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Sample records for blazar spectral sequence

  1. Optical Spectral Variability of Blazars

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... 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 ...

  2. Blazar Sequence in Fermi Era

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... 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 ...

  3. Blazar Sequence in Fermi Era Liang Chen

    Indian Academy of Sciences (India)

    Abstract. 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 ...

  4. The Blazar Sequence 2.0

    Directory of Open Access Journals (Sweden)

    Gabriele Ghisellini

    2016-09-01

    Full Text Available This paper discusses the spectral energy distribution (SED of all blazars with redshift detected by the Fermi satellite and listed in the 3LAC catalog. The so called “blazar sequence” from the phenomenological point of view will be updated, with no theory or modelling. It will be shown 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 γ-ray emission; (iii at low bolometric luminosities, two different types 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.

  5. Multi-Band Spectral Properties of Fermi Blazars Benzhong Dai ...

    Indian Academy of Sciences (India)

    ... FSRQs, 41 AGNs of other types and 72 AGNs of unknown type (Abdo et al. 2010a). This large sample enable us to investigate the spectral shapes of blazars from optical to X-ray to γ-ray in more detail than has been done before. For this purpose, we collected data for all Fermi blazars having available spectral information.

  6. Blazar Sequence in Fermi Era Liang Chen

    Indian Academy of Sciences (India)

    HSP) blazars indicates that this simple analysis should be problematic. So does the discovery of numerous low-power-low-sychrotron-peaked (LP-LSP) blazars. If a blazar has a less beaming jet, its synchrotron bump should peak at lower fre- quency and lower power. Therefore, beaming effect may account for HP-HSP and.

  7. The Effect of Blazar Spectral Breaks on the Blazar Contribution to the Extragalactic Gamma-Ray Background

    Science.gov (United States)

    Venters, Tonia M.; Pavlidou, Vasiliki

    2011-01-01

    The spectral shapes of the contributions of different classes of unresolved gamma-ray emitters can provide insight into their relative contributions to the extragalactic gamma-ray background (EGB) and the natures of their spectra at GeV energies, We calculate the spectral shapes of the contributions to the EGB arising from BL Lacertae type objects (BL Lacs) and flat-spectrum radio quasars (FSRQs) assuming blazar spectra can be described as broken power laws, We fit the resulting total blazar spectral shape to the Fermi Large Area Telescope measurements of the EGB, finding that the best-fit shape reproduces well the shape of the Fermi EGB for various break scenarios. We conclude that a scenario in which the contribution of blazars is dominant cannot be excluded on spectral grounds alone, even if spectral breaks are shown to be common among Fermi blazars. We also find that while the observation of a featureless (within uncertainties) power-law EGB spectrum by Fermi does not necessarily imply a single class of contributing unresolved sources with featureless individual spectra, such an observation and the collective spectra of the separate contributing populations determine the ratios of their contributions. As such, a comparison with studies including blazar gamma-ray luminosity functions could have profound implications for the blazar contribution to the EGB, blazar evolution, and blazar gamma-ray spectra and emission.

  8. Relation between Radio Polarization and Spectral Index of Blazars ...

    Indian Academy of Sciences (India)

    ties, including rapid variability, high and variability polarization, high luminosity and superluminal motion, etc. Their optical variability timescales can cover a range of hours to years from radio to γ-rays (Fan et al. 2004; Ulrich et al. 1997). When we analyse the different characters of blazars, spectral index (α) is very important.

  9. The broadband spectral energy distributions of SDSS blazars

    Science.gov (United States)

    Li, Huai-Zhen; Chen, Luo-En; Jiang, Yun-Guo; Yi, Ting-Feng

    2015-07-01

    We compiled the radio, optical and X-ray data of blazars from the Sloan Digital Sky Survey database, and presented the distribution of luminosities and broadband spectral indices. The distribution of luminosities shows that the averaged luminosity of flat spectrum radio quasars (FSRQs) is larger than that of BL Lacertae (BL Lac) objects. On the other hand, the broadband spectral energy distribution reveals that FSRQs and low energy peaked BL Lac objects have similar spectral properties, but high energy peaked BL Lac objects have a distinct spectral property. This may be due to the fact that different subclasses of blazars have different intrinsic environments and are at different cooling levels. Even so, a unified scheme is also revealed from the color-color diagram, which hints that there are similar physical processes operating in all objects under a range of intrinsic physical conditions or beaming parameters. Supported by the National Natural Science Foundation of China.

  10. Blazar spectral variability as explained by a twisted inhomogeneous jet.

    Science.gov (United States)

    Raiteri, C M; Villata, M; Acosta-Pulido, J A; Agudo, I; Arkharov, A A; Bachev, R; Baida, G V; Benítez, E; Borman, G A; Boschin, W; Bozhilov, V; Butuzova, M S; Calcidese, P; Carnerero, M I; Carosati, D; Casadio, C; Castro-Segura, N; Chen, W-P; Damljanovic, G; D'Ammando, F; Di Paola, A; Echevarría, J; Efimova, N V; Ehgamberdiev, Sh A; Espinosa, C; Fuentes, A; Giunta, A; Gómez, J L; Grishina, T S; Gurwell, M A; Hiriart, D; Jermak, H; Jordan, B; Jorstad, S G; Joshi, M; Kopatskaya, E N; Kuratov, K; Kurtanidze, O M; Kurtanidze, S O; Lähteenmäki, A; Larionov, V M; Larionova, E G; Larionova, L V; Lázaro, C; Lin, C S; Malmrose, M P; Marscher, A P; Matsumoto, K; McBreen, B; Michel, R; Mihov, B; Minev, M; Mirzaqulov, D O; Mokrushina, A A; Molina, S N; Moody, J W; Morozova, D A; Nazarov, S V; Nikolashvili, M G; Ohlert, J M; Okhmat, D N; Ovcharov, E; Pinna, F; Polakis, T A; Protasio, C; Pursimo, T; Redondo-Lorenzo, F J; Rizzi, N; Rodriguez-Coira, G; Sadakane, K; Sadun, A C; Samal, M R; Savchenko, S S; Semkov, E; Skiff, B A; Slavcheva-Mihova, L; Smith, P S; Steele, I A; Strigachev, A; Tammi, J; Thum, C; Tornikoski, M; Troitskaya, Yu V; Troitsky, I S; Vasilyev, A A; Vince, O

    2017-12-21

    Blazars are active galactic nuclei, which are powerful sources of radiation whose central engine is located in the core of the host galaxy. Blazar emission is dominated by non-thermal radiation from a jet that moves relativistically towards us, and therefore undergoes Doppler beaming. This beaming causes flux enhancement and contraction of the variability timescales, so that most blazars appear as luminous sources characterized by noticeable and fast changes in brightness at all frequencies. The mechanism that produces this unpredictable variability is under debate, but proposed mechanisms include injection, acceleration and cooling of particles, with possible intervention of shock waves or turbulence. Changes in the viewing angle of the observed emitting knots or jet regions have also been suggested as an explanation of flaring events and can also explain specific properties of blazar emission, such as intra-day variability, quasi-periodicity and the delay of radio flux variations relative to optical changes. Such a geometric interpretation, however, is not universally accepted because alternative explanations based on changes in physical conditions-such as the size and speed of the emitting zone, the magnetic field, the number of emitting particles and their energy distribution-can explain snapshots of the spectral behaviour of blazars in many cases. Here we report the results of optical-to-radio-wavelength monitoring of the blazar CTA 102 and show that the observed long-term trends of the flux and spectral variability are best explained by an inhomogeneous, curved jet that undergoes changes in orientation over time. We propose that magnetohydrodynamic instabilities or rotation of the twisted jet cause different jet regions to change their orientation and hence their relative Doppler factors. In particular, the extreme optical outburst of 2016-2017 (brightness increase of six magnitudes) occurred when the corresponding emitting region had a small viewing angle

  11. Blazar spectral variability as explained by a twisted inhomogeneous jet

    Science.gov (United States)

    Raiteri, C. M.; Villata, M.; Acosta-Pulido, J. A.; Agudo, I.; Arkharov, A. A.; Bachev, R.; Baida, G. V.; Benítez, E.; Borman, G. A.; Boschin, W.; Bozhilov, V.; Butuzova, M. S.; Calcidese, P.; Carnerero, M. I.; Carosati, D.; Casadio, C.; Castro-Segura, N.; Chen, W.-P.; Damljanovic, G.; D'Ammando, F.; di Paola, A.; Echevarría, J.; Efimova, N. V.; Ehgamberdiev, Sh. A.; Espinosa, C.; Fuentes, A.; Giunta, A.; Gómez, J. L.; Grishina, T. S.; Gurwell, M. A.; Hiriart, D.; Jermak, H.; Jordan, B.; Jorstad, S. G.; Joshi, M.; Kopatskaya, E. N.; Kuratov, K.; Kurtanidze, O. M.; Kurtanidze, S. O.; Lähteenmäki, A.; Larionov, V. M.; Larionova, E. G.; Larionova, L. V.; Lázaro, C.; Lin, C. S.; Malmrose, M. P.; Marscher, A. P.; Matsumoto, K.; McBreen, B.; Michel, R.; Mihov, B.; Minev, M.; Mirzaqulov, D. O.; Mokrushina, A. A.; Molina, S. N.; Moody, J. W.; Morozova, D. A.; Nazarov, S. V.; Nikolashvili, M. G.; Ohlert, J. M.; Okhmat, D. N.; Ovcharov, E.; Pinna, F.; Polakis, T. A.; Protasio, C.; Pursimo, T.; Redondo-Lorenzo, F. J.; Rizzi, N.; Rodriguez-Coira, G.; Sadakane, K.; Sadun, A. C.; Samal, M. R.; Savchenko, S. S.; Semkov, E.; Skiff, B. A.; Slavcheva-Mihova, L.; Smith, P. S.; Steele, I. A.; Strigachev, A.; Tammi, J.; Thum, C.; Tornikoski, M.; Troitskaya, Yu. V.; Troitsky, I. S.; Vasilyev, A. A.; Vince, O.

    2017-12-01

    Blazars are active galactic nuclei, which are powerful sources of radiation whose central engine is located in the core of the host galaxy. Blazar emission is dominated by non-thermal radiation from a jet that moves relativistically towards us, and therefore undergoes Doppler beaming. This beaming causes flux enhancement and contraction of the variability timescales, so that most blazars appear as luminous sources characterized by noticeable and fast changes in brightness at all frequencies. The mechanism that produces this unpredictable variability is under debate, but proposed mechanisms include injection, acceleration and cooling of particles, with possible intervention of shock waves or turbulence. Changes in the viewing angle of the observed emitting knots or jet regions have also been suggested as an explanation of flaring events and can also explain specific properties of blazar emission, such as intra-day variability, quasi-periodicity and the delay of radio flux variations relative to optical changes. Such a geometric interpretation, however, is not universally accepted because alternative explanations based on changes in physical conditions—such as the size and speed of the emitting zone, the magnetic field, the number of emitting particles and their energy distribution—can explain snapshots of the spectral behaviour of blazars in many cases. Here we report the results of optical-to-radio-wavelength monitoring of the blazar CTA 102 and show that the observed long-term trends of the flux and spectral variability are best explained by an inhomogeneous, curved jet that undergoes changes in orientation over time. We propose that magnetohydrodynamic instabilities or rotation of the twisted jet cause different jet regions to change their orientation and hence their relative Doppler factors. In particular, the extreme optical outburst of 2016–2017 (brightness increase of six magnitudes) occurred when the corresponding emitting region had a small viewing

  12. Spectral Index Changes with Brightness for γ-Ray Loud Blazars J. H. ...

    Indian Academy of Sciences (India)

    spectral index changes depending on γ-ray brightness is obtained. ... the γ-ray band. Key words. Active galactic nuclei (AGN): blazars: γ-ray emission: spectral index. 1. Introduction. Generally, the spectrum of one source changes with its .... Pearl River Scholar Funded Scheme (GDUPS) (2009), Yangcheng Scholar Funded.

  13. Variability of Spectral Energy Distribution of Blazar S5 0716+714 B ...

    Indian Academy of Sciences (India)

    Abstract. The emission from blazars is known to be variable at all wave- lengths. 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 param- eters of the jet. Meaningful modeling of ...

  14. Spectral Index Changes with Brightness for γ-Ray Loud Blazars J. H. ...

    Indian Academy of Sciences (India)

    spectral index changes depending on γ-ray brightness is obtained. ... the γ-ray band. Key words. Active galactic nuclei (AGN): blazars: γ-ray emission: spectral index. 1. Introduction. Generally, the spectrum of one source changes with its .... China (NSFC 11173009, NSFC 11203007), the research fund of Hunan University.

  15. Relation between Radio Polarization and Spectral Index of Blazars ...

    Indian Academy of Sciences (India)

    Introduction. Blazars are a very special class of extragalactic objects showing some special proper- ties, including rapid variability, high and variability polarization, high luminosity and superluminal motion, etc. Their optical variability timescales can cover a range of hours to years from radio to γ-rays (Fan et al. 2004; Ulrich ...

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

    Indian Academy of Sciences (India)

    Abstract. We collected the radio, K-band, optical, X-ray, and γ-ray data for 35 TeV blazars detected by Fermi LAT and studied the possible corre- lation between different broad band spectral indices (αr.o, αr.x, αir.o, αir.x, αo.γ , αx.γ ) in all states (average/high/low). Based on our results, we sug- gested that the seed photons ...

  17. SPECTRAL PROPERTIES OF BRIGHT FERMI-DETECTED BLAZARS IN THE GAMMA-RAY BAND

    International Nuclear Information System (INIS)

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Borgland, A. W.; Bouvier, A.; Atwood, W. B.; Axelsson, M.; Baldini, L.; Bellazzini, R.; Bregeon, J.; Brez, A.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bonamente, E.; Brigida, M.

    2010-01-01

    The gamma-ray energy spectra of bright blazars of the LAT Bright AGN Sample (LBAS) are investigated using Fermi-LAT data. Spectral properties (hardness, curvature, and variability) established using a data set accumulated over 6 months of operation are presented and discussed for different blazar classes and subclasses: flat spectrum radio quasars (FSRQs), low-synchrotron peaked BLLacs (LSP-BLLacs), intermediate-synchrotron peaked BLLacs (ISP-BLLacs), and high-synchrotron peaked BLLacs (HSP-BLLacs). The distribution of photon index (Γ, obtained from a power-law fit above 100 MeV) is found to correlate strongly with blazar subclass. The change in spectral index from that averaged over the 6 months observing period is < 0.2-0.3 when the flux varies by about an order of magnitude, with a tendency toward harder spectra when the flux is brighter for FSRQs and LSP-BLLacs. A strong departure from a single power-law spectrum appears to be a common feature for FSRQs. This feature is also present for some high-luminosity LSP-BLLacs, and a small number of ISP-BLLacs. It is absent in all LBAS HSP-BLLacs. For 3C 454.3 and AO 0235+164, the two brightest FSRQ source and LSP-BLLac source, respectively, a broken power law (BPL) gives the most acceptable of power law, BPL, and curved forms. The consequences of these findings are discussed.

  18. A New Statistical Approach to the Optical Spectral Variability in Blazars

    Directory of Open Access Journals (Sweden)

    Jose A. Acosta-Pulido

    2016-12-01

    Full Text Available We present a spectral variability study of a sample of about 25 bright blazars, based on optical spectroscopy. Observations cover the period from the end of 2008 to mid 2015, with an approximately monthly cadence. Emission lines have been identified and measured in the spectra, which permits us to classify the sources into BL Lac-type or FSRQs, according to the commonly used EW limit. We have obtained synthetic photometry and produced colour-magnitude diagrams which show different trends associated with the object classes: generally, BL Lacs tend to become bluer when brighter and FSRQs become redder when brighter, although several objects exhibit both trends, depending on brightness. We have also applied a pattern recognition algorithm to obtain the minimum number of physical components which can explain the variability of the optical spectrum. We have used NMF (Non-Negative Matrix Factorization instead of PCA (Principal Component Analysis to avoid un-realistic negative components. For most targets we found that 2 or 3 meta-components are enough to explain the observed spectral variability.

  19. Multi-Waveband Emission Maps of Blazars

    Indian Academy of Sciences (India)

    2016-01-27

    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 ...

  20. Bordism, stable homotopy and adams spectral sequences

    CERN Document Server

    Kochman, Stanley O

    1996-01-01

    This book is a compilation of lecture notes that were prepared for the graduate course "Adams Spectral Sequences and Stable Homotopy Theory" given at The Fields Institute during the fall of 1995. The aim of this volume is to prepare students with a knowledge of elementary algebraic topology to study recent developments in stable homotopy theory, such as the nilpotence and periodicity theorems. Suitable as a text for an intermediate course in algebraic topology, this book provides a direct exposition of the basic concepts of bordism, characteristic classes, Adams spectral sequences, Brown-Peter

  1. 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.

  2. Comprehensive monitoring of gamma-ray bright blazars. I. Statistical study of optical, X-ray, and gamma-ray spectral slopes

    Energy Technology Data Exchange (ETDEWEB)

    Williamson, Karen E.; Jorstad, Svetlana G.; Marscher, Alan P.; Agudo, Iván; Joshi, Manasvita; Malmrose, Michael P. [Institute for Astrophysical Research, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States); Larionov, Valeri M.; Blinov, Dmitry A.; Efimova, Natalia V.; Hagen-Thorn, Vladimir A.; Konstantinova, Tatiana S.; Kopatskaya, Evgenia N.; Larionova, Elena G.; Larionova, Liudmilla V. [Astronomical Institute, St. Petersburg State University, Universitetskij Pr. 28, Petrodvorets, 198504 St. Petersburg (Russian Federation); Smith, Paul S. [Steward Observatory, University of Arizona, Tucson, AZ 85721-0065 (United States); Arkharov, Arkady A. [Main (Pulkovo) Astronomical Observatory of RAS, Pulkovskoye shosse 60, 196140 St. Petersburg (Russian Federation); Casadio, Carolina; Gómez, José L.; Molina, Sol N. [Instituto de Astrofísica de Andalucía, CSIC, Apartado 3004, E-18080 Granada (Spain); McHardy, Ian M., E-mail: kwilliam@bu.edu [Department of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ (United Kingdom); and others

    2014-07-10

    We present γ-ray, X-ray, ultraviolet, optical, and near-infrared light curves of 33 γ-ray bright blazars over 4 years that we have been monitoring since 2008 August with multiple optical, ground-based telescopes and the Swift satellite, and augmented by data from the Fermi Gamma-ray Space Telescope and other publicly available data from Swift. The sample consists of 21 flat-spectrum radio quasars (FSRQs) and 12 BL Lac objects (BL Lacs). We identify quiescent and active states of the sources based on their γ-ray behavior. We derive γ-ray, X-ray, and optical spectral indices, α{sub γ}, α{sub X}, and α{sub o}, respectively (F{sub ν}∝ν{sup α}), and construct spectral energy distributions during quiescent and active states. We analyze the relationships between different spectral indices, blazar classes, and activity states. We find (1) significantly steeper γ-ray spectra of FSRQs than for BL Lacs during quiescent states, but a flattening of the spectra for FSRQs during active states while the BL Lacs show no significant change; (2) a small difference of α{sub X} within each class between states, with BL Lac X-ray spectra significantly steeper than in FSRQs; (3) a highly peaked distribution of X-ray spectral slopes of FSRQs at ∼ –0.60, but a very broad distribution of α{sub X} of BL Lacs during active states; (4) flattening of the optical spectra of FSRQs during quiescent states, but no statistically significant change of α{sub o} of BL Lacs between states; and (5) a positive correlation between optical and γ-ray spectral slopes of BL Lacs, with similar values of the slopes. We discuss the findings with respect to the relative prominence of different components of high-energy and optical emission as the flux state changes.

  3. Comprehensive monitoring of gamma-ray bright blazars. I. Statistical study of optical, X-ray, and gamma-ray spectral slopes

    International Nuclear Information System (INIS)

    Williamson, Karen E.; Jorstad, Svetlana G.; Marscher, Alan P.; Agudo, Iván; Joshi, Manasvita; Malmrose, Michael P.; Larionov, Valeri M.; Blinov, Dmitry A.; Efimova, Natalia V.; Hagen-Thorn, Vladimir A.; Konstantinova, Tatiana S.; Kopatskaya, Evgenia N.; Larionova, Elena G.; Larionova, Liudmilla V.; Smith, Paul S.; Arkharov, Arkady A.; Casadio, Carolina; Gómez, José L.; Molina, Sol N.; McHardy, Ian M.

    2014-01-01

    We present γ-ray, X-ray, ultraviolet, optical, and near-infrared light curves of 33 γ-ray bright blazars over 4 years that we have been monitoring since 2008 August with multiple optical, ground-based telescopes and the Swift satellite, and augmented by data from the Fermi Gamma-ray Space Telescope and other publicly available data from Swift. The sample consists of 21 flat-spectrum radio quasars (FSRQs) and 12 BL Lac objects (BL Lacs). We identify quiescent and active states of the sources based on their γ-ray behavior. We derive γ-ray, X-ray, and optical spectral indices, α γ , α X , and α o , respectively (F ν ∝ν α ), and construct spectral energy distributions during quiescent and active states. We analyze the relationships between different spectral indices, blazar classes, and activity states. We find (1) significantly steeper γ-ray spectra of FSRQs than for BL Lacs during quiescent states, but a flattening of the spectra for FSRQs during active states while the BL Lacs show no significant change; (2) a small difference of α X within each class between states, with BL Lac X-ray spectra significantly steeper than in FSRQs; (3) a highly peaked distribution of X-ray spectral slopes of FSRQs at ∼ –0.60, but a very broad distribution of α X of BL Lacs during active states; (4) flattening of the optical spectra of FSRQs during quiescent states, but no statistically significant change of α o of BL Lacs between states; and (5) a positive correlation between optical and γ-ray spectral slopes of BL Lacs, with similar values of the slopes. We discuss the findings with respect to the relative prominence of different components of high-energy and optical emission as the flux state changes.

  4. FastMotif: spectral sequence motif discovery.

    Science.gov (United States)

    Colombo, Nicoló; Vlassis, Nikos

    2015-08-15

    Sequence discovery tools play a central role in several fields of computational biology. In the framework of Transcription Factor binding studies, most of the existing motif finding algorithms are computationally demanding, and they may not be able to support the increasingly large datasets produced by modern high-throughput sequencing technologies. We present FastMotif, a new motif discovery algorithm that is built on a recent machine learning technique referred to as Method of Moments. Based on spectral decompositions, our method is robust to model misspecifications and is not prone to locally optimal solutions. We obtain an algorithm that is extremely fast and designed for the analysis of big sequencing data. On HT-Selex data, FastMotif extracts motif profiles that match those computed by various state-of-the-art algorithms, but one order of magnitude faster. We provide a theoretical and numerical analysis of the algorithm's robustness and discuss its sensitivity with respect to the free parameters. The Matlab code of FastMotif is available from http://lcsb-portal.uni.lu/bioinformatics. vlassis@adobe.com Supplementary data are available at Bioinformatics online. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  5. Duality spectral sequences for Weierstrass fibrations and applications

    Science.gov (United States)

    Lo, Jason; Zhang, Ziyu

    2018-01-01

    We study duality spectral sequences for Weierstraß fibrations. Using these spectral sequences, we show that on a K-trivial Weierstraß threefold over a K-numerically trivial surface, any line bundle of nonzero fiber degree is taken by a Fourier-Mukai transform to a slope stable locally free sheaf.

  6. Order and correlations in genomic DNA sequences. The spectral approach

    International Nuclear Information System (INIS)

    Lobzin, Vasilii V; Chechetkin, Vladimir R

    2000-01-01

    The structural analysis of genomic DNA sequences is discussed in the framework of the spectral approach, which is sufficiently universal due to the reciprocal correspondence and mutual complementarity of Fourier transform length scales. The spectral characteristics of random sequences of the same nucleotide composition possess the property of self-averaging for relatively short sequences of length M≥100-300. Comparison with the characteristics of random sequences determines the statistical significance of the structural features observed. Apart from traditional applications to the search for hidden periodicities, spectral methods are also efficient in studying mutual correlations in DNA sequences. By combining spectra for structure factors and correlation functions, not only integral correlations can be estimated but also their origin identified. Using the structural spectral entropy approach, the regularity of a sequence can be quantitatively assessed. A brief introduction to the problem is also presented and other major methods of DNA sequence analysis described. (reviews of topical problems)

  7. A Steady-state Spectral Model for Electron Acceleration and Cooling in Blazar Jets: Application to 3C 279

    Science.gov (United States)

    Lewis, Tiffany R.; Finke, Justin D.; Becker, Peter A.

    2018-01-01

    We introduce a new theoretical model to describe the emitting region in a blazar jet. We adopt a one-zone leptonic picture and construct the particle transport equation for a plasma blob experiencing low-energy, monoenergetic particle injection, energy-dependent particle escape, shock acceleration, adiabatic expansion, stochastic acceleration, synchrotron radiation, and external Compton radiation from the dust torus and broad-line region (BLR). We demonstrate that a one-zone leptonic model is able to explain the IR though γ -ray spectrum for 3C 279 in 2008–2009. We determine that the BLR seed photons cannot be adequately described by a single average distribution, but rather we find that a stratified BLR provides an improvement in the estimation of the distance of the emitting region from the black hole. We calculate that the jet is not always in equipartition between the particles and magnetic field and find that stochastic acceleration provides more energy to the particles than does shock acceleration, where the latter is also overshadowed by adiabatic losses. We further introduce a novel technique to implement numerical boundary conditions and determine the global normalization for the electron distribution, based on analysis of stiff ordinary differential equations. Our astrophysical results are compared with those obtained by previous authors.

  8. Multiwavelength temporal and spectral variability of the blazar OJ 287 during and after the 2015 December flare: a major accretion disc contribution

    Science.gov (United States)

    Kushwaha, Pankaj; Gupta, Alok C.; Wiita, Paul J.; Gaur, Haritma; de Gouveia Dal Pino, E. M.; Bhagwan, Jai; Kurtanidze, O. M.; Larionov, V. M.; Damljanovic, G.; Uemura, M.; Semkov, E.; Strigachev, A.; Bachev, R.; Vince, O.; Gu, Minfeng; Zhang, Z.; Abe, T.; Agarwal, A.; Borman, G. A.; Fan, J. H.; Grishina, T. S.; Hirochi, J.; Itoh, R.; Kawabata, M.; Kopatskaya, E. N.; Kurtanidze, S. O.; Larionova, E. G.; Larionova, L. V.; Mishra, A.; Morozova, D. A.; Nakaoka, T.; Nikolashvili, M. G.; Savchenko, S. S.; Troitskaya, Yu. V.; Troitsky, I. S.; Vasilyev, A. A.

    2018-01-01

    We present a multiwavelength spectral and temporal analysis of the blazar OJ 287 during its recent activity between 2015 December and 2016 May, showing strong variability in the near-infrared (NIR) to X-ray energies with detection at γ-ray energies as well. Most of the optical flux variations exhibit strong changes in polarization angle and degree. All the interband time lags are consistent with simultaneous emissions. Interestingly, on days with excellent data coverage in the NIR-UV bands, the spectral energy distributions (SEDs) show signatures of bumps in the visible-UV bands, never seen before in this source. The optical bump can be explained as accretion-disc emission associated with the primary black hole of mass ∼ 1.8 × 1010 M⊙ while the little bump feature in the optical-UV appears consistent with line emission. Further, the broad-band SEDs extracted during the first flare and during a quiescent period during this span show very different γ-ray spectra compared to previously observed flare or quiescent spectra. The probable thermal bump in the visible seems to have been clearly present since 2013 May, as found by examining all available NIR-optical observations, and favours the binary supermassive black hole model. The simultaneous multiwavelength variability and relatively weak γ-ray emission that shows a shift in the SED peak is consistent with γ-ray emission originating from inverse Compton scattering of photons from the line emission that apparently contributes to the little blue bump.

  9. 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- &...

  10. Neutrinos and Ultra-high-energy Cosmic-ray Nuclei from Blazars

    Science.gov (United States)

    Rodrigues, Xavier; Fedynitch, Anatoli; Gao, Shan; Boncioli, Denise; Winter, Walter

    2018-02-01

    We discuss the production of ultra-high-energy cosmic-ray (UHECR) nuclei and neutrinos from blazars. We compute the nuclear cascade in the jet for both BL Lac objects and flat-spectrum radio quasars (FSRQs), and in the ambient radiation zones for FSRQs as well. By modeling representative spectral energy distributions along the blazar sequence, two distinct regimes are identified, which we call “nuclear survival” (typically found in low-luminosity BL Lacs) and “nuclear cascade” (typically found in high-luminosity FSRQs). We quantify how the neutrino and cosmic-ray (CR) emission efficiencies evolve over the blazar sequence, and we demonstrate that neutrinos and CRs come from very different object classes. For example, high-frequency-peaked BL Lacs (HBLs) tend to produce CRs, and high-luminosity FSRQs are the more efficient neutrino emitters. This conclusion does not depend on the CR escape mechanism, for which we discuss two alternatives (diffusive and advective escape). Finally, the neutrino spectrum from blazars is shown to significantly depend on the injection composition into the jet, especially in the nuclear cascade case: Injection compositions heavier than protons lead to reduced neutrino production at the peak, which moves at the same time to lower energies. Thus, these sources will exhibit better compatibility with the observed IceCube and UHECR data.

  11. Consequences of Proton Acceleration in Blazar Jets

    Directory of Open Access Journals (Sweden)

    Apostolos Mastichiadis

    2016-11-01

    Full Text Available Hadronic models of blazar emission constitute an interesting alternative to the more popular leptonic ones. Using the BL Lac object Mrk 421 as a characteristic example, we present two distinct ways of modeling the spectral energy distribution of blazars in the hadronic context, and we discuss the predictions of each 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.

  12. Frequency dependent polarization in blazars

    International Nuclear Information System (INIS)

    Bjoernsson, C.I.

    1984-10-01

    It is argued that the intrinsic frequency dependent polarization in blazars finds its most straightforward explanations in terms of a single rather than a multicomponent sourcemodel. In order to reproduce the observations, under the assumption that the emission mechanism is optically thin synchrotron radiation, both a well ordered magnetic field and an electron distribution with a sharp break or cuttoff are necessary. Non-uniform pitch angle distribution and/or environments where synchrotron losses are important are both conducive to producing strong frequency dependent polarization. Reasons are put forth as to why such conditions ar expected to occur in blazars. Two specific models are discussed in detail and it is shown that they are both able to produce strong frequency dependent polarization, even when the spectral index changes by a small amount only. (orig.)

  13. The Equivalence of Grayson and Friedlander-Suslin Spectral Sequences

    OpenAIRE

    Podkopaev, Oleg

    2013-01-01

    This thesis establishes the equivalence of Grayson and Friedlander-Suslin spectral sequences, that was previously only known for the respective E_2-terms. We develop the necessary techniques regarding K_0-presheaves of spectra, building on the work of M. Walker and construct certain filtrations on the K-theory presheaf of spectra that we use as intermediate steps in obtaining the equivalence of the filtrations.

  14. Iterated Differential Forms IV: C-Spectral Sequence

    OpenAIRE

    Vinogradov, A. M.; Vitagliano, L.

    2006-01-01

    For the multiple differential algebra of iterated differential forms (see math.DG/0605113 and math.DG/0609287) on a diffiety (O,C) an analogue of C-spectral sequence is constructed. The first term of it is naturally interpreted as the algebra of secondary iterated differential forms on (O,C). This allows to develop secondary tensor analysis on generic diffieties, some simplest elements of which are sketched here. The presented here general theory will be specified to infinite jet spaces and i...

  15. Spontaneous baroreflex by sequence and power spectral methods in humans.

    Science.gov (United States)

    Hughson, R L; Quintin, L; Annat, G; Yamamoto, Y; Gharib, C

    1993-11-01

    Beat-by-beat variations in blood pressure and RR-interval are interrelated by the actions of baroreflex and non-baroreflex responses. This study had two purposes: (1) to examine the spontaneous relationships between RR-interval and systolic blood pressure to determine the relative occurrence of baroreflex and non-baroreflex responses in humans, and (2) to compare the beat-sequence method with a cross spectral estimate of the baroreflex response slope. Eight healthy men were studied during 10 h of quiet, seated rest, and six men and three women were studied during rest, rest plus fixed pace breathing, and a cold pressor test. RR-interval and continuous, non-invasive arterial blood pressure were measured with a computerized system. A baroreflex sequence was defined by a series of at least three consecutive heart beats in which systolic pressure and the following RR-interval either both increased or both decreased. A non-baroreflex relationship was defined by sequences of at least three beats by opposite directional changes of RR-interval and systolic pressure of that beat. The results showed that there were approximately 30% as many non-baroreflex compared to baroreflex slopes. Individual subject mean baroreflex and non-baroreflex slopes were highly correlated (r = 0.72, P < 0.001). Absolute slope values were not different, and they were unaffected by time, fixed pace breathing, or cold pressor test. The data showed the relatively simple beat-by-beat sequence method to yield spontaneous baroreflex response slopes that were quantitatively similar to, and highly correlated with (r = 0.85-0.94), baroreflex response slopes calculated by spectral analysis methods.

  16. Core shift effect in blazars

    Science.gov (United States)

    Agarwal, A.; Mohan, P.; Gupta, Alok C.; Mangalam, A.; Volvach, A. E.; Aller, M. F.; Aller, H. D.; Gu, M. F.; Lähteenmäki, A.; Tornikoski, M.; Volvach, L. N.

    2017-07-01

    We studied the pc-scale core shift effect using radio light curves for three blazars, S5 0716+714, 3C 279 and BL Lacertae, which were monitored at five frequencies (ν) between 4.8 and 36.8 GHz using the University of Michigan Radio Astronomical Observatory (UMRAO), the Crimean Astrophysical Observatory (CrAO) and Metsähovi Radio Observatory for over 40 yr. Flares were Gaussian fitted to derive time delays between observed frequencies for each flare (Δt), peak amplitude (A) and their half width. Using A ∝ να, we infer α in the range of -16.67-2.41 and using Δ t ∝ ν ^{1/k_r}, we infer kr ∼ 1, employed in the context of equipartition between magnetic and kinetic energy density for parameter estimation. From the estimated core position offset (Ωrν) and the core radius (rcore), we infer that opacity model may not be valid in all cases. The mean magnetic field strengths at 1 pc (B1) and at the core (Bcore) are in agreement with previous estimates. We apply the magnetically arrested disc model to estimate black hole spins in the range of 0.15-0.9 for these blazars, indicating that the model is consistent with expected accretion mode in such sources. The power-law-shaped power spectral density has slopes -1.3 to -2.3 and is interpreted in terms of multiple shocks or magnetic instabilities.

  17. Core Dominance Parameter for -Ray Loud Blazars

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... 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 ...

  18. Smoothly Varying Bright Blazars

    Science.gov (United States)

    Van Alfen, Nicholas; Hindman, Lauren; Moody, Joseph Ward; Biancardi, Rochelle; Whipple, Parkes; Gaunt, Caleb

    2018-01-01

    It is becoming increasingly apparent that blazar light can vary sinusoidally with periods of hundreds of days to tens of years. Such behavior is expected of, among other things, jets coming from binary black holes. To look for general variability in lesser-known blazars and AGN, in 2015-2016 we monitored 182 objects with Johnson V-band magnitudes reported as being < 16. In all, this campaign generated 22,000 frames from 2,000 unique pointings. We find that approximately one dozen of these objects show evidence of smooth variability consistent with sinusoidal periods. We report on the entire survey sample, highlighting those that show sinusoidal variations.

  19. 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

  20. Debeamed Sequence of LBAS Blazars

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... Author Affiliations. Bangrong Huang1 2 Xiong Zhang2 Dingrong Xiong2 Haojin Zhang2. National Astronomical Observatories/Yunnan Observatory, 650011 Kunming, China. Department of Physics, Yunnan Normal University, 650500 Kunming, China.

  1. Stark widths regularities within spectral series of sodium isoelectronic sequence

    Science.gov (United States)

    Trklja, Nora; Tapalaga, Irinel; Dojčinović, Ivan P.; Purić, Jagoš

    2018-02-01

    Stark widths within spectral series of sodium isoelectronic sequence have been studied. This is a unique approach that includes both neutrals and ions. Two levels of problem are considered: if the required atomic parameters are known, Stark widths can be calculated by some of the known methods (in present paper modified semiempirical formula has been used), but if there is a lack of parameters, regularities enable determination of Stark broadening data. In the framework of regularity research, Stark broadening dependence on environmental conditions and certain atomic parameters has been investigated. The aim of this work is to give a simple model, with minimum of required parameters, which can be used for calculation of Stark broadening data for any chosen transitions within sodium like emitters. Obtained relations were used for predictions of Stark widths for transitions that have not been measured or calculated yet. This system enables fast data processing by using of proposed theoretical model and it provides quality control and verification of obtained results.

  2. Quasi Periodic Oscillations in Blazars

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... Home; Journals; Journal of Astrophysics and Astronomy; Volume 35; Issue 3. Quasi Periodic Oscillations in Blazars ... 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 ...

  3. Blazars with INTEGRAL

    Czech Academy of Sciences Publication Activity Database

    Hudec, René; Blažek, Martin; Kocka, Matúš; Pian, E.

    2009-01-01

    Roč. 18, 3-4 (2009), s. 327-335 ISSN 1392-0049. [INTEGRAL/BART workshop 2009. Karlovy Vary, 26.03.2009-29.03.2009] R&D Project s: GA ČR GA205/08/1207 Grant - others:ESA(XE) ESA-PECS project No. 98023 Institutional research plan: CEZ:AV0Z10030501 Keywords : active galaxies * blazars * gamma rays Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 1.032, year: 2009

  4. Probing the very-high-energy gamma-ray spectral curvature in the blazar PG 1553+113 with the MAGIC telescopes

    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 Oña; Mendez, C Delgado; Prester, D Dominis; Dorner, D; Doro, M; Einecke, S; Eisenacher, D; Elsaesser, D; 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; Muñoz, A González; 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; 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; Rügamer, S; Saito, T; Saito, K; Satalecka, K; Scalzotto, V; Scapin, V; Schultz, C; Schweizer, T; Sillanpää, A; Sitarek, J; Snidaric, I; Sobczynska, D; Spanier, F; Stamerra, A; Steinbring, T; Storz, J; Strzys, M; 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; Vogler, P; Will, M; Zanin, R; D'Ammando, F; Lähteenmäki, A; Tornikoski, M; Hovatta, T; Readhead, A C S; Max-Moerbeck, W; Richards, J.L

    2015-01-01

    PG 1553+113 is a very-high-energy (VHE, E>100 GeV) gamma-ray emitter classified as a BL Lac object. Its redshift is constrained by intergalactic absorption lines in the range 0.40.2). The observed curvature is compatible with the extragalactic background light (EBL) imprint predicted by the current generation of EBL models assuming a redshift z~0.4. New constraints on the redshift were derived from the VHE spectrum. These constraints are compatible with previous limits and suggest that the source is most likely located around the optical lower limit, z=0.4. Finally, we find that the synchrotron self-Compton (SSC) model gives a satisfactory description of the observed multi-wavelength spectral energy distribution during the flare.

  5. Methods for the Quasi-Periodic Variability Analysis in Blazars Y. Liu ...

    Indian Academy of Sciences (India)

    the variability analysis in blazars in optical and radio bands, to search for possible quasi-periodic signals. 2. Power spectral density (PSD). In statistical signal processing and physics, the power spectral density (PSD) is a positive real function of a frequency variable associated with a stationary stochas- tic process. Intuitively ...

  6. Statistical learning of music- and language-like sequences and tolerance for spectral shifts.

    Science.gov (United States)

    Daikoku, Tatsuya; Yatomi, Yutaka; Yumoto, Masato

    2015-02-01

    In our previous study (Daikoku, Yatomi, & Yumoto, 2014), we demonstrated that the N1m response could be a marker for the statistical learning process of pitch sequence, in which each tone was ordered by a Markov stochastic model. The aim of the present study was to investigate how the statistical learning of music- and language-like auditory sequences is reflected in the N1m responses based on the assumption that both language and music share domain generality. By using vowel sounds generated by a formant synthesizer, we devised music- and language-like auditory sequences in which higher-ordered transitional rules were embedded according to a Markov stochastic model by controlling fundamental (F0) and/or formant frequencies (F1-F2). In each sequence, F0 and/or F1-F2 were spectrally shifted in the last one-third of the tone sequence. Neuromagnetic responses to the tone sequences were recorded from 14 right-handed normal volunteers. In the music- and language-like sequences with pitch change, the N1m responses to the tones that appeared with higher transitional probability were significantly decreased compared with the responses to the tones that appeared with lower transitional probability within the first two-thirds of each sequence. Moreover, the amplitude difference was even retained within the last one-third of the sequence after the spectral shifts. However, in the language-like sequence without pitch change, no significant difference could be detected. The pitch change may facilitate the statistical learning in language and music. Statistically acquired knowledge may be appropriated to process altered auditory sequences with spectral shifts. The relative processing of spectral sequences may be a domain-general auditory mechanism that is innate to humans. Copyright © 2014 Elsevier Inc. All rights reserved.

  7. Gamma-Ray and Multiwavelength Emission from Blazars Meg Urry

    Indian Academy of Sciences (India)

    Abstract. 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 ...

  8. High-redshift Blazars through NuSTAR Eyes

    International Nuclear Information System (INIS)

    Marcotulli, L.; Paliya, V. S.; Ajello, M.; Kaur, A.; Hartmann, D. H.; Gasparrini, D.; Greiner, J.; Rau, A.; Schady, P.; Baloković, M.; Stern, D.; Madejski, G.

    2017-01-01

    The most powerful sources among the blazar family are MeV blazars. Often detected at z > 2, they usually display high X- and γ -ray luminosities, larger-than-average jet powers, and black hole masses ≳10 9 M ☉ . In the present work, we perform a multiwavelength study of three high-redshift blazars: 3FGL J0325.5+2223 ( z = 2.06), 3FGL J0449.0+1121 ( z = 2.15), and 3FGL J0453.2−2808 ( z = 2.56), analyzing quasi-simultaneous data from GROND, Swift -UVOT and XRT, Nuclear Spectroscopic Telescope Array ( NuSTAR ), and Fermi -LAT. Our main focus is on the hard X-ray band recently unveiled by NuSTAR (3–79 keV) where these objects show a hard spectrum that enables us to constrain the inverse Compton (IC) peak and the jet power. We found that all three targets resemble the most powerful blazars, with the synchrotron peak located in the submillimeter range and the IC peak in the MeV range, and therefore belong to the MeV blazar class. Using a simple one-zone leptonic emission model to reproduce the spectral energy distributions, we conclude that a simple combination of synchrotron and accretion disk emission reproduces the infrared–optical spectra, while the X-ray to γ -ray part is well reproduced by the IC scattering of low-energy photons supplied by the broad-line region. The black hole masses for each of the three sources are calculated to be ≳4 × 10 8 M ☉ . The three studied sources have jet power at the level of, or beyond, the accretion luminosity.

  9. Optical Spectral Variability of Blazars Haritma Gaur

    Indian Academy of Sciences (India)

    trend appears to hold. Key words. Galaxies: active—galaxies: .... fashion because it has never shown a large amount of optical activity (Gaur et al. 2012b). We found significant flux variations in all the ... tive correlation was found for any BL Lac which reflects the common trend for this class that they become bluer when they ...

  10. Optical Spectral Variability of Blazars Haritma Gaur

    Indian Academy of Sciences (India)

    of optically thin synchrotron emitting plasma, αthin (Urry & Padovani 1995). s indi- cates that the optical emission of HSPs is contaminated by other components, such as thermal contribution from the accretion disc or host galaxy, or else significant amounts of non-thermal emission originating from different regions of the ...

  11. (D,A)∞-modules over (D,A)∞-algebras and spectral sequences

    International Nuclear Information System (INIS)

    Lapin, S V

    2002-01-01

    We introduce the construction of a (D,A) ∞ -(co)module over a (D,A) ∞ -(co) algebra and study its main homotopy properties. We establish a connection between (D,A) ∞ -(co)modules over (D,A) ∞ -(co)algebras and spectral sequences, and thus obtain the structure of an A ∞ -comodule over the Milnor A ∞ -coalgebra on the homology of any spectrum directly from the differentials of the Adams spectral sequence of this spectrum

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

    International Nuclear Information System (INIS)

    Hoehne-Moench, Daniel

    2010-01-01

    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) γ-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 γ-ray flux, only X-ray selected sources with a flux F X >2 μJy 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 X-γ between the X-ray range at 1 keV and the VHE γ-ray regime at 200 GeV were calculated. The majority of objects show a spectral behaviour as expected from the source class of HBLs: The energy output in the VHE regime is in general lower than in X-rays. For the stacked blazar sample the broad-band spectral index was calculated to α X-γ =1.09, confirming the result found for the individual objects. Another evidence for the revelation of the baseline emission is the broad-band spectral energy distribution (SED) comprising archival as well as contemporaneous multi-wavelength data from the radio to the VHE band. The SEDs of known VHE γ-ray sources in low flux states matches well the SED of the stacked blazar sample. (orig.)

  13. Time-variant spectral peak and notch detection in echolocation-call sequences in bats.

    Science.gov (United States)

    Genzel, Daria; Wiegrebe, Lutz

    2008-01-01

    Bats are able to recognize and discriminate three-dimensional objects in complete darkness by analyzing the echoes of their ultrasonic emissions. Bats typically ensonify objects from different aspects to gain an internal representation of the three-dimensional object shape. Previous work suggests that, as a result, bats rely on the echo-acoustic analysis of spectral peaks and notches. Dependent on the aspect of ensonification, this spectral interference pattern changes over time in an object-specific manner. The speed with which the bats' auditory system can follow time-variant spectral interference patterns is unknown. Here, we measured the detection thresholds for temporal variations in the spectral content of synthesized echolocation calls in the echolocating bat, Megaderma lyra. In a two-alternative, forced-choice procedure, bats were trained to discriminate synthesized echolocation-call sequences with time-variant spectral peaks or notches from echolocation-call sequences with invariant peaks or notches. Detection thresholds of the spectral modulations were measured by varying the modulation depth of the time-variant echolocation-call sequences for modulation rates ranging from 2 to 16 Hz. Both for spectral peaks and notches, modulation-detection thresholds were at a modulation depth of approximately 11% of the centre frequency. Interestingly, thresholds were relatively independent of modulation rate. Acknowledging reservations about direct comparisons of active-acoustic and passive-acoustic auditory processing, the effectual sensitivity and modulation-rate independency of the obtained results indicate that the bats are well capable of tracking changes in the spectral composition of echoes reflected by complex objects from different angles.

  14. BROADBAND OBSERVATIONS OF HIGH REDSHIFT BLAZARS

    Energy Technology Data Exchange (ETDEWEB)

    Paliya, Vaidehi S. [Department of Physics and Astronomy, Clemson University, Kinard Lab of Physics, Clemson, SC 29634-0978 (United States); Parker, M. L.; Fabian, A. C. [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom); Stalin, C. S., E-mail: vpaliya@g.clemson.edu [Indian Institute of Astrophysics, Block II, Koramangala, Bangalore-560034 (India)

    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.

  15. Stark width regularities within spectral series of the lithium isoelectronic sequence

    Science.gov (United States)

    Tapalaga, Irinel; Trklja, Nora; Dojčinović, Ivan P.; Purić, Jagoš

    2018-03-01

    Stark width regularities within spectral series of the lithium isoelectronic sequence have been studied in an approach that includes both neutrals and ions. The influence of environmental conditions and certain atomic parameters on the Stark widths of spectral lines has been investigated. This study gives a simple model for the calculation of Stark broadening data for spectral lines within the lithium isoelectronic sequence. The proposed model requires fewer parameters than any other model. The obtained relations were used for predictions of Stark widths for transitions that have not yet been measured or calculated. In the framework of the present research, three algorithms for fast data processing have been made and they enable quality control and provide verification of the theoretically calculated results.

  16. J1026+2542 : Proper motion in a blazar jet at z=5.27

    NARCIS (Netherlands)

    Frey, S.; Paragi, Z.; Fogasy, J.O.; Gurvits, L.

    2014-01-01

    The radio-loud AGN J1026+2542 has recently been classified as the second most distant blazar, based on its broad-band spectral energy distribution and X-ray spectrum. The source with a prominent one-sided jet extending to at least ?20 mas was earlier observed with the VLBA at 5 GHz in January 2006.

  17. Modeling Blazar Spectra by Solving an Electron Transport Equation

    Science.gov (United States)

    Lewis, Tiffany; Finke, Justin; Becker, Peter A.

    2018-01-01

    Blazars are luminous active galaxies across the entire electromagnetic spectrum, but the spectral formation mechanisms, especially the particle acceleration, in these sources are not well understood. We develop a new theoretical model for simulating blazar spectra using a self-consistent electron number distribution. Specifically, we solve the particle transport equation considering shock acceleration, adiabatic expansion, stochastic acceleration due to MHD waves, Bohm diffusive particle escape, synchrotron radiation, and Compton radiation, where we implement the full Compton cross-section for seed photons from the accretion disk, the dust torus, and 26 individual broad lines. We used a modified Runge-Kutta method to solve the 2nd order equation, including development of a new mathematical method for normalizing stiff steady-state ordinary differential equations. We show that our self-consistent, transport-based blazar model can qualitatively fit the IR through Fermi g-ray data for 3C 279, with a single-zone, leptonic configuration. We use the solution for the electron distribution to calculate multi-wavelength SED spectra for 3C 279. We calculate the particle and magnetic field energy densities, which suggest that the emitting region is not always in equipartition (a common assumption), but sometimes matter dominated. The stratified broad line region (based on ratios in quasar reverberation mapping, and thus adding no free parameters) improves our estimate of the location of the emitting region, increasing it by ~5x. Our model provides a novel view into the physics at play in blazar jets, especially the relative strength of the shock and stochastic acceleration, where our model is well suited to distinguish between these processes, and we find that the latter tends to dominate.

  18. Correlation between Spectral Index and Doppler Factor for a ...

    Indian Academy of Sciences (India)

    Abstract. Relativistic beaming effect is important for blazars. In a very recent work, γ-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, αOX, and found an anticorrelation between them.

  19. Estimating Black Hole Masses of Blazars

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... 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 ...

  20. Multiwavelength Emission from Blazars – Conference Summary ...

    Indian Academy of Sciences (India)

    Abstract. 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 ...

  1. Automated Blazar Light Curves Using Machine Learning

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Spencer James [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-07-27

    This presentation describes a problem and methodology pertaining to automated blazar light curves. Namely, optical variability patterns for blazars require the construction of light curves and in order to generate the light curves, data must be filtered before processing to ensure quality.

  2. THE CONTRIBUTION OF FERMI -2LAC BLAZARS TO DIFFUSE TEV–PEV NEUTRINO FLUX

    Energy Technology Data Exchange (ETDEWEB)

    Aartsen, M. G. [Department of Physics, University of Adelaide, Adelaide, 5005 (Australia); Abraham, K. [Physik-department, Technische Universität München, D-85748 Garching (Germany); Ackermann, M. [DESY, D-15735 Zeuthen (Germany); Adams, J. [Dept. of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch (New Zealand); Aguilar, J. A.; Ansseau, I. [Université Libre de Bruxelles, Science Faculty CP230, B-1050 Brussels (Belgium); Ahlers, M. [Dept. of Physics and Wisconsin IceCube Particle Astrophysics Center, University of Wisconsin, Madison, WI 53706 (United States); Ahrens, M. [Oskar Klein Centre and Dept. of Physics, Stockholm University, SE-10691 Stockholm (Sweden); Altmann, D.; Anton, G. [Erlangen Centre for Astroparticle Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, D-91058 Erlangen (Germany); Andeen, K. [Department of Physics, Marquette University, Milwaukee, WI, 53201 (United States); Anderson, T.; Arlen, T. C. [Dept. of Physics, Pennsylvania State University, University Park, PA 16802 (United States); Archinger, M.; Baum, V. [Institute of Physics, University of Mainz, Staudinger Weg 7, D-55099 Mainz (Germany); Arguelles, C.; Axani, S. [Dept. of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Auffenberg, J. [III. Physikalisches Institut, RWTH Aachen University, D-52056 Aachen (Germany); Bai, X. [Physics Department, South Dakota School of Mines and Technology, Rapid City, SD 57701 (United States); Barwick, S. W., E-mail: thorsten.gluesenkamp@fau.de [Dept. of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Collaboration: IceCube Collaboration; and others

    2017-01-20

    The recent discovery of a diffuse cosmic neutrino flux extending up to PeV energies raises the question of which astrophysical sources generate this signal. Blazars are one class of extragalactic sources which may produce such high-energy neutrinos. We present a likelihood analysis searching for cumulative neutrino emission from blazars in the 2nd Fermi -LAT AGN catalog (2LAC) using IceCube neutrino data set 2009-12, which was optimized for the detection of individual sources. In contrast to those in previous searches with IceCube, the populations investigated contain up to hundreds of sources, the largest one being the entire blazar sample in the 2LAC catalog. No significant excess is observed, and upper limits for the cumulative flux from these populations are obtained. These constrain the maximum contribution of 2LAC blazars to the observed astrophysical neutrino flux to 27% or less between around 10 TeV and 2 PeV, assuming the equipartition of flavors on Earth and a single power-law spectrum with a spectral index of −2.5. We can still exclude the fact that 2LAC blazars (and their subpopulations) emit more than 50% of the observed neutrinos up to a spectral index as hard as −2.2 in the same energy range. Our result takes into account the fact that the neutrino source count distribution is unknown, and it does not assume strict proportionality of the neutrino flux to the measured 2LAC γ -ray signal for each source. Additionally, we constrain recent models for neutrino emission by blazars.

  3. Relation between X-Ray and γ-Ray Emissions for Fermi Blazars ...

    Indian Academy of Sciences (India)

    Abstract. Using γ-ray band data detected by Fermi Large Area Tele- scope (LAT) and X-ray band data for 78 blazars, we find a medium cor- relation between X-ray and γ-ray fluxes in the average state. A medium anticorrelation is also found between X-ray (1 KeV) mean spectral index αx and γ-ray mean spectral index αγ for ...

  4. TIMING SIGNATURES OF THE INTERNAL-SHOCK MODEL FOR BLAZARS

    International Nuclear Information System (INIS)

    Boettcher, M.; Dermer, C. D.

    2010-01-01

    We investigate the spectral and timing signatures of the internal-shock model for blazars. For this purpose, we develop a semi-analytical model for the time-dependent radiative output from internal shocks arising from colliding relativistic shells in a blazar jet. The emission through synchrotron and synchrotron-self Compton radiation as well as Comptonization of an isotropic external radiation field are taken into account. We evaluate the discrete correlation function (DCF) of the model light curves in order to evaluate features of photon-energy-dependent time lags and the quality of the correlation, represented by the peak value of the DCF. The almost completely analytic nature of our approach allows us to study in detail the influence of various model parameters on the resulting spectral and timing features. This paper focuses on a range of parameters in which the γ-ray production is dominated by Comptonization of external radiation, most likely appropriate for γ-ray bright flat-spectrum radio quasars (FSRQs) or low-frequency peaked BL Lac objects (LBLs). In most cases relevant for FSRQs and LBLs, the variability of the optical emission is highly correlated with the X-ray and high-energy (HE: > 100 MeV) γ-ray emission. Our baseline model predicts a lead of the optical variability with respect to the higher-energy bands by 1-2 hr and of the HE γ-rays before the X-rays by about 1 hr. We show that variations of certain parameters may lead to changing signs of inter-band time lags, potentially explaining the lack of persistent trends of time lags in most blazars.

  5. Stochastic modeling of the Fermi/LAT γ-ray blazar variability

    Energy Technology Data Exchange (ETDEWEB)

    Sobolewska, M. A.; Siemiginowska, A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Kelly, B. C. [Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93107 (United States); Nalewajko, K., E-mail: malgosia@camk.edu.pl [JILA, University of Colorado and National Institute of Standards and Technology, 440 UCB, Boulder, CO 80309 (United States)

    2014-05-10

    We study the γ-ray variability of 13 blazars observed with the Fermi/Large Area Telescope (LAT). These blazars have the most complete light curves collected during the first four years of the Fermi sky survey. We model them with the Ornstein-Uhlenbeck (OU) process or a mixture of the OU processes. The OU process has power spectral density (PSD) proportional to 1/f {sup α} with α changing at a characteristic timescale, τ{sub 0}, from 0 (τ >> τ{sub 0}) to 2 (τ << τ{sub 0}). The PSD of the mixed OU process has two characteristic timescales and an additional intermediate region with 0 < α < 2. We show that the OU model provides a good description of the Fermi/LAT light curves of three blazars in our sample. For the first time, we constrain a characteristic γ-ray timescale of variability in two BL Lac sources, 3C 66A and PKS 2155-304 (τ{sub 0} ≅ 25 days and τ{sub 0} ≅ 43 days, respectively, in the observer's frame), which are longer than the soft X-ray timescales detected in blazars and Seyfert galaxies. We find that the mixed OU process approximates the light curves of the remaining 10 blazars better than the OU process. We derive limits on their long and short characteristic timescales, and infer that their Fermi/LAT PSD resemble power-law functions. We constrain the PSD slopes for all but one source in the sample. We find hints for sub-hour Fermi/LAT variability in four flat spectrum radio quasars. We discuss the implications of our results for theoretical models of blazar variability.

  6. 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...... 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)....

  7. Atomic data and spectral line intensities for the neon isoelectronic sequence (Si V through Kr XXVII)

    International Nuclear Information System (INIS)

    Bhatia, A.K.; Feldman, U.; Seely, J.F.

    1985-01-01

    The electron impact collision strengths and the spontaneous radiative decay rates are presented for the following ions of the Ne isoelectronic sequence: Si V, Ar IX, TI XIII, Fe XVII, Ge XXIII and Kr XXVII. Data are given for the 27 levels that belong to four different configurations (2s 2 2p 6 , 2s 2 2p 5 3s, 2s 2 2p 5 3p, and 2s 2 2p 5 3d). By use of the atomic data calculations of the above-mentioned ions, the atomic data for all the ions with 14 13 , 10 14 , and 10 15 cm -3 . Spectral line intensities are also presented for all transitions with intensities within two orders of magnitude of the most intense line in each ion

  8. Poly(A) motif prediction using spectral latent features from human DNA sequences

    KAUST Repository

    Xie, Bo

    2013-06-21

    Motivation: Polyadenylation is the addition of a poly(A) tail to an RNA molecule. Identifying DNA sequence motifs that signal the addition of poly(A) tails is essential to improved genome annotation and better understanding of the regulatory mechanisms and stability of mRNA.Existing poly(A) motif predictors demonstrate that information extracted from the surrounding nucleotide sequences of candidate poly(A) motifs can differentiate true motifs from the false ones to a great extent. A variety of sophisticated features has been explored, including sequential, structural, statistical, thermodynamic and evolutionary properties. However, most of these methods involve extensive manual feature engineering, which can be time-consuming and can require in-depth domain knowledge.Results: We propose a novel machine-learning method for poly(A) motif prediction by marrying generative learning (hidden Markov models) and discriminative learning (support vector machines). Generative learning provides a rich palette on which the uncertainty and diversity of sequence information can be handled, while discriminative learning allows the performance of the classification task to be directly optimized. Here, we used hidden Markov models for fitting the DNA sequence dynamics, and developed an efficient spectral algorithm for extracting latent variable information from these models. These spectral latent features were then fed into support vector machines to fine-tune the classification performance.We evaluated our proposed method on a comprehensive human poly(A) dataset that consists of 14 740 samples from 12 of the most abundant variants of human poly(A) motifs. Compared with one of the previous state-of-the-art methods in the literature (the random forest model with expert-crafted features), our method reduces the average error rate, false-negative rate and false-positive rate by 26, 15 and 35%, respectively. Meanwhile, our method makes ?30% fewer error predictions relative to the other

  9. An examination of the sequence of intersecting lines using attenuated total reflectance-Fourier transform infrared spectral imaging.

    Science.gov (United States)

    Bojko, Katherine; Roux, Claude; Reedy, Brian J

    2008-11-01

    In this study, the potential of attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectral imaging as a technique to determine the sequence of line crossings was examined. The technique was successful in determining the sequence of heterogeneous line intersections produced using ballpoint pens and laser printers. By imaging at characteristic frequencies, it was possible to form spectral images showing the spatial distribution of the materials. By examining the spectral images from the inks, it was possible to determine whether the ink was above or below the toner. In blind testing, ATR-FTIR spectral imaging results were directly compared to those obtained by eight experienced forensic document examiners using methods regularly employed in casework. ATR-FTIR spectral imaging was shown to achieve a 100% success rate in the blind tests, whereas some incorrect sequence determinations were made by the forensic document examiners when using traditional techniques. The technique was unable to image ink-jet printing, gel pens, roller ball pens, and felt-tip pens, and was also unable to determine the sequence of intersecting ballpoint pen lines.

  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. Theoretical Study of the Effects of Magnetic Field Geometry on the High-Energy Emission of Blazars

    Directory of Open Access Journals (Sweden)

    Manasvita Joshi

    2016-10-01

    Full Text Available 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. (2014 to carry out this study and to relate the geometry of the field to the observed SEDs at X-ray and γ-ray energies. One of the goals of the study is to understand the relationship between synchrotron and inverse Compton peaks in blazar SEDs and the reason for the appearance of γ-ray “orphan flares” observed in some blazars. This can be associated with the directionality of the magnetic field, which creates a difference in the radiation field as seen by an observer versus that seen by the electrons in the emission region.

  12. Core Dominance Parameter for γ-Ray Loud Blazars SH Li, JH Fan ...

    Indian Academy of Sciences (India)

    Abstract. In this paper, we compiled 572 blazars that have known core dominance parameter (log R), out of which 121 blazars are γ-ray loud blazars. We compared log R between 121 blazars and the rest with non γ-ray detections, and found that γ-ray loud blazars showed a diffe- rent distribution, and their average value of ...

  13. Comparisons of Jet Properties between GeV Radio Galaxies and Blazars

    Science.gov (United States)

    Xue, Zi-Wei; Zhang, Jin; Cui, Wei; Liang, En-Wei; Zhang, Shuang-Nan

    2017-09-01

    We compile a sample of spectral energy distributions (SEDs) of 12 GeV radio galaxies (RGs), including eight FR I RGs and four FR II RGs. These SEDs can be represented with the one-zone leptonic model. No significant unification, as expected in the unification model, is found for the derived jet parameters between FR I RGs and BL Lacertae objects (BL Lacs) and between FR II RGs and flat spectrum radio quasars (FSRQs). However, on average FR I RGs have a larger {γ }{{b}} (break Lorentz factor of electrons) and lower B (magnetic field strength) than FR II RGs, analogous to the differences between BL Lacs and FSRQs. The derived Doppler factors (δ) of RGs are on average smaller than those of blazars, which is consistent with the unification model such that RGs are the misaligned parent populations of blazars with smaller δ. On the basis of jet parameters from SED fits, we calculate their jet powers and the powers carried by each component, and compare their jet compositions and radiation efficiencies with blazars. Most of the RG jets may be dominated by particles, like BL Lacs, not FSRQs. However, the jets of RGs with higher radiation efficiencies tend to have higher jet magnetization. A strong anticorrelation between synchrotron peak frequency and jet power is observed for GeV RGs and blazars in both the observer and co-moving frames, indicating that the “sequence” behavior among blazars, together with the GeV RGs, may be intrinsically dominated by jet power.

  14. Optical spectroscopic observations of blazars and γ-ray blazar candidates in the sloan digital sky survey data release nine

    Energy Technology Data Exchange (ETDEWEB)

    Massaro, F.; Masetti, N.; D' Abrusco, R.; Paggi, A.; Funk, S.

    2014-09-09

    We present an analysis of the optical spectra available in the Sloan Digital Sky Survey data release nine (SDSS DR9) for the blazars listed in the ROMA-BZCAT and for the γ-ray blazar candidates selected according to their IR colors. First, we adopt a statistical approach based on Monte Carlo simulations to find the optical counterparts of the blazars listed in the ROMA-BZCAT catalog. Then, we crossmatched the SDSS spectroscopic catalog with our selected samples of blazars and γ-ray blazar candidates, searching for those with optical spectra available to classify our blazar-like sources and, whenever possible, to confirm their redshifts. Our main objectives are to determine the classification of uncertain blazars listed in the ROMA-BZCAT and to discover new gamma-ray blazars. For the ROMA-BZCAT sources, we investigated a sample of 84 blazars, confirming the classification for 20 of them and obtaining 18 new redshift estimates. For the γ-ray blazars, indicated as potential counterparts of unassociated Fermi sources or with uncertain nature, we established the blazar-like nature of 8 out of the 27 sources analyzed and confirmed 14 classifications.

  15. Astronomical Plate Archives and Binary Blazars Studies

    Czech Academy of Sciences Publication Activity Database

    Hudec, René

    2011-01-01

    Roč. 32, 1-2 (2011), s. 91-95 ISSN 0250-6335. [Conference on Multiwavelength Variability of Blazars. Guangzhou, 22,09,2010-24,09,2010] R&D Projects: GA ČR GA205/08/1207 Grant - others:GA ČR(CZ) GA102/09/0997; MŠMT(CZ) ME09027 Institutional research plan: CEZ:AV0Z10030501 Keywords : astronomical plates * plate archives archives * binary blazars Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 0.400, year: 2011

  16. Combined stellar structure and atmosphere models for massive stars. II. Spectral evolution on the main sequence.

    Science.gov (United States)

    Schaerer, D.; de Koter, A.; Schmutz, W.; Maeder, A.

    1996-08-01

    In Schaerer et al. (1995, Paper I) we have presented the first ``combined stellar structure and atmosphere models'' (CoStar) for massive stars, which consistently treat the entire mass loosing star from the center out to the outer region of the stellar wind. The models use up-to-date input physics and state-of-the-art techniques to model both the stellar interior and the spherically expanding non-LTE atmosphere. The atmosphere models include line blanketing for all elements from hydrogen to zinc. The present publication covers the spectral evolution corresponding to the main sequence interior evolution discussed in Paper I. The CoStar results presented in this paper comprise: (a) flux distributions, from the EUV to the far IR, and the ionizing fluxes in the hydrogen and helium continua, (b) absolute optical and infrared UBVRIJHKLMN photometric magnitudes and UV colors, (c) detailed line blanketed UV spectra, and (d) non-LTE hydrogen and helium line spectra in the optical and IR, including theoretical K band spectra. These results may, e.g., be used for population synthesis models intended to study the massive star content in young starforming regions. We compare our results with other predictions from LTE and non-LTE plane parallel models and point out the improvements and the importance of using adequate atmosphere models including stellar winds for massive stars. Particular emphasis is given to comparisons of the UV spectral evolution with observations, including continuum indices and several metal line signatures of P-Cygni lines and broad absorption features. Good agreement is found for most UV features. In particular, we are able to reproduce the strong observed Fe III 1920A feature in late O and early B giants and supergiants. This feature is found to depend sensitively on temperature and may be used to derive effective temperatures for these stars. We also derive a simple formula to determine mass loss rates from the equivalent width of hydrogen

  17. Radio Band Observations of Blazar Variability

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... 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 ...

  18. An Exploration of the Triplet Periodicity in Nucleotide Sequences with a Mature Self-Adaptive Spectral Rotation Approach

    Directory of Open Access Journals (Sweden)

    Bo Chen

    2014-01-01

    Full Text Available Previously, for predicting coding regions in nucleotide sequences, a self-adaptive spectral rotation (SASR method has been developed, based on a universal statistical feature of the coding regions, named triplet periodicity (TP. It outputs a random walk, that is, TP walk, in the complex plane for the query sequence. Each step in the walk is corresponding to a position in the sequence and generated from a long-term statistic of the TP in the sequence. The coding regions (TP intensive are then visually discriminated from the noncoding ones (without TP, in the TP walk. In this paper, the behaviors of the walks for random nucleotide sequences are further investigated qualitatively. A slightly leftward trend (a negative noise in such walks is observed, which is not reported in the previous SASR literatures. An improved SASR, named the mature SASR, is proposed, in order to eliminate the noise and correct the TP walks. Furthermore, a potential sequence pattern opposite to the TP persistent pattern, that is, the TP antipersistent pattern, is explored. The applications of the algorithms on simulated datasets show their capabilities in detecting such a potential sequence pattern.

  19. Polarization Observations of the Fermi blazars

    Science.gov (United States)

    Rani, Bindu; S. Jorstad, A. P. Marscher (BU, USA), K. Sokolovsky (IAASARS, Greece), I. Agudo (CSIC, Spain)

    2018-01-01

    Ever since the revolutionary discovery by the Fermi mission that active galactic nuclei (AGN) produce copious amounts of high-energy emission, its origin has remained elusive. Using high-frequency radio interferometry (VLBI) polarization imaging, we could probe the magnetic field topology of the compact high-energy emission regions in blazars. A case study for blazar 3C 279 reveals presence of multiple gamma-ray emission regions. The observed anti-correlation between gamma-ray flux and percentage polarization at optical bands challenges the current high-energy emission models. In addition to the turbulent component responsible for gamma-ray flares, our analysis suggests the presence of a steady polarized component having with its polarization direction aligned along the jet axis. The steady polarized component could possibly be the toroidal component of the helical magnetic field. To better understand the acceleration processes in jets, high-energy polarization missions are of great importance.

  20. BLAZAR FLARES FROM COMPTON DRAGGED SHELLS

    Energy Technology Data Exchange (ETDEWEB)

    Golan, Omri; Levinson, Amir, E-mail: Levinson@wise.tau.ac.il [School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978 (Israel)

    2015-08-10

    We compute the dynamics and emission of dissipative shells that are subject to a strong Compton drag, under simplifying assumptions about the dissipation mechanism. We show that under conditions prevailing in blazars, substantial deceleration is anticipated on sub-parsec and parsec scales in cases of rapid dissipation. Such episodes may be the origin of some of the flaring activity occasionally observed in gamma-ray blazars. The shape of the light curves thereby produced reflects the geometry of the emitting surface if the deceleration is very rapid, or the dynamics of the shell if the deceleration is delayed, or initially more gradual, owing, e.g., to continuous injection of energy and momentum.

  1. Search for neutrinos from flaring blazars

    Energy Technology Data Exchange (ETDEWEB)

    Kreter, Michael [Lehrstuhl fuer Astronomie, Universitaet Wuerzburg, Emil-Fischer-Strasse 31, 97074 Wuerzburg (Germany); ECAP, Universitaet Erlangen-Nuernberg, Erwin-Rommel-Str. 1, 91058 Erlangen (Germany); Eberl, Thomas; James, Clancy [ECAP, Universitaet Erlangen-Nuernberg, Erwin-Rommel-Str. 1, 91058 Erlangen (Germany); Kadler, Matthias [Lehrstuhl fuer Astronomie, Universitaet Wuerzburg, Emil-Fischer-Strasse 31, 97074 Wuerzburg (Germany); Collaboration: ANTARES-KM3NeT-Erlangen-Collaboration

    2016-07-01

    Jets from Active Galactic Nuclei (AGN) are among the best candidates for the recently detected extraterrestrial neutrino flux. Hadronic AGN jet-emission models predict a tight correlation between the neutrino flux and the time-variable gamma-ray emission. At the same time, the atmospheric-background (noise) signal, which often dominates in neutrino-astronomical observations, can be substantially reduced by rejecting long-lasting periods of low flux. For these reasons, short high-amplitude gamma-ray flares, as often observed in blazars, can be used to substantially increase the sensitivity of neutrino telescopes in point-source searches. We develop a strategy to search for TeV neutrinos from flaring blazar jets from the TANAMI sample using the ANTARES telescope and Fermi gamma-ray light curves. An unbinned maximum-likelihood method is applied to optimize the probability of a neutrino detection from TANAMI sources.

  2. Investigation of blazars with the INTEGRAL satellite

    Czech Academy of Sciences Publication Activity Database

    Hudec, René; Kubánek, K.; Münz, Filip; Pian, E.

    2007-01-01

    Roč. 166, - (2007), s. 255-257 ISSN 0920-5632. [International Conference on Particle and Fundamental Physics in Space /3./. Beijing, 19.04.2007-21.04.2007] Grant - others:EU(XE) ESA-PECS project No. 98023 Institutional research plan: CEZ:AV0Z10030501 Source of funding: V - iné verejné zdroje Keywords : blazars * gamma-rays Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 0.875, year: 2005

  3. 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.

  4. Astronomical Plate Archives and Binary Blazars Studies Rene Hudec

    Indian Academy of Sciences (India)

    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. Key words. Astronomical plates—astronomical archives—binary blazars. 1. Introduction. The study of long-term activity of astrophysical ...

  5. Multi-Band Spectral Properties of Fermi Blazars Benzhong Dai ...

    Indian Academy of Sciences (India)

    Galaxies: active—BL Lacertae objects—general—gamma rays—observations. 1. Introduction. The First Fermi-LAT Catalogue (1LAC) of AGN, corresponding to 11 months of data collected in scientific operation mode, includes 709 AGNs, comprising 300 BL. Lacs, 296 FSRQs, 41 AGNs of other types and 72 AGNs of ...

  6. Visual Method for Spectral Energy Distribution Calculation of Blazars

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... School of Computer Science and Education Software, Guangzhou University, Guangzhou 510006, China. Astronomy Science and Technology Research Laboratory of Department of Education of Guangdong Province, Guangzhou 510006, China. Centre for Astrophysics, Guangzhou University, Guangzhou ...

  7. GAMMA-RAY EMISSION FROM TWO BLAZARS BEHIND THE GALACTIC PLANE: B2013+370 AND B2023+336

    International Nuclear Information System (INIS)

    Kara, E.; Errando, M.; Aliu, E.; Mukherjee, R.; Max-Moerbeck, W.; Readhead, A. C. S.; Richards, J. L.; Böttcher, M.; Fortin, P.; Halpern, J. P.

    2012-01-01

    B2013+370 and B2023+336 are two blazars at low-galactic latitude that were previously proposed to be the counterparts for the EGRET unidentified sources 3EG J2016+3657 and 3EG J2027+3429. Gamma-ray emission associated with the EGRET sources has been detected by the Fermi Gamma-ray Space Telescope, and the two sources, 1FGL J2015.7+3708 and 1FGL J2027.6+3335, have been classified as unidentified in the 1 year catalog. This analysis of the Fermi Large Area Telescope (LAT) data collected during 31 months reveals that the 1FGL sources are spatially compatible with the blazars and are significantly variable, supporting the hypothesis of extragalactic origin for the gamma-ray emission. The gamma-ray light curves are compared with 15 GHz radio light curves from the 40 m telescope at the Owens Valley Radio Observatory. Simultaneous variability is seen in both bands for the two blazar candidates. The study is completed with the X-ray analysis of 1FGL J2015.7+3708 using Swift observations that were triggered in 2010 August by a Fermi-detected flare. The resulting spectral energy distribution shows a two-component structure typical of blazars. We also identify a second source in the field of view of 1FGL J2027.6+3335 with similar characteristics to the known LAT pulsars. This study gives solid evidence favoring blazar counterparts for these two unidentified EGRET and Fermi sources, supporting the hypothesis that a number of unidentified gamma-ray sources at low-galactic latitudes are indeed of extragalactic origin.

  8. Spectral Sequences of Type Ia Supernovae. I. Connecting Normal and Subluminous SNe Ia and the Presence of Unburned Carbon

    Energy Technology Data Exchange (ETDEWEB)

    Heringer, E.; Kerkwijk, M. H. van [Department of Astronomy and Astrophysics, University of Toronto, 50 Saint George Street, Toronto, ON M5S 3H4 (Canada); Sim, S. A. [Astrophysics Research Centre, School of Mathematics and Physics, Queens University Belfast, Belfast BT7 1NN (United Kingdom); Kerzendorf, W. E. [European Southern Observatory (ESO), Karl-Schwarzschild-Straße 2, D-85748 Garching (Germany)

    2017-09-01

    Type Ia supernovae (SNe Ia) are generally agreed to arise from thermonuclear explosions of carbon–oxygen white dwarfs. The actual path to explosion, however, remains elusive, with numerous plausible parent systems and explosion mechanisms suggested. Observationally, SNe Ia have multiple subclasses, distinguished by their light curves and spectra. This raises the question of whether these indicate that multiple mechanisms occur in nature or that explosions have a large but continuous range of physical properties. We revisit the idea that normal and 91bg-like SNe can be understood as part of a spectral sequence in which changes in temperature dominate. Specifically, we find that a single ejecta structure is sufficient to provide reasonable fits of both the normal SN Ia SN 2011fe and the 91bg-like SN 2005bl, provided that the luminosity and thus temperature of the ejecta are adjusted appropriately. This suggests that the outer layers of the ejecta are similar, thus providing some support for a common explosion mechanism. Our spectral sequence also helps to shed light on the conditions under which carbon can be detected in premaximum SN Ia spectra—we find that emission from iron can “fill in” the carbon trough in cool SNe Ia. This may indicate that the outer layers of the ejecta of events in which carbon is detected are relatively metal-poor compared to events in which carbon is not detected.

  9. Spectral Velocity Estimation using the Autocorrelation Function and Sparse data Sequences

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt

    2005-01-01

    the sparse sequence and averaged over a pulse length. The 1:2 sequence using 2 flow emission for one b-Mode emissions showed a nearly indistinguishable spectrum compared to a Fourier spectrum calculated on the full data. The sparser sequences give a higher noise in the spectrum proportional to the sparseness......Ultrasound scanners can be used for displaying the distribution of velocities in blood vessels by finding the power spectrum of the received signal. It is desired to show a B-mode image for orientation and data for this has to be acquired interleaved with the flow data. Techniques for maintaining...... both the B-mode frame rate, and at the same time have the highest possible $f_{prf}$ only limited by the depth of investigation, are, thus, of great interest. The power spectrum can be calculated from the Fourier transform of the autocorrelation function $R_r(k)$. The lag $k$ corresponds...

  10. EXPORT: Spectral classification and projected rotational velocities of Vega-type and pre-main sequence stars

    Science.gov (United States)

    Mora, A.; Merín, B.; Solano, E.; Montesinos, B.; de Winter, D.; Eiroa, C.; Ferlet, R.; Grady, C. A.; Davies, J. K.; Miranda, L. F.; Oudmaijer, R. D.; Palacios, J.; Quirrenbach, A.; Harris, A. W.; Rauer, H.; Collier Cameron, A.; Deeg, H. J.; Garzón, F.; Penny, A.; Schneider, J.; Tsapras, Y.; Wesselius, P. R.

    2001-10-01

    In this paper we present the first comprehensive results extracted from the spectroscopic campaigns carried out by the EXPORT (EXoPlanetary Observational Research Team) consortium. During 1998-1999, EXPORT carried out an intensive observational effort in the framework of the origin and evolution of protoplanetary systems in order to obtain clues on the evolutionary path from the early stages of the pre-main sequence to stars with planets already formed. The spectral types of 70 stars, and the projected rotational velocities, v sin i, of 45 stars, mainly Vega-type and pre-main sequence, have been determined from intermediate- and high-resolution spectroscopy, respectively. The first part of the work is of fundamental importance in order to accurately place the stars in the HR diagram and determine the evolutionary sequences; the second part provides information on the kinematics and dynamics of the stars and the evolution of their angular momentum. The advantage of using the same observational configuration and methodology for all the stars is the homogeneity of the set of parameters obtained. Results from previous work are revised, leading in some cases to completely new determinations of spectral types and projected rotational velocities; for some stars no previous studies were available. Tables 1 and 2 are only, and Table 6 also, available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/378/116 Based on observations made with the Isaac Newton and the William Herschel telescopes operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

  11. General Physical Properties of CGRaBS Blazars

    Science.gov (United States)

    Paliya, Vaidehi S.; Marcotulli, L.; Ajello, M.; Joshi, M.; Sahayanathan, S.; Rao, A. R.; Hartmann, D.

    2017-12-01

    We present the results of a multi-frequency, time-averaged analysis of blazars included in the Candidate Gamma-ray Blazar Survey catalog. Our sample consists of 324 γ-ray detected (γ-ray loud) and 191 γ-ray undetected (γ-ray quiet) blazars; we consider all the data up to 2016 April 1. We find that both the γ-ray loud and γ-ray quiet blazar populations occupy similar regions in the WISE color-color diagram, and γ-ray loud sources are brighter in the radio and X-ray bands. A simple one-zone synchrotron inverse-Compton emission model is applied to derive the physical properties of both populations. We find that the central black hole mass and accretion disk luminosity ({L}{disk}) computed from the modeling of the optical-UV emission with a Shakura-Sunyaev disk reasonably matches that estimated from the optical spectroscopic emission-line information. A significantly larger Doppler boosting in the γ-ray loud blazars is noted, and their jets are more radiatively efficient. On the other hand, the γ-ray quiet objects are more MeV-peaked and thus could be potential targets for next-generation MeV missions. Our results confirm earlier findings about the accretion-jet connection in blazars; however, many of the γ-ray quiet blazars tend to deviate from the recent claim that the jet power exceeds {L}{disk} in blazars. A broadband study, considering a larger set of γ-ray quiet objects and also including BL Lacs, will be needed to confirm/reject this hypothesis as well as to verify the evolution of the powerful high-redshift blazars into their low-power nearby counterparts.

  12. Neuronal Correlates of Auditory Streaming in Monkey Auditory Cortex for Tone Sequences without Spectral Differences.

    Science.gov (United States)

    Knyazeva, Stanislava; Selezneva, Elena; Gorkin, Alexander; Aggelopoulos, Nikolaos C; Brosch, Michael

    2018-01-01

    This study finds a neuronal correlate of auditory perceptual streaming in the primary auditory cortex for sequences of tone complexes that have the same amplitude spectrum but a different phase spectrum. Our finding is based on microelectrode recordings of multiunit activity from 270 cortical sites in three awake macaque monkeys. The monkeys were presented with repeated sequences of a tone triplet that consisted of an A tone, a B tone, another A tone and then a pause. The A and B tones were composed of unresolved harmonics formed by adding the harmonics in cosine phase, in alternating phase, or in random phase. A previous psychophysical study on humans revealed that when the A and B tones are similar, humans integrate them into a single auditory stream; when the A and B tones are dissimilar, humans segregate them into separate auditory streams. We found that the similarity of neuronal rate responses to the triplets was highest when all A and B tones had cosine phase. Similarity was intermediate when the A tones had cosine phase and the B tones had alternating phase. Similarity was lowest when the A tones had cosine phase and the B tones had random phase. The present study corroborates and extends previous reports, showing similar correspondences between neuronal activity in the primary auditory cortex and auditory streaming of sound sequences. It also is consistent with Fishman's population separation model of auditory streaming.

  13. Neuronal Correlates of Auditory Streaming in Monkey Auditory Cortex for Tone Sequences without Spectral Differences

    Directory of Open Access Journals (Sweden)

    Stanislava Knyazeva

    2018-01-01

    Full Text Available This study finds a neuronal correlate of auditory perceptual streaming in the primary auditory cortex for sequences of tone complexes that have the same amplitude spectrum but a different phase spectrum. Our finding is based on microelectrode recordings of multiunit activity from 270 cortical sites in three awake macaque monkeys. The monkeys were presented with repeated sequences of a tone triplet that consisted of an A tone, a B tone, another A tone and then a pause. The A and B tones were composed of unresolved harmonics formed by adding the harmonics in cosine phase, in alternating phase, or in random phase. A previous psychophysical study on humans revealed that when the A and B tones are similar, humans integrate them into a single auditory stream; when the A and B tones are dissimilar, humans segregate them into separate auditory streams. We found that the similarity of neuronal rate responses to the triplets was highest when all A and B tones had cosine phase. Similarity was intermediate when the A tones had cosine phase and the B tones had alternating phase. Similarity was lowest when the A tones had cosine phase and the B tones had random phase. The present study corroborates and extends previous reports, showing similar correspondences between neuronal activity in the primary auditory cortex and auditory streaming of sound sequences. It also is consistent with Fishman’s population separation model of auditory streaming.

  14. THE WISE BLAZAR-LIKE RADIO-LOUD SOURCES: AN ALL-SKY CATALOG OF CANDIDATE γ-RAY BLAZARS

    International Nuclear Information System (INIS)

    D'Abrusco, R.; Paggi, A.; Smith, H. A.; Massaro, F.; Masetti, N.; Landoni, M.; Tosti, G.

    2014-01-01

    We present a catalog of radio-loud candidate γ-ray emitting blazars with WISE mid-infrared colors similar to the colors of confirmed γ-ray blazars. The catalog is assembled from WISE sources detected in all four WISE filters, with colors compatible with the three-dimensional locus of the WISE γ-ray emitting blazars, and which can be spatially cross-matched with radio sources from one of the three radio surveys: NVSS, FIRST, and/or SUMSS. Our initial WISE selection uses a slightly modified version of previously successful algorithms. We then select only the radio-loud sources using a measure of the radio-to-IR flux, the q 22 parameter, which is analogous to the q 24 parameter known in the literature but which instead uses the WISE band-four flux at 22 μm. Our final catalog contains 7855 sources classified as BL Lacs, FSRQs, or mixed candidate blazars; 1295 of these sources can be spatially re-associated as confirmed blazars. We describe the properties of the final catalog of WISE blazar-like radio-loud sources and consider possible contaminants. Finally, we discuss why this large catalog of candidate γ-ray emitting blazars represents a new and useful resource to address the problem of finding low-energy counterparts to currently unidentified high-energy sources

  15. 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.

  16. Nustar detection of the blazar B2 1023+25 at redshift 5.3

    DEFF Research Database (Denmark)

    Sbarrato, T.; Tagliaferri, G.; Ghisellini, G.

    2013-01-01

    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 × 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...

  17. Zeolites occurrences prognostic using image spectral analysis in the volcanic sequences of Pequenos Lembombos, Mozambique

    Directory of Open Access Journals (Sweden)

    Elmidio Estévez-Cruz

    2018-01-01

    Full Text Available The research aims at evaluating the mineral potential of the basaltic lavas of the Movene Formation, to host microcrystalline zeolites. In order to attain this goal the methods of digital image processing, geological traversing and mineralogical analysis are used in an integrated approach. Landsat 8 images were processed using standard tools such as color composite, band ratios and supervised classification methods to understand the geology of the area and to identify areas spectrally similar to the minerals studied. The interpretation of the digital elevation model allowed to reveal structures and their combined use with the color compositions facilitated the lithologic discrimination. Fieldworks were carried out in the areas with the highest exposure of the basaltic lavas to identify and sample the zeolites. Finally, the collected samples were analyzed by X-ray diffraction in order to determine mineral composition. The study increased the existing geological knowledge about this important industrial mineral, mapping five mineral occurrences and revealing the most promising areas to host this type of deposits. Favorable sectors are circumscribed to the northern part of the working area, and they are generally in the proximity of rhyolites-basalts contact. The following mineral phases were also identified: heulandite-clinoptilolite, mesolite, mordenite, stilbite and laumontite

  18. Extended radio emission and the nature of blazars

    International Nuclear Information System (INIS)

    Antonucci, R.R.J.; Ulvestad, J.S.

    1985-01-01

    The VLA has been used at 20 cm to map all 23 of the 54 confirmed blazars listed in the Angel and Stockman review paper that had not been mapped before at high resolution. (Blazars include BL Lac objects and optically violently variable quasars.) In addition, data on most of the previously mapped blazars have been reprocessed in order to achieve higher dynamic range. Extended emission has been detected associated with 49 of the 54 objects. The extended radio emission has been used to test the hypothesis that blazars are normal radio galaxies and radio quasars viewed along the jet axes. We find that blazars have substantial extended power, consistent with this hypothesis. Many have extended powers as high as the luminous Fanaroff-Riley class 2 radio doubles. The projected linear sizes are small, as expected from foreshortening of the extended sources, and many blazars have the expected core-halo morphology. There are also several small doubles, a head-tail source, and some one-sided sources, and these could be in cases where the line of sight is slightly off the jet axis, or projections of asymmetrical radio galaxies and quasars. The ratio of core to extended radio emission has been studied as a possible indicator of viewing aspect or beaming intensity. It is found to correlate with optical polarization, optical and radio core variability, and one-sided radio morphology. We can go beyond these consistency checks and work toward a proof of the hypothesis under discussion. The flux from the extended emission alone is sufficient in some blazars to qualify them for inclusion in the 3C and 4C catalogs. Suppose that the radio core emission is anisotropic, but the extended emission is predominantly isotropic. The isotropy of the extended emission implies that these blazars would be in the catalogs even if viewed from the side

  19. Variations of the Blazar AO 0235+164 in 2006-2015

    Science.gov (United States)

    Hagen-Thorn, V. A.; Larionov, V. M.; Morozova, D. A.; Arkharov, A. A.; Hagen-Thorn, E. I.; Shablovinskaya, E. S.; Prokop'eva, M. S.; Yakovleva, V. A.

    2018-02-01

    The results of optical, radio, and gamma-ray observations of the blazar AO 0235+16 are presented, including photometric ( BV RIJHK) and polarimetric ( R)monitoring carried out at St. Petersburg State University and the Central (Pulkovo) Astronomical Observatory in 2007-2015, 43 GHz Very Long Baseline Interferometry radio observations processed at Boston University, and a gamma-ray light curve based on observationswith the Fermi space observatory are presented. Two strong outbursts were detected. The relative spectral energy distributions of the variable components responsible for the outbursts are determined; these follow power laws, but with different spectral indices. The degree of polarization was high in both outbursts; only an average relationship between the brightness and polarization can be found. There was no time lag between the variations in the optical and gamma-ray, suggesting that the sources of the radiation in the optical and gamma-ray are located in the same region of the jet.

  20. X-Ray Intraday Variability of Five TeV Blazars with NuSTAR

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, Ashwani; Gupta, Alok C. [Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital 263002 (India); Wiita, Paul J., E-mail: ashwanitapan@gmail.com, E-mail: acgupta30@gmail.com, E-mail: wiitap@tcnj.edu [Department of Physics, The College of New Jersey, 2000 Pennington Road, Ewing, NJ 08628-0718 (United States)

    2017-06-01

    We have examined 40 Nuclear Spectroscopic Telescope Array ( NuSTAR ) light curves (LCs) of five TeV emitting high synchrotron peaked blazars: 1ES 0229+200, Mrk 421, Mrk 501, 1ES 1959+650, and PKS 2155−304. Four of the blazars showed intraday variability in the NuSTAR energy range of 3–79 keV. Using an autocorrelation function analysis we searched for intraday variability timescales in these LCs and found indications of several between 2.5 and 32.8 ks in eight LCs of Mrk 421, a timescale around 8.0 ks for one LC of Mrk 501, and timescales of 29.6 and 57.4 ks in two LCs of PKS 2155-304. The other two blazars’ LCs do not show any evidence for intraday variability timescales shorter than the lengths of those observations; however, the data were both sparser and noisier for them. We found positive correlations with zero lag between soft (3–10 keV) and hard (10–79 keV) bands for most of the LCs, indicating that their emissions originate from the same electron population. We examined spectral variability using a hardness ratio analysis and noticed a general “harder-when-brighter” behavior. The 22 LCs of Mrk 421 observed between 2012 July and 2013 April show that this source was in a quiescent state for an extended period of time and then underwent an unprecedented double-peaked outburst while monitored on a daily basis during 2013 April 10–16. We briefly discuss models capable of explaining these blazar emissions.

  1. Constraints on the Location of γ-Ray Sample of Blazars with Radio Core-shift Measurements

    Science.gov (United States)

    Wu, Linhui; Wu, Qingwen; Yan, Dahai; Chen, Liang; Fan, Xuliang

    2018-01-01

    We model simultaneous or quasi-simultaneous multi-band spectral energy distributions (SEDs) for a sample of 25 blazars that have radio core-shift measurements, where a one-zone leptonic model and Markov chain Monte Carlo technique are adopted. In the SED fitting for 23 low-synchrotron-peaked (LSP) blazars, the seed photons from the broad-line (BLR) and molecular torus are considered respectively in the external Compton process. We find that the SED fitting with the seed photons from the torus are better than those utilizing BLR photons, which suggest that the γ-ray emitting region may be located outside the BLR. Assuming the magnetic field strength in the γ-ray emitting region as constrained from the SED fitting follows the magnetic field distribution as derived from the radio core-shift measurements (i.e., B{(R)≃ {B}1{pc}(R/1{pc})}-1, where R is the distance from the central engine and {B}1{pc} is the magnetic field strength at 1 pc), we further calculate the location of the γ-ray emitting region, {R}γ , for these blazars. We find that {R}γ ∼ 2× {10}4{R}{{S}}≃ 10 {R}{BLR} ({R}{{S}} is the Schwarzschild radius and {R}{BLR} is the BLR size), where {R}{BLR} is estimated from the broad-line luminosities using the empirical correlations obtained using the reverberation mapping methods.

  2. Visual Method for Spectral Energy Distribution Calculation of ...

    Indian Academy of Sciences (India)

    c Indian Academy of Sciences. Visual Method for Spectral Energy Distribution Calculation of Blazars. Y. Huang1,3 & J. H. Fan2,3,∗. 1School of Computer Science and Education Software, Guangzhou University,. Guangzhou 510006, China. 2Centre for Astrophysics, Guangzhou University, Guangzhou 510006, China.

  3. RECONCILING MODELS OF LUMINOUS BLAZARS WITH MAGNETIC FLUXES DETERMINED BY RADIO CORE-SHIFT MEASUREMENTS

    Energy Technology Data Exchange (ETDEWEB)

    Nalewajko, Krzysztof; Begelman, Mitchell C. [JILA, University of Colorado and National Institute of Standards and Technology, 440 UCB, Boulder, CO 80309 (United States); Sikora, Marek, E-mail: knalew@stanford.edu [Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw (Poland)

    2014-11-20

    Estimates of magnetic field strength in relativistic jets of active galactic nuclei, 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 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.

  4. AWAKENING OF THE HIGH-REDSHIFT BLAZAR CGRaBS J0809+5341

    Energy Technology Data Exchange (ETDEWEB)

    Paliya, Vaidehi S.; Stalin, C. S. [Indian Institute of Astrophysics, Block II, Koramangala, Bangalore 560034 (India); Parker, M. L.; Fabian, A. C. [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom); Ramya, S. [Shanghai Astronomical Observatory, 80 Nandan Road, Shanghai 200030 (China); Covino, S.; Tagliaferri, G. [INAF-Osservatorio Astronomico di Brera, Via Bianchi 46, I-23807 Merate (Italy); Sahayanathan, S. [Astrophysical Sciences Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Ravikumar, C. D., E-mail: vaidehi@iiap.res.in [Department of Physics, University of Calicut, Malappuram 673635 (India)

    2015-04-20

    CGRaBS J0809+5341, a high-redshift blazar at z = 2.144, underwent a giant optical outburst on 2014 April 19 when it brightened by ∼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 Nuclear Spectroscopic Telescope Array, Swift, and ground-based optical facilities. For the first time, the source is detected in γ-rays by the Large Area Telescope on board the Fermi Gamma-Ray Space Telescope. A high optical polarization of ∼10% is also observed. Using the Sloan Digital Sky Survey spectrum, the accretion disk luminosity and black hole mass are estimated as 1.5 × 10{sup 45} erg s{sup −1} and 10{sup 8.4} M{sub ⊙}, respectively. Using a single zone leptonic emission model, we reproduce the spectral energy distribution of the source during the flaring activity. This analysis suggests that the emission region is probably located outside the broad-line region, and the jet becomes radiatively efficient. We also show that the overall properties of CGRaBS J0809+5341 seem to not be in agreement with the general properties observed in high-redshift blazars up to now.

  5. 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.

  6. Pulmonary parenchyma segmentation in thin CT image sequences with spectral clustering and geodesic active contour model based on similarity

    Science.gov (United States)

    He, Nana; Zhang, Xiaolong; Zhao, Juanjuan; Zhao, Huilan; Qiang, Yan

    2017-07-01

    While the popular thin layer scanning technology of spiral CT has helped to improve diagnoses of lung diseases, the large volumes of scanning images produced by the technology also dramatically increase the load of physicians in lesion detection. Computer-aided diagnosis techniques like lesions segmentation in thin CT sequences have been developed to address this issue, but it remains a challenge to achieve high segmentation efficiency and accuracy without much involvement of human manual intervention. In this paper, we present our research on automated segmentation of lung parenchyma with an improved geodesic active contour model that is geodesic active contour model based on similarity (GACBS). Combining spectral clustering algorithm based on Nystrom (SCN) with GACBS, this algorithm first extracts key image slices, then uses these slices to generate an initial contour of pulmonary parenchyma of un-segmented slices with an interpolation algorithm, and finally segments lung parenchyma of un-segmented slices. Experimental results show that the segmentation results generated by our method are close to what manual segmentation can produce, with an average volume overlap ratio of 91.48%.

  7. The Gamma-Ray Blazar Content of the Northern Sky

    Energy Technology Data Exchange (ETDEWEB)

    Michelson, Peter

    2003-07-16

    Using survey data, we have re-evaluated the correlation of flat spectrum radio sources with EGRET sources in the Northern sky. An analysis incorporating the radio and X-ray properties and the {gamma}-ray source localization is used to gauge the reliability of associations and to search for counterparts of previously unidentified EGRET sources. Above |b|=10{sup o}, where the classification is complete, we find that 70% of the Northern EGRET sources have counterparts similar to the bright EGRET blazars. For several of these we identify known blazar counterparts more likely than the earlier proposed 3EG association; for {approx}20 we have new identifications. Spectroscopic confirmation of these candidates is in progress and we have found flat spectrum radio quasars and BL Lac counterparts with redshifts as high as 4. We also find strong evidence for a set of 28 objects with no plausible counterpart like the known EGRET blazars. These thus represent either a new extragalactic population or a population of Galactic objects with a large scale height. The survey has been extended into the plane, where we find several new blazar candidates; the bulk of the sources are, however, Galactic. Looking ahead to the GLAST era, we predict that several of the present 3EG sources are composite and that higher resolution data will break these into multiple blazar IDs.

  8. Time Dependent Leptonic and Lepto-Hadronic Modeling of Blazar Emission

    Science.gov (United States)

    DIltz, Christopher S.

    2016-08-01

    Active galactic nuclei (AGN) are known to exhibit multi-wavelength variability across the whole electromagnetic spectrum. In the context of blazars, the variability timescale can be as short as a few minutes. Correlated variability has been seen in different bands of the electromagnetic spectrum: from radio wavelengths to high energy gamma-rays. This correlated variability in different wavelength bands can put constraints on the particle content, acceleration mechanisms and radiative properties of the relativistic jets that produce blazar emission. Two models are typically invoked to explain the origin of the broadband emission across the electromagnetic spectrum: Leptonic and Hadronic Modeling. Both models have had success in reproducing the broadband spectral energy distributions (SEDs) of blazar emission with different input parameters, making the origin of the emission difficult to determine. However, flaring events cause the spectral components that produce the SED to evolve on different timescales, producing different light curve behavior for both models. My Ph.D. research involves developing one-zone time dependent leptonic and lepto-hadronic codes to reproduce the broadband SEDs of blazars and then model flaring scenarios in order to find distinct differences between the two models. My lepto-hadronic code also considers the time dependent evolution of the radiation emitted by secondary particles (pions and muons) generated from photo-hadronic interactions between the photons and protons in the emission region. I present fits to the broadband SEDs of the flat spectrum radio quasars (FSRQs) 3C 273 and 3C 279 using my one-zone leptonic and lepto-hadronic model, respectively. I showed that by considering perturbations of any one of the selected input parameters for both models: magnetic field, particle injection luminosity, particle spectral index, and stochastic acceleration time scale, distinct differences arise in the light curves for the optical, X-ray and

  9. HIGH-ENERGY NEUTRINOS FROM RECENT BLAZAR FLARES

    Energy Technology Data Exchange (ETDEWEB)

    Halzen, Francis; Kheirandish, Ali [Wisconsin IceCube Particle Astrophysics Center and Department of Physics, University of Wisconsin, Madison, WI 53706 (United States)

    2016-11-01

    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 2015 June, 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 40 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.

  10. Intrinsic brightness temperatures of blazar jets at 15 GHz

    Directory of Open Access Journals (Sweden)

    Hovatta Talvikki

    2013-12-01

    Full Text Available We have developed a new Bayesian Markov Chain Monte Carlo method to deconvolve light curves of blazars into individual flares, including proper estimation of the fit errors. We use the method to fit 15GHzlight curves obtained within the OVRO 40-m blazar monitoring program where a large number of AGN have been monitored since 2008 in support of the Fermi Gamma-Ray Space Telescope mission. The time scales obtained from the fitted models are used to calculate the variability brightness temperature of the sources. Additionally, we have calculated brightness temperatures of a sample of these objects using Very Long Baseline Array data from the MOJAVE survey. Combining these two data sets enables us to study the intrinsic brightness temperature distribution in these blazars at 15 GHz. Our preliminary results indicate that the mean intrinsic brightness temperature in a sample of 14 sources is near the equipartition brightness temperature of ~ 1011K.

  11. Visual Method for Spectral Energy Distribution Calculation of ...

    Indian Academy of Sciences (India)

    Abstract. 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, αRO, αOX, and αRX 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 ...

  12. A Comparative Study of Multiwavelength Blazar Variability on Decades to Minutes Timescales

    Directory of Open Access Journals (Sweden)

    Arti Goyal

    2018-03-01

    Full Text Available Multiwavelength blazar variability is produced by noise-like processes with the power-law form of power spectral density (PSD. We present the results of our detailed investigation of multiwavelength ( γ -ray and optical light curves covering decades to minutes timescales, of two BL Lac objects namely, PKS 0735+178 and OJ 287. The PSDs are derived using discrete Fourier transform (DFT method. Our systematic approach reveals that OJ 287 is, on average, more variable than PKS 0735+178 at both optical and γ -ray energies on the corresponding time scales. On timescales shorter than ∼10 days, due to continuous and dense monitoring by the Kepler satellite, a steepening of power spectrum is observed for OJ 287. This indicates the necessity of an intermittent process generating variability on intra-night timescales for OJ 287.

  13. Circular Polarization in Turbulent Blazar Jets

    Directory of Open Access Journals (Sweden)

    Nicholas Roy MacDonald

    2017-11-01

    Full Text Available Circular polarization (CP provides an invaluable probe into the underlying plasma content of relativistic jets. CP can be generated within the jet through a physical process known as linear birefringence. This is a physical mechanism through which initially linearly polarized emission produced in one region of the jet is attenuated by Faraday rotation as it passes through other regions of the jet with distinct magnetic field orientations. Marscher developed the turbulent extreme multi-zone (TEMZ model of blazar emission which mimics these types of magnetic geometries with collections of thousands of plasma cells passing through a standing conical shock. I have recently developed a radiative transfer algorithm to generate synthetic images of the time-dependent circularly polarized intensity emanating from the TEMZ model at different radio frequencies. In this study, we produce synthetic multi-epoch observations that highlight the temporal variability in the circular polarization produced by the TEMZ model. We also explore the effect that different plasma compositions within the jet have on the resultant levels of CP.

  14. Unresolved Blazar Component of the Extragalactic Gamma-Ray Background

    Science.gov (United States)

    Stecker, Floyd W.; Venters, T. M.

    2011-01-01

    We present new theoretical estimates of the relative contribution of unresolved blazars and star forming galaxies to the extragalactic gamma-ray background and discuss constraints on the contributions from other possible components. We find that the Fermi data do not rule out a scenario in which the extragalactic gamma-ray background is dominated by emission from unresolved blazars. The spectrum of unresolved FSRQs, when accounting for the energy dependent effects of source confusion, could be consistent with the combined spectrum of the low energy EGRET extragalactic gamma-ray background measurements and the Fermi-LAT measurements above 200 MeV.

  15. What We Talk about When We Talk about Blazars?

    Directory of Open Access Journals (Sweden)

    Luigi Foschini

    2017-07-01

    Full Text Available After the discovery of powerful relativistic jets from Narrow-Line Seyfert 1 Galaxies, and the understanding of their similarity with those of blazars, a problem of terminology was born. The word blazar is today associated to BL Lac Objects and Flat-Spectrum Radio Quasars, which are somehow different from Narrow-Line Seyfert 1 Galaxies. Using the same word for all the three classes of AGN could drive either toward some misunderstanding, or to the oversight of some important characteristics. I review the main characteristics of these sources, and finally I propose a new scheme of classification.

  16. Modeling Broadband Variability of Blazars with Time-Dependent Multi-Zone Radiative Transfer Simulations

    Science.gov (United States)

    Fossati, Giovanni

    This proposal aims at fully exploiting the large body of X-ray and multiwavelength observational data on TeV gamma-ray bright blazars for a detailed comparison with state- of-the art blazar radiation transfer simulations. The aim of this investigation is to develop diagnostics on critical jet parameters and shock physics, such as the magnetic field, the kinetic energy content in the jets, the characteristics of the shock acceleration mechanisms, and the detailed influence on geometry on the observed spectral variability features. Our project will comprises a systematic, uniform re-analysis of the relevant (in particular, X-ray) data sets. We will extract time-dependent spectral energy distributions, light curves, and intra-band as well as inter-band time lags from the available data. The modeling tasks will start with a quick sweep through parameter space using a semi- analytical internal-shock model. This will help to narrow down parameters such as the Lorentz factors of interacting emission regions, the overall energy requirements, the characteristics of the electron distributions accelerated at internal shocks, and the magnetic field. The parameters of this semi-analytical internal-shock model that allow for a representation of time-dependent SEDs, light curves and inter-band time lags, will form the starting point for our detailed modeling using our state-of-the-art time-dependent multi-zone Monte-Carlo simulation code. Using that code, we will explore in more detail the characteristics of the particle acceleration in active regions and the influence of various geometries on the observable features. By capitalizing on archival data of several NASA space astrophysics missions our proposal is in agreement with the NASA ADAP research objective, "the analysis io NASA space astrophysics data that are archived in the public domain at the time of submission", as stated in the NASA Research announcement.

  17. The recent NIR Flare of the Blazar 3C279

    Science.gov (United States)

    Carrasco, L.; Recillas, E.; Porras, A.; Escobedo, G.; Chavushyan, V.

    2018-02-01

    In our monitoring campaign of AGNs we found the Blazar 3C279 flaring in the NIR on January 27th,2018. this source is cross identified with the quasar HB891253-055 and the Gamma-ray source 3FGLJ1256.1-054.

  18. Gamma-Ray and Multiwavelength Emission from Blazars Meg Urry

    Indian Academy of Sciences (India)

    Aperture Research Telescope System, located in Cerro Tololo, Chile, which is a set of five telescopes, each with unique optical and/or near-infrared instrumentation. (ANDICAM; Depoy et al. 2003). We used the SMARTS 1.3 m + ANDICAM to obtain simultaneous 0.4–2.2 m images of 3C454.3 and other southern blazars in.

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

    International Nuclear Information System (INIS)

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

    2015-01-01

    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)

  20. Quasi Periodic Oscillations in Blazars Alok C. Gupta

    Indian Academy of Sciences (India)

    QPOs) in blazars time series data in X-ray and optical elec- tromagnetic 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 ...

  1. Quasi Periodic Oscillations in Blazars Alok C. Gupta

    Indian Academy of Sciences (India)

    -quiet AGN .... blazar S5 0716 + 714, simultaneous optical and radio QPO were detected on ∼1 day timescale (Quirrenbach et al. ... beration mapping method which gives a mass of about 2.4 × 108M⊙ (Kaspi et al. 2000). Due to the substantial ...

  2. IDENTIFICATION OF NEW GAMMA-RAY BLAZAR CANDIDATES WITH MULTIFREQUENCY ARCHIVAL OBSERVATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Cowperthwaite, Philip S. [Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States); Massaro, F. [SLAC National Laboratory and Kavli Institute for Particle Astrophysics and Cosmology, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States); D' Abrusco, R.; Paggi, A.; Smith, Howard A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Tosti, G., E-mail: pcowpert@umd.edu [Dipartimento di Fisica, Università Degli Studi di Perugia, I-06123 Perugia (Italy)

    2013-11-01

    Blazars are a highly variable, radio-loud subclass of active galactic nuclei. In order to better understand such objects we must be able to easily identify candidate blazars from the growing population of unidentified sources. Working toward this goal, we attempt to identify new gamma-ray blazar candidates from a sample of 102 previously unidentified sources. These sources are selected from The Astronomer's Telegram and the literature on the basis of non-periodic variability and multi-wavelength behavior. We then attempt to associate these objects to an IR counterpart in the Wide-field Infrared Survey Explorer all-sky survey. We are able to identify 16 candidate sources whose IR colors are consistent with those of the blazar population. Of those, 13 sources have IR colors indicative of being gamma-ray emitting blazar candidates. These sources all possess archival multi-wavelength observations that support their blazar-like nature.

  3. 5-day photo-polarimetric WEBT Campaign on Blazar S5 0716+714 - a Study of Microvariabiltiy in Blazar

    Science.gov (United States)

    Bhatta, Gopal; Ostrwoski, Michal; Stawarz, Lukasz; Zola, Staszek; Jableka, Damian; Bachev, R.; Benitez, Erika; Dhalla, Sarah M.; Cason, Andy; Carosati, Daniele; Damljanovic, Goran; Frasca, A.; Hu, Shao Ming; Jorstad, Svetlana G.; Kurtanidze, O.; Larionov, Valeri; Leto, Giuseppe; Marscher, Alan P.; Moody, Joseph; Ohlert, Johhanes; Rizzi, Nicola; Sadun, Alberto C.; Sasada, Mahito; Sergeev, Sergey; Strigachev, Anton; Vince, Oliver; Webb, James Raymond; Whole Earth Blazar Telescope

    2015-01-01

    A whole earth blazar telescope (WEBT) campaign on blazar S5 0716+714 was organized to simultaneously monitor the source in multiple photo-polarimetric filters as a study of the nature of microvariability in blazar. The campaign, starting on March 2nd 2014, lasted for five consecutive days resulting in a rich data set- flux in B,V,R,I and near IR filters, and polarization degree (PD) and position angle (PA) in mainly R filter. Such a rich information provides with an unique opportunity to look deep into the localized emission regions in the jet of the blazar. During the campaign, the source remained active with 0.93 duty cycle and went through an oscillation of 0.3 magnitudes along with 5% change in PD and 50 degrees swing in PA. For 6.19 hrs the activity suddenly stopped in all the filters resulting in a plateau around 14 magnitudes in R filter light curve and then brightens by 0.14 mag in 2.96 hr time. We employed time series analysis in search of possible quasi-periodic oscillations and found some of the significant timescales present in the light curve which could reflect on the physical processes in the turbulent jet environment. In the color-magnitude analysis, we looked for 'bluer-when-brighter' trend widely claimed to be found in some of the blazars including the source. Although we found some of such incidences, they could not claimed to be persistent through out the campaign period. Similarly, no clear trend of correlation between flux and PD, and flux and PA could be established. A modeling of the mini-flares lasting few hours as stochastic synchrotron pulses on top of relative stable back ground emission and that incorporates simultaneous the change of color, PA and PD is underway.

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

    International Nuclear Information System (INIS)

    Aliu, E.; Archambault, S.; Arlen, T.; Aune, T.; Barnacka, A.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Benbow, W.; Cerruti, M.; Berger, K.; Bird, R.; Collins-Hughes, E.; Bouvier, A.; Chen, X.; Ciupik, L.; Connolly, M. P.; Cui, W.; Dumm, J.; Eisch, J. D.

    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 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

  5. 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...... of a few months. While no fast variability was detected during a single observation, both sources were variable in the X-ray band, up to 50%, between the two observations, with larger variability at higher energies. No variability was detected in the optical/NIR band. These data, together with Fermi......-Large Area Telescope, Wide-field Infrared Survey Explorer, and other literature data, are then used to study the overall spectral energy distributions (SEDs) of these blazars. Although the jet nonthermal emission dominates the SED, it leaves the UV band unhidden, allowing us to detect the thermal emission...

  6. 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

  7. The WEBT Campaign on the Blazar 3C 279 in 2006

    Science.gov (United States)

    Böttcher, M.; Basu, S.; Joshi, M.; Villata, M.; Arai, A.; Aryan, N.; Asfandiyarov, I. M.; Bach, U.; Bachev, R.; Berduygin, A.; Blaek, M.; Buemi, C.; Castro-Tirado, A. J.; De Ugarte Postigo, A.; Frasca, A.; Fuhrmann, L.; Hagen-Thorn, V. A.; Henson, G.; Hovatta, T.; Hudec, R.; Ibrahimov, M.; Ishii, Y.; Ivanidze, R.; Jelínek, M.; Kamada, M.; Kapanadze, B.; Katsuura, M.; Kotaka, D.; Kovalev, Y. Y.; Kovalev, Yu. A.; Kubánek, P.; Kurosaki, M.; Kurtanidze, O.; Lähteenmäki, A.; Lanteri, L.; Larionov, V. M.; Larionova, L.; Lee, C.-U.; Leto, P.; Lindfors, E.; Marilli, E.; Marshall, K.; Miller, H. R.; Mingaliev, M. G.; Mirabal, N.; Mizoguchi, S.; Nakamura, K.; Nieppola, E.; Nikolashvili, M.; Nilsson, K.; Nishiyama, S.; Ohlert, J.; Osterman, M. A.; Pak, S.; Pasanen, M.; Peters, C. S.; Pursimo, T.; Raiteri, C. M.; Robertson, J.; Robertson, T.; Ryle, W. T.; Sadakane, K.; Sadun, A.; Sigua, L.; Sohn, B.-W.; Strigachev, A.; Sumitomo, N.; Takalo, L. O.; Tamesue, Y.; Tanaka, K.; Thorstensen, J. R.; Tosti, G.; Trigilio, C.; Umana, G.; Vennes, S.; Vitek, S.; Volvach, A.; Webb, J.; Yamanaka, M.; Yim, H.-S.

    2007-12-01

    The quasar 3C 279 was the target of an extensive multiwavelength monitoring campaign from 2006 January through April. An optical-IR-radio monitoring campaign by the Whole Earth Blazar Telescope (WEBT) collaboration was organized around target-of-opportunity X-ray and soft γ-ray observations with Chandra and INTEGRAL in 2006 mid-January, with additional X-ray coverage by RXTE and Swift XRT. In this paper we focus on the results of the WEBT campaign. The source exhibited substantial variability of optical flux and spectral shape, with a characteristic timescale of a few days. The variability patterns throughout the optical BVRI bands were very closely correlated with each other, while there was no obvious correlation between the optical and radio variability. After the ToO trigger, the optical flux underwent a remarkably clean quasi-exponential decay by about 1 mag, with a decay timescale of τd~12.8 days. In intriguing contrast to other (in particular, BL Lac type) blazars, we find a lag of shorter wavelength behind longer wavelength variability throughout the RVB wavelength ranges, with a time delay increasing with increasing frequency. Spectral hardening during flares appears delayed with respect to a rising optical flux. This, in combination with the very steep IR-optical continuum spectral index of α0~1.5-2.0, may indicate a highly oblique magnetic field configuration near the base of the jet, leading to inefficient particle acceleration and a very steep electron injection spectrum. An alternative explanation through a slow (timescale of several days) acceleration mechanism would require an unusually low magnetic field of B<~0.2 G, about an order of magnitude lower than inferred from previous analyses of simultaneous SEDs of 3C 279 and other flat-spectrum radio quasars with similar properties. For questions regarding the availability of the data from the WEBT campaign presented in this paper, please contact the WEBT President Massimo Villata at villata@oato.inaf.it.

  8. 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.

  9. RELAXATION OF BLAZAR-INDUCED PAIR BEAMS IN COSMIC VOIDS

    Energy Technology Data Exchange (ETDEWEB)

    Miniati, Francesco [Physics Department, Wolfgang-Pauli-Strasse 27, ETH-Zuerich, CH-8093 Zuerich (Switzerland); Elyiv, Andrii, E-mail: fm@phys.ethz.ch [Institut d' Astrophysique et de Geophysique, Universite de Liege, B-4000 Liege (Belgium)

    2013-06-10

    The stability properties of a low-density ultrarelativistic pair beam produced in the intergalactic medium (IGM) 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 considerably affect the thermal history of the IGM and structure formation. We use a Monte Carlo method to quantify the properties of the blazar-induced electromagnetic shower, in particular the bulk Lorentz factor and the angular spread of the pair beam generated by the shower, as a function of distance from the blazar itself. We then use linear and nonlinear kinetic theory to study the stability of the pair beam against the growth of electrostatic plasma waves, employing the Monte Carlo results for our quantitative estimates. We find that the fastest growing mode, like any perturbation mode with even a very modest component perpendicular to the beam direction, cannot be described in the reactive regime. Due to the effect of nonlinear Landau damping, which suppresses the growth of plasma oscillations, the beam relaxation timescale is found to be significantly longer than the inverse Compton loss time. Finally, density inhomogeneities associated with cosmic structure induce loss of resonance between the beam particles and plasma oscillations, strongly inhibiting their growth. We conclude that relativistic pair beams produced by blazars in the IGM are stable on timescales that are long compared with the electromagnetic cascades. There appears to be little or no effect of pair beams on the IGM.

  10. BLAZAR OPTICAL VARIABILITY IN THE PALOMAR-QUEST SURVEY

    International Nuclear Information System (INIS)

    Bauer, Anne; Baltay, Charles; Coppi, Paolo; Ellman, Nancy; Jerke, Jonathan; Rabinowitz, David; Scalzo, Richard

    2009-01-01

    We study the ensemble optical variability of 276 flat-spectrum radio quasars (FSRQs) and 86 BL Lacs in the Palomar-QUEST Survey with the goal of searching for common fluctuation properties, examining the range of behavior across the sample, and characterizing the appearance of blazars in such a survey so that future work can more easily identify such objects. The survey, which covers 15,000 deg 2 multiple times over 3.5 years, allows for the first ensemble blazar study of this scale. Variability amplitude distributions are shown for the FSRQ and BL Lac samples for numerous time lags, and also studied through structure function analyses. Individual blazars show a wide range of variability amplitudes, timescales, and duty cycles. Of the best-sampled objects, 35% are seen to vary by more than 0.4 mag; for these, the fraction of measurements contributing to the high-amplitude variability ranges constantly from about 5% to 80%. Blazar variability has some similarities to that of type I quasi-stellar objects (QSOs) but includes larger amplitude fluctuations on all timescales. FSRQ variability amplitudes are particularly similar to those of QSOs on timescales of several months, suggesting significant contributions from the accretion disk to the variable flux at these timescales. Optical variability amplitudes are correlated with the maximum apparent velocities of the radio jet for the subset of FSRQs with MOJAVE Very Long Baseline Array measurements, implying that the optically variable flux's strength is typically related to that of the radio emission. We also study CRATES radio-selected FSRQ candidates, which show similar variability characteristics to known FSRQs; this suggests a high purity for the CRATES sample.

  11. Fast γ-Ray Variability in Blazars beyond Redshift 3

    Science.gov (United States)

    Li, Shang; Xia, Zi-Qing; Liang, Yun-Feng; Liao, Neng-Hui; Fan, Yi-Zhong

    2018-02-01

    High-redshift blazars are one of the most powerful sources in the universe and γ-ray variability carries crucial information about their relativistic jets. In this work we present results of the first systematical temporal analysis of Fermi-LAT data of all known seven γ-ray blazars beyond redshift 3. Significant long-term γ-ray variability is found from five sources in monthly γ-ray light curves, in which three of them are reported for the first time. Furthermore, intraday γ-ray variations are detected from NVSS J053954‑283956 and NVSS J080518+614423. The doubling variability timescale of the former source is limited as short as ≲1 hr (at the source frame). Together with variability amplitude over one order of magnitude, NVSS J053954‑283956 is the most distant γ-ray flaring blazar so far. Meanwhile, intraday optical variability of NVSS J163547+362930 is found based on an archival PTF/iPTF light curve. Benefiting from the multi-wavelength activity of these sources, constraints on their Doppler factors, as well as the locations of the γ-ray radiation region and indications for the SDSS high redshift jetted active galactic nuclei deficit are discussed.

  12. Correlation between γ-Ray and Radio Bands for γ-Ray Loud Blazars ...

    Indian Academy of Sciences (India)

    Abstract. 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 γ-ray loud blazars with available γ-ray and radio (core and total) data. It is interesting that the γ-ray luminosity have a good correlation with the radio ...

  13. UV and X-ray Variability of Blazars Alok C. Gupta

    Indian Academy of Sciences (India)

    Abstract. 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 ...

  14. Correlation between γ-Ray and Radio Bands for γ-Ray Loud Blazars ...

    Indian Academy of Sciences (India)

    J. H. Fan & S. H. Li. Centre for Astrophysics, Guangzhou University, Guangzhou 510006, China. ∗ e-mail: dxwuhl@gmail.com. Abstract. 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 γ-ray loud blazars with ...

  15. In Like a Lamb, Out Like a Lion: Probing the Disk-Jet Connection in Fermi Gamma-ray Bright Blazars

    Science.gov (United States)

    Isler, Jedidah C.

    Blazars are active galactic nuclei whose relativistic jet is aligned at small angles (detected, making them an ideal laboratory to study the energetics of infalling and outflowing material. The simultaneously obtained multiwavelength, long-term data analyzed here help to better evaluate the impact of jet power on the broadband spectral energy distributions of these sources via the OIR color variability analysis. Secondly, emission line variability studies presented here can help constrain the location of the gamma-emitting region as well set preliminary constraints on the minimum jet contribution necessary to significantly increase the photoionizing flux in the broad line region. I briefly discuss the main findings of this dissertation below. The optical and infrared (OIR) light curves and color variability diagrams for a sample of 12 blazars are presented. I analyze the OIR color variability of these blazars from 2011 - 2013, comparing their OIR properties to the jet state via Fermi gamma-ray fluxes obtained on a similar cadence. This project also assesses long-term color variability by extending the temporal baseline of 6 blazars to 5 years, allowing the comparison of the color variability in the same source at different jet states. Using the slope of the color variability diagram, we propose that the existing dichotomy between FSRQ (redder when brighter) and BLL (bluer when brighter) color variability be reconsidered as a continuum of jet (versus disk) activity, in which blazars can achieve either color variability response depending on jet power. This allows a self-consistent description of the changes in OIR color variability in the same source over time, as well as the OIR color variability in a sample of blazars over time. The second topic of the dissertation is the emission line variability properties of a sample of 7 blazars. We compare the emission line variability with Fermi gamma-ray flux and optical linear polarized flux to estimate its relationship to

  16. 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

  17. EXTENDED RADIO EMISSION IN MOJAVE BLAZARS: CHALLENGES TO UNIFICATION

    International Nuclear Information System (INIS)

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

    2010-01-01

    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 A, 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

  18. The radio-γ-ray connection in Fermi blazars

    Science.gov (United States)

    Ghirlanda, G.; Ghisellini, G.; Tavecchio, F.; Foschini, L.; Bonnoli, G.

    2011-05-01

    We study the correlation between the γ-ray flux (Fγ), averaged over the first 11 months of the Fermi survey and integrated above 100 MeV, and the radio flux density (Fr at 20 GHz) of Fermi sources associated with a radio counterpart in the 20-GHz Australia Telescope Compact Array (AT20G) survey. Considering the blazars detected in both bands, the correlation is highly significant and has the form Fγ∝F0.85±0.04r, similar to BL Lacertae objects and flat-spectrum radio quasars. However, only a small fraction (˜1/15) of the AT20G radio sources with flat radio spectra are detected by Fermi. To understand if this correlation is real, we examine the selection effects introduced by the flux limits of both the radio and the γ-ray surveys, and the importance of variability of the γ-ray flux. After accounting for these effects, we find that the radio-γ-ray flux correlation is real, but its slope is steeper than the observed one, that is, Fγ∝Fδr with δ in the range 1.25-1.5. The observed Fγ-Fr correlation and the fraction of radio sources detected by Fermi are reproduced assuming a long-term γ-ray flux variability, following a lognormal probability distribution with standard deviation σ≥ 0.5 (corresponding to Fγ varying by at least a factor of 3). Such a variability is compatible, even if not necessarily equal, with what is observed when comparing, for the sources in common, the EGRET and the Fermi γ-ray fluxes (even if the Fermi fluxes are averaged over ˜1 yr). Another indication of variability is the non-detection of 12 out of 66 EGRET blazars by Fermi, despite its higher sensitivity. We also study the strong linear correlation between the γ-ray and the radio luminosity of the 144 AT20G-Fermi associations with known redshift and show, through partial correlation analysis, that it is statistically robust. Two possible implications of these correlations are discussed: the contribution of blazars to the extragalactic γ-ray background and the prediction

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

    Science.gov (United States)

    Adrian-Martinez, S.; Albert, A.; André, M.; Anton, G.; Ardid, M.; Aubert, J. J.; Baret, B.; Barrios, J.; Basa, S.; Gehrels, N.; hide

    2015-01-01

    Context. 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. Objects like these are prime candidates to be the source of the highest-energy cosmic rays, and thus of associated neutrino emission. Aims. We present an analysis of neutrino emission from the six blazars using observations with the ANTARES neutrino telescope. Methods. 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 di erent possible source neutrino spectra. A maximum-likelihood approach, using the reconstructed energies and arrival directions of through-going muons, is used to identify events with properties consistent with a blazar origin. Results. Both blazars predicted to be the most neutrino-bright in the TANAMI sample (1653-329 and 1714-336) have a signal flux fitted by the likelihood analysis corresponding to approximately one event. This observation is consistent with the blazar-origin hypothesis of the IceCube event IC 14 for a broad range of blazar spectra, although an atmospheric origin cannot be excluded. No ANTARES events are observed from any of the other four blazars, including the three associated with IceCube event IC20. This excludes at a 90% confidence level the possibility that this event was produced by these blazars unless the neutrino spectrum is flatter than -2.4.

  20. On the Direct Correlation between Gamma-Rays and PeV Neutrinos from Blazars

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Shan; Pohl, Martin; Winter, Walter, E-mail: shan.gao@desy.de [Deutsches Elektronen-Synchrotron (DESY), Platanenallee 6, D-15738 Zeuthen (Germany)

    2017-07-10

    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 to 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 a subdominant 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 demonstrate that the time-wise correlation between the neutrino event and burst phase is weak.

  1. Bulk Comptonization: new hints from the luminous blazar 4C+25.05

    Science.gov (United States)

    Kammoun, E. S.; Nardini, E.; Risaliti, G.; Ghisellini, G.; Behar, E.; Celotti, A.

    2018-01-01

    Blazars are often characterized by a spectral break at soft X-rays, whose origin is still debated. While most sources show a flattening, some exhibit a blackbody-like soft excess with temperatures of the order of ∼0.1 keV, similar to low-luminosity, non-jetted Seyferts. Here, we present the analysis of the simultaneous XMM-Newton and NuSTAR observations of the luminous flat-spectrum radio quasar 4C+25.05 (z = 2.368). The observed 0.3-30 keV spectrum is best described by the sum of a hard X-ray power law (Γ = 1.38_{-0.03}^{+0.05}) and a soft component, approximated by a blackbody with kT_BB = 0.66_{-0.04}^{+0.05} keV (rest frame). If the spectrum of 4C+25.05 is interpreted in the context of bulk Comptonization by cold electrons of broad-line region photons emitted in the direction of the jet, such an unusual temperature implies a bulk Lorentz factor of the jet of Γbulk ∼ 11.7. Bulk Comptonization is expected to be ubiquitous on physical grounds, yet no clear signature of it has been found so far, possibly due to its transient nature and the lack of high-quality, broad-band X-ray spectra.

  2. A Model of Polarisation Rotations in Blazars from Kink Instabilities in Relativistic Jets

    Directory of Open Access Journals (Sweden)

    Krzysztof Nalewajko

    2017-10-01

    Full Text Available This paper presents a simple model of polarisation rotation in optically thin relativistic jets of blazars. The model is based on the development of helical (kink mode of current-driven instability. A possible explanation is suggested for the observational connection between polarisation rotations and optical/gamma-ray flares in blazars, if the current-driven modes are triggered by secular increases of the total jet power. The importance of intrinsic depolarisation in limiting the amplitude of coherent polarisation rotations is demonstrated. The polarisation rotation amplitude is thus very sensitive to the viewing angle, which appears to be inconsistent with the observational estimates of viewing angles in blazars showing polarisation rotations. Overall, there are serious obstacles to explaining large-amplitude polarisation rotations in blazars in terms of current-driven kink modes.

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

    Energy Technology Data Exchange (ETDEWEB)

    Ruan, John J.; Anderson, Scott F.; MacLeod, Chelsea L.; Becker, Andrew C.; Davenport, James R. A.; Ivezic, Zeljko [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Burnett, T. H. [Department of Physics, University of Washington, Seattle, WA 98195-1560 (United States); Kochanek, Christopher S. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Plotkin, Richard M. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Sesar, Branimir [Division of Physics, Mathematics and Astronomy, Caltech, Pasadena, CA 91125 (United States); Stuart, J. Scott, E-mail: jruan@astro.washington.edu [Lincoln Laboratory, Massachusetts Institute of Technology, 244 Wood Street, Lexington, MA 02420-9108 (United States)

    2012-11-20

    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 {approx}30% of {gamma}-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 {tau}, and driving amplitudes on short timescales {sigma}-circumflex. Imposing cuts on minimum {tau} and {sigma}-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 {gamma}-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 {gamma}-ray blazars and is likely to be the {gamma}-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 {approx}3 years in the rest frame of the jet, in contrast with the {approx}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.

  4. 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.

  5. SYSTEMATIC STUDY OF GAMMA-RAY-BRIGHT BLAZARS WITH OPTICAL POLARIZATION AND GAMMA-RAY VARIABILITY

    Energy Technology Data Exchange (ETDEWEB)

    Itoh, Ryosuke; Fukazawa, Yasushi; Kanda, Yuka; Shiki, Kensei; Kawabata, Miho; Nakaoka, Tatsuya; Takaki, Katsutoshi; Takata, Koji; Ui, Takahiro [Department of Physical Science, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Nalewajko, Krzysztof; Madejski, Greg M. [Kavli Institute for Particle Astrophysics and Cosmology, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road M/S 29, Menlo Park, CA 94025 (United States); Uemura, Makoto; Tanaka, Yasuyuki T.; Kawabata, Koji S.; Akitaya, Hiroshi; Ohsugi, Takashi [Hiroshima Astrophysical Science Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Schinzel, Frank K. [Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM 87131 (United States); Moritani, Yuki [Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study, The University of Tokyo, Kashiwa, Chiba 277-8583 (Japan); Sasada, Mahito [Institute for Astrophysical Research, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States); Yamanaka, Masayuki, E-mail: itoh@hep01.hepl.hiroshima-u.ac.jp, E-mail: itoh@hp.phys.titech.ac.jp [Department of Physics, Faculty of Science and Engineering, Konan University, Okamoto, Kobe, Hyogo 658-8501 (Japan); and others

    2016-12-10

    Blazars are highly variable active galactic nuclei that 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 2008 July and 2014 December 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), this result implies a systematic difference in the intrinsic alignment of magnetic fields in parsec-scale relativistic jets between different types of blazars (flat-spectrum radio quasars vs. BL Lacs) and consequently between different types of radio galaxies (FR I versus FR II).

  6. Multifrequency Photo-polarimetric WEBT Observation Campaign on the Blazar S5 0716+714: Source Microvariability and Search for Characteristic Timescales

    Science.gov (United States)

    Bhatta, G.; Stawarz, Ł.; Ostrowski, M.; Markowitz, A.; Akitaya, H.; Arkharov, A. A.; Bachev, R.; Benítez, E.; Borman, G. A.; Carosati, D.; Cason, A. D.; Chanishvili, R.; Damljanovic, G.; Dhalla, S.; Frasca, A.; Hiriart, D.; Hu, S.-M.; Itoh, R.; Jableka, D.; Jorstad, S.; Jovanovic, M. D.; Kawabata, K. S.; Klimanov, S. A.; Kurtanidze, O.; Larionov, V. M.; Laurence, D.; Leto, G.; Marscher, A. P.; Moody, J. W.; Moritani, Y.; Ohlert, J. M.; Di Paola, A.; Raiteri, C. M.; Rizzi, N.; Sadun, A. C.; Sasada, M.; Sergeev, S.; Strigachev, A.; Takaki, K.; Troitsky, I. S.; Ui, T.; Villata, M.; Vince, O.; Webb, J. R.; Yoshida, M.; Zola, S.

    2016-11-01

    Here we report on the results of the Whole Earth Blazar Telescope photo-polarimetric campaign targeting the blazar S5 0716+71, organized in 2014 March to monitor the source simultaneously in BVRI and near-IR filters. The campaign resulted in an unprecedented data set spanning ∼110 hr of nearly continuous, multiband observations, including two sets of densely sampled polarimetric data mainly in the R filter. During the campaign, the source displayed pronounced variability with peak-to-peak variations of about 30% and “bluer-when-brighter” spectral evolution, consisting of a day-timescale modulation with superimposed hour-long microflares characterized by ∼0.1 mag flux changes. We performed an in-depth search for quasi-periodicities in the source light curve; hints for the presence of oscillations on timescales of ∼3 and ∼5 hr do not represent highly significant departures from a pure red-noise power spectrum. We observed that, at a certain configuration of the optical polarization angle (PA) relative to the PA of the innermost radio jet in the source, changes in the polarization degree (PD) led the total flux variability by about 2 hr; meanwhile, when the relative configuration of the polarization and jet angles altered, no such lag could be noted. The microflaring events, when analyzed as separate pulse emission components, were found to be characterized by a very high PD (>30%) and PAs that differed substantially from the PA of the underlying background component, or from the radio jet positional angle. We discuss the results in the general context of blazar emission and energy dissipation models. ).

  7. MULTIFREQUENCY PHOTO-POLARIMETRIC WEBT OBSERVATION CAMPAIGN ON THE BLAZAR S5 0716+714: SOURCE MICROVARIABILITY AND SEARCH FOR CHARACTERISTIC TIMESCALES

    Energy Technology Data Exchange (ETDEWEB)

    Bhatta, G.; Stawarz, Ł.; Ostrowski, M. [Astronomical Observatory of Jagiellonian University, ul. Orla 171, 30-244 Krakow (Poland); Markowitz, A. [Center for Astrophysics and Space Sciences, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0424 (United States); Akitaya, H. [Hiroshima Astrophysical Science Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Arkharov, A. A. [Main (Pulkovo) Astronomical Observatory of RAS, Pulkovskoye shosse, 60, 196140 St. Petersburg (Russian Federation); Bachev, R. [Institute of Astronomy, Bulgarian Academy of Sciences, 72, Tsarigradsko Shosse Blvd., 1784 Sofia (Bulgaria); Benítez, E. [Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico DF (Mexico); Borman, G. A. [Crimean Astrophysical Observatory, P/O Nauchny, Crimea, 298409 (Russian Federation); Carosati, D. [EPT Observatories, Tijarafe, La Palma (Spain); Cason, A. D. [Private address, 105 Glen Pine Trail, Dawnsonville, GA 30534 (United States); Chanishvili, R. [Abastumani Observatory, Mt. Kanobili, 0301 Abastumani, Georgia (United States); Damljanovic, G. [Astronomical Observatory, Volgina 7, 11060 Belgrade (Serbia); Dhalla, S. [Florida International University, Miami, FL 33199 (United States); Frasca, A. [INAF—Osservatorio Astrofisico di Catania (Italy); Hiriart, D. [Instituto de Astronomía, Universidad Nacional Autónoma de México, Ensenada (Mexico); Hu, S-M., E-mail: gopalbhatta716@gmail.com [Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, Institute of Space Sciences, Shandong University at Weihai, 264209 Weihai (China); and others

    2016-11-01

    Here we report on the results of the Whole Earth Blazar Telescope photo-polarimetric campaign targeting the blazar S5 0716+71, organized in 2014 March to monitor the source simultaneously in BVRI and near-IR filters. The campaign resulted in an unprecedented data set spanning ∼110 hr of nearly continuous, multiband observations, including two sets of densely sampled polarimetric data mainly in the R filter. During the campaign, the source displayed pronounced variability with peak-to-peak variations of about 30% and “bluer-when-brighter” spectral evolution, consisting of a day-timescale modulation with superimposed hour-long microflares characterized by ∼0.1 mag flux changes. We performed an in-depth search for quasi-periodicities in the source light curve; hints for the presence of oscillations on timescales of ∼3 and ∼5 hr do not represent highly significant departures from a pure red-noise power spectrum. We observed that, at a certain configuration of the optical polarization angle (PA) relative to the PA of the innermost radio jet in the source, changes in the polarization degree (PD) led the total flux variability by about 2 hr; meanwhile, when the relative configuration of the polarization and jet angles altered, no such lag could be noted. The microflaring events, when analyzed as separate pulse emission components, were found to be characterized by a very high PD (>30%) and PAs that differed substantially from the PA of the underlying background component, or from the radio jet positional angle. We discuss the results in the general context of blazar emission and energy dissipation models.

  8. 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.

  9. The VLBA-BU-BLAZAR Multi-Wavelength Monitoring Program

    Directory of Open Access Journals (Sweden)

    Svetlana Jorstad

    2016-10-01

    Full Text Available We describe a multiwavelength program of monitoring of a sample of bright γ-ray blazars, which the Boston University (BU group has being carrying out since June 2007. The program includes monthly monitoring with the Very Long Baseline Array at 43 GHz, optical photometric and polarimetric observations, construction and analysis of UV and X-ray light curves obtained with the Rossi X-ray Timing Explorer (RXTE and Swift satellites, and construction and analysis of γ-ray light curves based on data provided by the Large Area Telescope of the Fermi Gamma-ray Space Telescope. We present general results about the kinematics of parsec-scale radio jets, as well as the connection between γ-ray outbursts and jet events.

  10. Adaptive Spectral Doppler Estimation

    DEFF Research Database (Denmark)

    Gran, Fredrik; Jakobsson, Andreas; Jensen, Jørgen Arendt

    2009-01-01

    . The methods can also provide better quality of the estimated power spectral density (PSD) of the blood signal. Adaptive spectral estimation techniques are known to pro- vide good spectral resolution and contrast even when the ob- servation window is very short. The 2 adaptive techniques are tested......In this paper, 2 adaptive spectral estimation techniques are analyzed for spectral Doppler ultrasound. The purpose is to minimize the observation window needed to estimate the spectrogram to provide a better temporal resolution and gain more flexibility when designing the data acquisition sequence...... and compared with the averaged periodogram (Welch’s method). The blood power spectral capon (BPC) method is based on a standard minimum variance technique adapted to account for both averaging over slow-time and depth. The blood amplitude and phase estimation technique (BAPES) is based on finding a set...

  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. Broad Band Spectral Index TeV Blazars Detected by Fermi LAT

    Indian Academy of Sciences (India)

    Since January 2016, the Journal of Astrophysics and Astronomy has moved to Continuous Article Publishing (CAP) mode. This means that each accepted article is being published immediately online with DOI and article citation ID with starting page number 1. Articles are also visible in Web of Science immediately.

  13. Spectral Energy Distributions of SDSS Blazars H. Z. Li & L. E. Chen

    Indian Academy of Sciences (India)

    Physics Department, Yuxi Normal University, Yuxi 653100, People's Republic of China. ∗ e-mail: lhz@yxnu.net; chenle@yxnu.net. Abstract. We compiled the radio, optical and X-ray data for ... in the history of astronomy. Based on the sample of Plotkin et al. (2008) and Chen et al. (2009), we compiled a large sample of 686 ...

  14. Polarization and brightness of the blazar S5 0716+714 in 1991-2004

    Science.gov (United States)

    Doroshenko, V. T.; Kiselev, N. N.

    2017-06-01

    We investigate the photometric and polarimetric behavior of the blazar S5 0716+714 based on the observations carried out in 1991-2004 at the 125-cm Crimean Astrophysical Observatory telescope (AZT11) with a photopolarimeter that allows simultaneous polarization and brightness measurements to be made in the U BV RI bands. We also provide the U BV photometry for the blazar obtained in 2000-2009 with a 60-cm telescope at the Crimean Station of the Sternberg Astronomical Institute. The pattern of flux variability and the correlation between the brightness, color, and polarization variations have been investigated. In this time interval the blazar showed a significant brightness and polarization variability similar to noise processes.

  15. Long-term monitoring of blazars - the DWARF network

    Science.gov (United States)

    Backes, Michael; Biland, Adrian; Boller, Andrea; Braun, Isabel; Bretz, Thomas; Commichau, Sebastian; Commichau, Volker; Dorner, Daniela; von Gunten, Hanspeter; Gendotti, Adamo; Grimm, Oliver; Hildebrand, Dorothée; Horisberger, Urs; Krähenbühl, Thomas; Kranich, Daniel; Lustermann, Werner; Mannheim, Karl; Neise, Dominik; Pauss, Felicitas; Renker, Dieter; Rhode, Wolfgang; Rissi, Michael; Rollke, Sebastian; Röser, Ulf; Stark, Luisa Sabrina; Stucki, Jean-Pierre; Viertel, Gert; Vogler, Patrick; Weitzel, Quirin

    The variability of the very high energy (VHE) emission from blazars seems to be connected with the feeding and propagation of relativistic jets and with their origin in supermassive black hole binaries. The key to understanding their properties is measuring well-sampled gamma-ray lightcurves, revealing the typical source behavior unbiased by prior knowledge from other wavebands. Using ground-based gamma-ray observatories with exposures limited by dark-time, a global network of several telescopes is needed to carry out fulltime measurements. Obviously, such observations are time-consuming and, therefore, cannot be carried out with the present state of the art instruments. The DWARF telescope on the Canary Island of La Palma is dedicated to monitoring observations. It is currently being set up, employing a costefficient and robotic design. Part of this project is the future construction of a distributed network of small telescopes. The physical motivation of VHE long-term monitoring will be outlined in detail and the perspective for a network for 24/7 observations will be presented.

  16. Search for neutrino emission from gamma-ray flaring blazars with the ANTARES telescope

    NARCIS (Netherlands)

    Adrian-Martinez, S.; Al Samarai, I.; Albert, A.; Andre, 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.; Carloganu, C.; Carminati, G.; Carr, J.; Cecchini, S.; Charif, Z.; Charvis, P.; 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.; Enzenhofer, A.; Ernenwein, J.P.; Escoffier, S.; Fehn, K.; Fermani, P.; Ferri, M.; Ferry, S.; Flaminio, V.; Folger, F.; Fritsch, U.; Fuda, J.L.; Galata, S.; Gay, P.; Geyer, K.; Giacomelli, G.; Giordano, V.; Gomez-Gonzalez, J.P.; Graft, K.; Guillard, G.; Halladjian, G.; Hallewell, G.; van Haren, H.; Hartman, J.; Heijboer, A.J.; Hello, Y.; Hernandez-Rey, J.J.; Herold, B.; Hoessl, 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.; Lefevre, D.; Lim, G.; Lo Presti, D.; Loehner, H.; Loucatos, S.; Louis, F.; Mangano, S.; Marcelin, M.; Margiotta, A.; Martinez-Mora, J.A.; Meli, A.; Montaruli, T.; Morganti, N.; Moscoso, L.; Motz, H.; Neff, M.; Nezri, E.; Palioselitis, D.; Pavalas, 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.; Riviere, C.; Robert, A.; Roensch, K.; Rostovtsev, A.; Ruiz-Rivas, J.; Rujoiu, M.; Russo, G.V.; Salesa, F.; Samtleben, D.F.E.; Sapienza, P.; Schock, F.; Schuller, J.P.; Schussler, F.; Seitz, T.; Shanidze, R.; Simeone, F.; Spies, A.; Spurio, M.; Steijger, J.J.M.; Stolarczyk, T.; Sanchez-Losa, A.; Taiuti, M.; Tamburini, C.; Toscano, S.; Vallage, B.; Vallee, 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.; Zuniga, J.

    2012-01-01

    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,

  17. ANTARES constrains a blazar origin of two IceCube PeV neutrino events - Letter

    NARCIS (Netherlands)

    Adrián-Martínez, S.; et al., [Unknown; Bruijn, R.; Kooijman, P.; Palioselitis, D.; de Wolf, E.

    2015-01-01

    Context. 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. Objects like

  18. Multi-Wavelength Variability Properties of Fermi Blazar S5 0716+ ...

    Indian Academy of Sciences (India)

    2Key Laboratory for the Structure and Evolution of Celestial Objects, Yunnan Astronomical. Observatory, Chinese ... Blazars, including flat spectrum radio quasars and BL Lacertae objects are radio- loud active galactic ... interpreted by the relativistic jet oriented close to the line-of-sight (Blandford & Rees. 1978). But the ...

  19. Relativistic Beaming Effect in Fermi Blazars J. H. Fan1,2,∗ , D ...

    Indian Academy of Sciences (India)

    However, all of the discus- sions are based on the lower energetic bands, the radio Doppler factor, the radio polarization, the brightness temperature, and the superluminal motions. It is known that the Doppler factors are important in the discussion of blazars. So, if one can determine the Doppler factor in the γ-ray region, ...

  20. Models for High-Energy Radiation from Blazars G. E. Romero1 ...

    Indian Academy of Sciences (India)

    Key words. Blazars—radiation mechanisms: non-thermal—jets. 1. Introduction. The unification paradigm for Active Galactic Nuclei (AGN) suggests that different observational properties of these objects are basically due to the different angles of observations (e.g., Urry & Padovani 1995). Blazars are the AGN in which the jet.

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

    Indian Academy of Sciences (India)

    Blazars display rapid variability across the entire electromagnetic spectrum. Vari- ability at high energies on timescales of a few minutes has been observed for some of them, such as PKS 2155−304 (e.g., Aharonian et al. 2007). This discovery has led to the formulation of a large variety of models for non-thermal variability in ...

  2. Multi-Frequency Observations of Gamma-Ray Blazar 1633+382 SG ...

    Indian Academy of Sciences (India)

    Gamma-rays—quasars: 1633+382(4C+38.41)—radio jets— polarization. 1. Introduction. Blazars are the most numerous objects in the γ-ray sky (Abdo et al. 2010). They show dramatic variability across the electromagnetic spectrum (e.g., Jorstad et al. 2010; Marscher et al. 2010). Both these properties (strong γ-ray emission.

  3. Models for High-Energy Radiation from Blazars G. E. Romero1 ...

    Indian Academy of Sciences (India)

    Abstract. 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 ...

  4. γ-Ray Emission from the Extreme Blazar 1ES 0229+200 J. Li, T ...

    Indian Academy of Sciences (India)

    Abstract. 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 ...

  5. Estimating Black Hole Masses of Blazars Xue-Bing Wu1,∗ , FK Liu1 ...

    Indian Academy of Sciences (India)

    only for nearby sources. We have to seek other methods for most blazars because the velocity dispersions of their host galaxies are too difficult to be measured. In this paper, we report our progress on estimating the black hole masses of radio- loud AGNs using a new BLR size–Hβ emission line luminosity relation and the.

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

    Indian Academy of Sciences (India)

    Key words. Active galactic nuclei: blazars—radio continuum: variability— γ-ray: Fermi-LAT. 1. Model-fit and statistical analysis. We compiled a sample of 104 ... Position Angle Changes of Inner-Jets of Blazars. 395. Table 1. Statistics of correlations of IF vs. PA in G1. (1). (2). (3). (4). Class. N. Positive corr. Negative corr.

  7. γ-Rays Radiation of High Redshift Fermi Blazars WG Liu1, SH Fu2 ...

    Indian Academy of Sciences (India)

    γ-Rays Radiation of High Redshift Fermi Blazars. W. G. Liu1, S. H. Fu2, X. Zhang1, L. Ma1,∗. , Y. B. Li1 & D. R. Xiong1. 1Department of Physics, Yunnan Normal University, Kunming 650500, China. 2Yunnan Entry-Exit Inspection and Quarantine Bureau, Kunming 650228, China. ∗ e-mail: astromali@126.com. Abstract.

  8. Multi-Wavelength Variability Properties of Fermi Blazar S5 0716+ ...

    Indian Academy of Sciences (India)

    interpreted by the relativistic jet oriented close to the line-of-sight (Blandford & Rees. 1978). But the radiation process of blazars is still an open question. Researching .... Innovation Promotion Association, CAS. References. Abdo, A. A. et al. 2011, ApJ, 730, 101. Aller, M. F., Aller, H. D., Hughes, P. A., Latimer, G. A. 1999, ApJ, ...

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

    Indian Academy of Sciences (India)

    Position Angle Changes of Inner-Jets in a Sample of Blazars. Ligong Mi1,3,∗ & Xiang Liu1,2. 1Xinjiang Astronomical Observatory, CAS, 150 Science 1-Street, Urumqi 830011,. People's Republic of China. 2Key Laboratory of Radio Astronomy, CAS, Nanjing 210008, People's Republic of China. 3University of Chinese ...

  10. VLA Radio Observations of the blazar TXS 0506+056 associated with the IceCube-170922A neutrino event

    Science.gov (United States)

    Tetarenko, A. J.; Sivakoff, G. R.; Kimball, A. E.; Miller-Jones, J. C. A.

    2017-10-01

    We report VLA radio observations of the blazar TXS 0506+056, following its identification as the potential astrophysical origin of the extremely high energy neutrino event IceCube-170922A (GCN #21916).

  11. ROXA: a new multi-frequency large sample of blazars selected with SDSS and 2dF optical spectroscopy

    Science.gov (United States)

    Turriziani, S.; Cavazzuti, E.; Giommi, P.

    2007-09-01

    Context: Although blazars make of a small fraction of the overall AGN population, they are expected to be the dominant population of extragalactic sources in the hard X-ray and gamma-ray bands and have been shown to be the largest contaminant of CMB fluctuation maps. So far the number of known blazars is of the order of several hundreds, but the forthcoming AGILE, GLAST and Planck space observatories will detect several thousand objects of this type. Aims: In preparation for these missions it is necessary to identify new samples of blazars to study their multi-frequency characteristics and statistical properties. Methods: We compiled a sample of objects with blazar-like properties via a cross-correlation between large radio (NVSS, ATCAPMN) and X-ray surveys (RASS) using the SDSS-DR4 and 2dF survey data to spectroscopically identify our candidates and test the validity of the selection method. Results: We present the Radio-Optical-X-ray catalog built at ASDC (ROXA), a list of 816 objects among which 510 are confirmed blazars. Only 19% of the candidates were certain non-blazars, demonstrating the high efficiency of our selection method. Conclusions: Our catalog includes 173 new blazar identifications, or about 10% of all presently known blazars. The relatively high flux threshold in the X-ray energy band (given by the RASS survey) preferentially selects objects with high f_x/fr ratio leading to the discovery of new High Energy Peaked BL Lac (HBLs). Our catalog therefore includes many new potential targets for GeV-TeV observations. The catalog is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/472/699

  12. BL Lacertae Objects Beyond Redshift 1.3 - UV-to-NIR Photometry and Photometric Redshift for Fermi/LAT Blazars

    Science.gov (United States)

    Rau, A.; Schady, P.; Greiner, J.; Salvato, M.; Ajello, M.; Bottacini, E.; Gehrels, N.; Afonso, P. M. J.; Elliott, J.; Filgas, R.; hide

    2011-01-01

    Context. Observations of the gamma-ray sky with Fermi led to significant advances towards understanding blazars, the most extreme class of Active Galactic Nuclei. A large fraction of the population detected by Fermi is formed by BL Lacertae (BL Lac) objects, whose sample has always suffered from a severe redshift incompleteness due to the quasi-featureless optical spectra. Aims. Our goal is to provide a significant increase of the number of confirmed high-redshift BL Lac objects contained in the 2 LAC Fermi/LAT catalog. Methods. For 103 Fermi/LAT blazars, photometric redshifts using spectral energy distribution fitting have been obtained. The photometry includes 13 broad-band filters from the far ultraviolet to the near-IR observed with Swift/UVOT and the multi-channel imager GROND at the MPG/ESO 2.2m telescope. Data have been taken quasi-simultaneously and the remaining source-intrinsic variability has been corrected for. Results. We release the UV-to-near-IR 13-band photometry for all 103 sources and provide redshift constraints for 75 sources without previously known redshift. Out of those, eight have reliable photometric redshifts at z > or approx. 1.3, while for the other 67 sources we provide upper limits. Six of the former eight are BL Lac objects, which quadruples the sample of confirmed high-redshift BL Lac. This includes three sources with redshifts higher than the previous record for BL Lac, including CRATES J0402-2615, with the best-fit solution at z approx. = 1.9.

  13. Substitution dynamical systems spectral analysis

    CERN Document Server

    Queffélec, Martine

    2010-01-01

    This volume mainly deals with the dynamics of finitely valued sequences, and more specifically, of sequences generated by substitutions and automata. Those sequences demonstrate fairly simple combinatorical and arithmetical properties and naturally appear in various domains. As the title suggests, the aim of the initial version of this book was the spectral study of the associated dynamical systems: the first chapters consisted in a detailed introduction to the mathematical notions involved, and the description of the spectral invariants followed in the closing chapters. This approach, combined with new material added to the new edition, results in a nearly self-contained book on the subject. New tools - which have also proven helpful in other contexts - had to be developed for this study. Moreover, its findings can be concretely applied, the method providing an algorithm to exhibit the spectral measures and the spectral multiplicity, as is demonstrated in several examples. Beyond this advanced analysis, many...

  14. 3 mm GMVA Observations of Total and Polarized Emission from Blazar and Radio Galaxy Core Regions

    Directory of Open Access Journals (Sweden)

    Carolina Casadio

    2017-10-01

    Full Text Available We present total and linearly polarized 3 mm Global mm-VLBI Array (GMVA; mm-VLBI: Very Long Baseline Interferometry observations at millimetre wavelengths images of a sample of blazars and radio galaxies from the VLBA-BU-BLAZAR 7 mm monitoring program designed to probe the innermost regions of active galactic nuclei (AGN jets and locate the sites of gamma-ray emission observed by the Fermi-LAT. The lower opacity at 3 mm and improved angular resolution—on the order of 50 microarcseconds—allow us to distinguish features in the jet not visible in the 7 mm VLBA data. We also compare two different methods used for the calibration of instrumental polarisation and we analyze the resulting images for some of the sources in the sample.

  15. Gamma-ray astronomy from the ground and the space: first analyses of the HESS-II hybrid array and search for blazar candidates among the unidentified Fermi-LAT sources

    International Nuclear Information System (INIS)

    Lefaucheur, Julien

    2015-01-01

    This manuscript is about high energy gamma-ray astronomy (between 30 GeV and 300 GeV) with the Fermi-LAT satellite and very high energy gamma-ray astronomy (above ∼100 GeV) via the H.E.S.S. experiment. The second phase of the H.E.S.S. experiment began in July 2012 with the inauguration of a fifth 28 m-diameter telescope added to the initial array composed of four 12 m-diameter imaging atmospheric Cherenkov telescopes. In the first part of this thesis, we present the development of an analysis in hybrid mode based on a multivariate method dedicated to detect and study sources with different spectral shapes and the first analysis results on real data. The second part is dedicated to the research of blazar candidates among the Fermi-LAT unidentified sources of the 2FGL catalog. A first development is based on a multivariate approach using discriminant parameters built with the 2FGL catalog parameters. A second development is done with the use of the WISE satellite catalog and a non-parametric technic in order to find the blazar-like infrared counterparts of the unidentified sources of the 2FGL catalog. (author)

  16. The WEBT Campaign on the Blazar 3C 279 in 2006

    Czech Academy of Sciences Publication Activity Database

    Böttcher, M.; Basu, S.; Joshi, M.; Villata, M.; Arai, A.; Aryan, N.; Asfandiyarov, I. M.; Bach, U.; Bachev, R.; Berdyugin, A.; Blažek, Martin; Buemi, C.S.; Castro-Tirado, A.J.; de Ugarte Postigo, A.; Frasca, A.; Fuhrmann, L.; Hagen-Thorn, V.A.; Henson, G.; Hovatta, T.; Hudec, René; Ibrahimov, M.A.; Ishii, Y.; Ivanidze, R.; Jelínek, M.; Kamada, M.; Kapanadze, B.; Katsuura, M.; Kotaka, D.; Kovalev, Y.Y.; Kovalev, Yu.A.; Kubánek, Petr; Kurosaki, M.; Kurtanidze, O.M.; Lähteenmäki, A.; Lanteri, L.; Larionov, V.M.; Larionova, L.; Lee, C.-U.; Leto, P.; Lindfors, E.; Marilli, E.; Marshall, K.; Miller, H.R.; Mingaliev, M.G.; Mirabal, N.; Mizoguchi, S.; Nakamura, K.; Nieppola, E.; Nikolashvili, M.G.; Nilsson, K.; Nishiyama, S.; Ohlert, J.M.; Osterman, M.A.; Pak, S.; Pasanen, M.; Peters, C.S.; Pursimo, T.; Raiteri, C.M.; Robertson, J.; Robertson, T.; Ryle, W.T.; Sadakane, K.; Sadun, A.C.; Sigua, L.A.; Sohn, B.-W.; Strigachev, A.; Sumitomo, N.; Takalo, L.O.; Tamesue, Y.; Tanaka, K.; Thorstensen, J.R.; Tosti, G.; Trigilio, C.; Umana, G.; Vennes, S.; Vítek, S.; Volvach, A.; Webb, J.; Yamanaka, M.; Yim, S.-H.

    2007-01-01

    Roč. 670, č. 2 (2007), s. 968-977 ISSN 0004-637X Grant - others:EU(XE) ESA-PECS project No. 98023 Institutional research plan: CEZ:AV0Z10030501 Source of funding: V - iné verejné zdroje Keywords : blazars * active galactic nuclei Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 6.405, year: 2007

  17. 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.

  18. The Electrostatic Instability for Realistic Pair Distributions in Blazar/EBL Cascades

    Science.gov (United States)

    Vafin, S.; Rafighi, I.; Pohl, M.; Niemiec, J.

    2018-04-01

    This work revisits the electrostatic instability for blazar-induced pair beams propagating through the intergalactic medium (IGM) using linear analysis and PIC simulations. We study the impact of the realistic distribution function of pairs resulting from the interaction of high-energy gamma-rays with the extragalactic background light. We present analytical and numerical calculations of the linear growth rate of the instability for the arbitrary orientation of wave vectors. Our results explicitly demonstrate that the finite angular spread of the beam dramatically affects the growth rate of the waves, leading to the fastest growth for wave vectors quasi-parallel to the beam direction and a growth rate at oblique directions that is only a factor of 2–4 smaller compared to the maximum. To study the nonlinear beam relaxation, we performed PIC simulations that take into account a realistic wide-energy distribution of beam particles. The parameters of the simulated beam-plasma system provide an adequate physical picture that can be extrapolated to realistic blazar-induced pairs. In our simulations, the beam looses only 1% of its energy, and we analytically estimate that the beam would lose its total energy over about 100 simulation times. An analytical scaling is then used to extrapolate the parameters of realistic blazar-induced pair beams. We find that they can dissipate their energy slightly faster by the electrostatic instability than through inverse-Compton scattering. The uncertainties arising from, e.g., details of the primary gamma-ray spectrum are too large to make firm statements for individual blazars, and an analysis based on their specific properties is required.

  19. UV and X-ray Variability of Blazars Alok C. Gupta

    Indian Academy of Sciences (India)

    Hewitt & Burbidge (1980). It is the brightest blazar in UV/X-ray energies in the southern hemisphere. It was discovered as a X-ray source by ..... Piner, B. G., Pant, N., Edwards, P. G. 2008, Astrophys. J., 678, 64. Rani, B., Wiita, P. J., Gupta, A. C. 2009, Astrophys. J., 696, 2170. Rani, B., Gupta, A. C., Joshi, U. C., Ganesh, S., ...

  20. Testing the blazar sequence and black hole mass scaling with BL Lac objects

    NARCIS (Netherlands)

    Plotkin, Richard M.; Markoff, Sera; Anderson, Scott F.; Kelly, Brandon C.; Körding, Elmar; Trager, Scott C.; Romero, Gustavo E.; Sunyaev, Rashid A.; Belloni, Tomaso

    Jets from accreting black holes appear remarkably similar over eight orders of magnitude in black hole mass, with more massive black holes generally launching more powerful jets. For example, there is an observed correlation, termed the fundamental plane of black hole accretion, between black hole

  1. Testing the blazar sequence and black hole mass scaling with BL Lac objects

    NARCIS (Netherlands)

    Plotkin, R.M.; Markoff, S.; Anderson, S.F.; Kelly, B.C.; Körding, E.; Trager, S.C.

    2010-01-01

    Jets from accreting black holes appear remarkably similar over eight orders of magnitude in black hole mass, with more massive black holes generally launching more powerful jets. For example, there is an observed correlation, termed the fundamental plane of black hole accretion, between black hole

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

    DEFF Research Database (Denmark)

    Sbarrato, T.; Ghisellini, G.; Tagliaferri, G.

    2016-01-01

    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/X-ray Telescope, showing different variability behaviours. We found that NuSTAR is instrumental to explore the variability of powerful high-redshift blazars, even when...... no γ -ray emission is detected. The two sources have proven to have respectively the most luminous accretion disc and the most powerful jet among known blazars. Thanks to these properties, they are located at the extreme end of the jet-accretion disc relation previously found for γ -ray detected...

  3. Revisiting the incidence of Mg II absorbers along the blazar sightlines

    Science.gov (United States)

    Mishra, Sapna; Chand, Hum; Gopal-Krishna; Joshi, Ravi

    2018-04-01

    It is believed that the cool gas clouds traced by Mg II absorption, within a velocity offset of 5000 km/s from the background quasar, are associated with the quasar itself, whereas the absorbers seen at larger velocity offsets towards us are intervening systems and hence their existence is completely independent of the background quasar. Recent evidence by Bergeron et al. 2011 (hereafter BBM), however, seriously questions this canonical view, by showing that the number density of intervening Mg II absorbers along the sightlines towards 45 blazars is, on average, 2 times the expectation based on the Mg II absorption systems seen on the sightlines to normal QSOs. Given the serious implications of this finding, it becomes important to revisit this issue by enlarging the source sample and subjecting it to an independent analysis. Here, we first report our results based on a re-analysis of the spectroscopic data for the BBM sample; this has reproduced their factor 2 excess in dN/dz along blazar sightlines, vis-a-vis the normal QSOs. Next, we assemble a 6 times larger sample of blazar sightlines, albeit with lower SNR. Using this enlarged sample together with the BBM sample, our analysis shows that the dN/dz of Mg II absorbers statistically matches that known for normal QSO sightlines.

  4. Gamma-Ray Flaring Activity from the Gravitationally Lensed Blazar PKS 1830-211 Observed by Fermi LAT

    Energy Technology Data Exchange (ETDEWEB)

    Abdo, A. A.; et al.

    2015-01-23

    The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope routinely detects the MeV-peaked flat-spectrum radio quasar PKS 1830–211 (z = 2.507). Its apparent isotropic γ-ray luminosity (E > 100 MeV), averaged over ~3 years of observations and peaking on 2010 October 14/15 at 2.9 × 10(50) erg s(–)(1), makes it among the brightest high-redshift Fermi blazars. No published model with a single lens can account for all of the observed characteristics of this complex system. Based on radio observations, one expects time-delayed variability to follow about 25 days after a primary flare, with flux about a factor of 1.5 less. Two large γ-ray flares of PKS 1830–211 have been detected by the LAT in the considered period, and no substantial evidence for such a delayed activity was found. This allows us to place a lower limit of about 6 on the γ-ray flux ratio between the two lensed images. Swift XRT observations from a dedicated Target of Opportunity program indicate a hard spectrum with no significant correlation of X-ray flux with the γ-ray variability. The spectral energy distribution can be modeled with inverse Compton scattering of thermal photons from the dusty torus. The implications of the LAT data in terms of variability, the lack of evident delayed flare events, and different radio and γ-ray flux ratios are discussed. Microlensing effects, absorption, size and location of the emitting regions, the complex mass distribution of the system, an energy-dependent inner structure of the source, and flux suppression by the lens galaxy for one image path may be considered as hypotheses for understanding our results.

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

    International Nuclear Information System (INIS)

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

    2015-01-01

    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

  6. Probing the Diffuse Optical-IR Background with TeV Blazars Detected with the MAGIC Telescopes

    Directory of Open Access Journals (Sweden)

    Elisa Prandini

    2017-11-01

    Full Text Available Blazars are radio loud quasars whose jet points toward the observer. The observed emission is mostly non-thermal, dominated by the jet emission, and in some cases extends up to the very high energy gamma rays (VHE; E > 100 GeV. To date, more than 60 blazars have been detected at VHE mainly with ground-based imaging atmospheric Cherenkov telescopes (IACTs such as MAGIC, H.E.S.S., and VERITAS. Energetic photons from a blazar may interact with the diffuse optical and IR background (the extragalactic background light, EBL leaving an imprint on the blazar energy spectrum. This effect can be used to constrain the EBL, with basic assumptions on the intrinsic energy spectrum. Current generation of IACTs is providing valuable measurements of the EBL density and energy spectrum from optical to infrared frequencies. In this contribution, we present the latest results obtained with the data taken with the MAGIC telescopes: using 32 spectra from 12 blazars, the scale factor of the optical density predicted by the EBL model from Domínguez et al. (2011 is constrained to be 0.95 (+0.11, −0.12stat (+0.16, −0.07sys, where a value of 1 means the perfect match with the model.

  7. Probing the Diffuse Optical-IR Background with TeV Blazars Detected with the MAGIC Telescopes

    Energy Technology Data Exchange (ETDEWEB)

    Prandini, Elisa [Dipartimento di Fisica e Astronomia “G. Galilei”, University of Padova, Padua (Italy); Domínguez, Alberto [Departamento de Física Atómica, Universidad Complutense, Madrid (Spain); Fallah Ramazani, Vandad [Tuorla observatory, University of Turku, Turku (Finland); Hassan, Tarek [IFAE, The Barcelona Institute of Science and Technology, Bellaterra (Spain); Mazin, Daniel [Max Planck Institute for Physics, Munich (Germany); Institute for Cosmic Ray Research, University of Tokyo, Tokyo (Japan); Moralejo, Abelardo [IFAE, The Barcelona Institute of Science and Technology, Bellaterra (Spain); Nievas Rosillo, Mireia [Departamento de Física Atómica, Universidad Complutense, Madrid (Spain); Vanzo, Gaia; Vazquez Acosta, Monica, E-mail: prandini@pd.infn.it [Instituto de Astrofísica de Canarias, Tenerife (Spain); Departamento de Astrofisica, Universidad de La Laguna, Tenerife (Spain)

    2017-11-22

    Blazars are radio loud quasars whose jet points toward the observer. The observed emission is mostly non-thermal, dominated by the jet emission, and in some cases extends up to the very high energy gamma rays (VHE; E > 100 GeV). To date, more than 60 blazars have been detected at VHE mainly with ground-based imaging atmospheric Cherenkov telescopes (IACTs) such as MAGIC, H.E.S.S., and VERITAS. Energetic photons from a blazar may interact with the diffuse optical and IR background (the extragalactic background light, EBL) leaving an imprint on the blazar energy spectrum. This effect can be used to constrain the EBL, with basic assumptions on the intrinsic energy spectrum. Current generation of IACTs is providing valuable measurements of the EBL density and energy spectrum from optical to infrared frequencies. In this contribution, we present the latest results obtained with the data taken with the MAGIC telescopes: using 32 spectra from 12 blazars, the scale factor of the optical density predicted by the EBL model from Domínguez et al. (2011) is constrained to be 0.95 (+0.11, −0.12){sub stat} (+0.16, −0.07){sub sys}, where a value of 1 means the perfect match with the model.

  8. The H-Index of `An Approach to Correlate Tandem Mass Spectral Data of Peptides with Amino Acid Sequences in a Protein Database'

    Science.gov (United States)

    Washburn, Michael P.

    2015-11-01

    Over 20 years ago a remarkable paper was published in the Journal of American Society for Mass Spectrometry. This paper from Jimmy Eng, Ashley McCormack, and John Yates described the use of protein databases to drive the interpretation of tandem mass spectra of peptides. This paper now has over 3660 citations and continues to average more than 260 per year over the last decade. This is an amazing scientific achievement. The reason for this is the paper was a cutting edge development at the moment in time when genomes of organisms were being sequenced, protein and peptide mass spectrometry was growing into the field of proteomics, and the power of computing was growing quickly in accordance with Moore's law. This work by the Yates lab grew in importance as genomics, proteomics, and computation all advanced and eventually resulted in the widely used SEQUEST algorithm and platform for the analysis of tandem mass spectrometry data. This commentary provides an analysis of the impact of this paper by analyzing the citations it has generated and the impact of these citing papers.

  9. 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.

  10. Research and characterisation of blazar candidates among the Fermi/LAT 3FGL catalogue using multivariate classifications

    Science.gov (United States)

    Lefaucheur, Julien; Pita, Santiago

    2017-06-01

    Context. In the recently published 3FGL catalogue, the Fermi/LAT collaboration reports the detection of γ-ray emission from 3034 sources obtained after four years of observations. The nature of 1010 of those sources is unknown, whereas 2023 have well-identified counterparts in other wavelengths. Most of the associated sources are labelled as blazars (1717/2023), but the BL Lac or FSRQ nature of 573 of these blazars is still undetermined. Aims: The aim of this study was two-fold. First, to significantly increase the number of blazar candidates from a search among the large number of Fermi/LAT 3FGL unassociated sources (case A). Second, to determine the BL Lac or FSRQ nature of the blazar candidates, including those determined as such in this work and the blazar candidates of uncertain type (BCU) that are already present in the 3FGL catalogue (case B). Methods: For this purpose, multivariate classifiers - boosted decision trees and multilayer perceptron neural networks - were trained using samples of labelled sources with no caution flag from the 3FGL catalogue and carefully chosen discriminant parameters. The decisions of the classifiers were combined in order to obtain a high level of source identification along with well controlled numbers of expected false associations. Specifically for case A, dedicated classifications were generated for high (| b | >10◦) and low (| b | ≤10◦) galactic latitude sources; in addition, the application of classifiers to samples of sources with caution flag was considered separately, and specific performance metrics were estimated. Results: We obtained a sample of 595 blazar candidates (high and low galactic latitude) among the unassociated sources of the 3FGL catalogue. We also obtained a sample of 509 BL Lacs and 295 FSRQs from the blazar candidates cited above and the BCUs of the 3FGL catalogue. The number of expected false associations is given for different samples of candidates. It is, in particular, notably low ( 9

  11. Spectral Pollution

    OpenAIRE

    Davies, E B; Plum, M

    2003-01-01

    We discuss the problems arising when computing eigenvalues of self-adjoint operators which lie in a gap between two parts of the essential spectrum. Spectral pollution, i.e. the apparent existence of eigenvalues in numerical computations, when no such eigenvalues actually exist, is commonplace in problems arising in applied mathematics. We describe a geometrically inspired method which avoids this difficulty, and show that it yields the same results as an algorithm of Zimmermann and Mertins.

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

    International Nuclear Information System (INIS)

    Le Gallou, R.

    2001-11-01

    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

  13. The VHE anomaly in blazar spectra and related phenomena

    Directory of Open Access Journals (Sweden)

    Dzhatdoev Timur

    2017-01-01

    Full Text Available Most of the recent research on extragalactic γ-ray propagation focused on the study of the γγ * e+e− absorption process (“absorption-only model”. Starting from a possible anomaly at very high energies (VHE, E > 100 GeV, we briefly review several existing deviations from this model. The exotic interpretation of the VHE anomaly is not supported by the recent works. On the other hand, the process of intergalactic electromagnetic cascade development naturally explains these effects. We discuss phenomenology of intergalactic cascades and the main spectral signatures of the electromagnetic cascade model. We also briefly consider the hadronic cascade model; it also may explain the data, but requires low strength of magnetic field around the source of primary protons or nuclei.

  14. Secondary photons and neutrinos from cosmic rays produced by distant blazars.

    Science.gov (United States)

    Essey, Warren; Kalashev, Oleg E; Kusenko, Alexander; Beacom, John F

    2010-04-09

    Secondary photons and neutrinos produced in the interactions of cosmic ray protons emitted by distant active galactic nuclei (AGN) with the photon background along the line of sight can reveal a wealth of new information about the intergalactic magnetic fields, extragalactic background light, and the acceleration mechanisms of cosmic rays. The secondary photons may have already been observed by gamma-ray telescopes. We show that the secondary neutrinos improve the prospects of discovering distant blazars by IceCube, and we discuss the ramifications for the cosmic backgrounds, magnetic fields, and AGN models.

  15. 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.

  16. SALT-HRS observation of the blazar TXS 0506+056 associated with IceCube-170922A

    Science.gov (United States)

    van Soelen, B.; Buckley, David A. H.; Boettcher, Markus

    2017-10-01

    The blazar TXS 0506+056, which has been proposed as the counterpart to the neutrino event IceCube-170922A, has recently been reported to show increased optical and gamma-ray emission (ATel #10817, #10801, #10799, #10794, #10792, #10791, #10787, #10773).

  17. Intra-night Optical Variability Monitoring of Fermi Blazars: First Results from 1.3 m J. C. Bhattacharya Telescope

    International Nuclear Information System (INIS)

    Paliya, Vaidehi S.; Ajello, M.; Kaur, A.; Stalin, C. S.

    2017-01-01

    We report the first results obtained from our campaign to characterize the intra-night-optical variability (INOV) properties of Fermi detected blazars, using the observations from the recently commissioned 1.3 m J. C. Bhattacharya telescope (JCBT). During the first run, we were able to observe 17 blazars in the Bessel R filter for ∼137 hr. Using C- and scaled F -statistics, we quantify the extent of INOV and derive the duty cycle (DC), which is the fraction of time during which a source exhibits a substantial flux variability. We find a high DC of 40% for BL Lac objects and the flat spectrum radio quasars are relatively less variable (DC ∼ 15%). However, when estimated for blazars sub-classes, a high DC of ∼59% is found in low synchrotron peaked (LSP) blazars, whereas, intermediate and high synchrotron peaked objects have a low DC of ∼11% and 13%, respectively. We find evidence of the association of the high amplitude INOV with the γ -ray flaring state. We also notice a high polarization during the elevated INOV states (for the sources that have polarimetric data available), thus supporting the jet based origin of the observed variability. We plan to enlarge the sample and utilize the time availability from the small telescopes, such as 1.3 m JCBT, to strengthen/verify the results obtained in this work and those existing in the literature.

  18. Results of the first simultaneous X-ray, optical, and radio campaign on the blazar PKS 1622-297

    NARCIS (Netherlands)

    Meyer, Angela Osterman; Miller, H. Richard; Marshall, Kevin; Ryle, Wesley T.; Aller, Hugh; Aller, Margo; McFarland, John P.; Pollock, Joseph T.; Reichart, Daniel E.; Crain, J. Adam; Ivarsen, Kevin M.; LaCluyze, Aaron P.; Nysewander, Melissa C.

    Coordinated X-ray, optical, and radio observations of the blazar PKS 1622-297 were obtained during a three-week campaign in 2006 using the Rossi X-Ray Timing Explorer (RXTE), the University of Michigan Radio Astronomy Observatory, and optical telescopes at Cerro Tololo Inter-American Observatory.

  19. Intra-night Optical Variability Monitoring of Fermi Blazars: First Results from 1.3 m J. C. Bhattacharya Telescope

    Energy Technology Data Exchange (ETDEWEB)

    Paliya, Vaidehi S.; Ajello, M.; Kaur, A. [Department of Physics and Astronomy, Clemson University, Kinard Lab of Physics, Clemson, SC 29634-0978 (United States); Stalin, C. S., E-mail: vpaliya@g.clemson.edu [Indian Institute of Astrophysics, Block II, Koramangala, Bangalore-560034 (India)

    2017-07-20

    We report the first results obtained from our campaign to characterize the intra-night-optical variability (INOV) properties of Fermi detected blazars, using the observations from the recently commissioned 1.3 m J. C. Bhattacharya telescope (JCBT). During the first run, we were able to observe 17 blazars in the Bessel R filter for ∼137 hr. Using C- and scaled F -statistics, we quantify the extent of INOV and derive the duty cycle (DC), which is the fraction of time during which a source exhibits a substantial flux variability. We find a high DC of 40% for BL Lac objects and the flat spectrum radio quasars are relatively less variable (DC ∼ 15%). However, when estimated for blazars sub-classes, a high DC of ∼59% is found in low synchrotron peaked (LSP) blazars, whereas, intermediate and high synchrotron peaked objects have a low DC of ∼11% and 13%, respectively. We find evidence of the association of the high amplitude INOV with the γ -ray flaring state. We also notice a high polarization during the elevated INOV states (for the sources that have polarimetric data available), thus supporting the jet based origin of the observed variability. We plan to enlarge the sample and utilize the time availability from the small telescopes, such as 1.3 m JCBT, to strengthen/verify the results obtained in this work and those existing in the literature.

  20. Earthquake sequence simulations of a fault in a viscoelastic material with a spectral boundary integral equation method: The effect of interseismic stress relaxation on a behavior of a rate-weakening patch

    Science.gov (United States)

    Miyake, Y.; Noda, H.

    2017-12-01

    Earthquake sequences involve many processes in a wide range of time scales, from quasistatic loading to dynamic rupture. At a depth of brittle-plastic transitional and deeper, rock behaves as a viscous fluid in a long timescale, but as an elastic material in a short timescale. Viscoelastic stress relaxation may be important in the interseismic periods at the depth, near the deeper limit of the seismogenic layer or the region of slow slip events (SSEs) [Namiki et al., 2014 and references therein]. In the present study, we implemented the viscoelastic effect (Maxwell material) in fully-dynamic earthquake sequence simulations using a spectral boundary integral equation method (SBIEM) [e.g., Lapusta et al., 2000]. SBIEM is efficient in calculation of convolutional terms for dynamic stress transfer, and the problem size is limited by the amount of memory available. Linear viscoelasticity could be implemented by convolution of slip rate history and Green's function, but this method requires additional memory and thus not suitable for the implementation to the present code. Instead, we integrated the evolution of "effective slip" distribution, which gives static stress distribution when convolved with static elastic Green's function. This method works only for simple viscoelastic property distributions, but such models are suitable for numerical experiments aiming basic understanding of the system behavior because of the virtue of SBIEM, the ability of fine on-fault spatial resolution and efficient computation utilizing the fast Fourier transformation. In the present study, we examined the effect of viscoelasticity on earthquake sequences of a fault with a rate-weakening patch. A series of simulations with various relaxation time tc revealed that as decreasing tc, recurrence intervals of earthquakes increases and seismicity ultimately disappears. As long as studied, this transition to aseismic behavior is NOT associated with SSEs. In a case where the rate-weakening patch

  1. The role of plasma instabilities in the propagation of gamma-rays from distant Blazars

    Energy Technology Data Exchange (ETDEWEB)

    Saveliev, A.; Evoli, C.; Sigl, G. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik

    2013-11-15

    The observation in the GeV band of distant blazars has been recently used to put constraints on the Extragalactic Background Light (EBL) and Extragalactic Magnetic Fields (EGMF). To support such claims one has to assume that the leptonic component of the electromagnetic cascade initiated by blazar gamma-rays is deflected away by strong enough EGMF, suppressing the signal in the Fermi window. Apart from magnetic fields, the development of such a cascade might be affected by plasma instabilities due to interactions with the ionized component of the Intergalactic Medium (IGM). In this paper we model the electromagnetic cascade through a Monte Carlo simulation in which both effects are taken into account separately, and we derive constraints on these scenarios from the combined Fermi-HESS data set. In the specific case of 1ES 0229+200 observations, we show that both explanations of the GeV flux suppression are compatible with the available data, specifically by assuming a magnetic field of B >or similar 10{sup -16} G or an IGM temperature of T

  2. Search for neutrino emission from gamma-ray flaring blazars with the ANTARES telescope

    Science.gov (United States)

    Adrián-Martínez, S.; Al Samarai, I.; 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.; Lo Presti, D.; 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. 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.

    2012-08-01

    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 factor of two with respect to a standard time-integrated point source search. First results on the search for neutrinos associated with ten bright and variable Fermi sources are presented.

  3. 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.

  4. RAPID OPTICAL VARIABILITY IN BLAZAR S5 0716+71 DURING 2010 MARCH

    International Nuclear Information System (INIS)

    Chandra, S.; Baliyan, K. S.; Ganesh, S.; Joshi, U. C.

    2011-01-01

    We report rapid optical variability for the blazar S5 0716+71 during 2010 March 8-10 and 19-20 in the CCD observations made from Mt. Abu Infrared Observatory. The light curves are constructed for a duration longer than 3 hr each night, with very high temporal resolution (∼45 s in the R band). During 2010 March 8, the source smoothly decayed by about 0.15 mag in 2.88 hr, apart from a fast flicker lasting about 30 minutes. S5 0716+71 brightened during March 9 and 10, showing high activity, while it was relatively faint (>14 mag in the R band) albeit variable during March 19-20. During March 9 and 10, rapid flickers in the intensity modulated the long-term intra-night (∼3 hr) variations. The present observations suggest that the blazar S5 0716+71 showed night-to-night and intra-night variability at various timescales with a 100% duty cycle for variation along with microvariability at significant levels. On a night-to-night basis, the source exhibits mild bluer-when-brighter nature. The interaction of shocks with local inhomogeneities in the jet appears to cause intra-night variations, while microvariations could be due to small-scale perturbations intrinsic to the jet.

  5. Blazar Variability from Turbulence in Jets Launched by Magnetically Arrested Accretion Flows

    Energy Technology Data Exchange (ETDEWEB)

    Riordan, Michael O’; Pe’er, Asaf [Physics Department, University College Cork, Cork (Ireland); McKinney, Jonathan C., E-mail: michael_oriordan@umail.ucc.ie [Department of Physics and Joint Space-Science Institute, University of Maryland, College Park, MD 20742 (United States)

    2017-07-10

    Blazars show variability on timescales ranging from minutes to years, the former being comparable to and in some cases even shorter than the light-crossing time of the central black hole. The observed γ -ray light curves can be described by a power-law power density spectrum (PDS), with a similar index for both BL Lacs and flat-spectrum radio quasars. We show that this variability can be produced by turbulence in relativistic jets launched by magnetically arrested accretion flows (MADs). We perform radiative transport calculations on the turbulent, highly magnetized jet launching region of a MAD with a rapidly rotating supermassive black hole. The resulting synchrotron and synchrotron self-Compton emission, originating from close to the black hole horizon, is highly variable. This variability is characterized by PDS, which is remarkably similar to the observed power-law spectrum at frequencies less than a few per day. Furthermore, turbulence in the jet launching region naturally produces fluctuations in the plasma on scales much smaller than the horizon radius. We speculate that similar turbulent processes, operating in the jet at large radii (and therefore a high bulk Lorentz factor), are responsible for blazar variability over many decades in frequency, including on minute timescales.

  6. 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.

  7. A SEARCH FOR SPECTRAL HYSTERESIS AND ENERGY-DEPENDENT TIME LAGS FROM X-RAY AND TeV GAMMA-RAY OBSERVATIONS OF Mrk 421

    Energy Technology Data Exchange (ETDEWEB)

    Abeysekara, A. U.; Flinders, A. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Archambault, S.; Feng, Q. [Physics Department, McGill University, Montreal, QC H3A 2T8 (Canada); Archer, A.; 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); Bird, R.; Buchovecky, M. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States); Cardenzana, J. V; Eisch, J. D. [Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (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.; Finley, J. P. [Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907 (United States); Falcone, A. [Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802 (United States); Fleischhack, H. [DESY, Platanenallee 6, D-15738 Zeuthen (Germany); Collaboration: VERITAS Collaboration; MAGIC Collaboration; and others

    2017-01-01

    Blazars are variable emitters across all wavelengths over a wide range of timescales, from months down to minutes. It is therefore essential to observe blazars simultaneously at different wavelengths, especially in the X-ray and gamma-ray bands, where the broadband spectral energy distributions usually peak. In this work, we report on three “target-of-opportunity” observations of Mrk 421, one of the brightest TeV blazars, triggered by a strong flaring event at TeV energies in 2014. These observations feature long, continuous, and simultaneous exposures with XMM-Newton (covering the X-ray and optical/ultraviolet bands) and VERITAS (covering the TeV gamma-ray band), along with contemporaneous observations from other gamma-ray facilities (MAGIC and Fermi -Large Area Telescope) and a number of radio and optical facilities. Although neither rapid flares nor significant X-ray/TeV correlation are detected, these observations reveal subtle changes in the X-ray spectrum of the source over the course of a few days. We search the simultaneous X-ray and TeV data for spectral hysteresis patterns and time delays, which could provide insight into the emission mechanisms and the source properties (e.g., the radius of the emitting region, the strength of the magnetic field, and related timescales). The observed broadband spectra are consistent with a one-zone synchrotron self-Compton model. We find that the power spectral density distribution at ≳4 × 10{sup −4} Hz from the X-ray data can be described by a power-law model with an index value between 1.2 and 1.8, and do not find evidence for a steepening of the power spectral index (often associated with a characteristic length scale) compared to the previously reported values at lower frequencies.

  8. The Imprint of the Extragalactic Background Light in the Gamma-Ray Spectra of Blazars

    Science.gov (United States)

    Ackermann, M.; Ajello, M.; Allafort, A.; Schady, P.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bellazzini, R; Blandford, R. D.; hide

    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 isimportant to understand the nature of star formation and galaxy evolution, but direct measurements of the EBL are limited 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 approx. 1.6. This feature is caused by attenuation of gamma rays by the EBL at optical to ultraviolet frequencies and allowed us to measure the EBL flux density in this frequency band.

  9. 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.

  10. The extreme blazar AO 0235+164 as seen by extensive ground and space radio observations

    Science.gov (United States)

    Kutkin, A. M.; Pashchenko, I. N.; Lisakov, M. M.; Voytsik, P. A.; Sokolovsky, K. V.; Kovalev, Y. Y.; Lobanov, A. P.; Ipatov, A. V.; Aller, M. F.; Aller, H. D.; Lahteenmaki, A.; Tornikoski, M.; Gurvits, L. I.

    2018-04-01

    Clues to the physical conditions in radio cores of blazars come from measurements of brightness temperatures as well as effects produced by intrinsic opacity. We study the properties of the ultra-compact blazar AO 0235+164 with RadioAstron ground-space radio interferometer, multifrequency VLBA, EVN, and single-dish radio observations. We employ visibility modelling and image stacking for deriving structure and kinematics of the source, and use Gaussian process regression to find the relative multiband time delays of the flares. The multifrequency core size and time lags support prevailing synchrotron self-absorption. The intrinsic brightness temperature of the core derived from ground-based very long baseline interferometry (VLBI) is close to the equipartition regime value. In the same time, there is evidence for ultra-compact features of the size of less than 10 μas in the source, which might be responsible for the extreme apparent brightness temperatures of up to 1014 K as measured by RadioAstron. In 2007-2016 the VLBI components in the source at 43 GHz are found predominantly in two directions, suggesting a bend of the outflow from southern to northern direction. The apparent opening angle of the jet seen in the stacked image at 43 GHz is two times wider than that at 15 GHz, indicating a collimation of the flow within the central 1.5 mas. We estimate the Lorentz factor Γ = 14, the Doppler factor δ = 21, and the viewing angle θ = 1.7° of the apparent jet base, derive the gradients of magnetic field strength and electron density in the outflow, and the distance between jet apex and the core at each frequency.

  11. Extremely Rapid X-Ray Flares of TeV Blazars in the RXTE Era

    Science.gov (United States)

    Zhu, S. F.; Xue, Y. Q.; Brandt, W. N.; Cui, W.; Wang, Y. J.

    2018-01-01

    Rapid flares from blazars in very high-energy (VHE) γ-rays challenge the common understanding of jets of active galactic nuclei (AGNs). The same population of ultra-relativistic electrons is often thought to be responsible for both X-ray and VHE emission. We thus systematically searched for X-ray flares at sub-hour timescales of TeV blazars in the entire Rossi X-ray Timing Explorer archival database. We found rapid flares from PKS 2005‑489 and S5 0716+714, and a candidate rapid flare from 1ES 1101‑232. In particular, the characteristic rise timescale of PKS 2005‑489 is less than half a minute, which, to our knowledge, is the shortest among known AGN flares at any wavelengths. The timescales of these rapid flares indicate that the size of the central supermassive black hole is not a hard lower limit on the physical size of the emission region of the flare. PKS 2005‑489 shows possible hard lags in its flare, which could be attributed to particle acceleration (injection); its flaring component has the hardest spectrum when it first appears. For all flares, the flaring components show similar hard spectra with {{Γ }}=1.7{--}1.9, and we estimate the magnetic field strength B ∼ 0.1–1.0 G by assuming synchrotron cooling. These flares could be caused by inhomogeneity of the jets. Models that can only produce rapid γ-ray flares but little synchrotron activity are less favorable.

  12. A window on stochastic processes and gamma-ray cosmology through spectral and temporal studies of AGN observed with H.E.S.S

    International Nuclear Information System (INIS)

    Biteau, J.

    2013-01-01

    Fifty years after the discovery that quasars are extragalactic sources, their bright cores (AGN) and the jets that some of them exhibit still have plenty of secrets to share, particularly through observations in the gamma-ray band. Above 100 GeV, Cherenkov telescopes such as H.E.S.S. have detected 50 AGN, mostly blazars, objects whose jets are pointed toward the observer. The detection of two faint ones, 1ES 1312-423 and SHBL J001355.9-185406, is described in this thesis. Their multiwavelength spectra are reproduced with a synchrotron self-Compton model. The γ rays emitted by blazars are partly absorbed by the extragalactic background light (EBL), the second most intense cosmological background, which carries the integrated history of star formation. The first detection of this absorption above 100 GeV is performed, enabling the measurement of the EBL peak-amplitude in the optical band at the 20% level. In addition to these spectral studies, the fast flux-variations of blazars are investigated using the outbursts of PKS 2155-304 seen by H.E.S.S.. The observation of a skewed flux distribution and of an R.M.S.-flux correlation are interpreted within a kinematic model, where the emission is a realization of a stochastic process. (author)

  13. Spectral Decomposition Algorithm (SDA)

    Data.gov (United States)

    National Aeronautics and Space Administration — Spectral Decomposition Algorithm (SDA) is an unsupervised feature extraction technique similar to PCA that was developed to better distinguish spectral features in...

  14. Search for High-Confidence Blazar Candidates and Their MWL Counterparts in the Fermi-LAT Catalog Using Machine Learning

    Directory of Open Access Journals (Sweden)

    Sabrina Einecke

    2016-08-01

    Full Text Available A large fraction of the gamma-ray sources presented in the Third Fermi-LAT source catalog (3FGL is affiliated with counterparts and source types, but 1010 sources remain unassociated and 573 sources are associated with active galaxies of uncertain type. The purpose of this study is to assign blazar classes to these unassociated and uncertain sources, and to link counterparts to the unassociated. A machine learning algorithm is used for the classification, based on properties extracted from the 3FGL, an infrared and an X-ray catalog. To estimate the reliability of the classification, performance measures are considered through validation techniques. The classification yielded purity values around 90% with efficiency values of roughly 50%. The prediction of high-confidence blazar candidates has been conducted successfully, and the possibility to link counterparts in the same procedure has been proven. These findings confirm the relevance of this novel multiwavelength approach.

  15. Metallicity and the spectral energy distribution and spectral types of dwarf O-stars

    NARCIS (Netherlands)

    Mokiem, M.R.; Martín-Hernández, N.L.; Lenorzer, A.; de Koter, A.; Tielens, A.G.G.M.

    2004-01-01

    We present a systematic study of the effect of metallicity on the stellar spectral energy distribution (SED) of O main sequence (dwarf) stars, focussing on the hydrogen and helium ionizing continua, and on the optical and near-IR lines used for spectral classification. The spectra are based on

  16. Long-Term Monitoring of Bright Blazars in the Multi-GeV to TeV Range with FACT

    Directory of Open Access Journals (Sweden)

    Fabian Temme

    2017-02-01

    Full Text Available Blazars like Markarian 421 or Markarian 501 are active galactic nuclei (AGN, with their jets orientated towards the observer. They are among the brightest objects in the very high energy (VHE gamma ray regime (>100 GeV. Their emitted gamma-ray fluxes are extremely variable, with changing activity levels on timescales between minutes, months, and even years. Several questions are part of the current research, such as the question of the emission regions or the engine of the AGN and the particle acceleration. A dedicated longterm monitoring program is necessary to investigate the properties of blazars in detail. A densely sampled and unbiased light curve allows for observation of both high and low states of the sources, and the combination with multi-wavelength observation could contribute to the answer of several questions mentioned above. FACT (First G-APD Cherenkov Telescope is the first operational telescope using silicon photomultiplier (SiPM, also known as Geigermode—Avalanche Photo Diode, G-APD as photon detectors. SiPM have a very homogenous and stable longterm performance, and allow operation even during full moon without any filter, leading to a maximal duty cycle for an Imaging Air Cherenkov Telescope (IACT. Hence, FACT is an ideal device for such a longterm monitoring of bright blazars. A small set of sources (e.g., Markarian 421, Markarian 501, 1ES 1959+650, and 1ES 2344+51.4 is currently being monitored. In this contribution, the FACT telescope and the concept of longterm monitoring of bright blazars will be introduced. The results of the monitoring program will be shown, and the advantages of densely sampled and unbiased light curves will be discussed.

  17. Spectral Imaging by Upconversion

    DEFF Research Database (Denmark)

    Dam, Jeppe Seidelin; Pedersen, Christian; Tidemand-Lichtenberg, Peter

    2011-01-01

    We present a method to obtain spectrally resolved images using upconversion. By this method an image is spectrally shifted from one spectral region to another wavelength. Since the process is spectrally sensitive it allows for a tailored spectral response. We believe this will allow standard sili...... silicon based cameras designed for visible/near infrared radiation to be used for spectral images in the mid infrared. This can lead to much lower costs for such imaging devices, and a better performance.......We present a method to obtain spectrally resolved images using upconversion. By this method an image is spectrally shifted from one spectral region to another wavelength. Since the process is spectrally sensitive it allows for a tailored spectral response. We believe this will allow standard...

  18. Implications of variability Patterns Observed in TeV Blazars on the Structure of the Inner Jet

    Energy Technology Data Exchange (ETDEWEB)

    Madejski, Grzegorz

    2003-03-18

    The recent long look X-ray observations of TeV blazars have revealed many important new features concerning their time variability. In this paper, we suggest a physical interpretation for those features based on the framework of the internal and external shock scenarios. We present a simplified model applicable to TeV blazars, and investigate through simulations how each of the model parameters would affect to the observed light curve or spectrum. In particular, we show that the internal shock scenario naturally leads to all the observed variability properties including the structure function, but for it to be applicable, the fractional fluctuation of the initial bulk Lorentz factors must be small, {sigma}{prime}{sub {Lambda}} {triple_bond} {sigma}{sub {Lambda}}/{Lambda}{sub avrg} << 0.01. This implies very low dynamical efficiency of the internal shock scenario. We also suggest that several observational quantities--such as the characteristic time scale, the relative amplitude of flares as compared to the steady (''offset'') component, and the slope of the structure function--can be used to probe the inner jet. The results are applied to the TeV blazar Mrk 421, and this, within the context of the model, leads to the determination of several physical parameters: the ejection of a shell with average thickness of {approx} 10{sup 13} cm occurs on average every 10 minutes, and the shells collide {approx} 10{sup 17} cm away from the central source.

  19. Constraining the location of gamma-ray flares in luminous blazars

    Energy Technology Data Exchange (ETDEWEB)

    Nalewajko, Krzysztof; Begelman, Mitchell C. [JILA, University of Colorado and National Institute of Standards and Technology, 440 UCB, Boulder, CO 80309 (United States); Sikora, Marek, E-mail: knalew@jila.colorado.edu [Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw (Poland)

    2014-07-10

    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 ≲ 1, from an upper limit on the synchrotron self-Compton (SSC) luminosity L{sub SSC} ≲ L{sub X}, and from an upper limit on the efficient cooling photon energy E{sub cool,obs} ≲ 100 MeV. These three constraints are particularly strong for sources with low accretion disk luminosity L{sub d}. The commonly used intrinsic pair-production opacity constraint on Γ is usually much weaker than the SSC constraint. The SSC and cooling constraints provide a robust lower 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{sub var,obs}. Alternative scenarios motivated by the observed gamma-ray/millimeter connection, in which gamma-ray flares of t{sub 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

  20. Fine Structure of the Core of the Blazar OJ 287-I

    Science.gov (United States)

    Matveyenko, L. I.; Sivakon', S. S.

    2017-12-01

    The fine structure of the active region, the bulge, of the blazar OJ 287 has been investigated with a resolution of 20 μas (0.1 pc) at a wavelength of 7 mm, the epochs of 2007-2017. The structure and kinematics correspond to a vortex nature. The surrounding matter, the plasma, is transferred to the center along two arms from opposite directions. The emerging excess angular momentum is carried away along the rotation axis by bipolar outflows, rotating coaxial tubes, in a direction X ≈ -120° in the plane of the sky as it is accumulated. The central high-velocity bipolar outflow has a helical shape. The diameters of the low-velocity flows are ø1 ≈ 0.3 and ø2 ≈ 0.65 mas, or 1.4 and 3 pc, respectively. Ring currents whose tangential directions are observed as parallel chains of components are excited in the flow walls. The peak brightness temperature of the nozzle reaches Tb ≈ 1012-1013 K. A "disk" with a diameter ø ≈ 0.5 mas (≈2.2 pc) is observed by the absorption of synchrotron radiation. The disk is inclined to the plane of the sky at an angle of 60° in the jet direction. The fragments are seen from a distance of ˜0.2 mas outside the absorption zone. The jet sizes exceed considerably the counterjet ones. An enhanced supply of plasma from the northern arm gives rise to an independent vortex 0.2 mas away from the central one in the NW direction. As in the first case, the helical central bipolar outflow is surrounded by a low-velocity component ø ≈ 0.28 mas in diameter with built-in ring currents. The jet is ejected in the direction X = -50° in the plane of the sky. The jet orientation changes, X = -130° at a distance of 1 mas. A high activity of the central and two side nozzles spaced 0.22 mas apart in the direction X = -40° is occasionally observed simultaneously. The active region of the blazar is observed through an ionized medium, a screen, whose influence is significant even at a wavelength of 7 mm. The absorption and refraction of the

  1. VizieR Online Data Catalog: Five years of blazar observations with VERITAS (Archambault+, 2016)

    Science.gov (United States)

    Archambault, S.; Archer, A.; 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.; Hutten, 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.; O'Faolain de Bhroithe, A.; 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.

    2018-04-01

    In this paper, we present the results of the analysis of most of the non-detected blazars observed by VERITAS from 2007 (the beginning of full-scale scientific operations) to 2012 August (before the upgrade of the VERITAS array, see Kieda 2013arXiv1308.4849D). The VERITAS (Very Energetic Radiation Imaging Telescope Array System) telescope array is composed of four IACTs of 12 m diameter each, located at the Fred Lawrence Whipple Observatory, on the slopes of Mount Hopkins, in southern Arizona (31°40'N, 110°57'W). Each telescope has a segmented mirror that focuses light onto a camera composed of 499 photomultipliers located at the focal plane. The instrument FOV is 3.5°. For further details on the VERITAS instrument, see Holder et al. (2006APh....25..391H) and Holder (2011ICRC...12..137H). The VERITAS observations here have an average length of 20 minutes (referred to as a run), before switching targets or wobble directions. (7 data files).

  2. The TeV blazar measurement of the extragalactic background light

    Energy Technology Data Exchange (ETDEWEB)

    Reesman, Rebecca; Walker, T.P., E-mail: rreesman@physics.osu.edu, E-mail: twalker@mps.ohio-state.edu [Department of Physics, The Ohio State University, Columbus, OH, 43210 (United States)

    2013-12-01

    Gamma-rays propagating through space are likely to be extinguished via electron-positron pair production off of the ambient extragalactic background light (EBL). The spectrum of the EBL is produced by starlight (and starlight reprocessed by dust) from all galaxies throughout the history of the Universe. The attenuation of 40–400 GeV gamma-rays has been observed by Fermi and used to measure the EBL spectrum over energies 1 eV–10 eV out to redshift z ∼ 1. Measurements of several TeV blazers are consistent with attenuation, attributed to the EBL at redshift z ∼ 0.1. Here we simultaneously analyze a set of TeV blazers at z ∼ 0.1 to measure the optical depth for 100 GeV–10 TeV gamma-rays, which interact with EBL of energies 0.05 eV–5 eV. Using a suite of models for the EBL, we show that the optical depth indicated by TeV blazar attenuation is in good agreement with the optical depths measured by Fermi at lower gamma-ray energies and higher redshifts.

  3. Characteristics of Gamma-Ray Loud Blazars in the VLBA Imaging and Polarimetry Survey

    Science.gov (United States)

    Linford, J. D.; Taylor, G. B.; Romani, R. W.; Healey, S. E.; Helmboldt, J. F.; Readhead, A. C.; Reeves, R.; Richards, J. L.; Cotter, G.

    2010-01-01

    The radio properties of blazars detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope have been observed as part of the VLBA Imaging and Polarimetry Survey. This large, flux-limited sample of active galactic nuclei (AGNs) provides insights into the mechanism that produces strong gamma-ray emission. At lower flux levels, radio flux density does not directly correlate with gamma-ray flux. We find that the LAT-detected BL Lac objects tend to be similar to the non-LAT BL Lac objects, but that the LAT-detected FSRQs are often significantly different from the non-LAT FSRQs. The differences between the gamma-ray loud and quiet FSRQS can be explained by Doppler boosting; these objects appear to require larger Doppler factors than those of the BL Lac objects. It is possible that the gamma-ray loud FSRQs are fundamentally different from the gamma-ray quiet FSRQs. Strong polarization at the base of the jet appears to be a signature for gamma-ray loud AGNs.

  4. Psychoacoustic Properties of Fibonacci Sequences

    Directory of Open Access Journals (Sweden)

    J. Sokoll

    2008-01-01

    Full Text Available 1202, Fibonacci set up one of the most interesting sequences in number theory. This sequence can be represented by so-called Fibonacci Numbers, and by a binary sequence of zeros and ones. If such a binary Fibonacci Sequence is played back as an audio file, a very dissonant sound results. This is caused by the “almost-periodic”, “self-similar” property of the binary sequence. The ratio of zeros and ones converges to the golden ratio, as do the primary and secondary spectral components intheir frequencies and amplitudes. These Fibonacci Sequences will be characterized using listening tests and psychoacoustic analyses. 

  5. Discovery of a Highly Polarized Optical Microflare in Blazar S5 0716+714 during the 2014 WEBT Campaign

    Science.gov (United States)

    Bhatta, G.; Goyal, A.; Ostrowski, M.; Stawarz, Ł.; Akitaya, H.; Arkharov, A. A.; Bachev, R.; Benítez, E.; Borman, G. A.; Carosati, D.; Cason, A. D.; Damljanovic, G.; Dhalla, S.; Frasca, A.; Hu, S.-M.; Itoh, R.; Jorstad, S.; Jableka, D.; Kawabata, K. S.; Klimanov, S. A.; Kurtanidze, O.; Larionov, V. M.; Laurence, D.; Leto, G.; Markowitz, A.; Marscher, A. P.; Moody, J. W.; Moritani, Y.; Ohlert, J. M.; Di Paola, A.; Raiteri, C. M.; Rizzi, N.; Sadun, A. C.; Sasada, M.; Sergeev, S.; Strigachev, A.; Takaki, K.; Troitsky, I. S.; Ui, T.; Villata, M.; Vince, O.; Webb, J. R.; Yoshida, M.; Zola, S.; Hiriart, D.

    2015-08-01

    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 the recent WEBT campaign on 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 ˜(40-60)% ± (2-10)% and the electric vector position angle ˜(10-20)° ± (1-8)° 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 behavior with a counterclockwise rotation, meaning the polarization degree decreases with the flux (but is higher in the flux decaying phase), and an approximately stable polarization angle. The overall very high polarization degree of the flare, its symmetric flux rise and decay profiles, and also its structured evolution in the Q-U plane all imply that the observed flux variation corresponds to a single emission region characterized by a highly ordered magnetic field. As discussed in the paper, a small-scale but strong shock propagating within the outflow, and compressing a disordered magnetic field component, provides a natural, though not unique, interpretation of our findings. The data collected by the WEBT Collaboration are stored in the WEBT archive; for questions regarding their availability, please contact the WEBT President Massimo Villata ().

  6. 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).

  7. Search for neutrino emission in gamma-ray flaring blazars with the ANTARES telescope

    Energy Technology Data Exchange (ETDEWEB)

    Sánchez Losa, Agustín, E-mail: agustin.sanchez@ific.uv.es [IFIC, Apartado de Correos 22085, E-46071 Valencia (Spain)

    2013-10-11

    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 toward 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 analyzed looking for neutrinos detected in the high state period of 10 bright and variable Fermi sources assuming that the neutrino emission follows the gamma-ray light curves. First results show a sensitivity improvement by a factor 2–3 with respect to a standard time-integrated point source search. The analysis has been done with an unbinned method based on the minimization of a likelihood ratio applied to data corresponding to a live time of 60 days. The width of the flaring periods ranges from 1 to 20 days. Despite the fact that the most significant studied source is compatible with background fluctuations, recently detected flares promise interesting future analyze.

  8. 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.

  9. Variability of Blazars JH Fan1,2,∗ , Y. Liu1,2, Y. Li3, QF Zhang3, J ...

    Indian Academy of Sciences (India)

    5Joint Institute for Galaxies and Cosmology, ShAO and USTC, CAS, Shanghai 200030, China. 6Abastumani Observatory .... We have monitored dozens of blazars on 1.56 m telescope at Sheshan station, Shang- hai Astronomical Observatory. .... Poon, H., Fan, J. H., Fu, J. N. 2009, Astrophys. J. Suppl. Ser., 185, 511.

  10. VLT/X-Shooter spectrum of the blazar TXS 0506+056 (located inside the IceCube-170922A error box)

    Science.gov (United States)

    Coleiro, Alexis; Chaty, Sylvain

    2017-10-01

    The blazar TXS 0506+056 (PMN J0509+0541) is currently reported to show increased gamma-ray and optical activity (ATel #10791, #10792, #10794, #10799, #10801, #10817, #10830, #10831, #10838) and has been proposed as the counterpart to the high-energy neutrino event IceCube-170922A (https://gcn.gsfc.nasa.gov/notices_amon/50579430_130033.amon).

  11. Modelling blazar flaring using a time-dependent fluid jet emission model - an explanation for orphan flares and radio lags

    Science.gov (United States)

    Potter, William J.

    2018-01-01

    Blazar jets are renowned for their rapid violent variability and multiwavelength flares, however, the physical processes responsible for these flares are not well understood. In this paper, we develop a time-dependent inhomogeneous fluid jet emission model for blazars. We model optically thick radio flares for the first time and show that they are delayed with respect to the prompt optically thin emission by ∼months to decades, with a lag that increases with the jet power and observed wavelength. This lag is caused by a combination of the travel time of the flaring plasma to the optically thin radio emitting sections of the jet and the slow rise time of the radio flare. We predict two types of flares: symmetric flares - with the same rise and decay time, which occur for flares whose duration is shorter than both the radiative lifetime and the geometric path-length delay time-scale; extended flares - whose luminosity tracks the power of particle acceleration in the flare, which occur for flares with a duration longer than both the radiative lifetime and geometric delay. Our model naturally produces orphan X-ray and γ-ray flares. These are caused by flares that are only observable above the quiescent jet emission in a narrow band of frequencies. Our model is able to successfully fit to the observed multiwavelength flaring spectra and light curves of PKS1502+106 across all wavelengths, using a transient flaring front located within the broad-line region.

  12. Sequencing BPS spectra

    Energy Technology Data Exchange (ETDEWEB)

    Gukov, Sergei [Walter Burke Institute for Theoretical Physics, California Institute of Technology,1200 E California Blvd, Pasadena, CA 91125 (United States); Max-Planck-Institut für Mathematik,Vivatsgasse 7, D-53111 Bonn (Germany); Nawata, Satoshi [Walter Burke Institute for Theoretical Physics, California Institute of Technology,1200 E California Blvd, Pasadena, CA 91125 (United States); Centre for Quantum Geometry of Moduli Spaces, University of Aarhus,Nordre Ringgade 1, DK-8000 (Denmark); Saberi, Ingmar [Walter Burke Institute for Theoretical Physics, California Institute of Technology,1200 E California Blvd, Pasadena, CA 91125 (United States); Stošić, Marko [CAMGSD, Departamento de Matemática, Instituto Superior Técnico,Av. Rovisco Pais, 1049-001 Lisbon (Portugal); Mathematical Institute SANU,Knez Mihajlova 36, 11000 Belgrade (Serbia); Sułkowski, Piotr [Walter Burke Institute for Theoretical Physics, California Institute of Technology,1200 E California Blvd, Pasadena, CA 91125 (United States); Faculty of Physics, University of Warsaw,ul. Pasteura 5, 02-093 Warsaw (Poland)

    2016-03-02

    This paper provides both a detailed study of color-dependence of link homologies, as realized in physics as certain spaces of BPS states, and a broad study of the behavior of BPS states in general. We consider how the spectrum of BPS states varies as continuous parameters of a theory are perturbed. This question can be posed in a wide variety of physical contexts, and we answer it by proposing that the relationship between unperturbed and perturbed BPS spectra is described by a spectral sequence. These general considerations unify previous applications of spectral sequence techniques to physics, and explain from a physical standpoint the appearance of many spectral sequences relating various link homology theories to one another. We also study structural properties of colored HOMFLY homology for links and evaluate Poincaré polynomials in numerous examples. Among these structural properties is a novel “sliding” property, which can be explained by using (refined) modular S-matrix. This leads to the identification of modular transformations in Chern-Simons theory and 3d N=2 theory via the 3d/3d correspondence. Lastly, we introduce the notion of associated varieties as classical limits of recursion relations of colored superpolynomials of links, and study their properties.

  13. Spectral radius of graphs

    CERN Document Server

    Stevanovic, Dragan

    2015-01-01

    Spectral Radius of Graphs provides a thorough overview of important results on the spectral radius of adjacency matrix of graphs that have appeared in the literature in the preceding ten years, most of them with proofs, and including some previously unpublished results of the author. The primer begins with a brief classical review, in order to provide the reader with a foundation for the subsequent chapters. Topics covered include spectral decomposition, the Perron-Frobenius theorem, the Rayleigh quotient, the Weyl inequalities, and the Interlacing theorem. From this introduction, the

  14. Unmixing of spectrally similar minerals

    CSIR Research Space (South Africa)

    Debba, Pravesh

    2009-01-01

    Full Text Available techniques is complicated when considering very similar spectral signatures. Iron-bearing oxide/hydroxide/sulfate minerals have similar spectral signatures. The study focuses on how could estimates of abundances of spectrally similar iron-bearing oxide...

  15. MULTIWAVELENGTH EVIDENCE FOR QUASI-PERIODIC MODULATION IN THE GAMMA-RAY BLAZAR PG 1553+113

    International Nuclear Information System (INIS)

    Ackermann, M.; Buehler, R.; Ajello, M.; Albert, A.; Baldini, L.; Blandford, R. D.; Bloom, E. D.; Bottacini, E.; Caliandro, G. A.; Atwood, W. B.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Buson, S.; Becerra Gonzalez, J.; Bellazzini, R.; Bissaldi, E.; Bonino, R.; Bregeon, J.; Bruel, P.

    2015-01-01

    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

  16. 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.

  17. Revisiting Quasi-periodic Modulation in γ -Ray Blazar PKS 2155-304 with Fermi Pass 8 Data

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Peng-fei; Liao, Neng-hui [Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China); Yan, Da-hai; Wang, Jian-cheng, E-mail: zhangpengfee@pmo.ac.cn, E-mail: yandahai@ynao.ac.cn [Yunnan Observatory, Chinese Academy of Sciences, Kunming 650011 (China)

    2017-02-01

    We examine the gamma-ray quasi-periodic variability of PKS 2155-304 with the latest publicly available Fermi -LAT Pass 8 data, which covers the years from 2008 August to 2016 October. We produce the light curves in two ways: the exposure-weighted aperture photometry and the maximum likelihood optimization. The light curves are then analyzed by using Lomb-Scargle Periodogram (LSP) and Weighted Wavelet Z-transform, and the results reveal a significant quasi-periodicity with a period of 1.74±0.13 years and a significance of ∼4.9 σ . The constraint of multifrequencies quasi-periodic variabilities on blazar emission model is discussed.

  18. 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.

  19. 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.

  20. Vowel Inherent Spectral Change

    CERN Document Server

    Assmann, Peter

    2013-01-01

    It has been traditional in phonetic research to characterize monophthongs using a set of static formant frequencies, i.e., formant frequencies taken from a single time-point in the vowel or averaged over the time-course of the vowel. However, over the last twenty years a growing body of research has demonstrated that, at least for a number of dialects of North American English, vowels which are traditionally described as monophthongs often have substantial spectral change. Vowel Inherent Spectral Change has been observed in speakers’ productions, and has also been found to have a substantial effect on listeners’ perception. In terms of acoustics, the traditional categorical distinction between monophthongs and diphthongs can be replaced by a gradient description of dynamic spectral patterns. This book includes chapters addressing various aspects of vowel inherent spectral change (VISC), including theoretical and experimental studies of the perceptually relevant aspects of VISC, the relationship between ar...

  1. High Resolution Spectral Analysis

    Science.gov (United States)

    2006-10-25

    liable methods for high resolution spectral analysis of multivariable processes, as well as to distance measures for quantitative assessment of...called "modern nonlinear spectral analysis methods " [27]. An alternative way to reconstruct /„(#), based on Tn, is the periodogram/correlogram f{6...eie). A homotopy method was proposed in [8, 9] leading to a differential equation for A(T) in a homotopy variable r. If the statistics are consistent

  2. Spectrally selective glazings

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-08-01

    Spectrally selective glazing is window glass that permits some portions of the solar spectrum to enter a building while blocking others. This high-performance glazing admits as much daylight as possible while preventing transmission of as much solar heat as possible. By controlling solar heat gains in summer, preventing loss of interior heat in winter, and allowing occupants to reduce electric lighting use by making maximum use of daylight, spectrally selective glazing significantly reduces building energy consumption and peak demand. Because new spectrally selective glazings can have a virtually clear appearance, they admit more daylight and permit much brighter, more open views to the outside while still providing the solar control of the dark, reflective energy-efficient glass of the past. This Federal Technology Alert provides detailed information and procedures for Federal energy managers to consider spectrally selective glazings. The principle of spectrally selective glazings is explained. Benefits related to energy efficiency and other architectural criteria are delineated. Guidelines are provided for appropriate application of spectrally selective glazing, and step-by-step instructions are given for estimating energy savings. Case studies are also presented to illustrate actual costs and energy savings. Current manufacturers, technology users, and references for further reading are included for users who have questions not fully addressed here.

  3. Semiclassical Theory of Spectral Rigidity

    Science.gov (United States)

    Berry, M. V.

    1985-08-01

    The spectral rigidity Δ(L) of a set of quantal energy levels is the mean square deviation of the spectral staircase from the straight line that best fits it over a range of L mean level spacings. In the semiclassical limit (hslash-> 0), formulae are obtained giving Δ(L) as a sum over classical periodic orbits. When L ~= Lmax, where Lmax ~ hslash-(N-1) for a system of N freedoms, Δ(L) is shown to display the following universal behaviour as a result of properties of very long classical orbits: if the system is classically integrable (all periodic orbits filling tori), Δ(L) = 1/15L (as in an uncorrelated (Poisson) eigenvalue sequence); if the system is classically chaotic (all periodic orbits isolated and unstable) and has no symmetry, Δ(L) = ln L/2π^2 + D if 1 ~= L ~= Lmax (as in the gaussian unitary ensemble of random-matrix theory); if the system is chaotic and has time-reversal symmetry, Δ(L) = ln L/π^2 + E if 1 ~= L ~= Lmax (as in the gaussian orthogonal ensemble). When L >> Lmax, Δ(L) saturates non-universally at a value, determined by short classical orbits, of order hslash-(N-1) for integrable systems and ln (hslash-1) for chaotic systems. These results are obtained by using the periodic-orbit expansion for the spectral density, together with classical sum rules for the intensities of long orbits and a semiclassical sum rule restricting the manner in which their contributions interfere. For two examples Δ(L) is studied in detail: the rectangular billiard (integrable), and the Riemann zeta function (assuming its zeros to be the eigenvalues of an unknown quantum system whose unknown classical limit is chaotic).

  4. Journal of Astrophysics and Astronomy | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... Keywords. Blazars; spectral energy distributions; gamma-ray emission; radio emission; host galaxies; blazar demographics; redshifts; polarization; Yung Wing; optical emissions; emission mechanism; black holes.

  5. Automatic sequences

    CERN Document Server

    Haeseler, Friedrich

    2003-01-01

    Automatic sequences are sequences which are produced by a finite automaton. Although they are not random they may look as being random. They are complicated, in the sense of not being not ultimately periodic, they may look rather complicated, in the sense that it may not be easy to name the rule by which the sequence is generated, however there exists a rule which generates the sequence. The concept automatic sequences has special applications in algebra, number theory, finite automata and formal languages, combinatorics on words. The text deals with different aspects of automatic sequences, in particular:· a general introduction to automatic sequences· the basic (combinatorial) properties of automatic sequences· the algebraic approach to automatic sequences· geometric objects related to automatic sequences.

  6. Methods for the Quasi-Periodic Variability Analysis in Blazars Y. Liu ...

    Indian Academy of Sciences (India)

    Abstract. In this work, four methods are introduced to analyse the un- evenly sampled data. The four methods are power spectral density, auto- correlation function, structure function and Jurkevich method. Some interesting mathematical links are derived amongst the four methods. These links show that the four methods ...

  7. Temporal and spectral interaction in loudness perception

    DEFF Research Database (Denmark)

    Pedersen, Benjamin; Ellermeier, Wolfgang

    An experiment was conducted to investigate how changes in spectral content influence loudness judgments. Six listeners were asked to discriminate sounds, which were of one second duration and changing in level every 0.1 s. In one condition the first half of the sound was low-pass filtered and the....... This outcome is inconsistent with overall temporal integration, and argues for a cognitive mechanism allocating attention to changes in an event sequence....

  8. UNVEILING THE NATURE OF THE UNIDENTIFIED GAMMA-RAY SOURCES. III. GAMMA-RAY BLAZAR-LIKE COUNTERPARTS AT LOW RADIO FREQUENCIES

    Energy Technology Data Exchange (ETDEWEB)

    Massaro, F.; Funk, S. [SLAC National Laboratory and Kavli Institute for Particle Astrophysics and Cosmology, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States); D' Abrusco, R.; Paggi, A. [Harvard-Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Giroletti, M. [INAF Istituto di Radioastronomia, via Gobetti 101, I-40129 Bologna (Italy); Masetti, N. [INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, via Gobetti 101, I-40129 Bologna (Italy); Tosti, G. [Dipartimento di Fisica, Universita degli Studi di Perugia, I-06123 Perugia (Italy); Nori, M. [Department of Physics and Astronomy, University of Bologna, viale Berti Pichat 6/2, I-40127 Bologna (Italy)

    2013-07-01

    About one-third of the {gamma}-ray sources listed in the second Fermi Large Area Telescope catalog (2FGL) have no firmly established counterpart at lower energies and so are classified as unidentified gamma-ray sources (UGSs). Here, we propose a new approach to find candidate counterparts for the UGSs based on the 325 MHz radio survey performed with the Westerbork Synthesis Radio Telescope in the northern hemisphere. First, we investigate the low-frequency radio properties of blazars, the largest known population of {gamma}-ray sources; then we search for sources with similar radio properties combining the information derived from the Westerbork Northern Sky Survey (WENSS) with those of the NRAO Very Large Array Sky Survey. We present a list of candidate counterparts for 32 UGSs with at least one counterpart in the WENSS. We also performed an extensive research in the literature to look for infrared and optical counterparts of the {gamma}-ray blazar candidates selected using the low-frequency radio observations to confirm their nature. On the basis of our multifrequency research, we identify 23 new {gamma}-ray blazar candidates out of the 32 UGSs investigated. Comparison with previous results on the UGSs is also presented. Finally, we speculate on the advantages of using low-frequency radio observations to associate UGSs and to search for {gamma}-ray pulsar candidates.

  9. Constraining the physical conditions in the jets of γ-ray flaring blazars using centimeter-band polarimetry and radiative transfer simulations. I. Data and models for 0420–014, OJ 287, and 1156+295

    Energy Technology Data Exchange (ETDEWEB)

    Aller, M. F.; Hughes, P. A.; Aller, H. D.; Latimer, G. E. [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109-1042 (United States); Hovatta, T., E-mail: mfa@umich.edu [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States)

    2014-08-10

    To investigate parsec-scale jet flow conditions during GeV γ-ray flares detected by the Fermi Large Angle Telescope, we obtained centimeter-band total flux density and linear polarization monitoring observations from 2009.5 through 2012.5 with the 26 m Michigan radio telescope for a sample of core-dominated blazars. We use these data to constrain radiative transfer simulations incorporating propagating shocks oriented at an arbitrary angle to the flow direction in order to set limits on the jet flow and shock parameters during flares temporally associated with γ-ray flares in 0420–014, OJ 287, and 1156+295; these active galactic nuclei exhibited the expected signature of shocks in the linear polarization data. Both the number of shocks comprising an individual radio outburst (3 and 4) and the range of the compression ratios of the individual shocks (0.5-0.8) are similar in all three sources; the shocks are found to be forward-moving with respect to the flow. While simulations incorporating transverse shocks provide good fits for 0420–014 and 1156+295, oblique shocks are required for modeling the OJ 287 outburst, and an unusually low value of the low-energy cutoff of the radiating particles' energy distribution is also identified. Our derived viewing angles and shock speeds are consistent with independent Very Long Baseline Array results. While a random component dominates the jet magnetic field, as evidenced by the low fractional linear polarization, to reproduce the observed spectral character requires that a significant fraction of the magnetic field energy is in an ordered axial component. Both straight and low pitch angle helical field lines are viable scenarios.

  10. CRISS power spectral density

    International Nuclear Information System (INIS)

    Vaeth, W.

    1979-04-01

    The correlation of signal components at different frequencies like higher harmonics cannot be detected by a normal power spectral density measurement, since this technique correlates only components at the same frequency. This paper describes a special method for measuring the correlation of two signal components at different frequencies: the CRISS power spectral density. From this new function in frequency analysis, the correlation of two components can be determined quantitatively either they stem from one signal or from two diverse signals. The principle of the method, suitable for the higher harmonics of a signal as well as for any other frequency combinations is shown for the digital frequency analysis technique. Two examples of CRISS power spectral densities demonstrates the operation of the new method. (orig.) [de

  11. Parametric Explosion Spectral Model

    Energy Technology Data Exchange (ETDEWEB)

    Ford, S R; Walter, W R

    2012-01-19

    Small underground nuclear explosions need to be confidently detected, identified, and characterized in regions of the world where they have never before occurred. We develop a parametric model of the nuclear explosion seismic source spectrum derived from regional phases that is compatible with earthquake-based geometrical spreading and attenuation. Earthquake spectra are fit with a generalized version of the Brune spectrum, which is a three-parameter model that describes the long-period level, corner-frequency, and spectral slope at high-frequencies. Explosion spectra can be fit with similar spectral models whose parameters are then correlated with near-source geology and containment conditions. We observe a correlation of high gas-porosity (low-strength) with increased spectral slope. The relationship between the parametric equations and the geologic and containment conditions will assist in our physical understanding of the nuclear explosion source.

  12. SPECTRAL ENERGY DISTRIBUTION OF MARKARIAN 501: QUIESCENT STATE VERSUS EXTREME OUTBURST

    International Nuclear Information System (INIS)

    Acciari, V. A.; Benbow, W.; Arlen, T.; Aune, T.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Dickherber, R.; Boettcher, M.; Boltuch, D.; Bradbury, S. M.; Cannon, A.; Cesarini, A.; Ciupik, L.; Cui, W.; Finley, J. P.; Duke, C.; Errando, M.; Falcone, A.; Finnegan, G.

    2011-01-01

    The very high energy (VHE; E > 100 GeV) blazar Markarian 501 (Mrk 501) has a well-studied history of extreme spectral variability and is an excellent laboratory for studying the physical processes within the jets of active galactic nuclei. However, there are few detailed multiwavelength studies of Mrk 501 during its quiescent state, due to its low luminosity. A short-term multiwavelength study of Mrk 501 was coordinated in 2009 March, focusing around a multi-day observation with the Suzaku X-ray satellite and including γ-ray data from VERITAS, MAGIC, and the Fermi Gamma-ray Space Telescope with the goal of providing a well-sampled multiwavelength baseline measurement of Mrk 501 in the quiescent state. The results of these quiescent-state observations are compared to the historically extreme outburst of 1997 April 16, with the goal of examining variability of the spectral energy distribution (SED) between the two states. The derived broadband SED shows the characteristic double-peaked profile. We find that the X-ray peak shifts by over two orders of magnitude in photon energy between the two flux states while the VHE peak varies little. The limited shift in the VHE peak can be explained by the transition to the Klein-Nishina (KN) regime. Synchrotron self-Compton models are matched to the data and the implied KN effects are explored.

  13. Identification of Interesting Objects in Large Spectral Surveys Using Highly Parallelized Machine Learning

    Science.gov (United States)

    Škoda, Petr; Palička, Andrej; Koza, Jakub; Shakurova, Ksenia

    2017-06-01

    The current archives of LAMOST multi-object spectrograph contain millions of fully reduced spectra, from which the automatic pipelines have produced catalogues of many parameters of individual objects, including their approximate spectral classification. This is, however, mostly based on the global shape of the whole spectrum and on integral properties of spectra in given bandpasses, namely presence and equivalent width of prominent spectral lines, while for identification of some interesting object types (e.g. Be stars or quasars) the detailed shape of only a few lines is crucial. Here the machine learning is bringing a new methodology capable of improving the reliability of classification of such objects even in boundary cases. We present results of Spark-based semi-supervised machine learning of LAMOST spectra attempting to automatically identify the single and double-peak emission of Hα line typical for Be and B[e] stars. The labelled sample was obtained from archive of 2m Perek telescope at Ondřejov observatory. A simple physical model of spectrograph resolution was used in domain adaptation to LAMOST training domain. The resulting list of candidates contains dozens of Be stars (some are likely yet unknown), but also a bunch of interesting objects resembling spectra of quasars and even blazars, as well as many instrumental artefacts. The verification of a nature of interesting candidates benefited considerably from cross-matching and visualisation in the Virtual Observatory environment.

  14. Spectral analysis by correlation

    International Nuclear Information System (INIS)

    Fauque, J.M.; Berthier, D.; Max, J.; Bonnet, G.

    1969-01-01

    The spectral density of a signal, which represents its power distribution along the frequency axis, is a function which is of great importance, finding many uses in all fields concerned with the processing of the signal (process identification, vibrational analysis, etc...). Amongst all the possible methods for calculating this function, the correlation method (correlation function calculation + Fourier transformation) is the most promising, mainly because of its simplicity and of the results it yields. The study carried out here will lead to the construction of an apparatus which, coupled with a correlator, will constitute a set of equipment for spectral analysis in real time covering the frequency range 0 to 5 MHz. (author) [fr

  15. Spectral Ensemble Kalman Filters

    Czech Academy of Sciences Publication Activity Database

    Mandel, Jan; Kasanický, Ivan; Vejmelka, Martin; Fuglík, Viktor; Turčičová, Marie; Eben, Kryštof; Resler, Jaroslav; Juruš, Pavel

    2014-01-01

    Roč. 11, - (2014), EMS2014-446 [EMS Annual Meeting /14./ & European Conference on Applied Climatology (ECAC) /10./. 06.10.2014-10.10.2014, Prague] R&D Projects: GA ČR GA13-34856S Grant - others:NSF DMS -1216481 Institutional support: RVO:67985807 Keywords : data assimilation * spectral filter Subject RIV: DG - Athmosphere Sciences, Meteorology

  16. Code aperture optimization for spectrally agile compressive imaging.

    Science.gov (United States)

    Arguello, Henry; Arce, Gonzalo R

    2011-11-01

    Coded aperture snapshot spectral imaging (CASSI) provides a mechanism for capturing a 3D spectral cube with a single shot 2D measurement. In many applications selective spectral imaging is sought since relevant information often lies within a subset of spectral bands. Capturing and reconstructing all the spectral bands in the observed image cube, to then throw away a large portion of this data, is inefficient. To this end, this paper extends the concept of CASSI to a system admitting multiple shot measurements, which leads not only to higher quality of reconstruction but also to spectrally selective imaging when the sequence of code aperture patterns is optimized. The aperture code optimization problem is shown to be analogous to the optimization of a constrained multichannel filter bank. The optimal code apertures allow the decomposition of the CASSI measurement into several subsets, each having information from only a few selected spectral bands. The rich theory of compressive sensing is used to effectively reconstruct the spectral bands of interest from the measurements. A number of simulations are developed to illustrate the spectral imaging characteristics attained by optimal aperture codes.

  17. A Simple Spectral Observer

    Directory of Open Access Journals (Sweden)

    Lizeth Torres

    2018-05-01

    Full Text Available The principal aim of a spectral observer is twofold: the reconstruction of a signal of time via state estimation and the decomposition of such a signal into the frequencies that make it up. A spectral observer can be catalogued as an online algorithm for time-frequency analysis because is a method that can compute on the fly the Fourier transform (FT of a signal, without having the entire signal available from the start. In this regard, this paper presents a novel spectral observer with an adjustable constant gain for reconstructing a given signal by means of the recursive identification of the coefficients of a Fourier series. The reconstruction or estimation of a signal in the context of this work means to find the coefficients of a linear combination of sines a cosines that fits a signal such that it can be reproduced. The design procedure of the spectral observer is presented along with the following applications: (1 the reconstruction of a simple periodical signal, (2 the approximation of both a square and a triangular signal, (3 the edge detection in signals by using the Fourier coefficients, (4 the fitting of the historical Bitcoin market data from 1 December 2014 to 8 January 2018 and (5 the estimation of a input force acting upon a Duffing oscillator. To round out this paper, we present a detailed discussion about the results of the applications as well as a comparative analysis of the proposed spectral observer vis-à-vis the Short Time Fourier Transform (STFT, which is a well-known method for time-frequency analysis.

  18. Wavelength conversion based spectral imaging

    DEFF Research Database (Denmark)

    Dam, Jeppe Seidelin

    There has been a strong, application driven development of Si-based cameras and spectrometers for imaging and spectral analysis of light in the visible and near infrared spectral range. This has resulted in very efficient devices, with high quantum efficiency, good signal to noise ratio and high...... resolution for this spectral region. Today, an increasing number of applications exists outside the spectral region covered by Si-based devices, e.g. within cleantech, medical or food imaging. We present a technology based on wavelength conversion which will extend the spectral coverage of state of the art...... visible or near infrared cameras and spectrometers to include other spectral regions of interest....

  19. Spectral Efficiency of OCDMA Systems With Coherent Pulsed Sources

    Science.gov (United States)

    Rochette, Martin; Rusch, Leslie A.

    2005-03-01

    We present a model to evaluate the upper limit of the spectral efficiency of optical code-division multiple-access (OCDMA) systems with coherent sources. Phase-encoded and direct-sequence OCDMA systems are evaluated using this model. The results show that a spectral efficiency of 2.24x10^-2 b/s.Hz can be achieved with a maximum bit error rate of 10^-10 in these systems of the number of users. This result demonstrates that the maximum spectral efficiency of OCDMA systems with coherent sources is at least a factor of 5 higher than OCDMA systems with incoherent sources.

  20. FERMI LARGE AREA TELESCOPE OBSERVATIONS OF MARKARIAN 421: THE MISSING PIECE OF ITS SPECTRAL ENERGY DISTRIBUTION

    International Nuclear Information System (INIS)

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Borgland, A. W.; Buehler, R.; Baldini, L.; Bellazzini, R.; Bregeon, J.; Brez, A.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bonamente, E.; Bouvier, A.; Brigida, M.; Bruel, P.

    2011-01-01

    We report on the γ-ray activity of the high-synchrotron-peaked BL Lacertae object Markarian 421 (Mrk 421) during the first 1.5 years of Fermi operation, from 2008 August 5 to 2010 March 12. We find that the Large Area Telescope (LAT) γ-ray spectrum above 0.3 GeV can be well described by a power-law function with photon index Γ = 1.78 ± 0.02 and average photon flux F(> 0.3 GeV) = (7.23 ± 0.16) x 10 -8 ph cm -2 s -1 . Over this time period, the Fermi-LAT spectrum above 0.3 GeV was evaluated on seven-day-long time intervals, showing significant variations in the photon flux (up to a factor ∼3 from the minimum to the maximum flux) but mild spectral variations. The variability amplitude at X-ray frequencies measured by RXTE/ASM and Swift/BAT is substantially larger than that in γ-rays measured by Fermi-LAT, and these two energy ranges are not significantly correlated. We also present the first results from the 4.5 month long multifrequency campaign on Mrk 421, which included the VLBA, Swift, RXTE, MAGIC, the F-GAMMA, GASP-WEBT, and other collaborations and instruments that provided excellent temporal and energy coverage of the source throughout the entire campaign (2009 January 19 to 2009 June 1). During this campaign, Mrk 421 showed a low activity at all wavebands. The extensive multi-instrument (radio to TeV) data set provides an unprecedented, complete look at the quiescent spectral energy distribution (SED) for this source. The broadband SED was reproduced with a leptonic (one-zone synchrotron self-Compton) and a hadronic model (synchrotron proton blazar). Both frameworks are able to describe the average SED reasonably well, implying comparable jet powers but very different characteristics for the blazar emission site.

  1. A spectral algorithm for the seriation problem

    Energy Technology Data Exchange (ETDEWEB)

    Atkins, J.E. [Michigan Univ., Ann Arbor, MI (United States). Dept. of Mathematics; Boman, E.G. [Stanford Univ., CA (United States). Dept. of Computer Science; Hendrickson, B. [Sandia National Labs., Albuquerque, NM (United States)

    1994-11-01

    Given a set of objects and a correlation function f reflecting the desire for two items to be near each other, find all sequences {pi} of the items so that correlation preferences are preserved; that is if {pi}(i) < {pi}(j) < {pi}(k) then f(i,j) {ge} f(i,k) and f(j,k) {ge} f(i,k). This seriation problem has numerous applications, for instance, solving it yields a solution to the consecutive ones problem. We present a spectral algorithm for this problem that has a number of interesting features. Whereas most previous applications of spectral techniques provided bounds or heuristics, our result is an algorithm for a nontrivial combinatorial problem. Our analysis introduces powerful tools from matrix theory to the theoretical computer science community. Also, spectral methods are being applied as heuristics for a variety of sequencing problems and our result helps explain and justify these applications. Although the worst case running time for our approach is not competitive with that of existing methods for well posed problem instances, unlike combinatorial approaches our algorithm remains a credible heuristic for the important cases where there are errors in the data.

  2. Genome Sequencing

    DEFF Research Database (Denmark)

    Sato, Shusei; Andersen, Stig Uggerhøj

    2014-01-01

    The current Lotus japonicus reference genome sequence is based on a hybrid assembly of Sanger TAC/BAC, Sanger shotgun and Illumina shotgun sequencing data generated from the Miyakojima-MG20 accession. It covers nearly all expressed L. japonicus genes and has been annotated mainly based...... on transcriptional evidence. Analysis of repetitive sequences suggests that they are underrepresented in the reference assembly, reflecting an enrichment of gene-rich regions in the current assembly. Characterization of Lotus natural variation by resequencing of L. japonicus accessions and diploid Lotus species...... is currently ongoing, facilitated by the MG20 reference sequence...

  3. Hybrid spectral CT reconstruction

    Science.gov (United States)

    Clark, Darin P.

    2017-01-01

    Current photon counting x-ray detector (PCD) technology faces limitations associated with spectral fidelity and photon starvation. One strategy for addressing these limitations is to supplement PCD data with high-resolution, low-noise data acquired with an energy-integrating detector (EID). In this work, we propose an iterative, hybrid reconstruction technique which combines the spectral properties of PCD data with the resolution and signal-to-noise characteristics of EID data. Our hybrid reconstruction technique is based on an algebraic model of data fidelity which substitutes the EID data into the data fidelity term associated with the PCD reconstruction, resulting in a joint reconstruction problem. Within the split Bregman framework, these data fidelity constraints are minimized subject to additional constraints on spectral rank and on joint intensity-gradient sparsity measured between the reconstructions of the EID and PCD data. Following a derivation of the proposed technique, we apply it to the reconstruction of a digital phantom which contains realistic concentrations of iodine, barium, and calcium encountered in small-animal micro-CT. The results of this experiment suggest reliable separation and detection of iodine at concentrations ≥ 5 mg/ml and barium at concentrations ≥ 10 mg/ml in 2-mm features for EID and PCD data reconstructed with inherent spatial resolutions of 176 μm and 254 μm, respectively (point spread function, FWHM). Furthermore, hybrid reconstruction is demonstrated to enhance spatial resolution within material decomposition results and to improve low-contrast detectability by as much as 2.6 times relative to reconstruction with PCD data only. The parameters of the simulation experiment are based on an in vivo micro-CT experiment conducted in a mouse model of soft-tissue sarcoma. Material decomposition results produced from this in vivo data demonstrate the feasibility of distinguishing two K-edge contrast agents with a spectral

  4. Context Dependent Spectral Unmixing

    Science.gov (United States)

    2014-08-01

    remote sensing [1–13]. It is also used in food safety [14–17], pharmaceutical process monitoring and quality control [18–22], as well as in biomedical...23,24], industrial [25], biometric [26] and forensic applications [27]. Hyperspectral sensors capture both the spatial and spectral information of a...imagery,” IEEE Signal Processing Magazine, vol. 19, no. 1, pp. 58–69, 2002. [12] A. Plaza, J. A. Benediktsson, J. W. Boardman, J. Brazile , L. Bruzzone, G

  5. Hybrid spectral CT reconstruction.

    Directory of Open Access Journals (Sweden)

    Darin P Clark

    Full Text Available Current photon counting x-ray detector (PCD technology faces limitations associated with spectral fidelity and photon starvation. One strategy for addressing these limitations is to supplement PCD data with high-resolution, low-noise data acquired with an energy-integrating detector (EID. In this work, we propose an iterative, hybrid reconstruction technique which combines the spectral properties of PCD data with the resolution and signal-to-noise characteristics of EID data. Our hybrid reconstruction technique is based on an algebraic model of data fidelity which substitutes the EID data into the data fidelity term associated with the PCD reconstruction, resulting in a joint reconstruction problem. Within the split Bregman framework, these data fidelity constraints are minimized subject to additional constraints on spectral rank and on joint intensity-gradient sparsity measured between the reconstructions of the EID and PCD data. Following a derivation of the proposed technique, we apply it to the reconstruction of a digital phantom which contains realistic concentrations of iodine, barium, and calcium encountered in small-animal micro-CT. The results of this experiment suggest reliable separation and detection of iodine at concentrations ≥ 5 mg/ml and barium at concentrations ≥ 10 mg/ml in 2-mm features for EID and PCD data reconstructed with inherent spatial resolutions of 176 μm and 254 μm, respectively (point spread function, FWHM. Furthermore, hybrid reconstruction is demonstrated to enhance spatial resolution within material decomposition results and to improve low-contrast detectability by as much as 2.6 times relative to reconstruction with PCD data only. The parameters of the simulation experiment are based on an in vivo micro-CT experiment conducted in a mouse model of soft-tissue sarcoma. Material decomposition results produced from this in vivo data demonstrate the feasibility of distinguishing two K-edge contrast agents with

  6. Spectral distributions and symmetries

    International Nuclear Information System (INIS)

    Quesne, C.

    1980-01-01

    As it is now well known, the spectral distribution method has both statistical and group theoretical aspects which make for great simplifications in many-Fermion system calculations with respect to more conventional ones. Although both aspects intertwine and are equally essential to understand what is going on, we are only going to discuss some of the group theoretical aspects, namely those connected with the propagation of information, in view of their fundamental importance for the actual calculations of spectral distributions. To be more precise, let us recall that the spectral distribution method may be applied in principle to many-Fermion spaces which have a direct-product structure, i.e., are obtained by distributing a certain number n of Fermions over N single-particle states (O less than or equal to n less than or equal to N), as it is the case for instance for the nuclear shell model spaces. For such systems, the operation of a central limit theorem is known to provide us with a simplifying principle which, when used in conjunction with exact or broken symmetries, enables us to make definite predictions in those cases which are not amendable to exact shell model diagonalizations. The distribution (in energy) of the states corresponding to a fixed symmetry is then defined by a small number of low-order energy moments. Since the Hamiltonian is defined in few-particle subspaces embedded in the n-particlespace, the low-order moments, we are interested in, can be expressed in terms of simpler quantities defined in those few-particle subspaces: the information is said to propagate from the simple subspaces to the more complicated ones. The possibility of actually calculating spectral distributions depends upon the finding of simple ways to propagate the information

  7. Spectral and Diffraction Tomography

    OpenAIRE

    Lionheart, William

    2016-01-01

    We discuss several cases of what we call "Rich Tomography" problems in which more data is measured than a scalar for each ray. We give examples of infra red spectral tomography and Bragg edge neutron tomography in which the data is insufficient. For diffraction tomography of strain for polycrystaline materials we give an explicit reconstruction procedure. We go on to describe a way to find six independent rotation axes using Pascal's theorem of projective geometry

  8. Mechanical spectral shift reactor

    International Nuclear Information System (INIS)

    Wilson, J.F.; Sherwood, D.G.

    1982-01-01

    A mechanical spectral shift reactor comprises a reactive core having fuel assemblies accommodating both water displacer elements and neutron absorbing control rods for selectively changing the volume of water-moderator in the core. The fuel assemblies with displacer and control rods are arranged in alternating fashion so that one displacer element drive mechanism may move displacer elements in more than one fuel assembly without interfering with the movement of control rods of a corresponding control rod drive mechanisms. (author)

  9. Long-Term Multi-Band and Polarimetric View of Mkn 421: Motivations for an Integrated Open-Data Platform for Blazar Optical Polarimetry

    Directory of Open Access Journals (Sweden)

    Ulisses Barres de Almeida

    2017-11-01

    Full Text Available In this work, by making use of the large software and database resources made available through online facilities such as the ASI Science Data Center (ASDC, we present a novel approach to the modelling of blazar emission whereby the multi-epoch SED for Mkn 421 is modelled considering, in a self-consistent way, the temporal lags between bands (both in short and long-timescales. These are obtained via a detailed cross-correlation analysis, spanning data from radio to VHE gamma-rays from 2008 to 2015. In addition to that, long-term optical polarisation data is used to aid and complement our physical interpretation of the state and evolution of the source. Blazar studies constitute a clear example that astrophysics is becoming increasingly dominated by “big data”. Specific questions, such as the interpretation of polarimetric information—namely the evolution of the polarisation degree (PD and specially the polarisation angle (PA of a source—are very sensitive to the density of data coverage. Improving data accessibility and integration, in order to respond to these necessities, is thus extremely important and has a potentially large impact for blazar science. For this reason, we present also the project to create an open-access database for optical polarimetry, aiming to circumvent the issues raised above, by integrating long-term optical polarisation information on a number sources from several observatories and data providers in a consistent way. The platform, to be launched by the end of 2017 is built as part of the Brazilian Science Data Center (BSDC, a project hosted at CBPF, in Rio de Janeiro, and developed with the support of the Italian Space Agency (ASI and ICRANet. The BSDC is Virtual Observatory-compliant and is built in line with “Open Universe”, a global space science open-data initiative to be launched in November under the auspices of the United Nations.

  10. THE DISCOVERY OF γ-RAY EMISSION FROM THE BLAZAR RGB J0710+591

    International Nuclear Information System (INIS)

    Acciari, V. A.; Benbow, W.; Aliu, E.; Arlen, T.; Aune, T.; Bautista, M.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Dickherber, R.; Boettcher, M.; Boltuch, D.; Bradbury, S. M.; Byrum, K.; Cannon, A.; Cesarini, A.; Ciupik, L.; Cui, W.; Duke, C.; Falcone, A.

    2010-01-01

    The high-frequency-peaked BL Lacertae object RGB J0710+591 was observed in the very high-energy (VHE; E > 100 GeV) wave band by the VERITAS array of atmospheric Cherenkov telescopes. The observations, taken between 2008 December and 2009 March and totaling 22.1 hr, yield the discovery of VHE gamma rays from the source. RGB J0710+591 is detected at a statistical significance of 5.5 standard deviations (5.5σ) above the background, corresponding to an integral flux of (3.9 ± 0.8) x 10 -12 cm -2 s -1 (3% of the Crab Nebula's flux) above 300 GeV. The observed spectrum can be fit by a power law from 0.31 to 4.6 TeV with a photon spectral index of 2.69 ± 0.26 stat ± 0.20 sys . These data are complemented by contemporaneous multiwavelength data from the Fermi Large Area Telescope, the Swift X-ray Telescope, the Swift Ultra-Violet and Optical Telescope, and the Michigan-Dartmouth-MIT observatory. Modeling the broadband spectral energy distribution (SED) with an equilibrium synchrotron self-Compton model yields a good statistical fit to the data. The addition of an external-Compton component to the model does not improve the fit nor brings the system closer to equipartition. The combined Fermi and VERITAS data constrain the properties of the high-energy emission component of the source over 4 orders of magnitude and give measurements of the rising and falling sections of the SED.

  11. QCD spectral sum rules

    CERN Document Server

    Narison, Stéphan

    The aim of the book is to give an introduction to the method of QCD Spectral Sum Rules and to review its developments. After some general introductory remarks, Chiral Symmetry, the Historical Developments of the Sum Rules and the necessary materials for perturbative QCD including the MS regularization and renormalization schemes are discussed. The book also gives a critical review and some improvements of the wide uses of the QSSR in Hadron Physics and QSSR beyond the Standard Hadron Phenomenology. The author has participated actively in this field since 1978 just before the expanding success

  12. Spectral signatures of chirality

    DEFF Research Database (Denmark)

    Pedersen, Jesper Goor; Mortensen, Asger

    2009-01-01

    We present a new way of measuring chirality, via the spectral shift of photonic band gaps in one-dimensional structures. We derive an explicit mapping of the problem of oblique incidence of circularly polarized light on a chiral one-dimensional photonic crystal with negligible index contrast...... to the formally equivalent problem of linearly polarized light incident on-axis on a non-chiral structure with index contrast. We derive analytical expressions for the first-order shifts of the band gaps for negligible index contrast. These are modified to give good approximations to the band gap shifts also...

  13. On spectral pollution

    International Nuclear Information System (INIS)

    Llobet, X.; Appert, K.; Bondeson, A.; Vaclavik, J.

    1990-01-01

    Finite difference and finite element approximations of eigenvalue problems, under certain circumstances exhibit spectral pollution, i.e. the appearance of eigenvalues that do not converge to the correct value when the mesh density is increased. In the present paper this phenomenon is investigated in a homogeneous case by means of discrete dispersion relations: the polluting modes belong to a branch of the dispersion relation that is strongly distorted by the discretization method employed, or to a new, spurious branch. The analysis is applied to finite difference methods and to finite element methods, and some indications about how to avoiding polluting schemes are given. (author) 5 figs., 10 refs

  14. Dna Sequencing

    Science.gov (United States)

    Tabor, Stanley; Richardson, Charles C.

    1995-04-25

    A method for sequencing a strand of DNA, including the steps off: providing the strand of DNA; annealing the strand with a primer able to hybridize to the strand to give an annealed mixture; incubating the mixture with four deoxyribonucleoside triphosphates, a DNA polymerase, and at least three deoxyribonucleoside triphosphates in different amounts, under conditions in favoring primer extension to form nucleic acid fragments complementory to the DNA to be sequenced; labelling the nucleic and fragments; separating them and determining the position of the deoxyribonucleoside triphosphates by differences in the intensity of the labels, thereby to determine the DNA sequence.

  15. Intensity Conserving Spectral Fitting

    Science.gov (United States)

    Klimchuk, J. A.; Patsourakos, S.; Tripathi, D.

    2015-01-01

    The detailed shapes of spectral line profiles provide valuable information about the emitting plasma, especially when the plasma contains an unresolved mixture of velocities, temperatures, and densities. As a result of finite spectral resolution, the intensity measured by a spectrometer is the average intensity across a wavelength bin of non-zero size. It is assigned to the wavelength position at the center of the bin. However, the actual intensity at that discrete position will be different if the profile is curved, as it invariably is. Standard fitting routines (spline, Gaussian, etc.) do not account for this difference, and this can result in significant errors when making sensitive measurements. Detection of asymmetries in solar coronal emission lines is one example. Removal of line blends is another. We have developed an iterative procedure that corrects for this effect. It can be used with any fitting function, but we employ a cubic spline in a new analysis routine called Intensity Conserving Spline Interpolation (ICSI). As the name implies, it conserves the observed intensity within each wavelength bin, which ordinary fits do not. Given the rapid convergence, speed of computation, and ease of use, we suggest that ICSI be made a standard component of the processing pipeline for spectroscopic data.

  16. Spectral clustering for water body spectral types analysis

    Science.gov (United States)

    Huang, Leping; Li, Shijin; Wang, Lingli; Chen, Deqing

    2017-11-01

    In order to study the spectral types of water body in the whole country, the key issue of reservoir research is to obtain and to analyze the information of water body in the reservoir quantitatively and accurately. A new type of weight matrix is constructed by utilizing the spectral features and spatial features of the spectra from GF-1 remote sensing images comprehensively. Then an improved spectral clustering algorithm is proposed based on this weight matrix to cluster representative reservoirs in China. According to the internal clustering validity index which called Davies-Bouldin(DB) index, the best clustering number 7 is obtained. Compared with two clustering algorithms, the spectral clustering algorithm based only on spectral features and the K-means algorithm based on spectral features and spatial features, simulation results demonstrate that the proposed spectral clustering algorithm based on spectral features and spatial features has a higher clustering accuracy, which can better reflect the spatial clustering characteristics of representative reservoirs in various provinces in China - similar spectral properties and adjacent geographical locations.

  17. Non-stationary emission of the blazar S4 0954+658 over a wide range of wavelength

    Science.gov (United States)

    Volvach, A. E.; Bychkova, V. S.; Larionov, M. G.; Kardashev, N. S.; Volvach, L. N.; Vlasyuk, V. V.; Spiridonova, O. I.; Lähteenmäki, A.; Tornikoski, M.; Aller, M. F.; Aller, H. D.; Pooley, G.; Carrasco, L.; Porras, A.; Recillas, E.

    2016-12-01

    Data from long-term multi-frequency monitoring are used to analyze variations in the flux density of the active galactic nucleus S4 0954+658. These data were obtained at the CrimeanAstrophysical Observatory, the Metsähovi Radio Observatory of Aalto University, the University of Michigan Radio Astronomy Observatory, the Cavendish Laboratory of Cambridge University, the Special Astrophysical Observatory, and the National Institute of Astrophysics, Optics, and Electronics; 0.1-300-GeV data from the Fermi space gamma-ray observatory were also used. Radio data at 4.8, 8, 14.5, 15, 22.2, and 36.8 GHz are considered together with optical and near-infrared data in the R, J, H, and K filters. In the framework of a model in which binary supermassive black holes (SMBHs) are present in active galactic nuclei, harmonic and structural analyses are carried out to establish the orbital ( T orb ≈ 780 yrs) and precessional ( T pr ≈ 7800 yrs) periods in the rest frame of the source. The development of the most powerful flare ever observed in this object, which occurred in February 2015, is considered. The delay in the flare's development in different wavelength ranges from the gamma-ray to the radio is determined. both the magnitude of the delays and the durations of the flares themselves suggest that the physical characteristics of S4 0954+658 are similar to those of the blazar S5 0716+714, which displays evidence of a high γ factor for the jet motion and high superluminal speeds in the jet. The masses of the components of the binary SMBH ( M and m), the dimensions of their orbit, and the velocity of the lower-mass SMBH about the central SMBH are estimated. The derived physical characteristics are subject to a comparative analysis.

  18. 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.

  19. THE SEARCH FOR BLAZARS AMONG THE UNIDENTIFIED EGRET gamma-RAY SOURCES

    Directory of Open Access Journals (Sweden)

    Pieter J. Meintjes

    2013-12-01

    Full Text Available In this paper we report the results of a multi-wavelength follow-up study of selected flat spectrum extragalactic radio-optical counterparts within the error boxes of 13 unidentified EGRET sources. Two of these previously unidentified counterparts have been selected for optical photometric and spectroscopic follow-up studies. Spectroscopic observations made with the 4.1m SOAR telescope at Cerro Pachón, Chile, showed that the spectra of the optical counterparts of 3EG J0821−5814 (PKS J0820−5705 and 3EG J0706−3837 (PMN J0710−3835 correspond to a flat spectrum radio quasar (FSRQ and LINER-Seyfert I galaxy respectively. Optical photometry of these sources, performed with the 1.0m telescope at Sutherland (South-Africa shows noticeable intranight variability for PKS J0820−5705, as well as a 5 sigma variation of the mean brightness in the R-filter over a timescale of three nights. Significant variability has been detected in the B-band for PMN J0710−3835 as well. The gamma-ray spectral indices of all 13 candidates range between 2–3, correlating well with the BL Lacs and FSRQs detected with Fermi-LAT in the first 11 months of operation.

  20. Low-luminosity Blazars in Wise: A Mid-infrared View of Unification

    Science.gov (United States)

    Plotkin, Richard M.; Anderson, S. F.; Brandt, W. N.; Markoff, S.; Shemmer, O.; Wu, J.

    2012-01-01

    We use the preliminary data release from the Wide-Field Infrared Survey Explorer (WISE) to perform the first statistical study on the mid-infrared (IR) properties of a large number ( 102) of BL Lac objects -- low-luminosity Active Galactic Nuclei (AGN) with a jet beamed toward the Earth. As expected, many BL Lac objects are so highly beamed that their jet synchrotron emission dominates their IR spectral energy distributions (SEDs), and the shape of their SEDs in the IR correlates well with SED peak frequency. In other BL Lac objects, the jet is not strong enough to completely dilute the rest of the AGN, and we do not see observational signatures of the dusty torus from these weakly beamed BL Lac objects. While at odds with simple unification, the missing torus is consistent with recent suggestions that BL Lac objects are fed by radiatively inefficient accretion flows. We discuss implications on the ``nature vs. nurture" debate for FR I and FR II galaxies, and also on the standard orientation-based AGN unification model.

  1. Spectral Automorphisms in Quantum Logics

    Science.gov (United States)

    Ivanov, Alexandru; Caragheorgheopol, Dan

    2010-12-01

    In quantum mechanics, the Hilbert space formalism might be physically justified in terms of some axioms based on the orthomodular lattice (OML) mathematical structure (Piron in Foundations of Quantum Physics, Benjamin, Reading, 1976). We intend to investigate the extent to which some fundamental physical facts can be described in the more general framework of OMLs, without the support of Hilbert space-specific tools. We consider the study of lattice automorphisms properties as a “substitute” for Hilbert space techniques in investigating the spectral properties of observables. This is why we introduce the notion of spectral automorphism of an OML. Properties of spectral automorphisms and of their spectra are studied. We prove that the presence of nontrivial spectral automorphisms allow us to distinguish between classical and nonclassical theories. We also prove, for finite dimensional OMLs, that for every spectral automorphism there is a basis of invariant atoms. This is an analogue of the spectral theorem for unitary operators having purely point spectrum.

  2. Rectangular spectral collocation

    KAUST Repository

    Driscoll, Tobin A.

    2015-02-06

    Boundary conditions in spectral collocation methods are typically imposed by removing some rows of the discretized differential operator and replacing them with others that enforce the required conditions at the boundary. A new approach based upon resampling differentiated polynomials into a lower-degree subspace makes differentiation matrices, and operators built from them, rectangular without any row deletions. Then, boundary and interface conditions can be adjoined to yield a square system. The resulting method is both flexible and robust, and avoids ambiguities that arise when applying the classical row deletion method outside of two-point scalar boundary-value problems. The new method is the basis for ordinary differential equation solutions in Chebfun software, and is demonstrated for a variety of boundary-value, eigenvalue and time-dependent problems.

  3. The Advanced Spectral Library (ASTRAL) Project

    Science.gov (United States)

    Ayres, Thomas R.; The ASTRAL I & Science Teams, II

    2014-01-01

    The Advanced Spectral Library (ASTRAL) is an HST Treasury Program whose aim is to secure definitive ultraviolet (115-310 nm) spectra of representative bright stars utilizing the venerable -- yet still state-of-the-art -- Space Telescope Imaging Spectrograph (STIS). The initial Cycle 18 installment of the program (146 orbits in 2010-2011) focused on late-type (``cool’’) stars, acquiring high-S/N, high spectral resolution measurements of eight pivotal targets, including iconic objects like Betelgeuse and Procyon. The latest episode, in current Cycle 21 (230 orbits in 2013-2014), is designed to record very high-S/N (>100) STIS echellegrams, at the highest resolution feasible ( 30,000-100,000), of 21 representative bright early-type (``hot’’) stars, including equally iconic objects like Vega, Sirius, Regulus, and Zeta Puppis. The targets span a broad range of spectral types between early-O and early-A, encompassing main sequence and evolved stars, fast and slow rotators, as well as chemically peculiar and magnetic objects. These high-quality STIS UV spectra will be publicly available immediately after observation from the HST archive; and, in post-processed and merged form, at the project website: http://casa.colorado.edu ayres/ASTRAL/. The UV "atlases" produced by the ASTRAL Program will enable investigations of a broad range of astrophysical problems -- stellar, interstellar, and beyond -- for many years to come. Supported by Guest Observer grants from STScI.

  4. The Connection between the Radio Jet and the γ-ray Emission in the Radio Galaxy 3C 120 and the Blazar CTA 102

    Directory of Open Access Journals (Sweden)

    Carolina Casadio

    2016-09-01

    Full Text Available We present multi-wavelength studies of the radio galaxy 3C 120 and the blazar CTA 102 during unprecedented γ-ray flares for both sources. In both studies the analysis of γ-ray data has been compared with a series of 43 GHz VLBA images from the VLBA-BU-BLAZAR program, providing the necessary spatial resolution to probe the parsec scale jet evolution during the high energy events. To extend the radio dataset for 3C 120 we also used 15 GHz VLBA data from the MOJAVE sample. These two objects which represent very different classes of AGN, have similar properties during the γ-ray events. The γ-ray flares are associated with the passage of a new superluminal component through the mm VLBI core, but not all ejections of new components lead to γ-ray events. In both sources γ-ray events occurred only when the new components are moving in a direction closer to our line of sight. We locate the γ-ray dissipation zone a short distance from the radio core but outside of the broad line region, suggesting synchrotron self-Compton scattering as the probable mechanism for the γ-ray production.

  5. [Review of digital ground object spectral library].

    Science.gov (United States)

    Zhou, Xiao-Hu; Zhou, Ding-Wu

    2009-06-01

    A higher spectral resolution is the main direction of developing remote sensing technology, and it is quite important to set up the digital ground object reflectance spectral database library, one of fundamental research fields in remote sensing application. Remote sensing application has been increasingly relying on ground object spectral characteristics, and quantitative analysis has been developed to a new stage. The present article summarized and systematically introduced the research status quo and development trend of digital ground object reflectance spectral libraries at home and in the world in recent years. Introducing the spectral libraries has been established, including desertification spectral database library, plants spectral database library, geological spectral database library, soil spectral database library, minerals spectral database library, cloud spectral database library, snow spectral database library, the atmosphere spectral database library, rocks spectral database library, water spectral database library, meteorites spectral database library, moon rock spectral database library, and man-made materials spectral database library, mixture spectral database library, volatile compounds spectral database library, and liquids spectral database library. In the process of establishing spectral database libraries, there have been some problems, such as the lack of uniform national spectral database standard and uniform standards for the ground object features as well as the comparability between different databases. In addition, data sharing mechanism can not be carried out, etc. This article also put forward some suggestions on those problems.

  6. Spectral Theory of Chemical Bonding

    National Research Council Canada - National Science Library

    Langhoff, P. W; Boatz, J. A; Hinde, R. J; Sheehy, J. A

    2004-01-01

    New theoretical methods are reported for obtaining the binding energies of molecules and other chemical aggregates employing the spectral eigenstates and related properties of their atomic constituents...

  7. Understanding Soliton Spectral Tunneling as a Spectral Coupling Effect

    DEFF Research Database (Denmark)

    Guo, Hairun; Wang, Shaofei; Zeng, Xianglong

    2013-01-01

    Soliton eigenstate is found corresponding to a dispersive phase profile under which the soliton phase changes induced by the dispersion and nonlinearity are instantaneously counterbalanced. Much like a waveguide coupler relying on a spatial refractive index profile that supports mode coupling...... between channels, here we suggest that the soliton spectral tunneling effect can be understood supported by a spectral phase coupler. The dispersive wave number in the spectral domain must have a coupler-like symmetric profile for soliton spectral tunneling to occur. We show that such a spectral coupler...... exactly implies phase as well as group-velocity matching between the input soliton and tunneled soliton, namely a soliton phase matching condition. Examples in realistic photonic crystal fibers are also presented....

  8. The Optical Microvariability and Spectral Changes of the BL ...

    Indian Academy of Sciences (India)

    The external ones include interstellar scintillation, micro-lensing or geometric effects. The internal ones include shocks moving down the relativistic jet or insta- bilities in the accretion disk (Wagner & Witzel 1995). Studying microvariability can bring new insight into the understanding of the nature of blazars, probing into the.

  9. Event-sequence time series analysis in ground-based gamma-ray astronomy

    International Nuclear Information System (INIS)

    Barres de Almeida, U.; Chadwick, P.; Daniel, M.; Nolan, S.; McComb, L.

    2008-01-01

    The recent, extreme episodes of variability detected from Blazars by the leading atmospheric Cerenkov experiments motivate the development and application of specialized statistical techniques that enable the study of this rich data set to its furthest extent. The identification of the shortest variability timescales supported by the data and the actual variability structure observed in the light curves of these sources are some of the fundamental aspects being studied, that answers can bring new developments on the understanding of the physics of these objects and on the mechanisms of production of VHE gamma-rays in the Universe. Some of our efforts in studying the time variability of VHE sources involve the application of dynamic programming algorithms to the problem of detecting change-points in a Poisson sequence. In this particular paper we concentrate on the more primary issue of the applicability of counting statistics to the analysis of time-series on VHE gamma-ray astronomy.

  10. SPECTRAL ANALYSIS OF EXCHANGE RATES

    Directory of Open Access Journals (Sweden)

    ALEŠA LOTRIČ DOLINAR

    2013-06-01

    Full Text Available Using spectral analysis is very common in technical areas but rather unusual in economics and finance, where ARIMA and GARCH modeling are much more in use. To show that spectral analysis can be useful in determining hidden periodic components for high-frequency finance data as well, we use the example of foreign exchange rates

  11. Intersection numbers of spectral curves

    CERN Document Server

    Eynard, B

    2011-01-01

    We compute the symplectic invariants of an arbitrary spectral curve with only 1 branchpoint in terms of integrals of characteristic classes in the moduli space of curves. Our formula associates to any spectral curve, a characteristic class, which is determined by the laplace transform of the spectral curve. This is a hint to the key role of Laplace transform in mirror symmetry. When the spectral curve is y=\\sqrt{x}, the formula gives Kontsevich--Witten intersection numbers, when the spectral curve is chosen to be the Lambert function \\exp{x}=y\\exp{-y}, the formula gives the ELSV formula for Hurwitz numbers, and when one chooses the mirror of C^3 with framing f, i.e. \\exp{-x}=\\exp{-yf}(1-\\exp{-y}), the formula gives the topological vertex formula, i.e. the generating function of Gromov-Witten invariants of C^3. In some sense this formula generalizes ELSV formula, and Mumford formula.

  12. Spectral imagery collection experiment

    Science.gov (United States)

    Romano, Joao M.; Rosario, Dalton; Farley, Vincent; Sohr, Brian

    2010-04-01

    The Spectral and Polarimetric Imagery Collection Experiment (SPICE) is a collaborative effort between the US Army ARDEC and ARL for the collection of mid-wave and long-wave infrared imagery using hyperspectral, polarimetric, and broadband sensors. The objective of the program is to collect a comprehensive database of the different modalities over the course of 1 to 2 years to capture sensor performance over a wide variety of adverse weather conditions, diurnal, and seasonal changes inherent to Picatinny's northern New Jersey location. Using the Precision Armament Laboratory (PAL) tower at Picatinny Arsenal, the sensors will autonomously collect the desired data around the clock at different ranges where surrogate 2S3 Self-Propelled Howitzer targets are positioned at different viewing perspectives at 549 and 1280m from the sensor location. The collected database will allow for: 1) Understand of signature variability under the different weather conditions; 2) Development of robust algorithms; 3) Development of new sensors; 4) Evaluation of hyperspectral and polarimetric technologies; and 5) Evaluation of fusing the different sensor modalities. In this paper, we will present the SPICE data collection objectives, the ongoing effort, the sensors that are currently deployed, and how this work will assist researches on the development and evaluation of sensors, algorithms, and fusion applications.

  13. ULTRAVIOLET RAMAN SPECTRAL SIGNATURE ACQUISITION: UV RAMAN SPECTRAL FINGERPRINTS.

    Energy Technology Data Exchange (ETDEWEB)

    SEDLACEK,III, A.J.FINFROCK,C.

    2002-09-01

    As a member of the science-support part of the ITT-lead LISA development program, BNL is tasked with the acquisition of UV Raman spectral fingerprints and associated scattering cross-sections for those chemicals-of-interest to the program's sponsor. In support of this role, the present report contains the first installment of UV Raman spectral fingerprint data on the initial subset of chemicals. Because of the unique nature associated with the acquisition of spectral fingerprints for use in spectral pattern matching algorithms (i.e., CLS, PLS, ANN) great care has been undertaken to maximize the signal-to-noise and to minimize unnecessary spectral subtractions, in an effort to provide the highest quality spectral fingerprints. This report is divided into 4 sections. The first is an Experimental section that outlines how the Raman spectra are performed. This is then followed by a section on Sample Handling. Following this, the spectral fingerprints are presented in the Results section where the data reduction process is outlined. Finally, a Photographs section is included.

  14. Trace maps of general substitutional sequences

    International Nuclear Information System (INIS)

    Kolar, M.; Nori, F.

    1990-01-01

    It is shown that for arbitrary n, there exists a trace map for any n-letter substitutional sequence. Trace maps are explicitly obtained for the well-known circle and Rudin-Shapiro sequences which can be defined by means of substitution rules on three and four letters, respectively. The properties of the two trace maps and their consequences for various spectral properties are briefly discussed

  15. Long-Term and Rapid Radio Variability of the Blazar 3C 454.3 in 2010-2017

    Science.gov (United States)

    Gorshkov, A. G.; Ipatov, A. V.; Ipatova, I. A.; Konnikova, V. K.; Mardyshkin, V. V.; Mingaliev, M. G.; Kharinov, M. A.

    2018-03-01

    The article presents the results of observations of the blazar 3C 454.3 (J2253+1608), obtained in 2010-2017 on the RATAN-600 radio telescope of the Special Astrophysical Observatory at 4.6, 8.2, 11.2, and 21.7 GHz and on the 32-m Zelenchuk and Badary radio telescopes of the Quasar VLBI Network of the Institute of Applied Astronomy at 4.84 and 8.57 GHz. Long-term variability of the radio emission is studied, as well as variability on time scales of several days and intraday variability (IDV). Two flares were observed in the long-term light curve, in 2010 and in 2015-2017. The flux density at 21.7 GHz increased by a factor of ten during these flares. The delay in the maximum of the first flare at 4.85 GHz relative to the maximum at 21.7 GHz was six months. The time scale for variability on the descending branch of the first flare at 21.7 GHz was τvar = 1.2 yrs, yielding an upper limit on the linear size of the emitting region of 0.4 pc, corresponding to an angular size of 0.06 mas. The brightness temperature during the flare exceeded the Compton limit, implying a Doppler factor δ = 3.5, consistent with the known presence of a relativistic jet oriented close to the line of sight. No significant variability on time scales from several days to several weeks was found in five sets of daily observations carried out over 120 days. IDV was detected at 8.57 GHz on the 32-m telescopes in 30 of 61 successful observing sessions, with the presence of IDV correlated with the maxima of flares. The characteristic time scale for the IDV was from two to ten hours. A number of IDV light curves show the presence of a time delay in the maxima in the light curves for simultaneous observations carried out on the Badary and Zelenchuk antennas, which are widely separated in longitude. This demonstrates that the IDV most like arises in the interstellar medium.

  16. Sparse spectral deconvolution algorithm for noncartesian MR spectroscopic imaging.

    Science.gov (United States)

    Bhave, Sampada; Eslami, Ramin; Jacob, Mathews

    2014-02-01

    To minimize line shape distortions and spectral leakage artifacts in MR spectroscopic imaging (MRSI). A spatially and spectrally regularized non-Cartesian MRSI algorithm that uses the line shape distortion priors, estimated from water reference data, to deconvolve the spectra is introduced. Sparse spectral regularization is used to minimize noise amplification associated with deconvolution. A spiral MRSI sequence that heavily oversamples the central k-space regions is used to acquire the MRSI data. The spatial regularization term uses the spatial supports of brain and extracranial fat regions to recover the metabolite spectra and nuisance signals at two different resolutions. Specifically, the nuisance signals are recovered at the maximum resolution to minimize spectral leakage, while the point spread functions of metabolites are controlled to obtain acceptable signal-to-noise ratio. The comparisons of the algorithm against Tikhonov regularized reconstructions demonstrates considerably reduced line-shape distortions and improved metabolite maps. The proposed sparsity constrained spectral deconvolution scheme is effective in minimizing the line-shape distortions. The dual resolution reconstruction scheme is capable of minimizing spectral leakage artifacts. Copyright © 2013 Wiley Periodicals, Inc.

  17. Programmable spectral design and the binary supergrating

    Science.gov (United States)

    Levner, Daniel

    Spectral operations such as wavelength selection, power level manipulation, and chromatic dispersion control are key to many processes in optical telecommunication, spectroscopy, and sensing. In their simplest forms, these functions can be performed using a number of successful devices such as the Fraunhofer ("diffraction") grating, Bragg grating, thin-film filter (TFF), and dispersion-compensating fiber (DCF). More complicated manipulations, however, often require either problematic cascades of many simple elements, the use of custom technologies that offer little adjustment, or the implementation of fully programmable devices, which allow for the desired spectral function to be synthesized ab initio. Here, I present the Binary Supergrating (BSG), a novel technology that permits the programmable and near-arbitrary control of optical amplitude and phase using a simple, robust and practical form. This guided-wave form consists of an aperiodic sequence of binary elements; the sequence, determined through the process of BSG synthesis, encodes an optical program that defines device functionality. The ability to derive optical programs that address broad spectral demands is central to the BSG's extensive capabilities. In consequence, I present a powerful approach to synthesis that exploits existing knowledge in the design of "analog" gratings. This approach is based on a two-step process, which first derives an analog diffractive structure using the best available methods and then transforms it into binary form. Accordingly, I discuss the notion of diffractive structure transformation and introduce the principle of key information. I identify such key information and illustrate its application in grating quantizers based on an atypical form of Delta-Sigma modulation. As a digital approach to spectral engineering, the BSG presents many of the same advantages offered by the digital approach to electronic signal processing (DSP) over its analog predecessors. As such, it

  18. Moebius sequence

    DEFF Research Database (Denmark)

    Pedersen, Line Kjeldgaard; Maimburg, Rikke Damkjær; Hertz, Jens Michael

    2017-01-01

    and photographical evaluation. Five patients maintained the diagnosis of MS according to the diagnostic criteria. RESULTS: All five patients had bilateral facial and abducens paralysis confirmed by ophthalmological examination. Three of five had normal brain MR imaging. Two had missing facial nerves and one had......BACKGROUND: Moebius Sequence (MS) is a rare disorder defined by bilateral congenital paralysis of the abducens and facial nerves in combination with various odontological, craniofacial, ophthalmological and orthopaedic conditions. The aetiology is still unknown; but both genetic (de novo mutations...

  19. Spectral Unmixing With Multiple Dictionaries

    Science.gov (United States)

    Cohen, Jeremy E.; Gillis, Nicolas

    2018-02-01

    Spectral unmixing aims at recovering the spectral signatures of materials, called endmembers, mixed in a hyperspectral or multispectral image, along with their abundances. A typical assumption is that the image contains one pure pixel per endmember, in which case spectral unmixing reduces to identifying these pixels. Many fully automated methods have been proposed in recent years, but little work has been done to allow users to select areas where pure pixels are present manually or using a segmentation algorithm. Additionally, in a non-blind approach, several spectral libraries may be available rather than a single one, with a fixed number (or an upper or lower bound) of endmembers to chose from each. In this paper, we propose a multiple-dictionary constrained low-rank matrix approximation model that address these two problems. We propose an algorithm to compute this model, dubbed M2PALS, and its performance is discussed on both synthetic and real hyperspectral images.

  20. Special topics in spectral distributions

    International Nuclear Information System (INIS)

    French, J.B.

    1980-01-01

    We discuss two problems which relate to the foundations of the subject, and a third about asymptotic properties of spectral distributions. We give also a brief list of topics which should be further explored

  1. Detection techniques for the H.E.S.S. II telescope, data modeling of gravitational lensing and emission of blazars in HE-VHE astronomy

    International Nuclear Information System (INIS)

    Barnacka, Anna

    2013-01-01

    This thesis presents the study of four aspects of high energy astronomy. The first part of my thesis is dedicated to an aspect of instrument development for imaging atmospheric Cherenkov telescopes, namely the Level 2 trigger system of the High Energy Stereoscopic System (H.E.S.S.). My work on the project focused on the algorithm development and the Monte Carlo simulations of the trigger system and overall instrument. The hardware implementation of the system is described and its expected performances are then evaluated. The H.E.S.S. array has been used to observe the blazar PKS 1510-089. The second part of my thesis deals with the data analysis and modeling of broad-band emission of this particular blazar. In part II of my thesis, I am presenting the analysis of the H.E.S.S. data: the light curve and spectrum of PKS 1510-089, together with the FERMI data and a collection of multi-wavelength data obtained with various instruments. I am presenting the model of PKS 1510-089 observations carried out during a flare recorded by H.E.S.S.. The model is based on a single zone internal shock scenario. The third part of my thesis deals with blazars observed by the FERMI-LAT, but from the point of view of other phenomena: a strong gravitational lensing. This part of my thesis shows the first evidence for gravitational lensing phenomena in high energy gamma-rays. This evidence comes from the observation of a gravitational lens system induced echo in the light curve of the distant blazar PKS 1830-211. Traditional methods for the estimation of time delays in gravitational lensing systems rely on the cross-correlation of the light curves from individual images. In my thesis, I used 300 MeV-30 GeV photons detected by the Fermi-LAT instrument. The FERMI-LAT instrument cannot separate the images of known lenses. The observed light curve is thus the superposition of individual image light curves. The FERMI-LAT instrument has the advantage of providing long, evenly spaced, time series

  2. Very Rapid High-amplitude Gamma-Ray Variability in Luminous Blazar PKS 1510-089 Studied with Fermi-LAT

    Energy Technology Data Exchange (ETDEWEB)

    Saito, S.; Stawarz, L.; Tanaka, Y.T.; Takahashi, T.; Madejski, G.; D' Ammando, F.

    2013-03-20

    Here we report on the detailed analysis of the γ-ray light curve of a luminous blazar PKS 1510-089 observed in the GeV range with the Large Area Telescope (LAT) onboard the Fermi satellite during the period 2011 September - December. By investigating the properties of the detected three major flares with the shortest possible time binning allowed by the photon statistics, we find a variety of temporal characteristics and variability patterns. This includes a clearly asymmetric profile (with a faster flux rise and a slower decay) of the flare resolved on sub-daily timescales, a superposition of many short uncorrelated flaring events forming the apparently coherent longer-duration outburst, and a huge single isolated outburst unresolved down to the timescale of three-hours. In the latter case we estimate the corresponding γ-ray flux doubling timescale to be below one hour, which is extreme and never previously reported for any active galaxy

  3. Spectral dimensionality reduction for HMMs

    OpenAIRE

    Foster, Dean P.; Rodu, Jordan; Ungar, Lyle H.

    2012-01-01

    Hidden Markov Models (HMMs) can be accurately approximated using co-occurrence frequencies of pairs and triples of observations by using a fast spectral method in contrast to the usual slow methods like EM or Gibbs sampling. We provide a new spectral method which significantly reduces the number of model parameters that need to be estimated, and generates a sample complexity that does not depend on the size of the observation vocabulary. We present an elementary proof giving bounds on the rel...

  4. Compressive spectroscopy by spectral modulation

    Science.gov (United States)

    Oiknine, Yaniv; August, Isaac; Stern, Adrian

    2017-05-01

    We review two compressive spectroscopy techniques based on modulation in the spectral domain that we have recently proposed. Both techniques achieve a compression ratio of approximately 10:1, however each with a different sensing mechanism. The first technique uses a liquid crystal cell as a tunable filter to modulate the spectral signal, and the second technique uses a Fabry-Perot etalon as a resonator. We overview the specific properties of each of the techniques.

  5. Spectral unmixing: estimating partial abundances

    CSIR Research Space (South Africa)

    Debba, Pravesh

    2009-01-01

    Full Text Available the ingredients for this chocolate cake? Debba (CSIR) Spectral Unmixing LQM 2009 3 / 22 Background and Research Question Ingredients Quantity unsweetened chocolate unsweetened cocoa powder boiling water flour baking powder baking soda salt unsalted... butter white sugar eggs pure vanilla extract milk Table: Chocolate cake ingredients Debba (CSIR) Spectral Unmixing LQM 2009 4 / 22 Background and Research Question Ingredients Quantity unsweetened chocolate 120 grams unsweetened cocoa powder 28...

  6. Change Detection Analysis With Spectral Thermal Imagery

    National Research Council Canada - National Science Library

    Behrens, Richard

    1998-01-01

    ... (LWIR) region. This study used analysis techniques of differencing, histograms, and principal components analysis to detect spectral changes and investigate the utility of spectral change detection...

  7. The Spectral Web of stationary plasma equilibria. II. Internal modes

    Science.gov (United States)

    Goedbloed, J. P.

    2018-03-01

    The new method of the Spectral Web to calculate the spectrum of waves and instabilities of plasma equilibria with sizeable flows, developed in the preceding Paper I [Goedbloed, Phys. Plasmas 25, 032109 (2018)], is applied to a collection of classical magnetohydrodynamic instabilities operating in cylindrical plasmas with shear flow or rotation. After a review of the basic concepts of the complementary energy giving the solution path and the conjugate path, which together constitute the Spectral Web, the cylindrical model is presented and the spectral equations are derived. The first example concerns the internal kink instabilities of a cylindrical force-free magnetic field of constant α subjected to a parabolic shear flow profile. The old stability diagram and the associated growth rate calculations for static equilibria are replaced by a new intricate stability diagram and associated complex growth rates for the stationary model. The power of the Spectral Web method is demonstrated by showing that the two associated paths in the complex ω-plane nearly automatically guide to the new class of global Alfvén instabilities of the force-free configuration that would have been very hard to predict by other methods. The second example concerns the Rayleigh-Taylor instability of a rotating theta-pinch. The old literature is revisited and shown to suffer from inconsistencies that are remedied. The most global n = 1 instability and a cluster sequence of more local but much more unstable n =2 ,3 ,…∞ modes are located on separate solution paths in the hydrodynamic (HD) version of the instability, whereas they merge in the MHD version. The Spectral Web offers visual demonstration of the central position the HD flow continuum and of the MHD Alfvén and slow magneto-sonic continua in the respective spectra by connecting the discrete modes in the complex plane by physically meaningful curves towards the continua. The third example concerns the magneto-rotational instability

  8. Spectral filtering for plant production

    Energy Technology Data Exchange (ETDEWEB)

    Young, R.E.; McMahon, M.J.; Rajapakse, N.C.; Becoteau, D.R.

    1994-12-31

    Research to date suggests that spectral filtering can be an effective alternative to chemical growth regulators for altering plant development. If properly implemented, it can be nonchemical and environmentally friendly. The aqueous CuSO{sub 4}, and CuCl{sub 2} solutions in channelled plastic panels have been shown to be effective filters, but they can be highly toxic if the solutions contact plants. Some studies suggest that spectral filtration limited to short EOD intervals can also alter plant development. Future research should be directed toward confirmation of the influence of spectral filters and exposure times on a broader range of plant species and cultivars. Efforts should also be made to identify non-noxious alternatives to aqueous copper solutions and/or to incorporate these chemicals permanently into plastic films and panels that can be used in greenhouse construction. It would also be informative to study the impacts of spectral filters on insect and microbal populations in plant growth facilities. The economic impacts of spectral filtering techniques should be assessed for each delivery methodology.

  9. Solar Spectral Irradiance and Climate

    Science.gov (United States)

    Pilewskie, P.; Woods, T.; Cahalan, R.

    2012-01-01

    Spectrally resolved solar irradiance is recognized as being increasingly important to improving our understanding of the manner in which the Sun influences climate. There is strong empirical evidence linking total solar irradiance to surface temperature trends - even though the Sun has likely made only a small contribution to the last half-century's global temperature anomaly - but the amplitudes cannot be explained by direct solar heating alone. The wavelength and height dependence of solar radiation deposition, for example, ozone absorption in the stratosphere, absorption in the ocean mixed layer, and water vapor absorption in the lower troposphere, contribute to the "top-down" and "bottom-up" mechanisms that have been proposed as possible amplifiers of the solar signal. New observations and models of solar spectral irradiance are needed to study these processes and to quantify their impacts on climate. Some of the most recent observations of solar spectral variability from the mid-ultraviolet to the near-infrared have revealed some unexpected behavior that was not anticipated prior to their measurement, based on an understanding from model reconstructions. The atmospheric response to the observed spectral variability, as quantified in climate model simulations, have revealed similarly surprising and in some cases, conflicting results. This talk will provide an overview on the state of our understanding of the spectrally resolved solar irradiance, its variability over many time scales, potential climate impacts, and finally, a discussion on what is required for improving our understanding of Sun-climate connections, including a look forward to future observations.

  10. Spectral element simulation of ultrafiltration

    DEFF Research Database (Denmark)

    Hansen, M.; Barker, Vincent A.; Hassager, Ole

    1998-01-01

    A spectral element method for simulating stationary 2-D ultrafiltration is presented. The mathematical model is comprised of the Navier-Stokes equations for the velocity field of the fluid and a transport equation for the concentration of the solute. In addition to the presence of the velocity...... vector in the transport equation, the system is coupled by the dependency of the fluid viscosity on the solute concentration and by a concentration-dependent boundary condition for the Navier-Stokes equations at the membrane surface. The spectral element discretization yields a nonlinear algebraic system....... The performance of the spectral element code when applied to several ultrafiltration problems is reported. (C) 1998 Elsevier Science Ltd. All rights reserved....

  11. Spectrally Compatible Iterative Water Filling

    Science.gov (United States)

    Verlinden, Jan; Bogaert, Etienne Vanden; Bostoen, Tom; Zanier, Francesca; Luise, Marco; Cendrillon, Raphael; Moonen, Marc

    2006-12-01

    Until now static spectrum management has ensured that DSL lines in the same cable are spectrally compatible under worst-case crosstalk conditions. Recently dynamic spectrum management (DSM) has been proposed aiming at an increased capacity utilization by adaptation of the transmit spectra of DSL lines to the actual crosstalk interference. In this paper, a new DSM method for downstream ADSL is derived from the well-known iterative water-filling (IWF) algorithm. The amount of boosting of this new DSM method is limited, such that it is spectrally compatible with ADSL. Hence it is referred to as spectrally compatible iterative water filling (SC-IWF). This paper focuses on the performance gains of SC-IWF. This method is an autonomous DSM method (DSM level 1) and it will be investigated together with two other DSM level-1 algorithms, under various noise conditions, namely, iterative water-filling algorithm, and flat power back-off (flat PBO).

  12. Spectrally Compatible Iterative Water Filling

    Directory of Open Access Journals (Sweden)

    Cendrillon Raphael

    2006-01-01

    Full Text Available Until now static spectrum management has ensured that DSL lines in the same cable are spectrally compatible under worst-case crosstalk conditions. Recently dynamic spectrum management (DSM has been proposed aiming at an increased capacity utilization by adaptation of the transmit spectra of DSL lines to the actual crosstalk interference. In this paper, a new DSM method for downstream ADSL is derived from the well-known iterative water-filling (IWF algorithm. The amount of boosting of this new DSM method is limited, such that it is spectrally compatible with ADSL. Hence it is referred to as spectrally compatible iterative water filling (SC-IWF. This paper focuses on the performance gains of SC-IWF. This method is an autonomous DSM method (DSM level 1 and it will be investigated together with two other DSM level-1 algorithms, under various noise conditions, namely, iterative water-filling algorithm, and flat power back-off (flat PBO.

  13. Spectral scheme for spacetime physics

    International Nuclear Information System (INIS)

    Seriu, Masafumi

    2002-01-01

    Based on the spectral representation of spatial geometry, we construct an analysis scheme for spacetime physics and cosmology, which enables us to compare two or more universes with each other. In this scheme the spectral distance plays a central role, which is the measure of closeness between two geometries defined in terms of the spectra. We apply this scheme for analyzing the averaging problem in cosmology; we explicitly investigate the time evolution of the spectra, distance between two nearby spatial geometries, simulating the relation between the real Universe and its model. We then formulate the criteria for a model to be a suitable one

  14. Spectral ellipsometry of nanodiamond composite

    International Nuclear Information System (INIS)

    Yastrebov, S.G.; Ivanov-Omskij, V.I.; Gordeev, S.K.; Garriga, M.; Alonso, I.A.

    2006-01-01

    Methods of spectral ellipsometry were applied for analysis of optical properties of nanodiamond based composite in spectral region 1.4-5 eV. The nanocomposite was synthesized by molding of ultradispersed nanodiamond powder in the course of heterogeneous chemical reaction of decomposition of methane, forming pyrocarbon interconnecting nanodiamond grains. The energy of σ + π plasmon of pyrocarbon component of nanodiamond composite was restored which proves to be ∼ 24 eV; using this value, an estimation was done of pyrocarbon matrix density, which occurs to be 2 g/cm 3 [ru

  15. Spectral Variability in Radio-Loud Quasars Minfeng Gu

    Indian Academy of Sciences (India)

    with a large viewing angle, and therefore, the beaming effect is not severe. Although a bluer-when-brighter trend is commonly observed in blazars (e.g., Fan ... of the Radio Sky at Twenty cm (FIRST) 1.4-GHz radio catalogue (Becker et al. 1995), the green bank 6-cm (GB6) survey at 4.85 GHz radio catalogue (Gregory et al.

  16. SPECTRAL DEPENDENT ELECTRICAL CHARACTERISTICS OF ...

    African Journals Online (AJOL)

    ABSTRACT: The illuminated current-voltage characteristics of thin film a-Si:H. p-i-n solar cells were measured for the visible and near infrared spectral regions. The fill factor, the conversion efficiency, the open circuit Voltage and the short circuit current were compared to the parameters of crystalline silicon pit-junction.

  17. Speech recognition from spectral dynamics

    Indian Academy of Sciences (India)

    Abstract. Information is carried in changes of a signal. The paper starts with revis- iting Dudley's concept of the carrier nature of speech. It points to its close connection to modulation spectra of speech and argues against short-term spectral envelopes as dominant carriers of the linguistic information in speech. The history of ...

  18. Speech recognition from spectral dynamics

    Indian Academy of Sciences (India)

    2016-08-26

    Aug 26, 2016 ... Some of the history of gradual infusion of the modulation spectrum concept into Automatic recognition of speech (ASR) comes next, pointing to the relationship of modulation spectrum processing to wellaccepted ASR techniques such as dynamic speech features or RelAtive SpecTrAl (RASTA) filtering. Next ...

  19. Spectral problems for operator matrices

    NARCIS (Netherlands)

    Bátkai, A.; Binding, P.; Dijksma, A.; Hryniv, R.; Langer, H.

    2005-01-01

    We study spectral properties of 2 × 2 block operator matrices whose entries are unbounded operators between Banach spaces and with domains consisting of vectors satisfying certain relations between their components. We investigate closability in the product space, essential spectra and generation of

  20. Spectral Methods for Numerical Relativity

    Directory of Open Access Journals (Sweden)

    Grandclément Philippe

    2009-01-01

    Full Text Available Equations arising in general relativity are usually too complicated to be solved analytically and one must rely on numerical methods to solve sets of coupled partial differential equations. Among the possible choices, this paper focuses on a class called spectral methods in which, typically, the various functions are expanded in sets of orthogonal polynomials or functions. First, a theoretical introduction of spectral expansion is given with a particular emphasis on the fast convergence of the spectral approximation. We then present different approaches to solving partial differential equations, first limiting ourselves to the one-dimensional case, with one or more domains. Generalization to more dimensions is then discussed. In particular, the case of time evolutions is carefully studied and the stability of such evolutions investigated. We then present results obtained by various groups in the field of general relativity by means of spectral methods. Work, which does not involve explicit time-evolutions, is discussed, going from rapidly-rotating strange stars to the computation of black-hole–binary initial data. Finally, the evolution of various systems of astrophysical interest are presented, from supernovae core collapse to black-hole–binary mergers.

  1. Functional Analysis-Spectral Theoryl

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 6; Issue 4. Functional Analysis - Spectral Theory1. Cherian Varughese. Book Review Volume 6 Issue 4 April 2001 pp 91-92 ... Author Affiliations. Cherian Varughese1. Indian Statistical Institute, 8th Mile, Mysore Road, Bangalore 560 059, India.

  2. Spectral Diagonal Ensemble Kalman Filters

    Czech Academy of Sciences Publication Activity Database

    Kasanický, Ivan; Mandel, Jan; Vejmelka, Martin

    2015-01-01

    Roč. 22, č. 4 (2015), s. 485-497 ISSN 1023-5809 R&D Projects: GA ČR GA13-34856S Grant - others:NSF(US) DMS -1216481 Institutional support: RVO:67985807 Keywords : data assimilation * ensemble Kalman filter * spectral representation Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.321, year: 2015

  3. Speech recognition from spectral dynamics

    Indian Academy of Sciences (India)

    Some of the history of gradual infusion of the modulation spectrum concept into Automatic recognition of speech (ASR) comes next, pointing to the relationship of modulation spectrum processing to wellaccepted ASR techniques such as dynamic speech features or RelAtive SpecTrAl (RASTA) filtering. Next, the frequency ...

  4. Speech recognition from spectral dynamics

    Indian Academy of Sciences (India)

    automatic recognition of speech (ASR). Instead, likely for historical reasons, envelopes of power spectrum were adopted as main carrier of linguistic information in ASR. However, the relationships between phonetic values of sounds and their short-term spectral envelopes are not straightforward. Consequently, this asks for ...

  5. Spectral representation of Gaussian semimartingales

    DEFF Research Database (Denmark)

    Basse-O'Connor, Andreas

    2009-01-01

    The aim of the present paper is to characterize the spectral representation of Gaussian semimartingales. That is, we provide necessary and sufficient conditions on the kernel K for X t =∫ K t (s) dN s to be a semimartingale. Here, N denotes an independently scattered Gaussian random measure...

  6. Assessing FRET using Spectral Techniques

    Science.gov (United States)

    Leavesley, Silas J.; Britain, Andrea L.; Cichon, Lauren K.; Nikolaev, Viacheslav O.; Rich, Thomas C.

    2015-01-01

    Förster resonance energy transfer (FRET) techniques have proven invaluable for probing the complex nature of protein–protein interactions, protein folding, and intracellular signaling events. These techniques have traditionally been implemented with the use of one or more fluorescence band-pass filters, either as fluorescence microscopy filter cubes, or as dichroic mirrors and band-pass filters in flow cytometry. In addition, new approaches for measuring FRET, such as fluorescence lifetime and acceptor photobleaching, have been developed. Hyperspectral techniques for imaging and flow cytometry have also shown to be promising for performing FRET measurements. In this study, we have compared traditional (filter-based) FRET approaches to three spectral-based approaches: the ratio of acceptor-to-donor peak emission, linear spectral unmixing, and linear spectral unmixing with a correction for direct acceptor excitation. All methods are estimates of FRET efficiency, except for one-filter set and three-filter set FRET indices, which are included for consistency with prior literature. In the first part of this study, spectrofluorimetric data were collected from a CFP–Epac–YFP FRET probe that has been used for intracellular cAMP measurements. All comparisons were performed using the same spectrofluorimetric datasets as input data, to provide a relevant comparison. Linear spectral unmixing resulted in measurements with the lowest coefficient of variation (0.10) as well as accurate fits using the Hill equation. FRET efficiency methods produced coefficients of variation of less than 0.20, while FRET indices produced coefficients of variation greater than 8.00. These results demonstrate that spectral FRET measurements provide improved response over standard, filter-based measurements. Using spectral approaches, single-cell measurements were conducted through hyperspectral confocal microscopy, linear unmixing, and cell segmentation with quantitative image analysis

  7. Investigation of spectral statistics of nuclear systems by maximum likelihood estimation method

    International Nuclear Information System (INIS)

    Jafarizadeh, M.A.; Fouladi, N.; Sabri, H.; Rashidian Maleki, B.

    2012-01-01

    In this paper, maximum likelihood estimation technique is employed to consider the spectral statistics of nuclear systems in the nearest neighbor spacing distribution framework. With using the available empirical data, the spectral statistics of different sequences are analyzed. The ML-based estimated values propose more regular dynamics and also minimum uncertainties (variations very close to CRLB) in compare to other estimation methods. Also, the efficiencies of considered distribution functions are examined where suggest the least CRLB for Brody distribution.

  8. Assessment of modern spectral analysis methods to improve wavenumber resolution of F-K spectra

    International Nuclear Information System (INIS)

    Shirley, T.E.; Laster, S.J.; Meek, R.A.

    1987-01-01

    The improvement in wavenumber spectra obtained by using high resolution spectral estimators is examined. Three modern spectral estimators were tested, namely the Autoregressive/Maximum Entropy (AR/ME) method, the Extended Prony method, and an eigenstructure method. They were combined with the conventional Fourier method by first transforming each trace with a Fast Fourier Transform (FFT). A high resolution spectral estimator was applied to the resulting complex spatial sequence for each frequency. The collection of wavenumber spectra thus computed comprises a hybrid f-k spectrum with high wavenumber resolution and less spectral ringing. Synthetic and real data records containing 25 traces were analyzed by using the hybrid f-k method. The results show an FFT-AR/ME f-k spectrum has noticeably better wavenumber resolution and more spectral dynamic range than conventional spectra when the number of channels is small. The observed improvement suggests the hybrid technique is potentially valuable in seismic data analysis

  9. Simulative Investigation on Spectral Efficiency of Unipolar Codes based OCDMA System using Importance Sampling Technique

    Science.gov (United States)

    Farhat, A.; Menif, M.; Rezig, H.

    2013-09-01

    This paper analyses the spectral efficiency of Optical Code Division Multiple Access (OCDMA) system using Importance Sampling (IS) technique. We consider three configurations of OCDMA system namely Direct Sequence (DS), Spectral Amplitude Coding (SAC) and Fast Frequency Hopping (FFH) that exploits the Fiber Bragg Gratings (FBG) based encoder/decoder. We evaluate the spectral efficiency of the considered system by taking into consideration the effect of different families of unipolar codes for both coherent and incoherent sources. The results show that the spectral efficiency of OCDMA system with coherent source is higher than the incoherent case. We demonstrate also that DS-OCDMA outperforms both others in terms of spectral efficiency in all conditions.

  10. The Ultraviolet Spectral Morphology of a Sample of B Supergiants in the Small Magellanic Cloud

    Science.gov (United States)

    McNeil, R. C.; Borchers, A. L.; Sonneborn, G.; Fahey, R. P.

    1995-05-01

    A study of the ultraviolet spectra of a sample of B supergiants in the Small Magellanic Cloud is being undertaken as a means of addressing some questions about the nature and evolution of massive stars. All spectra are new or archival low-dispersion SWP spectra (1200International Ultraviolet Explorer. As a first step in this study, the ultraviolet spectral morphology of approximately 50 program stars is being examined for consistency with their published spectral classifications. Analysis includes a tabulation of ultraviolet spectral features, evaluation of their variation with spectral type and luminosity class, and comparison with IUE spectral sequences of standard stars. The data analysis was performed at the IUE Data Analysis Center at Goddard Space Flight Center. Partial support of this work by NASA and Northern Kentucky University through the Joint Ventures (JOVE) program, and support of the Laboratory for Astronomy and Solar Physics at GSFC, is gratefully acknowledged.

  11. Spectral Tensor-Train Decomposition

    DEFF Research Database (Denmark)

    Bigoni, Daniele; Engsig-Karup, Allan Peter; Marzouk, Youssef M.

    2016-01-01

    discretizations of the target function. We assess the performance of the method on a range of numerical examples: a modified set of Genz functions with dimension up to 100, and functions with mixed Fourier modes or with local features. We observe significant improvements in performance over an anisotropic......The accurate approximation of high-dimensional functions is an essential task in uncertainty quantification and many other fields. We propose a new function approximation scheme based on a spectral extension of the tensor-train (TT) decomposition. We first define a functional version of the TT.......e., the “cores”) comprising the functional TT decomposition. This result motivates an approximation scheme employing polynomial approximations of the cores. For functions with appropriate regularity, the resulting spectral tensor-train decomposition combines the favorable dimension-scaling of the TT...

  12. Spectral computations for bounded operators

    CERN Document Server

    Ahues, Mario; Limaye, Balmohan

    2001-01-01

    Exact eigenvalues, eigenvectors, and principal vectors of operators with infinite dimensional ranges can rarely be found. Therefore, one must approximate such operators by finite rank operators, then solve the original eigenvalue problem approximately. Serving as both an outstanding text for graduate students and as a source of current results for research scientists, Spectral Computations for Bounded Operators addresses the issue of solving eigenvalue problems for operators on infinite dimensional spaces. From a review of classical spectral theory through concrete approximation techniques to finite dimensional situations that can be implemented on a computer, this volume illustrates the marriage of pure and applied mathematics. It contains a variety of recent developments, including a new type of approximation that encompasses a variety of approximation methods but is simple to verify in practice. It also suggests a new stopping criterion for the QR Method and outlines advances in both the iterative refineme...

  13. Biomarkers and Biological Spectral Imaging

    Science.gov (United States)

    2001-01-23

    karyotyping (SKY) in hematological neoplasia [4259-13] B. S. Preiss, R. K. Pedersen, G. B. Kerndrup, Odense Univ. Hospital (Denmark) 60 Structure of...astronomy and airborne monitoring to forensic and biomedical sciences or industrial qualit\\ and process monitoring. There is growing need for a sensitive...SPIE Vol. 4259 55 Spectral Karyotyping (SKY) in Hematologic Neoplasia. Birgitte S. Preiss*a, Rikke K. Pedersena, Gitte B. Kerndrupa aInstitute of

  14. Chebyshev and Fourier spectral methods

    CERN Document Server

    Boyd, John P

    2001-01-01

    Completely revised text focuses on use of spectral methods to solve boundary value, eigenvalue, and time-dependent problems, but also covers Hermite, Laguerre, rational Chebyshev, sinc, and spherical harmonic functions, as well as cardinal functions, linear eigenvalue problems, matrix-solving methods, coordinate transformations, methods for unbounded intervals, spherical and cylindrical geometry, and much more. 7 Appendices. Glossary. Bibliography. Index. Over 160 text figures.

  15. Shotgun protein sequencing.

    Energy Technology Data Exchange (ETDEWEB)

    Faulon, Jean-Loup Michel; Heffelfinger, Grant S.

    2009-06-01

    A novel experimental and computational technique based on multiple enzymatic digestion of a protein or protein mixture that reconstructs protein sequences from sequences of overlapping peptides is described in this SAND report. This approach, analogous to shotgun sequencing of DNA, is to be used to sequence alternative spliced proteins, to identify post-translational modifications, and to sequence genetically engineered proteins.

  16. Abundance estimation of spectrally similar minerals

    CSIR Research Space (South Africa)

    Debba, Pravesh

    2009-07-01

    Full Text Available This paper evaluates a spectral unmixing method for estimating the partial abundance of spectrally similar minerals in complex mixtures. The method requires formulation of a linear function of individual spectra of individual minerals. The first...

  17. The sequence of sequencers: The history of sequencing DNA

    Science.gov (United States)

    Heather, James M.; Chain, Benjamin

    2016-01-01

    Determining the order of nucleic acid residues in biological samples is an integral component of a wide variety of research applications. Over the last fifty years large numbers of researchers have applied themselves to the production of techniques and technologies to facilitate this feat, sequencing DNA and RNA molecules. This time-scale has witnessed tremendous changes, moving from sequencing short oligonucleotides to millions of bases, from struggling towards the deduction of the coding sequence of a single gene to rapid and widely available whole genome sequencing. This article traverses those years, iterating through the different generations of sequencing technology, highlighting some of the key discoveries, researchers, and sequences along the way. PMID:26554401

  18. Calibration with near-continuous spectral measurements

    DEFF Research Database (Denmark)

    Nielsen, Henrik Aalborg; Rasmussen, Michael; Madsen, Henrik

    2001-01-01

    In chemometrics traditional calibration in case of spectral measurements express a quantity of interest (e.g. a concentration) as a linear combination of the spectral measurements at a number of wavelengths. Often the spectral measurements are performed at a large number of wavelengths and in thi...... by an example in which the octane number of gasoline is related to near infrared spectral measurements. The performance is found to be much better that for the traditional calibration methods....

  19. First Nustar Observations of the Bl Lac-Type Blazar Pks 2155-304: Constraints on the Jet Content and Distribution of Radiating Particles

    DEFF Research Database (Denmark)

    Madejski, G. M.; Nalewajko, K.; Madsen, K. K.

    2016-01-01

    , covering the energy range 0.5–60 keV, is best described by a model consisting of a log-parabola component with curvature β = 0.3 -0.1+0.2 and a (local) photon index 3.04 ± 0.15 at photon energy of 2 keV, and a hard power-law tail with photon index 2.2 ± 0.4. The hard X-ray tail can be smoothly joined......We report the first hard X-ray observations with NuSTAR of the BL Lac-type blazar PKS 2155-304, augmented with soft X-ray data from XMM-Newton and γ-ray data from the Fermi Large Area Telescope, obtained in 2013 April when the source was in a very low flux state. A joint NuSTAR and XMM spectrum...... to the quasi-simultaneous γ-ray spectrum by a synchrotron self-Compton component produced by an electron distribution with index p = 2.2. Assuming that the power-law electron distribution extends down to γ min = 1 and that there is one proton per electron, an unrealistically high total jet power of Lp ~ 10...

  20. USGS Spectral Library Version 7

    Science.gov (United States)

    Kokaly, Raymond F.; Clark, Roger N.; Swayze, Gregg A.; Livo, K. Eric; Hoefen, Todd M.; Pearson, Neil C.; Wise, Richard A.; Benzel, William M.; Lowers, Heather A.; Driscoll, Rhonda L.; Klein, Anna J.

    2017-04-10

    We have assembled a library of spectra measured with laboratory, field, and airborne spectrometers. The instruments used cover wavelengths from the ultraviolet to the far infrared (0.2 to 200 microns [μm]). Laboratory samples of specific minerals, plants, chemical compounds, and manmade materials were measured. In many cases, samples were purified, so that unique spectral features of a material can be related to its chemical structure. These spectro-chemical links are important for interpreting remotely sensed data collected in the field or from an aircraft or spacecraft. This library also contains physically constructed as well as mathematically computed mixtures. Four different spectrometer types were used to measure spectra in the library: (1) Beckman™ 5270 covering the spectral range 0.2 to 3 µm, (2) standard, high resolution (hi-res), and high-resolution Next Generation (hi-resNG) models of Analytical Spectral Devices (ASD) field portable spectrometers covering the range from 0.35 to 2.5 µm, (3) Nicolet™ Fourier Transform Infra-Red (FTIR) interferometer spectrometers covering the range from about 1.12 to 216 µm, and (4) the NASA Airborne Visible/Infra-Red Imaging Spectrometer AVIRIS, covering the range 0.37 to 2.5 µm. Measurements of rocks, soils, and natural mixtures of minerals were made in laboratory and field settings. Spectra of plant components and vegetation plots, comprising many plant types and species with varying backgrounds, are also in this library. Measurements by airborne spectrometers are included for forested vegetation plots, in which the trees are too tall for measurement by a field spectrometer. This report describes the instruments used, the organization of materials into chapters, metadata descriptions of spectra and samples, and possible artifacts in the spectral measurements. To facilitate greater application of the spectra, the library has also been convolved to selected spectrometer and imaging spectrometers sampling and

  1. Calibrating spectral images using penalized likelihood

    NARCIS (Netherlands)

    Heijden, van der G.W.A.M.; Glasbey, C.

    2003-01-01

    A new method is presented for automatic correction of distortions and for spectral calibration (which band corresponds to which wavelength) of spectral images recorded by means of a spectrograph. The method consists of recording a bar-like pattern with an illumination source with spectral bands

  2. Spectral properties of generalized eigenparameter dependent ...

    African Journals Online (AJOL)

    Jost function, spectrum, the spectral singularities, and the properties of the principal vectors corresponding to the spectral singularities of L, if. ∞Σn=1 n(∣1 - an∣ + ∣bnl) < ∞. Mathematics Subject Classication (2010): 34L05, 34L40, 39A70, 47A10, 47A75. Key words: Discrete equations, eigenparameter, spectral analysis, ...

  3. Spectral Lag Evolution among -Ray Burst Pulses

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... We analyse the spectral lag evolution of -ray burst (GRB) pulses with observations by CGRO/BATSE. No universal spectral lag evolution feature and pulse luminosity-lag relation within a GRB is observed.Our results suggest that the spectral lag would be due to radiation physics and dynamics of a given ...

  4. Sequence Read Archive (SRA)

    Data.gov (United States)

    U.S. Department of Health & Human Services — The Sequence Read Archive (SRA) stores raw sequencing data from the next generation of sequencing platforms including Roche 454 GS System®, Illumina Genome...

  5. Spectral Properties of Chaotic Signals Generated by the Bernoulli Map

    Directory of Open Access Journals (Sweden)

    Rafael A. da Costa

    2014-11-01

    Full Text Available In the last decades, the use of chaotic signals as broadband carriers has been considered in Telecommunications. Despite the relevance of the frequency domain analysis in this field, there are few studies that are concerned with spectral properties of chaotic signals. Bearing this in mind, this paper aims the characterization of the power spectral density (PSD of chaotic orbits generated by Bernoulli maps. We obtain analytic expressions for autocorrelation sequence, PSD and essential bandwidth for chaotic orbits generated by this map as function of the family parameter and Lyapunov exponent. Moreover, we verify that analytical expressions match numerical results. We conclude that the power of the generated orbits is concentrated in low frequencies for all parameters values. Besides, it is possible to obtain chaotic narrowband signals.

  6. Stochastically excited oscillations on the upper main sequence

    DEFF Research Database (Denmark)

    Antoci, Victoria

    2013-01-01

    Convective envelopes in stars on the main sequence are usually connected only with stars of spectral types F5 or later. However, observations as well as theory indicate that the convective outer layers in earlier stars, despite being shallow, are still effective and turbulent enough to stochastic......Convective envelopes in stars on the main sequence are usually connected only with stars of spectral types F5 or later. However, observations as well as theory indicate that the convective outer layers in earlier stars, despite being shallow, are still effective and turbulent enough...... Pulsating B and Be stars, all in the context of solar-like oscillations....

  7. Spectral multitude and spectral dynamics reflect changing conjugation length in single molecules of oligophenylenevinylenes

    KAUST Repository

    Kobayashi, Hiroyuki

    2012-01-01

    Single-molecule study of phenylenevinylene oligomers revealed distinct spectral forms due to different conjugation lengths which are determined by torsional defects. Large spectral jumps between different spectral forms were ascribed to torsional flips of a single phenylene ring. These spectral changes reflect the dynamic nature of electron delocalization in oligophenylenevinylenes and enable estimation of the phenylene torsional barriers. © 2012 The Owner Societies.

  8. [Spectral analysis in nanometer material science].

    Science.gov (United States)

    Chen, Wei; Sun, Shi-gang

    2002-06-01

    Spectral analysis is an important means in studies of nanometer scale systems, and is essential for deep understanding the structure and properties of nanometer materials. This paper reviews the recent progresses made in studies of nanometer materials using spectral analysis methods such as UV-Visible spectroscopy, FTIR spectroscopy, Raman spectroscopy, Mössbauer spectroscopy, positron annihilation and photoacoustic spectroscopy. The principle, characteristics and applications of most frequently employed spectral methods are introduced briefly and illustrated with typical examples. Future perspectives of spectral analysis in nanometer field are discussed. New directions of establishing spectral analysis methods at nanometer scale resolution and developing new spectroscopy technology in nanometer material studies are also emphasized.

  9. MULTI-WAVELENGTH OBSERVATIONS OF THE FLARING GAMMA-RAY BLAZAR 3C 66A IN 2008 OCTOBER

    International Nuclear Information System (INIS)

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Borgland, A. W.; Bouvier, A.; Buehler, R.; Baldini, L.; Bellazzini, R.; Bregeon, J.; Brez, A.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Buson, S.; Bonamente, E.; Brigida, M.; Bruel, P.

    2011-01-01

    The BL Lacertae object 3C 66A was detected in a flaring state by the Fermi Large Area Telescope (LAT) and VERITAS in 2008 October. In addition to these gamma-ray observations, F-GAMMA, GASP-WEBT, PAIRITEL, MDM, ATOM, Swift, and Chandra provided radio to X-ray coverage. The available light curves show variability and, in particular, correlated flares are observed in the optical and Fermi-LAT gamma-ray band. The resulting spectral energy distribution can be well fitted using standard leptonic models with and without an external radiation field for inverse Compton scattering. It is found, however, that only the model with an external radiation field can accommodate the intra-night variability observed at optical wavelengths.

  10. Planck 2013 results. IX. HFI spectral response

    CERN Document Server

    Ade, P A R; Armitage-Caplan, C; Arnaud, M; Ashdown, M; Atrio-Barandela, F; Aumont, J; Baccigalupi, C; Banday, A J; Barreiro, R B; Battaner, E; Benabed, K; Benoît, A; Benoit-Lévy, A; Bernard, J -P; Bersanelli, M; Bielewicz, P; Bobin, J; Bock, J J; Bond, J R; Borrill, J; Bouchet, F R; Boulanger, F; Bridges, M; Bucher, M; Burigana, C; Cardoso, J -F; Catalano, A; Challinor, A; Chamballu, A; Chary, R -R; Chen, X; Chiang, L -Y; Chiang, H C; Christensen, P R; Church, S; Clements, D L; Colombi, S; Colombo, L P L; Combet, C; Comis, B; Couchot, F; Coulais, A; Crill, B P; Curto, A; Cuttaia, F; Danese, L; Davies, R D; de Bernardis, P; de Rosa, A; de Zotti, G; Delabrouille, J; Delouis, J -M; Désert, F -X; Dickinson, C; Diego, J M; Dole, H; Donzelli, S; Doré, O; Douspis, M; Dupac, X; Efstathiou, G; Enßlin, T A; Eriksen, H K; Falgarone, E; Finelli, F; Forni, O; Frailis, M; Franceschi, E; Galeotta, S; Ganga, K; Giard, M; Giraud-Héraud, Y; González-Nuevo, J; Górski, K M; Gratton, S; Gregorio, A; Gruppuso, A; Hansen, F K; Hanson, D; Harrison, D; Henrot-Versillé, S; Hernández-Monteagudo, C; Herranz, D; Hildebrandt, S R; Hivon, E; Hobson, M; Holmes, W A; Hornstrup, A; Hovest, W; Huffenberger, K M; Hurier, G; Jaffe, T R; Jaffe, A H; Jones, W C; Juvela, M; Keihänen, E; Keskitalo, R; Kisner, T S; Kneissl, R; Knoche, J; Knox, L; Kunz, M; Kurki-Suonio, H; Lagache, G; Lamarre, J -M; Lasenby, A; Laureijs, R J; Lawrence, C R; Leahy, J P; Leonardi, R; Leroy, C; Lesgourgues, J; Liguori, M; Lilje, P B; Linden-Vørnle, M; López-Caniego, M; Lubin, P M; Macías-Pérez, J F; Maffei, B; Mandolesi, N; Maris, M; Marshall, D J; Martin, P G; Martínez-González, E; Masi, S; Matarrese, S; Matthai, F; Mazzotta, P; McGehee, P; Melchiorri, A; Mendes, L; Mennella, A; Migliaccio, M; Mitra, S; Miville-Deschênes, M -A; Moneti, A; Montier, L; Morgante, G; Mortlock, D; Munshi, D; Murphy, J A; Naselsky, P; Nati, F; Natoli, P; Netterfield, C B; Nørgaard-Nielsen, H U; North, C; Noviello, F; Novikov, D; Novikov, I; Osborne, S; Oxborrow, C A; Paci, F; Pagano, L; Pajot, F; Paoletti, D; Pasian, F; Patanchon, G; Perdereau, O; Perotto, L; Perrotta, F; Piacentini, F; Piat, M; Pierpaoli, E; Pietrobon, D; Plaszczynski, S; Pointecouteau, E; Polenta, G; Ponthieu, N; Popa, L; Poutanen, T; Pratt, G W; Prézeau, G; Prunet, S; Puget, J -L; Rachen, J P; Reinecke, M; Remazeilles, M; Renault, C; Ricciardi, S; Riller, T; Ristorcelli, I; Rocha, G; Rosset, C; Roudier, G; Rusholme, B; Santos, D; Savini, G; Shellard, E P S; Spencer, L D; Starck, J -L; Stolyarov, V; Stompor, R; Sudiwala, R; Sureau, F; Sutton, D; Suur-Uski, A -S; Sygnet, J -F; Tauber, J A; Tavagnacco, D; Terenzi, L; Tomasi, M; Tristram, M; Tucci, M; Umana, G; Valenziano, L; Valiviita, J; Van Tent, B; Vielva, P; Villa, F; Vittorio, N; Wade, L A; Wandelt, B D; Yvon, D; Zacchei, A; Zonca, A

    2014-01-01

    The Planck High Frequency Instrument (HFI) spectral response was determined through a series of ground based tests conducted with the HFI focal plane in a cryogenic environment prior to launch. The main goal of the spectral transmission tests was to measure the relative spectral response (including out-of-band signal rejection) of all HFI detectors. This was determined by measuring the output of a continuously scanned Fourier transform spectrometer coupled with all HFI detectors. As there is no on-board spectrometer within HFI, the ground-based spectral response experiments provide the definitive data set for the relative spectral calibration of the HFI. The spectral response of the HFI is used in Planck data analysis and component separation, this includes extraction of CO emission observed within Planck bands, dust emission, Sunyaev-Zeldovich sources, and intensity to polarization leakage. The HFI spectral response data have also been used to provide unit conversion and colour correction analysis tools. Ver...

  11. Spectral fluctuations and zeta functions

    International Nuclear Information System (INIS)

    Balazs, N.L.; Schmit, C.; Voros, A.

    1987-01-01

    The study theoretically and numerically the role of the fluctuations of eigenvalue spectra {μ/sub n} in a particular analytical continuation process applied to the (generalized) zeta function Z(s) = Σ/sub n/μ/sub n//sup -s/ for s large and positive. A particularly interesting example is the spectrum of the Laplacian on a triangular domain which tessellates a compact surface of constant negative curvature (of genus two). The authors indeed find that the fluctuations restrict the abscissa of convergence, and also affect the rate of convergence. This then initiates a new approach to the exploration of spectral fluctuations through the convergence of analytical continuation processes

  12. Multistage Spectral Relaxation Method for Solving the Hyperchaotic Complex Systems

    Directory of Open Access Journals (Sweden)

    Hassan Saberi Nik

    2014-01-01

    Full Text Available We present a pseudospectral method application for solving the hyperchaotic complex systems. The proposed method, called the multistage spectral relaxation method (MSRM is based on a technique of extending Gauss-Seidel type relaxation ideas to systems of nonlinear differential equations and using the Chebyshev pseudospectral methods to solve the resulting system on a sequence of multiple intervals. In this new application, the MSRM is used to solve famous hyperchaotic complex systems such as hyperchaotic complex Lorenz system and the complex permanent magnet synchronous motor. We compare this approach to the Runge-Kutta based ode45 solver to show that the MSRM gives accurate results.

  13. Digital generation of stochastic signals of arbitrary spectral shape

    International Nuclear Information System (INIS)

    Behringer, K.; Nishihara, H.; Spiekerman, G.

    1986-10-01

    For computer-simulation experiments in the development of noise monitoring systems three methods of generating ergodic Gaussian random noise with specified spectral properties have been investigated: digital filtering of white noise optimum symmetric FIR filters, a modified Rice formulation and an approximation of the Kac representation of noise. The proposed modified Rice formulation is a new noise generation method which is most efficient with regard to the computation time. By windowing subsequent Rice sequences a smooth noise record of any desired length can be produced. (author)

  14. Massively parallel signature sequencing.

    Science.gov (United States)

    Zhou, Daixing; Rao, Mahendra S; Walker, Roger; Khrebtukova, Irina; Haudenschild, Christian D; Miura, Takumi; Decola, Shannon; Vermaas, Eric; Moon, Keith; Vasicek, Thomas J

    2006-01-01

    Massively parallel signature sequencing is an ultra-high throughput sequencing technology. It can simultaneously sequence millions of sequence tags, and, therefore, is ideal for whole genome analysis. When applied to expression profiling, it reveals almost every transcript in the sample and provides its accurate expression level. This chapter describes the technology and its application in establishing stem cell transcriptome databases.

  15. Goldbach Partitions and Sequences

    Indian Academy of Sciences (India)

    IAS Admin

    as a sum of two primes (for even numbers) and three primes (for odd numbers). We call this the Goldbach sequence g(n), which may be converted into a binary sequence b(n) by mapping each even number to 0 and each odd number to 1. The resulting binary sequences may be used as pseudorandom sequences in ...

  16. Journal of Astrophysics and Astronomy | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    2016-01-27

    -Krishna ... Black Holes in Blazars. Variability of Spectral Energy Distribution of Blazar S5 0716+714 ... 2013 pp 273-296. On the Photometric Error Calibration for the Differential Light Curves of Point-like Active Galactic Nuclei.

  17. Application and analysis of performance of dqpsk advanced modulation format in spectral amplitude coding ocdma

    International Nuclear Information System (INIS)

    Memon, A.

    2015-01-01

    SAC (Spectral Amplitude Coding) is a technique of OCDMA (Optical Code Division Multiple Access) to encode and decode data bits by utilizing spectral components of the broadband source. Usually OOK (ON-Off-Keying) modulation format is used in this encoding scheme. To make SAC OCDMA network spectrally efficient, advanced modulation format of DQPSK (Differential Quaternary Phase Shift Keying) is applied, simulated and analyzed, m-sequence code is encoded in the simulated setup. Performance regarding various lengths of m-sequence code is also analyzed and displayed in the pictorial form. The results of the simulation are evaluated with the help of electrical constellation diagram, eye diagram and bit error rate graph. All the graphs indicate better transmission quality in case of advanced modulation format of DQPSK used in SAC OCDMA network as compared with OOK. (author)

  18. Application and Analysis of Performance of DQPSK Advanced Modulation Format in Spectral Amplitude Coding OCDMA

    Directory of Open Access Journals (Sweden)

    Abdul Latif Memon

    2014-04-01

    Full Text Available SAC (Spectral Amplitude Coding is a technique of OCDMA (Optical Code Division Multiple Access to encode and decode data bits by utilizing spectral components of the broadband source. Usually OOK (ON-Off-Keying modulation format is used in this encoding scheme. To make SAC OCDMA network spectrally efficient, advanced modulation format of DQPSK (Differential Quaternary Phase Shift Keying is applied, simulated and analyzed. m-sequence code is encoded in the simulated setup. Performance regarding various lengths of m-sequence code is also analyzed and displayed in the pictorial form. The results of the simulation are evaluated with the help of electrical constellation diagram, eye diagram and bit error rate graph. All the graphs indicate better transmission quality in case of advanced modulation format of DQPSK used in SAC OCDMA network as compared with OOK

  19. Auditory evoked fields elicited by spectral, temporal, and spectral-temporal changes in human cerebral cortex

    Directory of Open Access Journals (Sweden)

    Hidehiko eOkamoto

    2012-05-01

    Full Text Available Natural sounds contain complex spectral components, which are temporally modulated as time-varying signals. Recent studies have suggested that the auditory system encodes spectral and temporal sound information differently. However, it remains unresolved how the human brain processes sounds containing both spectral and temporal changes. In the present study, we investigated human auditory evoked responses elicited by spectral, temporal, and spectral-temporal sound changes by means of magnetoencephalography (MEG. The auditory evoked responses elicited by the spectral-temporal change were very similar to those elicited by the spectral change, but those elicited by the temporal change were delayed by 30 – 50 ms and differed from the others in morphology. The results suggest that human brain responses corresponding to spectral sound changes precede those corresponding to temporal sound changes, even when the spectral and temporal changes occur simultaneously.

  20. Tailored spiral in-out spectral-spatial water suppression pulses for magnetic resonance spectroscopic imaging

    NARCIS (Netherlands)

    Ma, Jun; Wismans, Carrie; Cao, Zhipeng; Klomp, DWJ; Wijnen, Jannie P; Grissom, William A

    2018-01-01

    PURPOSE: To develop short water suppression sequences for 7 T magnetic resonance spectroscopic imaging, with mitigation of subject-specific transmit RF field ( B1+) inhomogeneity. METHODS: Patient-tailored spiral in-out spectral-spatial saturation pulses were designed for a three-pulse WET water

  1. Sequence Classification Using Third-Order Moments

    DEFF Research Database (Denmark)

    Troelsgaard, Rasmus; Hansen, Lars Kai

    2017-01-01

    . The proposed method provides lower computational complexity at classification time than the usual likelihood-based methods. In order to demonstrate the properties of the proposed method, we perform classification of both simulated data and empirical data from a human activity recognition study.......Model-based classification of sequence data using a set of hidden Markov models is a well-known technique. The involved score function, which is often based on the class-conditional likelihood, can, however, be computationally demanding, especially for long data sequences. Inspired by recent...... theoretical advances in spectral learning of hidden Markov models, we propose a score function based on third-order moments. In particular, we propose to use the Kullback-Leibler divergence between theoretical and empirical third-order moments for classification of sequence data with discrete observations...

  2. Investigating the Innermost Jet Structures of Blazar S5 0716+714 Using Uniquely Dense Intra-day Photo-polarimetric Observations

    Directory of Open Access Journals (Sweden)

    Gopal Bhatta

    2016-10-01

    Full Text Available The sub-hour timescale variability commonly observed in blazars—widely known as intra-day or microvariability—has been extensively studied in optical photo-polarimetric bands over the past 25–30 years. In addition, there have been comprehensive theoretical discussions on the topic, with various models and scenarios proposed; however, the phenomenon still remains relatively poorly understood. Here we present the summary of our optical microvariability studies over the past few years based on multi-frequency photo-polarimetric Whole Earth Blazar Telescope (WEBT observation campaigns. The primary objective of the study was to explore the characteristics of the source microvariability on timescales of a few minutes to a few days using exceptionally dense photo-polarimetric observations. The results show that the source often displays fast variability with an amplitude as large as 0.3 mag within a few hours, as well as color variability on similar time scales often characterized by “bluer-when-brighter” trend. Similarly, the correlation between variability in flux and polarization appears to depend upon the configuration of the optical polarization angle relative to the positional angle of the innermost radio core of the jet. Other fascinating observations include a sudden and temporary disappearance in the observed variability lasting for ∼6 h. In addition, the modeling of individual microflares strongly suggests that the phenomenon of microvariability can be best explained by convolved emission from compact emission sites distributed stochastically in the turbulent jet. Besides, analysis of some of the well resolved micro-flares exhibiting high degrees of polarization points towards a complex magnetic geometry pervading the jet with the possible presence of small-scale regions of highly ordered and enhanced magnetic field similar to so-called “magnetic islands”.

  3. Light distribution system comprising spectral conversion means

    DEFF Research Database (Denmark)

    2012-01-01

    System (200, 300) for the distribution of white light, having a supply side (201, 301, 401) and a delivery side (202, 302, 402), the system being configured for guiding light with a multitude of visible wavelengths in a propagation direction P from the supply side to the distribution side...... fibre being operationally connected to the spectral conversion fibre having a length extending from an input end (221, 321)to an output end (222, 322), the spectral conversion fibre comprising a photoluminescent agent (511, 611, 711) for converting light of a first wavelength to light of a second......, longer wavelength,a spectral conversion characteristics of the spectral conversion fibre being essentially determined by the spectral absorption and emission properties of the photoluminescent agent, the amount of photo- luminescent agent,and the distribution of the photoluminescent agent in the spectral...

  4. Spectral functions in mathematics and physics

    CERN Document Server

    Kirsten, Klaus

    2002-01-01

    The literature on the spectral analysis of second order elliptic differential operators contains a great deal of information on the spectral functions for explicitly known spectra. The same is not true, however, for situations where the spectra are not explicitly known. Over the last several years, the author and his colleagues have developed new, innovative methods for the exact analysis of a variety of spectral functions occurring in spectral geometry and under external conditions in statistical mechanics and quantum field theory. Spectral Functions in Mathematics and Physics presents a detailed overview of these advances. The author develops and applies methods for analyzing determinants arising when the external conditions originate from the Casimir effect, dielectric media, scalar backgrounds, and magnetic backgrounds. The zeta function underlies all of these techniques, and the book begins by deriving its basic properties and relations to the spectral functions. The author then uses those relations to d...

  5. Quantitative spectral comparison by weighted spectral difference for protein higher order structure confirmation.

    Science.gov (United States)

    Dinh, Nikita N; Winn, Bradley C; Arthur, Kelly K; Gabrielson, John P

    2014-11-01

    Previously, different approaches of spectral comparison were evaluated, and the spectral difference (SD) method was shown to be valuable for its linearity with spectral changes and its independence on data spacing (Anal. Biochem. 434 (2013) 153-165). In this note, we present an enhancement of the SD calculation, referred to as the "weighted spectral difference" (WSD), by implementing a weighting function based on relative signal magnitude. While maintaining the advantages of the SD method, WSD improves the method sensitivity to spectral changes and tolerance for baseline inclusion. Furthermore, a generalized formula is presented to unify further development of approaches to quantify spectral difference. Copyright © 2014 Elsevier Inc. All rights reserved.

  6. Nonparametric combinatorial sequence models.

    Science.gov (United States)

    Wauthier, Fabian L; Jordan, Michael I; Jojic, Nebojsa

    2011-11-01

    This work considers biological sequences that exhibit combinatorial structures in their composition: groups of positions of the aligned sequences are "linked" and covary as one unit across sequences. If multiple such groups exist, complex interactions can emerge between them. Sequences of this kind arise frequently in biology but methodologies for analyzing them are still being developed. This article presents a nonparametric prior on sequences which allows combinatorial structures to emerge and which induces a posterior distribution over factorized sequence representations. We carry out experiments on three biological sequence families which indicate that combinatorial structures are indeed present and that combinatorial sequence models can more succinctly describe them than simpler mixture models. We conclude with an application to MHC binding prediction which highlights the utility of the posterior distribution over sequence representations induced by the prior. By integrating out the posterior, our method compares favorably to leading binding predictors.

  7. Spectral properties of nuclear matter

    International Nuclear Information System (INIS)

    Bozek, P

    2006-01-01

    We review self-consistent spectral methods for nuclear matter calculations. The in-medium T-matrix approach is conserving and thermodynamically consistent. It gives both the global and the single-particle properties the system. The T-matrix approximation allows to address the pairing phenomenon in cold nuclear matter. A generalization of nuclear matter calculations to the super.uid phase is discussed and numerical results are presented for this case. The linear response of a correlated system going beyond the Hartree-Fock+ Random-Phase-Approximation (RPA) scheme is studied. The polarization is obtained by solving a consistent Bethe-Salpeter (BS) equation for the coupling of dressed nucleons to an external field. We find that multipair contributions are important for the spin(isospin) response when the interaction is spin(isospin) dependent

  8. Signature spectrale des grains interstellaires.

    Science.gov (United States)

    Léger, A.

    Notre connaissance de la nature des grains interstellaires reposait sur un nombre très restreint de signatures spectrales dans la courbe d'extinction du milieu interstellaire. Une information considérable est contenue dans les 40 bandes interstellaires diffuses dans le visible, mais reste inexploitée. L'interprétation récente des cinq bandes IR en émission, en terme de molécules d'hydrocarbures aromatiques polycycliques, est développée. Elle permet l'utilisation d'une information spectroscopique comparable, à elle seule, à ce sur quoi était basée jusqu'alors notre connaissance de la matière interstellaire condensée. Différentes implications de cette mise en évidence sont proposées.

  9. Elementary principles of spectral distributions

    International Nuclear Information System (INIS)

    French, J.B.

    1980-01-01

    It is a common observation that as we add particles, one by one, to a simple system, things get steadily more and more complicated. For example if the system is describable in shell-model terms, i.e., with a model space in which m particles are distributed over N single-particle states, then as long as m << N, the dimensionality increases rapidly with particle number. On the other hand, for the usual (1 + 2)-body Hamiltonian, the (m greater than or equal to 2)-particle spectrum and wave functions are determined by operators defined in the one-particle space (for the single-particle energies) and the two-particle space (for the interactions). We may say then that the input information becomes more and more fragmented as the particle number increases, the fixed amount of information being distributed over more and more matrix elements. On the other hand there arise also new simplicities whose origin is connected with the operation of statistical laws. There is a macroscopic simplicity corresponding to the fact that the smoothed spectrum takes on a characteristic shape defined by a few parameters (low-order moments) of the spectrum. There is a microscopic simplicity corresponding to a remarkable spectral rigidity which extends over the entire spectrum and guarantees us that the fluctuations from uniformity in the spectrum are small and in many cases carry little information. The purpose of spectral-distribution theory, as applied to these problems, is to deal with the complexities by taking advantage of the simplicities

  10. Buckling feedback of the spectral calculations

    International Nuclear Information System (INIS)

    Jing Xingqing; Shan Wenzhi; Luo Jingyu

    1992-01-01

    This paper studies the problems about buckling feedback of spectral calculations in physical calculations of the reactor and presents a useful method by which the buckling feedback of spectral calculations is implemented. The effect of the buckling feedback in spectra and the broad group cross section, convergence of buckling feedback iteration and the effect of the spectral zones dividing are discussed in the calculations. This method has been used for the physical design of HTR-10 MW Test Module

  11. Spectral mapping theorems a bluffer's guide

    CERN Document Server

    Harte, Robin

    2014-01-01

    Written by an author who was at the forefront of developments in multi-variable spectral theory during the seventies and the eighties, this guide sets out to describe in detail the spectral mapping theorem in one, several and many variables. The basic algebraic systems – semigroups, rings and linear algebras – are summarised, and then topological-algebraic systems, including Banach algebras, to set up the basic language of algebra and analysis. Spectral Mapping Theorems is written in an easy-to-read and engaging manner and will be useful for both the beginner and expert. It will be of great importance to researchers and postgraduates studying spectral theory.

  12. Spectrally-engineered solar thermal photovoltaic devices

    Energy Technology Data Exchange (ETDEWEB)

    Lenert, Andrej; Bierman, David; Chan, Walker; Celanovic, Ivan; Soljacic, Marin; Wang, Evelyn N.; Nam, Young Suk; McEnaney, Kenneth; Kraemer, Daniel; Chen, Gang

    2018-03-27

    A solar thermal photovoltaic device, and method of forming same, includes a solar absorber and a spectrally selective emitter formed on either side of a thermally conductive substrate. The solar absorber is configured to absorb incident solar radiation. The solar absorber and the spectrally selective emitter are configured with an optimized emitter-to-absorber area ratio. The solar thermal photovoltaic device also includes a photovoltaic cell in thermal communication with the spectrally selective emitter. The spectrally selective emitter is configured to permit high emittance for energies above a bandgap of the photovoltaic cell and configured to permit low emittance for energies below the bandgap.

  13. Global and local aspects of spectral actions

    Science.gov (United States)

    Iochum, B.; Levy, C.; Vassilevich, D. V.

    2012-09-01

    The principal object in noncommutative geometry is the spectral triple consisting of an algebra {A}, a Hilbert space {H} and a Dirac operator {D}. Field theories are incorporated in this approach by the spectral action principle, which sets the field theory action to Tr\\,f( {D}^2/\\Lambda ^2), where f is a real function such that the trace exists and Λ is a cutoff scale. In the low-energy (weak-field) limit, the spectral action reproduces reasonably well the known physics including the standard model. However, not much is known about the spectral action beyond the low-energy approximation. In this paper, after an extensive introduction to spectral triples and spectral actions, we study various expansions of the spectral actions (exemplified by the heat kernel). We derive the convergence criteria. For a commutative spectral triple, we compute the heat kernel on the torus up to the second order in gauge connection and consider limiting cases. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical in honour of Stuart Dowker’s 75th birthday devoted to ‘Applications of zeta functions and other spectral functions in mathematics and physics’.

  14. Genome Sequence Databases (Overview): Sequencing and Assembly

    Energy Technology Data Exchange (ETDEWEB)

    Lapidus, Alla L.

    2009-01-01

    From the date its role in heredity was discovered, DNA has been generating interest among scientists from different fields of knowledge: physicists have studied the three dimensional structure of the DNA molecule, biologists tried to decode the secrets of life hidden within these long molecules, and technologists invent and improve methods of DNA analysis. The analysis of the nucleotide sequence of DNA occupies a special place among the methods developed. Thanks to the variety of sequencing technologies available, the process of decoding the sequence of genomic DNA (or whole genome sequencing) has become robust and inexpensive. Meanwhile the assembly of whole genome sequences remains a challenging task. In addition to the need to assemble millions of DNA fragments of different length (from 35 bp (Solexa) to 800 bp (Sanger)), great interest in analysis of microbial communities (metagenomes) of different complexities raises new problems and pushes some new requirements for sequence assembly tools to the forefront. The genome assembly process can be divided into two steps: draft assembly and assembly improvement (finishing). Despite the fact that automatically performed assembly (or draft assembly) is capable of covering up to 98% of the genome, in most cases, it still contains incorrectly assembled reads. The error rate of the consensus sequence produced at this stage is about 1/2000 bp. A finished genome represents the genome assembly of much higher accuracy (with no gaps or incorrectly assembled areas) and quality ({approx}1 error/10,000 bp), validated through a number of computer and laboratory experiments.

  15. The Spectral Index and Beaming Effect for Radio Sources J. Pan ...

    Indian Academy of Sciences (India)

    J. Pan & J. H. Fan. ∗. Center for Astrophysics, Guangzhou University, Guangzhou 510006, China. ∗ e-mail: jhfan_cn@yahoo.com.cn. Abstract. In this paper, we revisited the relationship between the spec- tral index and the core-dominance parameter using a larger sample of blazars. Conclusively, we explain that the ...

  16. Broad-Band Spectral Indices Variability of BL Lacertae by Wavelet ...

    Indian Academy of Sciences (India)

    object of active galactic nuclei (AGNs) which is well known by the pronounced variability at all wavelengths, from the radio to γ-ray band. It has been one of the targets of the Whole Earth Blazar Telescope (WEBT) in two or more observation campaigns after 1999 (see e.g., Villata et al. 2002, 2004, 2009), and has also been.

  17. Anomaly Detection in Sequences

    Data.gov (United States)

    National Aeronautics and Space Administration — We present a set of novel algorithms which we call sequenceMiner, that detect and characterize anomalies in large sets of high-dimensional symbol sequences that...

  18. DNA sequencing conference, 2

    Energy Technology Data Exchange (ETDEWEB)

    Cook-Deegan, R.M. [Georgetown Univ., Kennedy Inst. of Ethics, Washington, DC (United States); Venter, J.C. [National Inst. of Neurological Disorders and Strokes, Bethesda, MD (United States); Gilbert, W. [Harvard Univ., Cambridge, MA (United States); Mulligan, J. [Stanford Univ., CA (United States); Mansfield, B.K. [Oak Ridge National Lab., TN (United States)

    1991-06-19

    This conference focused on DNA sequencing, genetic linkage mapping, physical mapping, informatics and bioethics. Several were used to study this sequencing and mapping. This article also discusses computer hardware and software aiding in the mapping of genes.

  19. sequenceMiner algorithm

    Data.gov (United States)

    National Aeronautics and Space Administration — Detecting and describing anomalies in large repositories of discrete symbol sequences. sequenceMiner has been open-sourced! Download the file below to try it out....

  20. Maximizing the spectral and energy efficiency of ARQ with a fixed outage probability

    KAUST Repository

    Hadjtaieb, Amir

    2015-10-05

    This paper studies the spectral and energy efficiency of automatic repeat request (ARQ) in Nakagami-m block-fading channels. The source encodes each packet into L similar sequences and transmits them to the destination in the L subsequent time slots. The destination combines the L sequences using maximal ratio combining and tries to decode the information. In case of decoding failure, the destination feeds back a negative acknowledgment and then the source sends the same L sequences to the destination. This process continues until successful decoding occurs at the destination with no limit on the number of retransmissions. We consider two optimization problems. In the first problem, we maximize the spectral efficiency of the system with respect to the rate for a fixed power. In the second problem, we maximize the energy efficiency with respect to the transmitted power for a fixed rate. © 2015 IEEE.

  1. Spectral filtering for plant production

    Science.gov (United States)

    Young, Roy E.; Mcmahon, Margaret J.; Rajapakse, Nihal C.; Decoteau, Dennis R.

    1994-01-01

    Both plants and animals have one general commonality in their perception of light. They both are sensitive primarily to the 400 to 700 nm wavelength portion of the electromagnetic spectrum. This is referred to as the visible spectrum for animals and as the photosynthetically active radiation (PAR) spectrum for plants. Within this portion of the spectrum, animals perceive colors. Relatively recently it has been learned that within this same spectral range plants also demonstrate varying responses at different wavelengths, somewhat analogous to the definition of various colors at specific wavelengths. Although invisible to the human eye, portions of the electromagnetic spectrum on either side of the visible range are relatively inactive photosynthetically but have been found to influence important biological functions. These portions include the ultraviolet (UV approximately equal to 280-400 nm) and the far-red (FR approximately equal to 700-800 nm). The basic photoreceptor of plants for photosynthesis is chlorophyll. It serves to capture radiant energy which combined with carbon dioxide and water produces oxygen and assimulated carbon, used for the synthesis of cell wall polysaccarides, proteins, membrane lipids and other cellular constituents. The energy and carbon building blocks of photosynthesis sustain growth of plants. On the other hand, however, there are other photoreceptors, or pigments, that function as signal transducers to provide information that controls many physiological and morphological responses of how a plant grows. Known photomorphogenic receptors include phytochrome (the red/far-red sensor in the narrow bands of 655-665 nm and 725-735 nm ranges, respectively) and 'cryptochrome' (the hypothetical UV-B sensor in the 280-320 nm range). Since the USDA team of W. L. Butler, S. B. Hendricks, H. A. Borthwick, H. A. Siegleman and K. Norris in Beltsville, MD detected by spectroscopy, extracted and identified phytochrome as a protein in the 1950's, many

  2. A Black Hole Spectral Signature

    Science.gov (United States)

    Titarchuk, Lev; Laurent, Philippe

    2000-03-01

    An accreting black hole is, by definition, characterized by the drain. Namely, the matter falls into a black hole much the same way as water disappears down a drain matter goes in and nothing comes out. As this can only happen in a black hole, it provides a way to see ``a black hole'', an unique observational signature. The accretion proceeds almost in a free-fall manner close to the black hole horizon, where the strong gravitational field dominates the pressure forces. In this paper we present analytical calculations and Monte-Carlo simulations of the specific features of X-ray spectra formed as a result of upscattering of the soft (disk) photons in the converging inflow (CI) into the black hole. The full relativistic treatment has been implemented to reproduce these spectra. We show that spectra in the soft state of black hole systems (BHS) can be described as the sum of a thermal (disk) component and the convolution of some fraction of this component with the CI upscattering spread (Greens) function. The latter boosted photon component is seen as an extended power-law at energies much higher than the characteristic energy of the soft photons. We demonstrate the stability of the power spectral index over a wide range of the plasma temperature 0 - 10 keV and mass accretion rates (higher than 2 in Eddington units). We also demonstrate that the sharp high energy cutoff occurs at energies of 200-400 keV which are related to the average energy of electrons mec2 impinging upon the event horizon. The spectrum is practically identical to the standard thermal Comptonization spectrum when the CI plasma temperature is getting of order of 50 keV (the typical ones for the hard state of BHS). In this case one can see the effect of the bulk motion only at high energies where there is an excess in the CI spectrum with respect to the pure thermal one. Furthermore we demonstrate that the change of spectral shapes from the soft X-ray state to the hard X-ray state is clearly to be

  3. Spectral affinity in protein networks.

    Science.gov (United States)

    Voevodski, Konstantin; Teng, Shang-Hua; Xia, Yu

    2009-11-29

    Protein-protein interaction (PPI) networks enable us to better understand the functional organization of the proteome. We can learn a lot about a particular protein by querying its neighborhood in a PPI network to find proteins with similar function. A spectral approach that considers random walks between nodes of interest is particularly useful in evaluating closeness in PPI networks. Spectral measures of closeness are more robust to noise in the data and are more precise than simpler methods based on edge density and shortest path length. We develop a novel affinity measure for pairs of proteins in PPI networks, which uses personalized PageRank, a random walk based method used in context-sensitive search on the Web. Our measure of closeness, which we call PageRank Affinity, is proportional to the number of times the smaller-degree protein is visited in a random walk that restarts at the larger-degree protein. PageRank considers paths of all lengths in a network, therefore PageRank Affinity is a precise measure that is robust to noise in the data. PageRank Affinity is also provably related to cluster co-membership, making it a meaningful measure. In our experiments on protein networks we find that our measure is better at predicting co-complex membership and finding functionally related proteins than other commonly used measures of closeness. Moreover, our experiments indicate that PageRank Affinity is very resilient to noise in the network. In addition, based on our method we build a tool that quickly finds nodes closest to a queried protein in any protein network, and easily scales to much larger biological networks. We define a meaningful way to assess the closeness of two proteins in a PPI network, and show that our closeness measure is more biologically significant than other commonly used methods. We also develop a tool, accessible at http://xialab.bu.edu/resources/pnns, that allows the user to quickly find nodes closest to a queried vertex in any protein

  4. Spectral affinity in protein networks

    Directory of Open Access Journals (Sweden)

    Teng Shang-Hua

    2009-11-01

    Full Text Available Abstract Background Protein-protein interaction (PPI networks enable us to better understand the functional organization of the proteome. We can learn a lot about a particular protein by querying its neighborhood in a PPI network to find proteins with similar function. A spectral approach that considers random walks between nodes of interest is particularly useful in evaluating closeness in PPI networks. Spectral measures of closeness are more robust to noise in the data and are more precise than simpler methods based on edge density and shortest path length. Results We develop a novel affinity measure for pairs of proteins in PPI networks, which uses personalized PageRank, a random walk based method used in context-sensitive search on the Web. Our measure of closeness, which we call PageRank Affinity, is proportional to the number of times the smaller-degree protein is visited in a random walk that restarts at the larger-degree protein. PageRank considers paths of all lengths in a network, therefore PageRank Affinity is a precise measure that is robust to noise in the data. PageRank Affinity is also provably related to cluster co-membership, making it a meaningful measure. In our experiments on protein networks we find that our measure is better at predicting co-complex membership and finding functionally related proteins than other commonly used measures of closeness. Moreover, our experiments indicate that PageRank Affinity is very resilient to noise in the network. In addition, based on our method we build a tool that quickly finds nodes closest to a queried protein in any protein network, and easily scales to much larger biological networks. Conclusion We define a meaningful way to assess the closeness of two proteins in a PPI network, and show that our closeness measure is more biologically significant than other commonly used methods. We also develop a tool, accessible at http://xialab.bu.edu/resources/pnns, that allows the user to

  5. Spectral self-imaging effect by time-domain multilevel phase modulation of a periodic pulse train.

    Science.gov (United States)

    Caraquitena, José; Beltrán, Marta; Llorente, Roberto; Martí, Javier; Muriel, Miguel A

    2011-03-15

    We propose and analyze a novel (to our knowledge) approach to implement the spectral self-imaging effect of optical frequency combs. The technique is based on time-domain multilevel phase-only modulation of a periodic optical pulse train. The method admits both infinite- and finite-duration periodic pulse sequences. We show that the fractional spectral self-imaging effect allows one to reduce by an integer factor the comb frequency spacing. Numerical simulation results support our theoretical analysis.

  6. Spectral self-imaging effect by time-domain multilevel phase modulation of a periodic pulse train

    OpenAIRE

    Caraquitena Sales, José; Beltrán, Marta; Llorente, Roberto; Martí Sendra, Javier; Muriel, Miguel A.

    2011-01-01

    We propose and analyze a novel (to our knowledge) approach to implement the spectral self-imaging effect of optical frequency combs. The technique is based on time-domain multilevel phase-only modulation of a periodic optical pulse train. The method admits both infinite- and finite-duration periodic pulse sequences. We show that the fractional spectral self-imaging effect allows one to reduce by an integer factor the comb frequency spacing. Numerical simulation results support our theoretical...

  7. Balanced SSFP-like steady-state imaging using small-tip fast recovery with a spectral prewinding pulse.

    Science.gov (United States)

    Sun, Hao; Fessler, Jeffrey A; Noll, Douglas C; Nielsen, Jon-Fredrik

    2016-02-01

    Small-tip fast recovery (STFR) imaging has been proposed recently as a potential alternative to balanced steady-state free precession (bSSFP). STFR relies on a tailored "tip-up" radio-frequency pulse to achieve comparable signal level as bSSFP, but with reduced banding artifacts and transient oscillations, and is compatible with magnetization-preparation pulses. Previous STFR implementations used two-dimensional or three-dimensional pulses spatially tailored to the accumulated phase calculated from a B0 field map, making the steady-state STFR signal contain some T2* weighting. Here, we propose to replace the spatially tailored pulse with a recently introduced spectrally selective "pre-winding" pulse that is precomputed to a target frequency range. The proposed "spectral-STFR" sequence produces T2/T1-weighted images similar to bSSFP, but with reduced banding and potentially other benefits. We investigated the steady-state signal properties of spectral-STFR using simulations, and phantom and human volunteer experiments. Our simulation and experimental results showed that the spectral-STFR sequence has similar signal level and tissue contrast as bSSFP, but has a wider passband and more consistent banding profiles across different tissues (e.g., less hyperintense signal at band edges for low flip angles). Care is needed in designing the spectral radio-frequency pulse to ensure that the small tip angle approximation holds during radio-frequency transmission. Spectral-STFR has similar tissue contrast as bSSFP but a wider passband and more consistent cerebrospinal fluid/brain tissue contrast across the passband. The spectral-STFR sequence is a potential alternative to bSSFP in some applications. Compared to a spatially tailored STFR sequence, spectral-STFR can be precomputed, is easier to implement in practice, and potentially has more uniform image contrast and minimal T2* weighting. © 2015 Wiley Periodicals, Inc.

  8. Journal of Astrophysics and Astronomy | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... 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 ...

  9. Total spectral distributions from Hawking radiation

    Science.gov (United States)

    Broda, Bogusław

    2017-11-01

    Taking into account the time dependence of the Hawking temperature and finite evaporation time of the black hole, the total spectral distributions of the radiant energy and of the number of particles have been explicitly calculated and compared to their temporary (initial) blackbody counterparts (spectral exitances).

  10. A Spectral Emissivity Library of Spoil Substrates

    Czech Academy of Sciences Publication Activity Database

    Pivovarník, Marek; Pikl, Miroslav; Frouz, J.; Zemek, František; Kopačková, V.; Notesco, G.; Ben Dor, E.

    2016-01-01

    Roč. 1, č. 2 (2016) E-ISSN 2306-5729 R&D Projects: GA MŠk(CZ) LO1415 Institutional support: RVO:86652079 Keywords : post- mining sites * spectral emissivity * spectral library * spoil substrates Subject RIV: EH - Ecology, Behaviour OBOR OECD: Environmental sciences (social aspects to be 5.7)

  11. Relaxation schemes for Chebyshev spectral multigrid methods

    Science.gov (United States)

    Kang, Yimin; Fulton, Scott R.

    1993-01-01

    Two relaxation schemes for Chebyshev spectral multigrid methods are presented for elliptic equations with Dirichlet boundary conditions. The first scheme is a pointwise-preconditioned Richardson relaxation scheme and the second is a line relaxation scheme. The line relaxation scheme provides an efficient and relatively simple approach for solving two-dimensional spectral equations. Numerical examples and comparisons with other methods are given.

  12. Active spectral imaging nondestructive evaluation (SINDE) camera

    Energy Technology Data Exchange (ETDEWEB)

    Simova, E.; Rochefort, P.A., E-mail: eli.simova@cnl.ca [Canadian Nuclear Laboratories, Chalk River, Ontario (Canada)

    2016-06-15

    A proof-of-concept video camera for active spectral imaging nondestructive evaluation has been demonstrated. An active multispectral imaging technique has been implemented in the visible and near infrared by using light emitting diodes with wavelengths spanning from 400 to 970 nm. This shows how the camera can be used in nondestructive evaluation to inspect surfaces and spectrally identify materials and corrosion. (author)

  13. Total spectral distributions from Hawking radiation

    Energy Technology Data Exchange (ETDEWEB)

    Broda, Boguslaw [University of Lodz, Department of Theoretical Physics, Faculty of Physics and Applied Informatics, Lodz (Poland)

    2017-11-15

    Taking into account the time dependence of the Hawking temperature and finite evaporation time of the black hole, the total spectral distributions of the radiant energy and of the number of particles have been explicitly calculated and compared to their temporary (initial) blackbody counterparts (spectral exitances). (orig.)

  14. Stellar Spectral Classification with Locality Preserving Projections ...

    Indian Academy of Sciences (India)

    With the help of computer tools and algorithms, automatic stellar spectral classification has become an area of current interest. The process of stellar spectral classification mainly includes two steps: dimension reduction and classification. As a popular dimensionality reduction technique, Principal Component Analysis (PCA) ...

  15. Basic Functional Analysis Puzzles of Spectral Flow

    DEFF Research Database (Denmark)

    Booss-Bavnbek, Bernhelm

    2011-01-01

    We explain an array of basic functional analysis puzzles on the way to general spectral flow formulae and indicate a direction of future topological research for dealing with these puzzles.......We explain an array of basic functional analysis puzzles on the way to general spectral flow formulae and indicate a direction of future topological research for dealing with these puzzles....

  16. Measurement of spectral linewidths of semiconductor lasers

    Energy Technology Data Exchange (ETDEWEB)

    Du Xiaocheng; He Zhengchuan; Tang Sulan

    1987-03-01

    Based on the van der Pol equation, formulas describing the measurement of spectral linewidths of semiconductor lasers with the delayed self-heterodyne method were deduced and the influence of the spectral parameters on the measurement are given. Experimental results of single frequency semiconductor lasers are reported.

  17. Online Multi-Spectral Meat Inspection

    DEFF Research Database (Denmark)

    Nielsen, Jannik Boll; Larsen, Anders Boesen Lindbo

    2013-01-01

    We perform an explorative study on multi-spectral image data from a prototype device developed for fast online quality inspection of meat products. Because the camera setup is built for speed, we sacrifice exact pixel correspondences between the different bands of the multi-spectral images. Our...

  18. Sums of two-dimensional spectral triples

    DEFF Research Database (Denmark)

    Christensen, Erik; Ivan, Cristina

    2007-01-01

    We study countable sums of two dimensional modules for the continuous complex functions on a compact metric space and show that it is possible to construct a spectral triple which gives the original metric back. This spectral triple will be finitely summable for any positive parameter. We also co...

  19. Spectral features : How to reduce them

    NARCIS (Netherlands)

    Brug, H. van; Bloemendal, D. ten; Goeij, B. de; Vink, R.; Maresi, L.

    2009-01-01

    Spectral features are introduced by the diffuser that is used during on-board sun calibration. New findings are presented on how to reduce the size of these spectral features. Reduction can be obtained via optical design of the calibration unit, but also in creating a better diffuser. A novel

  20. Spectral Learning for Supervised Topic Models.

    Science.gov (United States)

    Ren, Yong; Wang, Yining; Zhu, Jun

    2018-03-01

    Supervised topic models simultaneously model the latent topic structure of large collections of documents and a response variable associated with each document. Existing inference methods are based on variational approximation or Monte Carlo sampling, which often suffers from the local minimum defect. Spectral methods have been applied to learn unsupervised topic models, such as latent Dirichlet allocation (LDA), with provable guarantees. This paper investigates the possibility of applying spectral methods to recover the parameters of supervised LDA (sLDA). We first present a two-stage spectral method, which recovers the parameters of LDA followed by a power update method to recover the regression model parameters. Then, we further present a single-phase spectral algorithm to jointly recover the topic distribution matrix as well as the regression weights. Our spectral algorithms are provably correct and computationally efficient. We prove a sample complexity bound for each algorithm and subsequently derive a sufficient condition for the identifiability of sLDA. Thorough experiments on synthetic and real-world datasets verify the theory and demonstrate the practical effectiveness of the spectral algorithms. In fact, our results on a large-scale review rating dataset demonstrate that our single-phase spectral algorithm alone gets comparable or even better performance than state-of-the-art methods, while previous work on spectral methods has rarely reported such promising performance.

  1. Discrimination and streaming of speech sounds based on differences in interaural and spectral cues.

    Science.gov (United States)

    David, Marion; Lavandier, Mathieu; Grimault, Nicolas; Oxenham, Andrew J

    2017-09-01

    Differences in spatial cues, including interaural time differences (ITDs), interaural level differences (ILDs) and spectral cues, can lead to stream segregation of alternating noise bursts. It is unknown how effective such cues are for streaming sounds with realistic spectro-temporal variations. In particular, it is not known whether the high-frequency spectral cues associated with elevation remain sufficiently robust under such conditions. To answer these questions, sequences of consonant-vowel tokens were generated and filtered by non-individualized head-related transfer functions to simulate the cues associated with different positions in the horizontal and median planes. A discrimination task showed that listeners could discriminate changes in interaural cues both when the stimulus remained constant and when it varied between presentations. However, discrimination of changes in spectral cues was much poorer in the presence of stimulus variability. A streaming task, based on the detection of repeated syllables in the presence of interfering syllables, revealed that listeners can use both interaural and spectral cues to segregate alternating syllable sequences, despite the large spectro-temporal differences between stimuli. However, only the full complement of spatial cues (ILDs, ITDs, and spectral cues) resulted in obligatory streaming in a task that encouraged listeners to integrate the tokens into a single stream.

  2. Meson spectral functions at finite temperature

    International Nuclear Information System (INIS)

    Wetzorke, I.; Karsch, F.; Laermann, E.; Petreczky, P.; Stickan, S.

    2002-01-01

    The Maximum Entropy Method provides a Bayesian approach to reconstruct the spectral functions from discrete points in Euclidean time. The applicability of the approach at finite temperature is probed with the thermal meson correlation function. Furthermore the influence of fuzzing/smearing techniques on the spectral shape is investigated. We present first results for meson spectral functions at several temperatures below and above T c . The correlation functions were obtained from quenched calculations with Clover fermions on large isotropic lattices of the size (24 - 64) 3 x 16. We compare the resulting pole masses with the ones obtained from standard 2-exponential fits of spatial and temporal correlation functions at finite temperature and in the vacuum. The deviation of the meson spectral functions from free spectral functions is examined above the critical temperature

  3. Meson spectral functions at finite temperature

    International Nuclear Information System (INIS)

    Wetzorke, I.; Karsch, F.; Laermann, E.; Petreczky, P.; Stickan, S.

    2001-10-01

    The Maximum Entropy Method provides a Bayesian approach to reconstruct the spectral functions from discrete points in Euclidean time. The applicability of the approach at finite temperature is probed with the thermal meson correlation function. Furthermore the influence of fuzzing/smearing techniques on the spectral shape is investigated. We present first results for meson spectral functions at several temperatures below and above T c . The correlation functions were obtained from quenched calculations with Clover fermions on large isotropic lattices of the size (24 - 64) 3 x 16. We compare the resulting pole masses with the ones obtained from standard 2-exponential fits of spatial and temporal correlation functions at finite temperature and in the vacuum. The deviation of the meson spectral functions from free spectral functions is examined above the critical temperature. (orig.)

  4. Meson spectral functions at finite temperature

    Energy Technology Data Exchange (ETDEWEB)

    Wetzorke, I.; Karsch, F.; Laermann, E.; Petreczky, P.; Stickan, S

    2002-03-01

    The Maximum Entropy Method provides a Bayesian approach to reconstruct the spectral functions from discrete points in Euclidean time. The applicability of the approach at finite temperature is probed with the thermal meson correlation function. Furthermore the influence of fuzzing/smearing techniques on the spectral shape is investigated. We present first results for meson spectral functions at several temperatures below and above T{sub c}. The correlation functions were obtained from quenched calculations with Clover fermions on large isotropic lattices of the size (24 - 64){sup 3} x 16. We compare the resulting pole masses with the ones obtained from standard 2-exponential fits of spatial and temporal correlation functions at finite temperature and in the vacuum. The deviation of the meson spectral functions from free spectral functions is examined above the critical temperature.

  5. Meson spectral functions at finite temperature

    Energy Technology Data Exchange (ETDEWEB)

    Wetzorke, I.; Karsch, F.; Laermann, E.; Petreczky, P.; Stickan, S. [Bielefeld Univ. (Germany). Fakultaet fuer Physik

    2001-10-01

    The Maximum Entropy Method provides a Bayesian approach to reconstruct the spectral functions from discrete points in Euclidean time. The applicability of the approach at finite temperature is probed with the thermal meson correlation function. Furthermore the influence of fuzzing/smearing techniques on the spectral shape is investigated. We present first results for meson spectral functions at several temperatures below and above T{sub c}. The correlation functions were obtained from quenched calculations with Clover fermions on large isotropic lattices of the size (24 - 64){sup 3} x 16. We compare the resulting pole masses with the ones obtained from standard 2-exponential fits of spatial and temporal correlation functions at finite temperature and in the vacuum. The deviation of the meson spectral functions from free spectral functions is examined above the critical temperature. (orig.)

  6. Extracting attosecond delays from spectrally overlapping interferograms

    Science.gov (United States)

    Jordan, Inga; Wörner, Hans Jakob

    2018-02-01

    Attosecond interferometry is becoming an increasingly popular technique for measuring the dynamics of photoionization in real time. Whereas early measurements focused on atomic systems with very simple photoelectron spectra, the technique is now being applied to more complex systems including isolated molecules and solids. The increase in complexity translates into an augmented spectral congestion, unavoidably resulting in spectral overlap in attosecond interferograms. Here, we discuss currently used methods for phase retrieval and introduce two new approaches for determining attosecond photoemission delays from spectrally overlapping photoelectron spectra. We show that the previously used technique, consisting in the spectral integration of the areas of interest, does in general not provide reliable results. Our methods resolve this problem, thereby opening the technique of attosecond interferometry to complex systems and fully exploiting its specific advantages in terms of spectral resolution compared to attosecond streaking.

  7. Spectral analysis of bedform dynamics

    DEFF Research Database (Denmark)

    Winter, Christian; Ernstsen, Verner Brandbyge; Noormets, Riko

    Successive multibeam echo sounder surveys in tidal channels off Esbjerg (Denmark) on the North Sea coast reveal the dynamics of subaquatic compound dunes. Mainly driven by tidal currents, dune structures show complex migration patterns in all temporal and spatial scales. Common methods for the an....... The proposed method overcomes the above mentioned problems of common descriptive analysis as it is an objective and straightforward mathematical process. The spectral decomposition of superimposed dunes allows a detailed description and analysis of dune patterns and migration.......Successive multibeam echo sounder surveys in tidal channels off Esbjerg (Denmark) on the North Sea coast reveal the dynamics of subaquatic compound dunes. Mainly driven by tidal currents, dune structures show complex migration patterns in all temporal and spatial scales. Common methods...... allows the application of a procedure, which has been a standard for the analysis of water waves for long times: The bathymetric signal of a cross-section of subaquatic compound dunes is approximated by the sum of a set of harmonic functions, derived by Fourier transformation. If the wavelength...

  8. Spectral Interferometry with Electron Microscopes.

    Science.gov (United States)

    Talebi, Nahid

    2016-09-21

    Interference patterns are not only a defining characteristic of waves, but also have several applications; characterization of coherent processes and holography. Spatial holography with electron waves, has paved the way towards space-resolved characterization of magnetic domains and electrostatic potentials with angstrom spatial resolution. Another impetus in electron microscopy has been introduced by ultrafast electron microscopy which uses pulses of sub-picosecond durations for probing a laser induced excitation of the sample. However, attosecond temporal resolution has not yet been reported, merely due to the statistical distribution of arrival times of electrons at the sample, with respect to the laser time reference. This is however, the very time resolution which will be needed for performing time-frequency analysis. These difficulties are addressed here by proposing a new methodology to improve the synchronization between electron and optical excitations through introducing an efficient electron-driven photon source. We use focused transition radiation of the electron as a pump for the sample. Due to the nature of transition radiation, the process is coherent. This technique allows us to perform spectral interferometry with electron microscopes, with applications in retrieving the phase of electron-induced polarizations and reconstructing dynamics of the induced vector potential.

  9. Method of photon spectral analysis

    Science.gov (United States)

    Gehrke, Robert J.; Putnam, Marie H.; Killian, E. Wayne; Helmer, Richard G.; Kynaston, Ronnie L.; Goodwin, Scott G.; Johnson, Larry O.

    1993-01-01

    A spectroscopic method to rapidly measure the presence of plutonium in soils, filters, smears, and glass waste forms by measuring the uranium L-shell x-ray emissions associated with the decay of plutonium. In addition, the technique can simultaneously acquire spectra of samples and automatically analyze them for the amount of americium and .gamma.-ray emitting activation and fission products present. The samples are counted with a large area, thin-window, n-type germanium spectrometer which is equally efficient for the detection of low-energy x-rays (10-2000 keV), as well as high-energy .gamma. rays (>1 MeV). A 8192- or 16,384 channel analyzer is used to acquire the entire photon spectrum at one time. A dual-energy, time-tagged pulser, that is injected into the test input of the preamplifier to monitor the energy scale, and detector resolution. The L x-ray portion of each spectrum is analyzed by a linear-least-squares spectral fitting technique. The .gamma.-ray portion of each spectrum is analyzed by a standard Ge .gamma.-ray analysis program. This method can be applied to any analysis involving x- and .gamma.-ray analysis in one spectrum and is especially useful when interferences in the x-ray region can be identified from the .gamma.-ray analysis and accommodated during the x-ray analysis.

  10. Spectral partitioning in equitable graphs.

    Science.gov (United States)

    Barucca, Paolo

    2017-06-01

    Graph partitioning problems emerge in a wide variety of complex systems, ranging from biology to finance, but can be rigorously analyzed and solved only for a few graph ensembles. Here, an ensemble of equitable graphs, i.e., random graphs with a block-regular structure, is studied, for which analytical results can be obtained. In particular, the spectral density of this ensemble is computed exactly for a modular and bipartite structure. Kesten-McKay's law for random regular graphs is found analytically to apply also for modular and bipartite structures when blocks are homogeneous. An exact solution to graph partitioning for two equal-sized communities is proposed and verified numerically, and a conjecture on the absence of an efficient recovery detectability transition in equitable graphs is suggested. A final discussion summarizes results and outlines their relevance for the solution of graph partitioning problems in other graph ensembles, in particular for the study of detectability thresholds and resolution limits in stochastic block models.

  11. Spectral statistics of 'cellular' billiards

    International Nuclear Information System (INIS)

    Gutkin, Boris

    2011-01-01

    For a bounded domain Ω 0 subset of R 2 whose boundary contains a number of flat pieces Γ i , i = 1, ..., l we consider a family of non-symmetric billiards Ω constructed by patching several copies of Ω 0 along Γ i s. It is demonstrated that the length spectrum of the periodic orbits in Ω is degenerate with the multiplicities determined by a matrix group G. We study the energy spectrum of the corresponding quantum billiard problem in Ω and show that it can be split into a number of uncorrelated subspectra corresponding to a set of irreducible representations α of G. Assuming that the classical dynamics in Ω 0 are chaotic, we derive a semiclassical trace formula for each spectral component and show that their energy level statistics are the same as in standard random matrix ensembles. Depending on whether α is real, pseudo-real or complex, the spectrum has either Gaussian orthogonal, Gaussian symplectic or Gaussian unitary types of statistics, respectively

  12. Protein sequence databases.

    Science.gov (United States)

    Apweiler, Rolf; Bairoch, Amos; Wu, Cathy H

    2004-02-01

    A variety of protein sequence databases exist, ranging from simple sequence repositories, which store data with little or no manual intervention in the creation of the records, to expertly curated universal databases that cover all species and in which the original sequence data are enhanced by the manual addition of further information in each sequence record. As the focus of researchers moves from the genome to the proteins encoded by it, these databases will play an even more important role as central comprehensive resources of protein information. Several the leading protein sequence databases are discussed here, with special emphasis on the databases now provided by the Universal Protein Knowledgebase (UniProt) consortium.

  13. New PN Even Balanced Sequences for Spread-Spectrum Systems

    Directory of Open Access Journals (Sweden)

    Inácio JAL

    2005-01-01

    Full Text Available A new class of pseudonoise even balanced (PN-EB binary spreading sequences is derived from existing classical odd-length families of maximum-length sequences, such as those proposed by Gold, by appending or inserting one extra-zero element (chip to the original sequences. The incentive to generate large families of PN-EB spreading sequences is motivated by analyzing the spreading effect of these sequences from a natural sampling point of view. From this analysis a new definition for PG is established, from which it becomes clear that very high processing gains (PGs can be achieved in band-limited direct-sequence spread-spectrum (DSSS applications by using spreading sequences with zero mean, given that certain conditions regarding spectral aliasing are met. To obtain large families of even balanced (i.e., equal number of ones and zeros sequences, two design criteria are proposed, namely the ranging criterion (RC and the generating ranging criterion (GRC. PN-EB sequences in the polynomial range are derived using these criteria, and it is shown that they exhibit secondary autocorrelation and cross-correlation peaks comparable to the sequences they are derived from. The methods proposed not only facilitate the generation of large numbers of new PN-EB spreading sequences required for CDMA applications, but simultaneously offer high processing gains and good despreading characteristics in multiuser SS scenarios with band-limited noise and interference spectra. Simulation results are presented to confirm the respective claims made.

  14. Spectral characterization of Quillaja saponaria (Mol.

    Directory of Open Access Journals (Sweden)

    T. Acuña

    2016-12-01

    Full Text Available This paper presents a spectral reflectance characterization of the specie Quillaja saponaria (Mol., endemic tree of Chile and valued by society due to its provision of several ecosystem services that gives to society and also for its high concentration of saponins in cortex widely used in the pharmacological industry. For spectral characterization a foliar spectral signatures protocol was designed which included standardized instrumental and environmental parameters. The spectral response of different individuals was measured to evaluate the spectral behaviour and degree of variability within species in the visible and near infrared ranges (VNIR; 400-990 nm with two hyperspectral sensors (ASD HH and camera PDF-65-V10E. The resulting spectral signatures obtained with ASD HH showed a variation less than 5% of reflectance in VNIR and lesser than that in the transition zone from red to near infrared (red-edge; 680-730 nm. Additionally, two distinctive spectral features were detected for the specie, the first is related to a fast increase of reflectance in bands 450-480 nm and the second, to a marked decrease in the 920-970 nm range associated with water absorption features. At branch level, these distinctive features are maintained but with a smaller magnitude of reflectance, which could indicate that they are useful characteristic spectral patterns that can eventually be used for monitoring the physical health state of the specie using remote sensing. On the other hand, we used a PDF-65 camera for study the plant vigour from different health states (healthy, ill, died with spectral vegetation index. The Plant Senescence Reflectance Index detected stress on leaves, and Triangular Vegetation Index allows for a gradually characterization of every state. This work provides the first spectral reference for one of the most important sclerophyll species of Chile.

  15. Real-root property of the spectral polynomial of the Treibich-Verdier potential and related problems

    Science.gov (United States)

    Chen, Zhijie; Kuo, Ting-Jung; Lin, Chang-Shou; Takemura, Kouichi

    2018-04-01

    We study the spectral polynomial of the Treibich-Verdier potential. Such spectral polynomial, which is a generalization of the classical Lamé polynomial, plays fundamental roles in both the finite-gap theory and the ODE theory of Heun's equation. In this paper, we prove that all the roots of such spectral polynomial are real and distinct under some assumptions. The proof uses the classical concept of Sturm sequence and isomonodromic theories. We also prove an analogous result for a polynomial associated with a generalized Lamé equation, where we apply a new approach based on the viewpoint of the monodromy data.

  16. SPECTRAL SMILE CORRECTION IN CRISM HYPERSPECTRAL IMAGES

    Science.gov (United States)

    Ceamanos, X.; Doute, S.

    2009-12-01

    The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) is affected by a common artifact in "push-broom" sensors, the so-called "spectral smile". As a consequence, both central wavelength and spectral width of the spectral response vary along the across-track dimension, thus giving rise to a shifting and smoothing of spectra (see Fig. 1 (left)). In fact, both effects are greater for spectra on the edges, while they are minimum for data acquired by central detectors, the so-called "sweet spot". The prior artifacts become particularly critical for Martian observations which contain steep spectra such as CO2 ice-rich polar images. Fig. 1 (right) shows the horizontal brightness gradient which appears in every band corresponding to a steep portion of spectra. The correction of CRISM spectral smile is addressed using a two-step method which aims at modifying data sensibly in order to mimic the optimal CRISM response. First, all spectra, which are previously interpolated by cubic splines, are resampled to the "sweet spot" wavelengths in order to overcome the spectra shift. Secondly, the non-uniform spectral width is overcome by mimicking an increase of spectral resolution thanks to a spectral sharpening. In order to minimize noise, only bands particularly suffering from smile are selected. First, bands corresponding to the outliers of the Minimum Noise Transformation (MNF) eigenvector, which corresponds to the MNF band related to smile (MNF-smile), are selected. Then, a spectral neighborhood Θi, which takes into account the local spectral convexity or concavity, is defined for every selected band in order to maximize spectral shape preservation. The proposed sharpening technique takes into account both the instrument parameters and the observed spectra. First, every reflectance value belonging to a Θi is reevaluated by a sharpening which depends on a ratio of the spectral width of the current detector and the "sweet spot" one. Then, the optimal degree of

  17. Tailored spiral in-out spectral-spatial water suppression pulses for magnetic resonance spectroscopic imaging.

    Science.gov (United States)

    Ma, Jun; Wismans, Carrie; Cao, Zhipeng; Klomp, Dennis W J; Wijnen, Jannie P; Grissom, William A

    2018-01-01

    To develop short water suppression sequences for 7 T magnetic resonance spectroscopic imaging, with mitigation of subject-specific transmit RF field ( B1+) inhomogeneity. Patient-tailored spiral in-out spectral-spatial saturation pulses were designed for a three-pulse WET water suppression sequence. The pulses' identical spatial subpulses were designed using patient-specific B1+ maps and a spiral in-out excitation k-space trajectory. The subpulse train was weighted by a spectral envelope that was root-flipped to minimize peak RF demand. The pulses were validated in in vivo experiments that acquired high resolution magnetic resonance spectroscopic imaging data, using a crusher coil for fast lipid suppression. Residual water signals and MR spectra were compared between the proposed tailored sequence and a conventional WET sequence. Replacing conventional spectrally-selective pulses with tailored spiral in-out spectral-spatial pulses reduced mean water residual from 5.88 to 2.52% (57% improvement). Pulse design time was less then 0.4 s. The pulses' specific absorption rate were compatible with magnetic resonance spectroscopic imaging TRs under 300 ms, which enabled spectra of fine in plane spatial resolution (5 mm) with good quality to be measured in 7.5 min. Tailored spiral in-out spectral-spatial water suppression enables efficient high resolution magnetic resonance spectroscopic imaging in the brain. Magn Reson Med 79:31-40, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

  18. Spectral theory for a class of periodically perturbed unbounded Jacobi matrices: elementary methods

    CERN Document Server

    Janas, J; Stolz, G

    2003-01-01

    We use elementary methods to give a full characterization of the spectral properties of unbounded Jacobi matrices with zero diagonal and off-diagonal entries of the type $\\lambda_n = n^{\\alpha} + c_n$, where $1/2 < \\alpha \\le 1$ and $c_n$ is a real periodic sequence. The spectral properties depend strongly on the parity of the minimal period of $c_n$. The methods used are asymptotic diagonalization techniques, including the finite difference version of Levinson's theorem, subordinacy theory, and the variational principle.

  19. An experimental applications of impedance measurements by spectral analysis to electrochemistry and corrosion

    International Nuclear Information System (INIS)

    Castro, E.B.; Vilche, J.R.; Milocco, R.H.

    1984-01-01

    An impedance measurement system based on the spectral analysis of excitation and response signals was implemented using a pseudo-random binary sequence in the generation of the electrical perturbation signal. The spectral density functions were estimated through finite Fourier transforms of the original time history records by fast computation of Fourier series. Experimental results obtained using the FFT algorithm in the developed impedance measurement system which covers a wide frequency range, 10 KHz >= f >= 1 mHz, are given both for dummy cells representing conventional electric circuits in electrochemistry and corrosion systems and for the Fe/acidic chloride solution interfaces under different polarization conditions. (C.L.B.) [pt

  20. Spectrally selective solar energy materials

    International Nuclear Information System (INIS)

    Sikkens, M.

    1981-01-01

    The performance and properties of spectrally selective materials are considered and, in particular, the selective absorption of solar radiation by free electrons is discussed, both in a homogeneous material in which these electrons are strongly scattered, and in a composite material consisting of small metal particles in a dielectric host. Such materials can be used as selective absorbers if they are deposited as a thin film onto a metal substrate, the latter providing the required low emittance. This type of selective surfaces is produced by reactive sputtering of Ni in an Ar/CH 4 gas mixture. This method can yield Ni films with a considerable carbon concentration. The carbon concentration can be varied over a wide range by adjusting the partial methane pressure. The associated experimental techniques are discussed. As the carbon concentration increases, the structure of the films changes from a Ni phase in which carbon is dissolved, via an intermediate Ni 3 C phase into an amorphous carbon phase with a high electrical resistivity in which small nickel particles are embedded. Both mechanisms of selective absorption by free electrons are observed and are found to be well described by rather simple models. The best selectivity is obtained at high carbon concentrations where the films consist of nickel particles in carbon. Depending on the film thickness and the substrate material, the solar absorptance varies between 0.78 and 0.90, while the thermal emittance varies between 0.025 and 0.04. Since the films are found to be stable at 400 0 C in vacuum, it appears that these films are good candidates for application in photothermal solar energy conversion at temperature levels around 200 0 C and higher. (Auth.)

  1. Nonlinear spectral imaging of biological tissues

    Science.gov (United States)

    Palero, J. A.

    2007-07-01

    The work presented in this thesis demonstrates live high resolution 3D imaging of tissue in its native state and environment. The nonlinear interaction between focussed femtosecond light pulses and the biological tissue results in the emission of natural autofluorescence and second-harmonic signal. Because biological intrinsic emission is generally very weak and extends from the ultraviolet to the visible spectral range, a broad-spectral range and high sensitivity 3D spectral imaging system is developed. Imaging the spectral characteristics of the biological intrinsic emission reveals the structure and biochemistry of the cells and extra-cellular components. By using different methods in visualizing the spectral images, discrimination between different tissue structures is achieved without the use of any stain or fluorescent label. For instance, RGB real color spectral images of the intrinsic emission of mouse skin tissues show blue cells, green hair follicles, and purple collagen fibers. The color signature of each tissue component is directly related to its characteristic emission spectrum. The results of this study show that skin tissue nonlinear intrinsic emission is mainly due to the autofluorescence of reduced nicotinamide adenine dinucleotide (phosphate), flavins, keratin, melanin, phospholipids, elastin and collagen and nonlinear Raman scattering and second-harmonic generation in Type I collagen. In vivo time-lapse spectral imaging is implemented to study metabolic changes in epidermal cells in tissues. Optical scattering in tissues, a key factor in determining the maximum achievable imaging depth, is also investigated in this work.

  2. Spectral modeling of magnetohydrodynamic turbulent flows.

    Science.gov (United States)

    Baerenzung, J; Politano, H; Ponty, Y; Pouquet, A

    2008-08-01

    We present a dynamical spectral model for large-eddy simulation of the incompressible magnetohydrodynamic (MHD) equations based on the eddy damped quasinormal Markovian approximation. This model extends classical spectral large-eddy simulations for the Navier-Stokes equations to incorporate general (non-Kolmogorovian) spectra as well as eddy noise. We derive the model for MHD flows and show that the introduction of an eddy damping time for the dynamics of spectral tensors, in the absence of equipartition between the velocity and magnetic fields, leads to better agreement with direct numerical simulations, an important point for dynamo computations.

  3. Spectrum-to-Spectrum Searching Using a Proteome-wide Spectral Library*

    Science.gov (United States)

    Yen, Chia-Yu; Houel, Stephane; Ahn, Natalie G.; Old, William M.

    2011-01-01

    The unambiguous assignment of tandem mass spectra (MS/MS) to peptide sequences remains a key unsolved problem in proteomics. Spectral library search strategies have emerged as a promising alternative for peptide identification, in which MS/MS spectra are directly compared against a reference library of confidently assigned spectra. Two problems relate to library size. First, reference spectral libraries are limited to rediscovery of previously identified peptides and are not applicable to new peptides, because of their incomplete coverage of the human proteome. Second, problems arise when searching a spectral library the size of the entire human proteome. We observed that traditional dot product scoring methods do not scale well with spectral library size, showing reduction in sensitivity when library size is increased. We show that this problem can be addressed by optimizing scoring metrics for spectrum-to-spectrum searches with large spectral libraries. MS/MS spectra for the 1.3 million predicted tryptic peptides in the human proteome are simulated using a kinetic fragmentation model (MassAnalyzer version2.1) to create a proteome-wide simulated spectral library. Searches of the simulated library increase MS/MS assignments by 24% compared with Mascot, when using probabilistic and rank based scoring methods. The proteome-wide coverage of the simulated library leads to 11% increase in unique peptide assignments, compared with parallel searches of a reference spectral library. Further improvement is attained when reference spectra and simulated spectra are combined into a hybrid spectral library, yielding 52% increased MS/MS assignments compared with Mascot searches. Our study demonstrates the advantages of using probabilistic and rank based scores to improve performance of spectrum-to-spectrum search strategies. PMID:21532008

  4. Epigenomics: sequencing the methylome.

    Science.gov (United States)

    Hirst, Martin

    2013-01-01

    DNA methylation patterns are increasingly surveyed through methods that utilize massively parallel sequencing. Sequence-based assays developed to detect DNA methylation can be broadly divided into those that depend on affinity enrichment, chemical conversion, or enzymatic restriction. The DNA fragments resulting from these methods are uniformly subjected to library construction and massively parallel sequencing. The sequence reads are subsequently aligned to a reference genome and subjected to specialized analytical tools to extract the underlying methylation signature. This chapter will outline these emerging techniques.

  5. Next-generation sequencing

    DEFF Research Database (Denmark)

    Rieneck, Klaus; Bak, Mads; Jønson, Lars

    2013-01-01

    the feasibility of predicting the fetal KEL1 phenotype using next-generation sequencing (NGS) technology. STUDY DESIGN AND METHODS: The KEL1/2 single-nucleotide polymorphism was polymerase chain reaction (PCR) amplified with one adjoining base, and the PCR product was sequenced using a genome analyzer (GAIIx......, Illumina); several millions of PCR sequences were analyzed. RESULTS: The results demonstrated the feasibility of diagnosing the fetal KEL1 or KEL2 blood group from cell-free DNA purified from maternal plasma. CONCLUSION: This method requires only one primer pair, and the large amount of sequence...

  6. Multi-Configuration Matched Spectral Filter Core Project

    Data.gov (United States)

    National Aeronautics and Space Administration — OPTRA proposes an open-architecture spectral gas sensor based on compressive sensing concepts employed for both spatial and spectral domains. Our matched spectral...

  7. Multi-Configuration Matched Spectral Filter Core, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — OPTRA proposes an open-architecture spectral gas sensor based on compressive sensing concepts employed for both spatial and spectral domains. Our matched spectral...

  8. Spectral Shifting in Nondestructive Assay Instrumentation

    Energy Technology Data Exchange (ETDEWEB)

    Trellue, Holly Renee [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Nettleton, Anthony Steven [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Tutt, James Robert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Menlove, Howard Olsen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); LaFleur, Adrienne Marie [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Tobin, Stephen Joseph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-11-17

    This project involves spectrum tailoring research that endeavors to better distinguish energies of gamma rays using different spectral material thicknesses and determine neutron energies by coating detectors with various materials.

  9. [Hygiene and the spectral energtic light pattern].

    Science.gov (United States)

    Kaptsov, V A; Deynego, V N; SoshMn, N P; Ulasyuk, V N

    There are considered methodological bases of multicriteria synthesis of a spectral energetic pattern for the evaluation of the excessive share of blue and red light in the spectrum of artificial energy sources. The basis of this methodology is relied upon on the hygienic approach to the spectrum analysis of solar and led light. Relying upon on "photobiological paradox of vision" according to M. A. Ostrovsky, conditions of "melanopsin cross" and mechanisms of adverse impact of light on vision, all the spectral-energy characteristics of solar light were divided into subspaces. The border between them became a spectral energy pattern for the evaluation of artificial sources on the security of their impact on eye and human health according to criteria of the excessive dose of blue or red light. On two examples there was shown the effectiveness and clarity of this estimation with the using of the spectral energetic pattern of light.

  10. Spectral properties of supersymmetric shape invariant potentials

    Indian Academy of Sciences (India)

    SIPs). Although the folded spectrum is completely random, unfolded spectrum shows that energy levels are highly correlated and absolutely rigid. All the SIPs exhibit harmonic oscillator-type spectral statistics in the unfolded spectrum.

  11. Salinity and spectral reflectance of soils

    Science.gov (United States)

    Szilagyi, A.; Baumgardner, M. F.

    1991-01-01

    The basic spectral response related to the salt content of soils in the visible and reflective IR wavelengths is analyzed in order to explore remote sensing applications for monitoring processes of the earth system. The bidirectional reflectance factor (BRF) was determined at 10 nm of increments over the 520-2320-nm spectral range. The effect of salts on reflectance was analyzed on the basis of 162 spectral measurements. MSS and TM bands were simulated within the measured spectral region. A strong relationship was found in variations of reflectance and soil characteristics pertaining to salinization and desalinization. Although the individual MSS bands had high R-squared values and 75-79 percent of soil/treatment combinations were separable, there was a large number of soil/treatment combinations not distinguished by any of the four highly correlated MSS bands under consideration.

  12. SSBUV middle ultraviolet solar spectral irradiance measurements

    Science.gov (United States)

    Cebula, Richard P.; Hilsenrath, Ernest

    1994-01-01

    The Shuttle Solar Backscatter Ultraviolet (SSBUV) instrument performs multiple solar spectral irradiance measurements in the wavelength region 200 to 400 nm at 1.1 nm resolution during yearly Space Shuttle flights. Solar spectral irradiance observations from the first three SSBUV Shuttle flights, October 1989, October 1990, and August 1991, are compared with one another and with solar measurements made by the NOAA-11 SBUV/2 instrument. The repeated SSBUV solar spectral observations, which agree to within plus or minus 1-2 percent from 200 to 400 nm, are valuable not only as a means of validating and calibrating the satellite-based solar irradiance measurements, but also as a distinct set of stand-alone solar measurements for monitoring long-term changes in the solar spectral irradiance, which are important for ozone photochemistry.

  13. Broadband Advanced Spectral System, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — NovaSol proposes to develop an advanced hyperspectral imaging system for earth science missions named BRASS (Broadband Advanced Spectral System). BRASS combines...

  14. Algorithms for Spectral Decomposition with Applications

    Data.gov (United States)

    National Aeronautics and Space Administration — The analysis of spectral signals for features that represent physical phenomenon is ubiquitous in the science and engineering communities. There are two main...

  15. Ultra-High Density Spectral Storage Materials

    National Research Council Canada - National Science Library

    Hasan, Zameer U

    2002-01-01

    .... Being atomic scale storage, spectral storage has the potential of providing orders of magnitude denser memories than present day memories that depend on the hulk properties of the storage medium...

  16. Chromosome analysis using spectral karyotyping (SKY).

    Science.gov (United States)

    Imataka, George; Arisaka, Osamu

    2012-01-01

    Spectral karyotyping is a novel technique for chromosome analysis that has been developed based on the approach of the fluorescence in situ hybridization technique. Spectral karyotyping makes it feasible to diagnose a variety of diseases, because of its technology in painting each of the 24 human chromosomes with different colors. In recent years, it has become possible to adopt the usage of spectral karyotyping for research in general clinical practice, and its usability has attracted particular attention in the diagnosis of different diseases. In this review, we will explain the principle of the spectral karyotyping, as well as its specificity and limitation in detecting the genetic defects within clinical application by presenting two case reports.

  17. Computer-assisted spectral design and synthesis

    Science.gov (United States)

    Vadakkumpadan, Fijoy; Wang, Qiqi; Sun, Yinlong

    2005-01-01

    In this paper, we propose a computer-assisted approach for spectral design and synthesis. This approach starts with some initial spectrum, modifies it interactively, evaluates the change, and decides the optimal spectrum. Given a requested change as function of wavelength, we model the change function using a Gaussian function. When there is the metameric constraint, from the Gaussian function of request change, we propose a method to generate the change function such that the result spectrum has the same color as the initial spectrum. We have tested the proposed method with different initial spectra and change functions, and implemented an interactive graphics environment for spectral design and synthesis. The proposed approach and graphics implementation for spectral design and synthesis can be helpful for a number of applications such as lighting of building interiors, textile coloration, and pigment development of automobile paints, and spectral computer graphics.

  18. Spectral properties of almost-periodic Hamiltonians

    International Nuclear Information System (INIS)

    Lima, R.

    1983-12-01

    We give a description of some spectral properties of almost-periodic hamiltonians. We put the stress on some particular points of the proofs of the existence of absolutely continuous or pure point spectrum [fr

  19. HIRES NIMS IDA SPECTRAL IMAGE CUBES

    Data.gov (United States)

    National Aeronautics and Space Administration — This data volume contains 17 channel spectral image cubes of asteroid 243 Ida ranging from 0.7 to 5.2 micrometers in wavelength in cgs units of radiance. These data...

  20. GALILEO NIMS SPECTRAL IMAGE CUBES: JUPITER OPERATIONS

    Data.gov (United States)

    National Aeronautics and Space Administration — The natural form of imaging spectrometer data is the spectral image cube. It is normally in band sequential format, but has a dual nature. It is a series of 'images'...

  1. GALILEO NIMS SPECTRAL IMAGE TUBES: JUPITER OPERATIONS

    Data.gov (United States)

    National Aeronautics and Space Administration — The natural form of imaging spectrometer data is the spectral image cube. It is normally in band sequential format, but has a dual nature. It is a series of 'images'...

  2. Learning theory of distributed spectral algorithms

    Science.gov (United States)

    Guo, Zheng-Chu; Lin, Shao-Bo; Zhou, Ding-Xuan

    2017-07-01

    Spectral algorithms have been widely used and studied in learning theory and inverse problems. This paper is concerned with distributed spectral algorithms, for handling big data, based on a divide-and-conquer approach. We present a learning theory for these distributed kernel-based learning algorithms in a regression framework including nice error bounds and optimal minimax learning rates achieved by means of a novel integral operator approach and a second order decomposition of inverse operators. Our quantitative estimates are given in terms of regularity of the regression function, effective dimension of the reproducing kernel Hilbert space, and qualification of the filter function of the spectral algorithm. They do not need any eigenfunction or noise conditions and are better than the existing results even for the classical family of spectral algorithms.

  3. Matched Spectral Filter Imager, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — OPTRA proposes the development of an imaging spectrometer for greenhouse gas and volcanic gas imaging based on matched spectral filtering and compressive imaging....

  4. Precise Multi-Spectral Dermatological Imaging

    DEFF Research Database (Denmark)

    Gomez, David Delgado; Carstensen, Jens Michael; Ersbøll, Bjarne Kjær

    2004-01-01

    In this work, an integrated imaging system to obtain accurate and reproducible multi-spectral dermatological images is proposed. The system is made up of an integrating sphere, light emitting diodes and a generic monochromatic camera. The system can collect up to 10 different spectral bands....... These spectral bands vary from ultraviolet to near infrared. The welldefined and diffuse illumination of the optically closed scene aims to avoid shadows and specular reflections. Furthermore, the system has been developed to guarantee the reproducibility of the collected images. This allows for comparative...... studies of time series of images. Two experiments are conducted to show the ability of the system to acquire highly precise and standardized multi-spectral images. The first experiment aims to show the capacity of the system to collect reproducible images. The second experiment demonstrates that the multi...

  5. Learning theory of distributed spectral algorithms

    International Nuclear Information System (INIS)

    Guo, Zheng-Chu; Lin, Shao-Bo; Zhou, Ding-Xuan

    2017-01-01

    Spectral algorithms have been widely used and studied in learning theory and inverse problems. This paper is concerned with distributed spectral algorithms, for handling big data, based on a divide-and-conquer approach. We present a learning theory for these distributed kernel-based learning algorithms in a regression framework including nice error bounds and optimal minimax learning rates achieved by means of a novel integral operator approach and a second order decomposition of inverse operators. Our quantitative estimates are given in terms of regularity of the regression function, effective dimension of the reproducing kernel Hilbert space, and qualification of the filter function of the spectral algorithm. They do not need any eigenfunction or noise conditions and are better than the existing results even for the classical family of spectral algorithms. (paper)

  6. Spectral properties of 441 radio pulsars

    Science.gov (United States)

    Jankowski, F.; van Straten, W.; Keane, E. F.; Bailes, M.; Barr, E. D.; Johnston, S.; Kerr, M.

    2018-02-01

    We present a study of the spectral properties of 441 pulsars observed with the Parkes radio telescope near the centre frequencies of 728, 1382 and 3100 MHz. The observations at 728 and 3100 MHz were conducted simultaneously using the dual-band 10-50 cm receiver. These high-sensitivity, multifrequency observations provide a systematic and uniform sample of pulsar flux densities. We combine our measurements with spectral data from the literature in order to derive the spectral properties of these pulsars. Using techniques from robust regression and information theory, we classify the observed spectra in an objective, robust and unbiased way into five morphological classes: simple or broken power law, power law with either low- or high-frequency cut-off and log-parabolic spectrum. While about 79 per cent of the pulsars that could be classified have simple power-law spectra, we find significant deviations in 73 pulsars, 35 of which have curved spectra, 25 with a spectral break and 10 with a low-frequency turn-over. We identify 11 gigahertz-peaked spectrum (GPS) pulsars, with 3 newly identified in this work and 8 confirmations of known GPS pulsars; 3 others show tentative evidence of GPS, but require further low-frequency measurements to support this classification. The weighted mean spectral index of all pulsars with simple power-law spectra is -1.60 ± 0.03. The observed spectral indices are well described by a shifted log-normal distribution. The strongest correlations of spectral index are with spin-down luminosity, magnetic field at the light-cylinder and spin-down rate. We also investigate the physical origin of the observed spectral features and determine emission altitudes for three pulsars.

  7. Spectral Feature Selection for Data Mining

    CERN Document Server

    Zhao, Zheng Alan

    2011-01-01

    Spectral Feature Selection for Data Mining introduces a novel feature selection technique that establishes a general platform for studying existing feature selection algorithms and developing new algorithms for emerging problems in real-world applications. This technique represents a unified framework for supervised, unsupervised, and semisupervised feature selection. The book explores the latest research achievements, sheds light on new research directions, and stimulates readers to make the next creative breakthroughs. It presents the intrinsic ideas behind spectral feature selection, its th

  8. Measuring Collimator Infrared (IR) Spectral Transmission

    Science.gov (United States)

    2016-05-01

    TECHNICAL REPORT RDMR-WD-16-15 MEASURING COLLIMATOR INFRARED ( IR ) SPECTRAL TRANSMISSION Christopher L. Dobbins Weapons...AND DATES COVERED Final 4. TITLE AND SUBTITLE Measuring Collimator Infrared ( IR ) Spectral Transmission 5. FUNDING NUMBERS 6. AUTHOR(S) Christopher L...release; distribution is unlimited. 12b. DISTRIBUTION CODE A 13. ABSTRACT (Maximum 200 Words) Several Infrared ( IR ) imaging systems have been measured

  9. Biomimetic joint spatial-spectral pattern recognition

    Science.gov (United States)

    Caulfield, H. John

    2003-08-01

    Most animals use color and shape to recognize things in their worlds. Shapes are properties of objects inferable from their 2D images. Colors are spectral discriminants computed by their brains using data sensed in 2-4 broad, spectrally overlapping bands. So color is not an object property. Both shape and color combine to make discrimination work well. I will describe Artificial Color and then ways to recognize an Artificially colored image.

  10. A high throughput spectral image microscopy system

    Science.gov (United States)

    Gesley, M.; Puri, R.

    2018-01-01

    A high throughput spectral image microscopy system is configured for rapid detection of rare cells in large populations. To overcome flow cytometry rates and use of fluorophore tags, a system architecture integrates sample mechanical handling, signal processors, and optics in a non-confocal version of light absorption and scattering spectroscopic microscopy. Spectral images with native contrast do not require the use of exogeneous stain to render cells with submicron resolution. Structure may be characterized without restriction to cell clusters of differentiation.

  11. Spectral evolution of galaxies: current views

    International Nuclear Information System (INIS)

    Bruzual, A.G.

    1985-01-01

    A summary of current views on the interpretation of the various evolutionary tests aimed at detecting spectral evolution in galaxies is presented. It is concluded that the evolution taking place in known galaxy samples is a slow process (perhaps consistent with no evolution at all), and that the early phases of rapid spectral evolution in early-type galaxies have not yet been detected. (author)

  12. Panchromatic spectral energy distributions of Herschel sources

    Science.gov (United States)

    Berta, S.; Lutz, D.; Santini, P.; Wuyts, S.; Rosario, D.; Brisbin, D.; Cooray, A.; Franceschini, A.; Gruppioni, C.; Hatziminaoglou, E.; Hwang, H. S.; Le Floc'h, E.; Magnelli, B.; Nordon, R.; Oliver, S.; Page, M. J.; Popesso, P.; Pozzetti, L.; Pozzi, F.; Riguccini, L.; Rodighiero, G.; Roseboom, I.; Scott, D.; Symeonidis, M.; Valtchanov, I.; Viero, M.; Wang, L.

    2013-03-01

    Combining far-infrared Herschel photometry from the PACS Evolutionary Probe (PEP) and Herschel Multi-tiered Extragalactic Survey (HerMES) guaranteed time programs with ancillary datasets in the GOODS-N, GOODS-S, and COSMOS fields, it is possible to sample the 8-500 μm spectral energy distributions (SEDs) of galaxies with at least 7-10 bands. Extending to the UV, optical, and near-infrared, the number of bands increases up to 43. We reproduce the distribution of galaxies in a carefully selected restframe ten colors space, based on this rich data-set, using a superposition of multivariate Gaussian modes. We use this model to classify galaxies and build median SEDs of each class, which are then fitted with a modified version of the magphys code that combines stellar light, emission from dust heated by stars and a possible warm dust contribution heated by an active galactic nucleus (AGN). The color distribution of galaxies in each of the considered fields can be well described with the combination of 6-9 classes, spanning a large range of far- to near-infrared luminosity ratios, as well as different strength of the AGN contribution to bolometric luminosities. The defined Gaussian grouping is used to identify rare or odd sources. The zoology of outliers includes Herschel-detected ellipticals, very blue z ~ 1 Ly-break galaxies, quiescent spirals, and torus-dominated AGN with star formation. Out of these groups and outliers, a new template library is assembled, consisting of 32 SEDs describing the intrinsic scatter in the restframe UV-to-submm colors of infrared galaxies. This library is tested against L(IR) estimates with and without Herschel data included, and compared to eightother popular methods often adopted in the literature. When implementing Herschel photometry, these approaches produce L(IR) values consistent with each other within a median absolute deviation of 10-20%, the scatter being dominated more by fine tuning of the codes, rather than by the choice of

  13. Can spectral-spatial image segmentation be used to discriminate experimental burn wounds?

    Science.gov (United States)

    Paluchowski, Lukasz A.; Nordgaard, Håvard B.; Bjorgan, Asgeir; Hov, Håkon; Berget, Sissel M.; Randeberg, Lise L.

    2016-10-01

    Hyperspectral imaging (HSI) is a noncontact and noninvasive optical modality emerging the field of medical research. The goal of this study was to determine the ability of HSI and image segmentation to discriminate burn wounds in a preclinical porcine model. A heated brass rod was used to introduce burn wounds of graded severity in a pig model and a sequence of hyperspectral data was recorded up to 8-h postinjury. The hyperspectral images were processed by an unsupervised spectral-spatial segmentation algorithm. Segmentation was validated using results from histology. The proposed algorithm was compared to K-means segmentation and was found superior. The obtained segmentation maps revealed separated zones within the burn sites, indicating a variation in burn severity. The suggested image-processing scheme allowed mapping dynamic changes of spectral properties within the burn wounds over time. The results of this study indicate that unsupervised spectral-spatial segmentation applied on hyperspectral images can discriminate burn injuries of varying severity.

  14. Semi-supervised spectral clustering with application to detect population stratification

    Directory of Open Access Journals (Sweden)

    Binghui eLiu

    2013-10-01

    Full Text Available In genetic association studies, unaccounted population stratification can cause spurious associations in a discovery process of identifying disease-associated genetic markers. In such a situation, prior information is often available for some subjects' population identities. To leverage the additional information, we propose a semi-supervised clustering approach for detecting population stratification. This approach maintains the advantages of spectral clustering, while is integrated with the additional identity information, leading to sharper clustering performance. To demonstrate utility of our approach, we analyze a whole-genome sequencing dataset from the 1000 Genomes Project, consisting of the genotypes of 607 individuals sampled from three continental groups involving 10 subpopulations. This is compared against a semi-supervised spectral clustering method, in addition to a spectral clustering method, with the known subpopulation information by the Rand index and an adjusted Rand (ARand index. The numerical results suggest that the proposed method outperforms its competitors in detecting population stratification.

  15. Delayed Sequence Intubation

    DEFF Research Database (Denmark)

    Weingart, Scott D; Trueger, N Seth; Wong, Nelson

    2015-01-01

    assessed. RESULTS: A total of 62 patients were enrolled: 19 patients required delayed sequence intubation to allow nonrebreather mask, 39 patients required it to allow NIPPV, and 4 patients required it for nasogastric tube placement. Saturations increased from a mean of 89.9% before delayed sequence...

  16. Cosmetology: Scope and Sequence.

    Science.gov (United States)

    Nashville - Davidson County Metropolitan Public Schools, TN.

    This scope and sequence guide, developed for a cosmetology vocational education program, represents an initial step in the development of a systemwide articulated curriculum sequence for all vocational programs within the Metropolitan Nashville Public School System. It was developed as a result of needs expressed by teachers, parents, and the…

  17. Sequences for Student Investigation

    Science.gov (United States)

    Barton, Jeffrey; Feil, David; Lartigue, David; Mullins, Bernadette

    2004-01-01

    We describe two classes of sequences that give rise to accessible problems for undergraduate research. These problems may be understood with virtually no prerequisites and are well suited for computer-aided investigation. The first sequence is a variation of one introduced by Stephen Wolfram in connection with his study of cellular automata. The…

  18. The Effect of Field Spectral Reflectance Measurement Distance to the Spectral Reflectance of Rhizophora stylosa

    Science.gov (United States)

    Kamal, M.; Ningam, M. U. L.; Alqorina, F.

    2017-12-01

    Mapping mangrove species from remote sensing data through its spectral reflectance pattern collected in the field is challenging. There are high variations in light condition, leaf orientation, canopy structure, background objects and measurement distance when measuring mangrove spectral reflectance in the field. Spectral measurement distance to the object is one of the most important aspects controlling the result of spectral reflectance pattern. This research is aimed to assess the effect of spectral reflectance pattern of Rhizophora stylosa collected at various distances. Specific objectives of this research are to collect samples of mangrove spectral reflectance pattern in the field, to assess the effect of the observation scale to the result of the spectral reflectance pattern, and to characterize the mangrove spectral reflectance pattern resulted from different observation scales. Spectral reflectance data collection in the field was conducted using JAZ EL-350 field spectrometer at 2cm, 50cm, 1m, 2m, and 5m distance and was conducted in Karimunjawa Island, Jepara, Central Java, Indonesia. A visual comparison of the spectral reflectance curve was conducted to understand the effect of measurement distance. The results of this study indicate that the difference in the measurement distance of Rhizophora stylosa species was highly influential to the resulting spectral reflectance curve. The spectral reflectance curve recorded at close range to the leaf (i.e. 2 cm) has the lowest curve variation, as well as the furthest distance (i.e. 5 m). This study is a basic study that supports the development of the use of remote sensing imagery for mangrove species mapping.

  19. Deriving the Contribution of Blazars to the Fermi-LAT Extragalactic γ-ray Background at E > 10 GeV with Efficiency Corrections and Photon Statistics

    Science.gov (United States)

    Di Mauro, M.; Manconi, S.; Zechlin, H.-S.; Ajello, M.; Charles, E.; Donato, F.

    2018-04-01

    The Fermi Large Area Telescope (LAT) Collaboration has recently released the Third Catalog of Hard Fermi-LAT Sources (3FHL), which contains 1556 sources detected above 10 GeV with seven years of Pass 8 data. Building upon the 3FHL results, we investigate the flux distribution of sources at high Galactic latitudes (| b| > 20^\\circ ), which are mostly blazars. We use two complementary techniques: (1) a source-detection efficiency correction method and (2) an analysis of pixel photon count statistics with the one-point probability distribution function (1pPDF). With the first method, using realistic Monte Carlo simulations of the γ-ray sky, we calculate the efficiency of the LAT to detect point sources. This enables us to find the intrinsic source-count distribution at photon fluxes down to 7.5 × 10‑12 ph cm‑2 s‑1. With this method, we detect a flux break at (3.5 ± 0.4) × 10‑11 ph cm‑2 s‑1 with a significance of at least 5.4σ. The power-law indexes of the source-count distribution above and below the break are 2.09 ± 0.04 and 1.07 ± 0.27, respectively. This result is confirmed with the 1pPDF method, which has a sensitivity reach of ∼10‑11 ph cm‑2 s‑1. Integrating the derived source-count distribution above the sensitivity of our analysis, we find that (42 ± 8)% of the extragalactic γ-ray background originates from blazars.

  20. Spectral measurements from laser-produced plasma in OMEGA

    Science.gov (United States)

    Burkhalter, P. G.; Newman, D. A.; Rosen, D. L.; Hudson, K.; Richardson, M.; Audebert, P.

    1986-08-01

    Curved- and flat-diffraction crystal spectrographs were developed to collect x-ray spectra from high-atomic-number elements (cadmium-rare earths) in the 5-17-Å region. The plasma source was generated by the 24-beam, frequency-tripled light of the OMEGA laser system. The spectral patterns were identified with the aid of atomic structure calculations and from Moseley plots of isoelectronic sequences. The Ne-like (third-order diffraction) and Na-like ionization stages were observed in the Cd and Sn spectra. The rare-earth spectra were predominantly 3d-4p, 4f transitions over a range of ionization stages involving the M shell. Calibration spectra were obtained with L-series transitions from Fe and Cu targets and K lines from Si plasma excited in the glass supporting stalk.

  1. Sequence History Update Tool

    Science.gov (United States)

    Khanampompan, Teerapat; Gladden, Roy; Fisher, Forest; DelGuercio, Chris

    2008-01-01

    The Sequence History Update Tool performs Web-based sequence statistics archiving for Mars Reconnaissance Orbiter (MRO). Using a single UNIX command, the software takes advantage of sequencing conventions to automatically extract the needed statistics from multiple files. This information is then used to populate a PHP database, which is then seamlessly formatted into a dynamic Web page. This tool replaces a previous tedious and error-prone process of manually editing HTML code to construct a Web-based table. Because the tool manages all of the statistics gathering and file delivery to and from multiple data sources spread across multiple servers, there is also a considerable time and effort savings. With the use of The Sequence History Update Tool what previously took minutes is now done in less than 30 seconds, and now provides a more accurate archival record of the sequence commanding for MRO.

  2. Spectral fingerprints of Earth-like planets around FGK stars.

    Science.gov (United States)

    Rugheimer, Sarah; Kaltenegger, Lisa; Zsom, Andras; Segura, Antígona; Sasselov, Dimitar

    2013-03-01

    We present model atmospheres for an Earth-like planet orbiting the entire grid of main sequence FGK stars with effective temperatures ranging from Teff=4250 K to Teff=7000 K in 250 K intervals. We have modeled the remotely detectable spectra of Earth-like planets for clear and cloudy atmospheres at the 1 AU equivalent distance from the VIS to IR (0.4 to 20 μm) to compare detectability of features in different wavelength ranges in accordance with the James Webb Space Telescope and future design concepts to characterize exo-Earths. We have also explored the effect of the stellar UV levels as well as spectral energy distribution on a terrestrial atmosphere, concentrating on detectable atmospheric features that indicate habitability on Earth, namely, H2O, O3, CH4, N2O, and CH3Cl. The increase in UV dominates changes of O3, OH, CH4, N2O, and CH3Cl, whereas the increase in stellar temperature dominates changes in H2O. The overall effect as stellar effective temperatures and corresponding UV increase is a lower surface temperature of the planet due to a bigger part of the stellar flux being reflected at short wavelengths, as well as increased photolysis. Earth-like atmosphere models show more O3 and OH but less stratospheric CH4, N2O, CH3Cl, and tropospheric H2O (but more stratospheric H2O) with increasing effective temperature of main sequence stars. The corresponding detectable spectral features, on the other hand, show different detectability depending on the wavelength observed. We concentrate on directly imaged planets here as a framework to interpret future light curves, direct imaging, and secondary eclipse measurements of atmospheres of terrestrial planets in the habitable zone at varying orbital positions.

  3. USGS Digital Spectral Library splib06a

    Science.gov (United States)

    Clark, Roger N.; Swayze, Gregg A.; Wise, Richard A.; Livo, K. Eric; Hoefen, Todd M.; Kokaly, Raymond F.; Sutley, Stephen J.

    2007-01-01

    Introduction We have assembled a digital reflectance spectral library that covers the wavelength range from the ultraviolet to far infrared along with sample documentation. The library includes samples of minerals, rocks, soils, physically constructed as well as mathematically computed mixtures, plants, vegetation communities, microorganisms, and man-made materials. The samples and spectra collected were assembled for the purpose of using spectral features for the remote detection of these and similar materials. Analysis of spectroscopic data from laboratory, aircraft, and spacecraft instrumentation requires a knowledge base. The spectral library discussed here forms a knowledge base for the spectroscopy of minerals and related materials of importance to a variety of research programs being conducted at the U.S. Geological Survey. Much of this library grew out of the need for spectra to support imaging spectroscopy studies of the Earth and planets. Imaging spectrometers, such as the National Aeronautics and Space Administration (NASA) Airborne Visible/Infra Red Imaging Spectrometer (AVIRIS) or the NASA Cassini Visual and Infrared Mapping Spectrometer (VIMS) which is currently orbiting Saturn, have narrow bandwidths in many contiguous spectral channels that permit accurate definition of absorption features in spectra from a variety of materials. Identification of materials from such data requires a comprehensive spectral library of minerals, vegetation, man-made materials, and other subjects in the scene. Our research involves the use of the spectral library to identify the components in a spectrum of an unknown. Therefore, the quality of the library must be very good. However, the quality required in a spectral library to successfully perform an investigation depends on the scientific questions to be answered and the type of algorithms to be used. For example, to map a mineral using imaging spectroscopy and the mapping algorithm of Clark and others (1990a, 2003b

  4. Solar spectral irradiance changes during cycle 24

    Energy Technology Data Exchange (ETDEWEB)

    Marchenko, S. V.; DeLand, M. T. [Also at NASA/Goddard Space Flight Center, Greenbelt, MD, USA. (United States)

    2014-07-10

    We use solar spectra obtained by the Ozone Monitoring Instrument (OMI) on board the Aura satellite to detect and follow long-term (years) and short-term (weeks) changes in the solar spectral irradiance (SSI) in the 265-500 nm spectral range. During solar Cycle 24, in the relatively line-free regions the SSI changed by ∼0.6% ± 0.2% around 265 nm. These changes gradually diminish to 0.15% ± 0.20% at 500 nm. All strong spectral lines and blends, with the notable exception of the upper Balmer lines, vary in unison with the solar 'continuum'. Besides the lines with strong chromospheric components, the most involved species include Fe I blends and all prominent CH, NH, and CN spectral bands. Following the general trend seen in the solar 'continuum', the variability of spectral lines also decreases toward longer wavelengths. The long-term solar cycle SSI changes are closely, to within the quoted 0.1%-0.2% uncertainties, matched by the appropriately adjusted short-term SSI variations derived from the 27 day rotational modulation cycles. This further strengthens and broadens the prevailing notion about the general scalability of the UV SSI variability to the emissivity changes in the Mg II 280 nm doublet on timescales from weeks to years. We also detect subtle deviations from this general rule: the prominent spectral lines and blends at λ ≳ 350 nm show slightly more pronounced 27 day SSI changes when compared to the long-term (years) trends. We merge the solar data from Cycle 21 with the current Cycle 24 OMI and GOME-2 observations and provide normalized SSI variations for the 170-795 nm spectral region.

  5. HIV Sequence Compendium 2015

    Energy Technology Data Exchange (ETDEWEB)

    Foley, Brian Thomas [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Leitner, Thomas Kenneth [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Apetrei, Cristian [Univ. of Pittsburgh, PA (United States); Hahn, Beatrice [Univ. of Pennsylvania, Philadelphia, PA (United States); Mizrachi, Ilene [National Center for Biotechnology Information, Bethesda, MD (United States); Mullins, James [Univ. of Washington, Seattle, WA (United States); Rambaut, Andrew [Univ. of Edinburgh, Scotland (United Kingdom); Wolinsky, Steven [Northwestern Univ., Evanston, IL (United States); Korber, Bette Tina Marie [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-10-05

    This compendium is an annual printed summary of the data contained in the HIV sequence database. We try to present a judicious selection of the data in such a way that it is of maximum utility to HIV researchers. Each of the alignments attempts to display the genetic variability within the different species, groups and subtypes of the virus. This compendium contains sequences published before January 1, 2015. Hence, though it is published in 2015 and called the 2015 Compendium, its contents correspond to the 2014 curated alignments on our website. The number of sequences in the HIV database is still increasing. In total, at the end of 2014, there were 624,121 sequences in the HIV Sequence Database, an increase of 7% since the previous year. This is the first year that the number of new sequences added to the database has decreased compared to the previous year. The number of near complete genomes (>7000 nucleotides) increased to 5834 by end of 2014. However, as in previous years, the compendium alignments contain only a fraction of these. A more complete version of all alignments is available on our website, http://www.hiv.lanl.gov/ content/sequence/NEWALIGN/align.html As always, we are open to complaints and suggestions for improvement. Inquiries and comments regarding the compendium should be addressed to seq-info@lanl.gov.

  6. Evolution of DNA sequencing.

    Science.gov (United States)

    Tipu, Hamid Nawaz; Shabbir, Ambreen

    2015-03-01

    Sanger and coworkers introduced DNA sequencing in 1970s for the first time. It principally relied on termination of growing nucleotide chain when a dideoxythymidine triphosphate (ddTTP) was inserted in it. Detection of terminated sequences was done radiographically on Polyacrylamide Gel Electrophoresis (PAGE). Improvements that have evolved over time in original Sanger sequencing include replacement of radiography with fluorescence, use of separate fluorescent markers for each nucleotide, use of capillary electrophoresis instead of polyacrylamide gel electrophoresis and then introduction of capillary array electrophoresis. However, this technique suffered from few inherent limitations like decreased sensitivity for low level mutant alleles, complexities in analyzing highly polymorphic regions like Major Histocompatibility Complex (MHC) and high DNA concentrations required. Several Next Generation Sequencing (NGS) technologies have been introduced by Roche, Illumina and other commercial manufacturers that tend to overcome Sanger sequencing limitations and have been reviewed. Introduction of NGS in clinical research and medical diagnostics is expected to change entire diagnostic approach. These include study of cancer variants, detection of minimal residual disease, exome sequencing, detection of Single Nucleotide Polymorphisms (SNPs) and their disease association, epigenetic regulation of gene expression and sequencing of microorganisms genome.

  7. The Colliding Beams Sequencer

    International Nuclear Information System (INIS)

    Johnson, D.E.; Johnson, R.P.

    1989-01-01

    The Colliding Beam Sequencer (CBS) is a computer program used to operate the pbar-p Collider by synchronizing the applications programs and simulating the activities of the accelerator operators during filling and storage. The Sequencer acts as a meta-program, running otherwise stand alone applications programs, to do the set-up, beam transfers, acceleration, low beta turn on, and diagnostics for the transfers and storage. The Sequencer and its operational performance will be described along with its special features which include a periodic scheduler and command logger. 14 refs., 3 figs

  8. Phylogenetic Trees From Sequences

    Science.gov (United States)

    Ryvkin, Paul; Wang, Li-San

    In this chapter, we review important concepts and approaches for phylogeny reconstruction from sequence data.We first cover some basic definitions and properties of phylogenetics, and briefly explain how scientists model sequence evolution and measure sequence divergence. We then discuss three major approaches for phylogenetic reconstruction: distance-based phylogenetic reconstruction, maximum parsimony, and maximum likelihood. In the third part of the chapter, we review how multiple phylogenies are compared by consensus methods and how to assess confidence using bootstrapping. At the end of the chapter are two sections that list popular software packages and additional reading.

  9. a Variable Resolution Global Spectral Model.

    Science.gov (United States)

    Hardiker, Vivek Manohar

    A conformal transformation suggested by F. Schimdt is followed to implement a global spectral model with variable horizontal resolution. A conformal mapping is defined between the real physical sphere (Earth) to a transformed (Computational) sphere. The model equations are discretized on the computational sphere and the conventional spectral technique is applied to solve the model equations. There are two types of transformations used in the present study, namely, the Stretching transformation and the Rotation of the horizontal grid points. Application of the stretching transformation results in finer resolution along the meridional direction. The stretching is controlled by a parameter C. The rotation transformation can be used to relocate the North Pole of the model to any point on the geographic sphere. The idea is now to rotate the pole to the area of interest and refine the resolution around the new pole by applying the stretching transformation. The stretching transformation can be applied alone without the rotation. A T-42 Spectral Shallow-Water model is transformed by applying the stretching transformation alone as well as the two transformations together. A T-42 conventional Spectral Shallow-Water model is run as the control experiment and a conventional T-85 Spectral Shallow-Water model run is treated as the benchmark (Truth) solution. RMS error analysis for the geopotential field as well as the wind field is performed to evaluate the forecast made by the transformed model. It is observed that the RMS error of the transformed model is lower than that of the control run in a latitude band, for the case of stretching transformation alone, while for the total transformation (rotation followed by stretching), similar results are obtained for a rectangular domain. A multi-level global spectral model is designed from the current FSU global spectral model in order to implement the conformal transformation. The transformed T-85 model is used to study Hurricane

  10. Schrodinger Eigenmaps for spectral target detection

    Science.gov (United States)

    Dorado-Munoz, Leidy P.; Messinger, David W.

    2015-05-01

    Spectral imagery such as multispectral and hyperspectral data could be seen as a set of panchromatic images stacked as a 3d cube, with two spatial dimensions and one spectral. For hyperspectral imagery, the spectral dimension is highly sampled, which implies redundant information and a high spectral dimensionality. Therefore, it is necessary to use transformations on the data not only to reduce processing costs, but also to reveal some features or characteristics of the data that were hidden in the original space. Schrodinger Eigenmaps (SE) is a novel mathematical method for non-linear representation of a data set that attempts to preserve the local structure while the spectral dimension is reduced. SE could be seen as an extension of Laplacian Eigenmaps (LE), where the diffusion process could be steered in certain directions determined by a potential term. SE was initially introduced as a semi supervised classification technique and most recently, it has been applied to target detection showing promising performance. In target detection, only the barrier potential has been used, so different forms to define barrier potentials and its influence on the data embedding are studied here. In this way, an experiment to assess the target detection vs. how strong the influence of potentials is and how many eigenmaps are used in the detection, is proposed. The target detection is performed using a hyperspectral data set, where several targets with different complexity are presented in the same scene.

  11. Efficient uncertainty minimization for fuzzy spectral clustering.

    Science.gov (United States)

    White, Brian S; Shalloway, David

    2009-11-01

    Spectral clustering uses the global information embedded in eigenvectors of an inter-item similarity matrix to correctly identify clusters of irregular shape, an ability lacking in commonly used approaches such as k -means and agglomerative clustering. However, traditional spectral clustering partitions items into hard clusters, and the ability to instead generate fuzzy item assignments would be advantageous for the growing class of domains in which cluster overlap and uncertainty are important. Korenblum and Shalloway [Phys. Rev. E 67, 056704 (2003)] extended spectral clustering to fuzzy clustering by introducing the principle of uncertainty minimization. However, this posed a challenging nonconvex global optimization problem that they solved by a brute-force technique unlikely to scale to data sets having more than O(10;{2}) items. Here we develop a method for solving the minimization problem, which can handle data sets at least two orders of magnitude larger. In doing so, we elucidate the underlying structure of uncertainty minimization using multiple geometric representations. This enables us to show how fuzzy spectral clustering using uncertainty minimization is related to and generalizes clustering motivated by perturbative analysis of almost-block-diagonal matrices. Uncertainty minimization can be applied to a wide variety of existing hard spectral clustering approaches, thus transforming them to fuzzy methods.

  12. Spectral line polarimetry with a channeled polarimeter.

    Science.gov (United States)

    van Harten, Gerard; Snik, Frans; Rietjens, Jeroen H H; Martijn Smit, J; Keller, Christoph U

    2014-07-01

    Channeled spectropolarimetry or spectral polarization modulation is an accurate technique for measuring the continuum polarization in one shot with no moving parts. We show how a dual-beam implementation also enables spectral line polarimetry at the intrinsic resolution, as in a classic beam-splitting polarimeter. Recording redundant polarization information in the two spectrally modulated beams of a polarizing beam-splitter even provides the possibility to perform a postfacto differential transmission correction that improves the accuracy of the spectral line polarimetry. We perform an error analysis to compare the accuracy of spectral line polarimetry to continuum polarimetry, degraded by a residual dark signal and differential transmission, as well as to quantify the impact of the transmission correction. We demonstrate the new techniques with a blue sky polarization measurement around the oxygen A absorption band using the groundSPEX instrument, yielding a polarization in the deepest part of the band of 0.160±0.010, significantly different from the polarization in the continuum of 0.2284±0.0004. The presented methods are applicable to any dual-beam channeled polarimeter, including implementations for snapshot imaging polarimetry.

  13. Spectrally selective imaging with wideband balanced steady-state free precession MRI.

    Science.gov (United States)

    Çukur, Tolga

    2016-03-01

    Unwanted, bright fat signals in balanced steady-state free precession sequences are commonly suppressed using spectral shaping. Here, a new spectral-shaping method is proposed to significantly improve the uniformity of stopband suppression without compromising the level of passband signals. The proposed method combines binomial-pattern excitation pulses with a wideband balanced steady-state free precession sequence kernel. It thereby increases the frequency separation between the centers of pass and stopbands by π radians, enabling improved water-fat contrast. Simulations were performed to find the optimal flip angles and subpulse spacing for the binomial pulses that maximize contrast and signal efficiency. Comparisons with a conventional binomial balanced steady-state free precession sequence were performed in simulations as well as phantom and in vivo experiments at 1.5 T and 3 T. Enhanced fat suppression is demonstrated in vivo with an average improvement of 58% in blood-fat and 68% in muscle-fat contrast (P steady-state free precession method is a promising candidate for spectrally selective imaging with enhanced reliability against field inhomogeneities. © 2015 Wiley Periodicals, Inc.

  14. Stress Drops for Potentially Induced Earthquake Sequences

    Science.gov (United States)

    Huang, Y.; Beroza, G. C.; Ellsworth, W. L.

    2015-12-01

    Stress drop, the difference between shear stress acting across a fault before and after an earthquake, is a fundamental parameter of the earthquake source process and the generation of strong ground motions. Higher stress drops usually lead to more high-frequency ground motions. Hough [2014 and 2015] observed low intensities in "Did You Feel It?" data for injection-induced earthquakes, and interpreted them to be a result of low stress drops. It is also possible that the low recorded intensities could be a result of propagation effects. Atkinson et al. [2015] show that the shallow depth of injection-induced earthquakes can lead to a lack of high-frequency ground motion as well. We apply the spectral ratio method of Imanishi and Ellsworth [2006] to analyze stress drops of injection-induced earthquakes, using smaller earthquakes with similar waveforms as empirical Green's functions (eGfs). Both the effects of path and linear site response should be cancelled out through the spectral ratio analysis. We apply this technique to the Guy-Greenbrier earthquake sequence in central Arkansas. The earthquakes migrated along the Guy-Greenbrier Fault while nearby injection wells were operating in 2010-2011. Huang and Beroza [GRL, 2015] improved the magnitude of completeness to about -1 using template matching and found that the earthquakes deviated from Gutenberg-Richter statistics during the operation of nearby injection wells. We identify 49 clusters of highly similar events in the Huang and Beroza [2015] catalog and calculate stress drops using the source model described in Imanishi and Ellsworth [2006]. Our results suggest that stress drops of the Guy-Greenbrier sequence are similar to tectonic earthquakes at Parkfield, California (the attached figure). We will also present stress drop analysis of other suspected induced earthquake sequences using the same method.

  15. The Sturm-Liouville inverse spectral problem with boundary conditions depending on the spectral parameter

    Directory of Open Access Journals (Sweden)

    Cornelis van der Mee

    2005-01-01

    Full Text Available We present the complete version including proofs of the results announced in [van der Mee C., Pivovarchik V.: A Sturm-Liouville spectral problem with boundary conditions depending on the spectral parameter. Funct. Anal. Appl. 36 (2002, 315–317 [Funkts. Anal. Prilozh. 36 (2002, 74–77 (Russian

  16. Gomphid DNA sequence data

    Data.gov (United States)

    U.S. Environmental Protection Agency — DNA sequence data for several genetic loci. This dataset is not publicly accessible because: It's already publicly available on GenBank. It can be accessed through...

  17. General LTE Sequence

    OpenAIRE

    Billal, Masum

    2015-01-01

    In this paper,we have characterized sequences which maintain the same property described in Lifting the Exponent Lemma. Lifting the Exponent Lemma is a very powerful tool in olympiad number theory and recently it has become very popular. We generalize it to all sequences that maintain a property like it i.e. if p^{\\alpha}||a_k and p^\\b{eta}||n, then p^{{\\alpha}+\\b{eta}}||a_{nk}.

  18. Biological sequence analysis

    DEFF Research Database (Denmark)

    Durbin, Richard; Eddy, Sean; Krogh, Anders Stærmose

    This book provides an up-to-date and tutorial-level overview of sequence analysis methods, with particular emphasis on probabilistic modelling. Discussed methods include pairwise alignment, hidden Markov models, multiple alignment, profile searches, RNA secondary structure analysis, and phylogene......This book provides an up-to-date and tutorial-level overview of sequence analysis methods, with particular emphasis on probabilistic modelling. Discussed methods include pairwise alignment, hidden Markov models, multiple alignment, profile searches, RNA secondary structure analysis...

  19. HIV Sequence Compendium 2010

    Energy Technology Data Exchange (ETDEWEB)

    Kuiken, Carla [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Foley, Brian [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Leitner, Thomas [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Apetrei, Christian [Univ. of Pittsburgh, PA (United States); Hahn, Beatrice [Univ. of Alabama, Tuscaloosa, AL (United States); Mizrachi, Ilene [National Center for Biotechnology Information, Bethesda, MD (United States); Mullins, James [Univ. of Washington, Seattle, WA (United States); Rambaut, Andrew [Univ. of Edinburgh, Scotland (United Kingdom); Wolinsky, Steven [Northwestern Univ., Evanston, IL (United States); Korber, Bette [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2010-12-31

    This compendium is an annual printed summary of the data contained in the HIV sequence database. In these compendia we try to present a judicious selection of the data in such a way that it is of maximum utility to HIV researchers. Each of the alignments attempts to display the genetic variability within the different species, groups and subtypes of the virus. This compendium contains sequences published before January 1, 2010. Hence, though it is called the 2010 Compendium, its contents correspond to the 2009 curated alignments on our website. The number of sequences in the HIV database is still increasing exponentially. In total, at the time of printing, there were 339,306 sequences in the HIV Sequence Database, an increase of 45% since last year. The number of near complete genomes (>7000 nucleotides) increased to 2576 by end of 2009, reflecting a smaller increase than in previous years. However, as in previous years, the compendium alignments contain only a small fraction of these. Included in the alignments are a small number of sequences representing each of the subtypes and the more prevalent circulating recombinant forms (CRFs) such as 01 and 02, as well as a few outgroup sequences (group O and N and SIV-CPZ). Of the rarer CRFs we included one representative each. A more complete version of all alignments is available on our website, http://www.hiv.lanl.gov/content/sequence/NEWALIGN/align.html. Reprints are available from our website in the form of both HTML and PDF files. As always, we are open to complaints and suggestions for improvement. Inquiries and comments regarding the compendium should be addressed to seq-info@lanl.gov.

  20. Spectral image reconstruction using an edge preserving spatio-spectral Wiener estimation.

    Science.gov (United States)

    Urban, Philipp; Rosen, Mitchell R; Berns, Roy S

    2009-08-01

    Reconstruction of spectral images from camera responses is investigated using an edge preserving spatio-spectral Wiener estimation. A Wiener denoising filter and a spectral reconstruction Wiener filter are combined into a single spatio-spectral filter using local propagation of the noise covariance matrix. To preserve edges the local mean and covariance matrix of camera responses is estimated by bilateral weighting of neighboring pixels. We derive the edge-preserving spatio-spectral Wiener estimation by means of Bayesian inference and show that it fades into the standard Wiener reflectance estimation shifted by a constant reflectance in case of vanishing noise. Simulation experiments conducted on a six-channel camera system and on multispectral test images show the performance of the filter, especially for edge regions. A test implementation of the method is provided as a MATLAB script at the first author's website.

  1. Spectral resolution measurement technique for Czerny-Turner spectrometers based on spectral interferometry

    Science.gov (United States)

    Contreras Martínez, Ramiro; Garduño Mejía, Jesús; Rosete Aguilar, Martha; Román Moreno, Carlos J.

    2016-08-01

    We propose the design of a new technique for measuring the spectral resolution of a Czerny-Turner Spectrometer based on spectral interferometry of ultrashort laser pulses. It is well known that ultrashort pulse measurement like SPIDER and TADPOLE techniques requires a precise and well characterized spectrum, especially in fringe resolution. We developed a new technique, to our knowledge, in which by measuring the nominal fringe spacing of a spectral interferogram one can characterize the spectral resolution in a Czerny-Turner spectrometer using Ryleigh's criteria. This technique was tested in a commercial Czerny-Turner spectrometer. The results demonstrate a consistent spectral resolution between what was reported by the manufacturer. The actual calibration technique was applied in a homemade broadband astigmatism-free Czerny-Turner spectrometer. Theory and experimental results are presented.

  2. Listening talkers produce great spectral tilt contrasts

    DEFF Research Database (Denmark)

    Christiansen, Thomas Ulrich; Heegård, Jan; Henrichsen, Peter Juel

    It is well known that the envelope of the long-term average speech spectrum flattens with vocal effort. A recent study [1] showed that content words had a flatter spectral envelope than content words at the same overall level for a specific Danish speech material. The present paper investigates...... of colored geometrical shapes taken from DanPASS [2]. The spectral tilt was gauged by calculating the band-level difference in dB between two frequency bands with pass-bands 150 to 803 Hz and 803 to 1358 Hz respectively in 5 ms intervals. This was done separately for intervals containing content words...... and function words and grouped by talker. The spectral tilt difference was then calculated as the average band-level difference for function words minus the average band-level difference for content words. This calculation was grouped per talker. For the monologues these differences ranged between 5 and 8 d...

  3. Automated spectral classification and the GAIA project

    Science.gov (United States)

    Lasala, Jerry; Kurtz, Michael J.

    1995-01-01

    Two dimensional spectral types for each of the stars observed in the global astrometric interferometer for astrophysics (GAIA) mission would provide additional information for the galactic structure and stellar evolution studies, as well as helping in the identification of unusual objects and populations. The classification of the large quantity generated spectra requires that automated techniques are implemented. Approaches for the automatic classification are reviewed, and a metric-distance method is discussed. In tests, the metric-distance method produced spectral types with mean errors comparable to those of human classifiers working at similar resolution. Data and equipment requirements for an automated classification survey, are discussed. A program of auxiliary observations is proposed to yield spectral types and radial velocities for the GAIA-observed stars.

  4. Spectrally resolved longitudinal spatial coherence inteferometry

    Science.gov (United States)

    Woodard, Ethan R.; Kudenov, Michael W.

    2017-05-01

    We present an alternative imaging technique using spectrally resolved longitudinal spatial coherence interferometry to encode a scene's angular information onto the source's power spectrum. Fourier transformation of the spectrally resolved channeled spectrum output yields a measurement of the incident scene's angular spectrum. Theory for the spectrally resolved interferometric technique is detailed, demonstrating analogies to conventional Fourier transform spectroscopy. An experimental proof of concept system and results are presented using an angularly-dependent Fabry-Perot interferometer-based optical design for successful reconstruction of one-dimensional sinusoidal angular spectra. Discussion for a potential future application of the technique, in which polarization information is encoded onto the source's power spectrum is also given.

  5. Multiple spectral splits of supernova neutrinos.

    Science.gov (United States)

    Dasgupta, Basudeb; Dighe, Amol; Raffelt, Georg G; Smirnov, Alexei Yu

    2009-07-31

    Collective oscillations of supernova neutrinos swap the spectra f(nu(e))(E) and f(nu[over ](e))(E) with those of another flavor in certain energy intervals bounded by sharp spectral splits. This phenomenon is far more general than previously appreciated: typically one finds one or more swaps and accompanying splits in the nu and nu[over ] channels for both inverted and normal neutrino mass hierarchies. Depending on an instability condition, swaps develop around spectral crossings (energies where f(nu(e))=f(nu(x)), f(nu[over ](e))=f(nu[over ](x)) as well as E-->infinity where all fluxes vanish), and the widths of swaps are determined by the spectra and fluxes. Washout by multiangle decoherence varies across the spectrum and splits can survive as sharp spectral features.

  6. Spectral Trends of Titan's Tropical Surface

    Science.gov (United States)

    Griffith, Caitlin Ann; Penteado, Paulo F.; Turner, Jake; Montiel, Nicholas; Schoenfeld, Ashley; Lopes, Rosaly M. C.; Soderblom, Laurence A.; Neish, Catherine; Radebaugh, Jani

    2016-10-01

    Titan's surface can be observed most clearly at 8 spectral regions that lie in between the strong methane bands in Titan's spectrum. Within these "windows", between 0.9 to 5 microns, the surface is nonetheless obscured by methane and haze, the latter of which is optically thick at lower wavelengths. Thus studies of Titan's surface must eliminate the effects of atmospheric extinction and extract the subtle spectral features that underlie the dominant spectral trends.To determine the subtle spectral features of Titan's tropical surface (30S--30N) we conducted a Principal Components Analysis (PCA) of the I/F at the 1.1, 1.3, 1.6 and 2.0 um wavelength windows, recorded by Cassini/VIMS. The PCA analysis identifies the spectral trend that defines the highest variance in the data (the principal component), as well as successively weaker orthogonal trends, without a priori assumptions about the surface composition, e.g. as needed in radiative transfer analyses.Our analysis derives the spectral features at the four wavelengths that describe Titan's tropical surface. We detect a large almost contiguous region that extends roughly 160 degrees in longitude and which exhibits absorption features at 1.6 and 2.0, as well as 2.8 um (characteristic of water ice). This vast and perhaps tectonic feature is, in part, associated with terrain that is hypothesized to be some of the oldest surfaces on Titan. In addition, the PCA analysis indicates at least 2 separate organic spectra signatures, potentially due to the separation of liquid and refractory sediments or to their chemically alteration over time. Here we discuss the PCA analysis and compare our derived compositional maps of Titan's surface with Radar maps of the topography and morphology, to entertain questions regarding the geology of Titan's surface the age of its atmosphere.

  7. Beam profile assessment in spectral CT scanners.

    Science.gov (United States)

    Anjomrouz, Marzieh; Shamshad, Muhammad; Panta, Raj K; Broeke, Lieza Vanden; Schleich, Nanette; Atharifard, Ali; Aamir, Raja; Bheesette, Srinidhi; Walsh, Michael F; Goulter, Brian P; Bell, Stephen T; Bateman, Christopher J; Butler, Anthony P H; Butler, Philip H

    2018-03-01

    In this paper, we present a method that uses a combination of experimental and modeled data to assess properties of x-ray beam measured using a small-animal spectral scanner. The spatial properties of the beam profile are characterized by beam profile shape, the angular offset along the rotational axis, and the photon count difference between experimental and modeled data at the central beam axis. Temporal stability of the beam profile is assessed by measuring intra- and interscan count variations. The beam profile assessment method was evaluated on several spectral CT scanners equipped with Medipix3RX-based detectors. On a well-calibrated spectral CT scanner, we measured an integral count error of 0.5%, intrascan count variation of 0.1%, and an interscan count variation of less than 1%. The angular offset of the beam center ranged from 0.8° to 1.6° for the studied spectral CT scanners. We also demonstrate the capability of this method to identify poor performance of the system through analyzing the deviation of the experimental beam profile from the model. This technique can, therefore, aid in monitoring the system performance to obtain a robust spectral CT; providing the reliable quantitative images. Furthermore, the accurate offset parameters of a spectral scanner provided by this method allow us to incorporate a more realistic form of the photon distribution in the polychromatic-based image reconstruction models. Both improvements of the reliability of the system and accuracy of the volume reconstruction result in a better discrimination and quantification of the imaged materials. © 2018 MARS Bioimaging Ltd. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

  8. Moments of spectral functions: Monte Carlo evaluation and verification.

    Science.gov (United States)

    Predescu, Cristian

    2005-11-01

    The subject of the present study is the Monte Carlo path-integral evaluation of the moments of spectral functions. Such moments can be computed by formal differentiation of certain estimating functionals that are infinitely differentiable against time whenever the potential function is arbitrarily smooth. Here, I demonstrate that the numerical differentiation of the estimating functionals can be more successfully implemented by means of pseudospectral methods (e.g., exact differentiation of a Chebyshev polynomial interpolant), which utilize information from the entire interval . The algorithmic detail that leads to robust numerical approximations is the fact that the path-integral action and not the actual estimating functional are interpolated. Although the resulting approximation to the estimating functional is nonlinear, the derivatives can be computed from it in a fast and stable way by contour integration in the complex plane, with the help of the Cauchy integral formula (e.g., by Lyness' method). An interesting aspect of the present development is that Hamburger's conditions for a finite sequence of numbers to be a moment sequence provide the necessary and sufficient criteria for the computed data to be compatible with the existence of an inversion algorithm. Finally, the issue of appearance of the sign problem in the computation of moments, albeit in a milder form than for other quantities, is addressed.

  9. Spectroscopic evolution of massive stars on the main sequence

    Science.gov (United States)

    Martins, F.; Palacios, A.

    2017-02-01

    Context. The evolution of massive stars depends on several parameters, and the relation between different morphological types is not fully constrained. Aims: We aim to provide an observational view of evolutionary models in the Hertzsprung-Russell diagram, on the main sequence. This view should help compare observations and model predictions. Methods: We first computed evolutionary models with the code STAREVOL for initial masses between 15 and 100 M⊙. We subsequently calculated atmosphere models at specific points along the evolutionary tracks, using the code CMFGEN. Synthetic spectra obtained in this way were classified as if they were observational data: we assigned them a spectral type and a luminosity class. We tested our spectral classification by comparison to observed spectra of various stars with different spectral types. We also compared our results with empirical data of a large number of OB stars. Results: We obtain spectroscopic sequences along evolutionary tracks. In our computations, the earliest O stars (O2-3.5) appear only above 50 M⊙. For later spectral types, a similar mass limit exists, but is lower. A luminosity class V does not correspond to the entire main sequence. This only holds for the 15 M⊙ track. As mass increases, a larger portion of the main sequence is spent in luminosity class III. Above 50 M⊙, supergiants appear before the end of core-hydrogen burning. Dwarf stars (luminosity class V) do not occur on the zero-age main sequence above 80 M⊙. Consequently, the distribution of luminosity class V in the HR diagram is not a diagnostic of the length of the main sequence (above 15 M⊙) and cannot be used to constrain the size of the convective core. The distribution of dwarfs and giants in the HR diagram that results from our calculations agrees well with the location of stars analyzed by means of quantitative spectroscopy. For supergiants, there is a slight discrepancy in the sense that luminosity class I is observed slightly

  10. Universal fermionic spectral functions from string theory.

    Science.gov (United States)

    Gauntlett, Jerome P; Sonner, Julian; Waldram, Daniel

    2011-12-09

    We carry out the first holographic calculation of a fermionic response function for a strongly coupled d=3 system with an explicit D=10 or D=11 supergravity dual. By considering the supersymmetry current, we obtain a universal result applicable to all d=3 N=2 SCFTs with such duals. Surprisingly, the spectral function does not exhibit a Fermi surface, despite the fact that the system is at finite charge density. We show that it has a phonino pole and at low frequencies there is a depletion of spectral weight with a power-law scaling which is governed by a locally quantum critical point.

  11. Glue Film Thickness Measurements by Spectral Reflectance

    Energy Technology Data Exchange (ETDEWEB)

    B. R. Marshall

    2010-09-20

    Spectral reflectance was used to determine the thickness of thin glue layers in a study of the effect of the glue on radiance and reflectance measurements of shocked-tin substrates attached to lithium fluoride windows. Measurements based on profilometry of the components were found to be inaccurate due to flatness variations and deformation of the tin substrate under pressure during the gluing process. The accuracy of the spectral reflectance measurements were estimated to be ±0.5 μm, which was sufficient to demonstrate a convincing correlation between glue thickness and shock-generated light.

  12. Glue Film Thickness Measurements by Spectral Reflectance

    International Nuclear Information System (INIS)

    Marshall, B.R.

    2010-01-01

    Spectral reflectance was used to determine the thickness of thin glue layers in a study of the effect of the glue on radiance and reflectance measurements of shocked-tin substrates attached to lithium fluoride windows. Measurements based on profilometry of the components were found to be inaccurate due to flatness variations and deformation of the tin substrate under pressure during the gluing process. The accuracy of the spectral reflectance measurements were estimated to be ±0.5 (micro)m, which was sufficient to demonstrate a convincing correlation between glue thickness and shock-generated light.

  13. Quantum BCH Codes Based on Spectral Techniques

    International Nuclear Information System (INIS)

    Guo Ying; Zeng Guihua

    2006-01-01

    When the time variable in quantum signal processing is discrete, the Fourier transform exists on the vector space of n-tuples over the Galois field F 2 , which plays an important role in the investigation of quantum signals. By using Fourier transforms, the idea of quantum coding theory can be described in a setting that is much different from that seen that far. Quantum BCH codes can be defined as codes whose quantum states have certain specified consecutive spectral components equal to zero and the error-correcting ability is also described by the number of the consecutive zeros. Moreover, the decoding of quantum codes can be described spectrally with more efficiency.

  14. Spectral methods in numerical plasma simulation

    International Nuclear Information System (INIS)

    Coutsias, E.A.; Hansen, F.R.; Huld, T.; Knorr, G.; Lynov, J.P.

    1989-01-01

    An introduction is given to the use of spectral methods in numerical plasma simulation. As examples of the use of spectral methods, solutions to the two-dimensional Euler equations in both a simple, doubly periodic region, and on an annulus will be shown. In the first case, the solution is expanded in a two-dimensional Fourier series, while a Chebyshev-Fourier expansion is employed in the second case. A new, efficient algorithm for the solution of Poisson's equation on an annulus is introduced. Problems connected to aliasing and to short wavelength noise generated by gradient steepening are discussed. (orig.)

  15. Spectral Methods in Numerical Plasma Simulation

    DEFF Research Database (Denmark)

    Coutsias, E.A.; Hansen, F.R.; Huld, T.

    1989-01-01

    in a two-dimensional Fourier series, while a Chebyshev-Fourier expansion is employed in the second case. A new, efficient algorithm for the solution of Poisson's equation on an annulus is introduced. Problems connected to aliasing and to short wavelength noise generated by gradient steepening are discussed.......An introduction is given to the use of spectral methods in numerical plasma simulation. As examples of the use of spectral methods, solutions to the two-dimensional Euler equations in both a simple, doubly periodic region, and on an annulus will be shown. In the first case, the solution is expanded...

  16. Bedform characterization through 2D spectral analysis

    DEFF Research Database (Denmark)

    Lefebvre, Alice; Ernstsen, Verner Brandbyge; Winter, Christian

    2011-01-01

    characteristics using twodimensional (2D) spectral analysis is presented and tested on seabed elevation data from the Knudedyb tidal inlet in the Danish Wadden Sea, where large compound bedforms are found. The bathymetric data were divided into 20x20 m areas on which a 2D spectral analysis was applied. The most...... energetic peak of the 2D spectrum was found and its energy, frequency and direction were calculated. A power-law was fitted to the average of slices taken through the 2D spectrum; its slope and y-intercept were calculated. Using these results the test area was morphologically classified into 4 distinct...

  17. Krein Spectral Triples and the Fermionic Action

    International Nuclear Information System (INIS)

    Dungen, Koen van den

    2016-01-01

    Motivated by the space of spinors on a Lorentzian manifold, we define Krein spectral triples, which generalise spectral triples from Hilbert spaces to Krein spaces. This Krein space approach allows for an improved formulation of the fermionic action for almost-commutative manifolds. We show by explicit calculation that this action functional recovers the correct Lagrangians for the cases of electrodynamics, the electro-weak theory, and the Standard Model. The description of these examples does not require a real structure, unless one includes Majorana masses, in which case the internal spaces also exhibit a Krein space structure.

  18. Spectral Classification of Asteroids by Random Forest

    Science.gov (United States)

    Huang, C.; Ma, Y. H.; Zhao, H. B.; Lu, X. P.

    2016-09-01

    With the increasing asteroid spectral and photometric data, a variety of classification methods for asteroids have been proposed. This paper classifies asteroids based on the observations of Sloan Digital Sky Survey (SDSS) Moving Object Catalogue (MOC) by using the random forest algorithm. With the training data derived from the taxonomies of Tholen, Bus, Lazzaro, DeMeo, and Principal Component Analysis, we classify 48642 asteroids according to g, r, i, and z SDSS magnitudes. In this way, asteroids are divided into 8 spectral classes (C, X, S, B, D, K, L, and V).

  19. Spectral Analysis of Large Particle Systems

    DEFF Research Database (Denmark)

    Dahlbæk, Jonas

    2017-01-01

    is on obtaining a framework which unifies and generalizes frameworks that have appeared previously in the literature. The end result is a calculus for creation/annihilation symbols, where Wick’s theorem provides a formula for the product of finitely many symbols. The framework is then applied to the Fröhlich...... polaron model. The framework is also applied to the spin boson model. The application to the spin boson model is based on the spectral renormalization group. It is shown that the spectral renormalization group scheme can be natu- rally posed as an iterated Grushin problem. While it is already known...

  20. Novel spectral features of nanoelectromechanical systems

    KAUST Repository

    Tahir, M.

    2014-02-17

    Electron transport through a quantum dot or single molecule coupled to a quantum oscillator is studied by the Keldysh nonequilibrium Green\\'s function formalism to obtain insight into the quantum dynamics of the electronic and oscillator degrees of freedom. We tune the electronic level of the quantum dot by a gate voltage, where the leads are kept at zero temperature. Due to the nonequilibrium distribution of the electrons in the quantum dot, the spectral function becomes a function of the gate voltage. Novel spectral features are identified for the ground and excited states of nanomechanical oscillators that can be used to enhance the measurement sensitivity.