation as it propagates through other regions of the jet with distinct magnetic field orientations. Recently, Marscher has developed the Turbulent Extreme Multi-Zone (TEMZ model for blazar emission, in which turbulent plasma crossing a standing shock in the jet is represented by a collection of thousands of individual plasma cells, each with distinct magnetic field orientation. In order to test whether the TEMZ model can reproduce circularly polarized radiation at levels comparable to those observed in blazars, I have developed a numerical algorithm to solve the full Stokes equations of polarized radiative transfer. I have embedded this algorithm into the ray-tracing code RADMC3D (http://ascl.net/1202.015. RADMC3D was originally developed to model continuum radiative transfer in dusty media. This code, however, has been written in a modularized fashion that allows the user to specify the physics that is incorporated into the radiative transfer. I have replaced RADMC3D’s thermal emission and absorption coefficients with non-thermal coefficients pertaining to polarized synchrotron emission. This code is applied to ray-tracing through the 3-D TEMZ computational grid. Here I present a suite of synthetic polarized emission maps that highlight the effect that thousands of distinct cells of plasma within a jet can have on the observed linear and circular polarization.

  17. MAGIC observations of the February 2014 flare of 1ES 1011+496 and ensuing constraint of the EBL density

    Science.gov (United States)

    Ahnen, M. L.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Babic, A.; Banerjee, B.; Bangale, P.; Barres de Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Bernardini, E.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Carmona, E.; Carosi, A.; Chatterjee, A.; Clavero, R.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Lotto, B.; de Oña Wilhelmi, E.; Delgado Mendez, C.; Di Pierro, F.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher Glawion, D.; Elsaesser, D.; Fernández-Barral, A.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Frantzen, K.; Fruck, C.; Galindo, D.; García López, R. J.; Garczarczyk, M.; Garrido Terrats, D.; Gaug, M.; Giammaria, P.; Godinović, N.; González Muñoz, A.; Guberman, D.; Hahn, A.; Hanabata, Y.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Hughes, G.; Idec, W.; Kodani, K.; Konno, Y.; Kubo, H.; Kushida, J.; La Barbera, A.; Lelas, D.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; López-Coto, R.; López-Oramas, A.; Lorenz, E.; Majumdar, P.; Makariev, M.; Mallot, K.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Moretti, E.; Nakajima, D.; Neustroev, V.; Niedzwiecki, A.; Nievas Rosillo, M.; Nilsson, K.; Nishijima, K.; Noda, K.; Orito, R.; Overkemping, A.; Paiano, S.; Palacio, J.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Persic, M.; Poutanen, J.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Rhode, W.; Ribó, M.; Rico, J.; Rodriguez Garcia, J.; Saito, T.; Satalecka, K.; Schultz, C.; Schweizer, T.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Stamerra, A.; Steinbring, T.; Strzys, M.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Thaele, J.; Torres, D. F.; Toyama, T.; Treves, A.; Verguilov, V.; Vovk, I.; Ward, J. E.; Will, M.; Wu, M. H.; Zanin, R.

    2016-05-01

    Context. During February-March 2014, the MAGIC telescopes observed the high-frequency peaked BL Lac 1ES 1011+496 (z = 0.212) in flaring state at very-high energy (VHE, E> 100 GeV). The flux reached a level of more than ten times higher than any previously recorded flaring state of the source. Aims: To describe the characteristics of the flare presenting the light curve and the spectral parameters of the night-wise spectra and the average spectrum of the whole period. From these data we aim to detect the imprint of the extragalactic background light (EBL) in the VHE spectrum of the source, to constrain its intensity in the optical band. Methods: We analyzed the gamma-ray data from the MAGIC telescopes using the standard MAGIC software for the production of the light curve and the spectra. To constrain the EBL, we implement the method developed by the H.E.S.S. collaboration, in which the intrinsic energy spectrum of the source is modeled with a simple function (≤4 parameters), and the EBL-induced optical depth is calculated using a template EBL model. The likelihood of the observed spectrum is then maximized, including a normalization factor for the EBL opacity among the free parameters. Results: The collected data allowed us to describe the night-wise flux changes and also to produce differential energy spectra for all nights in the observed period. The estimated intrinsic spectra of all the nights could be fitted by power-law functions. Evaluating the changes in the fit parameters, we conclude that the spectral shape for most of the nights were compatible, regardless of the flux level, which enabled us to produce an average spectrum from which the EBL imprint could be constrained. The likelihood ratio test shows that the model with an EBL density 1.07 (-0.20, +0.24)stat+sys, relative to the one in the tested EBL template, is preferred at the 4.6σ level to the no-EBL hypothesis, with the assumption that the intrinsic source spectrum can be modeled as a log

  18. High-energy sources at low radio frequency: the Murchison Widefield Array view of Fermi blazars

    Science.gov (United States)

    Giroletti, M.; Massaro, F.; D'Abrusco, R.; Lico, R.; Burlon, D.; Hurley-Walker, N.; Johnston-Hollitt, M.; Morgan, J.; Pavlidou, V.; Bell, M.; Bernardi, G.; Bhat, R.; Bowman, J. D.; Briggs, F.; Cappallo, R. J.; Corey, B. E.; Deshpande, A. A.; Ewall-Rice, A.; Emrich, D.; Gaensler, B. M.; Goeke, R.; Greenhill, L. J.; Hazelton, B. J.; Hindson, L.; Kaplan, D. L.; Kasper, J. C.; Kratzenberg, E.; Feng, L.; Jacobs, D.; Kudryavtseva, N.; Lenc, E.; Lonsdale, C. J.; Lynch, M. J.; McKinley, B.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Oberoi, D.; Offringa, A. R.; Ord, S. M.; Pindor, B.; Prabu, T.; Procopio, P.; Riding, J.; Rogers, A. E. E.; Roshi, A.; Udaya Shankar, N.; Srivani, K. S.; Subrahmanyan, R.; Tingay, S. J.; Waterson, M.; Wayth, R. B.; Webster, R. L.; Whitney, A. R.; Williams, A.; Williams, C. L.

    2016-04-01

    Context. Low-frequency radio arrays are opening a new window for the study of the sky, both to study new phenomena and to better characterize known source classes. Being flat-spectrum sources, blazars are so far poorly studied at low radio frequencies. Aims: We characterize the spectral properties of the blazar population at low radio frequency, compare the radio and high-energy properties of the gamma-ray blazar population, and search for radio counterparts of unidentified gamma-ray sources. Methods: We cross-correlated the 6100 deg2 Murchison Widefield Array Commissioning Survey catalogue with the Roma blazar catalogue, the third catalogue of active galactic nuclei detected by Fermi-LAT, and the unidentified members of the entire third catalogue of gamma-ray sources detected by Fermi-LAT. When available, we also added high-frequency radio data from the Australia Telescope 20 GHz catalogue. Results: We find low-frequency counterparts for 186 out of 517 (36%) blazars, 79 out of 174 (45%) gamma-ray blazars, and 8 out of 73 (11%) gamma-ray blazar candidates. The mean low-frequency (120-180 MHz) blazar spectral index is ⟨αlow⟩ = 0.57 ± 0.02: blazar spectra are flatter than the rest of the population of low-frequency sources, but are steeper than at ~GHz frequencies. Low-frequency radio flux density and gamma-ray energy flux display a mildly significant and broadly scattered correlation. Ten unidentified gamma-ray sources have a (probably fortuitous) positional match with low radio frequency sources. Conclusions: Low-frequency radio astronomy provides important information about sources with a flat radio spectrum and high energy. However, the relatively low sensitivity of the present surveys still misses a significant fraction of these objects. Upcoming deeper surveys, such as the GaLactic and Extragalactic All-Sky MWA (GLEAM) survey, will provide further insight into this population. Tables 5-7 are only available at the CDS via anonymous ftp to http

  19. Peak of spectral energy distribution play an important role in intra-day variability of Blazars?

    CERN Document Server

    Gupta, Alok C; Gaur, Haritma; Duorah, Kalpana

    2016-01-01

    Blazars can be divided into two sub-classes namely high energy and low energy peaked blazars. In spectral energy distribution, the first synchrotron hump of the former class peaks in UV/X-rays and in IR/optical bands for the latter class. The peak of the spectral energy distribution seems to be responsible for variability properties of these classes of blazars in X-ray and optical bands. Since, in low energy peaked blazars, the X-ray bands lies well below the synchrotron hump, one expects that the highest energy electrons available for the synchrotron emission would have slower effect of variability on X-ray intra-day timescale. In this paper, by taking the advantage of a sample of 12 low energy peaked blazars with total 50 observations from XMM$-$Newton since its launch, we confirm that this class is less variable in X-ray bands. We found that out of 50 observational light curves, genuine intra-day variability is present in only two of light curves i.e 4%. Similar results we obtained from our earlier optical...

  20. Mining the Herschel-ATLAS: submillimeter-selected blazars in equatorial fields

    CERN Document Server

    López-Caniego, M; Massardi, M; Bonavera, L; Herranz, D; Negrello, M; De Zotti, G; Carrera, F J; Danese, L; Fleuren, S; Hardcastle, M; Jarvis, M J; Klöckner, H -R; Mauch, T; Procopio, P; Righini, S; Sutherland, W; Auld, R; Baes, M; Buttiglione, S; Clark, C J R; Cooray, A; Dariush, A; Dunne, L; Dye, S; Eales, S; Hopwood, R; Hoyos, C; Ibar, E; Ivison, R J; Maddox, S; Valiante, E

    2012-01-01

    The Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) provides an unprecedented opportunity to search for blazars at sub-mm wavelengths. We cross-matched the FIRST radio source catalogue with the 11655 sources brighter than 35 mJy at 500{\\mu}m in the \\sim 135 square degrees of the sky covered by the H-ATLAS equatorial fields at 9 h and 15 h, plus half of the field at 12 h. We found that 379 of the H-ATLAS sources have a FIRST counterpart within 10 arcsec, including 8 catalogued blazars (plus one known blazar that was found at the edge of one the H-ATLAS maps). To search for additional blazar candidates we have devised new diagnostic diagrams and found that known blazars occupy a region of the log(S500{\\mu}m/S350{\\mu}m) vs. log(S500{\\mu}m/S1.4GHz) plane separated from that of the other sub-mm sources with radio counterparts. Using this diagnostic we have selected 12 further candidates that turn out to be scattered in the (r-z) vs. (u-r) plane or in the WISE colour-colour diagram proposed by Massaro ...

  1. Variability of Spectral Energy Distribution of Blazar S5 0716+714

    Indian Academy of Sciences (India)

    B. Rani; Alok C. Gupta; Paul J. Wiita

    2011-03-01

    The emission from blazars is known to be variable at all wavelengths. The flux variability is often accompanied by spectral changes. Spectral energy distribution (SED) changes must be associated with changes in the spectra of emitting electrons and/or the physical parameters of the jet. Meaningful modeling of blazar broadband spectra is required to understand the extreme conditions within the emission region. Not only is the broadband SED crucial, but also information about its variability is needed to understand how the highest states of emission occur and how they differ from the low states. This may help in discriminating between models. Here we present the results of our SED modeling of the blazar S5 0716+714 during various phases of its activity. The SEDs are classified into different bins depending on the optical brightness state of the source.

  2. Blazar Studies with GLAST: Synchro-Compton Analysis of Flat Spectr um Radio Quasars

    CERN Document Server

    Dermer, Charles D; Krug, Hannah; Boettcher, Markus

    2008-01-01

    We extend a method for modeling synchrotron and synchrotron self-Compton radiations in blazar jets to include external Compton processes. The basic model assumption is that the blazar radio through soft X-ray flux is nonthermal synchrotron radiation emitted by isotropically-distributed electrons in the randomly directed magnetic field of outflowing relativistic blazar jet plasma. Thus the electron distribution is given by the synchrotron spectrum, depending only on the Doppler factor and mean magnetic field, given that the comoving emission region size scale. Generalizing the approach of Georganopoulos, Kirk, and Mastichiadis (2001) to arbitrary anisotropic target radiation fields, we use the electron spectrum implied by the synchrotron component to derive accurate Compton-scattered $\\gamma$-ray spectra throughout the Thomson and Klein-Nishina regimes for external Compton scattering (ECS) processes. We derive and calculate accurate $\\gamma$-ray spectra produced by relativistic electrons that Compton-scatter (...

  3. Resolving the blazar CGRaBS J0809+5341 in the presence of telescope systematics

    CERN Document Server

    Natarajan, Iniyan; Zwart, Jonathan; Perkins, Simon; Smirnov, Oleg; van der Heyden, Kurt

    2016-01-01

    We analyse Very Long Baseline Interferometry (VLBI) observations of the blazar CGRaBS J0809+5341 using Bayesian inference methods. The observation was carried out at 5 GHz using 8 telescopes that form part of the European VLBI Network. Imaging and deconvolution using traditional methods imply that the blazar is unresolved. To search for source structure beyond the diffraction limit, we perform Bayesian model selection between three source models (point, elliptical Gaussian, and circular Gaussian). Our modelling jointly accounts for antenna-dependent gains and system equivalent flux densities. We obtain posterior distributions for the various source and instrumental parameters along with the corresponding uncertainties and correlations between them. We find that there is very strong evidence (>1e9 :1) in favour of elliptical Gaussian structure and using this model derive the apparent brightness temperature distribution of the blazar, accounting for uncertainties in the shape estimates. To test the integrity of...

  4. Variability of Soft X-ray Spectral Shape in Blazars Observed by ROSAT

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In previous paper we have shown that the soft X-ray spectra of two types of Seyfert 1 galaxies behave statistically differently with increasing intensity.In order to see how the spectrum of blazars changes, we made plots of Hardness Ratio 1 versus Count Rates (HR1-Cts) for 18 blazars observed by ROSAT/PSPC.According to our criteria, ten showed a positive HR1-Cts correlation, two a negative correlation, and the remaining six, no clear correlation. Thus, most blazars of our sample show a hardening spectrum during overall flux increase, though some vary randomly. By investigating the photon index of these objects and different radiation theories, we argue that relative dominance between the synchrotron and inverse Compton emission in the soft X-ray band can well account for the differing spectral behaviours and that the different spectral variations might represent a sequence of synchrotron peaked frequency.

  5. FACT - Long-term Monitoring of Bright TeV-Blazars

    CERN Document Server

    Dorner, D; Bretz, T; Buss, J; Einecke, S; Eisenacher, D; Hildebrand, D; Knötig, M L; Krähenbühl, T; Lustermann, W; Mannheim, K; Meier, K; Neise, D; Overkemping, A -K; Paravac, A; Pauss, F; Rhode, W; Ribordy, M; Steinbring, T; Temme, F; Thaele, J; Walter, R; Weitzel, Q; Zänglein, M

    2013-01-01

    Since October 2011, the First G-APD Cherenkov Telescope (FACT) is operated successfully on the Canary Island of La Palma. Apart from the proof of principle for the use of G-APDs in Cherenkov telescopes, the major goal of the project is the dedicated long-term monitoring of a small sample of bright TeV blazars. The unique properties of G-APDs permit stable observations also during strong moon light. Thus a superior sampling density is provided on time scales at which the blazar variability amplitudes are expected to be largest, as exemplified by the spectacular variations of Mrk 501 observed in June 2012. While still in commissioning, FACT monitored bright blazars like Mrk 421 and Mrk 501 during the past 1.5 years so far. Preliminary results including the Mrk 501 flare from June 2012 will be presented.

  6. The relation between black hole masses and Lorentz factors of the jet components in blazars

    Institute of Scientific and Technical Information of China (English)

    Ming Zhou; Xin-Wu Cao

    2009-01-01

    We explore the relationship between black hole mass (MBH) and the motion of the jet components for a sample of blazars. The Very Long Baseline Array (VLBA) 2cm Survey and its continuation: Monitoring of Jets in active galactic nuclei (AGNs) with VLBA Experiments (MOJAVE) have observed 278 radio-loud AGNs, of which 146 blazars have reliable measurements of their apparent velocities of the jet components. We calculate the minimal Lorentz factors for these sources from their measured apparent velocities, and their black hole masses ate estimated with their broad-line widths. A sig-nificant intrinsic correlation is found between black hole masses and the minimal Lorentz factors of the jet components. The Eddington ratio is only weakly correlated with the min-imal Lorentz factor, which may imply that the Blandford-Znajek (BZ) mechanism may dominate over the Blandford-Payne (BP) mechanism for the jet acceleration (at least) in blazars.

  7. The influence of the magnetic field on the spectral properties of blazars

    CERN Document Server

    Rueda-Becerril, J M; Aloy, M A

    2013-01-01

    We explore the signature imprinted by dynamically relevant magnetic fields on the spectral energy distribution (SED) of blazars. It is assumed that the emission from these sources originates from the collision of ultrarelativistic and magnetized shells of cold plasma. A suitable analytic modeling, based on the numerical solution of Riemann problems, accounts for the magnetohydrodynamic evolution of the shell collisions. Using this dynamics we compute model SEDs including the most relevant radiative processes (synchrotron emission, synchrotron self-Compton and external inverse Compton scattering). To quantify the way in which the degree of magnetization shapes the SED, we scan a broad parameter space that encompasses a significant fraction of the commonly accepted values of not directly measurable physical properties. Starting from unmagnetized shell collisions, we reproduce the standard double hump SED found in blazar observations. We also show that the prototype double hump structure of blazars can also be r...

  8. Spectral trends in the Very High Energy blazar sample due to EBL absorption

    CERN Document Server

    Behera, B

    2009-01-01

    The absorption of gamma-rays in the intergalactic medium due to the EBL (Extragalactic Background Light) causes the observed blazar spectrum to be fainter and softer than their intrinsic state. It could thus be expected to see an effective spectral-softening trend with redshift. No such trend is evident in the sample of VHE blazars currently observed. To check which distributions of the properties of the parent blazar population could reproduce the observations, various simulations are done. The resulting subsamples that satisfy a generic detection criterion for the current generation of ACTs (Atmospheric Cherenkov Telescope) are checked to identify whether any inherent correlations (of spectral properties with redshift) are required to explain the current observations.

  9. NUSTAR, SWIFT, and GROND Observations of the Flaring MEV Blazar PMN J0641-0320

    DEFF Research Database (Denmark)

    Ajello, M.; Ghisellini, G.; Paliya, V. S.;

    2016-01-01

    MeV blazars are a sub-population of the blazar family, exhibiting larger-than-average jet powers, accretion luminosities, and black hole masses. Because of their extremely hard X-ray continua, these objects are best studied in the X-ray domain. Here, we report on the discovery by the Fermi Large...... Area Telescope and subsequent follow-up observations with NuSTAR, Swift, and GROND of a new member of the MeV blazar family: PMN J0641-0320. Our optical spectroscopy provides confirmation that this is a flat-spectrum radio quasar located at a redshift of z = 1.196. Its very hard NuSTAR spectrum (power...

  10. Peak of spectral energy distribution plays an important role in intra-day variability of blazars?

    Science.gov (United States)

    Gupta, Alok C.; Kalita, Nibedita; Gaur, Haritma; Duorah, Kalpana

    2016-10-01

    Blazars can be divided into two sub-classes namely high energy and low energy peaked blazars. In spectral energy distribution, the first synchrotron hump of the former class peaks in UV/X-rays and in IR/optical bands for the latter class. The peak of the spectral energy distribution seems to be responsible for variability properties of these classes of blazars in X-ray and optical bands. Since, in low energy peaked blazars, the X-ray bands lies well below the synchrotron hump, one expects that the highest energy electrons available for the synchrotron emission would have slower effect of variability on X-ray intra-day time-scale. In this paper, by taking the advantage of a sample of 12 low energy peaked blazars with total 50 observations from XMM-Newton since its launch, we confirm that this class is less variable in X-ray bands. We found that out of 50 observational light curves, genuine intra-day variability is present in only two of light curves i.e 4 per cent. Similar results we obtained from our earlier optical intra-day variability studies of high energy peaked blazars where out of 144 light curves, only genuine intra-day variability was detected in 6 light curves i.e ˜4 per cent. Since, X-ray bands lie below the peak of the spectral energy distribution of LSPs where inverse Compton mechanism is dominating rather than synchrotron radiation at the peak of the optical band, leads to slower variability in the X-ray bands. Hence, reducing their intra-day variability in X-ray bands as compared to the variability in optical bands.

  11. Long term variability of the blazar PKS 2155-304

    CERN Document Server

    Chevalier, Jill; Rieger, Frank; Maurin, Gilles; Lenain, Jean-Philippe; Lamanna, Giovanni

    2015-01-01

    Time variability of the photon flux is a known feature of active galactic nuclei (AGN) and in particular of blazars. The high frequency peaked BL Lac (HBL) object PKS 2155-304 is one of the brightest sources in the TeV band and has been monitored regularly with different instruments and in particular with the H.E.S.S. experiment above 200 GeV for more than 11 years. These data together with the observations of other instruments and monitoring programs like SMARTS (optical), Swift-XRT/RXTE/XMM-Newton (X-ray) and Fermi-LAT (100 MeV < E < 300 GeV) are used to characterize the variability of this object in the quiescent state over a wide energy range. Variability studies are made by looking at the lognormality of the light curves and at the fractional root mean square (rms) variability Fvar in several energy bands. Lognormality is found in every energy range and the evolution of Fvar with the energy shows a similar increase both in X-rays and in TeV bands.

  12. Blazars and gamma-ray cosmology: recent and prospective results

    Science.gov (United States)

    Biteau, Jonathan; Williams, David A.

    2016-01-01

    Blazars are dazzling gamma-ray beacons shedding light on some of the darkest mysteries of modern-day astroparticle physics. Some of these mysteries include the light content of the universe, including the UV-IR background, the emission of first stars and of organic molecules; large-scale magnetic fields and their potential primordial origin; spacetime structure, with the potential for Lorentz-invariance violations near the Planck scale; and the search for new interaction channels with photons, e.g. in the form of axion-like particles. These crucial scientific topics can be studied through the signatures of billion-year propagation of GeV-TeV gamma rays that reach Earth from astrophysical sources. We discuss how spectral imprints in data from ground-based and satellite experiments are beginning to answer some of the fundamental questions of gamma-ray cosmology. Recent results, obtained with increased datasets and advanced analysis techniques, are opening the path for future observatories. We examine the areas that remain to be explored, in particular by the proposed Cherenkov Telescope Array, CTA.

  13. Frequency-dependent core shifts and parameter estimation in Blazars

    Science.gov (United States)

    Agarwal, Aditi

    2016-07-01

    We study the core shift effect in the parsec-scale jet of blazars using the 4.8-36.8 GHz radio light curves obtained from four decades of continuous monitoring. From a piecewise Gaussian fit to each flare, time lags between the observation frequencies and spectral indices (α) based on peak amplitudes (A) are determined. Index k is calculated and found to be ˜1, indicating equipartition between the magnetic field energy density and the particle energy density. A mean magnetic field strength at 1 pc (B1) and at the core (Bcore) are inferred which are found to be consistent with previous estimates. The measure of core position offset is also performed by averaging over all frequency pairs. Based on the statistical trend shown by the measured core radius as a function of frequency, we infer that the synchrotron opacity model may not be valid for all cases. A Fourier periodogram analysis yields power-law slopes in the range -1.6 to -3.5 describing the power spectral density shape and gives bend timescales. This result, and both positive and negative spectral indices, indicate that the flares originate from multiple shocks in a small region. Important objectives met in our study include: the demonstration of the computational efficiency and statistical basis of the piecewise Gaussian fit; consistency with previously reported results; evidence for the core shift dependence on observation frequency and its utility in jet diagnostics in the region close to the resolving limit of very long baseline interferometry observations.

  14. Dissipation of jet bulk kinetic energy in powerful blazars

    CERN Document Server

    Katarzynski, K

    2006-01-01

    We investigate the dissipation of the bulk kinetic energy of a relativistic jet at different distances from the central power--house and analyse in detail how the dissipated energy is radiated away. We assume that the location of the dissipation region is a function of the bulk Lorentz factor Gamma of the jet, being closer to the center for smaller Gamma. This assumption is naturally fulfilled in the internal shock scenario. The dissipated energy is partially used to accelerate electrons and to amplify the magnetic field. This process creates a source inside the jet (blob). Such blobs may efficiently produce synchrotron and inverse Compton emission. We find that even if the blobs or shells responsible for the blazar activity carry the same energy (in bulk kinetic form), the fact that they move at different Gamma can produce dramatic variations in different bands, even if the bolometric luminosity is instead very similar. This is due to the relative importance of the synchrotron, self-Compton and external Comp...

  15. Spectroscopic monitoring of the Blazar 3C 454.3

    CERN Document Server

    Benítez, E; Raiteri, C M; Villata, M; Dultzin, D; Martínez, O; Perez-Camargo, B; Torrealba, J

    2009-01-01

    We performed an optical spectroscopic monitoring of the blazar 3C 454.3 from September 2003 to July 2008. Sixteen optical spectra were obtained during different runs, which constitute the first spectroscopic monitoring done in the rest-frame UV region (z=0.859). An overall flux variation of the MgII (2800 A) by a factor ~ 3 was observed, while the corresponding UV continuum (F_cont at 3000 A) changed by a factor ~ 14. The MgII emission lines respond proportionally to the continuum variations when the source is in a low-activity state. In contrast, near the optical outbursts detected in 2005 and 2007, the MgII emission lines showed little response to the continuum flux variations. During the monitored period the UV FeII flux changed by a factor ~ 6 and correlated with F_cont (r = 0.92). A negative correlation between EW(Mg II) and F_cont was found, i.e. the so-called "Intrinsic Baldwin Effect".

  16. Radio Variability and Random Walk Noise Properties of Four Blazars

    CERN Document Server

    Park, Jong-Ho

    2014-01-01

    We present the results of a time series analysis of the long-term radio lightcurves of four blazars: 3C 279, 3C 345, 3C 446, and BL Lacertae. We exploit the data base of the University of Michigan Radio Astronomy Observatory (UMRAO) monitoring program which provides densely sampled lightcurves spanning 32 years in time in three frequency bands located at 4.8, 8, and 14.5 GHz. Our sources show mostly flat or inverted (spectral indices -0.5 < alpha < 0) spectra, in agreement with optically thick emission. All lightcurves show strong variability on all time scales. Analyzing the time lags between the lightcurves from different frequency bands, we find that we can distinguish high-peaking flares and low-peaking flares in accord with the classification of Valtaoja et al. (1992). The periodograms (temporal power spectra) of the observed lightcurves are consistent with random-walk powerlaw noise without any indication of (quasi-)periodic variability. The fact that all four sources studied are in agreement with...

  17. An Investigation into the Spectral Properties of Bright Fermi Blazars

    CERN Document Server

    Harris, Jonathan; Daniel, Michael K

    2014-01-01

    We investigate the spectral properties of blazars detected with the Fermi-Large Area Telescope (LAT) in the high energy regime 100 MeV - 100 GeV. We find that over long timescales a log-parabola provides an adequate description of the spectrum in almost all objects and in most cases is significantly better than a simple power law or broken power law description. Broken power law descriptions appear to arise from two causes: confusion with nearby sources and as an artifact of older LAT instrument response functions. We create a light curve for 2FGLJ2253.9+1609 (3C 454.3), the brightest of the objects investigated. During the quiescent state we find the spectrum to be fairly stable and well-described by a log-parabola. There is some evidence that, on average, the peak energy of the inverse Compton emission is lower in the quiescent state than in the time-averaged state, suggesting that increases in flux are due to changing parameters within the jet as opposed to changes in an external photon field. However, no ...

  18. Multi-Band Spectral Properties of Fermi Blazars

    Indian Academy of Sciences (India)

    Benzhong Dai; Dahai Yan

    2011-03-01

    The multi-band data covering optical, X-ray and -ray energy regions of 130 Fermi blazars in the First LAT AGN Catalog (1LAC) were collected to investigate the broadband spectral properties. The composite spectral indices show that HBLs have convex optical-to-X-ray continua and concave X-ray-to--ray continua, > 0 and < 0, while FSRQs and LBLs have < 0. The distribution of FSRQs and LBLs extends from negative to positive values. We suggest > 0 and < 0 could be considered as a criterion for HBLs. Moreover, HBLs have narrow distribution of peak interval of log $v^{\\text{ic}}_{\\text{p}}=\\log v^{\\text{syn}}_{\\text{p}}$, and FSRQs have significant anti-correlation between log $v^{\\text{ic}}_{\\text{p}}-\\log v^{\\text{syn}}_{\\text{p}}$ and $\\log v^{\\text{syn}}_{\\text{p}}$. This indicates that SSC model is responsible for high energy emission of HBLs, while EC for FSRQs. Our results also indicate that FSRQs with larger break energy of electrons have smaller bulk Lorentz factor of dissipation region.

  19. On radiative acceleration in spine-sheath structured blazar jets

    CERN Document Server

    Chhotray, Atul; Ghisellini, Gabriele; Salafia, Om Sharan; Tavecchio, Fabrizio; Lazzati, Davide

    2016-01-01

    It has been proposed that blazar jets are structured, with a fast spine surrounded by a slower sheath or layer. This structured jet model explains some properties of their emission and morphology. Because of their relative motion, the radiation produced by one component is seen amplified by the other, thus enhancing the inverse Compton emission of both. Radiation is emitted anisotropically in the comoving frames, and causes the emitting plasma to recoil. As seen in the observer frame, this corresponds to a deceleration of the fastest component (the spine) and an acceleration of the slower one (the layer). While the deceleration of the spine has already been investigated, here we study for the first time the acceleration of the sheath and find self-consistent velocity profile solutions for both the spine and the sheath while accounting for radiative cooling. We find that the sheath can be accelerated to the velocities required by the observations if its leptons remain energetic in the acceleration region, assu...

  20. The red blazar PMN J2345-1555 becomes blue

    CERN Document Server

    Ghisellini, G; Foschini, L; Bonnoli, G; Tagliaferri, G

    2013-01-01

    The Flat Spectrum Radio Quasar PMN J2345-1555 is a bright gamma-ray source, that recently underwent a flaring episode in the IR, UV and gamma-ray bands. The flux changed quasi simultaneously at different frequencies, suggesting that it was produced by a single population of emitting particles, hence by a single and well localized region of the jet. While the overall Spectral Energy Distribution (SED) before the flare was typical of powerful blazars (namely two broad humps peaking in the far IR and below 100 MeV bands, respectively), during the flare the peaks moved to the optical-UV and to energies larger than 1 GeV, to resemble low power BL Lac objects, even if the observed bolometric luminosity increased by more than one order of magnitude. We interpret this behavior as due to a change of the location of the emission region in the jet, from within the broad line region, to just outside. The corresponding decrease of the radiation energy density as seen in the comoving frame of the jet allowed the relativist...

  1. Models for Very Rapid High-Energy -Ray Variability in Blazars

    Indian Academy of Sciences (India)

    G. E. Romero; M. M. Reynoso

    2014-09-01

    We present a family of models for rapid -ray variability in blazars based on a two-component jet. Fast variability occurs when relativistic electron–positron pairs interact with small-scale perturbations in the inner jet. These perturbations are produced by Kelvin–Helmholtz instabilities. We fit the minute-scale strong variability displayed by the blazar PKS 2155−304 and present synthetic light-curves of the kind that might be observed with forthcoming instruments such as the Cherenkov telescope array.

  2. Highly Variable Objects in the Palomar-QUEST Survey: A Blazar Search using Optical Variability

    OpenAIRE

    Bauer, Anne; Baltay, Charles; De Coppi, Paolo; Donalek, Ciro; Drake, Andrew; Djorgovski, S. G.; Ellman, Nancy; Glikman, Eilat; Graham, Matthew; Jerke, Jonathan; Mahabal, Ashish; Rabinowitz, David; Scalzo, Richard; Williams, Roy

    2009-01-01

    We identify 3113 highly variable objects in 7200 deg^2 of the Palomar-QUEST (PQ) Survey, which each varied by more than 0.4 mag simultaneously in two broadband optical filters on timescales from hours to roughly 3.5 years. The primary goal of the selection is to find blazars by their well-known violent optical variability. Because most known blazars have been found in radio and/or X-ray wavelengths, a sample discovered through optical variability may have very different selection effects, elu...

  3. TANAMI Blazars in the IceCube PeV Neutrino Fields

    CERN Document Server

    Krauß, F; Mannheim, K; Schulz, R; Trüstedt, J; Wilms, J; Ojha, R; Ros, E; Anton, G; Baumgartner, W; Beuchert, T; Blanchard, J; Bürkel, C; Carpenter, B; Eberl, T; Edwards, P G; Eisenacher, D; Elsässer, D; Fehn, K; Fritsch, U; Gehrels, N; Gräfe, C; Großberger, C; Hase, H; Horiuchi, S; James, C; Kappes, A; Katz, U; Kreikenbohm, A; Kreykenbohm, I; Langejahn, M; Leiter, K; Litzinger, E; Lovell, J E J; Müller, C; Phillips, C; Plötz, C; Quick, J; Steinbring, T; Stevens, J; Thompson, D J; Tzioumis, A K

    2014-01-01

    The IceCube Collaboration has announced the discovery of a neutrino flux in excess of the atmospheric background. Due to the steeply falling atmospheric background spectrum, events at PeV energies are most likely of extraterrestrial origin. We present the multiwavelength properties of the six radio brightest blazars positionally coincident with these events using contemporaneous data of the TANAMI blazar sample, including high-resolution images and spectral energy distributions. Assuming the X-ray to {\\gamma}-ray emission originates in the photoproduction of pions by accelerated protons, the integrated predicted neutrino luminosity of these sources is large enough to explain the two detected PeV events.

  4. Relation between X-Ray and -Ray Emissions for Fermi Blazars

    Indian Academy of Sciences (India)

    Bijun Li; Xiong Zhang

    2014-09-01

    Using -ray band data detected by Fermi Large Area Telescope (LAT) and X-ray band data for 78 blazars, we find a medium correlation between X-ray and -ray fluxes in the average state. A medium anticorrelation is also found between X-ray (1 KeV) mean spectral index and -ray mean spectral index for blazars. Our results suggest that the most likely radiation mechanism for the high energy -ray would be SSC. And that the -ray emission mechanism may be somewhat different for BL Lacs and FSRQs.

  5. New constraints on the Mid-IR EBL from the HESS discovery of VHE gamma rays from 1ES 0229+200

    CERN Document Server

    Aharonian, F; Bazer-Bachi, A R; Behera, B; Beilicke, M; Benbow, W; Bernlöhr, K; Boisson, C; Bolz, O; Borrel, V; Braun, I; Brion, E; Brown, A M; Buhler, R; Bulik, T; Büsching, I; Boutelier, T; Carrigan, S; Chadwick, P M; Chounet, L M; Clapson, A C; Coignet, G; Cornils, R; Costamante, L; Dalton, M; Degrange, B; Dickinson, H J; Djannati-Atai, A; Domainko, W; O'Connor-Drury, L; Dubois, F; Dubus, G; Dyks, J; Egberts, K; Emmanoulopoulos, D; Espigat, P; Farnier, C; Feinstein, F; Fiasson, A; Förster, A; Fontaine, G; Funk, Seb; Fussling, M; Gallant, Y A; Giebels, B; Glicenstein, J F; Glück, B; Goret, P; Hadjichristidis, C; Hauser, D; Hauser, M; Heinzelmann, G; Henri, G; Hermann, G; Hinton, J A; Hoffmann, A; Hofmann, W; Holleran, M; Hoppe, S; Horns, D; Jacholkowska, A; De Jager, O C; Jung, I; Katarzynski, K; Kendziorra, E; Kerschhaggl, M; Khelifi, B; Keogh, D; Komin, Nu; Kosack, K; Lamanna, G; Latham, I J; Lemiere, A; Lemoine-Goumard, M; Lenain, J P; Lohse, T; Martin, J M; Martineau-Huynh, O; Marcowith, A; Masterson, C; Maurin, D; Maurin, G; McComb, T J L; Moderski, R; Moulin, E; De Naurois, Mathieu; Nedbal, D; Nolan, S J; Ohm, S; Olive, J P; de Ona Wilhelmi, E; Orford, K J; Osborne, J L; Ostrowski, M; Panter, M; Pedaletti, G; Pelletier, G; Petrucci, P O; Pita, S; Pühlhofer, G; Punch, M; Ranchon, S; Raubenheimer, B C; Raue, M; Rayner, S M; Renaud, M; Ripken, J; Rob, L; Rolland, L; Rosier-Lees, S; Rowell, G; Rudak, B; Ruppel, J; Sahakian, V V; Santangelo, A; Schlickeiser, R; Schock, F; Schroder, R; Schwanke, U; Schwarzburg, S; Schwemmer, S; Shalchi, A; Sol, H; Spangler, D; Stawarz, L; Steenkamp, R; Stegmann, C; Superina, G; Tam, P H; Tavernet, J P; Terrier, R; Van Eldik, C; Vasileiadis, G; Venter, C; Vialle, J P; Vincent, P; Vivier, M; Völk, H J; Volpe, F; Wagner, S J; Ward, M; Zdziarski, A A; Zech, A

    2007-01-01

    AIMS: To investigate the very high energy (VHE: >100 GeV) gamma-ray emission from the high-frequency peaked BL Lac 1ES 0229+200. METHODS: Observations of 1ES 0229+200 at energies above 580 GeV were performed with the High Energy Stereoscopic System (HESS) in 2005 and 2006. RESULTS: 1ES 0229+200 is discovered by HESS to be an emitter of VHE photons. A signal is detected at the 6.6 sigma level in the HESS observations (41.8 h live time). The integral flux above 580 GeV is (9.4 +- 1.5 {stat} +- 1.9 {syst}) x 10^{-13} cm^{-2} s^{-1}, corresponding to ~1.8% of the flux observed from the Crab Nebula. The data show no evidence for significant variability on any time scale. The observed spectrum is characterized by a hard power law (Gamma = 2.50 +- 0.19 {stat} +- 0.10 {syst}) from 500 GeV to ~15 TeV. CONCLUSIONS: The high-energy range and hardness of the observed spectrum, coupled with the object's relatively large redshift (z=0.1396), enable the strongest constraints so far on the density of the Extragalactic Backgr...

  6. Joint anisotropy and source count constraints on the contribution of blazars to the diffuse gamma-ray background

    OpenAIRE

    Cuoco, Alessandro; Komatsu, Eiichiro; Siegal-Gaskins, Jennifer

    2012-01-01

    We place new constraints on the contribution of blazars to the large-scale isotropic gamma-ray background (IGRB) by jointly analyzing the measured source count distribution (logN-logS) of blazars and the measured intensity and anisotropy of the IGRB. We find that these measurements point to a consistent scenario in which unresolved blazars make less than 20% of the IGRB intensity at 1-10 GeV while accounting for the majority of the measured anisotropy in that energy band. These results indica...

  7. Optical Spectroscopic Observations of Gamma-ray Blazar Candidates. V. TNG, KPNO, and OAN Observations of Blazar Candidates of Uncertain Type in the Northern Hemisphere

    CERN Document Server

    Crespo, N Álvarez; Ricci, F; Landoni, M; Patiño-Álvarez, V; Massaro, F; D'Abrusco, R; Paggi, A; Chavushyan, V; Jiménez-Bailón, E; Torrealba, J; Latronico, L; La Franca, F; Smith, Howard A; Tosti, G

    2016-01-01

    The extragalactic $\\gamma$-ray sky is dominated by emission from blazars, a peculiar class of active galactic nuclei (AGNs). Many of the $\\gamma$-ray sources included in Fermi -Large Area Telescope Third Source catalog (3FGL) are classified as a blazar candidate of uncertain type (BCU) because there is no optical spectra available in the literature to confirm their nature. In 2013 we started a spectroscopic campaign to look for the optical counterparts of the BCUs and of the Unidentified $\\gamma$-ray Sources. The main goal of our investigation is to confirm the blazar nature of these sources having peculiar properties as compact radio emission and/or selected on the basis of their infrared (IR) colors. Whenever possible we also determine their redshifts. Here we present the results of the observations carried out in the Northern hemisphere in 2013 and 2014 at Telescopio Nazionale Galilleo (TNG), Kitt Peak National Observatory (KPNO) and Observatorio Astron\\'omico Nacional (OAN) in San Pedro M\\'artir. In this ...

  8. Infrared properties of blazars: putting the GASP-WEBT sources into context

    CERN Document Server

    Raiteri, C M; Carnerero, M I; Acosta-Pulido, J A; Larionov, V M; D'Ammando, F; Arévalo, M J; Arkharov, A A; Bueno, A Bueno; Di Paola, A; Efimova, N V; González-Morales, P A; Gorshanov, D L; Grinon-Marin, A B; Lázaro, C; Manilla-Robles, A; Yabar, A Pastor; Giménez, I Puerto; Velasco, S

    2014-01-01

    The infrared properties of blazars can be studied from the statistical point of view with the help of sky surveys, like that provided by the Wide-field Infrared Survey Explorer (WISE) and the Two Micron All Sky Survey (2MASS). However, these sources are known for their strong and unpredictable variability, which can be monitored for a handful of objects only. In this paper we consider the 28 blazars (14 BL Lac objects and 14 flat-spectrum radio quasars, FSRQs) that are regularly monitored by the GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT) since 2007. They show a variety of infrared colours, redshifts, and infrared-optical spectral energy distributions (SEDs), and thus represent an interesting mini-sample of bright blazars that can be investigated in more detail. We present near-IR light curves and colours obtained by the GASP from 2007 to 2013, and discuss the infrared-optical SEDs. These are analysed with the aim of understanding the interplay among different emission compon...

  9. Coeval Observations of a Complete Sample of Blazars with Effelsberg, IRAM 30m, and Planck

    CERN Document Server

    Rachen, Jörg P; Krichbaum, Thomas; Angelakis, Emmanouil; Nestoras, Ioannis; Zensus, Anton; Sievers, Albrecht; Ungerechts, Hans; Keihänen, Elina; Reinecke, Martin

    2016-01-01

    We present the outline and first results of a project using the synergies of the long term blazar radiomillimetre monitoring program F-GAMMA, the continued scanning of the millimetre-submillimetre sky by the Planck satellite, together with several dedicated observing programs at the Effelsberg 100m telescope, to obtain a data sample unprecedented in both time resolution and frequency span.

  10. The physics and cosmology of TeV blazars in a nutshell

    CERN Document Server

    Chang, P

    2013-01-01

    The extragalactic gamma-ray sky at TeV energies is dominated by blazars, a subclass of accreting super-massive black holes with powerful relativistic outflows directed at us. Only constituting a small fraction of the total power output of black holes, blazars were thought to have a minor impact on the universe at best. As we argue here, the opposite is true and the gamma-ray emission from TeV blazars can be thermalized via beam-plasma instabilities on cosmological scales with order unity efficiency, resulting in a potentially dramatic heating of the low-density intergalactic medium. Here, we review this novel heating mechanism and explore the consequences for the formation of structure in the universe. In particular, we show how it produces an inverted temperature-density relation of the intergalactic medium that is in agreement with observations of the Lyman-alpha forest. This suggests that blazar heating can potentially explain the paucity of dwarf galaxies in galactic halos and voids, and the bimodality of...

  11. The Evolution of Swift/BAT blazars and the origin of the MeV background

    CERN Document Server

    Ajello, M; Sambruna, R M; Gehrels, N; Chiang, J; Rau, A; Escala, A; Greiner, J; Tüller, J; Wall, J V; Mushotzky, R F

    2009-01-01

    We use 3 years of data from the Swift/BAT survey to select a complete sample of X-ray blazars above 15 keV. This sample comprises 26 Flat-Spectrum Radio Quasars (FSRQs) and 12 BL Lac objects detected over a redshift range of 0.03blazars. We find that, contrary to the Seyfert-like AGNs detected by BAT, the population of blazars shows strong positive evolution. This evolution is comparable to the evolution of luminous optical QSOs and luminous X-ray selected AGNs. We also find evidence for an epoch-dependence of the evolution as determined previously for radio-quiet AGNs. We interpret both these findings as a strong link between accretion and jet activity. In our sample, the FSRQs evolve strongly, while our best-fit shows that BL Lacs might not evolve at all. The blazar population accounts for 10-20 % (depending on the evolution of the BL Lacs) of the Cosmic X-ray background (CXB) in the 15--55 keV band. W...

  12. The extension of variability properties in gamma-ray bursts to blazars

    CERN Document Server

    Wu, Qingwen; Lei, Wei-Hua; Zou, Yuan-Chuan; Liang, Enwen; Cao, Xinwu

    2015-01-01

    Both gamma-ray bursts (GRBs) and blazars have relativistic jets pointing at a small angle from our line of sight. Several recent studies suggested that these two kinds of sources may share similar jet physics. In this work, we explore the variability properties for GRBs and blazars as a whole. We find that the correlation between minimum variability timescale (MTS) and Lorentz factor, $\\Gamma$, as found only in GRBs by Sonbas et al. can be extended to blazars with a joint correlation of $\\rm MTS\\propto\\Gamma^{-4.7\\pm0.3}$. The same applies to the $\\rm MTS\\propto \\it L_{\\gamma}^{\\rm -1.0\\pm0.1}$ correlation as found in GRBs, which can be well extended into blazars as well. These results provide further evidence that the jets in these two kinds of sources are similar despite of the very different mass scale of their central engines. Further investigations of the physical origin of these correlations are needed, which can shed light on the nature of the jet physics.

  13. RoboPol: First season rotations of optical polarization plane in blazars

    CERN Document Server

    Blinov, D; Papadakis, I; Kiehlmann, S; Panopoulou, G; Liodakis, I; King, O G; Angelakis, E; Baloković, M; Das, H; Feiler, R; Fuhrmann, L; Hovatta, T; Khodade, P; Kus, A; Kylafis, N; Myserlis, I; Modi, D; Pazderska, B; Pazderski, E; Papamastorakis, I; Pearson, T J; Rajarshi, C; Ramaprakash, A; Reig, P; Readhead, A C S; Tassis, K; Zensus, J A

    2015-01-01

    We present first results on polarization swings in optical emission of blazars obtained by RoboPol, a monitoring program of an unbiased sample of gamma-ray bright blazars specially designed for effective detection of such events. A possible connection of polarization swing events with periods of high activity in gamma rays is investigated using the dataset obtained during the first season of operation. It was found that the brightest gamma-ray flares tend to be located closer in time to rotation events, which may be an indication of two separate mechanisms responsible for the rotations. Blazars with detected rotations have significantly larger amplitude and faster variations of polarization angle in optical than blazars without rotations. Our simulations show that the full set of observed rotations is not a likely outcome (probability $\\le 1.5 \\times 10^{-2}$) of a random walk of the polarization vector simulated by a multicell model. Furthermore, it is highly unlikely ($\\sim 5 \\times 10^{-5}$) that none of o...

  14. Constraints on black hole massess with timescales of variations in blazars

    CERN Document Server

    Liu, H T

    2015-01-01

    In this paper, we investigated the issue of black hole masses and minimum timescales of jet emission for blazars. We proposed a sophisticated model that sets an upper limit to the central black hole masses $M_{\\bullet}$ with the minimum timescales $\\Delta t^{\\rm{ob}}_{\\rm{min}}$ of variations observed in blazars. The value of $\\Delta t^{\\rm{ob}}_{\\rm{min}}$ presents an upper limit to the size of blob in jet. The blob is assumed to be generated in the jet-production region in the vicinity of black hole, and then the expanding blob travels outward along the jet. We applied the model to 32 blazars, 29 of which were detected in gamma rays by satellites, and these $\\Delta t^{\\rm{ob}}_{\\rm{min}}$ are on the order of hours with large variability amplitudes. In general, these $M_{\\bullet}$ estimated with this method are not inconsistent with those masses reported in the literatures. This model is natural to connect $M_{\\bullet}$ with $\\Delta t^{\\rm{ob}}_{\\rm{min}}$ for blazars, and seems to be applicable to constrain...

  15. Multiwavelength Doppler factors for Fermi-detected gamma-ray loud blazars

    Institute of Scientific and Technical Information of China (English)

    Hou-Dun Zeng; Li Zhang

    2011-01-01

    We collect a sample of 51 Fermi-detected gamma-ray loud blazars with known radio Doppler factors and study properties of the Doppler factors of blazars at optical, X-ray and gamma-ray bands. A basic assumption is that the emission from the radio to gamma-ray bands of the blazars are produced by the nonthermal radiation of accelerated particles in a jet. Our results show that (1) the Doppler factors of blazars are a function of frequency, with the Doppler factor decreasing with frequency from the radio to X-ray regions, and then increasing from the X-ray to y-ray regions which are similar to results given by Zhang et al., and (2) there are marginal correlations between the Doppler factors at radio and X-ray bands and the synchrotron peak frequency, and a strong correlation between the Doppler factor in the gamma-ray band and the synchrotron peak frequency, but no correlation in the optical band.

  16. Frequency dependent core shifts and parameter estimation for the blazar 3C 454.3

    CERN Document Server

    Mohan, P; Mangalam, A; Gupta, Alok C; Wiita, Paul J; Volvach, A E; Aller, M F; Aller, H D; Gu, M F; Lahteenmaki, A; Tornikoski, M; Volvach, L N

    2015-01-01

    We study the core shift effect in the parsec scale jet of the blazar 3C 454.3 using the 4.8 GHz - 36.8 GHz radio light curves obtained from three decades of continuous monitoring. From a piecewise Gaussian fit to each flare, time lags $\\Delta t$ between the observation frequencies $\

  17. The Influence of Plasma Effects of Pair Beams on the Intergalactic Cascade Emission of Blazars

    Science.gov (United States)

    Menzler, Ulf; Schlickeiser, Reinhard

    2014-03-01

    The attenuation of TeV γ-rays from distant blazars by the extragalactic background light (EBL) produces relativistic electron-positron pair beams. It has been shown by Broderick et. al. (2012) and Schlickeiser et. al (2012) that a pair beam traversing the intergalactic medium is unstable to linear two-stream instabilities of both electrostatic and electromagnetic nature. While for strong blazars all free pair energy is dissipated in heating the intergalactic medium and a potential electromagnetic cascade via inverse-Compton scattering with the cosmic microwave background is suppressed, we investigate the case of weak blazars where the back reaction of generated electrostatic turbulence leads to a plateauing of the electron energy spectrum. In the ultra-relativistic Thomson limit we analytically calculate the inverse-Compton spectral energy distribution for both an unplateaued and a plateaued beam scenario, showing a peak reduction factor of Rpeak ≈ 0.345. This is consistent with the FERMI non-measurements of a GeV excess in the spectrum of EBL attenuated TeV blazars. Claims on the lower bound of the intergalactic magnetic field strengths, made by several authors neglecting plasma effects, are thus put into question.

  18. Simultaneous Planck, Swift, and Fermi Observations of X-ray and Gamma-ray Selected Blazars

    Science.gov (United States)

    Giommi, P.; Polenta, G.; Laehteenmaeki, A.; Thompson, D. J.; Capalbi, M.; Cutini, S.; Gasparrini, D.; Gonzalez, Nuevo, J.; Leon-Tavares, J.; Lopez-Caniego, M.; Mazziotta, M. N.; Monte, C.; Perri, M.; Raino, S.; Tosti, G.; Tramacere, A.; Verracchia, F.; Aller, H. D.; Aller, MF.; Angelakis, E.; Bastieri, D.; Berdyugin, A.; Bonaldi, A.; Bonavera, L.; Lawrence, C. R.

    2012-01-01

    We present simultaneous Planck, Swift, Fermi, and ground-based data for 105 blazars belonging to three samples with flux limits in the soft X-ray, hard X-ray, and gamma-ray bands, with additional 5 GHz flux-density limits to ensure a good probability of a Planck detection. We compare our results to those of a companion paper presenting simultaneous Planck and multi-frequency observations of 104 radio-loud northern active galactic nuclei selected at radio frequencies. While we confirm several previous results, our unique data set allows us to demonstrate that the selection method strongly influences the results, producing biases that cannot be ignored. Almost all the BL Lac objects have been detected by the Fermi Large Area Telescope (LAT), whereas 30% to 40% of the flat-spectrum radio quasars (FSRQs) in the radio, soft X-ray, and hard X-ray selected samples are still below the gamma-ray detection limit even after integrating 27 months of Fermi-LAT data. The radio to sub-millimetre spectral slope of blazars is quite flat, with (alpha) approx 0 up to about 70GHz, above which it steepens to (alpha) approx -0.65. The BL Lacs have significantly flatter spectra than FSRQs at higher frequencies. The distribution of the rest-frame synchrotron peak frequency (nu(sup s)(sub peak)) in the spectral energy distribution (SED) of FSRQs is the same in all the blazar samples with (nu(sup s)(sub peak)) = 10(exp 13.1 +/- 0.1) Hz, while the mean inverse Compton peak frequency, (nu(sup IC)(sub peak)), ranges from 10(exp 21) to 10(exp 22) Hz. The distributions of nu(sup s)(sub peak) and nu(sup IC)(sub peak) of BL Lacs are much broader and are shifted to higher energies than those of FSRQs; their shapes strongly depend on the selection method. The Compton dominance of blazars. defined as the ratio of the inverse Compton to synchrotron peak luminosities, ranges from less than 0.2 to nearly 100, with only FSRQs reaching values larger than about 3. Its distribution is broad and depends

  19. Coincidence of a high-fluence blazar outburst with a PeV-energy neutrino event

    Science.gov (United States)

    Kadler, M.; Krauß, F.; Mannheim, K.; Ojha, R.; Müller, C.; Schulz, R.; Anton, G.; Baumgartner, W.; Beuchert, T.; Buson, S.; Carpenter, B.; Eberl, T.; Edwards, P. G.; Eisenacher Glawion, D.; Elsässer, D.; Gehrels, N.; Gräfe, C.; Gulyaev, S.; Hase, H.; Horiuchi, S.; James, C. W.; Kappes, A.; Kappes, A.; Katz, U.; Kreikenbohm, A.; Kreter, M.; Kreykenbohm, I.; Langejahn, M.; Leiter, K.; Litzinger, E.; Longo, F.; Lovell, J. E. J.; McEnery, J.; Natusch, T.; Phillips, C.; Plötz, C.; Quick, J.; Ros, E.; Stecker, F. W.; Steinbring, T.; Stevens, J.; Thompson, D. J.; Trüstedt, J.; Tzioumis, A. K.; Weston, S.; Wilms, J.; Zensus, J. A.

    2016-08-01

    The astrophysical sources of the extraterrestrial, very high-energy neutrinos detected by the IceCube collaboration remain to be identified. Gamma-ray (γ-ray) blazars have been predicted to yield a cumulative neutrino signal exceeding the atmospheric background above energies of 100 TeV, assuming that both the neutrinos and the γ-ray photons are produced by accelerated protons in relativistic jets. As the background spectrum falls steeply with increasing energy, the individual events with the clearest signature of being of extraterrestrial origin are those at petaelectronvolt energies. Inside the large positional-uncertainty fields of the first two petaelectronvolt neutrinos detected by IceCube, the integrated emission of the blazar population has a sufficiently high electromagnetic flux to explain the detected IceCube events, but fluences of individual objects are too low to make an unambiguous source association. Here, we report that a major outburst of the blazar PKS B1424-418 occurred in temporal and positional coincidence with a third petaelectronvolt-energy neutrino event (HESE-35) detected by IceCube. On the basis of an analysis of the full sample of γ-ray blazars in the HESE-35 field, we show that the long-term average γ-ray emission of blazars as a class is in agreement with both the measured all-sky flux of petaelectronvolt neutrinos and the spectral slope of the IceCube signal. The outburst of PKS B1424-418 provides an energy output high enough to explain the observed petaelectronvolt event, suggestive of a direct physical association.

  20. Theoretical Study Of The Effects Of Magnetic Field Geometry On The High-Energy Emission Of Blazars

    CERN Document Server

    Joshi, Manasvita; Boettcher, Markus

    2016-01-01

    The knowledge of the structure of the magnetic field inside a blazar jet, as deduced from polarization observations at radio to optical wavelengths, is closely related to the formation and propagation of relativistic jets that result from accretion onto supermassive black holes. However, a largely unexplored aspect of the theoretical understanding of radiation transfer physics in blazar jets has been the magnetic field geometry as revealed by the polarized emission and the connection between the variability in polarization and flux across the spectrum. Here, we explore the effects of various magnetic geometries that can exist inside a blazar jet: parallel, oblique, toroidal, and tangled. We investigate the effects of changing the orientation of the magnetic field, according to the above-mentioned geometries, on the resulting high-energy spectral energy distributions (SEDs) and spectral variability patterns (SVPs) of a typical blazar. We use the MUlti-ZOne Radiation Feedback (MUZORF) model of Joshi et al. (201...

  1. Fermi LAT detection of increasing GeV gamma-ray activity from the high-energy peaked BL Lac object 1ES 1959+650

    Science.gov (United States)

    Ciprini, Stefano; Fermi Large Area Telescope Collaboration

    2015-10-01

    The Large Area Telescope (LAT), one of two instruments on the Fermi Gamma-ray Space Telescope, has observed increasing gamma-ray emission from a source positionally consistent with the very-high energy peaked BL Lac object 1ES 1959+650 (also known as TXS 1959+650 and 3FGL J2000.0+6509, Acero et al. 2015, ApJS 218, 23) with radio coordinates (J2000) R.A.: 299.999384 deg, Dec.: 65.148514 deg (Beasley et al. 2002, ApJS, 141, 13). This source has a redshift z=0.047 (Schachter et al. 1993, ApJ, 412, 541).

  2. Fermi-LAT, FACT, MAGIC and VERITAS detection of increasing gamma-ray activity from the high-energy peaked BL Lac object 1ES 1959+650

    Science.gov (United States)

    Buson, S.; Magill, J. D.; Dorner, D.; Biland, A.; Mirzoyan, R.; Mukherjee, R.

    2016-04-01

    The Fermi-LAT, FACT, MAGIC and VERITAS collaborations report the detection of enhanced gamma-ray activity from a source positionally consistent with the very-high-energy peaked BL Lac object 1ES 1959+650 (a.k.a 3FGL J2000.0+6509, in the 3rd LAT source catalog, 3FGL, Acero et al. 2015, ApJS 218, 23) with radio coordinates (J2000) R.A.: 299.999384 deg, Dec.: 65.148514 deg (Beasley et al. 2002, ApJS, 141, 13). This source has a redshift z=0.047 (Schachter et al. 1993, ApJ, 412, 541).

  3. The central black hole masses for the γ-ray loud blazars

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (formerly GLAST) provides an increase in sensitivity and has detected rapid variability of gamma-ray sources.The variability time scales detected from the gamma-ray loud blazars by LAT and EGRET,and gamma-ray luminosity are used to estimate the central black hole masses.In this work,we find that the lower limits of central black hole masses are in a range of (0.3-24)×107M⊙,which are compared with those obtained by other authors.Our results are consistent with other authors’ results.Also,the Lorentz factor,Γ,and the propagation angle,θ,are obtained for 18 blazars for which superluminal motions are known.

  4. A Diagnostic Test for Determining the Location of the GeV Emission in Powerful Blazars

    Science.gov (United States)

    Dotson, Amanda; Georganopoulos, Markos; Kazanas, Demosthenes; Perlman, Eric

    2011-01-01

    An issue currently under debate in the literature is how far from the black hole is the Fermi-observed GeV emission of powerful blazars emitted. Here we present a clear diagnostic tool for testing whether the Ge V emission site is located within the sub-pc broad emission line (BLR) region or further out in the few pc scale molecular torus (MT) environment. Within the BLR the scatteri takes place at the onset of the Klein-Nishina regime, causing the electron cooling time to become almost energy independent and as a result, the variation of high-energy emission is expected to be achromatic. Contrarily, if the emission site is located outside the BLR, the expected GeY variability is energy-dependent and with amplitude increasing with energy. We demonstrate this using time-dependent numerical simulations of blazar variability.

  5. The relationship of extended radio power and broad emission line luminosity in blazars

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The relationship between broad line luminosity LBLR and extended radio power PE is investigated.In the log PE-log LBLR diagram,FSRQs populate the region of higher luminosity relative to BL Lacs,and FR II BL Lacs are between FSRQs and FR I BL Lacs.For these blazars,there is a significant correlation between LBLR and PE.The regression line scales as PE ∝ L0B.L87R ± 0.15.The slope of this scaling relation is consistent with that derived from the simple theoretical formulae.Thus,the unification of BL Lacs and FRSQs into a single population finds a statistical basis,and a disk-jet symbiosis in blazars is confirmed.FR II BL Lacs are probably at an intermediate stage in the sequence from FSRQs to BL Lacs with FR I BL Lacs at the end of this sequence.

  6. Multi-TeV flaring from blazars: Markarian 421 a case study

    CERN Document Server

    Sahu, Sarira; Rajpoot, Subhash

    2015-01-01

    The TeV blazar Markarian 421 underwent multi-TeV flaring during April 2004 and simultaneously observed in x-ray and TeV energies. It was observed that the TeV outbursts had no counterparts in the lower energies, which implies that this might be an orphan flare. In the context of hadronic model, we have shown that this multi-TeV flaring can be produced due to the interaction of Fermi-accelerated protons of energy $\\lesssim 168$ TeV with the background photons in the low energy tail of the synchrotron self-Compton spectrum of the blazar jet. We fit very well the flaring spectrum with this model. Based on this study, we speculate that Mrk 501 and PG 1553+113 are possible candidates for orphan flaring in the future.

  7. Looking for blazars in a sample of unidentified high-energy emitting Fermi sources

    CERN Document Server

    Marchesini, E J; Chavushyan, V; Cellone, S A; Andruchow, I; Bassani, L; Bazzano, A; Jiménez-Bailón, E; Landi, R; Malizia, A; Palazzi, E; Patiño-Álvarez, V; Rodríguez-Castillo, G A; Stephen, J B; Ubertini, P

    2016-01-01

    Context. Based on their overwhelming dominance among associated Fermi gamma ray catalogue sources, it is expected that a large fraction of the unidentified Fermi objects are blazars. Through crossmatching between the positions of unidentified gamma ray sources from the First Fermi Catalog of gamma ray sources emitting above 10 GeV (1FHL) and the ROSAT and Swift XRT catalogues of X ray objects and between pointed XRT observations, a sample of 36 potential associations was found in previous works with less than 15 arcsec of positional offset. One third of them have recently been classified; the remainder, though believed to belong to the blazar class, still lack spectroscopic classifications. Aims. We study the optical spectrum of the putative counterparts of these unidentified gamma ray sources in order to find their redshifts and to determine their nature and main spectral characteristics. Methods. An observational campaign was carried out on the putative counterparts of 13 1FHL sources using medium resolutio...

  8. The estimations of four basic parameters for gamma-ray loud blazars

    Institute of Scientific and Technical Information of China (English)

    Jun-Hui Fan; Yu-Hai Yuan; Yi Liu; Jing-Yi Zhang; Yi-Ping Qin; Hua Liu; Yong Huang; Jiang-He Yang; Hong-Guang Wang; Jiang-Shui Zhang

    2009-01-01

    The method used in our previous papers is adopted to estimate four basic pa-rameters (the central black hole mass (M), the boosting factor (or Doppler factor) (δ), the (d)) for 59 γ-ray loud blazars (20 BL Lacertae objects and 39 fiat spectrum radio quasars).The central black hole masses estimated for this sample are in a range of from 107 M⊙to 109 M⊙. In the case of black hole mass, there is no clear difference between BL Lacertae objects and flat spectrum radio quasars, which is consistent with the previous results sug-gesting that the central black hole masses do not play an important role in the evolutionary sequence of blazars.

  9. RoboPol: optical polarization-plane rotations and flaring activity in blazars

    CERN Document Server

    Blinov, D; Papadakis, I E; Hovatta, T; Pearson, T J; Liodakis, I; Panopoulou, G V; Angelakis, E; Baloković, M; Das, H; Khodade, P; Kiehlmann, S; King, O G; Kus, A; Kylafis, N; Mahabal, A; Marecki, A; Modi, D; Myserlis, I; Paleologou, E; Papamastorakis, I; Pazderska, B; Pazderski, E; Rajarshi, C; Ramaprakash, A; Readhead, A C S; Reig, P; Tassis, K; Zensus, J A

    2016-01-01

    We present measurements of rotations of the optical polarization of blazars during the second year of operation of RoboPol, a monitoring programme of an unbiased sample of gamma-ray bright blazars specially designed for effective detection of such events, and we analyse the large set of rotation events discovered in two years of observation. We investigate patterns of variability in the polarization parameters and total flux density during the rotation events and compare them to the behaviour in a non-rotating state. We have searched for possible correlations between average parameters of the polarization-plane rotations and average parameters of polarization, with the following results: (1) there is no statistical association of the rotations with contemporaneous optical flares; (2) the average fractional polarization during the rotations tends to be lower than that in a non-rotating state; (3) the average fractional polarization during rotations is correlated with the rotation rate of the polarization plane...

  10. GAMMA-RAY AND X-RAY EMISSION FROM GAMMA-RAY-LOUD BLAZARS

    Institute of Scientific and Technical Information of China (English)

    ZHANG XIONG; ZHAO GANG; XIE GUANG-ZHONG; ZHENG GUANG-SHENG; ZHANG LI

    2001-01-01

    We present a strong correlation of the gamma-ray (above 100 MeV) mean spectral indices aγ and X-ray (1 keV)mean spectral indices cX for 34 gamma-ray-loud blazars (16 BL Lac objects and 18 flat spectrum radio quasars). Astrong correlation is also found between the gamma-ray flux densities F-γ and X-ray flux densities Fx in the low state for 47 blazars (17 BL Lac and 30 flat spectrum radio quasars). Possible correlation on the gamma-ray emission mechanism is discussed. We suggest that the main gamma-ray radiation mechanism is probably the synchrotron process. The gamma-ray emission may be somewhat different from that of BL Lac objects and flat spectrum radio quasars.

  11. Electromagnetic cascade masquerade: a way to mimic $\\gamma$--ALP mixing effects in blazar spectra

    CERN Document Server

    Dzhatdoev, T A; Kircheva, A P; Lyukshin, A A

    2016-01-01

    Most of the studies on extragalactic {\\gamma}-ray propagation performed up to now only accounted for primary gamma-ray absorption and adiabatic losses (absorption-only model). However, there is growing evidence that this model is oversimplified and must be modified in some way. (...) There are many hints that a secondary component from electromagnetic cascades initiated by primary $\\gamma$-rays or nuclei may be observed in the spectra of some blazars. We study the impact of electromagnetic cascades from primary $\\gamma$-rays or protons on the physical interpretation of blazar spectra obtained with imaging Cherenkov telescopes. We use the publicly-available code ELMAG to compute observable spectra of electromagnetic cascades from primary $\\gamma$-rays. For the case of primary proton, we develop a simple, fast, and reasonably accurate hybrid method to calculate the observable spectrum. (...) Electromagnetic cascades show at least two very distinct regimes labeled by the energy of the primary $\\gamma$-ray ($E_{0...

  12. The Evolution of Swift/BAT blazars and the origin of the MeV background

    Energy Technology Data Exchange (ETDEWEB)

    Ajello, M.; /SLAC /KIPAC, Menlo Park; Costamante, L.; /Stanford U., HEPL /KIPAC, Menlo Park; Sambruna, R.M.; Gehrels, N.; /NASA, Goddard; Chiang, J.; /SLAC /KIPAC, Menlo Park; Rau, A.; /Caltech; Escala, A.; /SLAC /KIPAC, Menlo Park /Cerro Calan Observ.; Greiner, J.; /Garching, Max Planck Inst., MPE; Tueller, J.; /NASA, Goddard; Wall, J.V.; /British Columbia U.; Mushotzky, R.F.; /NASA, Goddard

    2009-10-17

    We use 3 years of data from the Swift/BAT survey to select a complete sample of X-ray blazars above 15 keV. This sample comprises 26 Flat-Spectrum Radio Quasars (FSRQs) and 12 BL Lac objects detected over a redshift range of 0.03 < z < 4.0. We use this sample to determine, for the first time in the 15-55 keV band, the evolution of blazars. We find that, contrary to the Seyfert-like AGNs detected by BAT, the population of blazars shows strong positive evolution. This evolution is comparable to the evolution of luminous optical QSOs and luminous X-ray selected AGNs. We also find evidence for an epoch-dependence of the evolution as determined previously for radio-quiet AGNs. We interpret both these findings as a strong link between accretion and jet activity. In our sample, the FSRQs evolve strongly, while our best-fit shows that BL Lacs might not evolve at all. The blazar population accounts for 10-20% (depending on the evolution of the BL Lacs) of the Cosmic X-ray background (CXB) in the 15-55 keV band. We find that FSRQs can explain the entire CXB emission for energies above 500 keV solving the mystery of the generation of the MeV background. The evolution of luminous FSRQs shows a peak in redshift (z{sub c} = 4.3 {+-} 0.5) which is larger than the one observed in QSOs and X-ray selected AGNs. We argue that FSRQs can be used as tracers of massive elliptical galaxies in the early Universe.

  13. On conservative models of "the pair-production anomaly" in blazar spectra at Very High Energies

    OpenAIRE

    Dzhatdoev, T. A.

    2015-01-01

    For some blazars, the gamma-ray absorption features due to pair-production on the Extragalactic Background Light (EBL) are fainter than expected. The present work reviews the main models that could explain this paradox, with emphasis on conservative ones, that do not include any new physics. The models that are intrinsic to the source, do allow a very hard primary spectrum, but fail to explain a regular redshift dependence of the anomaly starting energy. The model that includes a contribution...

  14. Broad Band Spectral Index TeV Blazars Detected by Fermi LAT

    Indian Academy of Sciences (India)

    Yong Juan Cha; Xiong Zhang

    2014-09-01

    We collected the radio, K-band, optical, X-ray, and -ray data for 35 TeV blazars detected by Fermi LAT and studied the possible correlation between different broad band spectral indices (r.o, r.x, ir.o, ir.x, o., x.) in all states (average/high/low). Based on our results, we suggested that the seed photons of the -ray drive from the synchrotron radiation themselves.

  15. Searching for distant blazars with GLAST and the Large Millimeter Telescope

    Directory of Open Access Journals (Sweden)

    Alberto Carramiñana

    2008-01-01

    Full Text Available El Gran Telescopio Milimétrico estudiará el universo a altos corrimientos al rojo, incluyendo la formación de las primeras galaxias masivas y sus núcleos activos. El GTM puede ser usado en conjunto con GLAST en la búsqueda de los blazares más distantes para explorar la época de formación de los primeros hoyos negros.

  16. VizieR Online Data Catalog: Sample of Fermi Blazars (Chen+, 2016)

    Science.gov (United States)

    Chen, Y.-Y.; Zhang, X.; Xiong, D.-R.; Wang, S.-J.; Yu, X.-L.

    2016-04-01

    We tried to select a large number of blazars with reliable redshift, radio core and extended radio luminosity at 1.4GHz. Firstly, we considered the following samples of blazars to get the radio core luminosity and extended luminosity at 1.4GHz: Kharb et al. (2010, J/ApJ/710/764), Antonucci & Ulvestad (1985ApJ...294..158A), Cassaro et al. (1999A&AS..139..601C), Murphy et al. (1993MNRAS.264..298M), Landt & Bignall (2008MNRAS.391..967L), Caccianiga & Marcha (2004, Cat. J/MNRAS/348/973), Giroletti et al. (2004). We cross-correlated these samples with the Fermi LAT Third Source Catalog (3FGL), and we acquired the 3FGL spectral index and energy flux at 0.1-100GeV from clean sources in 3FGL (Fermi-LAT Collaboration 2015, J/ApJS/218/23) Using these catalogs, we compiled 201 Fermi blazars. (1 data file).

  17. Multiwavelength behaviour of the blazar OJ 248 from radio to {\\gamma}-rays

    CERN Document Server

    Carnerero, M I; Villata, M; Acosta-Pulido, J A; D'Ammando, F; Smith, P S; Larionov, V M

    2015-01-01

    We present an analysis of the multiwavelength behaviour of the blazar OJ 248 at z = 0.939 in the period 2006-2013. We use low-energy data (optical, near-infrared, and radio) obtained by 21 observatories participating in the GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT), as well as data from the Swift (optical-UV and X-rays) and Fermi (gamma-rays) satellites, to study flux and spectral variability and correlations among emissions in different bands. We take into account the effect of absorption by the Damped Lyman Alpha intervening system at z = 0.525. Two major outbursts were observed in 2006-2007 and in 2012-2013 at optical and near-IR wavelengths, while in the high-frequency radio light curves prominent radio outbursts are visible peaking at the end of 2010 and beginning of 2013, revealing a complex radio-optical correlation. Cross-correlation analysis suggests a delay of the optical variations after the gamma-ray ones of about a month, which is a peculiar behaviour in blazar...

  18. SMARTS optical and infrared monitoring of 12 gamma-ray bright blazars

    CERN Document Server

    Bonning, E W; Bailyn, C; Buxton, M; Chatterjee, R; Coppi, P; Fossati, G; Isler, J; Maraschi, L

    2012-01-01

    We present multiwavelength data for twelve blazars observed from 2008-2010 as part of an ongoing optical-infrared photometric monitoring project. Sources were selected to be bright, southern (dec < 20 deg) blazars observed by the Fermi Gamma-Ray Space Telescope, with daily and weekly gamma-ray fluxes made available from the start of the Fermi mission. Light curves are presented for the twelve blazars in BVRJK at near-daily cadence. We find that optical and infrared fluxes are well correlated in all sources. Gamma-ray bright flat spectrum radio quasars (FSRQs) in our sample have optical/infrared emission correlated with gamma-rays consistent with inverse Compton-scattering models for GeV emission. In FSRQs, the variability amplitude decreases towards optical/IR wavelengths, consistent with the presence of a thermal emission component from the accretion disk varying on significantly longer timescales than the jet synchrotron emission. In BL Lac objects, variability is mainly constant across wavelengths, cons...

  19. HIGHLY VARIABLE OBJECTS IN THE PALOMAR-QUEST SURVEY: A BLAZAR SEARCH USING OPTICAL VARIABILITY

    International Nuclear Information System (INIS)

    We identify 3113 highly variable objects in 7200 deg2 of the Palomar-QUEST (PQ) Survey, which each varied by more than 0.4 mag simultaneously in two broadband optical filters on timescales from hours to roughly 3.5 years. The primary goal of the selection is to find blazars by their well-known violent optical variability. Because most known blazars have been found in radio and/or X-ray wavelengths, a sample discovered through optical variability may have very different selection effects, elucidating the range of behavior possible in these systems. A set of blazars selected in this unusual manner will improve our understanding of the physics behind this extremely variable and diverse class of active galactic nucleus (AGN). The object positions, variability statistics, and color information are available using the PQ CasJobs server. The time domain is just beginning to be explored over large sky areas; we do not know exactly what a violently variable sample will hold. About 20% of the sample has been classified in the literature; over 70% of those objects are known or likely AGNs. The remainder largely consists of a variety of variable stars, including a number of RR Lyrae and cataclysmic variables.

  20. Spectral analysis of Fermi-LAT blazars above 50 GeV

    CERN Document Server

    Domínguez, Alberto

    2015-01-01

    We present an analysis of the intrinsic (unattenuated by the extragalactic background light, EBL) power-law spectral indices of 128 extragalactic sources detected up to z~2 with the Fermi-Large Area Telescope (LAT) at very high energies (VHEs, E>50 GeV). The median of the intrinsic index distribution is 2.20 (versus 2.54 for the observed distribution). We also analyze the observed spectral breaks (i.e., the difference between the VHE and high energy, HE, 100 MeVblazar curvature and EBL attenuation. There is also no evidence of evolution with redshift of the physics that drives the photon emission in high-frequency synchrotron peak (HSP) blazars. This makes HSP blazars excellent probes of the EBL.

  1. Upper Limits on the Extragalactic Background Light from the Gamma-Ray Spectra of Blazars

    CERN Document Server

    Schroedter, M

    2005-01-01

    The direct measurement of the extragalactic background light (EBL) is difficult at optical to infrared wavelengths because of the strong foreground radiation originating in the Solar System. Very high energy (VHE, E$>$100 GeV) gamma rays interact with EBL photons of these wavelengths through pair production. In this work, the available VHE spectra from six blazars are used to place upper limits on the EBL. These blazars have been detected over a range of redshifts and a steepening of the spectral index is observed with increasing source distance. This can be interpreted as absorption by the EBL. In general, knowledge of the intrinsic source spectrum is necessary to determine the density of the intervening EBL. Motivated by the observed spectral steepening with redshift, upper limits on the EBL are derived by assuming that the intrinsic spectra of the six blazars are $\\propto E^{-1.8}$. Upper limits are then placed on the EBL flux at discrete energies without assuming a specific spectral shape for the EBL. Thi...

  2. Multi-band optical variability of three TeV Blazars on Diverse Timescales

    CERN Document Server

    Gupta, Alok C; Bhagwan, J; Strigachev, A; Bachev, R; Semkov, E; Gaur, H; Damljanovic, G; Vince, O; Wiita, Paul J

    2016-01-01

    We present our optical photometric observations of three TeV blazars, PKS 1510-089, PG 1553+113 and Mrk 501 taken using two telescopes in India, one in Bulgaria, one in Greece and one in Serbia during 2012 - 2014. These observations covered a total of 95 nights with a total of 202 B filter frames, 247 images in V band, 817 in R band while 229 images were taken in the I filter. This work is focused on multi-band flux and colour variability studies of these blazars on diverse timescales which are useful in understanding the emission mechanisms. We studied the variability characteristics of above three blazars and found all to be active over our entire observational campaigns. We also searched for any correlation between the brightness of the sources and their colour indices. During the times of variability, no significant evidence for the sources to display spectral changes correlated with magnitude was found on timescales of a few months. We briefly discuss the possible physical mechanisms most likely responsi...

  3. Coincidence of a high-fluence blazar outburst with a PeV-energy neutrino event

    CERN Document Server

    Kadler, M; Mannheim, K; Ojha, R; Müller, C; Schulz, R; Anton, G; Baumgartner, W; Beuchert, T; Buson, S; Carpenter, B; Eberl, T; Edwards, P G; Glawion, D Eisenacher; Elsässer, D; Gehrels, N; Gräfe, C; Hase, H; Horiuchi, S; James, C W; Kappes, A; Katz, U; Kreikenbohm, A; Kreter, M; Kreykenbohm, I; Langejahn, M; Leiter, K; Litzinger, E; Longo, F; Lovell, J E J; McEnery, J; Phillips, C; Plötz, C; Quick, J; Ros, E; Stecker, F W; Steinbring, T; Stevens, J; Thompson, D J; Trüstedt, J; Tzioumis, A K; Wilms, J; Zensus, J A

    2016-01-01

    The discovery of extraterrestrial very-high-energy neutrinos by the IceCube collaboration has launched a quest for the identification of their astrophysical sources. Gamma-ray blazars have been predicted to yield a cumulative neutrino signal exceeding the atmospheric background above energies of 100 TeV, assuming that both the neutrinos and the gamma-ray photons are produced by accelerated protons in relativistic jets. Since the background spectrum falls steeply with increasing energy, the individual events with the clearest signature of being of an extraterrestrial origin are those at PeV energies. Inside the large positional-uncertainty fields of the first two PeV neutrinos detected by IceCube, the integrated emission of the blazar population has a sufficiently high electromagnetic flux to explain the detected IceCube events, but fluences of individual objects are too low to make an unambiguous source association. Here, we report that a major outburst of the blazar PKS B1424-418 occurred in temporal and pos...

  4. Prominent Polarized Flares of the Blazars AO 0235+164 and PKS 1510-089

    CERN Document Server

    Sasada, Mahito; Fukazawa, Yasushi; Kawabata, Koji S; Ikejiri, Yuki; Itoh, Ryosuke; Yamanaka, Masayuki; Sakimoto, Kiyoshi; Ohsugi, Takashi; Yoshida, Michitoshi; Sato, Shuji; Kino, Masaru

    2011-01-01

    We report on multi-band photometric and polarimetric observations of the blazars AO 0235+164 and PKS 1510-089. These two blazars were active in 2008 and 2009, respectively. In these active states, prominent short flares were observed in both objects, having amplitudes of >1 mag within 10 d. The $V-J$ color became bluer when the objects were brighter in these flares. On the other hand, the color of PKS 1510-089 exhibited a trend that it became redder when it was brighter, except for its prominent flare. This redder-when-brighter trend can be explained by the strong contribution of thermal emission from an accretion disk. The polarization degree increased at the flares, and reached >25 % at the maxima. We compare these flares in AO 0235+164 and PKS 1510-089 with other short flares which were detected by our monitoring of 41 blazars. Those two flares had one of the largest variation amplitudes in both flux and polarization degree. Furthermore, we found a significant positive correlation between the amplitudes of...

  5. Multi-frequency, multi-messenger astrophysics with Swift. The case of blazars

    CERN Document Server

    Giommi, Paolo

    2015-01-01

    During its first 10 years of orbital operations Swift dedicated approximately 11% of its observing time to blazars, carrying out more than 12,000 observations of ~1,600 different objects, for a total exposure time of over 25 million seconds. This is probably the largest contribution to multi-frequency (optical, UV, soft and hard X-rays) and multi-temporal data archives about this type of sources. In this paper I briefly discuss the impact that Swift is having on blazar multi-frequency and time-domain astrophysics, as well as how it is contributing to the opening of the era of multi-messenger astronomy. Finally, I present some preliminary results from a systematic analysis of a very large number of Swift XRT observations of blazars. All the "science ready" data products that are being generated by this project will be publicly released. Specifically, deconvolved X-ray spectra and best fit spectral parameters will be available through the ASDC "SED builder" tool (https://tools.asdc.asi.it/SED) and by means of i...

  6. The Energy Spectrum of the Blazar Markarian 421 Above 130 GeV

    CERN Document Server

    Carson, J E; Ong, R A; Ball, J; Bramel, D A; Covault, C E; Driscoll, D; Fortin, P; Gingrich, D M; Hanna, D S; Lindner, T; Müller, C; Jarvis, A; Mukherjee, R; Ragan, K; Scalzo, R A; Williams, D A; Zweerink, J

    2006-01-01

    Markarian 421 (Mrk 421) was the first blazar detected at gamma-ray energies above 300 GeV, and it remains one of only twelve TeV blazars detected to date. TeV gamma-ray measurements of its flaring activity and spectral variability have placed constraints on models of the high-energy emission from blazars. However, observations between 50 and 300 GeV are rare, and the high-energy peak of the spectral energy distribution (SED), predicted to be in this range, has never been directly detected. We present a detection of Mrk 421 above 100 GeV as made by the Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) during a multiwavelength campaign in early 2004. STACEE is a ground-based atmospheric Cherenkov telescope using the wavefront sampling technique to detect gamma rays at lower energies than achieved by most imaging Cherenkov telescopes. We also outline a method for reconstructing gamma-ray energies using a solar heliostat telescope. This technique was applied to the 2004 data, and we present the differe...

  7. Upper limits from five years of blazar observations with the VERITAS Cherenkov telescopes

    CERN Document Server

    Archambault, S; Benbow, W; Bird, R; Biteau, J; Buchovecky, M; Buckley, J H; Bugaev, V; Byrum, K; Cerruti, M; Chen, X; Ciupik, L; Connolly, M P; Cui, W; Eisch, J D; Errando, M; Falcone, A; Feng, Q; Finley, J P; Fleischhack, H; Fortin, P; Fortson, L; Furniss, A; Gillanders, G H; Griffin, S; Grube, J; Gyuk, G; Hütten, M; Hakansson, N; Hanna, D; Holder, J; Humensky, T B; Johnson, C A; Kaaret, P; Kar, P; Kelley-Hoskins, N; Kertzman, M; Kieda, D; Krause, M; Krennrich, F; Kumar, S; Lang, M J; Maier, G; McArthur, S; McCann, A; Meagher, K; Moriarty, P; Mukherjee, R; Nguyen, T; Nieto, D; De Bhróithe, A O'Faoláin; Ong, R A; Otte, A N; Park, N; Perkins, J S; Pichel, A; Pohl, M; Popkow, A; Pueschel, E; Quinn, J; Ragan, K; Reynolds, P T; Richards, G T; Roache, E; Rovero, A C; Santander, M; Sembroski, G H; Shahinyan, K; Smith, A W; Staszak, D; Telezhinsky, I; Tucci, J V; Tyler, J; Vincent, S; Wakely, S P; Weiner, O M; Weinstein, A; Williams, D A; Zitzer, B; Fumagalli, M; Prochaska, J X

    2016-01-01

    Between the beginning of its full-scale scientific operations in 2007 and 2012, the VERITAS Cherenkov telescope array observed more than 130 blazars; of these, 26 were detected as very-high-energy (VHE; E>100 GeV) {\\gamma}-ray sources. In this work, we present the analysis results of a sample of 114 undetected objects. The observations constitute a total live-time of ~570 hours. The sample includes several unidentified Fermi-Large Area Telescope (LAT) sources (located at high Galactic latitude) as well as all the sources from the second Fermi-LAT catalog which are contained within the field of view of the VERITAS observations. We have also performed optical spectroscopy measurements in order to estimate the redshift of some of these blazars that do not have a spectroscopic distance estimate. We present new optical spectra from the Kast instrument on the Shane telescope at the Lick observatory for 18 blazars included in this work, which allowed for the successful measurement or constraint on the redshift of fo...

  8. Unusual Flaring Activity in the Blazar PKS 1424-418 during 2008-2011

    CERN Document Server

    Buson, S; Larsson, S; Cutini, S; Finke, J; Ciprini, S; Ojha, R; D'Ammando, F; Donato, D; Thompson, D J; Desiante, R; Bastieri, D; Wagner, S; Hauser, M; Fuhrmann, L; Dutka, M; Müller, C; Kadler, M; Angelakis, E; Zensus, J A; Stevens, J; Blanchard, J M; Edwards, P G; Lovell, J E J; Gurwell, M A; Wehrle, A E; Zook, A

    2014-01-01

    Context. Blazars are a subset of active galactic nuclei (AGN) with jets that are oriented along our line of sight. Variability and spectral energy distribution (SED) studies are crucial tools for understanding the physical processes responsible for observed AGN emission. Aims. We report peculiar behaviour in the bright gamma-ray blazar PKS 1424-418 and use its strong variability to reveal information about the particle acceleration and interactions in the jet. Methods. Correlation analysis of the extensive optical coverage by the ATOM telescope and nearly continuous gamma-ray coverage by the Fermi Large Area Telescope is combined with broadband, time-dependent modeling of the SED incorporating supplemental information from radio and X-ray observations of this blazar. Results. We analyse in detail four bright phases at optical-GeV energies. These flares of PKS 1424-418 show high correlation between these energy ranges, with the exception of one large optical flare that coincides with relatively low gamma-ray a...

  9. ANTARES Constrains a Blazar Origin of Two IceCube PeV Neutrino Events

    CERN Document Server

    Adrián-Martínez, S; André, M; Anton, G; Ardid, M; Aubert, J -J; Baret, B; Barrios, J; Basa, S; Bertin, V; Biagi, S; Bogazzi, C; Bormuth, R; Bou-Cabo, M; Bouwhuis, M C; Bruijn, R; Brunner, J; Busto, J; Capone, A; Caramete, L; Carr, J; Chiarusi, T; Circella, M; Coniglione, R; Core, L; Costantini, H; Coyle, P; Creusot, A; De Rosa, G; Dekeyser, I; Deschamps, A; De Bonis, G; Distefano, C; Donzaud, C; Dornic, D; Dorosti, Q; Drouhin, D; Dumas, A; Eberl, T; Enzenhöfer, A; Escoffier, S; Fehn, K; Felis, I; Fermani, P; Folger, F; Fusco, L A; Galatà, S; Gay, P; Geißelsöder, S; Geyer, K; Giordano, V; Gleixner, A; Gómez-González, J P; Graf, K; Guillard, G; van Haren, H; Heijboer, A J; Hello, Y; Hernández-Rey, J J; Herold, B; Herrero, A; Hößl, J; Hofestädt, J; Hugon, C; James, C W; de Jong, M; Kalekin, O; Katz, U; Kießling, D; Kooijman, P; Kouchner, A; Kulikovskiy, V; Lahmann, R; Lambard, E; Lambard, G; Lefèvre, D; Leonora, E; Loehner, H; Loucatos, S; Mangano, S; Marcelin, M; Margiotta, A; Martínez-Mora, J A; Martini, S; Mathieu, A; Michael, T; Migliozzi, P; Neff, M; Nezri, E; Palioselitis, D; Păvălaş, G E; Pellegrino, C; Perrina, C; Piattelli, P; Popa, V; Pradier, T; Racca, C; Riccobene, G; Richter, R; Roensch, K; Rostovtsev, A; Saldaña, M; Samtleben, D F E; Sánchez-Losa, A; Sanguineti, M; Sapienza, P; Schmid, J; Schnabel, J; Schulte, S; Schüssler, F; Seitz, T; Sieger, C; Spies, A; Spurio, M; Steijger, J J M; Stolarczyk, Th; Taiuti, M; Tamburini, C; Tayalati, Y; Trovato, A; Vallage, B; Vallée, C; Van Elewyck, V; Visser, E; Vivolo, D; Wagner, S; de Wolf, E; Yatkin, K; Yepes, H; Zornoza, J D; Zúñiga, J; :,; Krauß, F; Kadler, M; Mannheim, K; Schulz, R; Trüstedt, J; Wilms, J; Ojha, R; Ros, E; Baumgartner, W; Beuchert, T; Blanchard, J; Bürkel, C; Carpenter, B; Edwards, P G; Glawion, D Eisenacher; Elsässer, D; Fritsch, U; Gehrels, N; Gräfe, C; Großberger, C; Hase, H; Horiuchi, S; Kappes, A; Kreikenbohm, A; Kreykenbohm, I; Langejahn, M; Leiter, K; Litzinger, E; Lovell, J E J; Müller, C; Phillips, C; Plötz, C; Quick, J; Steinbring, T; Stevens, J; Thompson, D J; Tzioumis, A K

    2015-01-01

    The source(s) of the neutrino excess reported by the IceCube Collaboration is unknown. The TANAMI Collaboration recently reported on the multiwavelength emission of six bright, variable blazars which are positionally coincident with two of the most energetic IceCube events. Such objects are prime candidates to be the source of the highest-energy cosmic rays, and thus of associated neutrino emission. We present an analysis of neutrino emission from the six blazars using observations with the ANTARES neutrino telescope. The standard methods of the ANTARES candidate list search are applied to six years of data to search for an excess of muons - and hence their neutrino progenitors - from the directions of the six blazars described by the TANAMI Collaboration, and which are possibly associated with two IceCube events. Monte Carlo simulations of the detector response to both signal and background particle fluxes are used to estimate the sensitivity of this analysis for different possible source neutrino spectra. A...

  10. 5 year Global 3-mm VLBI survey of Gamma-ray active blazars

    CERN Document Server

    Hodgson, J A; Marscher, A P; Jorstad, S G; Marti-Vidal, I; Lindqvist, M; Bremer, M; Sanchez, S; de Vicente, P; Zensus, J A

    2015-01-01

    The Global mm-VLBI Array (GMVA) is a network of 14 3\\,mm and 7\\,mm capable telescopes spanning Europe and the United States, with planned extensions to Asia. The array is capable of sensitive maps with angular resolution often exceeding 50\\,$\\mu$as. Using the GMVA, a large sample of prominent $\\gamma$-ray blazars have been observed approximately 6 monthly from later 2008 until now. Combining 3\\,mm maps from the GMVA with near-in-time 7\\,mm maps from the VLBA-BU-BLAZAR program and 2\\,cm maps from the MOJAVE program, we determine the sub-pc morphology and high frequency spectral structure of $\\gamma$-ray blazars. The magnetic field strength can be estimated at different locations along the jet under the assumption of equipartition between magnetic field and relativistic particle energies. Making assumptions on the jet magnetic field configuration (e.g. poloidal or toroidal), we can estimate the separation of the mm-wave "core" and the jet base, and estimate the strength of the magnetic field there. The results ...

  11. The jets-accretion relation, mass-luminosity relation in Fermi blazars

    CERN Document Server

    Yu, Xiaoling; Zhang, Haojing; Xiong, Dingrong; Li, Bijun; Cha, Yongjuan; Chen, Yongyun; Huang, Xia; Wang, Yuwei

    2015-01-01

    A sample of 111 Fermi blazars each with a well-established radio core luminosity, broad-line luminosity, bolometric luminosity and black hole mass has been compiled from the literatures.We present a significant correlation between radio core and broad-line emission luminosities that supports a close link between accretion processes and relativistic jets. Analysis reveals a relationship of $\\rm{LogL_{BLR}\\sim(0.81\\pm0.06)LogL_{R}^{C}}$ which is consistant with theoretical predicted coefficient and supports that blazar jets are powered by energy extraction from a rapidly spinning Kerr black hole through the magnetic field provided by the accretion disk. Through studying the correlation between the intrinsic bolometric luminosity and the black hole mass, we find a relationship of $\\rm{{Log}\\frac{L_{in}}{L_{\\odot}}=(0.95\\pm0.26){Log}\\frac{M}{M_{\\odot}}+(3.53\\pm2.24)}$ which supports mass-luminosity relation for Fermi blazars derived in this work is a powerlaw relation similar to that for main-sequence stars. Fina...

  12. INTEGRAL observations of the blazar 3C454.3 in outburst

    CERN Document Server

    Pian, E; Beckmann, V; Pian, Elena; Foschini, Luigi; Beckmann, Volker

    2006-01-01

    In Spring 2005, the blazar 3C454.3 underwent a dramatic outburst at all wavelengths from mm to X-rays. This prompted INTEGRAL observations, accomplished in 15-18 May 2005. The source was detected by the INTEGRAL instruments from 3 to 200 keV in a bright state (~5 x 10E-10 cgs), at least a factor of 2-3 higher than previously observed. This is one of the brightest blazar detections achieved by INTEGRAL. During the 2.5 days of INTEGRAL monitoring, we detected a ~20% decrease in the hard X-rays (20-40 keV), indicating that we have sampled the decaying part of the flare. The decrease is less apparent in the soft X-rays (5-15 keV). The simultaneous optical variations are weakly correlated with those at soft X-rays, and not clearly correlated with those at hard X-rays. The spectral energy distribution exhibits two components, as typically seen in blazars, which can be modeled with synchrotron radiation and inverse Compton scattering occurring in a region external to the broad line region.

  13. Multi-TeV flaring from blazars: Markarian 421 as a case study

    Energy Technology Data Exchange (ETDEWEB)

    Sahu, Sarira; Miranda, Luis Salvador [Universidad Nacional Autonoma de Mexico, Instituto de Ciencias Nucleares, Mexico, DF (Mexico); Rajpoot, Subhash [California State University, Department of Physics and Astronomy, Long Beach, CA (United States)

    2016-03-15

    The TeV blazar Markarian 421 underwent multi-TeV flaring during April 2004 and simultaneously observations in the X-ray and TeV energies were made. It was observed that the TeV outbursts had no counterparts in the lower energy range. One implication of this is that it might be an orphan flare. We show that Fermi-accelerated protons of energy ≤ 168 TeV can interact with the low energy tail of the background synchrotron self-Compton photons in the inner region of the blazar to produce the multi-TeV flare and our results fit very well with the observed spectrum. Based on our study, we predict that the blazars with a deep valley in between the end of the synchrotron spectrum and the beginning of the SSC spectrum are possible candidates for orphan flaring. Future possible candidates for this scenario are the HBLs Mrk 501 and PG 1553 + 113 objects. (orig.)

  14. Temporal Correlations Between Optical and Gamma-ray Activity in Blazars

    CERN Document Server

    Cohen, Daniel P; Filippenko, Alexei V; Cenko, S Bradley; Lott, Benoit; Zheng, WeiKang; Li, Weidong

    2014-01-01

    We have been using the 0.76-m Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory to optically monitor a sample of 157 blazars that are bright in $\\gamma$-rays, being detected with high significance (test-statistic TS $> 100$, i.e., $\\ge 10\\sigma$) in one year by the Large Area Telescope (LAT) on the {\\it Fermi} Gamma-ray Space Telescope. We attempt to observe each source on a 3-day cadence with KAIT, subject to weather and seasonal visibility. The $\\gamma$-ray coverage is essentially continuous. KAIT observations extend over much of the 5-year Fermi mission for several objects, and most have $>$100 optical measurements spanning the last three years. These blazars (flat-spectrum radio quasars and BL Lac objects) exhibit a wide range of flaring behavior. Using the discrete correlation function (DCF), here we search for temporal relationships between optical and $\\gamma$-ray light curves in the 40 brightest sources in hopes of placing constraints on blazar acceleration and emission zones. We find str...

  15. Blazar Flaring Patterns (B-FlaP): Classifying Blazar Candidates of Uncertain type in the third Fermi-LAT catalog by Artificial Neural Networks

    CERN Document Server

    Chiaro, G; La Mura, G; Giroletti, M; Thompson, D J; Bastieri, D

    2016-01-01

    The Fermi Large Area Telescope (LAT) is currently the most important facility for investigating the GeV $\\gamma$-ray sky. With Fermi LAT more than three thousand $\\gamma$-ray sources have been discovered so far. 1144 ($\\sim40\\%$) of the sources are active galaxies of the blazar class, and 573 ($\\sim20\\%$) are listed as Blazar Candidate of Uncertain type (BCU), or sources without a conclusive classification. We use the Empirical Cumulative Distribution Functions (ECDF) and the Artificial Neural Networks (ANN) for a fast method of screening and classification for BCUs based on data collected at $\\gamma$-ray energies only, when rigorous multiwavelength analysis is not available. Based on our method, we classify 342 BCUs as BL Lacs and 154 as FSRQs, while 77 objects remain uncertain. Moreover, radio analysis and direct observations in ground-based optical observatories are used as counterparts to the statistical classifications to validate the method. This approach is of interest because of the increasing number ...

  16. OPTICAL SPECTROSCOPIC OBSERVATIONS OF GAMMA-RAY BLAZAR CANDIDATES. IV. RESULTS OF THE 2014 FOLLOW-UP CAMPAIGN

    Energy Technology Data Exchange (ETDEWEB)

    Ricci, F. [Dipartimento di Matematica e Fisica, Università Roma Tre, via della Vasca Navale 84, I-00146, Roma (Italy); Massaro, F. [Dipartimento di Fisica, Università degli Studi di Torino, via Pietro Giuria 1, I-10125 Torino (Italy); Landoni, M. [INAF-Osservatorio Astronomico di Brera, Via Emilio Bianchi 46, I-23807 Merate (Italy); D’Abrusco, R.; Milisavljevic, D.; Paggi, A.; Smith, Howard A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Stern, D. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Mail Stop 169-221, Pasadena, CA 91109 (United States); Masetti, N. [INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, via Gobetti 101, I-40129, Bologna (Italy); Tosti, G., E-mail: riccif@fis.uniroma3.it [Dipartimento di Fisica, Università degli Studi di Perugia, I-06123 Perugia (Italy)

    2015-05-15

    The extragalactic γ-ray sky is dominated by the emission arising from blazars, one of the most peculiar classes of radio-loud active galaxies. Since the launch of Fermi several methods were developed to search for blazars as potential counterparts of unidentified γ-ray sources (UGSs). To confirm the nature of the selected candidates, optical spectroscopic observations are necessary. In 2013 we started a spectroscopic campaign to investigate γ-ray blazar candidates selected according to different procedures. The main goals of our campaign are: (1) to confirm the nature of these candidates, and (2) whenever possible, determine their redshifts. Optical spectroscopic observations will also permit us to verify the robustness of the proposed associations and check for the presence of possible source class contaminants to our counterpart selection. This paper reports the results of observations carried out in 2014 in the northern hemisphere with Kitt Peak National Observatory and in the southern hemisphere with the Southern Astrophysical Research telescopes. We also report three sources observed with the Magellan and Palomar telescopes. Our selection of blazar-like sources that could be potential counterparts of UGSs is based on their peculiar infrared colors and on their combination with radio observations both at high and low frequencies (i.e., above and below ∼1 GHz) in publicly available large radio surveys. We present the optical spectra of 27 objects. We confirm the blazar-like nature of nine sources that appear to be potential low-energy counterparts of UGSs. Then we present new spectroscopic observations of 10 active galaxies of uncertain type associated with Fermi sources, classifying all of them as blazars. In addition, we present the spectra for five known γ-ray blazars with uncertain redshift estimates and three BL Lac candidates that were observed during our campaign. We also report the case for WISE J173052.85−035247.2, candidate counterpart of the

  17. Optical archival spectra of blazar candidates of uncertain type in the 3$^{rd}$ Fermi Large Area Telescope Catalog

    CERN Document Server

    Crespo, N Álvarez; D'Abrusco, R; Landoni, M; Masetti, N; Chavushyan, V; Jiménez-Bailón, E; La Franca, F; Milisavljevic, D; Paggi, A; Patiño-Álvarez, V; Ricci, F; Smith, Howard A

    2016-01-01

    Despite the fact that blazars constitute the rarest class among active galactic nuclei (AGNs) they are the largest known population of associated $\\gamma$-ray sources. Many of the $\\gamma$-ray objects listed in the Fermi-Large Area Telescope Third Source catalog (3FGL) are classified as blazar candidates of uncertain type (BCUs), either because they show multifrequency behaviour similar to blazars but lacking optical spectra in the literature, or because the quality of such spectra is too low to confirm their nature. Here we select, out of 585 BCUs in the 3FGL, 42 BCUs which we identify as probable blazars by their WISE infrared colors and which also have optical spectra that are available in the Sloan Digital Sky Survey (SDSS) and/or Six-Degree Field Galaxy Survey Database (6dFGS). We confirm the blazar nature of all of the sources. We furthermore conclude that 28 of them are BL Lacs, 8 are radio-loud quasars with flat radio spectrum and 6 are BL Lac whose emission is dominated by their host galaxy.

  18. Photopolarimetric monitoring of 41 blazars in the optical and near-infrared bands with the Kanata telescope

    CERN Document Server

    Ikejiri, Y; Sasada, M; Sakimoto, K; Ito, R; Yamanaka, M; Arai, A; Fukazawa, Y; Ohsugi, T; Kawabata, K S

    2009-01-01

    Blazars are a kind of active galactic nuclei (AGN) in which a relativistic jet is considered to be directed along the line of sight. They are characterized by strong and rapid variability of the flux and high polarization. We performed a monitoring of 41 blazars in the optical and near-infrared regions from 2008 to 2009 using TRISPEC attached to the "Kanata" 1.5-m telescope. In this paper, we report the correlation of the flux, color and polarization using our data, and discuss universal features for blazars, which have not fully been established. Three blazars (3C 454.3, QSO 0454$-$234, and PKS 1510$-$089) tended to be redder when they were brighter, only during their faint states. This color behavior suggests that the contribution of a thermal component is strong in the faint states for those objects. Excluding this "redder-when-brighter" phase, we found that 24 blazars tended to be bluer when they were brighter. This number corresponds to 83% among well-observed objects which we observed for $>10$ nights. ...

  19. Optical archival spectra of blazar candidates of uncertain type in the 3rd Fermi Large Area Telescope Catalog

    Science.gov (United States)

    Álvarez Crespo, N.; Massaro, F.; D'Abrusco, R.; Landoni, M.; Masetti, N.; Chavushyan, V.; Jiménez-Bailón, E.; La Franca, F.; Milisavljevic, D.; Paggi, A.; Patiño-Álvarez, V.; Ricci, F.; Smith, Howard A.

    2016-09-01

    Despite the fact that blazars constitute the rarest class among active galactic nuclei (AGNs) they are the largest known population of associated γ-ray sources. Many of the γ-ray objects listed in the Fermi-Large Area Telescope Third Source catalog (3FGL) are classified as blazar candidates of uncertain type (BCUs), either because they show multifrequency behavior similar to blazars but lacking optical spectra in the literature, or because the quality of such spectra is too low to confirm their nature. Here we select, out of 585 BCUs in the 3FGL, 42 BCUs which we identify as probable blazars by their WISE infrared colors and which also have optical spectra that are available in the Sloan Digital Sky Survey (SDSS) and/or Six-Degree Field Galaxy Survey Database (6dFGS). We confirm the blazar nature of all of the sources. We furthermore conclude that 28 of them are BL Lacs, 8 are radio-loud quasars with flat radio spectrum and 6 are BL Lac whose emission is dominated by their host galaxy.

  20. A Comprehensive Statistical Description of Radio-Through-$\\gamma$-Ray Spectral Energy Distributions of All Known Blazars

    CERN Document Server

    Mao, Peiyuan; Massaro, Francesco; Paggi, Alessandro; Cauteruccio, Joe; Künzel, Soren R

    2016-01-01

    We combined multi-wavelength data for blazars from the Roma-BZCAT catalog and analyzed hundreds of X-ray spectra. We present the fluxes and Spectral Energy Distributions (SEDs), in 12 frequency bands from radio to $\\gamma$-rays, for a final sample of 2214 blazars. Using a model-independent statistical approach, we looked for systematic trends in the SEDs; the most significant trends involved the radio luminosities and X-ray spectral indices of the blazars. We used a Principal Component Analysis (PCA), to determine the basis vectors of the blazar SEDs and, in order to maximize the size of the sample, imputed missing fluxes using the K-nearest neighbors method. Using more than an order of magnitude more data than was available when Fossati et al. (1997, 1998) first reported trends of SED shape with blazar luminosity, we confirmed the anti-correlation between radio luminosity and synchrotron peak frequency, although with greater scatter than was seen in the smaller sample. The same trend can be seen between bolo...

  1. The Outburst of the Blazar S5 0716+71 in 2011 October: Shock in a Helical Jet

    CERN Document Server

    Larionov, V M; Marscher, A P; Morozova, D A; Blinov, D A; Hagen-Thorn, V A; Konstantinova, T S; Kopatskaya, E N; Larionova, L V; Larionova, E G; Troitsky, I S

    2013-01-01

    We present the results of optical (R band) photometric and polarimetric monitoring and Very Long Baseline Array (VLBA) imaging of the blazar S5 0716+714 along with Fermi gamma-ray data during a multi-waveband outburst in 2011 October. We analyze total and polarized intensity images of the blazar obtained with the VLBA at 43 GHz during and after the outburst. Monotonic rotation of the linear polarization vector at a rate of >50 degrees per night coincided with a sharp maximum in gamma-ray and optical flux. At the same time, within the uncertainties, a new superluminal knot appeared, with an apparent speed of ~21c. The general multi-frequency behavior of the outburst can be explained within the framework of a shock wave propagating along a helical path in the blazar's jet.

  2. Probing Precise Location of Radio Core in TeV Blazar Mrk 501 with VERA at 43 GHz

    CERN Document Server

    Koyama, S; Doi, A; Niinuma, K; Hada, K; Nagai, H; Honma, M; Akiyama, K; Giroletti, M; Giovannini, G; Orienti, M; Isobe, N; Kataoka, J; Paneque, D; Kobayashi, H; Asada, K

    2015-01-01

    We investigate the position of the radio core in a blazar by multi-epoch astrometric observations at 43 GHz. Using the VLBI Exploration of Radio Astrometry (VERA), we have conducted four adjacent observations in February 2011 and another four in October 2011, and succeeded in measuring the position of the radio core in the TeV blazar Mrk 501 relative to a distant compact quasar NRAO 512. During our observations, we find that (1) there is no positional change within ~0.2 mas or ~2.0 pc de-projected with $\\pm1\\sigma$ error for the weighted-mean phase-referenced positions of Mrk 501 core relative to NRAO 512 over four adjacent days, and (2) there is an indication of position change for 3C 345 core relative to NRAO 512. By applying our results to the standard internal shock model for blazars, we constrain the bulk Lorenz factors of the ejecta.

  3. The New Surprising Behaviour of the Two 'Prototype' Blazars PKS 2155-304 and 3C 279

    Energy Technology Data Exchange (ETDEWEB)

    Costamante, Luigi; /Stanford U., HEPL /KIPAC, Menlo Park; Aharonian, Felix; /Heidelberg, Max Planck Inst.; Buhler, Rolf; /Heidelberg, Max Planck Inst.; Khangulyan, Dmitry; /Heidelberg, Max Planck Inst.; Reimer, Anita; /Stanford U., HEPL /KIPAC, Menlo Park; Reimer, Olaf; /Stanford U., HEPL /KIPAC, Menlo Park

    2011-11-21

    Recent VHE observations have unveiled a surprising behaviour in two well-known blazars at opposite sides of the blazar sequence. PKS 2155-304 have shown for the first time in an HBL a large Compton dominance, high {gamma}-ray luminosities and a cubic relation between X-ray and VHE fluxes. 3C 279 is the first FSRQ detected at VHE. The high luminosity required to overcome the significant absorption caused by the BLR emission cannot be easily reconciled with the historical and quasi-simultaneous SED properties. Both cases shed a new light on the structure and ambient fields of blazars. Contrary to previous claims, it is also shown that 3C 279 - as any FSRQ - cannot provide robust constraints on the EBL.

  4. Optical spectroscopic observations of gamma-ray blazar candidates IV. Results of the 2014 follow-up campaign

    CERN Document Server

    Ricci, F; Landoni, M; D'Abrusco, R; Milisavljevic, D; Stern, D; Masetti, N; Paggi, A; Smith, Howard A; Tosti, G

    2015-01-01

    The extragalactic gamma-ray sky is dominated by the emission arising from blazars, one of the most peculiar classes of radio-loud active galaxies. Since the launch of Fermi several methods were developed to search for blazars as potential counterparts of unidentified gamma-ray sources (UGSs). To confirm the nature of the selected candidates, optical spectroscopic observations are necessary. In 2013 we started a spectroscopic campaign to investigate gamma-ray blazar candidates selected according to different procedures. The main goals of our campaign are: 1) to confirm the nature of these candidates, and 2) whenever possible determine their redshifts. Optical spectroscopic observations will also permit us to verify the robustness of the proposed associations and check for the presence of possible source class contaminants to our counterpart selection. This paper reports the results of observations carried out in 2014 in the Northern hemisphere with Kitt Peak National Observatory (KPNO) and in the Southern hemi...

  5. Analysis of the cumulative neutrino flux from Fermi LAT blazar populations using 3 years of IceCube data

    Directory of Open Access Journals (Sweden)

    Glüsenkamp Thorsten

    2016-01-01

    Full Text Available The recent discovery of a diffuse neutrino flux up to PeV energies raises the question of which populations of astrophysical sources contribute to this diffuse signal. One extragalactic candidate source population to produce high-energy neutrinos are Blazars. We present results from a likelihood analysis searching for cumulative neutrino emission from Blazar populations selected with the 2nd Fermi LAT AGN catalogue (2LAC using an IceCube data set that has been optimized for the detection of individual sources. In contrast to previous searches with IceCube, the investigated populations contain up to hundreds of sources, the biggest one being the entire Blazar sample measured by the Fermi-LAT. No significant neutrino signal was found from any of these populations. Some implications of this non-observation for the origin of the observed PeV diffuse signal will be discussed.

  6. Multi-wavelength Study of Blazars Using Variability as a Tool

    Science.gov (United States)

    Baliyan, Kiran S.; Kaur, Navpreet; Chandra, Sunil; Sameer, Sameer; Ganesh, Shashikiran

    2016-09-01

    Active galactic nuclei (AGN) are too compact to be resolved by any existing optical telescope facility, making it difficult to understand their structure and the emission processes responsible for their huge energy output. However, variability, one of their characteristic properties, provides a tool to probe the inner regions of AGN. Blazars are the best candidates for such a study, and hence a considerable amount of effort is being made to investigate variability in these sources across the electromagnetic spectrum. Here, using the Mt. Abu infrared observatory (MIRO) blazar monitoring program, we present intra-night, inter-night, and long term aspects of the variability in S5 0716+71, 3C66A, and OJ 287. These stars show significant variability on short (a few tens of mins, to a few hours, to a few days) to long term (months to years) timescales. Based on the light travel time argument, the shortest variability timescales (micro-variability) provide upper limits to the size of the emission region. While S5 0716 shows a very high duty cycle of variability (> 80 %), 3C66A shows a much lower intra day variability (IDV) duty cycle (< 20 %). All three show rapid variations within 2.5 to 3.5 hr, which, perhaps, are generated near the vicinity of black holes. Assuming this, estimates of the masses of the black holes are made at 10^{9} , 8×10^{8}, and 2.7×10^{9} M⨀ for S5 0716+71, 3C66A, and OJ 287, respectively. Multi-wavelength light-curves for the blazar PKS 1510-089 are discussed to infer the emission processes responsible for the recent flaring episodes in this source.

  7. Optical Counterparts of Undetermined Type -Ray Active Galactic Nuclei with Blazar-Like Spectral Energy Distributions

    Indian Academy of Sciences (India)

    Giovanni La Mura; Graziano Chiaro; Stefano Ciroi; Piero Rafanelli; David Salvetti; Marco Berton; Valentina Cracco; Fermi-LAT collaboration

    2015-12-01

    During its first four years of scientific observations, the Fermi Large Area Telescope (Fermi-LAT) detected 3033 -ray sources above a 4 significance level. Although most of the extra-galactic sources are active galactic nuclei (AGN) of the blazar class, other families of AGNs are observed too, while a still high fraction of detections (∼30%) remains with uncertain association or classification. According to the currently accepted interpretation, the AGN -ray emission arises from inverse Compton (IC) scattering of low energy photons by relativistic particles confined in a jet, which, in the case of blazars, is oriented very close to our line-of-sight. Taking advantage of data from radio and X-ray wavelengths, which we expect to be produced together with -rays, providing a much better source localization potential, we focused our attention on a sample of -ray Blazar Candidates of Undetermined type (BCUs), starting a campaign of optical spectroscopic observations. The main aims of our investigation include a census of the AGN families that contribute to -ray emission and a study of their redshift distribution, with the subsequent implications on the intrinsic source power. We furthermore analyze which -ray properties can better constrain the nature of the source, thus helping in the study of objects not yet associated with a reliable low frequency counterpart. Here we report on the instruments and techniques used to identify the optical counterparts of -ray sources, we give an overview on the status of our work, and we discuss the implications of a large scale study of -ray emitting AGNs.

  8. An Emerging Class of Gamma-ray Flares from Blazars: Beyond One-zone Models

    Science.gov (United States)

    Tavani, M.; Vittorini, V.; Cavaliere, A.

    2015-11-01

    Blazars radiate from relativistic plasma jets with bulk Lorentz factors {{Γ }}∼ 10, closely aligned along our line of sight. In a number of blazars of the flat-spectrum radio quasar type, such as 3C 454.3 and 3C 279, gamma-ray flares have recently been detected with very high luminosity and few or no counterparts in the optical and soft X-ray bands. They challenge the current one-zone leptonic models of emissions from within the broad-line region (BLR). The latter envisage the optical/X-ray emissions to be produced as synchrotron radiation by the same population of highly relativistic electrons in the jet that would also yield the gamma rays by inverse Compton upscattering of surrounding soft photons. To meet the challenge, we present here a model based on primary synchrotron photons emitted in the BLR by a plasmoid moving out with the jet and scattered back toward the incoming plasmoid by an outer plasma clump acting as a mirror. We consider both a scenario based on a static mirror located outside the BLR and an alternative provided by a moving mirror geometry. We show that mirroring phenomena can locally enhance the density and anisotropy with associated relativistic boosting of soft photons within the jet, so as to trigger bright inverse Compton gamma-ray transients from nearly steady optical/X-ray synchrotron emissions. In this picture we interpret the peculiarly asymmetric light curves of the recently detected gamma-ray flares from 3C 279. Our scenario provides a promising start to understanding the widening class of bright and transient gamma-ray activities in blazars.

  9. Measurement of the blazar Mrk421 flux above 60 GeV with the CELESTE experiment

    International Nuclear Information System (INIS)

    The CELESTE experiment is based on an ancient solar plant that has been turned into a detector able to detect the particle showers triggered by the interactions of high energy cosmic photons with the earth atmosphere nuclei. The purpose of the CELESTE experiment is to study the emissions of photons by cosmic objects like supernovae remnants, pulsars or active cores of galaxies such as blazars. Blazars are very interesting objects to study because they allow us to investigate matter that is in extreme conditions and to probe a very far past. The aim of this work has been to develop methods for the analysis of the data collected by CELESTE and to validate them. A specific effort has been achieved for the selection of efficient hadronic rejection criteria in order to optimize the sensitivity of the detector. The physics of the detector is detailed from the particle showers to the data analysis. The detector acceptance has been assessed through Monte-Carlo simulations that have been shown that the detection threshold is 30 GeV at the triggering point and 60 GeV after the analysis cuts. The validation tests have been performed on the Crab nebula that is a standard in gamma astronomy for its stability and intensity. CELESTE has been operating since November 1999 in a satisfactory way and has accumulated data on 4 blazars among them Mrk421. Several bursts have been detected on Mrk421 and an average photon flux has been determined. A correlation has been deduced from the activity detected by CELESTE and the activities in the TeV and X ranges which agrees with the simulations

  10. Results from the Blazar Monitoring Campaign at the Whipple 10m Gamma-ray Telescope

    CERN Document Server

    Steele, David; Charlot, P; Kurtanidze, O; Lahteenmaki, A; Montaruli, T; Sadun, A C; Villata, M

    2007-01-01

    In September 2005, the observing program of the Whipple 10 m gamma-ray telescope was redefined to be dedicated almost exclusively to AGN monitoring. Since then the five Northern Hemisphere blazars that had already been detected at Whipple are monitored routinely each night that they are visible. Thanks to the efforts of a large number of multiwavelength collaborators, the first year of this program has been very successful. We report here on the analysis of Markarian 421 observations taken from November, 2005 to May, 2006 in the gamma-ray, X-ray, optical and radio bands.

  11. A Dramatic Optical Flare and Microvariability in the Blazar 3C 454.3

    Science.gov (United States)

    Balonek, Thomas J.; Boni, Samantha J.; Chapman, Katie J.; Didio, Nicholas A.; Sabyr, Alina; Stahlin, R. William; Weaver, Zachary R.; Zhang, Saiyang

    2016-06-01

    Following up on the report of optical and gamma-ray activity in the blazar 3C 454.3 by Jorstad (ATel# 9150), Lucarelli et al (ATel #9157), and Bulgarelli et al (ATel #9176), we report optical (R) observations which reveal a brightening of over 2 magnitudes in a 10 day interval between 2016 June 10 and 20. The brightness on June 20 (R = 13.7) is 1.2 magnitudes brighter than reported by Jorstad on June 13, and is the brightest 3C 454.3 has been observed in two years.

  12. Numerical study of broadband spectra caused by internal shocks in magnetized relativistic jets of blazars

    CERN Document Server

    Rueda-Becerril, Jesus M; Aloy, Miguel A; Aloy, Carmen

    2013-01-01

    The internal-shocks scenario in relativistic jets has been used to explain the variability of blazars' outflow emission. Recent simulations have shown that the magnetic field alters the dynamics of these shocks producing a whole zoo of spectral energy density patterns. However, the role played by magnetization in such high-energy emission is still not entirely understood. With the aid of \\emph{Fermi}'s second LAT AGN catalog, a comparison with observations in the $\\gamma$-ray band was performed, in order to identify the effects of the magnetic field.

  13. The many faces of blazar emission in the context of hadronic models

    CERN Document Server

    Petropoulou, Maria; Padovani, Paolo; Resconi, Elisa; Giommi, Paolo; Mastichiadis, Apostolos

    2016-01-01

    We present two ways of modeling the spectral energy distribution of blazars in the hadronic context and discuss the predictions of each "hadronic variant" on the spectral shape, the multi-wavelength variability, the cosmic-ray flux, and the high-energy neutrino emission. Focusing on the latter, we then present an application of the hadronic model to individual BL Lacs that were recently suggested to be the counterparts of some of the IceCube neutrinos, and conclude by discussing the contribution of the whole BL Lac class to the observed neutrino background.

  14. Broad Band Observations of Gravitationally Lensed Blazar during a Gamma-Ray Outburst

    Directory of Open Access Journals (Sweden)

    Julian Sitarek

    2016-09-01

    Full Text Available QSO B0218+357 is a gravitationally lensed blazar located at a cosmological redshift of 0.944. In July 2014 a GeV flare was observed by Fermi-LAT, triggering follow-up observations with the MAGIC telescopes at energies above 100 GeV. The MAGIC observations at the expected time of arrival of the trailing component resulted in the first detection of QSO B0218+357 in Very-High-Energy (VHE, >100 GeV gamma rays. We report here the observed multiwavelength emission during the 2014 flare.

  15. Fermi LAT detection of renewed activity from the blazar PKS 1502+106

    Science.gov (United States)

    Ciprini, Stefano

    2015-06-01

    The Large Area Telescope (LAT), one of two instruments on the Fermi Gamma-ray Space Telescope, has observed increasing gamma-ray flux from a source positionally consistent with the flat spectrum radio quasar PKS 1502+106 (also known as OR 103, S3 1502+10 and 3FGL J1504.4+1029, Acero et al., arXiv:1501.02003), with radio coordinates, (J2000.0), R.A.: 226.10408 deg, Dec: 10.49422 deg (Johnston et al. 1995, AJ, 110, 880). This blazar has a redshift of z=1.8383 (Hewett & Wild 2010, MNRAS, 405, 2302).

  16. The TANAMI Multiwavelength Program: Dynamic spectral energy distributions of southern blazars

    Science.gov (United States)

    Krauß, F.; Wilms, J.; Kadler, M.; Ojha, R.; Schulz, R.; Trüstedt, J.; Edwards, P. G.; Stevens, J.; Ros, E.; Baumgartner, W.; Beuchert, T.; Blanchard, J.; Buson, S.; Carpenter, B.; Dauser, T.; Falkner, S.; Gehrels, N.; Gräfe, C.; Gulyaev, S.; Hase, H.; Horiuchi, S.; Kreikenbohm, A.; Kreykenbohm, I.; Langejahn, M.; Leiter, K.; Lovell, J. E. J.; Müller, C.; Natusch, T.; Nesci, R.; Pursimo, T.; Phillips, C.; Plötz, C.; Quick, J.; Tzioumis, A. K.; Weston, S.

    2016-06-01

    Context. Simultaneous broadband spectral and temporal studies of blazars are an important tool for investigating active galactic nuclei (AGN) jet physics. Aims: We study the spectral evolution between quiescent and flaring periods of 22 radio-loud AGN through multiepoch, quasi-simultaneous broadband spectra. For many of these sources these are the first broadband studies. Methods: We use a Bayesian block analysis of Fermi/LAT light curves to determine time ranges of constant flux for constructing quasi-simultaneous spectral energy distributions (SEDs). The shapes of the resulting 81 SEDs are described by two logarithmic parabolas and a blackbody spectrum where needed. Results: The peak frequencies and luminosities agree well with the blazar sequence for low states with higher luminosity implying lower peak frequencies. This is not true for sources in high states. The γ-ray photon index in Fermi/LAT correlates with the synchrotron peak frequency in low and intermediate states. No correlation is present in high states. The black hole mass cannot be determined from the SEDs. Surprisingly, the thermal excess often found in FSRQs at optical/UV wavelengths can be described by blackbody emission and not an accretion disk spectrum. Conclusions: The so-called harder-when-brighter trend, typically seen in X-ray spectra of flaring blazars, is visible in the blazar sequence. Our results for low and intermediate states, as well as the Compton dominance, are in agreement with previous results. Black hole mass estimates using recently published parameters are in agreement with some of the more direct measurements. For two sources, estimates disagree by more than four orders of magnitude, possibly owing to boosting effects. The shapes of the thermal excess seen predominantly in flat spectrum radio quasars are inconsistent with a direct accretion disk origin. Tables of the fluxes are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or

  17. BeppoSAX Observations of the TeV Blazar Mkn 421

    International Nuclear Information System (INIS)

    The blazar Mkn 421 has been observed, as part of the AO1 Core Program, five times from 2 to 7 May 1997. In the LECS+MECS energy band the spectrum shows convex curvature, well represented by a broken power-law. Flux variability (more than a factor 2) has been detected over the entire 0.1-10 keV range, accompanying which the spectrum steepens with the decrease in intensity. Mkn 421 has been also detected with the PDS instrument. Our preliminary analysis indicates that the PDS spectrum lies significantly above the extrapolation from the MECS, suggesting a contribution from a flatter high energy component

  18. NuSTAR, Swift, and GROND observations of the flaring MeV blazar: PMN J0641$-$0320

    CERN Document Server

    Ajello, M; Paliya, V S; Kocevski, D; Tagliaferri, G; Madejski, G; Rau, A; Schady, P; Greiner, J; Massaro, F; Bakolovic, M; Buehler, R; Giomi, M; Marcotulli, L; D'Ammando, F; Stern, D; Boggs, S E; Christensen, F E; Craig, W W; Hailey, C J; Harrison, F A; Zhang, W W

    2016-01-01

    MeV blazars are a sub--population of the blazar family, exhibiting larger--than--average jet powers, accretion luminosities and black hole masses. Because of their extremely hard X--ray continua, these objects are best studied in the X-ray domain. Here, we report on the discovery by the $Fermi$ Large Area Telescope and subsequent follow-up observations with $NuSTAR$, $Swift$ and GROND of a new member of the MeV blazar family: PMN J0641$-$0320. Our optical spectroscopy provides confirmation that this is a flat--spectrum radio quasar located at a redshift of $z=1.196$. Its very hard $NuSTAR$ spectrum (power--law photon index of $\\sim$1 up to $\\sim$80 keV) indicates that the emission is produced via inverse Compton scattering off photons coming from outside the jet.The overall spectral energy distribution of PMN J0641$-$0320 is typical of powerful blazars and by reproducing it with a simple one-zone leptonic emission model we find the emission region to be located either inside the broad line region or within th...

  19. Optical spectroscopic observations of $\\gamma$-ray blazar candidates VI. Further observations from TNG, WHT, OAN, SOAR and Magellan telescopes

    CERN Document Server

    Crespo, N Álvarez; Milisavljevic, D; Landoni, M; Chavushyan, V; Patiño-Álvarez, V; Masetti, N; Jiménez-Bailón, E; Strader, J; Chomiuk, L; Katagiri, H; Kagaya, M; Cheung, C C; Paggi, A; D'Abrusco, R; Ricci, F; La Franca, F; Smith, Howard A; Tosti, G

    2016-01-01

    Blazars, one of the most extreme class of active galaxies, constitute so far the largest known population of $\\gamma$-ray sources and their number is continuously growing in the Fermi catalogs. However in the latest release of the Fermi catalog there is still a large fraction of sources that are classified as blazar candidate of uncertain type (BCUs) for which optical spectroscopic observations are necessary to confirm their nature and their associations. In addition about 1/3 of the $\\gamma$-ray point sources listed in the Third Fermi-LAT Source Catalog (3FGL) are still unassociated and lacking an assigned lower energy counterpart. Since 2012 we have been carrying out an optical spectroscopic campaign to observe blazar candidates to confirm their nature. In this paper, the sixth of the series, we present optical spectroscopic observations for 30 $\\gamma$-ray blazar candidates from different observing programs we carried out with the TNG, WHT, OAN, SOAR and Magellan telescopes. We found that 21 out of 30 sour...

  20. The Outburst of the Blazar S40954+658 in March-April 2011

    CERN Document Server

    Morozova, D A; Troitsky, I S; Jorstad, S G; Marscher, A P; Gómez, J L; Blinov, D A; Efimova, N V; Hagen-Thorn, V A; Hagen-Thorn, E I; Joshi, M; Konstantinova, T S; Kopatskaya, E N; Larionova, L V; Larionova, E G; Lähteenmäki, A; Tammi, J; Rastorgueva-Foi, E; McHardy, I; Tornikoski, M; Agudo, I; Casadio, C; Molina, S N; Volvach, A E; Volvach, L N

    2014-01-01

    We present the results of optical (R band) photometric and polarimetric monitoring and Very Long Baseline Array (VLBA) imaging of the blazar S4 0954+658, along with Fermi and gamma;-ray data during a multi-waveband outburst in 2011 March-April. After a faint state with a brightness level R ~17.6 mag registered in the first half of January 2011, the optical brightness of the source started to rise and reached ~14.8 mag during the middle of March, showing flare-like behavior. The most spectacular case of intranight variability was observed during the night of 2011 March 9, when the blazar brightened by ~0.7 mag within ~7 hours. During the rise of the flux the position angle of optical polarization rotated smoothly over more than 300$\\deg$. At the same time, within 1$\\sigma$ uncertainty a new superluminal knot appeared with an apparent speed of 19.0$\\pm$0.3 c. We have very strong evidence for association of this knot with the multi-waveband outburst in 2011 March-April. We also analyze the multi-frequency behavi...

  1. Blazars in the Fermi Era: The OVRO 40-m Telescope Monitoring Program

    CERN Document Server

    Richards, Joseph L; Pavlidou, Vasiliki; King, Oliver G; Pearson, Timothy J; Readhead, Anthony C S; Reeves, Rodrigo; Shepherd, Martin C; Stevenson, Matthew A; Weintraub, Lawrence C; Fuhrmann, Lars; Angelakis, Emmanouil; Zensus, J Anton; Healey, Stephen E; Romani, Roger W; Shaw, Michael S; Grainge, Keith; Birkinshaw, Mark; Lancaster, Katy; Worrall, Diana M; Taylor, Gregory B; Cotter, Garret; Bustos, Ricardo

    2010-01-01

    The Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope provides an unprecedented opportunity to study gamma-ray blazars. To capitalize on this opportunity, beginning in late 2007, about a year before the start of LAT science operations, we began a large-scale, fast-cadence 15 GHz radio monitoring program with the 40-m telescope at the Owens Valley Radio Observatory (OVRO). This program began with the 1158 northern (declination>-20 deg) sources from the Candidate Gamma-ray Blazar Survey (CGRaBS) and now encompasses over 1500 sources, each observed twice per week with a ~4 mJy (minimum) and 3% (typical) uncertainty. Here, we describe this monitoring program and our methods, and present radio light curves from the first two years (2008 and 2009). As a first application, we combine these data with a novel measure of light curve variability amplitude, the intrinsic modulation index, through a likelihood analysis to examine the variability properties of subpopulations of our sample. We demonstrat...

  2. X-ray spectral studies of TeV gamma-ray emitting blazars

    CERN Document Server

    Wierzcholska, Alicja

    2016-01-01

    This work is a summary of the X-ray spectral studies of 29 TeV $\\gamma$-ray emitting blazars observed with Swift/XRT, especially focusing on sources for which X-ray regime allows to study the low and the high energy ends of the particle distributions function. Variability studies require simultaneous coverage, ideally sampling different flux states of each source. This is achieved using X-ray observations by disentangling the high-energy end of the synchrotron emission and the low-energy end of the Compton emission, which are produced by the same electron population. We focused on a sample of 29 TeV gamma-ray emitting blazars with the best signal-to-noise X-ray observations collected with Swift/XRT in the energy range of 0.3-10 keV during 10 years of Swift/XRT operations. We investigate the X-ray spectral shapes and the effects of different corrections for neutral hydrogen absorption and decompose the synchrotron and inverse Compton components. In the case of 5 sources (3C 66A, S5 0716+714, W Comae, 4C +21.35...

  3. The 72-Hour WEBT Microvariability Observation of Blazar S5 0716+714 in 2009

    CERN Document Server

    Bhatta, G; Hollingsworth, H; Dhalla, S; Khanuja, A; Bachev, R; Blinov, D A; Bottcher, M; Calle, O J A Bravo; Calcidese, P; Capezzali, D; Carosati, D; Chigladze, R; Collins, A; Coloma, J M; Efimov, Y; Gupta, A C; Hu, S-M; Kurtanidze, O; Lamerato, A; Larionov, V M; Lee, C -U; Lindfors, E; Murphy, B; Nilsson, K; Ohlert, J M; Oksanen, A; Paakkonen, P; Pollock, J T; Rani, B; Reinthal, R; Rodriguez, D; Ros, J A; Roustazadeh, P; Sagar, R; Sanchez, A; Shastri, P; Sillanpaa, A; Strigachev, A; Takalo, L; Vennes, S; Villata, M; Villforth, C; Wu, J; Zhou, X

    2013-01-01

    Context. The international whole earth blazar telescope (WEBT) consortium planned and carried out three days of intensive micro-variability observations of S5 0716+714 from February 22, 2009 to February 25, 2009. This object was chosen due to its bright apparent magnitude range, its high declination, and its very large duty cycle for micro-variations. Aims. We report here on the long continuous optical micro-variability light curve of 0716+714 obtained during the multi-site observing campaign during which the Blazar showed almost constant variability over a 0.5 magnitude range. The resulting light curve is presented here for the first time. Observations from participating observatories were corrected for instrumental diff?erences and combined to construct the overall smoothed light curve. Methods. Thirty-six observatories in sixteen countries participated in this continuous monitoring program and twenty of them submitted data for compilation into a continuous light curve. The light curve was analyzed using se...

  4. Search for neutrino emission of gamma-ray flaring blazars with the ANTARES telescope

    CERN Document Server

    Dornic, D

    2011-01-01

    The ANTARES telescope is well suited to detect neutrinos produced in astrophysical transient sources as it can observe a full hemisphere of the sky at all times with a high duty cycle. The background and point source sensitivity can be drastically reduced by selecting a narrow time window around the assumed neutrino production period. Radio-loud active galactic nuclei with their jets pointing almost directly towards the observer, the so- called blazars, are particularly attractive potential neutrino point sources, since they are among the most likely sources of the observed ultra high energy cosmic rays and therefore, neutrinos and gamma-rays may be produced in hadronic interactions with the surrounding medium. The gamma-ray light curves of blazars measured by the LAT instrument on-board the Fermi satellite reveal important time variability information. A strong correlation between the gamma-ray and the neutrino fluxes is expected in this scenario. An unbinned method based on the minimization of a likelihood ...

  5. SDSSJ14584479+3720215: A Benchmark JHK Blazar Light Curve from the 2MASS Calibration Scans

    CERN Document Server

    Davenport, James R A; Becker, Andrew C; Macleod, Chelsea L; Cutri, Roc M

    2015-01-01

    Active galactic nuclei (AGNs) are well-known to exhibit flux variability across a wide range of wavelength regimes, but the precise origin of the variability at different wavelengths remains unclear. To investigate the relatively unexplored near-IR variability of the most luminous AGNs, we conduct a search for variability using well sampled JHKs-band light curves from the 2MASS survey calibration fields. Our sample includes 27 known quasars with an average of 924 epochs of observation over three years, as well as one spectroscopically confirmed blazar (SDSSJ14584479+3720215) with 1972 epochs of data. This is the best-sampled NIR photometric blazar light curve to date, and it exhibits correlated, stochastic variability that we characterize with continuous auto-regressive moving average (CARMA) models. None of the other 26 known quasars had detectable variability in the 2MASS bands above the photometric uncertainty. A blind search of the 2MASS calibration field light curves for AGN candidates based on fitting C...

  6. Testing the Equivalence Principle and Lorentz Invariance with PeV Neutrinos from Blazar Flares.

    Science.gov (United States)

    Wang, Zi-Yi; Liu, Ruo-Yu; Wang, Xiang-Yu

    2016-04-15

    It was recently proposed that a giant flare of the blazar PKS B1424-418 at redshift z=1.522 is in association with a PeV-energy neutrino event detected by IceCube. Based on this association we here suggest that the flight time difference between the PeV neutrino and gamma-ray photons from blazar flares can be used to constrain the violations of equivalence principle and the Lorentz invariance for neutrinos. From the calculated Shapiro delay due to clusters or superclusters in the nearby universe, we find that violation of the equivalence principle for neutrinos and photons is constrained to an accuracy of at least 10^{-5}, which is 2 orders of magnitude tighter than the constraint placed by MeV neutrinos from supernova 1987A. Lorentz invariance violation (LIV) arises in various quantum-gravity theories, which predicts an energy-dependent velocity of propagation in vacuum for particles. We find that the association of the PeV neutrino with the gamma-ray outburst set limits on the energy scale of possible LIV to >0.01E_{pl} for linear LIV models and >6×10^{-8}E_{pl} for quadratic order LIV models, where E_{pl} is the Planck energy scale. These are the most stringent constraints on neutrino LIV for subluminal neutrinos. PMID:27127950

  7. Constraining the Location of Gamma-Ray Flares in Luminous Blazars

    CERN Document Server

    Nalewajko, Krzysztof; Sikora, Marek

    2014-01-01

    Locating the gamma-ray emission sites in blazar jets is a long-standing and highly controversial issue. We investigate jointly several constraints on the distance scale r and Lorentz factor Gamma of the gamma-ray emitting regions in luminous blazars (primarily flat spectrum radio quasars, FSRQs). Working in the framework of one-zone external radiation Comptonization (ERC) models, we perform a parameter space study for several representative cases of actual gamma-ray flares in their multiwavelength context. We find a particularly useful combination of three constraints: from an upper limit on the collimation parameter Gamma*theta ~ 0.1 - 0.7. Typical values of r corresponding to moderate values of Gamma ~ 20 are in the range 0.1 - 1 pc, and are determined primarily by the observed variability time scale t_var,obs. Alternative scenarios motivated by the observed gamma-ray/mm connection, in which gamma-ray flares of t_var,obs ~ a few days are located at r ~ 10 pc, are in conflict with both the SSC and cooling co...

  8. An Emerging Class of Gamma-Ray Flares from Blazars: Beyond One-Zone Models

    CERN Document Server

    Tavani, Marco; Cavaliere, Alfonso

    2015-01-01

    Blazars radiate from relativistic plasma jets with bulk Lorentz factors {\\Gamma} ~ 10, closely aligned along our line of sight. In a number of blazars of the Flat Spectrum Radio Quasar type such as 3C 454.3 and 3C 279 gamma-ray flares have recently been detected with very high luminosity and little or no counterparts in the optical and soft X-ray bands. They challenge the current one-zone leptonic models of emissions from within the broad line region. The latter envisage the optical/X-ray emissions to be produced as synchrotron radiation by the same population of highly relativistic electrons in the jet that would also yield the gamma rays by inverse Compton up-scattering of surrounding soft photons. To meet the challenge we present here a model based on primary synchrotron photons emitted in the broad line region by a plasmoid moving out with the jet and scattered back toward the incoming plasmoid by an outer plasma clump acting as a mirror. We consider both a scenario based on a static mirror located outsid...

  9. The Deep X-ray Radio Blazar Survey (DXRBS). II. New Identifications

    CERN Document Server

    Landt, H; Perlman, E S; Giommi, P; Bignall, H E; Tzioumis, A K

    2001-01-01

    We have searched the archived, pointed ROSAT Position Sensitive Proportional Counter data for blazars by correlating the WGACAT X-ray database with several publicly available radio catalogs, restricting our candidate list to serendipitous X-ray sources with a flat radio spectrum (alpha_r <= 0.70). This makes up the Deep X-ray Radio Blazar Survey (DXRBS). Here we present new identifications and spectra for 106 sources, including 86 radio-loud quasars, 11 BL Lacertae objects, and 9 narrow-line radio galaxies. Together with our previously published objects and already known sources, our sample now contains 298 identified objects: 234 radio-loud quasars (181 flat-spectrum quasars: FSRQ [alpha_r <= 0.50] and 53 steep-spectrum quasars: SSRQ), 36 BL Lacs, and 28 narrow-line radio galaxies. Redshift information is available for 96% of these. Thus our selection technique is ~ 90% efficient at finding radio-loud quasars and BL Lacs. Reaching 5 GHz radio fluxes ~ 50 mJy and 0.1-2.0 keV X-ray fluxes a few x 10^-14 ...

  10. RECOLLIMATION AND RADIATIVE FOCUSING OF RELATIVISTIC JETS: APPLICATIONS TO BLAZARS AND M87

    International Nuclear Information System (INIS)

    Recent observations of M87 and some blazars reveal violent activity in small regions located at relatively large distances from the central engine. Motivated by these considerations, we study the hydrodynamic collimation of a relativistic cooling outflow using a semianalytical model developed earlier. We first demonstrate that radiative cooling of the shocked outflow layer can lead to a focusing of the outflow and its reconfinement in a region having a very small cross-sectional radius. Such a configuration can produce rapid variability at large distances from the central engine via reflections of the converging recollimation shock. Possible applications of this model to TeV blazars are discussed. We then apply our model to M87. The low radiative efficiency of the M87 jet renders focusing unlikely. However, the shallow profile of the ambient medium pressure inferred from observations results in extremely good collimation that can explain the reported variability of the X-ray flux emitted from the HST-1 knot.

  11. Search for Neutrino Emission from Gamma-Ray Flaring Blazars with the ANTARES Telescope

    CERN Document Server

    Adrián-Martínez, S; Albert, A; André, M; Anghinolfi, M; Anton, G; Anvar, S; Ardid, M; Astraatmadja, T; Aubert, J-J; Baret, B; Basa, S; Bertin, V; Biagi, S; Bigongiari, C; Bogazzi, C; Bou-Cabo, M; Bouhou, B; Bouwhuis, M C; Brunner, J; Busto, J; Camarena, F; Capone, A; Cârloganu, C; Carminati, G; Carr, J; Cecchini, S; Charif, Z; Charvis, Ph; Chiarusi, T; Circella, M; Core, L; Costantini, H; Coyle, P; Creusot, A; Curtil, C; De Bonis, G; Decowski, M P; Dekeyser, I; Deschamps, A; Distefano, C; Donzaud, C; Dornic, D; Dorosti, Q; Drouhin, D; Eberl, T; Emanuele, U; Enzenhöfer, A; Ernenwein, J-P; Escoffier, S; Fehn, K; Fermani, P; Ferri, M; Ferry, S; Flaminio, V; Folger, F; Fritsch, U; Fuda, J-L; Galatà, S; Gay, P; Geyer, K; Giacomelli, G; Giordano, V; Gómez-González, J P; Graf, K; Guillard, G; Halladjian, G; Hallewell, G; van Haren, H; Hartman, J; Heijboer, A J; Hello, Y; Hernández-Rey, J J; Herold, B; Hößl, J; Hsu, C C; de Jong, M; Kadler, M; Kalekin, O; Kappes, A; Katz, U; Kavatsyuk, O; Kooijman, P; Kopper, C; Kouchner, A; Kreykenbohm, I; Kulikovskiy, V; Lahmann, R; Lambard, G; Larosa, G; Lattuada, D; Lefèvre, D; Lim, G; Presti, D Lo; Loehner, H; Loucatos, S; Louis, F; Mangano, S; Marcelin, M; Margiotta, A; Martínez-Mora, J A; Meli, A; Montaruli, T; Morganti, N; Moscoso, L; Motz, H; Neff, M; Nezri, E; Palioselitis, D; Păvălaş, G E; Payet, K; Payre, P; Petrovic, J; Piattelli, P; Picot-Clemente, N; Popa, V; Pradier, T; Presani, E; Racca, C; Reed, C; Riccobene, G; Richardt, C; Richter, R; Rivière, C; Robert, A; Roensch, K; Rostovtsev, A; Ruiz-Rivas, J; Rujoiu, M; Russo, G V; Salesa, F; Samtleben, D F E; Sapienza, P; Schöck, F; Schuller, J-P; Schüssler, F; Seitz, T; Shanidze, R; Simeone, F; Spies, A; Spurio, M; Steijger, J M; Stolarczyk, Th; Sánchez-Losa, A; Taiuti, M; Tamburini, C; Toscano, S; Vallage, B; Vallée, C; Van Elewyck, V; Vannoni, G; Vecchi, M; Vernin, P; Visser, E; Wagner, S; Wijnker, G; Wilms, J; de Wolf, E; Yepes, H; Zaborov, D; Zornoza, J D; Zúñiga, J

    2011-01-01

    The ANTARES telescope is well-suited to detect neutrinos produced in astrophysical transient sources as it can observe a full hemisphere of the sky at all times with a high duty cycle. Radio-loud active galactic nuclei with jets pointing almost directly towards the observer, the so-called blazars, are particularly attractive potential neutrino point sources. The all-sky monitor LAT on board the Fermi satellite probes the variability of any given gamma-ray bright blazar in the sky on time scales of hours to months. Assuming hadronic models, a strong correlation between the gamma-ray and the neutrino fluxes is expected. Selecting a narrow time window on the assumed neutrino production period can significantly reduce the background. An unbinned method based on the minimization of a likelihood ratio was applied to a subsample of data collected in 2008 (61 days live time). By searching for neutrinos during the high state periods of the AGN light curve, the sensitivity to these sources was improved by about a facto...

  12. Time-Dependent Electron Acceleration in Blazar Transients: X-Ray Time Lags and Spectral Formation

    CERN Document Server

    Lewis, Tiffany R; Finke, Justin D

    2016-01-01

    Electromagnetic radiation from blazar jets often displays strong variability, extending from radio to $\\gamma$-ray frequencies. In a few cases, this variability has been characterized using Fourier time lags, such as those detected in the X-rays from Mrk~421 using BeppoSAX. The lack of a theoretical framework to interpret the data has motivated us to develop a new model for the formation of the X-ray spectrum and the time lags in blazar jets based on a transport equation including terms describing stochastic Fermi acceleration, synchrotron losses, shock acceleration, adiabatic expansion, and spatial diffusion. We derive the exact solution for the Fourier transform of the electron distribution, and use it to compute the Fourier transform of the synchrotron radiation spectrum and the associated X-ray time lags. The same theoretical framework is also used to compute the peak flare X-ray spectrum, assuming that a steady-state electron distribution is achieved during the peak of the flare. The model parameters are...

  13. Discovery of a GeV Blazar Shining Through the Galactic Plane

    Energy Technology Data Exchange (ETDEWEB)

    Vandenbroucke, J.; Buehler, R.; Ajello, M.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Bellini, A.; /Padua U., Astron. Dept. /Baltimore, Space Telescope Sci.; Bolte, M.; /UC, Santa Cruz; Cheung, C.C.; /Naval Research Lab, Wash., D.C. /NAS, Washington, D.C.; Civano, F.; /Smithsonian Astrophys. Observ.; Donato, D.; /NASA, Goddard; Fuhrmann, L.; /Bonn, Max Planck Inst., Radioastron.; Funk, S.; Healey, S.E.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Hill, A.B.; /Joseph Fourier U.; Knigge, C.; /Southampton U.; Madejski, G.M.; Romani, R.W.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Santander-Garcia, M.; /IAC, La Laguna /Isaac Newton Group /Laguna U., Tenerife; Shaw, M.S.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Steeghs, D.; /Warwick U.; Torres, M.A.P.; /Smithsonian Astrophys. Observ.; Van Etten, A.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Texas U., Astron. Dept.

    2011-08-11

    The Fermi Large Area Telescope (LAT) discovered a new gamma-ray source near the Galactic plane, Fermi J0109+6134, when it flared brightly in 2010 February. The low Galactic latitude (b = -1.2{sup o}) indicated that the source could be located within the Galaxy, which motivated rapid multi-wavelength follow-up including radio, optical, and X-ray observations. We report the results of analyzing all 19 months of LAT data for the source, and of X-ray observations with both Swift and the Chandra X-ray Observatory. We determined the source redshift, z = 0.783, using a Keck LRIS observation. Finally, we compiled a broadband spectral energy distribution (SED) from both historical and new observations contemporaneous with the 2010 February flare. The redshift, SED, optical line width, X-ray obsorption, and multi-band variability indicate that this new Gev source is a blazar seen through the Galactic plane. Because several of the optical emission lines have equivalent width > 5 {angstrom}, this blazar belongs in the flat-spectrum radio quasar category.

  14. RoboPol: optical polarization-plane rotations and flaring activity in blazars

    Science.gov (United States)

    Blinov, D.; Pavlidou, V.; Papadakis, I. E.; Hovatta, T.; Pearson, T. J.; Liodakis, I.; Panopoulou, G. V.; Angelakis, E.; Baloković, M.; Das, H.; Khodade, P.; Kiehlmann, S.; King, O. G.; Kus, A.; Kylafis, N.; Mahabal, A.; Marecki, A.; Modi, D.; Myserlis, I.; Paleologou, E.; Papamastorakis, I.; Pazderska, B.; Pazderski, E.; Rajarshi, C.; Ramaprakash, A.; Readhead, A. C. S.; Reig, P.; Tassis, K.; Zensus, J. A.

    2016-04-01

    We present measurements of rotations of the optical polarization of blazars during the second year of operation of RoboPol, a monitoring programme of an unbiased sample of gamma-ray bright blazars specially designed for effective detection of such events, and we analyse the large set of rotation events discovered in two years of observation. We investigate patterns of variability in the polarization parameters and total flux density during the rotation events and compare them to the behaviour in a non-rotating state. We have searched for possible correlations between average parameters of the polarization-plane rotations and average parameters of polarization, with the following results: (1) there is no statistical association of the rotations with contemporaneous optical flares; (2) the average fractional polarization during the rotations tends to be lower than that in a non-rotating state; (3) the average fractional polarization during rotations is correlated with the rotation rate of the polarization plane in the jet rest frame; (4) it is likely that distributions of amplitudes and durations of the rotations have physical upper bounds, so arbitrarily long rotations are not realized in nature.

  15. Anatomy of a blazar in the (sub-)millimeter: ALMA Observations of PKS 0521-365

    CERN Document Server

    Leon, S; Guerard, M; Villard, E; Hidayat, T; Flaquer, B Ocana; Vila-Vilaro, B

    2015-01-01

    We aim at analyzing the (sub-)millimeter emission in a nearby blazar, PKS 0521-365 , to study the synchrotron and thermal emission in the different components detected at low frequency. We analyze the archive public data of the ALMA Cycle 0 where PKS 0521-365 is used as a calibrator. A total of 13 projects with 23 dataset is analyzed in band 3, 6 and 7 and combined. The whole set of data is combined and wavelet filtered to obtain a deep image reaching a dynamic range of 47000. The individual emission flux is measured at different date over a period of 11 months in various components. Finally we analyze the Spectral Energy Distribution (SED) in each different component, including the radio jet and counter jet. The point sources detected in the field follow a similar distribution to previous studies. The blazar flux shows large variation especially in band 3. Different components are observed: core, radio jet and newly detected counter jet, Hot Spot (HS) and a disky structure roughly perpendicular to the jet. T...

  16. Deep Broadband Observations of the Distant Gamma-ray Blazar PKS 1424+240

    CERN Document Server

    Archambault, S; Behera, B; Beilicke, M; Benbow, W; Berger, K; Bird, R; Biteau, J; Bugaev, V; Byrum, K; Cardenzana, J V; Cerruti, M; Chen, X; Ciupik, L; Connolly, M P; Cui, W; Dumm, J; Errando, M; Falcone, A; Federici, S; Feng, Q; Finley, J P; Fleischhack, H; Fortson, L; Furniss, A; Galante, N; Gillanders, G H; Griffin, S; Griffiths, S T; Grube, J; Gyuk, G; Hanna, D; Holder, J; Hughes, G; Humensky, T B; Johnson, C A; Kaaret, P; Kertzman, M; Khassen, Y; Kieda, D; Krawczynski, H; Krennrich, F; Kumar, S; Lang, M J; Madhavan, A S; Maier, G; McCann, A; Meagher, K; Moriarty, P; Mukherjee, R; Nieto, D; de Bhroithe, A O'Faolain; Ong, R A; Otte, A N; Park, N; Pohl, M; Popkow, A; Prokoph, H; Quinn, J; Ragan, K; Rajotte, J; Reyes, L C; Reynolds, P T; Richards, G T; Roache, E; Sembroski, G H; Shahinyan, K; Staszak, D; Telezhinsky, I; Tucci, J V; Tyler, J; Varlotta, A; Vassiliev, V V; Vincent, S; Wakely, S P; Weinstein, A; Welsing, R; Wilhelm, A; Williams, D A; Ackermann, M; Ajello, M; Albert, A; Baldini, L; Bastieri, D; Bellazzini, R; Bissaldi, E; Bregeon, J; Buehler, R; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Cavazzuti, E; Charles, E; Chiang, J; Ciprini, S; Claus, R; Cutini, S; D'Ammando, F; de Angelis, A; de Palma, F; Dermer, C D; Digel, S W; Di Venere, L; Drell, P S; Favuzzi, C; Franckowiak, A; Fusco, P; Gargano, F; Gasparrini, D; Giglietto, N; Giordano, F; Giroletti, M; Grenier, I A; Guiriec, S; Jogler, T; Kuss, M; Larsson, S; Latronico, L; Longo, F; Loparco, F; Lubrano, P; Madejski, G M; Mayer, M; Mazziotta, M N; Michelson, P F; Mizuno, T; Monzani, M E; Morselli, A; Murgia, S; Nuss, E; Ohsugi, T; Ormes, J F; Perkins, J S; Piron, F; Pivato, G; Raino, S; Razzano, M; Reimer, A; Reimer, O; Ritz, S; Schaal, M; Sgro, C; Siskind, E J; Spinelli, P; Takahashi, H; Tibaldo, L; Tinivella, M; Troja, E; Vianello, G; Werner, M; Wood, M

    2014-01-01

    We present deep VERITAS observations of the blazar PKS 1424+240, along with contemporaneous Fermi Large Area Telescope, Swift X-ray Telescope and Swift UV Optical Telescope data between 2009 February 19 and 2013 June 8. This blazar resides at a redshift of $z\\ge0.6035$, displaying a significantly attenuated gamma-ray flux above 100 GeV due to photon absorption via pair-production with the extragalactic background light. We present more than 100 hours of VERITAS observations from three years, a multiwavelength light curve and the contemporaneous spectral energy distributions. The source shows a higher flux of (2.1$\\pm0.3$)$\\times10^{-7}$ ph m$^{-2}$s$^{-1}$ above 120 GeV in 2009 and 2011 as compared to the flux measured in 2013, corresponding to (1.02$\\pm0.08$)$\\times10^{-7}$ ph m$^{-2}$s$^{-1}$ above 120 GeV. The measured differential very high energy (VHE; $E\\ge100$ GeV) spectral indices are $\\Gamma=$3.8$\\pm$0.3, 4.3$\\pm$0.6 and 4.5$\\pm$0.2 in 2009, 2011 and 2013, respectively. No significant spectral change...

  17. Reconciling models of luminous blazars with magnetic fluxes determined by radio core shift measurements

    CERN Document Server

    Nalewajko, Krzysztof; Begelman, Mitchell C

    2014-01-01

    Estimates of magnetic field strength in relativistic jets of active galactic nuclei (AGN), obtained by measuring the frequency-dependent radio core location, imply that the total magnetic fluxes in those jets are consistent with the predictions of the magnetically-arrested disk (MAD) scenario of jet formation. On the other hand, the magnetic field strength determines the luminosity of the synchrotron radiation, which forms the low-energy bump of the observed blazar spectral energy distribution (SED). The SEDs of the most powerful blazars are strongly dominated by the high-energy bump, which is most likely due to the external radiation Compton (ERC) mechanism. This high Compton dominance may be difficult to reconcile with the MAD scenario, unless 1) the geometry of external radiation sources (broad-line region, hot-dust torus) is quasi-spherical rather than flat, or 2) most gamma-ray radiation is produced in jet regions of low magnetization, e.g., in magnetic reconnection layers or in fast jet spines.

  18. Synchrotron Lightcurves of blazars in a time-dependent synchrotron-self Compton cooling scenario

    CERN Document Server

    Zacharias, Michael

    2013-01-01

    Blazars emit non-thermal radiation in all frequency bands from radio to \\gamma-rays. Additionally, they often exhibit rapid flaring events at all frequencies with doubling time scale of the TeV and X-ray flux on the order of minutes, and such rapid flaring events are hard to explain theoretically. We explore the effect of the synchrotron-self Compton cooling, which is inherently time-dependent, leading to a rapid cooling of the electrons. Having discussed intensively the resulting effects of this cooling scenario on the spectral energy distribution of blazars in previous papers, the effects of the time-dependent approach on the synchrotron lightcurve are investigated here. Taking into account the retardation due to the finite size of the source and the source geometry, we show that the time-dependent synchrotron-self Compton (SSC) cooling still has profound effects on the lightcurve compared to the usual linear (synchrotron and external Compton) cooling terms. This is most obvious if the SSC cooling takes lon...

  19. Turbulent, Extreme Multi-Zone Model for Simulating Flux and Polarization Variability in Blazars

    CERN Document Server

    Marscher, Alan P

    2013-01-01

    The author presents a model for variability of the flux and polarization of blazars in which turbulent plasma flowing at a relativistic speed down a jet crosses a standing conical shock. The shock compresses the plasma and accelerates electrons to energies up to gamma(max) > 1E4 times their rest-mass energy, with the value of gamma(max) determined by the direction of the magnetic field relative to the shock front. The turbulence is approximated in a computer code as many cells, each with a uniform magnetic field whose direction is selected randomly. The density of high-energy electrons in the plasma changes randomly with time in a manner consistent with the power spectral density of flux variations derived from observations of blazars. The variations in flux and polarization are therefore caused by continuous noise processes rather than by singular events such as explosive injection of energy at the base of the jet. Sample simulations illustrate the behavior of flux and linear polarization versus time that su...

  20. Why Haven't Many of the Brightest Radio Loud Blazars Been Detected by Fermi ?

    CERN Document Server

    Lister, M L; Max-Morbeck, W; Readhead, A C S; Richards, J L; Ros, E

    2015-01-01

    We use the complete MOJAVE 1.5 Jy sample of active galactic nuclei (AGN) to examine the gamma-ray detection statistics of the brightest radio-loud blazars in the northern sky. We find that 23% of these AGN were not detected above 0.1 GeV by the Fermi LAT during the 4-year 3FGL catalog period partly because of an instrumental selection effect, and partly due to their lower Doppler boosting factors. Blazars with synchrotron peaks in their spectral energy distributions located below $10^{13.4}$ Hz also tend to have high-energy peaks that lie below the 0.1 GeV threshold of the LAT, and are thus less likely to be detected by Fermi. The non-detected AGN in the 1.5 Jy sample also have significantly lower 15 GHz radio modulation indices and apparent jet speeds, indicating that they have lower than average Doppler factors. Since the effective amount of relativistic Doppler boosting is enhanced in gamma-rays (particularly in the case of external inverse-Compton scattering), this makes them less likely to appear in the ...

  1. VizieR Online Data Catalog: Non-Fermi blazar sample (Xiong+, 2015)

    Science.gov (United States)

    Xiong, D.; Zhang, X.; Bai, J.; Zhang, H.

    2015-11-01

    The selection criteria for the sample were that we tried to select the largest group of blazars included in the multi-frequency catalogue of blazars (the Roma BZCAT; Massaro et al.. 2009, Cat. J/A+A/495/691) with reliable broad-line luminosity (used as a proxy for disc luminosity), redshift, black hole mass and jet kinetic power. The sample of FBs was directly from Xiong & Zhang (2014MNRAS.441.3375X). The νpeak and Lpeak of our FBs were collected from Finke (2013ApJ...763..134F) and Meyer et al. (2011, Cat. J/ApJ/740/98), and the νpeak and Lpeak of NFBs from Nieppola et al. (2006, Cat. J/A+A/445/441; 2008, Cat. J/A+A/488/867), Meyer et al. (2011, Cat. J/ApJ/740/98), Wu, Gu & Jiang (2009RAA.....9..168W) and Aatrokoski et al. (2011A&A...536A..15P). (1 data file).

  2. Radio monitoring of a sample of X- and gamma-ray loud blazars

    CERN Document Server

    Venturi, T; Orfei, A; Bondi, M; Fanti, R; Gregorini, L; Mantovani, F; Stanghellini, C; Trigilio, C; Umana, G

    2001-01-01

    In this paper we present the results of a 4-year (1996 - 1999) radio flux density monitoring program for a sample of X- and $\\gamma$-ray loud blazars. Our program started in January 1996 and was carried out on monthly basis at the frequencies of 5 GHz and 8.4 GHz with the 32-m antennas located in Medicina (Bologna, Italy) and Noto (Siracusa, Italy). 22 GHz data collected in Medicina from January 1996 to June 1997 will also be presented. The sample of selected sources comprises most radio loud blazars with $\\delta \\ge -10^{\\circ}$ characterised by emission in the X- and $\\gamma$-ray regimes, and target sources for the BeppoSAX X-ray mission. All sources in the sample, except J1653+397 (MKN 501), are variable during the four years of our monitoring program. We classified the type of variability in each source by means of a structure function analysis. We also computed th$\\alpha_{5}^{8.4}$ for all epochs with nearly simultaneous observations ate spectral index and found that $\\alpha_{5}^{8.4}$ starts flattening ...

  3. Radiation and Polarization Signatures of 3D Multi-zone Time-dependent Hadronic Blazar Model

    CERN Document Server

    Zhang, Haocheng; Böttcher, Markus

    2016-01-01

    We present a newly developed time-dependent three-dimensional multi-zone hadronic blazar emission model. By coupling a Fokker-Planck based lepto-hadronic particle evolution code 3DHad with a polarization-dependent radiation transfer code, 3DPol, we are able to study the time-dependent radiation and polarization signatures of a hadronic blazar model for the first time. Our current code is limited to parameter regimes in which the hadronic $\\gamma$-ray output is dominated by proton synchrotron emission, neglecting pion production. Our results demonstrate that the time-dependent flux and polarization signatures are generally dominated by the relation between the synchrotron cooling and the light crossing time scale, which is largely independent of the exact model parameters. We find that unlike the low-energy polarization signatures, which can vary rapidly in time, the high-energy polarization signatures appear stable. As a result, future high-energy polarimeters may be able to distinguish such signatures from t...

  4. Time-Dependent Modeling of Gamma-ray Flares in Blazar PKS1510-089

    CERN Document Server

    Saito, Shinya; Tanaka, Yasuyuki; Takahashi, Tadayuki; Sikora, Marek; Moderski, Rafal

    2015-01-01

    Here we present a new approach for constraining luminous blazars, incorporating fully time-dependent and self-consistent modeling of bright gamma-ray flares of PKS1510-089 resolved with Fermi-LAT, in the framework of the internal shock scenario. The results of our modeling imply the location of the gamma-ray flaring zone outside of the broad-line region, namely around 0.3pc from the core for a free-expanding jet with the opening angle Gamma, \\theta_\\mathrm{jet} \\simeq 1 (where Gamma is the jet bulk Lorentz factor), up to \\simeq 3pc for a collimated outflow with Gamma, \\theta_\\mathrm{jet} \\simeq 0.1. Moreover, under the Gamma, \\theta_\\mathrm{jet} \\simeq 1 condition, our modeling indicates the maximum efficiency of the jet production during the flares, with the total jet energy flux strongly dominated by protons and exceeding the available accretion power in the source. This is in contrast to the quiescence states of the blazar, characterized by lower jet kinetic power and an approximate energy equipartition be...

  5. A narrow line Seyfert 1--blazar composite nucleus in 2MASX J0324+3410

    CERN Document Server

    Zhou, H; Yuan, W; Shan, H; Komossa, S; Lü, H; Liu, Y; Xu, D; Bai, J M; Jiang, D R; Zhou, Hongyan; Wang, Tinggui; Yuan, Weimin; Shan, Hongguang; Komossa, Stefanie; Lu, Honglin; Liu, Yi; Xu, Dawei

    2007-01-01

    We report the identification of 2MASX J032441.19+341045.9 (hereafter 2MASX J0324+3410) with an appealing object which shows the dual properties of both a narrow line Seyfert 1 galaxy (NLS1) and a blazar. Its optical spectrum, which has a H\\beta line width about 1600 km s^-1 (FWHM), an [OIII] to H\\beta line ratio ~0.12, and strong FeII emission, clearly fulfills the conventional definition of NLS1s. On the other hand, 2MASX J0324+3410 also exhibits some behavior which is characteristic of blazars, including a flat radio spectrum above 1 GHz, a compact core plus a one-sided jet structure on mas-scale at 8.4 GHz, highly variable fluxes in the radio, optical, and X-ray bands, and a possible detection of TeV gamma-ray emission. On its optical image, obtained with the HST WFPC2, the active nucleus is displaced from the center of the host galaxy, which exhibits an apparent one-armed spiral structure extended to 16 kpc. The remarkable hybrid behavior of this object presents a challenge to current models of NLS1 galax...

  6. The “Far Site” Scenario for Gamma-ray Emission in Blazars

    Directory of Open Access Journals (Sweden)

    Agudo Iván

    2013-12-01

    Full Text Available Since the birth of γ-ray astronomy, locating the origin of γ-ray emission has been a fundamental problem for the knowledge of the emission processes involved. Densely time sampled monitoring programs with very long baseline interferometry and the Fermi Gamma-ray Space Telescope, together with several other facilities at most of the available spectral ranges (including polarization measurements if possible are starting to shed new light for the case of blazars. A successful observing technique consists on analyzing the timing of multi-waveband variations in the flux and linear polarization, as well as changes in ultra-high resolution VLBI images to associate the particularly bright events at different wavebands. Such association can be robustly demonstrated by probing the statistical significance of the correlation among spectral ranges through Monte Carlo simulations. The location of the high energy emission region is inferred through its relative location with regard to the associated low energy event observed in the VLBI images. In this paper, I present some of the latest results using this method that locate the GeV emission within the jets of blazars AO 0235+164 and OJ287 at > 12 pc from the central AGN engine, hence supporting the “far site” scenario.

  7. OPTICAL SPECTROSCOPIC OBSERVATIONS OF GAMMA-RAY BLAZAR CANDIDATES. VI. FURTHER OBSERVATIONS FROM TNG, WHT, OAN, SOAR, AND MAGELLAN TELESCOPES

    Energy Technology Data Exchange (ETDEWEB)

    Álvarez Crespo, N.; Massaro, F. [Dipartimento di Fisica, Università degli Studi di Torino, via Pietro Giuria 1, I-10125 Torino (Italy); Milisavljevic, D.; Paggi, A.; Smith, Howard A. [Harvard—Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Landoni, M. [INAF-Osservatorio Astronomico di Brera, Via Emilio Bianchi 46, I-23807 Merate (Italy); Chavushyan, V.; Patiño-Álvarez, V. [Instituto Nacional de Astrofísica, Óptica y Electrónica, Apartado Postal 51-216, 72000 Puebla, México (Mexico); Masetti, N. [INAF—Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, via Gobetti 101, I-40129, Bologna (Italy); Jiménez-Bailón, E. [Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 877, Ensenada, 22800 Baja California, México (Mexico); Strader, J.; Chomiuk, L. [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Katagiri, H.; Kagaya, M. [College of Science, Ibaraki University, 2-1-1, Bunkyo, Mito 310-8512 (Japan); Cheung, C. C. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); D’Abrusco, R. [Department of Physical Sciences, University of Napoli Federico II, via Cinthia 9, I-80126 Napoli (Italy); Ricci, F.; La Franca, F. [Dipartimento di Matematica e Fisica, Università Roma Tre, via della Vasca Navale 84, I-00146, Roma (Italy); and others

    2016-04-15

    Blazars, one of the most extreme classes of active galaxies, constitute so far the largest known population of γ-ray sources, and their number is continuously growing in the Fermi catalogs. However, in the latest release of the Fermi catalog there is still a large fraction of sources that are classified as blazar candidates of uncertain type (BCUs) for which optical spectroscopic observations are necessary to confirm their nature and their associations. In addition, about one-third of the γ-ray point sources listed in the Third Fermi-LAT Source Catalog (3FGL) are still unassociated and lacking an assigned lower-energy counterpart. Since 2012 we have been carrying out an optical spectroscopic campaign to observe blazar candidates to confirm their nature. In this paper, the sixth of the series, we present optical spectroscopic observations for 30 γ-ray blazar candidates from different observing programs we carried out with the Telescopio Nazionale Galileo, William Herschel Telescope, Observatorio Astronómico Nacional, Southern Astrophysical Research Telescope, and Magellan Telescopes. We found that 21 out of 30 sources investigated are BL Lac objects, while the remaining targets are classified as flat-spectrum radio quasars showing the typical broad emission lines of normal quasi-stellar objects. We conclude that our selection of γ-ray blazar candidates based on their multifrequency properties continues to be a successful way to discover potential low-energy counterparts of the Fermi unidentified gamma-ray sources and to confirm the nature of BCUs.

  8. Through The Ring Of Fire: $\\gamma$-Ray Variability In Blazars By A Moving Plasmoid Passing A Local Source Of Seed Photons

    CERN Document Server

    MacDonald, Nicholas R; Jorstad, Svetlana G; Joshi, Manasvita

    2015-01-01

    Blazars exhibit flares across the electromagnetic spectrum. Many $\\gamma$-ray flares are highly correlated with flares detected at optical wavelengths; however, a small subset appears to occur in isolation, with little or no variability detected at longer wavelengths. These "orphan" $\\gamma$-ray flares challenge current models of blazar variability, most of which are unable to reproduce this type of behavior. We present numerical calculations of the time-variable emission of a blazar based on a proposal by Marscher et al. (2010) to explain such events. In this model, a plasmoid ("blob") propagates relativistically along the spine of a blazar jet and passes through a synchrotron-emitting ring of electrons representing a shocked portion of the jet sheath. This ring supplies a source of seed photons that are inverse-Compton scattered by the electrons in the moving blob. The model includes the effects of radiative cooling, a spatially varying magnetic field, and acceleration of the blob's bulk velocity. Synthetic...

  9. NuSTAR and multifrequency study of the two high-redshift blazars S5 0836+710 and PKS 2149-306

    DEFF Research Database (Denmark)

    Tagliaferri, G.; Ghisellini, G.; Perri, M.;

    2015-01-01

    Powerful blazars are flat-spectrum radio quasars whose emission is dominated by a Compton component peakingbetween a few hundred keV and a few hundred MeV. We observed two bright blazars, PKS 2149–306 at redshift z = 2.345 and S5 0836+710 at z = 2.172, in the hard X-ray band with the Nuclear...

  10. Model fitting of the kinematics of ten superluminal components in blazar 3C 279

    Institute of Scientific and Technical Information of China (English)

    Shan-Jie Qian

    2013-01-01

    The kinematics of ten superluminal components (C11-C16,C18,C20,C21 and C24) of blazar 3C 279 are studied from VLBI observations.It is shown that their initial trajectory,distance from the core and apparent speed can be well fitted by the precession model proposed by Qian.Combined with the results of the model fit for the six superluminal components (C3,C4,C7a,C8,C9 and C10) already published,the kinematics of sixteen superluminal components can now be consistently interpreted in the precession scenario with their ejection times spanning more than 25 yr (or more than one precession period).The results from model fitting show the possible existence of a common precessing trajectory for these knots within a projected core distance of ~0.2-0.4 mas.In the framework of the jet-precession scenario,we can,for the first time,identify three classes of trajectories which are characterized by their collimation parameters.These different trajectories could be related to the helical structure of magnetic fields in the jet.Through fitting the model,the bulk Lorentz factor,Doppler factor and viewing angle of these knots are derived.It is found that there is no evidence for any correlation between the bulk Lorentz factor of the components and their precession phase (or ejection time).In a companion paper,the kinematics of another seven components (C5a,C6,C7,C17,C19,C22 and C23) have been derived from model fitting,and a binary black-hole/jet scenario was envisaged.The precession model proposed by Qian would be useful for understanding the kinematics of superluminal components in blazar 3C 279 derived from VLBI observations,by disentangling different mechanisms and ingredients.More generally,it might also be helpful for studying the mechanism of jet swing (wobbling) in other blazars.

  11. Fermi-LAT View of Bright Flaring Gamma-Ray Blazars

    Indian Academy of Sciences (India)

    D. Bastieri; S. Ciprini; D. Gasparrini

    2011-03-01

    The Fermi LAT provides a continuous and uniform monitoring of the Universe in the gamma-ray band. During the first year many gamma-ray blazar flares, some unidentified transients and emission by the Sun while in a quiet state were promptly detected. This is mainly due to the design of the mission, featuring a detector, the LAT with a wide field of view, and to the operation of the spacecraft itself, that can cover every region of the sky every 3 hours. Nevertheless, the scientific exploitation of this monitoring is more fruitful when early information about transients reaches a broader community. In this respect, the indefatigable activity of flare advocates, who worked on weekly shifts to validate the results and quickly broadcast information about flares and new detections, was the key to most scientific results.

  12. Estudio de variabilidad del blazar BL Lacertae: desde radio hasta rayos gamma (2008-2015)

    Science.gov (United States)

    Pichel, A.; Rovero, A. C.

    2016-08-01

    The aim of this work is to study the blazar BL Lacertae during extended periods (greater than weeks), by characterizing the changes in flux and polarization at optical, radio, X-rays and gamma rays; also to investigate the possible correlations between different bands. We look for periodicity in the flux variations in different bands, looking for criteria to predict high activity states of the source. We use multi-frequency observations of BL Lacertae obtained during the years 2008--2015, from radio to very-high-energy gamma rays. During this period, the source remained mainly in a low state of activity at the high energy bands, with several episodes of high activity (flares) in different bands, some of them observed simultaneously in several bands.

  13. The Imprint of The Extragalactic Background Light in the Gamma-Ray Spectra of Blazars

    CERN Document Server

    ,

    2012-01-01

    The light emitted by stars and accreting compact objects through the history of the Universe is encoded in the intensity of the extragalactic background light (EBL). Knowledge of the EBL is important to understand the nature of star formation and galaxy evolution, but direct measurements of the EBL are lim- ited by Galactic and other foreground emissions. Here we report an absorption feature seen in the combined spectra of a sample of gamma-ray blazars out to a redshift of z$\\sim$1.6. This feature is caused by attenuation of gamma rays by the EBL at optical to UV frequencies, and allowed us to measure the EBL flux density in this frequency band.

  14. The beaming effect and $\\rm{\\gamma}$-ray emission for Fermi blazars

    CERN Document Server

    Chen, Yong-Yun; Xiong, Dingrong; Wang, Si-Ju; Yu, Xiaoling

    2015-01-01

    We study the $\\rm{\\gamma}$-ray luminosity and beaming effect for Fermi blazars. Our results are as follows. (i) There are significant correlations between $\\rm{\\gamma}$-ray luminosity and radio core luminosity, and between $\\rm{\\gamma}$-ray luminosity and $\\rm{R_{v}}$, which suggests that the $\\rm{\\gamma}$-ray emissions have strong beaming effect. (ii) Using the $\\rm{L_{ext}/M_{abs}}$ as an indicator of environment effects, we find that there have no significant correlation between $\\rm{\\gamma}$-ray luminosity and $\\rm{L_{ext}/M_{abs}}$ for all sources when remove the effect of redshift. FSRQs considered alone also do not show a significant correlation, while BL Lacs still show a significant correlation when remove the effect of redshift. These results suggest that the $\\rm{\\gamma}$-ray emission may be affected by environment on the kiloparsec-scale for BL Lacs.

  15. Broadband radio jet emission and variability of γ-ray blazars

    Science.gov (United States)

    Nestoras, Ioannis

    2015-07-01

    AGN (Active Galactic Nuclei) and in particular their subclass blazars, are among the most energetic objects observed in the universe, featuring extreme phenomenological characteristics such as rapid broadband flux density and polarization variability, fast super--luminal motion, high degree of polarization and a broadband, double-humped spectral energy distribution (SED). The details of the emission processes and violent variability of blazars are still poorly understood. Variability studies give important clues about the size, structure, physics and dynamics of the emitting region making AGN/blazar monitoring programs of uttermost importance in providing the necessary constraints for understanding the origin of energy production. In this framework the F-gamma program was initiated, monitoring monthly 60 fermi detected AGN/blazars at 12 frequencies between 2.6 and 345GHz since 2007. For the thesis in hand observations and data analysis were performed within the realms of the F-gamma program, using the Effelsberg (EB) 100m and Pico Veleta (PV) 30m telescopes at 10 frequency bands ranging from 2.64 to 142GHz. The cm to short-mm variability/spectral characteristics are monitored for a sample of 59 sources for a period of five years enabling for the first time a detailed study of the observed flaring activity in both the light curve and spectral domains for such a large number of sources and such high cadence. Also the observing systems and methods are introduced as well as the data reduction techniques. The thesis at hand is structured as follows: Chapter 3 presents the reduction methods and post measurement corrections applied to the data such as pointing offsets, gain--elevation and sensitivity corrections as well as specific corrections applied for each of the Effelsberg and Pico Veleta observing systems respectively. Chapter 4 presents the analysis tools and methods that were used such as: variability characteristics, flare amplitudes with a new method for

  16. Stochastic Gyroresonant Acceleration for Hard Electron Spectra of Blazars: Effect of Damping of Cascading Turbulence

    CERN Document Server

    Kakuwa, Jun

    2015-01-01

    Stochastic acceleration of nonthermal electrons is investigated in the context of hard photon spectra of blazars. It is well known that this acceleration mechanism can produce a hard electron spectrum of $m \\equiv \\partial \\ln n_{\\rm e}(\\gamma)/\\partial \\ln \\gamma = 2$ with the high-energy cutoff, called an ultrarelativistic Maxwellian-like distribution, where $n_{\\rm e}(\\gamma)$ is an electron energy spectrum. We revisit the formation of this characteristic spectrum, considering a particular situation where the electrons are accelerated through gyroresonant interaction with magnetohydrodynamic wave turbulence driven by the turbulent cascade. By solving kinetic equations of the turbulent fields, electrons, and photons emitted via the synchrotron self-Compton (SSC) process, we demonstrate that in the non-test-particle treatment, the formation of a Maxwellian-like distribution is prevented by the damping effect on the turbulent fields due to the electron acceleration, at least unless an extreme parameter value ...

  17. On the phenomenological classification of continuum radio spectra variability patterns of Fermi blazars

    CERN Document Server

    Angelakis, E; Nestoras, I; Fromm, C M; Schmidt, R; Zensus, J A; Marchili, N; Krichbaum, T P; Perucho-Pla, M; Ungerechts, H; Sievers, A; Riquelme, D

    2011-01-01

    The F-GAMMA program is a coordinated effort to investigate the physics of Active Galactic Nuclei (AGNs) via multi-frequency monitoring of {\\em Fermi} blazars. The current study is concerned with the broad-band radio spectra composed of measurement at ten frequencies between 2.64 and 142 GHz. It is shown that any of the 78 sources studied can be classified in terms of their variability characteristics in merely 5 types of variability. The first four types are dominated by spectral evolution and can be reproduced by a simple two-component system made of the quiescent spectrum of a large scale jet populated with a flaring event evolving according to Marscher & Gear (1985). The last type is characterized by an achromatic change of the broad-band spectrum which must be attributed to a completely different mechanism. Here are presented, the classification, the assumed physical system and the results of simulations that have been conducted.

  18. First Study of Combined Blazar Light Curves with FACT and HAWC

    CERN Document Server

    ,

    2016-01-01

    For studying variable sources like blazars, it is crucial to achieve unbiased monitoring, either with dedicated telescopes in pointing mode or survey instruments. At TeV energies, the High Altitude Water Cherenkov (HAWC) observatory monitors approximately two thirds of the sky every day. It uses the water Cherenkov technique, which provides an excellent duty cycle independent of weather and season. The First G-APD Cherenkov Telescope (FACT) monitors a small sample of sources with better sensitivity, using the imaging air Cherenkov technique. Thanks to its camera with silicon-based photosensors, FACT features an excellent detector performance and stability and extends its observations to times with strong moonlight, increasing the duty cycle compared to other imaging air Cherenkov telescopes. As FACT and HAWC have overlapping energy ranges, a joint study can exploit the longer daily coverage given that the observatories' locations are offset by 5.3 hours. Furthermore, the better sensitivity of FACT adds a fine...

  19. Helical motion and the origin of QPO in blazar-type sources

    CERN Document Server

    Rieger, F M

    2004-01-01

    Recent observations and analysis of blazar sources provide strong evidence for (i) the presence of significant periodicities in their lightcurves and (ii) the occurrence of helical trajectories in their radio jets. In scenarios, where the periodicity is caused by differential Doppler boosting effects along a helical jet path, both of these facts may be naturally tied together. Here we discuss four possible driving mechanisms for the occurrence of helical trajectories: orbital motion in a binary system, Newtonian-driven jet precession, internal jet rotation and motion along a global helical magnetic field. We point out that for non-ballistic helical motion the observed period may appear strongly shortened due to classical travel time effects. Finally, the possible relevance of the above mentioned driving mechanisms is discussed for Mkn~501, OJ 287 and AO 0235+16.

  20. Evidence for Quasi-periodic Modulation in the Gamma-ray Blazar PG 1553+113

    CERN Document Server

    Ackermann, M; Albert, A; Atwood, W B; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Gonzalez, J Becerra; Bellazzini, R; Bissaldi, E; Blandford, R D; Bloom, E D; Bonino, R; Bottacini, E; Bregeon, J; Bruel, P; Buehler, R; Buson, S; Caliandro, G A; Cameron, R A; Caputo, R; Caragiulo, M; Caraveo, P A; Cavazzuti, E; Cecchi, C; Chekhtman, A; Chiang, J; Chiaro, G; Ciprini, S; Cohen-Tanugi, J; Conrad, J; Cutini, S; D'Ammando, F; De Angelis, A; De Palma, F; Desiante, R; Di Venere, L; Dominguez, A; Drell, P S; Favuzzi, C; Fegan, S J; Ferrara, E C; Focke, W B; Fuhrmann, L; Fukazawa, Y; Fusco, P; Gargano, F; Gasparrini, D; Giglietto, N; Giommi, P; Giordano, F; Giroletti, M; Godfrey, G; Green, D; Grenier, I A; Grove, J E; Guiriec, S; Harding, A K; Hays, E; Hewitt, J W; Hill, A B; Horan, D; Jogler, T; Johannesson, G; Johnson, A S; Kamae, T; Kuss, M; Larsson, S; Latronico, L; Li, J; Li, L; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Magill, J; Maldera, S; Manfreda, A; Max-Moerbeck, W; Mayer, M; Mazziotta, M N; Mcenery, J E; Michelson, P F; Mizuno, T; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nuss, E; Ohno, M; Ohsugi, T; Ojha, R; Omodei, N; Orlando, E; Ormes, J F; Paneque, D; Pearson, T J; Perkins, J S; Perri, M; Pesce-Rollins, M; Petrosian, V; Piron, F; Pivato, G; Porter, T A; Raino', S; Rando, R; Razzano, M; Readhead, A; Reimer, A; Reimer, O; Schulz, A; Sgro', C; Siskind, E J; Spada, F; Spandre, G; Spinelli, P; Suson, D J; Takahashi, H; Thayer, J B; Thompson, D J; Tibaldo, L; Torres, D F; Tosti, G; Troja, E; Uchiyama, Y; Vianello, G; Wood, K S; Wood, M; Zimmer, S; Berdyugin, A; Corbet, R H D; Hovatta, T; Lindfors, E; Nilsson, K; Reinthal, R; Sillanpaa, A; Stamerra, A; Takalo, L O; Valtonen, M J

    2015-01-01

    We report for the first time a gamma-ray and multiwavelength nearly-periodic oscillation in an active galactic nucleus. Using the Fermi Large Area Telescope (LAT) we have discovered an apparent quasi-periodicity in the gamma-ray flux (E>100 MeV) from the GeV/TeV BL Lac object PG 1553+113. The marginal significance of the 2.18 +/- 0.08 year-period gamma-ray cycle, seen in 3.5 oscillation maxima observed, is corroborated by correlated oscillations observed in radio and optical fluxes, through data collected in the OVRO, Tuorla, KAIT, and CSS monitoring programs and Swift UVOT. The optical cycle appearing in sim 10 years of data has a similar period, while the 15 GHz oscillation is less regular. Further long-term multi-wavelength monitoring of this blazar may discriminate among the possible explanations for this quasi-periodicity.

  1. Extreme photo-polarimetric behaviour of the blazar AO 0235+164

    CERN Document Server

    Cellone, Sergio A; Combi, Jorge A; Marti, Josep

    2007-01-01

    We present optical photo-polarimetric observations with high temporal resolution of the blazar AO 0235+164. Our data, the first to test the photo-polarimetric behaviour of this object at very short time-scales, show significant micro-variability in total flux, colour index, linear polarization degree, and position angle. Strong inter-night variations are also detected for these parameters. Although no correlation between colour index and total flux was found, our data seem to support the general bluer-when-brighter trend already known for this object. The polarization degree, in turn, shows no correlation with total flux, but a clear trend in the sense that colour index is redder (the spectrum is softer) when the measured polarization is higher.

  2. Fourier Analysis of Blazar Variability: Klein-Nishina Effects and the Jet Scattering Environment

    CERN Document Server

    Finke, Justin D

    2015-01-01

    The strong variability of blazars can be characterized by power spectral densities (PSDs) and Fourier frequency-dependent time lags. In previous work, we created a new theoretical formalism for describing the PSDs and time lags produced via a combination of stochastic particle injection and emission via the synchrotron, synchrotron self-Compton, and external Compton (EC) processes. This formalism used the Thomson cross section and simple $\\delta$-function approximations to model the synchrotron and Compton emissivities. Here we expand upon this work, using the full Compton cross section and detailed and accurate emissivities. Our results indicate good agreement between the PSDs computed using the $\\delta$-function approximations and those computed using the accurate expressions, provided the observed photons are produced primarily by electrons with energies exceeding the lower limit of the injected particle population. Breaks are found in the PSDs at frequencies corresponding to the cooling timescales of the ...

  3. Constraining the Location of Gamma-Ray Flares in Luminous Blazars

    Science.gov (United States)

    Nalewajko, Krzysztof; Begelman, Mitchell C.; Sikora, Marek

    2014-07-01

    Locating the gamma-ray emission sites in blazar jets is a long standing and highly controversial issue. We jointly investigate several constraints on the distance scale r and Lorentz factor Γ of the gamma-ray emitting regions in luminous blazars (primarily flat spectrum radio quasars). Working in the framework of one-zone external radiation Comptonization models, we perform a parameter space study for several representative cases of actual gamma-ray flares in their multiwavelength context. We find a particularly useful combination of three constraints: from an upper limit on the collimation parameter Γθ ~ 0.1-0.7. Typical values of r corresponding to moderate values of Γ ~ 20 are in the range 0.1-1 pc, and are determined primarily by the observed variability timescale t var, obs. Alternative scenarios motivated by the observed gamma-ray/millimeter connection, in which gamma-ray flares of t var, obs ~ a few days are located at r ~ 10 pc, are in conflict with both the SSC and cooling constraints. Moreover, we use a simple light travel time argument to point out that the gamma-ray/millimeter connection does not provide a significant constraint on the location of gamma-ray flares. We argue that spine-sheath models of the jet structure do not offer a plausible alternative to external radiation fields at large distances; however, an extended broad-line region is an idea worth exploring. We propose that the most definite additional constraint could be provided by determination of the synchrotron self-absorption frequency for correlated synchrotron and gamma-ray flares.

  4. Long-term Multi-band Photometric Monitoring of Blazar S5 0716+714

    Science.gov (United States)

    Dai, Ben-zhong; Zeng, Wei; Jiang, Ze-jun; Fan, Zhong-hui; Hu, Wen; Zhang, Peng-fei; Yang, Qing-yun; Yan, Da-hai; Wang, Dan; Zhang, Li

    2015-06-01

    We present long-term optical multi-band photometric monitoring of blazar S5 0716+714, from 2004 January 11 to 2012 November 4, with high temporal resolution of approximately 15 minutes in the BVRI bands. The source was in an active state during the whole monitoring campaign, showing intraday variability in 11 of 72 days. The average magnitudes in each band were B = 14.398, V = 13.821, R = 13.255, and I = 12.885. The overall variability amplitudes were {Δ }B=1\\buildrel{{m}}\\over{.}834, {Δ }V=2\\buildrel{{m}}\\over{.}167, {Δ }R=2\\buildrel{{m}}\\over{.}148, and {Δ }I=1\\buildrel{{m}}\\over{.}912. The structure function showed that typical timescales for intraday variability were between approximately 2 and 7.5 hr. The intraday variability amplitudes were from a few percent to approximately 30%. We found typical variation rates of approximately 0.05 mag hr-1 in both the rising and falling phases, with a minimal variability timescale of 130 minutes. A 10 day period short-term variability was observed simultaneously in the BVRI bands. The discrete correlation function suggests that there is significant correlated variability between the B- and I-band light curves. However, no significant time lags were detected. The spectral behaviors in the different variability episodes were studied, and our observations show bluer-when-brighter behavior on long, short, and intraday timescales for the blazar S5 0716+714. The variability and relevant spectral trends can be explained by the shock-in-jet scenario.

  5. AGN astrophysics via multi-frequency monitoring of gamma-ray blazars in the Fermi-GST era

    CERN Document Server

    Angelakis, E; Zensus, J A; Nestoras, I; Marchili, N; Krichbaum, T P; Ungerechts, H; Max-Moerbeck, W; Pavlidou, V; Pearson, T J; Readhead, A C S; Richards, J L; Stevenson, M A

    2009-01-01

    The F-GAMMA-project is the coordinated effort of several observatories to understand the AGN phenomenon and specifically blazars via multi-frequency monitoring in collaboration with the {\\sl Fermi}-GST satellite since January 2007. The core observatories are: the Effelsberg 100-m, the IRAM 30-m and the OVRO 40-m telescope covering the range between 2.6 and 270 GHz. Effelsberg and IRAM stations do a monthly monitoring of the cm to sub-mm radio spectra of 60 selected blazars whereas the OVRO telescope is observing roughly 1200 objects at 15 GHz with a dense sampling of 2 points per week. The calibration uncertainty even at high frequencies, is of a few percent. 47% of the Effelsberg/Pico Veleta sample is included in the LBAS list. An update of the monitored sample is currently underway.

  6. Discovery of a wandering radio jet base after a large X-ray flare in the blazar Markarian 421

    CERN Document Server

    Niinuma, K; Doi, A; Hada, K; Nagai, H; Koyama, S

    2015-01-01

    We investigate the location of the radio jet bases ("radio cores") of blazars in radio images, and their stationarity by means of dense very long baseline interferometry (VLBI) observations. In order to measure the position of a radio core, we conducted 12 epoch astrometric observation of the blazar Markarian 421 with the VLBI Exploration of Radio Astrometry at 22 GHz immediately after a large X-ray flare, which occurred in the middle of 2011 September. For the first time, we find that the radio core is not stationary but rather changes its location toward 0.5 mas downstream. This angular scale corresponds to the de-projected length of a scale of $10^5$ Schwarzschild radii (Rs) at the distance of Markarian~421. This radio-core wandering may be a new type of manifestation associated with the phenomena of large X-ray flares.

  7. Time-Variable Linear Polarization as a Probe of the Physical Conditions in the Compact Jets of Blazars

    CERN Document Server

    Marscher, Alan P

    2014-01-01

    A single measurement of linear polarization of a nonthermal source provides direct information about the mean direction and level of ordering of the magnetic field. Monitoring of the polarization in blazars, combined with millimeter-wave VLBI imaging in both total and polarized intensity, has the potential to determine the geometry of the magnetic field. This is a key probe of the physical processes in the relativistic jet, such as ordered field components, turbulence, magnetic reconnections, magnetic collimation and acceleration of the jet flow, particle acceleration, and radiative processes that produce extremely luminous, highly variable nonthermal emission. Well-sampled monitoring observations of multi-waveband flux and radio-optical polarization of blazars show a variety of behavior. In some cases, the observed polarization patterns appear systematic, while in others randomness dominates. Explanations involve helical magnetic fields, turbulence, and perhaps particle acceleration that depends on the angle...

  8. Short-time Variability of Blazars via Non-linear, Time-dependent Synchrotron-Self Compton Radiative Losses

    CERN Document Server

    Röken, Christian; Schöneberg, Sebastian; Schuppan, Florian

    2016-01-01

    A leptonic one-zone model accounting for the radiation emission of blazars is presented. This model describes multiple successive injections of mono-energetic, ultra-relativistic, interacting electron populations, which are subjected to synchrotron and synchrotron-self Compton radiative losses. The electron number density is computed analytically by solving a time-dependent, relativistic transport equation. Moreover, the synchrotron and synchrotron-self Compton intensities as well as the corresponding total fluences are explicitly calculated. The lightcurves and fluences are plotted for realistic parameter values, showing that the model can simultaneously explain both the specific short-time variability in the flaring of blazars and the characteristic broad-band fluence behavior.

  9. Polarization Signatures of Relativistic Magnetohydrodynamic Shocks in the Blazar Emission Region - I. Force-free Helical Magnetic Fields

    CERN Document Server

    Zhang, Haocheng; Li, Hui; Böttcher, Markus

    2015-01-01

    The optical radiation and polarization signatures in blazars are known to be highly variable during flaring activities. It is frequently argued that shocks are the main driver of the flaring events. However, the spectral variability modelings generally lack detailed considerations of the self-consistent magnetic field evolution modeling, thus so far the associated optical polarization signatures are poorly understood. We present the first simultaneous modeling of the optical radiation and polarization signatures based on 3D magnetohydrodynamic simulations of relativistic shocks in the blazar emission environment, with the simplest physical assumptions. By comparing the results with observations, we find that shocks in a weakly magnetized environment will largely lead to significant changes in the optical polarization signatures, which are seldom seen in observations. Hence an emission region with relatively strong magnetization is preferred. In such an environment, slow shocks may produce minor flares with ei...

  10. 1WHSP: an IR-based sample of $\\sim$1,000 VHE $\\gamma$-ray blazar candidates

    CERN Document Server

    Arsioli, B; Giommi, P; Padovani, P; Marrese, P M

    2015-01-01

    Blazars are the dominant type of extragalactic sources at microwave and at $\\gamma$-ray energies. In the most energetic part of the electromagnetic spectrum (E>100GeV) a large fraction of high Galactic latitude sources are blazars of the High Synchrotron Peaked (HSP) type, that is BL Lac objects with synchrotron power peaking in the UV or in the X-ray band. HSP blazars are remarkably rare, with only a few hundreds of them expected to be above the sensitivity limits of currently available surveys. To find these very uncommon objects, we have devised a method that combines ALLWISE survey data with multi-frequency selection criteria. The sample was defined starting from a primary list of infrared colour-colour selected sources from the ALLWISE all sky survey database, and applying further restrictions on IR-radio and IR-X-ray flux ratios. Using a polynomial fit to the multi-frequency data (radio to X-ray) we estimated synchrotron peak frequencies and fluxes of each object. We assembled a sample including 992 sou...

  11. Optical spectroscopic observations of gamma-ray blazar candidates III. The 2013/2014 campaign in the Southern Hemisphere

    CERN Document Server

    Landoni, M; Paggi, A; D'Abrusco, R; Milisavljevic, D; Masetti, N; Smith, Howard A; Tosti, G; Chomiuk, L; Strader, J; Cheung, C C

    2015-01-01

    We report the results of our exploratory program carried out with the Southern Astrophysical Research (SOAR) telescope aimed at associating counterparts and establishing the nature of the Fermi Unidentified gamma-ray Sources (UGS). We selected the optical counterparts of 6 UGSs from the Fermi catalog on the basis of our recently discovered tight connection between infrared and gamma-ray emission found for the gamma-ray blazars detected by the Wide-Field Infrared Survey Explorer (WISE) in its the all-sky survey. We perform for the first time a spectroscopic study of the low-energy counterparts of Fermi UGS, in the optical band, confirming the blazar-like nature for the whole sample. We also present new spectroscopic observations of 6 Active Galaxies of Uncertain type associated with Fermi sources (AGUs) that appear to be BL Lac objects. Finally, we report the spectra collected for 6 known gamma-ray blazars belonging to the Roma BZCAT that were obtained to establish their nature or better estimate their redshif...

  12. Why Have Many of the Brightest Radio-loud Blazars Not Been Detected in Gamma-Rays by Fermi?

    Science.gov (United States)

    Lister, M. L.; Aller, M. F.; Aller, H. D.; Hovatta, T.; Max-Moerbeck, W.; Readhead, A. C. S.; Richards, J. L.; Ros, E.

    2015-09-01

    We use the complete MOJAVE 1.5 Jy sample of active galactic nuclei (AGNs) to examine the gamma-ray detection statistics of the brightest radio-loud blazars in the northern sky. We find that 23% of these AGNs were not detected above 0.1 GeV by the Fermi-LAT during the four-year 3FGL catalog period partly because of an instrumental selection effect and partly due to their lower Doppler boosting factors. Blazars with synchrotron peaks in their spectral energy distributions located below {10}13.4 Hz also tend to have high-energy peaks that lie below the 0.1 GeV threshold of the LAT, and are thus less likely to be detected by Fermi. The non-detected AGNs in the 1.5 Jy sample also have significantly lower 15 GHz radio modulation indices and apparent jet speeds, indicating that they have lower than average Doppler factors. Since the effective amount of relativistic Doppler boosting is enhanced in gamma-rays (particularly in the case of external inverse-Compton scattering), this makes them less likely to appear in the 3FGL catalog. Based on their observed properties, we have identified several bright radio-selected blazars that are strong candidates for future detection by Fermi.

  13. RoboPol: The optical polarization of gamma-ray--loud and gamma-ray--quiet blazars

    CERN Document Server

    Angelakis, E; Blinov, D; Pavlidou, V; Kiehlmann, S; Myserlis, I; Boettcher, M; Mao, P; Panopoulou, G V; Liodakis, I; King, O G; Balokovic, M; Kus, A; Kylafis, N; Mahabal, A; Marecki, A; Paleologou, E; Papadakis, I; Papamastorakis, I; Pazderski, E; Pearson, T J; Prabhudesai, S; Ramaprakash, A N; Readhead, A C S; Reig, P; Tassis, K; Urry, M; Zensus, J A

    2016-01-01

    We present average R-band optopolarimetric data, as well as variability parameters, from the first and second RoboPol observing season. We investigate whether gamma- ray--loud and gamma-ray--quiet blazars exhibit systematic differences in their optical polarization properties. We find that gamma-ray--loud blazars have a systematically higher polarization fraction (0.092) than gamma-ray--quiet blazars (0.031), with the hypothesis of the two samples being drawn from the same distribution of polarization fractions being rejected at the 3{\\sigma} level. We have not found any evidence that this discrepancy is related to differences in the redshift distribution, rest-frame R-band lu- minosity density, or the source classification. The median polarization fraction versus synchrotron-peak-frequency plot shows an envelope implying that high synchrotron- peaked sources have a smaller range of median polarization fractions concentrated around lower values. Our gamma-ray--quiet sources show similar median polarization fr...

  14. Optical counterparts of undetermined type $\\gamma$-ray Active Galactic Nuclei with blazar-like Spectral Energy Distributions

    CERN Document Server

    La Mura, G; Ciroi, S; Rafanelli, P; Salvetti, D; Berton, M; Cracco, V

    2015-01-01

    During its first four years of scientific observations, the Fermi Large Area Telescope (Fermi-LAT) detected 3033 $\\gamma$-ray sources above a 4$\\sigma$ significance level. Although most of the extra-Galactic sources are active galactic nuclei (AGN) of the blazar class, other families of AGNs are observed too, while a still high fraction of detections ($\\sim 30\\%$) remains with uncertain association or classification. According to the currently accepted interpretation, the AGN $\\gamma$-ray emission arises from inverse Compton (IC) scattering of low energy photons by relativistic particles confined in a jet that, in the case of blazars, is oriented very close to our line of sight. Taking advantage of data from radio and X-ray wavelengths, which we expect to be produced together with $\\gamma$-rays, providing a much better source localization potential, we focused our attention on a sample of $\\gamma$-ray Blazar Candidates of Undetermined Type (BCUs), starting a campaign of optical spectroscopic observations. The...

  15. Multi-frequency monitoring of gamma-ray loud blazars: I. Light curves and spectral energy distributions

    CERN Document Server

    Bach, U; Villata, M; Fuhrmann, L; Buemi, C S; Larionov, V M; Leto, P; Arkharov, A A; Coloma, J M; Di Paola, A; Dolci, M; Efimova, N; Forne, E; Ibrahimov, M A; Hagen-Thorn, V; Konstantinova, T; Kopatskaya, E; Lanteri, L; Kurtanidze, O M; Maccaferri, G; Nikolashvili, M G; Orlati, A; Ros, J A; Tosti, G; Trigilio, C; Umana, G

    2006-01-01

    Context: Being dominated by non-thermal emission from aligned relativistic jets, blazars allow us to elucidate the physics of extragalactic jets, and, ltimately, how the energy is extracted from the central black hole in radio-loud active galactic nuclei. Aims: Crucial information is provided by broad-band spectral energy distributions (SEDs), their trends with luminosity and correlated multi-frequency variability. With this study we plan to obtain a database of contemporaneous radio-to-optical spectra of a sample of blazars, which are and will be observed by current and future high-energy satellites. Methods: Since December 2004 we are performing a monthly multi-frequency radio monitoring of a sample of 35 blazars at the antennas in Medicina and Noto. Contemporaneous near-IR and optical observations for all our observing epochs are organised. Results: Until June 2006 about 4000 radio measurements and 5500 near-IR and optical measurements were obtained. Most of the sources show significant variability in all ...

  16. RoboPol: The optical polarization of gamma-ray-loud and gamma-ray-quiet blazars

    Science.gov (United States)

    Angelakis, E.; Hovatta, T.; Blinov, D.; Pavlidou, V.; Kiehlmann, S.; Myserlis, I.; Böttcher, M.; Mao, P.; Panopoulou, G. V.; Liodakis, I.; King, O. G.; Baloković, M.; Kus, A.; Kylafis, N.; Mahabal, A.; Marecki, A.; Paleologou, E.; Papadakis, I.; Papamastorakis, I.; Pazderski, E.; Pearson, T. J.; Prabhudesai, S.; Ramaprakash, A. N.; Readhead, A. C. S.; Reig, P.; Tassis, K.; Urry, M.; Zensus, J. A.

    2016-09-01

    We present average R-band optopolarimetric data, as well as variability parameters, from the first and second RoboPolobserving season. We investigate whether gamma-ray-loud and gamma-ray-quiet blazars exhibit systematic differences in their optical polarization properties. We find that gamma-ray-loud blazars have a systematically higher polarization fraction (0.092) than gamma-ray-quiet blazars (0.031), with the hypothesis of the two samples being drawn from the same distribution of polarization fractions being rejected at the 3σ level. We have not found any evidence that this discrepancy is related to differences in the redshift distribution, rest-frame R-band luminosity density, or the source classification. The median polarization fraction versus synchrotron-peak-frequency plot shows an envelope implying that high synchrotron-peaked sources have a smaller range of median polarization fractions concentrated around lower values. Our gamma-ray-quiet sources show similar median polarization fractions although they are all low synchrotron-peaked. We also find that the randomness of the polarization angle depends on the synchrotron peak frequency. For high synchrotron-peaked sources it tends to concentrate around preferred directions while for low synchrotron-peaked sources it is more variable and less likely to have a preferred direction. We propose a scenario which mediates efficient particle acceleration in shocks and increases the helical B-field component immediately downstream of the shock.

  17. Discovery of a Highly Polarized Optical Microflare in the Blazar S5 0716+714 During 2014 WEBT Campaign

    CERN Document Server

    Bhatta, Gopal; Ostrowski, Michal; Stawarz, Łukasz; Arkharov, A A; Akitaya, Hiroshi; Bachev, Rumen; Borman, Erika Benítez G A; Carosati, Daniele; Cason, Andy; Damljanovic, Goran; Dhalla, Sarah; Frasca, Antonio; Hiriart, David; Hu, Shao Ming; Itoh, Ryosuke; Jableka, Damian; Jorstad, Svetlana; Kawabata, Koji; Klimanov, Sergey; Kurtanidze, Omar; Larionov, Valeri; Laurence, Douglas; Leto, Giuseppe; Markowitz, Alex; Marscher, Alan P; Moody, J; Moritani, Yuki; Ohlert, Johannes; Di Paola, Andrea; Rizzi, Nicola; Sadun, Alberto; Sasada, Mahito; Sergeev, Sergey G; Strigachev, Anton; Takaki, Katsutoshi; Troitsky, Ivan; Ui, Takahiro; Villata, Massimo; Vince, Oliver; Webb, James; Yoshida, Michitoshi; Zola, Staszek

    2015-01-01

    The occurrence of low-amplitude flux variations in blazars on hourly timescales, commonly known as microvariability, is still a widely debated subject in high-energy astrophysics. Several competing scenarios have been proposed to explain such occurrences, including various jet plasma instabilities leading to the formation of shocks, magnetic reconnection sites, and turbulence. In this letter we present the results of our detailed investigation of a prominent, five-hour-long optical microflare detected during recent WEBT campaign in 2014, March 2-6 targeting the blazar 0716+714. After separating the flaring component from the underlying base emission continuum of the blazar, we find that the microflare is highly polarized, with the polarization degree $\\sim (40-60)\\%$$\\pm (2-10)\\%$, and the electric vector position angle $\\sim (10 - 20)$deg$\\pm (1-8)$deg slightly misaligned with respect to the position angle of the radio jet. The microflare evolution in the $(Q,\\,U)$ Stokes parameter space exhibits a looping b...

  18. The BL-Lac gamma-ray blazar PKS 1424+240 associated with a group of galaxies at z=0.6010

    CERN Document Server

    Rovero, A C; Donzelli, C; Pichel, A

    2016-01-01

    PKS 1424+240 is a BL-Lac blazar with unknown redshift that was detected at high-energy gamma rays by Fermi-LAT with a hard spectrum. At VHE, it was first detected by VERITAS and later confirmed by MAGIC. Its spectral energy distribution is highly attenuated at VHE gamma rays, which is coherent with distant sources. Several estimations enabled the redshift to be constrained to the range 0.6 < z < 1.3. These results place PKS 1424+240 in the very interesting condition of being probably the most distant blazar that has been detected at VHE. The ambiguity in the redshift is still large enough to prevent precise studies of the EBL and the intrinsic blazar spectrum. Given the difficulty of measuring spectroscopic redshifts for BL-Lac objects directly, we aim to establish a reliable redshift value for this blazar by finding its host group of galaxies. Elliptical galaxies are associated with groups, and BL-Lac objects are typically hosted by them, so we decided to search for the host group of the blazar. For th...

  19. INTEGRAL observations of the GeV blazar PKS1502+106 and of the hard X-ray bright Seyfert Galaxy Mkn841

    CERN Document Server

    Pian, E; Bazzano, A; Beckmann, V; Eckert, D; Ghisellini, G; Pursimo, T; Tagliaferri, G; Tavecchio, F; Tuerler, M; Bianchi, S; Bianchin, V; Hudec, R; Maraschi, L; Raiteri, C M; Soldi, S; Treves, A; Villata, M

    2010-01-01

    Extragalactic nuclear activity is best explored with observations at high energies, where the most extreme flux and spectral variations are expected to occur, witnessing changes in the accretion flow or in the kinematics of the plasma. In active galactic nuclei of blazar type, these variations are the most dramatic. By following blazar outbursts from their onset and by correlating the observed variations at many different wavelengths we can reconstruct the behavior of the plasma and map out the development of the flare within the jet. The advent of the Fermi satellite has allowed the start of a systematic and intensive monitoring program of blazars. Blazar outbursts are very effectively detected by the LAT instrument in the MeV-GeV domain, and these can be promptly followed up with other facilities. Based on a Fermi LAT detection of a high MeV-GeV state, we have observed the blazar PKS 1502+106 with the INTEGRAL satellite between 9 and 11 August 2008. Simultaneous Swift observations have been also accomplishe...

  20. X-ray spectral studies of TeV γ-ray emitting blazars

    Science.gov (United States)

    Wierzcholska, Alicja; Wagner, Stefan J.

    2016-05-01

    This work is a summary of the X-ray spectral studies of 29 TeV (1012 eV, tera-electron-volt) γ-ray emitting blazars observed with Swift/XRT, especially focusing on sources for which the X-ray regime allows us to study the low- and the high-energy ends of the particle distribution function. Variability studies require simultaneous coverage, ideally sampling different flux states of each source. This is achieved using X-ray observations by disentangling the high-energy end of the synchrotron emission and the low-energy end of the Compton emission, which are produced by the same electron population. We focused on a sample of 29 TeV γ-ray emitting blazars with the best signal-to-noise X-ray observations collected with Swift/XRT in the energy range 0.3-10 keV during 10 yr of Swift/XRT operations. We investigate the X-ray spectral shapes and the effects of different corrections for neutral hydrogen absorption and decompose the synchrotron and inverse Compton components. For five sources (3C 66A, S5 0716+714, W Comae, 4C +21.35 and BL Lacertae) a superposition of both components is observed in the X-ray band, permitting simultaneous, time-resolved studies of both ends of the electron distribution. The analysis of multi-epoch observations revealed that the break energy of the X-ray spectrum varies only by a small factor with flux changes. Flux variability is more pronounced in the synchrotron domain (high-energy end of the electron distribution) than in the Compton domain (low-energy end of the electron distribution). The spectral shape of the Compton domain is stable, while the flux of the synchrotron domain is variable. These changes cannot be described by simple variations of the cut-off energy, suggesting that the high-energy end of the electron distribution is not generally well described by cooling only.

  1. Multi-Frequency Blazar Micro-Variability as a Tool to Investigate Relativistic Jets

    Directory of Open Access Journals (Sweden)

    James R. Webb

    2016-08-01

    Full Text Available For the past 12 years we have been studying optical micro-variability of a sample of 15 Blazars. We summarize the results of this study and draw some basic conclusions about the characteristics of micro-variability. The intermittency, the stochastic nature, and the similar profile shapes seen in micro-variations at different times and in different objects have led us to a possible model to explain the observed micro-variations. The model is based on a strong shock propagating down a relativistic jet and encountering turbulence which causes density or magnetic field enhancements. We use the theory of Kirk, Reiger, and Mastichiadis (1998 to describe the pulse of synchrotron emission emanating from individual density enhancements energized by the shock. By fitting these “pulses” to micro-variability observations, we obtain excellent fits to actual micro-variations. The model predicts that the spectral index changes as a function of pulse duration. This effect should be observable in multi-frequency micro-variability data. We present the theoretical model, model fits of our micro-variability light curves, and preliminary multi-frequency micro-variability observations that support this model. A further test that has yet to be carried out involves observing polarization changes in different pulses.

  2. External Compton Scattering in Blazar Jets and the Location of the Gamma-Ray Emitting Region

    CERN Document Server

    Finke, Justin D

    2016-01-01

    I study the location of the $\\gamma$-ray emission in blazar jets by creating a Compton-scattering approximation valid for all anisotropic radiation fields in the Thomson through Klein-Nishina regimes, which is highly accurate and can speed up numerical calculations by up to a factor $\\sim10$. I apply this approximation to synchrotron self-Compton, and external Compton-scattering of photons from the accretion disk, broad-line region (BLR), and dust torus. I use a stratified BLR model and include detailed Compton-scattering calculations of a spherical and flattened BLR. I create two dust torus models, one where the torus is an annulus, and one where it is an extended disk. I present detailed calculations of the photoabsorption optical depth using my detailed BLR and dust torus models, including the full angle dependence. I apply these calculations to the emission from a relativistically moving blob traveling through these radiation fields. The ratio of $\\gamma$-ray to optical flux produces a predictable pattern...

  3. On conservative models of "the pair-production anomaly" in blazar spectra at Very High Energies

    CERN Document Server

    Dzhatdoev, T A

    2015-01-01

    For some blazars, the gamma-ray absorption features due to pair-production on the Extragalactic Background Light (EBL) are fainter than expected. The present work reviews the main models that could explain this paradox, with emphasis on conservative ones, that do not include any new physics. The models that are intrinsic to the source, do allow a very hard primary spectrum, but fail to explain a regular redshift dependence of the anomaly starting energy. The model that includes a contribution from secondary photons produced by cosmic rays (CR) near the Earth seems to require a well collimated CR beam, what is hard to achieve. Finally, the model with secondary photons produced in electromagnetic (EM) cascades initiated by primary gamma-rays is considered. In principle, it allows to decrease the statistical significance of the anomaly and, while requiring quite low EGMF strength B, does not contradict to most contemporary constraints on the B value. Additionally, it is shown that the recently observed correlati...

  4. Parsec scale polarization properties of the TeV blazar Markarian 421

    CERN Document Server

    Lico, R; Orienti, M; Gomez, J L; Casadio, C; D'Ammando, F; Blasi, M G; Cotton, W; Edwards, P G; Fuhrmann, L; Jorstad, S; Kino, M; Kovalev, Y Y; Krichbaum, T P; Marscher, A P; Paneque, D; Piner, B G; Sokolovsky, K V

    2015-01-01

    In this work we present a polarization analysis at radio frequencies of Markarian 421, one of the closest (z=0.03) TeV blazars. The observations were obtained, both in total and in polarized intensity, with the Very Long Baseline Array (VLBA) at 15, 24, and 43 GHz throughout 2011, with one observation per month (for a total of twelve epochs). We investigate the magnetic field topology and the polarization structure on parsec scale and their evolution with time. We detect polarized emission both in the core and in the jet region, and it varies with frequency, location and time. In the core region we measure a mean fractional polarization of about 1-2%, with a peak of about 4% in March at 43 GHz; the polarization angle is almost stable at 43 GHz, but it shows significant variability in the range 114-173 deg at 15 GHz. In the jet region the polarization properties show a more stable behavior; the fractional polarization is about 16% and the polarization angle is nearly perpendicular to the jet axis. The higher E...

  5. Multi-Frequency Observations of Gamma-Ray Blazar 1633+382

    Indian Academy of Sciences (India)

    S. G. Jorstad; A. P. Marscher; I. Agudo; P. S. Smith; V. M. Larionov; A. Lähteenmäki

    2011-03-01

    We perform monthly monitoring of the quasar 1633+382 (4C+38.41) within a sample of -ray blazars with the VLBA at 43 GHz along with optical photometric and polarimetric observations. We construct the -ray light curve of 1633+382 using data obtained by the Fermi LAT. We find that a high -ray state of the quasar starting in 2009 September is simultaneous with an increase of the flux in the mm-wave VLBI core. We resolve a superluminal feature on the VLBA images that appears to be responsible for the mm-wave flux increase. We find a strong correlation between optical and -ray light curves with a delay of -ray variations of 5 ± 3 days, as well as a strong correlation between optical flux and degree of polarization during the high -ray state. Comparison between the optical polarization position angle and that in the VLBI core supports the idea that in the quasar 1633+382 a high -ray state is connected with processes originating near the mm-VLBI core.

  6. The connection between the 15 GHz radio and gamma-ray emission in blazars

    CERN Document Server

    Max-Moerbeck, W; Hovatta, T; Pavlidou, V; Pearson, T J; Readhead, A C S; King, O G; Reeves, R

    2014-01-01

    Since mid-2007 we have carried out a dedicated long-term monitoring programme at 15 GHz using the Owens Valley Radio Observatory 40 meter telescope. One of the main goals of this programme is to study the relation between the radio and gamma-ray emission in blazars and to use it as a tool to locate the site of high energy emission. Using this large sample of objects we are able to characterize the radio variability, and study the significance of correlations between the radio and gamma-ray bands. We find that the radio variability of many sources can be described using a simple power law power spectral density, and that when taking into account the red-noise characteristics of the light curves, cases with significant correlation are rare. We note that while significant correlations are found in few individual objects, radio variations are most often delayed with respect to the gamma-ray variations. This suggests that the gamma-ray emission originates upstream of the radio emission. Because strong flares in mo...

  7. X-shaped radio sources as parent population of core-dominated triple blazars

    CERN Document Server

    Marecki, Andrzej

    2012-01-01

    There are a number of theories explaining the nature of the so-called X-shaped radio sources. According to one of them, an X-shaped source is indeed a cross whose one arm is associated with a double radio source that has changed its orientation in space, while the other arm is associated with relic lobes and its position indicates the former direction of the jets. Here, I present two new arguments in favour of this conjecture. Firstly, it is obvious that shortly after the repositioning, the pair of the new lobes must be very compact. To illustrate such a possibility, I show an EVN image of the central component of a triple source J1625+2712. When resolved, it appears as a compact double that is not aligned with the outer double so the whole source is indeed X-shaped. Secondly, I consider the situation when one of the arms of an X-shaped source is not intrinsically short but foreshortened by projection. I show two examples of triple sources whose central component is a blazar and the span of the lobes that str...

  8. Multi-Epoch Multiwavelength Spectra and Models for Blazar 3C~279

    CERN Document Server

    Hartman, R C

    2001-01-01

    Of the blazars detected by EGRET in GeV gamma rays, 3C 279 is not only the best-observed by EGRET, but also one of the best-monitored at lower frequencies. We have assembled eleven spectra, from GHz radio through GeV gamma rays, from the time intervals of EGRET observations. Although some of the data have appeared in previous publications, most are new, including data taken during the high states in early 1999 and early 2000. All of the spectra show substantial gamma-ray contribution to the total luminosity of the object; in a high state, the gamma-ray luminosity dominates over that at all other frequencies by a factor of more than 10. There is no clear pattern of time correlation; different bands do not always rise and fall together, even in the optical, X-ray, and gamma-ray bands. The spectra are modeled using a leptonic jet, with combined synchrotron self-Compton + external Compton gamma-ray production. Spectral variability of 3C 279 is consistent with variations of the bulk Lorentz factor of the jet, acco...

  9. The connection between radio and γ-ray emission in Fermi/LAT blazars

    Institute of Scientific and Technical Information of China (English)

    Xu-Liang Fan; Jin-Ming Bai; Hong-Tao Liu; Liang Chen; Neng-Hui Liao

    2012-01-01

    We collect the second Large Area Telescope AGN catalog (2LAC) and Monitor of Jets in AGN with VLBA Equipment (MOJAVE) quasi-simultaneous data to investigate the radio-γ connection of blazars.The cross sample contains 166 sources.The statistical analysis based on this sample confirms positive correlations between these two bands,but the correlations become weaker as the γ-ray energy increases.The statistical results between various parameters show negative correlations of γ-ray photon spectral index with γ-ray loudness for both Flat Spectrum Radio Quasars (FSRQs) and BL Lacertae objects,positive correlations of γ-ray variability index with the γ-ray loudness for FSRQs,a negative correlation of the γ-ray variability index with the γ-ray photon spectral index for FSRQs,and negative correlations of γ-ray photon spectral index with γ-ray luminosity for FSRQs.These results suggest that the γ-ray variability may be due to changes inside the γ-ray emission region like the injected power,rather than changes in the photon density of the external radiation fields,and the variability amplitude tends to be larger as the γ-rays are closer to the high energy peak of the spectral energy distribution (SED).No correlation of variability index found for BL Lacertae objects implies that variability behavior may differ below and above the peak energy.

  10. Kepler light curve analysis of the blazar W2R 1926+42

    CERN Document Server

    Mohan, P; Bachev, R; Strigachev, A

    2015-01-01

    We study the long term Kepler light curve of the blazar W2R 1926+42 ($\\sim$ 1.6 years) which indicates a variety of variability properties during different intervals of observation. The normalized excess variance, $F_{\\rm var}$ ranges from 1.8 % in the quiescent phase and 43.3 % in the outburst phase. We find no significant deviation from linearity in the $F_{\\rm var}$-flux relation. Time series analysis is conducted using the Fourier power spectrum and the wavelet analysis methods to study the power spectral density (PSD) shape, infer characteristic timescales and statistically significant quasi-periodic oscillations (QPOs). A bending power law with an associated timescale of $T_B = 6.2^{+6.4}_{-3.1}$ hours is inferred in the PSD analysis. We obtain a black hole mass of $M_\\bullet = (1.5 - 5.9) \\times 10^7 M_\\odot$ for the first time using $F_{\\rm var}$ and the bend timescale for this source. From a mean outburst lifetime of days, we infer a distance from the jet base $r \\leq 1.75$ pc indicating that the out...

  11. Suzaku Observations of Extreme MeV Blazar Swift J0746.3+2548

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Shin; Sato, Rie; Takahashi, Tadayuki; Kataoka, Jun; Madejski, Greg; Sikora, Marek; Tavecchio, Fabrizio; Sambruna, Rita; Romani, Roger; Edwards, Philip G.; Pursimo, Tapio

    2008-12-01

    We report the Suzaku observations of the high luminosity blazar SWIFT J0746.3+2548 (J0746) conducted in November 2005. This object, with z = 2.979, is the highest redshift source observed in the Suzaku Guaranteed Time Observer (GTO) period, is likely to show high gamma-ray flux peaking in the MeV range. As a result of the good photon statistics and high signal-to-noise ratio spectrum, the Suzaku observation clearly confirms that J0746 has an extremely hard spectrum in the energy range of 0.3-24 keV, which is well represented by a single power-law with a photon index of {Lambda}{sub ph} {approx_equal} 1.17 and Galactic absorption. The multiwavelength spectral energy distribution of J0746 shows two continuum components, and is well modeled assuming that the high-energy spectral component results from Comptonization of the broad-line region photons. In this paper we search for the bulk Compton spectral features predicted to be produced in the soft X-ray band by scattering external optical/UV photons by cold electrons in a relativistic jet. We discuss and provide constraints on the pair content resulting from the apparent absence of such features.

  12. Suzaku Observations of Extreme MeV Blazar SWIFT J0746.3+2548

    CERN Document Server

    Watanabe, Shin; Takahashi, Tadayuki; Kataoka, Jun; Madejski, Greg; Sikora, Marek; Tavecchio, Fabrizio; Sambruna, Rita; Romani, Roger; Edwards, Philip G; Pursimo, Tapio

    2008-01-01

    We report the Suzaku observations of the high luminosity blazar SWIFT J0746.3+2548 (J0746) conducted in November 2005. This object, with z = 2.979, is the highest redshift source observed in the Suzaku Guaranteed Time Observer (GTO) period, is likely to show high gamma-ray flux peaking in the MeV range. As a result of the good photon statistics and high signal-to-noise ratio spectrum, the $Suzaku$ observation clearly confirms that J0746 has an extremely hard spectrum in the energy range of 0.3-24 keV, which is well represented by a single power-law with a photon index of 1.17 and Galactic absorption. The multiwavelength spectral energy distribution of J0746 shows two continuum components, and is well modeled assuming that the high-energy spectral component results from Comptonization of the broad-line region photons. In this paper we search for the bulk Compton spectral features predicted to be produced in the soft X-ray band by scattering external optical/UV photons by cold electrons in a relativistic jet. W...

  13. Polarization angle swings in blazars: The case of 3C 279

    CERN Document Server

    Kiehlmann, S; Jorstad, S G; Sokolovsky, K V; Schinzel, F K; Marscher, A P; Larionov, V M; Agudo, I; Akitaya, H; Benítez, E; Berdyugin, A; Blinov, D A; Bochkarev, N G; Borman, G A; Burenkov, A N; Casadio, C; Doroshenko, V T; Efimova, N V; Fukazawa, Y; Gómez, J L; Grishina, T S; Hagen-Thorn, V A; Heidt, J; Hiriart, D; Itoh, R; Joshi, M; Kawabata, K S; Kimeridze, G N; Kopatskaya, E N; Korobtsev, I V; Krajci, T; Kurtanidze, O M; Kurtanidze, S O; Larionova, E G; Larionova, L V; Lindfors, E; López, J M; McHardy, I M; Molina, S N; Moritani, Y; Morozova, D A; Nazarov, S V; Nikolashvili, M G; Nilsson, K; Pulatova, N G; Reinthal, R; Sadun, A; Sasada, M; Savchenko, S S; Sergeev, S G; Sigua, L A; Smith, P S; Sorcia, M; Spiridonova, O I; Takaki, K; Takalo, L O; Taylor, B; Troitsky, I S; Uemura, M; Ugolkova, L S; Ui, T; Yoshida, M; Zensus, J A; Zhdanova, V E

    2016-01-01

    Over the past few years, several occasions of large, continuous rotations of the electric vector position angle (EVPA) of linearly polarized optical emission from blazars have been reported. These events are often coincident with high energy gamma-ray flares and they have attracted considerable attention, as they could allow one to probe the magnetic field structure in the gamma-ray emitting region of the jet. The flat-spectrum radio quasar 3C279 is one of the most prominent examples showing this behaviour. Our goal is to study the observed EVPA rotations and to distinguish between a stochastic and a deterministic origin of the polarization variability. We have combined multiple data sets of R-band photometry and optical polarimetry measurements of 3C279, yielding exceptionally well-sampled flux density and polarization curves that cover a period of 2008-2012. Several large EVPA rotations are identified in the data. We introduce a quantitative measure for the EVPA curve smoothness, which is then used to test ...

  14. On the soft X-ray spectra of $\\gamma$-loud blazars

    CERN Document Server

    Comastri, A; Ghisellini, G; Molendi, S

    1996-01-01

    ROSAT observations of a large sample of bright gamma-ray (E > 100 MeV) blazars are presented. Results of a detailed spectral analysis in the soft energy distribution with particular emphasis on the relation between X-ray and gamma-ray properties. A significant anti-correlation between X-ray and gamma-ray spectral shapes of flat radio spectrum quasars (FSRQ) and BL Lacs has been discovered. A different shape in the overall energy distributions from radio to gamma-ray energies between FSRQ and BL Lacs is also implied by the correlation of their broad-band spectral indices $\\alpha_{ro}$ and $\\alpha_{x emission and the hard X-ray to gamma-ray emission originate from the same electron population, via, respectively, the synchrotron process and the inverse Compton mechanism. We suggest that a key parameter for understanding the overall energy distributions of both classes of objects is the energy at which the synchrotron emission peaks in a $\

  15. An eclipsing binary black hole candidate system in the blazar Mrk 421

    CERN Document Server

    Benitez, E; Fraija, N; Hernandez, X; Lopez-Corona, O; Lora-Clavijo, F D; Mendoza, S

    2015-01-01

    Removing strong outbursts from multiwavelength light curves of the blazar Mrk 421, we construct outburstless time series for this system. A model-independent power spectrum light curve analysis in the optical, hard X-ray and gamma-rays of this outburstless state shows clear evidence for a periodicity of \\approx 400 days. A subsequent full maximum likelihood analysis fitting an eclipse model confirms a periodicity of 387.16 days. The power spectrum of the signal in the outburstless state of the source does not follow a flicker noise behaviour and so, the system producing it is not self-organised. This means that the periodicity is not produced by any internal physical processes associated to the central engine. The simplest physical mechanism to which this periodicity could be ascribed is a dynamical effect produced by an orbiting supermassive black hole companion of mass \\sim 10^7 M_\\odot eclipsing the central black hole, which has a mass \\sim 10^8 M_\\odot. The optimal model restricts the physics of the eclip...

  16. Search for neutrino emission in gamma-ray flaring blazars with the ANTARES telescope

    CERN Document Server

    Sánchez-Losa, Agustín

    2012-01-01

    The ANTARES telescope observes a full hemisphere of the sky all the time with a duty cycle close to 100%. This makes it well suited for an extensive observation of neutrinos produced in astrophysical transient sources. In the surrounding medium of blazars, i.e. active galactic nuclei with their jets pointing almost directly towards the observer, neutrinos may be produced together with gamma-rays by hadronic interactions, so a strong correlation between neutrinos and gamma-rays emissions is expected. The time variability information of the studied source can be obtained by the gamma-ray light curves measured by the LAT instrument on-board the Fermi satellite. If the expected neutrino flux observation is reduced to a narrow window around the assumed neutrino production period, the point-source sensitivity can be drastically improved. The ANTARES data collected in 2008 has been analysed looking for neutrinos detected in the high state period of ten bright and variable Fermi sources assuming that the neutrino emi...

  17. The blazar-like radio structure of the TeV source IC310

    CERN Document Server

    Kadler, Matthias; Ros, Eduardo; Mannheim, Karl; Elsässer, Dominik; Bach, Uwe

    2012-01-01

    Context. The radio galaxy IC310 in the Perseus cluster has recently been detected in the gamma-ray regime at GeV and TeV energies. The TeV emission shows time variability and an extraordinarily hard spectrum, even harder than the spectrum of the similar nearby gamma-ray emitting radio galaxy M87. Aims. High-resolution studies of the radio morphology help to constrain the geometry of the jet on sub-pc scales and to find out where the high-energy emission might come from. Methods. We analyzed May 2011 VLBA data of IC310 at a wavelength of 3.6 cm, revealing the parsec-scale radio structure of this source. We compared our findings with more information available from contemporary single-dish flux density measurements with the 100-m Effelsberg radio telescope. Results. We have detected a one-sided core-jet structure with blazar-like, beamed radio emission oriented along the same position angle as the kiloparsec scale radio structure observed in the past by connected interferometers. Doppler-boosting favoritism is ...

  18. Extremely high polarization in the 2010 outburst of blazar 3C 454.3

    Energy Technology Data Exchange (ETDEWEB)

    Sasada, Mahito; Kino, Masaru [Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan); Uemura, Makoto; Yoshida, Michitoshi; Kawabata, Koji S.; Akitaya, Hiroshi [Hiroshima Astrophysical Science Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Fukazawa, Yasushi; Yasuda, Hajimu; Itoh, Ryosuke; Sakimoto, Kiyoshi; Ikejiri, Yuki; Ohsugi, Takashi; Komatsu, Tomoyuki; Miyamoto, Hisashi; Nagae, Osamu; Tanaka, Hiroyuki [Department of Physical Science, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima 739-8526 (Japan); Yamanaka, Masayuki [Kwasan Observatory, Kyoto University, 17-1 Kitakazan-ohmine-cho, Yamashina-ku, Kyoto 607-8471 (Japan); Nakaya, Hidehiko [National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588 (Japan); Sato, Shuji, E-mail: sasada@kusastro.kyoto-u.ac.jp [Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602 (Japan)

    2014-04-01

    The gamma-ray-detected blazar 3C 454.3 exhibits dramatic flux and polarization variations in the optical and near-infrared bands. In 2010 December, the object emitted a very bright outburst. We monitored it for approximately four years (including the 2010 outburst) by optical and near-infrared photopolarimetry. During the 2010 outburst, the object emitted two rapid, redder brightenings, at which the polarization degrees (PDs) in both bands increased significantly and the bands exhibited a frequency-dependent polarization. The observed frequency-dependent polarization leads us to propose that the polarization vector is composed of two vectors. Therefore, we separate the observed polarization vectors into short- and long-term components that we attribute to the emissions of the rapid brightenings and the outburst that varied the timescale of days and months, respectively. The estimated PD of the short-term component is greater than the maximum observed PD and is close to the theoretical maximum PD. We constrain the bulk Lorentz factors and inclination angles between the jet axis and the line of sight from the estimated PDs. In this case, the inclination angle of the emitting region of short-term component from the first rapid brightening should be equal to 90°, because the estimated PD of the short-term component was approximately equal to the theoretical maximum PD. Thus, the Doppler factor at the emitting region of the first rapid brightening should be equal to the bulk Lorentz factor.

  19. Time-dependent Radiation Transfer in the Internal Shock Model Scenario for Blazar Jets

    CERN Document Server

    Joshi, Manasvita

    2010-01-01

    We describe the time-dependent radiation transfer in blazar jets, within the internal shock model. We assume that the central engine, which consists of a black hole and an accretion disk, spews out relativistic shells of plasma with different velocity, mass, and energy. We consider a single inelastic collision between a faster (inner) and a slower (outer) moving shell. We study the dynamics of the collision and evaluate the subsequent emission of radiation via the synchrotron and synchrotron self Compton (SSC) processes after the interaction between the two shells has begun. The collision results in the formation of a forward shock (FS) and a reverse shock (RS) that convert the ordered bulk kinetic energy of the shells into magnetic field energy and accelerate the particles, which then radiate. We assume a cylindrical geometry for the emission region of the jet. We treat the self-consistent radiative transfer by taking into account the inhomogeneity in the photon density throughout the region. In this paper, ...

  20. First broadband characterization and redshift determination of the VHE blazar MAGIC J2001+439

    CERN Document Server

    Aleksić, J; Antonelli, L A; Antoranz, P; Babic, A; Bangale, P; de Almeida, U Barres; Barrio, J A; González, J Becerra; Bednarek, W; Bernardini, E; Biland, A; Blanch, O; Bonnefoy, S; Bonnoli, G; Borracci, F; Bretz, T; Carmona, E; Carosi, A; Fidalgo, D Carreto; Colin, P; Colombo, E; Contreras, J L; Cortina, J; Covino, S; Da Vela, P; Dazzi, F; De Angelis, A; De Caneva, G; De Lotto, B; Mendez, C Delgado; Doert, M; Domínguez, A; Prester, D Dominis; Dorner, D; Doro, M; Einecke, S; Eisenacher, D; Elsaesser, D; Farina, E; Ferenc, D; Fonseca, M V; Font, L; Frantzen, K; Fruck, C; López, R J García; Garczarczyk, M; Terrats, D Garrido; Gaug, M; Godinović, N; Muñoz, A González; Gozzini, S R; Hadasch, D; Hayashida, M; Herrera, J; Herrero, A; Hildebrand, D; Hose, J; Hrupec, D; Idec, W; Kadenius, V; Kellermann, H; Kodani, K; Konno, Y; Krause, J; Kubo, H; Kushida, J; La Barbera, A; Lelas, D; Lewandowska, N; Lindfors, E; Lombardi, S; López, M; López-Coto, R; López-Oramas, A; Lorenz, E; Lozano, I; Makariev, M; Mallot, K; Maneva, G; Mankuzhiyil, N; Mannheim, K; Maraschi, L; Marcote, B; Mariotti, M; Martínez, M; Mazin, D; Menzel, U; Meucci, M; Miranda, J M; Mirzoyan, R; Moralejo, A; Munar-Adrover, P; Nakajima, D; Niedzwiecki, A; Nilsson, K; Nishijima, K; Noda, K; Nowak, N; Orito, R; Overkemping, A; Paiano, S; Palatiello, M; Paneque, D; Paoletti, R; Paredes, J M; Paredes-Fortuny, X; Partini, S; Persic, M; Prada, F; Moroni, P G Prada; Prandini, E; Preziuso, S; Puljak, I; Reinthal, R; Rhode, W; Ribó, M; Rico, J; Garcia, J Rodriguez; Rügamer, S; Saggion, A; Saito, T; Saito, K; Satalecka, K; Scalzotto, V; Scapin, V; Schultz, C; Schweizer, T; Shore, S N; Sillanpää, A; Sitarek, J; Snidaric, I; Sobczynska, D; Spanier, F; Stamatescu, V; Stamerra, A; Steinbring, T; Storz, J; Strzys, M; Sun, S; Surić, T; Takalo, L; Takami, H; Tavecchio, F; Temnikov, P; Terzić, T; Tescaro, D; Teshima, M; Thaele, J; Tibolla, O; Torres, D F; Toyama, T; Treves, A; Uellenbeck, M; Vogler, P; Wagner, R M; Zandanel, F; Zanin, R; D'Ammando, F; Hovatta, T; Larionov, V M; Max-Moerbeck, W; Perri, M; Readhead, A C S; Richards, J L; Sakamoto, T; Schwartz, R D; Verrecchia, F; Reyes, L C

    2014-01-01

    We aim to characterize the broadband emission from 2FGL J2001.1+4352, which has been associated with the unknown-redshift blazar MG4 J200112+4352. Based on its gamma-ray spectral properties, it was identified as a potential very high energy (VHE; E > 100 GeV) gamma-ray emitter. The source was observed with MAGIC first in 2009 and later in 2010 within a multi-instrument observation campaign. The MAGIC observations yielded 14.8 hours of good quality stereoscopic data. The object was monitored at radio, optical and gamma-ray energies during the years 2010 and 2011. The source, named MAGIC J2001+439, is detected for the first time at VHE with MAGIC at a statistical significance of 6.3 {\\sigma} (E > 70 GeV) during a 1.3-hour long observation on 2010 July 16. The multi-instrument observations show variability in all energy bands with the highest amplitude of variability in the X-ray and VHE bands. We also organized deep imaging optical observations with the Nordic Optical Telescope in 2013 to determine the source r...

  1. Stochastic Gyroresonant Acceleration for Hard Electron Spectra of Blazars: Effect of Damping of Cascading Turbulence

    Science.gov (United States)

    Kakuwa, Jun

    2016-01-01

    Stochastic acceleration of nonthermal electrons is investigated in the context of hard photon spectra of blazars. It is well known that this acceleration mechanism can produce a hard electron spectrum of m≡ ∂ {ln}{n}{{e}}(γ )/∂ {ln}γ =2 with the high-energy cutoff, called an ultrarelativistic Maxwellian-like distribution, where {n}{{e}}(γ ) is an electron energy spectrum. We revisit the formation of this characteristic spectrum, considering a particular situation where the electrons are accelerated through gyroresonant interaction with magnetohydrodynamic wave turbulence driven by the turbulent cascade. By solving kinetic equations of the turbulent fields, electrons, and photons emitted via the synchrotron self-Compton (SSC) process, we demonstrate that in the non-test-particle treatment, the formation of a Maxwellian-like distribution is prevented by the damping effect on the turbulent fields due to the electron acceleration, at least unless an extreme parameter value is chosen. Instead, a softer electron spectrum with the index of m ≈ -1 is produced if the Kolmogorov-type cascade is assumed. The SSC spectrum that originates from the resultant softer electron spectrum is still hard, but somewhat softer and broader than the case of m = 2. This change of achievable hardness should be noted when this basic particle acceleration scenario is accurately tested with observations of hard photon spectra.

  2. Multiband optical-NIR variability of blazars on diverse time-scales

    Science.gov (United States)

    Agarwal, Aditi; Gupta, Alok C.; Bachev, R.; Strigachev, A.; Semkov, E.; Wiita, Paul J.; Böttcher, M.; Boeva, S.; Gaur, H.; Gu, M. F.; Peneva, S.; Ibryamov, S.; Pandey, U. S.

    2015-08-01

    To search for optical variability on a wide range of time-scales, we have carried out photometric monitoring of two flat spectrum radio quasars, 3C 454.3 and 3C 279, plus one BL Lac, S5 0716+714, all of which have been exhibiting remarkably high activity and pronounced variability at all wavelengths. CCD magnitudes in B, V, R, and I passbands were determined for ˜7000 new optical observations from 114 nights made during 2011-2014, with an average length of ˜4 h each, at seven optical telescopes: four in Bulgaria, one in Greece, and two in India. We measured multiband optical flux and colour variations on diverse time-scales. Discrete correlation functions were computed among B, V, R, and I observations, to search for any time delays. We found weak correlations in some cases with no significant time lags. The structure function method was used to estimate any characteristic time-scales of variability. We also investigated the spectral energy distribution of the three blazars using B, V, R, I, J, and K passband data. We found that the sources almost always follow a bluer-when-brighter trend. We discuss possible physical causes of the observed spectral variability.

  3. ON THE ORIGIN OF THE γ-RAY/OPTICAL LAGS IN LUMINOUS BLAZARS

    International Nuclear Information System (INIS)

    Blazars are strongly variable sources that occasionally show spectacular flares visible in various energy bands. These flares are often, but not always, correlated. In a number of cases, the peaks of optical flares are found to be somewhat delayed with respect to the γ-ray peaks. One notable example of such a delay was found in 3C 279 by Hayashida et al. and interpreted as a result of steeper drop with a distance of the energy density of an external radiation field than of the magnetic energy density. In this paper, we demonstrate that, in general, depending on the respective energy density profile along the jet, such lags can have both signs and that they can take place for any ratio of these energy densities. We study the dependence of such lags on the ratio of these energy densities at a distance of a maximal energy dissipation in a jet, on their gradients, as well as on the time profile of the relativistic electron injection within the moving source. We show how prominent such lags can be, and their expected timescales. We suggest that studies of such lags can provide a powerful tool to resolve the structure of relativistic jets and their radiative environment. As an example we model the lag observed in 3C 279, showing that in this object the flare is produced at a distance of a few parsecs from the central black hole, consistent with our previous inferences based on the spectra and optical polarization properties.

  4. AGILE detection of intense gamma-ray emission from the blazar PKS 1510-089

    CERN Document Server

    Pucella, G; D'Ammando, F; Tavani, M; Raiteri, C M; Villata, M; Argan, A; Barbiellini, G; Boffelli, F; Bulgarelli, A; Caraveo, P; Cattaneo, P W; Chen, A W; Cocco, V; Costa, E; Del Monte, E; De Paris, G; Di Cocco, G; Donnarumma, I; Evangelista, Y; Feroci, M; Fiorini, M; Froysland, T; Fuschino, F; Galli, M; Gianotti, F; Giuliani, A; Labanti, C; Lapshov, I; Lazzarotto, F; Lipari, P; Longo, F; Marisaldi, M; Mereghetti, S; Morselli, A; Pacciani, L; Pellizzoni, A; Perotti, F; Picozza, P; Prest, M; Rapisarda, M; Rappoldi, A; Soffitta, P; Trifoglio, M; Trois, A; Vallazza, E; Vercellone, S; Zambra, A; Zanello, D; Antonelli, L A; Colafrancesco, S; Cutini, S; Gasparrini, D; Giommi, P; Pittori, C; Verrecchia, F; Salotti, L; Aller, M F; Aller, H D; Carosati, D; Larionov, V M; Ligustri, R

    2008-01-01

    We report the detection by the AGILE (Astro-rivelatore Gamma a Immagini LEggero) satellite of an intense gamma-ray flare from the source AGL J1511-0909, associated with the powerful quasar PKS 1510-089, during ten days of observations from 23 August to 1 September 2007. During the observation period, the source was in optical decrease following a flaring event monitored by the GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT). The simultaneous gamma-ray, optical, and radio coverage allows us to study the spectral energy distribution and the theoretical models based on the synchrotron and inverse Compton (IC) emission mechanisms. AGILE observed the source with its two co-aligned imagers, the Gamma-Ray Imaging Detector and the hard X-ray imager Super-AGILE sensitive in the 30 MeV - 50 GeV and 18 - 60 keV bands, respectively. Between 23 and 27 August 2007, AGILE detected gamma-ray emission from PKS 1510-089 when this source was located about 50 degrees off-axis, with an average flux o...

  5. Time dependent approach of TeV blazars based on a model of inhomogeneous stratified jet

    International Nuclear Information System (INIS)

    The study of the emission and variability mechanisms of TeV blazars has been the subject of intensive research for years. The homogeneous one-zone model commonly used is puzzling since it yields very high Lorentz factor, in contradiction with other observational evidences. In this work, I describe a new time dependent multi-zone approach, in the framework of the two-flow model. I compute the emission of a full jet, where relativistic electron-positron pairs distributed in pileup propagate. The evolution and the emission of the plasma is computed taking into account a turbulent heating term, some radiative cooling, and a pair production term due to photo-annihilation process. Applied to PKS 2155-304, the model allows the reproduction of the full spectra, as well as the simultaneous multi wavelength variability, with a relatively small Lorentz factor. The variability is explained by the instability of the pair creation process. Nonetheless, the value is still high to agree with other observational evidences in radio. Hence, I show in the last part of this work how to conciliate high Lorentz factor with the absence of apparent superluminal movement in radio, by taking into account the effect of the opening angle on the appearance of relativistic jets. (author)

  6. On the direct correlation between gamma-rays and PeV neutrinos from blazars

    CERN Document Server

    Gao, Shan; Winter, Walter

    2016-01-01

    We study the frequently used assumption in multi-messenger astrophysics that the gamma-ray and neutrino fluxes are directly connected because they are assumed to be produced by the same photohadronic production chain. An interesting candidate source for this test is the flat-spectrum radio quasar PKS B1424-418, which recently called attention of a potential correlation between an IceCube PeV-neutrino event and its burst phase. We simulate both the multi-waveband photon and the neutrino emission from this source using a self-consistent radiation model. We demonstrate that a simple hadronic model cannot adequately describe the spectral energy distribution for this source, but a lepto-hadronic model with sub-dominant hadronic component can reproduce the multi-waveband photon spectrum observed during various activity phases of the blazar. As a conclusion, up to about 0.3 neutrino events may coincide with the burst, which implies that the leptonic contribution dominates in the relevant energy band. We also demonst...

  7. Multi-Wavelength Variability Properties of Fermi Blazar S5 0716+714

    Indian Academy of Sciences (India)

    N. H. Liao; J. M. Bai; H. T. Liu; S. S. Weng; Liang Chen; F. Li

    2014-09-01

    The multi-wavelength variability properties of blazar S5 0716 + 714 are reported. We construct multi-wavelength light curves of radio, optical, X-ray and -ray including our optical observation at Yunnan Observatories. In all the bands, the light curves show intense variabilities. The variability amplitudes in -ray and optical bands are larger than those in the hard X-ray and radio bands. The characteristic variability timescales at 14.5 GHz, optical, X-ray, and -ray bands are comparable. The variations of the hard X-ray and 14.5GHz emissions are correlated with zero lag, and so are the V band and -ray variations. The multi-wavelength variability behaviours can be naturally explained by the classic leptonic model. We model the average SED of S5 0716 + 714 by leptonic model. The SSC+ERC model using the external seed photons from hot dust or Broad Line Region (BLR) emission is probably favourable avoiding the extreme input parameters from the pure SSC model.

  8. Evidence for quasi-periodic modulation in the gamma-ray blazar PG 1553+113

    Science.gov (United States)

    Cutini, Sara; Ciprini, Stefano; Larsson, Stefan; Thompson, David John; Stamerra, Antonio; Fermi LAT Collaboration

    2016-01-01

    For the first time a gamma-ray and multiwavelength nearly-periodic oscillation in an active galactic nucleus is reported using the Fermi Large Area Telescope (LAT). A quasi-periodicity in the gamma-ray flux (E>100 MeV and E>1 GeV) is observed from the well-known GeV/TeV BL Lac object PG 1553+113 (Ackermann et al. submitted). The significance of the 2.18 +/- 0.08 year-period gamma-ray modulation, seen in 3.5 oscillation maxima observed, is supported by significant cross-correlated variations observed in radio and optical flux light curves, through data collected in the OVRO, Tuorla, KAIT, and CSS monitoring programs and Swift UVOT. The optical cycle, appearing in about 10 years of data, has a similar period, while the radio-band oscillation observed at 15 GHz is less regular and coherent. The available X-ray flux data obtained by Swift XRT appears also to be linearly correlated with the gamma-ray flux. Further long-term multi-wavelength monitoring of this blazar may discriminate among the possible explanations for this first evidence of periodicity.

  9. Absorption of 10--200 Gev Gamma Rays by Radiation from BLR in Blazars

    CERN Document Server

    Liu, H T

    2008-01-01

    In this paper, we study the photon-photon pair production optical depth for gamma-rays with energies from 10 to 200 GeV emitted by powerful blazars due to the diffuse radiation field of broad line region (BLR). There are four key parameters in the BLR model employed to determine the $\\gamma-\\gamma$ attenuation optical depth of these gamma-rays. They are the gamma-ray emitting radius $R_{\\gamma}$, the BLR luminosity $L_{\\rm{BLR}}$, the BLR half thickness $h$ and the ratio $\\tau_{\\rm{BLR}}/f_{\\rm{cov}}$ of the Thomson optical depth to the covering factor of BLR. For FSRQs, on average, it is impossible for gamma-rays with energies from 10 to 200 GeV to escape from the diffuse radiation field of the BLR. If $\\it GLAST$ could detect these gamma-rays for most of FSRQs, the gamma-ray emitting region is likely to be outside the cavity formed by the BLR. Otherwise, the emitting region is likely to be inside the BLR cavity. As examples, we estimate the photon-photon absorption optical depth of gamma-rays with energies ...

  10. Tests of the Einstein Equivalence Principle using TeV Blazars

    CERN Document Server

    Wei, Jun-Jie; Gao, He; Wu, Xue-Feng

    2016-01-01

    The observed time delays between different energy bands from TeV blazars provide a new interesting way of testing the Einstein Equivalence Principle (EEP). If the whole time delay is assumed to be dominated by the gravitational field of the Milky Way, the conservative upper limit on the EEP can be estimated. Here we show that the strict limits on the differences of the parameterized post-Newtonian parameter $\\gamma$ values are $\\gamma_{\\rm TeV}-\\gamma_{\\rm keV}0.8$ TeV light curves of PKS 2155-304, a much more severe constraint on $\\gamma$ differences of $\\sim10^{-6}$ can be achieved, although the energy difference is of order of $\\sim$ TeV. Furthermore, we can combine these limits on the energy dependence of $\\gamma$ with the bound on the absolute $\\gamma$ value $\\gamma-1\\sim0.3\\%$ from light deflection measurements at the optical (eV) bands, and conclude that this absolute bound on $\\gamma$ can be extended from optical to TeV energies.

  11. The low-frequency radio emission in blazar PKS2155-304

    CERN Document Server

    Pandey-Pommier, M; Chadwick, P; Martin, J -M; Colom, P; van Driel, W; Combes, F; Kharb, P; Crespeau, P-J; Richard, J; Guiderdoni, B

    2016-01-01

    We report radio imaging and monitoring observations in the frequency range 0.235 - 2.7 GHz during the flaring mode of PKS 2155-304, one of the brightest BL Lac objects. The high sensitivity GMRT observations not only reveal extended kpc-scale jet and FRI type lobe morphology in this erstwhile `extended-core' blazar but also delineate the morphological details, thanks to its arcsec scale resolution. The radio light curve during the end phase of the outburst measured in 2008 shows high variability (8.5%) in the jet emission in the GHz range, compared to the lower core variability (3.2%) seen at the lowest frequencies. The excess of flux density with a very steep spectral index in the MHz range supports the presence of extra diffuse emission at low frequencies. The analysis of multi wavelength (radio/ optical/ gamma-ray) light curves at different radio frequencies confirms the variability of the core region and agrees with the scenario of high energy emission in gamma-rays due to inverse Compton emission from a ...

  12. Hadronic models of blazars require a change of the accretion paradigm

    CERN Document Server

    Zdziarski, Andrzej A

    2015-01-01

    We study hadronic models of broad-band emission of jets in radio-loud active galactic nuclei, and their implications for the accretion in those sources. We show that the models that account for broad-band spectra of blazars emitting in the GeV range in the sample of Boettcher et al. have highly super-Eddington jet powers. Furthermore, the ratio of the jet power to the radiative luminosity of the accretion disc is ~3000 on average and can be as high as ~10^5. We then show that the measurements of the radio core shift for the sample imply low magnetic fluxes threading the black hole, which rules out the Blandford-Znajek mechanism to produce powerful jets. These results require that the accretion rate necessary to power the modelled jets is extremely high, and the average radiative accretion efficiency is ~4 10^-5. Thus, if the hadronic model is correct, the currently prevailing picture of accretion in AGNs needs to be significantly revised. Also, the obtained accretion mode cannot be dominant during the lifetim...

  13. Locating the gamma-ray emission site in Fermi/LAT blazars. II Multifrequency correlations

    CERN Document Server

    Ramakrishnan, V; Tornikoski, M; Nilsson, K; Lindfors, E; Baloković, M; Lähteenmäki, A; Reinthal, R; Takalo, L

    2016-01-01

    In an attempt to constrain and understand the emission mechanism of gamma rays, we perform a cross-correlation analysis of 15 blazars using light curves in millimetre, optical and gamma rays. We use discrete correlation function and consider only correlations significant at 99 per cent level. A strong correlation was found between 37 and 95 GHz with a near-zero time delay in most of the sources, and ~1 month or longer in the rest. A similar result was obtained between the optical and gamma-ray bands. Of the 15 sources, less than 50 per cent showed a strong correlation between the millimetre and gamma-ray or millimetre and optical bands. The primary reason for the lack of statistically significant correlation is the absence of a major outburst in the millimetre bands of most of the sources during the 2.5 yr time period investigated in our study. This may indicate that only the long-term variations or large flares are correlated between these bands. The variability of the sources at every waveband was also insp...

  14. Awakening of The High Redshift Blazar CGRaBS J0809+5341

    CERN Document Server

    Paliya, Vaidehi S; Stalin, C S; Fabian, A C; Ramya, S; Covino, S; Tagliaferri, G; Sahayanathan, S; Ravikumar, C D

    2015-01-01

    CGRaBS J0809+5341, a high redshift blazar at z = 2.144, underwent a giant optical outburst on 2014 April 19 when it brightened by $\\sim$5 mag and reached an unfiltered apparent magnitude of 15.7 mag. This implies an absolute magnitude of -30.5 mag, making it one of the brightest quasars in the Universe. This optical flaring triggered us to carry out observations during the decaying part of the flare covering a wide energy range using the {\\it Nuclear Spectroscopic Telescope Array}, {\\it Swift}, and ground based optical facilities. For the first time, the source is detected in $\\gamma$-rays by the Large Area Telescope onboard the {\\it Fermi Gamma-Ray Space Telescope}. A high optical polarization of $\\sim$10\\% is also observed. Using the Sloan Digital Sky Survey spectrum, accretion disk luminosity and black hole mass are estimated as $1.5 \\times 10^{45}$ erg s$^{-1}$ and $10^{8.4}~M_{\\odot}$ respectively. Using a single zone leptonic emission model, we reproduce the spectral energy distribution of the source du...

  15. Gamma-ray opacity of the anisotropic stratified broad-line regions in blazars

    CERN Document Server

    Abolmasov, Pavel

    2016-01-01

    The GeV-range spectra of blazars are shaped not only by non-thermal emission processes internal to the relativistic jet but also by external pair-production absorption on the thermal emission of the accretion disc and the broad-line region (BLR). For the first time, we compute here the pair-production opacities in the GeV range produced by a realistic BLR accounting for the radial stratification and radiation anisotropy. Using photoionization modelling with the CLOUDY code, we calculate a series of BLR models of different sizes, geometries, cloud densities, column densities and metallicities. The strongest emission features in the model BLR are Ly$\\alpha$ and HeII Ly$\\alpha$. Contribution of recombination continua is smaller, especially for hydrogen, because Ly continuum is efficiently trapped inside the large optical depth BLR clouds and converted to Lyman emission lines and higher-order recombination continua. The largest effects on the gamma-ray opacity are produced by the BLR geometry and localization of ...

  16. ASCA and other contemporaneous observations of the blazar B2 1308+326

    CERN Document Server

    Watson, D; Hanlon, L O; McBreen, B; Quilligan, F; Tashiro, M; Metcalfe, L; Doyle, P G; Teraesranta, H; Carramiñana, A; Guichard, J P

    2000-01-01

    The high redshift (z=0.997) blazar B2 1308+326 was observed contemporaneously at x-ray, optical and radio wavelengths in June 1996. The x-ray observations were performed with ASCA. The ASCA results were found to be consistent with reanalysed data from two earlier ROSAT observations. The combined ASCA and ROSAT data reveal an x-ray spectrum that is best fit by a broken power law with absorber model. The break in the x-ray spectrum is interpreted, to be the emerging importance of inverse Compton (IC) emission which dominates the ASCA spectrum. The faint optical state reported for these observations (m_V=18.3+/-0.25) is incompatible with the high synchrotron flux previously detected by ROSAT. The IC emission detected by both ROSAT and ASCA was not significantly affected by the large change in the synchrotron component. MgII emission was detected with an equivalent width (EW) significantly different from previously reported values. Absorption at a level of in excess of the Galactic value was detected, indicating ...

  17. Long-Term Multiwavelength Studies of High-Redshift Blazar 0836+710

    CERN Document Server

    Akyuz, A; Donato, D; Perkins, J S; Fuhrmann, L; Angelakis, E; Zensus, J A; Larsson, S; Sokolovsky, K; Kurtanidze, O

    2013-01-01

    Aims. The observation of gamma -ray flares from blazar 0836+710 in 2011, following a period of quiescence, offered an opportunity to study correlated activity at different wavelengths for a high-redshift (z=2.218) active galactic nucleus. Methods. Optical and radio monitoring, plus Fermi-LAT gamma-ray monitoring provided 2008-2012 coverage, while Swift offered auxiliary optical, ultraviolet, and X-ray information. Other contemporaneous observations were used to construct a broad-band spectral energy distribution. Results. There is evidence of correlation but not a measurable lag between the optical and gamma-ray flaring emission. On the contrary, there is no clear correlation between radio and gamma-ray activity, indicating radio emission regions that are unrelated to the parts of the jet that produce the gamma-rays. The gamma-ray energy spectrum is unusual in showing a change of shape from a power law to a curved spectrum when going from the quiescent state to the active state.

  18. Multiwavelength Observations of a Dramatic High Energy Flare in the Blazar 3C 279

    CERN Document Server

    Wehrle, A E; Urry, C M; Maraschi, L; Ghisellini, G; Hartman, R C

    1997-01-01

    The blazar 3C 279, one of the brightest identified extragalactic objects in the gamma-ray sky, underwent a flare of a factor 10 amplitude in gamma-rays towards the end of a 3-week pointing by CGRO, in 1996 January-February. The flare peak represents the highest gamma-ray intensity ever recorded for this object. During the high state, extremely rapid gamma-ray variability was seen. Coordinated multifrequency observations were carried out with RXTE, ASCA, ROSAT and IUE and from many ground-based observatories, covering most accessible wavelengths. The well-sampled, simultaneous RXTE light curve shows an outburst of lower amplitude (factor of ~3) well correlated with the gamma-ray flare without any apparent lag. The optical-UV light curves, which are not well sampled during the high energy flare, exhibit more modest variations (factor of ~2) and a lower degree of correlation. The flux at millimetric wavelengths was near an historical maximum during the gamma-ray flare peak, with suggestion of a correlated decay....

  19. A FAST FLARE AND DIRECT REDSHIFT CONSTRAINT IN FAR-ULTRAVIOLET SPECTRA OF THE BLAZAR S5 0716+714

    International Nuclear Information System (INIS)

    The BL Lacertae object S5 0716+714 is one of the most studied blazars on the sky due to its active variability and brightness in many bands, including very-high-energy gamma rays. We present here two serendipitous results from recent far-ultraviolet spectroscopic observations by the Cosmic Origins Spectrograph onboard the Hubble Space Telescope (HST). First, during the course of our 7.3 hr HST observations, the blazar increased in flux rapidly by ∼40% (–0.45 mag hr–1) followed by a slower decline (+0.36 mag hr–1) to previous FUV flux levels. We model this flare using asymmetric flare templates and constrain the physical size and energetics of the emitting region. Furthermore, the spectral index of the object softens considerably during the course of the flare from αν ≈ –1.0 to αν ≈ –1.4. Second, we constrain the source redshift directly using the ∼30 intervening absorption systems. A system at z = 0.2315 is detected in Lyα, Lyβ, O VI, and N V and defines the lower bound on the source redshift. No absorbers are seen in the remaining spectral coverage (0.2315 Lyα ∼< 0.47) and we set a statistical upper bound of z < 0.322 (95% confidence) on the blazar. This is the first direct redshift limit for this object and is consistent with literature estimates of z = 0.31 ± 0.08 based on the detection of a host galaxy.

  20. Optical Spectroscopic Observations of γ-Ray Blazar Candidates. III. The 2013/2014 Campaign in the Southern Hemisphere

    Science.gov (United States)

    Landoni, M.; Massaro, F.; Paggi, A.; D'Abrusco, R.; Milisavljevic, D.; Masetti, N.; Smith, H. A.; Tosti, G.; Chomiuk, L.; Strader, J.; Cheung, C. C.

    2015-05-01

    We report the results of our exploratory program carried out with the southern Astrophysical Research telescope aimed at associating counterparts and establishing the nature of the Fermi Unidentified γ-ray Sources (UGSs). We selected the optical counterparts of six UGSs from the Fermi catalog on the basis of our recently discovered tight connection between infrared and γ-ray emission found for the γ-ray blazars detected by the Wide-Field Infrared Survey Explorer in its all-sky survey. We perform for the first time a spectroscopic study of the low-energy counterparts of the Fermi UGSs, in the optical band, confirming the blazar-like nature of the whole sample. We also present new spectroscopic observations of six active galaxies of uncertain type associated with Fermi sources which appear to be BL Lac objects. Finally, we report the spectra collected for six known γ-ray blazars belonging to the Roma BZCAT that were obtained to establish their nature or better estimate their redshifts. Two interesting cases of high redshift and extremely luminous BL Lac objects (z ≥ 1.18 and z ≥ 1.02, based on the detection of Mg ii intervening systems) are also discussed. Based on observations obtained at the southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação (MCTI) da República Federativa do Brasil, the U.S. National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).

  1. Exceptional outburst of the blazar CTA 102 in 2012: the GASP-WEBT campaign and its extension

    Science.gov (United States)

    Larionov, V. M.; Villata, M.; Raiteri, C. M.; Jorstad, S. G.; Marscher, A. P.; Agudo, I.; Smith, P. S.; Acosta-Pulido, J. A.; ˙arévalo, M. J.; Arkharov, A. A.; Bachev, R.; Blinov, D. A.; Borisov, G.; Borman, G. A.; Bozhilov, V.; Bueno, A.; Carnerero, M. I.; Carosati, D.; Casadio, C.; Chen, W. P.; Clemens, D. P.; Di Paola, A.; Ehgamberdiev, Sh. A.; Gómez, J. L.; González-Morales, P. A.; Griñón-Marín, A.; Grishina, T. S.; Hagen-Thorn, V. A.; Ibryamov, S.; Itoh, R.; Joshi, M.; Kopatskaya, E. N.; Koptelova, E.; Lázaro, C.; Larionova, E. G.; Larionova, L. V.; Manilla-Robles, A.; Metodieva, Y.; Milanova, Yu. V.; Mirzaqulov, D. O.; Molina, S. N.; Morozova, D. A.; Nazarov, S. V.; Ovcharov, E.; Peneva, S.; Ros, J. A.; Sadun, A. C.; Savchenko, S. S.; Semkov, E.; Sergeev, S. G.; Strigachev, A.; Troitskaya, Yu. V.; Troitsky, I. S.

    2016-09-01

    After several years of quiescence, the blazar CTA 102 underwent an exceptional outburst in 2012 September-October. The flare was tracked from γ-ray to near-infrared (NIR) frequencies, including Fermi and Swift data as well as photometric and polarimetric data from several observatories. An intensive Glast-Agile support programme of the Whole Earth Blazar Telescope (GASP-WEBT) collaboration campaign in optical and NIR bands, with an addition of previously unpublished archival data and extension through fall 2015, allows comparison of this outburst with the previous activity period of this blazar in 2004-2005. We find remarkable similarity between the optical and γ-ray behaviour of CTA 102 during the outburst, with a time lag between the two light curves of ≈1 h, indicative of cospatiality of the optical and γ-ray emission regions. The relation between the γ-ray and optical fluxes is consistent with the synchrotron self-Compton (SSC) mechanism, with a quadratic dependence of the SSC γ-ray flux on the synchrotron optical flux evident in the post-outburst stage. However, the γ-ray/optical relationship is linear during the outburst; we attribute this to changes in the Doppler factor. A strong harder-when-brighter spectral dependence is seen both the in γ-ray and optical non-thermal emission. This hardening can be explained by convexity of the UV-NIR spectrum that moves to higher frequencies owing to an increased Doppler shift as the viewing angle decreases during the outburst stage. The overall pattern of Stokes parameter variations agrees with a model of a radiating blob or shock wave that moves along a helical path down the jet.

  2. Evidence for quasi-periodic oscillations in the optical polarization of the blazar PKS 2155-304

    Science.gov (United States)

    Pekeur, N. W.; Taylor, A. R.; Potter, S. B.; Kraan-Korteweg, R. C.

    2016-10-01

    Evidence for the presence of quasi-periodic oscillations (QPOs) in the optical polarization of the blazar PKS 2155-304, during a period of enhanced gamma-ray brightness, is presented. The periodogram of the polarized flux revealed the existence of a prominent peak at T ˜ 13 min, detected at >99.7 per cent significance, and T ˜ 30 min, which was nominally significant at >99 per cent. This is the first evidence of QPOs in the polarization of an active galactic nucleus, potentially opening up a new avenue of studying this phenomenon.

  3. Equipartition gamma-ray blazars and the location of the gamma-ray emission site in 3C 279

    Energy Technology Data Exchange (ETDEWEB)

    Dermer, Charles D. [Code 7653, Space Science Division, U.S. Naval Research Laboratory, Washington, DC 20375 (United States); Cerruti, Matteo [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Lott, Benoit [Centre d' Études Nucléaires Bordeaux Gradignan, Université de Bordeaux, CNRS/IN2P3, UMR 5797, F-33175 Gradignan (France); Boisson, Catherine; Zech, Andreas, E-mail: charles.dermer@nrl.navy.mil, E-mail: matteo.cerruti@cfa.harvard.edu [Laboratoire Univers et THeories (LUTH), Observatoire de Paris-Meudon, 5 Place Jules Janssen, F-92195 Meudon Cedex (France)

    2014-02-20

    Blazar spectral models generally have numerous unconstrained parameters, leading to ambiguous values for physical properties like Doppler factor δ{sub D} or fluid magnetic field B'. To help remedy this problem, a few modifications of the standard leptonic blazar jet scenario are considered. First, a log-parabola function for the electron distribution is used. Second, analytic expressions relating energy loss and kinematics to blazar luminosity and variability, written in terms of equipartition parameters, imply δ{sub D}, B', and the peak electron Lorentz factor γ{sub pk}{sup ′}. The external radiation field in a blazar is approximated by Lyα radiation from the broad-line region (BLR) and ≈0.1 eV infrared radiation from a dusty torus. When used to model 3C 279 spectral energy distributions from 2008 and 2009 reported by Hayashida et al., we derive δ{sub D} ∼ 20-30, B' ∼ few G, and total (IR + BLR) external radiation field energy densities u ∼ 10{sup –2}-10{sup –3} erg cm{sup –3}, implying an origin of the γ-ray emission site in 3C 279 at the outer edges of the BLR. This is consistent with the γ-ray emission site being located at a distance R ≲ Γ{sup 2} ct {sub var} ∼ 0.1(Γ/30){sup 2}(t {sub var}/10{sup 4} s) pc from the black hole powering 3C 279's jets, where t {sub var} is the variability timescale of the radiation in the source frame, and at farther distances for narrow-jet and magnetic-reconnection models. Excess ≳ 5 GeV γ-ray emission observed with Fermi LAT from 3C 279 challenges the model, opening the possibility of a second leptonic component or a hadronic origin of the emission. For low hadronic content, absolute jet powers of ≈10% of the Eddington luminosity are calculated.

  4. Evidence for quasi-periodic oscillations in the optical polarization of the blazar PKS 2155-304

    CERN Document Server

    Pekeur, N W; Potter, S B; Kraan-Korteweg, R C

    2016-01-01

    Evidence for the presence of quasi-periodic oscillations (QPOs) in the optical polarization of the blazar PKS 2155-304, during a period of enhanced gamma-ray brightness, is presented. The periodogram of the polarized flux revealed the existence of a prominent peak at $T\\sim 13$ min, detected at >99.7% significance, and $T\\sim 30$ min, which was nominally significant at >99%. This is the first evidence of QPOs in the polarization of an active galactic nucleus, potentially opening up a new avenue of studying this phenomenon.

  5. Through the Ring of Fire: A Study of the Origin of Orphan Gamma-ray Flares in Blazars

    Science.gov (United States)

    MacDonald, Nicholas R.; Marscher, Alan P.; Jorstad, Svetlana G.; Joshi, Manasvita

    2014-06-01

    Blazars exhibit flares across the electromagnetic spectrum. Many gamma-ray flares are highly correlated with flares detected at optical wavelengths; however, a small subset appear to occur in isolation, with no counterpart in the other wave bands. These "orphan" gamma-ray flares challenge current models of blazar variability, most of which are unable to reproduce this type of behavior. We present numerical calculations of the time variable emission of a blazar based on a proposal by Marscher et al. (2010) to explain such events. In this model, a plasmoid ("blob") consisting of a power-law distribution of electrons propagates relativistically along the spine of a blazar jet and passes through a synchrotron emitting ring of electrons representing a shocked portion of the jet sheath. This ring supplies a source of seed photons that are inverse-Compton scattered by the electrons in the moving blob. As the blob approaches the ring, the photon density in the co-moving frame of the plasma increases, resulting in an orphan gamma-ray flare that then dissipates as the blob passes through and then moves away from the ring. The model includes the effects of radiative cooling and a spatially varying magnetic field. Support for the plausibility of this model is provided by observations by Marscher et al.(2010) of an isolated gamma-ray flare that was correlated with the passage of a superluminal knot through the inner jet of quasar PKS 1510-089. Synthetic light-curves produced by this new model are compared to the observed light-curves from this event. In addition, we present polarimetric observations that point to the existence of a jet sheath in the quasar 3C 273. A rough estimate of the bolometric luminosity of the sheath results in a value of ~10^45 erg s^-1 10% of the jet luminosity). This inferred sheath luminosity indicates that the jet sheath in 3C 273 can provide a significant source of seed photons that need to be taken into account when modeling the non

  6. Does the gamma-ray flux of the blazar 3C 454.3 vary on sub-hour timescales?

    OpenAIRE

    Foschini, L.; Tagliaferri, G.; Ghisellini, G.; Ghirlanda, G.; Tavecchio, F.; Bonnoli, G.

    2010-01-01

    In the early days of April 2010, the blazar 3C 454.3 (z=0.859) underwent a strong gamma-ray outburst, reaching fluxes (E > 100 MeV) in excess of 10^-5 ph cm^-2 s^-1. The Fermi Gamma ray Space Telescope performed a 200 ks long pointed observation starting from 5 April 2010 19:38 UTC. This allowed us to try probing the variability of the gamma-ray emission on timescales of hours or less. We found the variability on a few hours timescale. On sub-hour timescale we found no evidence of significant...

  7. Relativistic Pair Beams from TeV Blazars: A Source of Reprocessed GeV Emission rather than Intergalactic Heating

    Science.gov (United States)

    Sironi, Lorenzo; Giannios, Dimitrios

    2014-05-01

    The interaction of TeV photons from blazars with the extragalactic background light produces a relativistic beam of electron-positron pairs streaming through the intergalactic medium (IGM). The fate of the beam energy is uncertain. By means of two- and three-dimensional particle-in-cell simulations, we study the nonlinear evolution of dilute ultra-relativistic pair beams propagating through the IGM. We explore a wide range of beam Lorentz factors γ b Gt 1 and beam-to-plasma density ratios α Lt 1, so that our results can be extrapolated to the extreme parameters of blazar-induced beams (γ b ~ 106 and α ~ 10-15, for powerful blazars). For cold beams, we show that the oblique instability governs the early stages of evolution, but its exponential growth terminates—due to self-heating of the beam in the transverse direction—when only a negligible fraction ~(α/γ b )1/3 ~ 10-7 of the beam energy has been transferred to the IGM plasma. Further relaxation of the beam proceeds through quasi-longitudinal modes, until the momentum dispersion in the direction of propagation saturates at Δp b, ∥/γ b mec ~ 0.2. This corresponds to a fraction ~10% of the beam energy—irrespective of γ b or α—being ultimately transferred to the IGM plasma (as compared to the heating efficiency of ~50% predicted by one-dimensional models, which cannot properly account for the transverse broadening of the beam). For the warm beams generated by TeV blazars, the development of the longitudinal relaxation is suppressed, since the initial dispersion in beam momentum is already Δp b0, ∥/γ b mec >~ 1. Here, the fraction of beam energy ultimately deposited into the IGM is only ~α γ b ~ 10-9. It follows that most of the beam energy is still available to power the GeV emission produced by inverse Compton up-scattering of the cosmic microwave background by the beam pairs.

  8. MOJAVE. XII. ACCELERATION AND COLLIMATION OF BLAZAR JETS ON PARSEC SCALES

    Energy Technology Data Exchange (ETDEWEB)

    Homan, D. C. [Department of Physics, Denison University, Granville, OH 43023 (United States); Lister, M. L.; Richards, J. L. [Department of Physics, Purdue University, 525 Northwestern Avenue, West Lafayette, IN 47907 (United States); Kovalev, Y. Y. [Astro Space Center of Lebedev Physical Institute, Profsoyuznaya 84/32, 117997 Moscow (Russian Federation); Pushkarev, A. B.; Savolainen, T.; Ros, E. [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Kellermann, K. I., E-mail: homand@denison.edu [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States)

    2015-01-10

    We report on the acceleration properties of 329 features in 95 blazar jets from the MOJAVE Very Long Baseline Array program. Nearly half the features and three-quarters of the jets show significant changes in speed and/or direction. In general, apparent speed changes are distinctly larger than changes in direction, indicating that changes in the Lorentz factors of jet features dominate the observed speed changes rather than bends along the line of sight. Observed accelerations tend to increase the speed of features near the jet base, ≲ 10-20 pc projected, and decrease their speed at longer distances. The range of apparent speeds at a fixed distance in an individual jet can span a factor of a few, indicating that shock properties and geometry may influence the apparent motions; however, we suggest that the broad trend of jet features increasing their speed near the origin is due to an overall acceleration of the jet flow out to deprojected distances of the order of 10{sup 2} pc, beyond which the flow begins to decelerate or remains nearly constant in speed. We estimate intrinsic rates of change of the Lorentz factors in the galaxy frame of the order of Γ-dot /Γ≃10{sup −3} to 10{sup –2} yr{sup –1}, which can lead to total Lorentz factor changes of a factor of a few on the length scales observed here. Finally, we also find evidence for jet collimation at projected distances of ≲ 10 pc in the form of the non-radial motion and bending accelerations that tend to better align features with the inner jet.

  9. Science with the ASTRI mini-array for the Cherenkov Telescope Array: blazars and fundamental physics

    Science.gov (United States)

    Bonnoli, Giacomo; Tavecchio, Fabrizio; Giuliani, Andrea; Bigongiari, Ciro; Di Pierro, Federico; Stamerra, Antonio; Pareschi, Giovanni; Vercellone, Stefano; ASTRI Collaboration; CTA Consortium

    2016-05-01

    ASTRI (“Astronomia a Specchi con Tecnologia Replicante Italiana”) is a flagship project of the Italian Ministry of Research (MIUR), devoted to the realization, operation and scientific validation of an end-to-end prototype for the Small Size Telescope (SST) envisaged to become part of the Cherenkov Telescope Array (CTA). The ASTRI SST-2M telescope prototype is characterized by a dual mirror, Schwarzschild-Couder optical design and a compact camera based on silicon photo-multipliers. It will be sensitive to multi-TeV very high energy (VHE) gamma rays up to 100 TeV, with a PSF ~ 6’ and a wide (9.6°) unaberrated optical field of view. Right after validation of the design in single-dish observations at the Serra La Nave site (Sicily, Italy) during 2015, the ASTRI collaboration will be able to start deployment, at the final CTA southern site, of the ASTRI mini-array, proposed to constitute the very first CTA precursor. Counting 9 ASTRI SST-2M telescopes, the ASTRI mini-array will overtake current IACT systems in differential sensitivity above 5 TeV, thus allowing unprecedented observations of known and predicted bright TeV emitters in this band, including some extragalactic sources such as extreme high-peaked BL Lacs with hard spectra. We exploited the ASTRI scientific simulator ASTRIsim in order to understand the feasibility of observations tackling blazar and cosmic ray physics, including discrimination of hadronic and leptonic scenarios for the VHE emission from BL Lac relativistic jets and indirect measurements of the intergalactic magnetic field and of the extragalactic background light. We selected favorable targets, outlining observation modes, exposure times, multi-wavelength coverage needed and the results expected. Moreover, the perspectives for observation of effects due to the existence of axion-like particles or to Lorentz invariance violations have been investigated.

  10. Very Long Baseline Polarimetric monitoring at 15 GHz of the TeV blazar Markarian 421

    Science.gov (United States)

    Lico, R.; Casadio, C.; Gómez, J. L.; Giroletti, M.; Orienti, M.; Giovannini, G.; Blasi, M. G.; Cotton, W.; Edwards, P. G.; Fuhrmann, L.; Jorstad, S.; Kino, M.; Kovalev, Y. Y.; Krichbaum, T. P.; Marscher, A.; Paneque, D.; Perez-Torres, M. A.; Piner, G.; Sokolovsky, K. V.

    2013-12-01

    Thanks to high resolution radio observations it is possible to obtain a direct imaging of the innermost regions of Active Galactic Nuclei; in particular, it is possible to investigate about the jet's morphology and any proper motions, and the time evolution of physical parameters, such as flux densities and spectral index. Furthermore, with the study of the polarization properties, it is possible to obtain important information about the magnetic field structure and the emission mechanisms. In this work we present recent results about the nearby (z=0.031) TeV blazar Mrk 421. We analyzed data obtained with the Very Long Baseline Array (VLBA),both in total and polarized intensity, at twelve epochs (one observation per month from January to December 2011) at 15, 24 and 43 GHz, in the context of a broadband campaign from the radio to gamma-ray. We investigate the inner jet structure on parsec scale through the study of model-fit components for each epoch. At these frequencies the source shows a compact (about 0.13 mas, or 0.08 pc) and bright component, with a one sided jet detected out to about 10 mas. All model-fit components in the jet appear to be almost stationary during our observation period, and the spectral index is fairly flat in the core region and steepens along the jet's length. In particular, we present a preliminary study of the polarization properties for the 15 GHz dataset: we found a degree of polarization of ˜ 1% for the core region and for the C3 component, at near 1 mas from the core, we found a value of near 14%.

  11. Exploring the blazar zone in high-energy flares of FSRQs

    Energy Technology Data Exchange (ETDEWEB)

    Pacciani, L.; Donnarumma, I. [INAF-Istituto di Astrofisica e Planetologia Spaziale, Via Fosso del Cavaliere 100, I-00133 Rome (Italy); Tavecchio, F. [INAF-Osservatorio Astronomico di Brera, via E. Bianchi 46, I-23807 Merate (Italy); Stamerra, A. [INAF-Osservatorio Astrofisico di Torino, via P. Giuria 1, I-10125 Torino (Italy); Carrasco, L.; Recillas, E.; Porras, A. [Instituto Nacional de Astrofisica, Optica y Electronica, Mexico, Luis E, Erro 1, Sta. Maria Tonantzintla, Puebla, CP 72840 (Mexico); Uemura, M., E-mail: luigi.pacciani@iaps.inaf.it [Hiroshima Astrophysical Science Center, Hiroshima University 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526 (Japan)

    2014-07-20

    The gamma-ray emission offers a powerful diagnostic tool to probe jets and their surroundings in flat-spectrum radio quasars (FSRQs). In particular, sources emitting at high energies (>10 GeV) give us the strongest constraints. This motivates us to start a systematic study of flares with bright emission above 10 GeV, examining archival data of the Fermi-LAT gamma-ray telescope. At the same time, we began to trigger Target of Opportunity observations to the Swift observatory at the occurrence of high-energy flares, obtaining a wide coverage of the spectral energy distributions (SEDs) for several FSRQs during flares. Among others, we investigate the SED of a peculiar flare of 3C 454.3, showing a remarkably hard gamma-ray spectrum, quite different from the brightest flares of this source, and a bright flare of CTA 102. We modeled the SED in the framework of the one-zone leptonic model, using also archival optical spectroscopic data to derive the luminosity of the broad lines and thus estimate the disk luminosity, from which the structural parameters of the FSRQ nucleus can be inferred. The model allowed us to evaluate the magnetic field intensity in the blazar zone and to locate the emitting region of gamma-rays in the particular case in which gamma-ray spectra show neither absorption from the broad-line region (BLR) nor the Klein-Nishina curvature expected in leptonic models assuming the BLR as the source of seed photons for the External Compton scenario. For FSRQs bright above 10 GeV, we were able to identify short periods lasting less than one day characterized by a high rate of high-energy gamma-rays and hard gamma-ray spectra. We discussed the observed spectra and variability timescales in terms of injection and cooling of energetic particles, arguing that these flares could be triggered by magnetic reconnection events or turbulence in the flow.

  12. Gamma-ray opacity of the anisotropic stratified broad-line regions in blazars

    Science.gov (United States)

    Abolmasov, Pavel; Poutanen, Juri

    2016-09-01

    The GeV-range spectra of blazars are shaped not only by non-thermal emission processes internal to the relativistic jet but also by external pair-production absorption on the thermal emission of the accretion disc and the broad-line region (BLR). For the first time, we compute here the pair-production opacities in the GeV range produced by a realistic BLR accounting for the radial stratification and radiation anisotropy. Using photoionization modelling with the CLOUDY code, we calculate a series of BLR models of different sizes, geometries, cloud densities, column densities and metallicities. The strongest emission features in the model BLR are Lyα and He II Lyα. Contribution of recombination continua is smaller, especially for hydrogen, because Ly continuum is efficiently trapped inside the large optical depth BLR clouds and converted to Lyman emission lines and higher-order recombination continua. The largest effects on the gamma-ray opacity are produced by the BLR geometry and localization of the gamma-ray source. We show that when the gamma-ray source moves further from the central source, all the absorption details move to higher energies and the overall level of absorption drops because of decreasing incidence angles between the gamma-rays and BLR photons. The observed positions of the spectral breaks can be used to measure the geometry and the location of the gamma-ray emitting region relative to the BLR. Strong dependence on geometry means that the soft photons dominating the pair-production opacity may be actually produced by a different population of BLR clouds than the bulk of the observed broad line emission.

  13. Polarization angle swings in blazars: The case of 3C 279

    Science.gov (United States)

    Kiehlmann, S.; Savolainen, T.; Jorstad, S. G.; Sokolovsky, K. V.; Schinzel, F. K.; Marscher, A. P.; Larionov, V. M.; Agudo, I.; Akitaya, H.; Benítez, E.; Berdyugin, A.; Blinov, D. A.; Bochkarev, N. G.; Borman, G. A.; Burenkov, A. N.; Casadio, C.; Doroshenko, V. T.; Efimova, N. V.; Fukazawa, Y.; Gómez, J. L.; Grishina, T. S.; Hagen-Thorn, V. A.; Heidt, J.; Hiriart, D.; Itoh, R.; Joshi, M.; Kawabata, K. S.; Kimeridze, G. N.; Kopatskaya, E. N.; Korobtsev, I. V.; Krajci, T.; Kurtanidze, O. M.; Kurtanidze, S. O.; Larionova, E. G.; Larionova, L. V.; Lindfors, E.; López, J. M.; McHardy, I. M.; Molina, S. N.; Moritani, Y.; Morozova, D. A.; Nazarov, S. V.; Nikolashvili, M. G.; Nilsson, K.; Pulatova, N. G.; Reinthal, R.; Sadun, A.; Sasada, M.; Savchenko, S. S.; Sergeev, S. G.; Sigua, L. A.; Smith, P. S.; Sorcia, M.; Spiridonova, O. I.; Takaki, K.; Takalo, L. O.; Taylor, B.; Troitsky, I. S.; Uemura, M.; Ugolkova, L. S.; Ui, T.; Yoshida, M.; Zensus, J. A.; Zhdanova, V. E.

    2016-05-01

    Context. Over the past few years, on several occasions, large, continuous rotations of the electric vector position angle (EVPA) of linearly polarized optical emission from blazars have been reported. These events are often coincident with high energy γ-ray flares and they have attracted considerable attention, since they could allow us to probe the magnetic field structure in the γ-ray emitting region of the jet. The flat-spectrum radio quasar 3C 279 is one of the most prominent examples showing this behaviour. Aims: Our goal is to study the observed EVPA rotations and to distinguish between a stochastic and a deterministic origin of the polarization variability. Methods: We have combined multiple data sets of R-band photometry and optical polarimetry measurements of 3C 279, yielding exceptionally well-sampled flux density and polarization curves that cover a period of 2008-2012. Several large EVPA rotations are identified in the data. We introduce a quantitative measure for the EVPA curve smoothness, which is then used to test a set of simple random walk polarization variability models against the data. Results: 3C 279 shows different polarization variation characteristics during an optical low-flux state and a flaring state. The polarization variation during the flaring state, especially the smooth ~360° rotation of the EVPA in mid-2011, is not consistent with the tested stochastic processes. Conclusions: We conclude that, during the two different optical flux states, two different processes govern polarization variation, which is possibly a stochastic process during the low-brightness state and a deterministic process during the flaring activity. The measured and processed optical polarization and R-band photometry data are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/590/A10

  14. Multi-frequency properties of synthetic blazar radio light curves within the shock-in-jet scenario

    CERN Document Server

    Fromm, C M; Perucho, M

    2014-01-01

    Blazars are among the most powerful extragalactic objects, as a sub-class of active galactic nuclei. They launch relativistic jets and their emitted radiation shows strong variability across the entire electro-magnetic spectrum. The mechanisms producing the variability are still controversial and different models have been proposed to explain the observed variations in multi-frequency blazar light curves.We investigate the capabilities of the classical shock-in-jet model to explain and reconstruct the observed evolution of flares in the turnover frequency turnover flux density plane and their frequency-dependent light curve parameters. With a detailed parameter space study we provide the framework for future, detailed comparisons of observed flare signatures with the shock-in-jet scenario. Based on the shock model we compute synthetic single-dish light curves at different radio frequencies (2.6 to 345 GHz) and for different physical conditions in a conical jet (e.g. magnetic field geometry and Doppler factor)...

  15. Frequency-dependent time delays for strong outbursts in four blazars from the Metsahovi and UMRAO monitoring databases

    CERN Document Server

    Pyatunina, T B; Gabuzda, D C; Jorstad, S G; Aller, M F; Aller, H D; Terasranta, H

    2006-01-01

    The combined data of the University of Michigan Radio Astronomy Observatory and Metsahovi Radio Observatory provide us with radio light curves for Active Galactic Nuclei monitored by both observatories from 4.8 to 37 GHz covering time intervals up to ~25 years. We consider here such composite light curves for four gamma-ray blazars that have been nearly continuously monitored at both observatories: 0458-020, 0528+134, 1730-130 and 2230+114. We have decomposed the most prominent outbursts in the light curves of these four blazars into individual components using Gaussian model fitting, and estimated the epochs, amplitudes, and half-widths of these components as functions of frequency. We attempt to distinguish "core outbursts", which show frequency-dependent time delays and are associated with brightening of the core, from "jet outbursts", which appear nearly synchronously at all frequencies and are accompanied by the emergence of new jet components and their subsequent evolution. Available 43 GHz VLBA images ...

  16. Nine years of multi-frequency monitoring of the blazar PKS 0048-097: spectral and temporal variability

    CERN Document Server

    Wierzcholska, Alicja

    2016-01-01

    Blazars are highly variable, radio-loud active galactic nuclei with jets oriented at a small angle to the line of sight. The observed emission of these sources covers the whole electromagnetic spectrum from radio frequencies up to the high or even very high energy gamma-ray range. To understand the complex physics of these objects, multi-wavelength observations and studies on the variability and correlations between different wavelengths are therefore essential. The long-term multi-frequency observations of PKS 0048-097 are analysed here to investigate its spectral and temporal features. The studies includes nine years of observations of the blazar, which is well studied in the optical and radio domain, but not in the other frequencies. Multi-wavelength data collected with OVRO, KAIT, Catalina, Swift/UVOT, Swift/XRT and Fermi/LAT were studied. The performed analysis revealed strong variability in all wavelengths that is most clearly manifested in the X-ray range. The correlation studies do not exhibit any rel...

  17. MULTI-WAVELENGTH OBSERVATIONS OF BLAZAR AO 0235+164 IN THE 2008-2009 FLARING STATE

    Energy Technology Data Exchange (ETDEWEB)

    Ackermann, M. [Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen (Germany); Ajello, M.; Blandford, R. D.; Bloom, E. D.; Borgland, A. W.; Bottacini, E.; Buehler, R.; Cameron, R. A. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Ballet, J.; Casandjian, J. M. [Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d' Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D.; Buson, S. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bellazzini, R.; Bregeon, J. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Bonamente, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Brigida, M. [Dipartimento di Fisica ' M. Merlin' dell' Universita e del Politecnico di Bari, I-70126 Bari (Italy); Bruel, P. [Laboratoire Leprince-Ringuet, Ecole polytechnique, CNRS/IN2P3, Palaiseau (France); Caliandro, G. A. [Institut de Ciencies de l' Espai (IEEE-CSIC), Campus UAB, 08193 Barcelona (Spain); Caraveo, P. A., E-mail: eduardo@slac.stanford.edu, E-mail: madejski@slac.stanford.edu, E-mail: fabio.gargano@ba.infn.it, E-mail: silvia.raino@ba.infn.it, E-mail: lreyes04@calpoly.edu, E-mail: knalew@colorado.edu, E-mail: sikora@camk.edu.pl [INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica, I-20133 Milano (Italy); Collaboration: Fermi-LAT Collaboration; GASP-WEBT consortium; F-GAMMA; Iram-PdBI; Kanata; RXTE; SMARTS; Swift-XRT; and others

    2012-06-01

    The blazar AO 0235+164 (z = 0.94) has been one of the most active objects observed by Fermi Large Area Telescope (LAT) since its launch in Summer 2008. In addition to the continuous coverage by Fermi, contemporaneous observations were carried out from the radio to {gamma}-ray bands between 2008 September and 2009 February. In this paper, we summarize the rich multi-wavelength data collected during the campaign (including F-GAMMA, GASP-WEBT, Kanata, OVRO, RXTE, SMARTS, Swift, and other instruments), examine the cross-correlation between the light curves measured in the different energy bands, and interpret the resulting spectral energy distributions in the context of well-known blazar emission models. We find that the {gamma}-ray activity is well correlated with a series of near-IR/optical flares, accompanied by an increase in the optical polarization degree. On the other hand, the X-ray light curve shows a distinct 20 day high state of unusually soft spectrum, which does not match the extrapolation of the optical/UV synchrotron spectrum. We tentatively interpret this feature as the bulk Compton emission by cold electrons contained in the jet, which requires an accretion disk corona with an effective covering factor of 19% at a distance of 100 R{sub g}. We model the broadband spectra with a leptonic model with external radiation dominated by the infrared emission from the dusty torus.

  18. MULTI-WAVELENGTH OBSERVATIONS OF BLAZAR AO 0235+164 IN THE 2008-2009 FLARING STATE

    International Nuclear Information System (INIS)

    The blazar AO 0235+164 (z = 0.94) has been one of the most active objects observed by Fermi Large Area Telescope (LAT) since its launch in Summer 2008. In addition to the continuous coverage by Fermi, contemporaneous observations were carried out from the radio to γ-ray bands between 2008 September and 2009 February. In this paper, we summarize the rich multi-wavelength data collected during the campaign (including F-GAMMA, GASP-WEBT, Kanata, OVRO, RXTE, SMARTS, Swift, and other instruments), examine the cross-correlation between the light curves measured in the different energy bands, and interpret the resulting spectral energy distributions in the context of well-known blazar emission models. We find that the γ-ray activity is well correlated with a series of near-IR/optical flares, accompanied by an increase in the optical polarization degree. On the other hand, the X-ray light curve shows a distinct 20 day high state of unusually soft spectrum, which does not match the extrapolation of the optical/UV synchrotron spectrum. We tentatively interpret this feature as the bulk Compton emission by cold electrons contained in the jet, which requires an accretion disk corona with an effective covering factor of 19% at a distance of 100 Rg. We model the broadband spectra with a leptonic model with external radiation dominated by the infrared emission from the dusty torus.

  19. Exceptional outburst of the blazar CTA 102 in 2012: The GASP-WEBT campaign and its extension

    CERN Document Server

    Larionov, V M; Raiteri, C M; Jorstad, S G; Marscher, A P; Agudo, I; Smith, P S; Acosta-Pulido, J A; Arévalo, M J; Arkharov, A A; Bachev, R; Blinov, D A; Borisov, G; Borman, G A; Bozhilov, V; Bueno, A; Carnerero, M I; Carosati, D; Casadio, C; Chen, W P; Clemens, D P; Di Paola, A; Ehgamberdiev, Sh A; Gómez, J L; González-Morales, P A; Griñón-Marín, A; Grishina, T S; Hagen-Thorn, V A; Ibryamov, S; Itoh, R; Kopatskaya, E N; Koptelova, E; Lázaro, C; Larionova, E G; Larionova, L V; Manilla-Robles, A; Metodieva, Y; Milanova, Yu V; Mirzaqulov, D O; Molina, S N; Morozova, D A; Nazarov, S V; Ovcharov, E; Peneva, S; Ros, J A; Sadun, A C; Savchenko, S S; Semkov, E; Sergeev, S G; Strigachev, A; Troitskaya, Yu V; Troitsky, I S

    2016-01-01

    After several years of quiescence, the blazar CTA 102 underwent an exceptional outburst in 2012 September-October. The flare was tracked from gamma-ray to near-infrared frequencies, including Fermi and Swift data as well as photometric and polarimetric data from several observatories. An intensive GASP-WEBT collaboration campaign in optical and NIR bands, with an addition of previously unpublished archival data and extension through fall 2015, allows comparison of this outburst with the previous activity period of this blazar in 2004-2005. We find remarkable similarity between the optical and gamma-ray behaviour of CTA 102 during the outburst, with a time lag between the two light curves of ~1 hour, indicative of co-spatiality of the optical and gamma-ray emission regions. The relation between the gamma-ray and optical fluxes is consistent with the SSC mechanism, with a quadratic dependence of the SSC gamma-ray flux on the synchrotron optical flux evident in the post-outburst stage. However, the gamma-ray/opt...

  20. MAGIC long-term study of the distant TeV blazar PKS 1424+240 in a multiwavelength context

    CERN Document Server

    Aleksić, J; Antonelli, L A; Antoranz, P; Babic, A; Bangale, P; de Almeida, U Barres; Barrio, J A; González, J Becerra; Bednarek, W; Bernardini, E; Biland, A; Blanch, O; Bonnefoy, S; Bonnoli, G; Borracci, F; Bretz, T; Carmona, E; Carosi, A; Fidalgo, D Carreto; Colin, P; Colombo, E; Contreras, J L; Cortina, J; Covino, S; Da Vela, P; Dazzi, F; De Angelis, A; De Caneva, G; De Lotto, B; Mendez, C Delgado; Doert, M; Domínguez, A; Prester, D Dominis; Dorner, D; Doro, M; Einecke, S; Eisenacher, D; Elsaesser, D; Farina, E; Ferenc, D; Fonseca, M V; Font, L; Frantzen, K; Fruck, C; López, R J García; Garczarczyk, M; Terrats, D Garrido; Gaug, M; Godinović, N; Muñoz, A González; Gozzini, S R; Hadasch, D; Hayashida, M; Herrera, J; Herrero, A; Hildebrand, D; Hose, J; Hrupec, D; Idec, W; Kadenius, V; Kellermann, H; Kodani, K; Konno, Y; Krause, J; Kubo, H; Kushida, J; La Barbera, A; Lelas, D; Lewandowska, N; Lindfors, E; Lombardi, S; López, M; López-Coto, R; López-Oramas, A; Lorenz, E; Lozano, I; Makariev, M; Mallot, K; Maneva, G; Mankuzhiyil, N; Mannheim, K; Maraschi, L; Marcote, B; Mariotti, M; Martínez, M; Mazin, D; Menzel, U; Meucci, M; Miranda, J M; Mirzoyan, R; Moralejo, A; Munar-Adrover, P; Nakajima, D; Niedzwiecki, A; Nilsson, K; Nishijima, K; Noda, K; Nowak, N; Orito, R; Overkemping, A; Paiano, S; Palatiello, M; Paneque, D; Paoletti, R; Paredes, J M; Paredes-Fortuny, X; Partini, S; Persic, M; Prada, F; Moroni, P G Prada; Prandini, E; Preziuso, S; Puljak, I; Reinthal, R; Rhode, W; Ribó, M; Rico, J; Garcia, J Rodriguez; Rügamer, S; Saggion, A; Saito, T; Saito, K; Satalecka, K; Scalzotto, V; Scapin, V; Schultz, C; Schweizer, T; Shore, S N; Sillanpää, A; Sitarek, J; Snidaric, I; Sobczynska, D; Spanier, F; Stamatescu, V; Stamerra, A; Steinbring, T; Storz, J; Sun, S; Surić, T; Takalo, L; Takami, H; Tavecchio, F; Temnikov, P; Terzić, T; Tescaro, D; Teshima, M; Thaele, J; Tibolla, O; Torres, D F; Toyama, T; Treves, A; Uellenbeck, M; Vogler, P; Wagner, R M; Zandanel, F; Zanin, R; Cutini, S; Gasparrini, D; Furniss, A; Hovatta, T; Kangas, T; Kankare, E; Kotilainen, J; Lister, M; Lähteenmäki, A; Max-Moerbeck, W; Pavlidou, V; Readhead, A; Richards, J

    2014-01-01

    Aims. We present a study of the very high energy (VHE; E>100 GeV) gamma-ray emission of the blazar PKS 1424+240 observed with the MAGIC telescopes. The primary aim of this paper is the multiwavelength spectral characterization and modeling of this blazar, made particularly interesting by the recent discovery of a lower limit of its redshift of z>0.6, which makes it a promising candidate to be the most distant VHE source. Methods. The source has been observed with the MAGIC telescopes in VHE gamma rays for a total observation time of 33.6 h from 2009 to 2011. Results. The source was marginally detected in VHE gamma rays during 2009 and 2010 and later the detection was confirmed during an optical outburst in 2011. The combined significance of the stacked sample is 7.2 sigma. The differential spectra measured during the different campaigns can be described by steep power laws, with the indices ranging from 3.5+/-1.2 to 5.0+/-1.7. The MAGIC spectra corrected for the absorption due to the extragalactic background ...

  1. Multi-wavelength observations of blazar AO 0235+164 in the 2008-2009 flaring state

    CERN Document Server

    Ackermann, M; Ballet, J; Barbiellini, G; Bastieri, D; Bellazzini, R; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Bottacini, E; Bregeon, J; Brigida, M; Bruel, P; Buehler, R; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Cavazzuti, E; Cecchi, C; Charles, E; Chekhtman, A; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Cutini, S; D'Ammando, F; de Palma, F; Dermer, C D; Silva, E do Couto e; Drell, P S; Drlica-Wagner, A; Dubois, R; Favuzzi, C; Fegan, S J; Ferrara, E C; Focke, W B; Fortin, P; Fuhrmann, L; Fukazawa, Y; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giglietto, N; Giommi, P; Giordano, F; Giroletti, M; Glanzman, T; Godfrey, G; Grenier, I A; Guiriec, S; Hadasch, D; Hayashida, M; Hughes, R E; Itoh, R; Johannesson, G; Johnson, A S; Katagiri, H; Kataoka, J; Knodlseder, J; Kuss, M; Lande, J; Larsson, S; Lee, S -H; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Mazziotta, M N; McEnery, J E; Mehault, J; Michelson, P F; Mitthumsiri, W; Mizuno, T; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Naumann-Godo, M; Nishino, S; Norris, J P; Nuss, E; Ohsugi, T; Okumura, A; Omodei, N; Orlando, E; Ozaki, M; Paneque, D; Panetta, J H; Pelassa, V; Pesce-Rollins, M; Pierbattista, M; Piron, F; Pivato, G; Porter, T A; Raino, S; Rando, R; Rastawicki, D; Razzano, M; Readhead, A; Reimer, A; Reimer, O; Reyes, L C; Richards, J L; Sbarra, C; Sgro, C; Siskind, E J; Spandre, G; Spinelli, P; Szostek, A; Takahashi, H; Tanaka, T; Thayer, J G; Thayer, J B; Thompson, D J; Tinivella, M; Torres, D F; Tosti, G; Troja, E; Usher, T L; Vandenbroucke, J; Vasileiou, V; Vianello, G; Vitale, V; Waite, A P; Winer, B L; Wood, K S; Yang, Z; Zimmer, S; Moderski, R; Nalewajko, K; Sikora, M; Villata, M; Raiteri, C M; Aller, H D; Aller, M F; Arkharov, A A; Benitez, E; Berdyugin, A; Blinov, D A; Boettcher, M; Calle, O J A Bravo; Buemi, C S; Carosati, D; Chen, W P; Diltz, C; Di Paola, A; Dolci, M; Efimova, N V; Forn\\', E; Gurwell, M A; Heidt, J; Hiriart, D; Jordan, B; Kimeridze, G; Konstantinova, T S; Kopatskaya, E N; Koptelova, E; Kurtanidze, O M; Lahteenmaki, A; Larionova, E G; Larionova, L V; Larionov, V M; Leto, P; Lindfors, E; Lin, H C; Morozova, D A; Nikolashvili, M G; Nilsson, K; Oksman, M; Roustazadeh, P; Sievers, A; Sigua, L A; Sillanpaa, A; Takahashi, T; Takalo, L O; Tornikoski, M; Trigilio, C; Troitsky, I S; Umana, G; Angelakis, E; Krichbaum, T P; Nestoras, I; Riquelme, D; Krips, M; Trippe, S; Arai, A; Kawabata, K S; Sakimoto, K; Sasada, M; Sato, S; Uemura, M; Yamanaka, M; Yoshida, M; Belloni, T; Tagliaferri, G; Bonning, E W; Isler, J; Urry, C M; Hoversten, E; Falcone, A; Pagani, C; Stroh, M

    2012-01-01

    The blazar AO 0235+164 (z = 0.94) has been one of the most active objects observed by Fermi Large Area Telescope (LAT) since its launch in Summer 2008. In addition to the continuous coverage by Fermi, contemporaneous observations were carried out from the radio to {\\gamma} -ray bands between 2008 September and 2009 February. In this paper, we summarize the rich multi-wavelength data collected during the campaign (including F-GAMMA, GASP- WEBT, Kanata, OVRO, RXTE, SMARTS, Swift, and other instruments), examine the cross-correlation between the light curves measured in the different energy bands, and interpret the resulting spectral energy distributions in the context of well-known blazar emission models. We find that the {\\gamma} -ray activity is well correlated with a series of near-IR/optical flares, accompanied by an increase in the optical polarization degree. On the other hand, the X-ray light curve shows a distinct 20 day high state of unusually soft spectrum, which does not match the extrapolation of th...

  2. The Cosmological Impact of Luminous TeV Blazars II: Rewriting the Thermal History of the Intergalactic Medium

    CERN Document Server

    ,

    2011-01-01

    The Universe is opaque to extragalactic very high-energy gamma rays (VHEGRs, E>100 GeV) because they annihilate and pair produce on the extragalactic background light. The resulting ultra-relativistic pairs are assumed to lose energy through inverse Compton scattering of CMB photons. In Broderick et al. (2011, Paper I of this three paper series), we argued that instead powerful plasma instabilities in the ultra-relativistic pair beam dissipate the kinetic energy of the TeV-generated pairs locally, heating the intergalactic medium (IGM). Here, we explore the effect of this heating upon the thermal history of the IGM. We collate the observed extragalactic VHEGR sources to determine a local VHEGR heating rate and correct for the pointed nature of VHEGR observations using Fermi observations of high and intermediate peaked BL Lacs. Because the local extragalactic VHEGR flux is dominated by TeV blazars, we tie the TeV blazar luminosity density to the quasar luminosity density, and produce a VHEGR heating rate as a ...

  3. NuSTAR DETECTION OF THE BLAZAR B2 1023+25 AT REDSHIFT 5.3

    Energy Technology Data Exchange (ETDEWEB)

    Sbarrato, T. [Dipartimento di Scienza e Alta Tecnologia, Università dell' Insubria, Via Valleggio 11, I-22100 Como (Italy); Tagliaferri, G.; Ghisellini, G. [INAF-Osservatorio Astronomico di Brera, via E. Bianchi 46, I-23807 Merate (Italy); Perri, M.; Puccetti, S.; Giommi, P. [ASI-Science Data Center, via Galileo Galilei, I-00044 Frascati (Italy); Baloković, M.; Harrison, F. A.; Hovatta, T. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Nardini, M. [Dipartimento di Fisica G. Occhialini, Università di Milano Bicocca, Piazza della Scienza 3, I-20126 Milano (Italy); Stern, D. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Boggs, S. E. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Brandt, W. N. [Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Christensen, F. E. [DTU Space-National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark); Greiner, J.; Rau, A.; Schady, P.; Sudilovsky, V. [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching (Germany); Hailey, C. J. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Madejski, G. M., E-mail: tullia.sbarrato@brera.inaf.it [Kavli Institute for Particle Astrophysics and Cosmology, SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); and others

    2013-11-10

    B2 1023+25 is an extremely radio-loud quasar at z = 5.3 that was first identified as a likely high-redshift blazar candidate in the SDSS+FIRST quasar catalog. Here, we use the Nuclear Spectroscopic Telescope Array (NuSTAR) to investigate its non-thermal jet emission, whose high-energy component we detected in the hard X-ray energy band. The X-ray flux is ∼ 5.5 x 10{sup -14} erg cm{sup -2} s{sup -1} (5-10 keV) and the photon spectral index is Γ{sub X} ≅ 1.3-1.6. Modeling the full spectral energy distribution, we find that the jet is oriented close to the line of sight, with a viewing angle of ∼3°, and has significant Doppler boosting, with a large bulk Lorentz factor ∼13, which confirms the identification of B2 1023+25 as a blazar. B2 1023+25 is the first object at redshift larger than 5 detected by NuSTAR, demonstrating the ability of NuSTAR to investigate the early X-ray universe and to study extremely active supermassive black holes located at very high redshift.

  4. The observed radio/gamma-ray emission correlation for blazars with the Fermi-LAT and the RATAN-600 data

    CERN Document Server

    Mufakharov, T; Sotnikova, Yu; Naiden, Ya; Erkenov, A

    2015-01-01

    We study the correlation between gamma-ray and radio band radiation for 123 blazars, using the Fermi-LAT first source catalog (1FGL) and the RATAN-600 data obtained at the same period of time (within a few months). We found an apparent positive correlation for BL Lac and flat-spectrum radio quasar (FSRQ) sources from our sample through testing the value of the Pearson product-moment correlation coefficient. The BL Lac objects show higher values of the correlation coefficient than FSRQs at all frequencies, except 21.7 GHz, and at all bands, except $10-100$ GeV, typically at high confidence level (> 99%). At higher gamma-ray energies the correlation weakens and even becomes negative for BL Lacs and FSRQs. For BL Lac blazars, the correlation of the fluxes appeared to be more sensitive to the considered gamma-ray energy band, than to the frequency, while for FSRQ sources the correlation changed notably both with the considered radio frequency and gamma-ray energy band. We used a data randomization method to quant...

  5. Searches for very high energy gamma rays from blazars with CANGAROO-III telescope in 2005-2009

    CERN Document Server

    Mizumura, Y; Nishijima, K; Bicknell, G V; Clay, R W; Edwards, P G; Gunji, S; Hara, S; Hayashi, S; Kabuki, S; Kajino, F; Kawachi, A; Kifune, T; Kiuchi, R; Kodani, K; Matsubara, Y; Mizukami, T; Mizumoto, Y; Mori, M; Muraishi, H; Naito, T; Ohishi, M; Yoshida, T; Yoshikoshi, T

    2012-01-01

    We have searched for very high energy (VHE) gamma rays from four blazars using the CANGAROO-III imaging atmospheric Cherenkov telescope. We report the results of the observations of H 2356-309, PKS 2155-304, PKS 0537-441, and 3C 279, performed from 2005 to 2009, applying a new analysis to suppress the effects of the position dependence of Cherenkov images in the field of view. No significant VHE gamma ray emission was detected from any of the four blazars. The GeV gamma-ray spectra of these objects were obtained by analyzing Fermi/LAT archival data. Non-simultaneous wide range (radio to VHE gamma-ray bands) spectral energy distributions (SEDs) including CANGAROO-III upper limits, GeV gamma-ray spectra, and archival data are discussed using a one-zone synchrotron self-Compton (SSC) model in combination with a external Compton (EC) radiation. The HBLs (H 2356-309 and PKS 2155-304) can be explained by a simple SSC model, and PKS 0537-441 and 3C 279 are well modeled by a combination of SSC and EC model. We find a...

  6. Gamma-Ray and Parsec-Scale Jet Properties of a Complete Sample of Blazars From the MOJAVE Program

    CERN Document Server

    Lister, M L; Aller, H; Hovatta, T; Kellermann, K I; Kovalev, Y Y; Meyer, E T; Pushkarev, A B; Ros, E; Ackermann, M; Antolini, E; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Bechtol, K; Bellazzini, R; Berenji, B; Blandford, R D; Bloom, E D; Boeck, M; Bonamente, E; Borgland, A W; Bregeon, J; Brigida, M; Bruel, P; Buehler, R; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Cavazzuti, E; Cecchi, C; Chang, C S; Charles, E; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; Cutini, S; de Palma, F; Dermer, C D; Silva, E do Couto e; Drell, P S; Drlica-Wagner, A; Favuzzi, C; Fegan, S J; Ferrara, E C; Finke, J; Focke, W B; Fortin, P; Fukazawa, Y; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giglietto, N; Giordano, F; Giroletti, M; Glanzman, T; Godfrey, G; Grenier, I A; Guiriec, S; Hadasch, D; Hayashida, M; Hays, E; Horan, D; Hughes, R E; Jóhannesson, G; Johnson, A S; Kadler, M; Katagiri, H; Kataoka, J; Knödlseder, J; Kuss, M; Lande, J; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Mazziotta, M N; McConville, W; McEnery, J E; Mehault, J; Michelson, P F; Mizuno, T; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Naumann-Godo, M; Nishino, S; Nolan, P L; Norris, J P; Nuss, E; Ohno, M; Ohsugi, T; Okumura, A; Omodei, N; Orlando, E; Ozaki, M; Paneque, D; Parent, D; Pesce-Rollins, M; Pierbattista, M; Piron, F; Pivato, G; Rainò, S; Readhead, A; Reimer, A; Reimer, O; Richards, J L; Ritz, S; Sadrozinski, H F -W; Sgrò, C; Shaw, M S; Siskind, E J; Spandre, G; Spinelli, P; Takahashi, H; Tanaka, T; Thayer, J G; Thayer, J B; Thompson, D J; Tosti, G; Tramacere, A; Troja, E; Usher, T L; Vandenbroucke, J; Vasileiou, V; Vianello, G; Vitale, V; Waite, A P; Wang, P; Winer, B L; Wood, K S; Zimmer, S

    2011-01-01

    We investigate the Fermi LAT gamma-ray and 15 GHz VLBA radio properties of a joint gamma-ray- and radio-selected sample of AGNs obtained during the first 11 months of the Fermi mission (2008 Aug 4 - 2009 Jul 5). Our sample contains the brightest 173 AGNs in these bands above declination -30 deg. during this period, and thus probes the full range of gamma-ray loudness (gamma-ray to radio band luminosity ratio) in the bright blazar population. The latter quantity spans at least four orders of magnitude, reflecting a wide range of spectral energy distribution (SED) parameters in the bright blazar population. The BL Lac objects, however, display a linear correlation of increasing gamma-ray loudness with synchrotron SED peak frequency, suggesting a universal SED shape for objects of this class. The synchrotron self-Compton model is favored for the gamma-ray emission in these BL Lacs over external seed photon models, since the latter predict a dependence of Compton dominance on Doppler factor that would destroy any...

  7. Exploring the multiband emission of TXS 0536+145: the most distant gamma-ray flaring blazar

    CERN Document Server

    Orienti, M; Giroletti, M; Finke, J; Ajello, M; Dallacasa, D; Venturi, T

    2014-01-01

    We report results of a multiband monitoring campaign of the flat spectrum radio quasar TXS 0536+145 at redshift 2.69. This source was detected during a very high gamma-ray activity state in 2012 March by the Large Area Telescope on board Fermi, becoming the gamma-ray flaring blazar at the highest redshift detected so far. At the peak of the flare the source reached an apparent isotropic gamma-ray luminosity of 6.6 x 10^49 erg/s which is comparable to the values achieved by the most luminous blazars. This activity triggered radio-to-X-rays monitoring observations by Swift, Very Long Baseline Array, European VLBI Network, and Medicina single-dish telescope. Significant variability was observed from radio to X-rays supporting the identification of the gamma-ray source with TXS 0536+145. Both the radio and gamma-ray light curves show a similar behaviour, with the gamma-rays leading the radio variability with a time lag of about 4-6 months. The luminosity increase is associated with a flattening of the radio spect...

  8. NuSTAR Detection of the Blazar B2 1023+25 at Redshift 5.3

    Science.gov (United States)

    Sbarrato, T.; Tagliaferri, G.; Ghisellini, G.; Perri, M.; Puccetti, S.; Balokovic, M.; Nardini, M.; Stern, D.; Boggs, S. E.; Brandt, W. N.; Christensen, F. E.; Giommi, P.; Greiner, J.; Hailey, C. J.; Harrison, F. A.; Hovatta, T.; Madejski, G. M.; Rau, A.; Schady, P.; Sudilovsky, V.; Urry, C. M.; Zhang, William W.

    2013-01-01

    B2 1023+25 is an extremely radio-loud quasar at zeta = 5.3 that was first identified as a likely high-redshift blazar candidate in the SDSS+FIRST quasar catalog. Here, we use the Nuclear Spectroscopic Telescope Array (NuSTAR) to investigate its non-thermal jet emission, whose high-energy component we detected in the hard X-ray energy band. The X-ray flux is approximately 5.5 × 10 (exp -14) erg cm(exp -2) s(exp -1) (5-10 keV) and the photon spectral index is Gamma(x) approx. =1.3-1.6. Modeling the full spectral energy distribution, we find that the jet is oriented close to the line of sight, with a viewing angle of approximately 3deg, and has significant Doppler boosting, with a large bulk Lorentz factor approximately 13, which confirms the identification of B2 1023+25 as a blazar. B2 1023+25 is the first object at redshift larger than 5 detected by NuSTAR, demonstrating the ability of NuSTAR to investigate the early X-ray universe and to study extremely active supermassive black holes located at very high redshift.

  9. NuSTAR detection of the blazar B2 1023+25 at redshift 5.3

    CERN Document Server

    Sbarrato, T; Ghisellini, G; Perri, M; Puccetti, S; Balokovic, M; Nardini, M; Stern, D; Boggs, S E; Brandt, W N; Chirstensen, F E; Giommi, P; Greiner, J; Hailey, C J; Harrison, F; Hovatta, T; Madejski, G M; Rau, A; Schady, P; Sudilovsky, V; Urry, C M; Zhang, W W

    2013-01-01

    B2 1023+25 is an extremely radio-loud quasar at z=5.3 which was first identified as a likely high-redshift blazar candidate in the SDSS+FIRST quasar catalog. Here we use the Nuclear Spectroscopic Telescope Array (NuSTAR) to investigate its non-thermal jet emission, whose high-energy component we detected in the hard X-ray energy band. The X-ray flux is ~5.5x10^(-14) erg cm^(-2)s^(-1) (5-10keV) and the photon spectral index is Gamma_X=1.3-1.6. Modeling the full spectral energy distribution, we find that the jet is oriented close to the line of sight, with a viewing angle of ~3deg, and has significant Doppler boosting, with a large bulk Lorentz factor ~13, which confirms the identification of B2 1023+25 as a blazar. B2 1023+25 is the first object at redshift larger than 5 detected by NuSTAR, demonstrating the ability of NuSTAR to investigate the early X-ray Universe and to study extremely active supermassive black holes located at very high redshift.

  10. SDSS J114657.79+403708.6: the third most distant blazar at z=5.0

    CERN Document Server

    Ghisellini, G; Tagliaferri, G; Foschini, L; Tavecchio, F; Ghirlanda, G; Braito, V; Gehrels, N

    2014-01-01

    The radio-loud quasar SDSS J114657.79+403708.6 at a redshift z=5.0 is one of the most distant radio-loud objects. The IR-optical luminosity and spectrum suggest that its black hole has a very large mass: M=(5+-1)x 1e9 Msun. The radio-loudness (ratio of the radio to optical flux) of the source is large (around 100), suggesting that the source is viewed at small angles from the jet axis, and could be a blazar. The X-ray observations fully confirm this hypothesis, due to the high level and hardness of the flux. This makes SDSS J114657.79+403708.6 the third most distant blazar known, after Q0906+693 (z=5.47) and B2 1023+25 (z=5.3). Among those, SDSS J114657.79+403708.6 has the largest black hole mass, setting interesting constraints on the mass function of heavy (larger than one billion solar masses) black holes at high redshifts.

  11. Fermi LAT detection of extraordinary variability in the gamma-ray emission of the blazar PKS 1510-089

    CERN Document Server

    Foschini, L; Ghisellini, G; Tagliaferri, G; Tavecchio, F; Stamerra, A

    2013-01-01

    We have reanalysed the giant outburst of the blazar PKS 1510-089 (z=0.36) occurred on 2011 October-November. The gamma-ray flux in the 0.1-100 GeV energy range exceeded the value of 10^-5 ph/cm2/s for several days. The peak flux was reached on 2011 October 19, with a value of 4.4 x 10^-5 ph/cm2/s, which in turn corresponds to a luminosity of 2 x 10^49 erg/s. Very short time scale variability was measured. Particularly, on 2011 October 18, the flux doubling time was as small as 20 minutes. This is the shortest variability ever detected in the MeV-GeV energy band. We compared the present analysis with two other outbursts observed in 2009 March and 2012 February-March, when the blazar was detected also by HESS and MAGIC, respectively, in order to infer information about the emission at hundreds of GeV.

  12. SDSS J102623.61+254259.5: the second most distant blazar at z=5.3

    CERN Document Server

    Sbarrato, T; Nardini, M; Tagliaferri, G; Foschini, L; Ghirlanda, G; Tavecchio, F; Greiner, J; Rau, A; Gehrels, N

    2012-01-01

    The radio-loud quasar SDSS J102623.61+254259.5, at a redshift z=5.3, is one of the most distant radio-loud objects. Since its radio flux exceeds 100 mJy at a few GHz, it is also one of the most powerful radio-loud sources. We propose that this source is a blazar, i.e. we are seeing its jet at a small viewing angle. This claim is based on the spectral energy distribution of this source, and especially on its strong and hard X-ray spectrum, as seen by Swift, very typical of powerful blazars. Observations by the Gamma-Ray Burst Optical/Near-Infrared Detector (GROND) and by theWide-field Infrared Survey Explorer (WISE) allow to establish the thermal nature of the emission in the near IR-optical band. Assuming that this is produced by a standard accretion disk, we derive that it emits a luminosity of L_d \\simeq 9 \\times 10^46 erg s^{-1} and that the black hole has a mass between 2 and 5 billion solar masses. This poses interesting constraints on the mass function of heavy (> 10^9 M_sun) black holes at high redshif...

  13. NuSTAR DETECTION OF THE BLAZAR B2 1023+25 AT REDSHIFT 5.3

    International Nuclear Information System (INIS)

    B2 1023+25 is an extremely radio-loud quasar at z = 5.3 that was first identified as a likely high-redshift blazar candidate in the SDSS+FIRST quasar catalog. Here, we use the Nuclear Spectroscopic Telescope Array (NuSTAR) to investigate its non-thermal jet emission, whose high-energy component we detected in the hard X-ray energy band. The X-ray flux is ∼ 5.5 x 10-14 erg cm-2 s-1 (5-10 keV) and the photon spectral index is ΓX ≅ 1.3-1.6. Modeling the full spectral energy distribution, we find that the jet is oriented close to the line of sight, with a viewing angle of ∼3°, and has significant Doppler boosting, with a large bulk Lorentz factor ∼13, which confirms the identification of B2 1023+25 as a blazar. B2 1023+25 is the first object at redshift larger than 5 detected by NuSTAR, demonstrating the ability of NuSTAR to investigate the early X-ray universe and to study extremely active supermassive black holes located at very high redshift

  14. Resumen de tesis. La B(1,3)glucán sintasa Bgs1 es esencial en el control de la polaridad celular y la citocinesis de Schizosaccharomyces pombe

    OpenAIRE

    Ramos Vecino, Mariona

    2014-01-01

    [ES]El complejo enzimático de la beta(1,3)glucán sintasa de la levadura de fisión Schizosaccharomyces pombe está compuesta por una subunidad catalítica codificada por los genes de la familia Bgs. Bgs1 es esencial y es responsable de la síntesis del beta(1,3)glucano lineal que da lugar a la estructura del septo primario de división. En ausencia de Bgs1 las células presentan defectos en separación celular y en la selección del sitio de crecimiento polarizado. En este trabajo de tesis se pon...

  15. Model-fitting of the kinematics of superluminal components in blazar 3C 279

    Institute of Scientific and Technical Information of China (English)

    Shan-Jie Qian

    2012-01-01

    A precessing jet-nozzle model with a precession period of about 25 yr has been proposed by Qian to interpret the change with time of the ejection position angle of the superluminal components observed using very long baseline interferometry (VLBI) in the blazar 3C 279.We discuss the kinematic properties of six superluminal knots (C3,C4,C7a,C8,C9 and C10) and show that their trajectory,core-distance and apparent speed,derived from VLBI observations,can be consistently well fitted by the model.Their intrinsic Lorentz factors of bulk superluminal motion are thus derived,and the evidence shows no relation between Lorentz factor and the precession phase.Interestingly,for the C7a and C8 knots,the fitted core-distance ranges from ~0.1 mas to ~0.4mas and for knots C9 and C10 from ~0.2mas to ~1.0-1.5mas.For knot C4,its trajectory and apparent velocity are well fitted in the core-distance range from ~1 mas to ~5 mas,taking into account a curvature of the trajectory at core-distance larger than ~3 mas.The consistent fitting of the kinematics of these components clearly demonstrates that the amplitude function and collimation parameter adopted in the precession model are appropriate and applicable for both the inner and outer parts of the jet in 3C 279,but in some cases the jet curvature in the outer parts (or deviation from the model trajectory) needs to be seriously taken into consideration.With the exception of C4,the ejection position angles derived from the precession model are consistent with the values measured by VLBI observations (within about 3° - 6°).Undoubtedly,the consistent interpretation of the kinematics in terms of the precession model for these superluminal components,with their ejection time spanning ~24 yr,significantly expands its applicability and implies that regular pattems of trajectories (or rotating channels) could exist in some periods.

  16. AGILE detection of intense gamma-ray emission from the blazar PKS 1510-089

    Science.gov (United States)

    Pucella, G.; Vittorini, V.; D'Ammando, F.; Tavani, M.; Raiteri, C. M.; Villata, M.; Argan, A.; Barbiellini, G.; Boffelli, F.; Bulgarelli, A.; Caraveo, P.; Cattaneo, P. W.; Chen, A. W.; Cocco, V.; Costa, E.; Del Monte, E.; de Paris, G.; Di Cocco, G.; Donnarumma, I.; Evangelista, Y.; Feroci, M.; Fiorini, M.; Froysland, T.; Fuschino, F.; Galli, M.; Gianotti, F.; Giuliani, A.; Labanti, C.; Lapshov, I.; Lazzarotto, F.; Lipari, P.; Longo, F.; Marisaldi, M.; Mereghetti, S.; Morselli, A.; Pacciani, L.; Pellizzoni, A.; Perotti, F.; Picozza, P.; Prest, M.; Rapisarda, M.; Rappoldi, A.; Soffitta, P.; Trifoglio, M.; Trois, A.; Vallazza, E.; Vercellone, S.; Zambra, A.; Zanello, D.; Antonelli, L. A.; Colafrancesco, S.; Cutini, S.; Gasparrini, D.; Giommi, P.; Pittori, C.; Verrecchia, F.; Salotti, L.; Aller, M. F.; Aller, H. D.; Carosati, D.; Larionov, V. M.; Ligustri, R.

    2008-11-01

    Context: We report the detection by the AGILE (Astro-rivelatore Gamma a Immagini LEggero) satellite of an intense gamma-ray flare from the source AGL J1511-0909, associated with the powerful quasar PKS 1510-089, during ten days of observations from 23 August to 1 September 2007. Aims: During the observation period, the source was in optical decrease following a flaring event monitored by the GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT). The simultaneous gamma-ray, optical, and radio coverage allows us to study the spectral energy distribution and the theoretical models based on the synchrotron and inverse Compton (IC) emission mechanisms. Methods: AGILE observed the source with its two co-aligned imagers, the Gamma-Ray Imaging Detector and the hard X-ray imager Super-AGILE sensitive in the 30 MeV div 50 GeV and 18 div 60 keV bands, respectively. Results: Between 23 and 27 August 2007, AGILE detected gamma-ray emission from PKS 1510-089 when this source was located 50° off-axis, with an average flux of (270 ± 65) × 10-8 photons cm-2 s-1 for photon energy above 100 MeV. In the following period, 28 August-1 September, after a satellite re-pointing, AGILE detected the source at 35° off-axis, with an average flux (E > 100 MeV) of (195 ± 30) × 10-8 photons cm-2 s-1. No emission was detected by Super-AGILE, with a 3-σ upper limit of 45 mCrab in 200 ks. Conclusions: The spectral energy distribution is modelled with a homogeneous one-zone synchrotron self Compton (SSC) emission plus contributions by external photons: the SSC emission contributes primarily to the X-ray band, whereas the contribution of the IC from the external disc and the broad line region match the hard gamma-ray spectrum observed.

  17. Suzaku Observations of Luminous Quasars: Revealing the Nature of High-energy Blazar Emission in Low-level Activity States

    Science.gov (United States)

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Antolini, E.; Baldini, L.; Ballet, J.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Carrigan, S.; Casandjian, J. M.; Cavazzuti, E.; Cecchi, C.; Çelik, Ö.; Chekhtman, A.; Chen, A. W.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Colafrancesco, S.; Conrad, J.; Cutini, S.; Dermer, C. D.; de Palma, F.; Digel, S. W.; Silva, E. do Couto e.; Drell, P. S.; Dubois, R.; Dumora, D.; Farnier, C.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Focke, W. B.; Frailis, M.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Giebels, B.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grandi, P.; Grenier, I. A.; Guillemot, L.; Guiriec, S.; Hadasch, D.; Harding, A. K.; Hayashida, M.; Horan, D.; Hughes, R. E.; Itoh, R.; Jackson, M. S.; Jóhannesson, G.; Johnson, A. S.; Johnson, W. N.; Kamae, T.; Katagiri, H.; Kataoka, J.; Kawai, N.; Knödlseder, J.; Kuss, M.; Lande, J.; Latronico, L.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Madejski, G. M.; Makeev, A.; Mazziotta, M. N.; McEnery, J. E.; McGlynn, S.; Meurer, C.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nestoras, I.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Okumura, A.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paneque, D.; Panetta, J. H.; Parent, D.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Piron, F.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Reimer, A.; Reimer, O.; Reyes, L. C.; Rodriguez, A. Y.; Roth, M.; Ryde, F.; Sadrozinski, H. F.-W.; Sambruna, R.; Sander, A.; Sato, R.; Sgrò, C.; Shaw, M. S.; Siskind, E. J.; Smith, P. D.; Spandre, G.; Spinelli, P.; Stawarz, Ł.; Stecker, F. W.; Strickman, M. S.; Suson, D. J.; Takahashi, H.; Takahashi, T.; Tanaka, T.; Thayer, J. B.; Thayer, J. G.; Thompson, D. J.; Tibolla, O.; Torres, D. F.; Tosti, G.; Tramacere, A.; Uchiyama, Y.; Usher, T. L.; Vasileiou, V.; Vilchez, N.; Villata, M.; Vitale, V.; von Kienlin, A.; Waite, A. P.; Wang, P.; Winer, B. L.; Wood, K. S.; Yang, Z.; Ylinen, T.; Ziegler, M.; Tavecchio, F.; Sikora, M.; Schady, P.; Roming, P.; Chester, M. M.; Maraschi, L.

    2010-06-01

    We present the results from the Suzaku X-ray observations of five flat-spectrum radio quasars (FSRQs), namely PKS 0208-512, Q 0827+243, PKS 1127-145, PKS 1510-089, and 3C 454.3. All these sources were additionally monitored simultaneously or quasi-simultaneously by the Fermi satellite in gamma rays and the Swift UVOT in the UV and optical bands, respectively. We constructed their broadband spectra covering the frequency range from 1014 Hz up to 1025 Hz, and those reveal the nature of high-energy emission of luminous blazars in their low-activity states. The analyzed X-ray spectra are well fitted by a power-law model with photoelectric absorption. In the case of PKS 0208-512, PKS 1127-145, and 3C 454.3, the X-ray continuum showed indication of hardening at low energies. Moreover, when compared with the previous X-ray observations, we see a significantly increasing contribution of low-energy photons to the total X-ray fluxes when the sources are getting fainter. The same behavior can be noted in the Suzaku data alone. A likely explanation involves a variable, flat-spectrum component produced via inverse-Compton emission, plus an additional, possibly steady soft X-ray component prominent when the source gets fainter. This soft X-ray excess is represented either by a steep power-law (photon indices Γ ~ 3-5) or a blackbody-type emission with temperatures kT ~ 0.1-0.2 keV. We model the broadband spectra of the five observed FSRQs using synchrotron self-Compton and/or external-Compton radiation models. Our modeling suggests that the difference between the low- and high-activity states in luminous blazars is due to the different total kinetic power of the jet, most likely related to varying bulk Lorentz factor of the outflow within the blazar emission zone.

  18. Gamma-ray cosmology and fundamental physics with TeV blazars: results from 20 years of observations

    CERN Document Server

    Biteau, Jonathan

    2015-01-01

    Gamma rays from TeV blazars have been detected by ground-based experiments for more than two decades. We have collected the most extensive set of archival spectra from these sources in order to constrain the processes affecting gamma-ray propagation on cosmological distances. We discuss our results on the diffuse photon field that populates universe, called the extragalactic background light, on the expansion rate of the Universe, and on fundamental physics in the form of axion-like particles and Lorentz-invariance violation. Specifically, we present a spectrum of the extragalactic background light from 0.26 to 105 microns constructed from the gamma-ray observations, we measure a value of the Hubble constant compatible with other estimates, and we constrain the energy scale at which Lorentz-invariance violation impacts gamma-ray absorption by the extragalactic background light to be larger than sixty percent of the Planck scale.

  19. Inverse Compton light curves of blazars under non-linear, time-dependent synchrotron-self Compton cooling

    CERN Document Server

    Zacharias, Michael

    2014-01-01

    Blazars exhibit flares with a doubling time scale on the order of minutes. Such rapid flares are theoretically challenging and several {models} have been put forward to explain the fast variability. In this paper we continue the discussion concerning the effects of non-linear, time-dependent synchrotron self-Compton (SSC) cooling. In previous papers we were able to show that the non-linearity{, introduced by a time-dependent electron injection,} has severe consequences for both the spectral energy distribution (SED) and the monochromatic synchrotron light curve. The non-linear cooling introduces novel breaks in the SED, which are usually explained by complicated underlying electron distributions, while the much faster cooling of the SSC process {causes significant differences in the synchrotron light curves}. In this paper we calculate the inverse Compton light curves, taking into account both the SSC and the external Compton process. The light curves are calculated from the monochromatic intensities by intro...

  20. GeV Blazar flares several parsecs from the central engine. Who pays the seed photon bill?

    Science.gov (United States)

    Breiding, Peter; Georganopoulos, Markos; Meyer, Eileen

    2016-04-01

    In Blazars, multi-wavelength observations suggest that some GeV flares take place at the location of the mm VLBI core, several pc from the black hole. This location for the GeV emission requires a yet un-identified source of seed photons to be Inverse Compton scattered to GeV energies. Our model for these flares involves a fast spine and slow sheath configuration for the relativistic jet, where the mildly beamed sheath emission will illuminate with a large opening angle the outer regions of the Molecular Torus. The heated clouds will then radiate and their emission will be relativistically boosted in the spine frame where it can they be up-scattered to GeV energies. We argue, through analytical work and simulations, that this can be the seed photon source that produces the GeV flares.

  1. A Search for QPOs in the Blazar OJ287: Preliminary Results from the 2015/2016 Observing Campaign

    Directory of Open Access Journals (Sweden)

    S. Zola

    2016-10-01

    Full Text Available We analyse the light curve in the R band of the blazar OJ287, gathered during the 2015/2016 observing season. We did a search for quasi-periodic oscillations (QPOs using several methods over a wide range of timescales. No statistically significant periods were found in the high-frequency domain both in the ground-based data and in Kepler observations. In the longer-period domain, the Lomb–Scargle periodogram revealed several peaks above the 99% significance level. The longest one—about 95 days—corresponds to the innermost stable circular orbit (ISCO period of the more massive black hole. The 43-day period could be an alias, or it can be attributed to accretion in the form of a two-armed spiral wave.

  2. Multiwavelength Evidence for Quasi-periodic Modulation in the Gamma-Ray Blazar PG 1553+113

    Science.gov (United States)

    Ackermann, M.; Ajello, M.; Albert, A.; Atwood, W. B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Becerra Gonzalez, J.; Bellazzini, R.; Bissaldi, E.; Blandford, R. D.; Bloom, E. D.; Bonino, R.; Bottacini, E.; Bregeon, J.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caputo, R.; Caragiulo, M.; Caraveo, P. A.; Cavazzuti, E.; Cecchi, C.; Chekhtman, A.; Chiang, J.; Chiaro, G.; Ciprini, S.; Cohen-Tanugi, J.; Conrad, J.; Cutini, S.; D'Ammando, F.; de Angelis, A.; de Palma, F.; Desiante, R.; Di Venere, L.; D´nguez, A.; Drell, P. S.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Focke, W. B.; Fuhrmann, L.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Godfrey, G.; Green, D.; Grenier, I. A.; Grove, J. E.; Guiriec, S.; Harding, A. K.; Hays, E.; Hewitt, J. W.; Hill, A. B.; Horan, D.; Jogler, T.; Jóhannesson, G.; Johnson, A. S.; Kamae, T.; Kuss, M.; Larsson, S.; Latronico, L.; Li, J.; Li, L.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Magill, J.; Maldera, S.; Manfreda, A.; Max-Moerbeck, W.; Mayer, M.; Mazziotta, M. N.; McEnery, J. E.; Michelson, P. F.; Mizuno, T.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nuss, E.; Ohno, M.; Ohsugi, T.; Ojha, R.; Omodei, N.; Orlando, E.; Ormes, J. F.; Paneque, D.; Pearson, T. J.; Perkins, J. S.; Perri, M.; Pesce-Rollins, M.; Petrosian, V.; Piron, F.; Pivato, G.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Readhead, A.; Reimer, A.; Reimer, O.; Schulz, A.; Sgrò, C.; Siskind, E. J.; Spada, F.; Spandre, G.; Spinelli, P.; Suson, D. J.; Takahashi, H.; Thayer, J. B.; Thompson, D. J.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Troja, E.; Uchiyama, Y.; Vianello, G.; Wood, K. S.; Wood, M.; Zimmer, S.; Berdyugin, A.; Corbet, R. H. D.; Hovatta, T.; Lindfors, E.; Nilsson, K.; Reinthal, R.; Sillanpää, A.; Stamerra, A.; Takalo, L. O.; Valtonen, M. J.

    2015-11-01

    We report for the first time a γ-ray and multiwavelength nearly periodic oscillation in an active galactic nucleus. Using the Fermi Large Area Telescope we have discovered an apparent quasi-periodicity in the γ-ray flux (E > 100 MeV) from the GeV/TeV BL Lac object PG 1553+113. The marginal significance of the 2.18 ± 0.08 year period γ-ray cycle is strengthened by correlated oscillations observed in radio and optical fluxes, through data collected in the Owens Valley Radio Observatory, Tuorla, Katzman Automatic Imaging Telescope, and Catalina Sky Survey monitoring programs and Swift-UVOT. The optical cycle appearing in ˜10 years of data has a similar period, while the 15 GHz oscillation is less regular than seen in the other bands. Further long-term multiwavelength monitoring of this blazar may discriminate among the possible explanations for this quasi-periodicity.

  3. MULTIWAVELENGTH EVIDENCE FOR QUASI-PERIODIC MODULATION IN THE GAMMA-RAY BLAZAR PG 1553+113

    Energy Technology Data Exchange (ETDEWEB)

    Ackermann, M.; Buehler, R. [Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen (Germany); Ajello, M. [Department of Physics and Astronomy, Clemson University, Kinard Lab of Physics, Clemson, SC 29634-0978 (United States); Albert, A.; Baldini, L.; Blandford, R. D.; Bloom, E. D.; Bottacini, E.; Caliandro, G. A. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Atwood, W. B. [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Université Paris Diderot, Service d’Astrophysique, CEA Saclay, F-91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D.; Buson, S. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Becerra Gonzalez, J. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Bellazzini, R. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Bissaldi, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Bari, I-70126 Bari (Italy); Bonino, R. [Istituto Nazionale di Fisica Nucleare, Sezione di Torino, I-10125 Torino (Italy); Bregeon, J. [Laboratoire Univers et Particules de Montpellier, Université Montpellier, CNRS/IN2P3, Montpellier (France); Bruel, P., E-mail: David.J.Thompson@nasa.gov, E-mail: sara.cutini@asdc.asi.it, E-mail: stefano.ciprini@asdc.asi.it, E-mail: stefan@astro.su.se, E-mail: stamerra@oato.inaf.it [Laboratoire Leprince-Ringuet, École polytechnique, CNRS/IN2P3, Palaiseau (France); and others

    2015-11-10

    We report for the first time a γ-ray and multiwavelength nearly periodic oscillation in an active galactic nucleus. Using the Fermi Large Area Telescope we have discovered an apparent quasi-periodicity in the γ-ray flux (E > 100 MeV) from the GeV/TeV BL Lac object PG 1553+113. The marginal significance of the 2.18 ± 0.08 year period γ-ray cycle is strengthened by correlated oscillations observed in radio and optical fluxes, through data collected in the Owens Valley Radio Observatory, Tuorla, Katzman Automatic Imaging Telescope, and Catalina Sky Survey monitoring programs and Swift-UVOT. The optical cycle appearing in ∼10 years of data has a similar period, while the 15 GHz oscillation is less regular than seen in the other bands. Further long-term multiwavelength monitoring of this blazar may discriminate among the possible explanations for this quasi-periodicity.

  4. Separation of Different Contributions to the Total X-ray Luminosity in Gamma-ray Loud Blazars

    Institute of Scientific and Technical Information of China (English)

    Jun-Hui Fan; Gustavo E. Romero; Yong-Xiang Wang; Jiang-Shui Zhang

    2005-01-01

    The relativistic beaming model has been successfully used to explain many of the observational properties of active galactic nuclei. In this model the total emission is formed by two components, one beamed, one unbeamed. However,the exact contribution from each component in unresolved sources is still not clear.In the radio band, the core and extended emissions are clearly separated. We adopt the method proposed by Kembhavi to separate the two contributions in the X-ray emissions in a sample of 19 gamma-ray loud blazars. It is clearly shown that the beamed emission dominates the X-ray flux and the unbeamed X-ray emission is correlated with the extended radio emission of the considered objects. We also find that the ratio of the beamed to the unbeamed X-ray luminosity is correlated with the X-ray spectral index, an effect that should be a consequence of the underlying X-ray emission mechanism.

  5. A hydrodynamical model for the Fermi-LAT γ-ray light curve of blazar PKS 1510-089

    Directory of Open Access Journals (Sweden)

    Cabrera J.I.

    2013-12-01

    Full Text Available A physical description of the formation and propagation of working surfaces inside the relativistic jet of the blazar PKS 1510-089 are used to model its γ -ray variability light curve using Fermi-LAT data from 2008 to 2012. The physical model is based on conservation laws of mass and momentum at the working surface as explained by Mendoza et al. (2009. The hydrodynamical description of a working surface is parametrized by the initial velocity and mass injection rate at the base of the jet. We show that periodic variations on the injected velocity profiles are able to account for the observed luminosity, fixing model parameters such as mass ejection rates of the central engine injected at the base of the jet, oscillation frequencies of the flow and maximum Lorentz factors of the bulk flow during a particular burst.

  6. Multiwaveband Variability of Blazars from Turbulent Plasma Passing through a Standing Shock: The Mother of Multi-zone Models

    Science.gov (United States)

    Marscher, Alan P.

    2011-09-01

    Multi-wavelength light curves of bright gamma-ray blazars (e.g., 3C 454.3) are compared with the model proposed by Marscher and Jorstad. In this scenario, much of the optical and high-energy radiation in a blazar is emitted near the 43 GHz core of the jet as seen in VLBA images, parsecs from the central engine. The main physical features are a turbulent ambient jet plasma that passes through a standing recollimation shock in the jet. The model allows for short time-scales of optical and gamma-ray variability by restricting the highest-energy electrons radiating at these frequencies to a small fraction of the turbulent cells, perhaps those with a particular orientation of the magnetic field relative to the shock front. Because of this, the volume filling factor at high frequencies is relatively low, while that of the electrons radiating below about 10 THz is near unity. Such a model is consistent with the (1) red-noise power spectra of flux variations, (2) shorter time-scales of variability at higher frequencies, (3) frequency dependence of polarization and its variability, and (4) breaks in the synchrotron spectrum by more than the radiative loss value of 0.5. Simulated light curves are generated by a numerical code that (as of May 2011) includes synchrotron radiation as well as inverse Compton scattering of seed photons from both a dust torus and a Mach disk at the jet axis. The latter source of seed photons produces more pronounced variability in gamma-ray than in optical light curves, as is often observed. More features are expected to be added to the code by the time of the presentation. This research is supported in part by NASA through Fermi grants NNX08AV65G and NNX10AO59G, and by NSF grant AST-0907893.

  7. γ-RAY AND PARSEC-SCALE JET PROPERTIES OF A COMPLETE SAMPLE OF BLAZARS FROM THE MOJAVE PROGRAM

    International Nuclear Information System (INIS)

    We investigate the Fermi Large Area Telescope γ-ray and 15 GHz Very Long Baseline Array radio properties of a joint γ-ray and radio-selected sample of active galactic nuclei (AGNs) obtained during the first 11 months of the Fermi mission (2008 August 4-2009 July 5). Our sample contains the brightest 173 AGNs in these bands above declination –30° during this period, and thus probes the full range of γ-ray loudness (γ-ray to radio band luminosity ratio) in the bright blazar population. The latter quantity spans at least 4 orders of magnitude, reflecting a wide range of spectral energy distribution (SED) parameters in the bright blazar population. The BL Lac objects, however, display a linear correlation of increasing γ-ray loudness with synchrotron SED peak frequency, suggesting a universal SED shape for objects of this class. The synchrotron self-Compton model is favored for the γ-ray emission in these BL Lac objects over external seed photon models, since the latter predict a dependence of Compton dominance on Doppler factor that would destroy any observed synchrotron SED-peak-γ-ray-loudness correlation. The high-synchrotron peaked (HSP) BL Lac objects are distinguished by lower than average radio core brightness temperatures, and none display large radio modulation indices or high linear core polarization levels. No equivalent trends are seen for the flat-spectrum radio quasars (FSRQs) in our sample. Given the association of such properties with relativistic beaming, we suggest that the HSP BL Lac objects have generally lower Doppler factors than the lower-synchrotron peaked BL Lac objects or FSRQs in our sample.

  8. Monitoring the radio spectra of selected blazars in the Fermi-GST era. The Effelsberg 100 m telescope covering the cm band

    CERN Document Server

    Angelakis, E; Marchili, N; Krichbaum, T P; Zensus, J A

    2008-01-01

    The analysis of the spectral energy distribution variability at frequencies from radio to TeV is a powerful tool in the investigation of the dynamics, the physics and the structure evolution occurring in the most exotic flavour of active galaxies, the blazars. In particular, the presence of {\\sl Fermi-GST} is providing a unique opportunity for such studies delivering $\\gamma$-ray data of unprecedented quality. Here we introduce a monitoring program that has been running at the Effelsberg 100m telescope since January 2007, underpinning a broad multi-frequency collaboration of facilities that cover the band from radio to infrared. Sixty one selected blazars are observed monthly between 2.64 GHz and 43 GHz. The calibration accuracy is better than a few percent as it is demonstrated with some preliminary examples.

  9. The SMARTS Multi-epoch Optical Spectroscopy Atlas (SAMOSA): Using Emission Line Variability to Probe the Location of the Blazar Gamma-emitting Region

    CERN Document Server

    Isler, Jedidah C; Bailyn, C; Smith, P S; Coppi, P; Brady, M; Macpherson, E; Hasan, I; Buxton, M

    2015-01-01

    We present multi-epoch optical spectroscopy of seven southern Fermi-monitored blazars from 2008 - 2013 using the Small and Medium Aperture Research Telescope System (SMARTS), with supplemental spectroscopy and polarization data from the Steward Observatory. We find that the emission lines are much less variable than the continuum; 4 of 7 blazars had no detectable emission line variability over the 5 years. This is consistent with photoionization primarily by an accretion disk, allowing us to use the lines as a probe of disk activity. Comparing optical emission line flux with Fermi $\\gamma$-ray flux and optical polarized flux, we investigate whether relativistic jet variability is related to the accretion flow. In general, we see no such dependence, suggesting the jet variability is likely caused by internal processes like turbulence or shock acceleration rather than a variable accretion rate. However, three sources showed statistically significant emission line flares in close temporal proximity to very large...

  10. Impact of oscillations of photons into axion-like particles on the very-high energy γ-ray spectrum of the blazar PKS 1424+240

    CERN Document Server

    Meyer, Manuel

    2013-01-01

    Very high energy (VHE) gamma-rays undergo pair production with low energy photons of background radiation fields. This leads to an attenuation of the primary gamma-ray flux of extragalactic sources in the interaction with the extragalactic background light (EBL) which stretches from ultraviolet to far-infrared wavelengths. In the presence of magnetic fields, gamma-rays could oscillate into hypothetical axion-like particles (ALPs). This might lead to a reduced opacity of the Universe for VHE gamma-rays, as ALPs circumvent pair production. Here, the impact of photon-ALP conversions on the spectrum of PKS1424+240 is demonstrated. A lower limit on the redshift of this blazar was recently determined to be $z \\geqslant 0.6035$, making it the farthest source ever observed at VHE energies. Under the assumption of a specific magnetic field scenario and EBL model, photon-ALP couplings are derived that lead to an overall concave intrinsic blazar spectrum.

  11. Relaxation of Blazar Induced Pair Beams in Cosmic Voids: Measurement of Magnetic Field in Voids and Thermal History of the IGM

    CERN Document Server

    Miniati, Francesco

    2012-01-01

    The stability properties of a low density ultra relativistic pair beam produced in the intergalactic medium by multi-TeV gamma-ray photons from blazars are analyzed. The problem is relevant for probes of magnetic field in cosmic voids through gamma-ray observations. In addition, dissipation of such beams could affect considerably the thermal history of the intergalactic medium and structure formation. We use a Monte Carlo method to quantify the shower properties, in particular the bulk Lorentz factor and the angular spread of the beam, as a function of distance from the blazar. We find that the fastest growing modes, like any perturbation mode with even a very modest component perpendicular to the beam direction, requires a kinetic treatment. Combined with the effect of non-linear Landau damping, which suppresses the growth of plasma oscillations, the beam relaxation timescale is found typically longer than a Hubble time. Finally, density inhomogeneities associated with cosmic structure induce severe loss of ...

  12. Curvature of the spectral energy distribution, the dominant process for inverse Compton component and other jet properties in Fermi 2LAC blazars

    CERN Document Server

    Xue, R; Du, L M; Wang, Z R; Xie, Z H; Yi, T F; Xiong, D R; Xu, Y B; Liu, W G; Yu, X L

    2016-01-01

    We fit the spectral energy distributions (SEDs) of members of a large sample of Fermi 2LAC blazars to synchrotron and inverse Compton (IC) models. Our main results are as follows. (i) As suggested by previous works, the correlation between peak frequency and curvature can be explained by statistical or stochastic particle acceleration mechanisms. For BL Lacs, we find a linear correlation between synchrotron peak frequency and its curvature. The slope of the correlation is consistent with the stochastic acceleration mechanisms and confirm previous studies. For FSRQs, we also find a linear correlation, but its slope cannot be explained by previous theoretical models. (ii) We find a significant correlation between IC luminosity and synchrotron luminosity. The slope of the correlation of FSRQs is consistent with the EC process. And the slope of the correlation of BL Lac is consistent with the SSC process. (iii) We find several significant correlations between IC curvature and several basic parameters of blazars (...

  13. Observing the VHE Gamma Ray Sky with the MAGIC Telescopes: the Blazar B3 2247+381 and the Crab Pulsar

    OpenAIRE

    Giavitto, Gianluca

    2013-01-01

    El objetivo de esta tesis es ampliar nuestra comprensión de la física de dos clases de fuentes astrofísicas entre las más importantes emisoras de radiación no-térmica: blazars y púlsares. En particular, la tesis relata sobre la observación del blazar B3 2247 381 y el púlsar del Cangrejo. Este estudio se llevó a cabo mediante la medición de rayos gamma por encima de ~50 GeV con los telescopios MAGIC. Las dos clases de fuentes incluidas en esta tesis no están fuertemente re...

  14. Application of the MST clustering to the high energy γ-ray sky. III—New detections of γ-ray emission from blazars

    Science.gov (United States)

    Campana, R.; Massaro, E.; Bernieri, E.

    2016-06-01

    We present the results of a photon cluster search in the γ-ray sky observed by the Fermi Large Area Telescope, using the new Pass 8 dataset, at energies higher than 10 GeV. By means of the Minimum Spanning Tree (MST) algorithm, we found 25 clusters associated with catalogued blazars not previously known as γ-ray emitters. The properties of these sources are discussed.

  15. Application of the MST clustering to the high energy gamma-ray sky. III - New detections of gamma-ray emission from blazars

    CERN Document Server

    Campana, R; Bernieri, E

    2016-01-01

    We present the results of a photon cluster search in the gamma-ray sky observed by the Fermi Large Area Telescope, using the new Pass 8 dataset, at energies higher than 10 GeV. By means of the Minimum Spanning Tree (MST) algorithm, we found 25 clusters associated with catalogued blazars not previously known as gamma-ray emitters. The properties of these sources are discussed.

  16. Search for muon-neutrino emission from GeV and TeV gamma-ray flaring blazars using five years of data of the ANTARES telescope

    CERN Document Server

    Adrián-Martínez, S; André, M; Anton, G; Ardid, M; Aubert, J -J; Baret, B; Barrios-Martí, J; Basa, S; Bertin, V; Biagi, S; Bogazzi, C; Bormuth, R; Bou-Cabo, M; Bouwhuis, M C; Bruijn, R; Brunner, J; Busto, J; Capone, A; Caramete, L; Carr, J; Chiarusi, T; Circella, M; Coniglione, R; Costantini, H; Coyle, P; Creusot, A; Dekeyser, I; Deschamps, A; De Bonis, G; Distefano, C; Donzaud, C; Dornic, D; Drouhin, D; Dumas, A; Eberl, T; Elsässer, D; Enzenhöfer, A; Fehn, K; Felis, I; Fermani, P; Folger, F; Fusco, L A; Galatà, S; Gay, P; Geißelsöder, S; Geyer, K; Giordano, V; Gleixner, A; Gracia-Ruiz, R; Graf, K; van Haren, H; Heijboer, A J; Hello, Y; Hernández-Rey, J J; Herrero, A; Hößl, J; Hofestädt, J; Hugon, C; James, C W; de Jong, M; Kadler, M; Kalekin, O; Katz, U; Kießling, D; Kooijman, P; Kouchner, A; Kreykenbohm, I; Kulikovskiy, V; Lahmann, R; Lambard, G; Lattuada, D; Lefèvre, D; Leonora, E; Loucatos, S; Mangano, S; Margiotta, A; Martínez-Mora, J A; Martini, S; Mathieu, A; Michael, T; Migliozzi, P; Moussa, A; Mueller, C; Neff, M; Nezri, E; Păvălaş, G E; Pellegrino, C; Perrina, C; Piattelli, P; Popa, V; Pradier, T; Racca, C; Riccobene, G; Richter, R; Roensch, K; Rostovtsev, A; Saldaña, M; Samtleben, D F E; Sanguineti, M; Sapienza, P; Schmid, J; Schnabel, J; Schulte, S; Schüssler, F; Seitz, T; Sieger, C; Spurio, M; Steijger, J J M; Stolarczyk, Th; Sánchez-Losa, A; Taiuti, M; Tamburini, C; Trovato, A; Tselengidou, M; Tönnis, C; Turpin, D; Vallage, B; Vallée, C; Van Elewyck, V; Visser, E; Vivolo, D; Wagner, S; Wilms, J; Zornoza, J D; Zúñiga, J

    2015-01-01

    The ANTARES telescope is well-suited for detecting astrophysical transient neutrino sources as it can observe a full hemisphere of the sky at all times with a high duty cycle. The background due to atmospheric particles can be drastically reduced, and the point-source sensitivity improved, by selecting a narrow time window around possible neutrino production periods. Blazars, being radio-loud active galactic nuclei with their jets pointing almost directly towards the observer, are particularly attractive potential neutrino point sources, since they are among the most likely sources of the very high-energy cosmic rays. Neutrinos and gamma rays may be produced in hadronic interactions with the surrounding medium. Moreover, blazars generally show high time variability in their light curves at different wavelengths and on various time scales. This paper presents a time-dependent analysis applied to a selection of flaring gamma-ray blazars observed by the FERMI/LAT experiment and by TeV Cherenkov telescopes using ...

  17. Application of the MST clustering to the high energy gamma-ray sky. IV - Blazar candidates found as possible counterparts of photon clusters

    CERN Document Server

    Campana, R; Bernieri, E

    2016-01-01

    We present the results of a cluster search in the Fermi-LAT Pass 8 gamma-ray sky by means of the Minimum Spanning Tree algorithm, at energies higher than 10 GeV and at Galactic latitudes higher than 25 degrees. The selected clusters have a minimum number of photons higher than or equal to 5, a high degree of concentration, and are without a clear corresponding counterpart in blazar catalogues. A sample of 30 possible gamma-ray sources was obtained. These objects were verified by applying the standard Maximum Likelihood analysis on the Fermi-LAT data. A search for possible radio counterparts in a circle having a radius of 6 arcmin was performed, finding several interesting objects, the majority of them without optical spectroscopical data. These can be considered as new blazar candidates. Some of them were already noticed as possible blazars or Active Galactic Nuclei in previous surveys, but never associated with high energy emission. These possible counterparts are reported and their properties are discussed.

  18. PKS 1502+106: A high-redshift Fermi blazar at extreme angular resolution. Structural dynamics with VLBI imaging up to 86 GHz

    CERN Document Server

    Karamanavis, V; Krichbaum, T P; Angelakis, E; Hodgson, J; Nestoras, I; Myserlis, I; Zensus, J A; Sievers, A; Ciprini, S

    2016-01-01

    Context. Blazars are among the most energetic objects in the Universe. In 2008 August, Fermi/LAT detected the blazar PKS 1502+106 showing a rapid and strong gamma-ray outburst followed by high and variable flux over the next months. This activity at high energies triggered an intensive multi-wavelength campaign covering also the radio, optical, UV, and X-ray bands indicating that the flare was accompanied by a simultaneous outburst at optical/UV/X-rays and a delayed outburst at radio bands. Aims: In the current work we explore the phenomenology and physical conditions within the ultra-relativistic jet of the gamma-ray blazar PKS 1502+106. Additionally, we address the question of the spatial localization of the MeV/GeV-emitting region of the source. Methods: We utilize ultra-high angular resolution mm-VLBI observations at 43 and 86 GHz complemented by VLBI observations at 15 GHz. We also employ single-dish radio data from the F-GAMMA program at frequencies matching the VLBI monitoring. Results: PKS 1502+106 sh...

  19. Preparing GLAST LAT studies of the millisecond pulsar PSR J0218+4232 and the blazar 3C 66A

    International Nuclear Information System (INIS)

    Millisecond pulsars have weaker magnetic fields than normal pulsars, but their rapid rotation implies open field line voltages similar to those of young pulsars and they are therefore candidates for accelerating particles to the high energies required to emit in the GeV energy domain. PSR J0218+4232 was the only millisecond pulsar detected by EGRET. Its detection was rendered difficult by the powerful BL Lacertae 3C 66A a degree away, in spite of the low background (b= -16.8 degrees). Pulsations were detected at the 4.9 σ level, reinforcing the expectation that millisecond pulsars are a promising class for detection by the forthcoming high-energy mission GLAST. To estimate the GLAST LAT performance for both PSR J0218+4232 and 3C 66A, we have simulated LAT data using predictions for the 'polar cap' and the 'outer gap' pulsar models along with spectral energy distribution estimates for the blazar, normalizing to the EGRET observed fluxes. We demonstrate that GLAST is able to separate unambiguously the two objects in a few weeks. The spectral parameters of the pulsar derived in this context could be used to discriminate between the polar cap and outer gap models

  20. TIME SERIES ANALYSIS OF GAMMA-RAY BLAZARS AND IMPLICATIONS FOR THE CENTRAL BLACK-HOLE MASS

    International Nuclear Information System (INIS)

    Radiation from the blazar class of active galactic nuclei (AGNs) exhibits fast time variability which is usually ascribed to instabilities in the emission region near the central supermassive black hole. The variability time scale is generally faster in higher energy region, and data recently provided by the Fermi Gamma-ray Space Telescope in the GeV energy band enable a detailed study of the temporal behavior of AGN. Due to its wide field-of-view in the scanning mode, most sky regions are observed for several hours per day and daily light curves of many AGNs have been accumulated for more than 4 yr. In this paper we investigate the time variability of 15 well-detected AGNs by studying the normalized power spectrum density of their light curves in the GeV energy band. One source, 3C 454.3, shows a specific time scale of 6.8 × 105 s, and this value suggests, assuming the internal shock model, a mass for the central black hole of (108-1010) M☉ which is consistent with other estimates. It also indicates the typical time interval of ejected blobs is (7-70) times the light crossing time of the Schwarzschild radius