WorldWideScience

Sample records for binary radio pulsars

  1. Understanding the evolution of close binary systems with radio pulsars

    CERN Document Server

    Benvenuto, O G; Horvath, J E

    2014-01-01

    We calculate the evolution of close binary systems (CBSs) formed by a neutron star (behaving as a radio pulsar) and a normal donor star, evolving either to helium white dwarf (HeWD) or ultra short orbital period systems. We consider X-ray irradiation feedback and evaporation due to radio pulsar irradiation. We show that irradiation feedback leads to cyclic mass transfer episodes, allowing CBSs to be observed in-between as binary radio pulsars under conditions in which standard, non-irradiated models predict the occurrence of a low mass X-ray binary. This behavior accounts for the existence of a family of eclipsing binary systems known as redbacks. We predict that redback companions should almost fill their Roche lobe, as observed in PSR J1723-2837. This state is also possible for systems evolving with larger orbital periods. Therefore, binary radio pulsars with companion star masses usually interpreted as larger than expected to produce HeWDs may also result in such {\\it quasi - Roche Lobe Overflow} states, r...

  2. UNDERSTANDING THE EVOLUTION OF CLOSE BINARY SYSTEMS WITH RADIO PULSARS

    Energy Technology Data Exchange (ETDEWEB)

    Benvenuto, O. G. [Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, 1900 La Plata, Buenos Aires (Argentina); De Vito, M. A. [Instituto de Astrofísica de La Plata (IALP), CCT-CONICET-UNLP. Paseo del Bosque S/N (B1900FWA), La Plata (Argentina); Horvath, J. E., E-mail: obenvenu@fcaglp.unlp.edu.ar, E-mail: adevito@fcaglp.unlp.edu.ar, E-mail: foton@astro.iag.usp.br [Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo R. do Matão 1226 (05508-090), Cidade Universitária, São Paulo SP (Brazil)

    2014-05-01

    We calculate the evolution of close binary systems (CBSs) formed by a neutron star (behaving as a radio pulsar) and a normal donor star, which evolve either to a helium white dwarf (HeWD) or to ultra-short orbital period systems. We consider X-ray irradiation feedback and evaporation due to radio pulsar irradiation. We show that irradiation feedback leads to cyclic mass transfer episodes, allowing CBSs to be observed in between episodes as binary radio pulsars under conditions in which standard, non-irradiated models predict the occurrence of a low-mass X-ray binary. This behavior accounts for the existence of a family of eclipsing binary systems known as redbacks. We predict that redback companions should almost fill their Roche lobe, as observed in PSR J1723-2837. This state is also possible for systems evolving with larger orbital periods. Therefore, binary radio pulsars with companion star masses usually interpreted as larger than expected to produce HeWDs may also result in such quasi-Roche lobe overflow states, rather than hosting a carbon-oxygen WD. We found that CBSs with initial orbital periods of P{sub i} < 1 day evolve into redbacks. Some of them produce low-mass HeWDs, and a subgroup with shorter P{sub i} becomes black widows (BWs). Thus, BWs descend from redbacks, although not all redbacks evolve into BWs. There is mounting observational evidence favoring BW pulsars to be very massive (≳ 2 M {sub ☉}). As they should be redback descendants, redback pulsars should also be very massive, since most of the mass is transferred before this stage.

  3. A Radio Pulsar/X-ray Binary Link

    CERN Document Server

    Archibald, Anne M; Ransom, Scott M; Kaspi, Victoria M; Kondratiev, Vladislav I; Lorimer, Duncan R; McLaughlin, Maura A; Boyles, Jason; Hessels, Jason W T; Lynch, Ryan; van Leeuwen, Joeri; Roberts, Mallory S E; Jenet, Frederick; Champion, David J; Rosen, Rachel; Barlow, Brad N; Dunlap, Bart H; Remillard, Ronald A

    2009-01-01

    Radio pulsars with millisecond spin periods are thought to have been spun up by transfer of matter and angular momentum from a low-mass companion star during an X-ray-emitting phase. The spin periods of the neutron stars in several such low-mass X-ray binary (LMXB) systems have been shown to be in the millisecond regime, but no radio pulsations have been detected. Here we report on detection and follow-up observations of a nearby radio millisecond pulsar (MSP) in a circular binary orbit with an optically identified companion star. Optical observations indicate that an accretion disk was present in this system within the last decade. Our optical data show no evidence that one exists today, suggesting that the radio MSP has turned on after a recent LMXB phase.

  4. On tests of general relativity with binary radio pulsars

    Science.gov (United States)

    Del Pozzo, W.; Vecchio, A.

    2016-10-01

    The timing of radio pulsars in binary systems provides a superb testing ground of general relativity. Here we propose a Bayesian approach to carry out these tests, and a relevant efficient numerical implementation, that has several conceptual and practical advantages with respect to traditional methods based on least-squares fit that have been used so far: (i) it accounts for the actual structure of the likelihood function - and it is not predicated on the Laplace approximation which is implicitly built in least-squares fit that can potentially bias the inference - (ii) it provides the ratio of the evidences of any two models under consideration as the statistical quantity to compare different theories, and (iii) it allows us to put joint constraints from the monitoring of multiple systems, that can be expressed in terms of ratio of evidences or probability intervals of global (thus not system-dependent) parameters of the theory, if any exists. Our proposed approach optimally exploits the progress in timing of radio pulsars and the increase in the number of observed systems. We demonstrate the power of this framework using simulated data sets that are representative of current observations.

  5. On tests of general relativity with binary radio pulsars

    CERN Document Server

    Del Pozzo, Walter

    2016-01-01

    The timing of radio pulsars in binary systems provides a superb testing ground of general relativity. Here we propose a Bayesian approach to carry out these tests, and a relevant efficient numerical implementation, that has several conceptual and practical advantages with respect to traditional methods based on least-square-fits that have been used so far: (i) it accounts for the actual structure of the likelihood function - and it is not predicated on the Laplace approximation which is implicitly built in least-square fits that can potentially bias the inference - (ii) it provides the ratio of the evidences of any two models under consideration as the statistical quantity to compare different theories, and (iii) it allows us to put joint constraints from the monitoring of multiple systems, that can be expressed in terms of ratio of evidences or probability intervals of global (thus not system-dependent) parameters of the theory, if any exists. Our proposed approach optimally exploits the progress in timing o...

  6. Extended Corbet Diagram of HMXBs,LMXBs and radio pulsar binaries

    Institute of Scientific and Technical Information of China (English)

    ALI; Esamdin

    2010-01-01

    The evolutionary scenario of neutron star binaries is still an essential enigma in both stellar astrophysics and high energy astrophysics.In order to explore the scenario,we include the accumulation of data on the orbits and spins of compact binaries in multi-wavelength ranging from radio to X-ray,such as radio pulsar binaries,HMXBs,and LMXBs,filling them into the so called "Corbet Diagram" which initially investigated the period of orbit(Porb)~the period of spin(Pspin) correlation of HMXBs.We find that the evolutionary scenario comes more clearly and makes strong confirmation of the connection between LMXBs and radio pulsar binaries,predicted by the recycle process.However,the origins of radio pulsar binaries sre still unknown.Accretion Induced Collapse(AIP) process may be a mechanism which can explain the origin of the binary millisecond pulsars with relatively longer orbital periods.A correlation of P1/3orb~P-1spin of LMXBs and radio pulsar binaries may exist.

  7. Binary and Millisecond Pulsars

    Directory of Open Access Journals (Sweden)

    Lorimer Duncan R.

    2008-11-01

    Full Text Available We review the main properties, demographics and applications of binary and millisecond radio pulsars. Our knowledge of these exciting objects has greatly increased in recent years, mainly due to successful surveys which have brought the known pulsar population to over 1800. There are now 83 binary and millisecond pulsars associated with the disk of our Galaxy, and a further 140 pulsars in 26 of the Galactic globular clusters. Recent highlights include the discovery of the young relativistic binary system PSR J1906+0746, a rejuvination in globular cluster pulsar research including growing numbers of pulsars with masses in excess of 1.5M_⊙, a precise measurement of relativistic spin precession in the double pulsar system and a Galactic millisecond pulsar in an eccentric (e = 0.44 orbit around an unevolved companion.

  8. Supermassive black hole binaries and transient radio events: studies in pulsar astronomy

    Science.gov (United States)

    Burke-Spolaor, S.

    2011-06-01

    The field of pulsar astronomy encompasses a rich breadth of astrophysical topics. The research in this thesis contributes to two particular subjects of pulsar astronomy: gravitational wave science, and identifying celestial sources of pulsed radio emission. We first investigated the detection of supermassive black hole (SMBH) binaries, which are the brightest expected source of gravitational waves for pulsar timing. We considered whether two electromagnetic SMBH tracers, velocity-resolved emission lines in active nuclei, and radio galactic nuclei with spatially-resolved, flat-spectrum cores, can reveal systems emitting gravitational waves in the pulsar timing band. We found that there are systems which may in principle be simultaneously detectable by both an electromagnetic signature and gravitational emission, however the probability of actually identifying such a system is low (they will represent much less than 1% of a randomly selected galactic nucleus sample). This study accents the fact that electromagnetic indicators may be used to explore binary populations down to the 'stalling radii' at which binary inspiral evolution may stall indefinitely at radii exceeding those which produce gravitational radiation in the pulsar timing band. We then performed a search for binary SMBH holes in archival Very Long Baseline Interferometry data for 3114 radio-luminous active galactic nuclei. One source was detected as a double nucleus. This result is interpreted in terms of post-merger timescales for SMBH centralisation, implications for 'stalling', and the relationship of radio activity in nuclei to mergers. Our analysis suggested that binary pair evolution of SMBHs (both of masses >108M circled bullet) spends less than 500Myr in progression from the merging of galactic stellar cores to within the purported stalling radius for SMBH pairs, giving no evidence for an excess of stalled binary systems at small separations. Circumstantial evidence showed that the relative state

  9. Eclipsing Binary Pulsars

    CERN Document Server

    Freire, P C C

    2004-01-01

    The first eclipsing binary pulsar, PSR B1957+20, was discovered in 1987. Since then, 13 other eclipsing low-mass binary pulsars have been found, 12 of these are in globular clusters. In this paper we list the known eclipsing binary pulsars and their properties, with special attention to the eclipsing systems in 47 Tuc. We find that there are two fundamentally different groups of eclipsing binary pulsars; separated by their companion masses. The less massive systems (M_c ~ 0.02 M_sun) are a product of predictable stellar evolution in binary pulsars. The systems with more massive companions (M_c ~ 0.2 M_sun) were formed by exchange encounters in globular clusters, and for that reason are exclusive to those environments. This class of systems can be used to learn about the neutron star recycling fraction in the globular clusters actively forming pulsars. We suggest that most of these binary systems are undetectable at radio wavelengths.

  10. PSR J1723-2837: An Eclipsing Binary Radio Millisecond Pulsar

    CERN Document Server

    Crawford, F; Stairs, I H; Kaplan, D L; McLaughlin, M A; Freire, P C C; Burgay, M; Camilo, F; D'Amico, N; Faulkner, A; Kramer, M; Lorimer, D R; Manchester, R N; Possenti, A; Steeghs, D

    2013-01-01

    We present a study of PSR J1723-2837, an eclipsing, 1.86 ms millisecond binary radio pulsar discovered in the Parkes Multibeam survey. Radio timing indicates that the pulsar has a circular orbit with a 15 hr orbital period, a low-mass companion, and a measurable orbital period derivative. The eclipse fraction of ~15% during the pulsar's orbit is twice the Roche lobe size inferred for the companion. The timing behavior is significantly affected by unmodeled systematics of astrophysical origin, and higher-order orbital period derivatives are needed in the timing solution to account for these variations. We have identified the pulsar's (non-degenerate) companion using archival ultraviolet, optical, and infrared survey data and new optical photometry. Doppler shifts from optical spectroscopy confirm the star's association with the pulsar and indicate a pulsar-to-companion mass ratio of 3.3 +/- 0.5, corresponding to a companion mass range of 0.4 to 0.7 Msun and an orbital inclination angle range of between 30 and ...

  11. PSR J1723–2837: AN ECLIPSING BINARY RADIO MILLISECOND PULSAR

    Energy Technology Data Exchange (ETDEWEB)

    Crawford, Fronefield [Department of Physics and Astronomy, Franklin and Marshall College, P.O. Box 3003, Lancaster, PA 17604 (United States); Lyne, Andrew G. [Jodrell Bank Centre for Astrophysics, University of Manchester, Manchester M13 9PL (United Kingdom); Stairs, Ingrid H. [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1 (Canada); Kaplan, David L. [Physics Department, University of Wisconsin - Milwaukee, Milwaukee, WI 53211 (United States); McLaughlin, Maura A.; Lorimer, Duncan R. [Department of Physics, West Virginia University, Morgantown, WV 26506 (United States); Freire, Paulo C. C.; Kramer, Michael [Max-Planck-Institut für Radioastronomie, auf dem Huegel 69, D-53121 Bonn (Germany); Burgay, Marta; D' Amico, Nichi; Possenti, Andrea [INAF - Osservatorio Astronomico di Cagliari, Poggio dei Pini, I-09012 Capoterra (Italy); Camilo, Fernando [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Faulkner, Andrew [Cavendish Laboratory, University of Cambridge, J. J. Thompson Avenue, Cambridge, CB3 0HE (United Kingdom); Manchester, Richard N. [CSIRO Astronomy and Space Science, Australia Telescope National Facility, P.O. Box 76, Epping, NSW 1710 (Australia); Steeghs, Danny, E-mail: fcrawfor@fandm.edu [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom)

    2013-10-10

    We present a study of PSR J1723–2837, an eclipsing, 1.86 ms millisecond binary radio pulsar discovered in the Parkes Multibeam survey. Radio timing indicates that the pulsar has a circular orbit with a 15 hr orbital period, a low-mass companion, and a measurable orbital period derivative. The eclipse fraction of ∼15% during the pulsar's orbit is twice the Roche lobe size inferred for the companion. The timing behavior is significantly affected by unmodeled systematics of astrophysical origin, and higher-order orbital period derivatives are needed in the timing solution to account for these variations. We have identified the pulsar's (non-degenerate) companion using archival ultraviolet, optical, and infrared survey data and new optical photometry. Doppler shifts from optical spectroscopy confirm the star's association with the pulsar and indicate a pulsar-to-companion mass ratio of 3.3 ± 0.5, corresponding to a companion mass range of 0.4 to 0.7 M{sub ☉} and an orbital inclination angle range of between 30° and 41°, assuming a pulsar mass range of 1.4-2.0 M{sub ☉}. Spectroscopy indicates a spectral type of G for the companion and an inferred Roche-lobe-filling distance that is consistent with the distance estimated from radio dispersion. The features of PSR J1723–2837 indicate that it is likely a 'redback' system. Unlike the five other Galactic redbacks discovered to date, PSR J1723–2837 has not been detected as a γ-ray source with Fermi. This may be due to an intrinsic spin-down luminosity that is much smaller than the measured value if the unmeasured contribution from proper motion is large.

  12. PSR J1723-2837: An Eclipsing Binary Radio Millisecond Pulsar

    Science.gov (United States)

    Crawford, Fronefield; Lyne, Andrew G.; Stairs, Ingrid H.; Kaplan, David L.; McLaughlin, Maura A.; Freire, Paulo C. C.; Burgay, Marta; Camilo, Fernando; D'Amico, Nichi; Faulkner, Andrew; Kramer, Michael; Lorimer, Duncan R.; Manchester, Richard N.; Possenti, Andrea; Steeghs, Danny

    2013-10-01

    We present a study of PSR J1723-2837, an eclipsing, 1.86 ms millisecond binary radio pulsar discovered in the Parkes Multibeam survey. Radio timing indicates that the pulsar has a circular orbit with a 15 hr orbital period, a low-mass companion, and a measurable orbital period derivative. The eclipse fraction of ~15% during the pulsar's orbit is twice the Roche lobe size inferred for the companion. The timing behavior is significantly affected by unmodeled systematics of astrophysical origin, and higher-order orbital period derivatives are needed in the timing solution to account for these variations. We have identified the pulsar's (non-degenerate) companion using archival ultraviolet, optical, and infrared survey data and new optical photometry. Doppler shifts from optical spectroscopy confirm the star's association with the pulsar and indicate a pulsar-to-companion mass ratio of 3.3 ± 0.5, corresponding to a companion mass range of 0.4 to 0.7 M ⊙ and an orbital inclination angle range of between 30° and 41°, assuming a pulsar mass range of 1.4-2.0 M ⊙. Spectroscopy indicates a spectral type of G for the companion and an inferred Roche-lobe-filling distance that is consistent with the distance estimated from radio dispersion. The features of PSR J1723-2837 indicate that it is likely a "redback" system. Unlike the five other Galactic redbacks discovered to date, PSR J1723-2837 has not been detected as a γ-ray source with Fermi. This may be due to an intrinsic spin-down luminosity that is much smaller than the measured value if the unmeasured contribution from proper motion is large.

  13. Algorithms for searching Fast radio bursts and pulsars in tight binary systems.

    Science.gov (United States)

    Zackay, Barak

    2017-01-01

    Fast radio bursts (FRB's) are an exciting, recently discovered, astrophysical transients which their origins are unknown.Currently, these bursts are believed to be coming from cosmological distances, allowing us to probe the electron content on cosmological length scales. Even though their precise localization is crucial for the determination of their origin, radio interferometers were not extensively employed in searching for them due to computational limitations.I will briefly present the Fast Dispersion Measure Transform (FDMT) algorithm,that allows to reduce the operation count in blind incoherent dedispersion by 2-3 orders of magnitude.In addition, FDMT enables to probe the unexplored domain of sub-microsecond astrophysical pulses.Pulsars in tight binary systems are among the most important astrophysical objects as they provide us our best tests of general relativity in the strong field regime.I will provide a preview to a novel algorithm that enables the detection of pulsars in short binary systems using observation times longer than an orbital period.Current pulsar search programs limit their searches for integration times shorter than a few percents of the orbital period.Until now, searching for pulsars in binary systems using observation times longer than an orbital period was considered impossible as one has to blindly enumerate all options for the Keplerian parameters, the pulsar rotation period, and the unknown DM.Using the current state of the art pulsar search techniques and all computers on the earth, such an enumeration would take longer than a Hubble time. I will demonstrate that using the new algorithm, it is possible to conduct such an enumeration on a laptop using real data of the double pulsar PSR J0737-3039.Among the other applications of this algorithm are:1) Searching for all pulsars on all sky positions in gamma ray observations of the Fermi LAT satellite.2) Blind searching for continuous gravitational wave sources emitted by pulsars with

  14. LMXB and IMXB Evolution: I. The Binary Radio Pulsar PSR J1614-2230

    CERN Document Server

    Lin, Jinrong; Podsiadlowski, Ph; Nelson, L; Paxton, B; Todorov, P

    2010-01-01

    We have computed an extensive grid of binary evolution tracks to represent low- and intermediate mass X-ray binaries (LMXBs and IMXBs). The grid includes 42,000 models which covers 60 initial donor masses over the range of 1-4 solar masses and, for each of these, 700 initial orbital periods over the range of 10-250 hours. These results can be applied to understanding LMXBs and IMXBs: those that evolve analogously to CVs; those that form ultracompact binaries with orbital periods in the range of 6-50 minutes; and those that lead to wide orbits with giant donors. We also investigate the relic binary recycled radio pulsars into which these systems evolve. To evolve the donor stars in this study, we utilized a newly developed stellar evolution code called "MESA" that was designed, among other things, to be able to handle very low-mass and degenerate donors. This first application of the results is aimed at an understanding of the newly discovered pulsar PSR J1614-2230 which has a 1.97 solar masses neutron star, o...

  15. The low-mass X-ray binary-millisecond radio pulsar birthrate problem revisited

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    We investigate the birthrate problem for low-mass X-ray binaries(LMXBs) and millisecond radio pulsars(MRPs) in this paper.We consider intermediate-mass and low-mass X-ray binaries(I/LMXBs) to be the progenitors of MRPs,and calculate their evolutionary response to the cosmic star formation rate(SFR) both semi-analytically and numerically.With a typical value(1 Gyr) of the LMXB lifetime,one may expect comparable birthrates of LMXBs and MRPs,but the calculated number of LMXBs is an order of magnitude higher than that observed in the Galaxy.Instead,we suggest that the birthrate problem could be solved if most MRPs have evolved from faint to rather than bright LMXBs.The former may have a population of-104 in the Galaxy.

  16. The Quasi-Roche lobe overflow state in the evolution of Close Binary Systems containing a radio pulsar

    CERN Document Server

    Benvenuto, O G; Horvath, J E

    2014-01-01

    We study the evolution of close binary systems formed by a normal (solar composition), intermediate mass donor star together with a neutron star. We consider models including irradiation feedback and evaporation. These non-standard ingredients deeply modify the mass transfer stages of these binaries. While models that neglect irradiation feedback undergo continuous, long standing mass transfer episodes, models including these effect suffer a number cycles of mass transfer and detachment. During mass transfer the systems should reveal themselves as low-mass X-ray binaries (LMXBs), whereas when detached they behave as a binary radio pulsars. We show that at these stages irradiated models are in a Roche lobe overflow (RLOF) state or in a quasi-RLOF state. Quasi-RLOF stars have a radius slightly smaller than its Roche lobe. Remarkably, these conditions are attained for orbital period and donor mass values in the range corresponding to a family of binary radio pulsars known as "redbacks". Thus, redback companions ...

  17. Populations and evolution of radio pulsars

    Institute of Scientific and Technical Information of China (English)

    李向东; 汪珍如

    1996-01-01

    A new physical parameter Q=log(We/P2/3) is defined as a criterion for judging whether a radio pulsar is a normal pulsar or a recycled pulsar originating from accreting binary systems.Based on the definition,the observational characteristics and the evolution of the two groups of pulsars are discussed.

  18. X-ray and $\\gamma$-ray Studies of the Millisecond Pulsar and PossibleX-ray Binary/Radio Pulsar Transition Object PSR J1723-2837

    CERN Document Server

    Bogdanov, Slavko; Crawford, Fronefield; Possenti, Andrea; McLaughlin, Maura A; Freire, Paulo

    2013-01-01

    We present X-ray observations of the ``redback'' eclipsing radio millisecond pulsar and candidate radio pulsar/X-ray binary transition object PSR J1723-2837. The X-ray emission from the system is predominantly non-thermal and exhibits pronounced variability as a function of orbital phase, with a factor of ~2 reduction in brightness around superior conjunction. Such temporal behavior appears to be a defining characteristic of this variety of peculiar millisecond pulsar binaries and is likely caused by a partial geometric occultation by the main-sequence-like companion of a shock within the binary. There is no indication of diffuse X-ray emission from a bow shock or pulsar wind nebula associated with the pulsar. We also report on a search for point source emission and $\\gamma$-ray pulsations in Fermi Large Area Telescope data using a likelihood analysis and photon probability weighting. Although PSR J1723-2837 is consistent with being a $\\gamma$-ray point source, due to the strong Galactic diffuse emission at i...

  19. X-ray and γ-ray studies of the millisecond pulsar and possible X-ray binary/radio pulsar transition object PSR J1723-2837

    Energy Technology Data Exchange (ETDEWEB)

    Bogdanov, Slavko [Columbia Astrophysics Laboratory, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Esposito, Paolo [INAF-IASF Milano, via East Bassini 15, I-20133 Milano (Italy); Crawford III, Fronefield [Department of Physics and Astronomy, Franklin and Marshall College, P.O. Box 3003, Lancaster, PA 17604 (United States); Possenti, Andrea [INAF-Osservatorio Astronomico di Cagliari, Loc. Poggio dei Pini, Strada 54, I-09012 Capoterra (Italy); McLaughlin, Maura A. [Department of Physics and Astronomy, West Virginia University, 210E Hodges Hall, Morgantown, WV 26506 (United States); Freire, Paulo, E-mail: slavko@astro.columbia.edu [Max-Planck-Institut für Radioastronomie, D-53121 Bonn (Germany)

    2014-01-20

    We present X-ray observations of the 'redback' eclipsing radio millisecond pulsar (MSP) and candidate radio pulsar/X-ray binary transition object PSR J1723-2837. The X-ray emission from the system is predominantly non-thermal and exhibits pronounced variability as a function of orbital phase, with a factor of ∼2 reduction in brightness around superior conjunction. Such temporal behavior appears to be a defining characteristic of this variety of peculiar MSP binaries and is likely caused by a partial geometric occultation by the main-sequence-like companion of a shock within the binary. There is no indication of diffuse X-ray emission from a bow shock or pulsar wind nebula associated with the pulsar. We also report on a search for point source emission and γ-ray pulsations in Fermi Large Area Telescope data using a likelihood analysis and photon probability weighting. Although PSR J1723-2837 is consistent with being a γ-ray point source, due to the strong Galactic diffuse emission at its position a definitive association cannot be established. No statistically significant pulsations or modulation at the orbital period are detected. For a presumed detection, the implied γ-ray luminosity is ≲5% of its spin-down power. This indicates that PSR J1723-2837 is either one of the least efficient γ-ray producing MSPs or, if the detection is spurious, the γ-ray emission pattern is not directed toward us.

  20. THE QUASI-ROCHE LOBE OVERFLOW STATE IN THE EVOLUTION OF CLOSE BINARY SYSTEMS CONTAINING A RADIO PULSAR

    Energy Technology Data Exchange (ETDEWEB)

    Benvenuto, O. G.; De Vito, M. A. [Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata and Instituto de Astrofísica de La Plata (IALP), CCT-CONICET-UNLP. Paseo del Bosque S/N (B1900FWA), La Plata (Argentina); Horvath, J. E., E-mail: adevito@fcaglp.unlp.edu.ar, E-mail: foton@iag.usp.br [Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo R. do Matão 1226 (05508-090), Cidade Universitária, São Paulo SP (Brazil)

    2015-01-01

    We study the evolution of close binary systems formed by a normal (solar composition), intermediate-mass-donor star together with a neutron star. We consider models including irradiation feedback and evaporation. These nonstandard ingredients deeply modify the mass-transfer stages of these binaries. While models that neglect irradiation feedback undergo continuous, long-standing mass-transfer episodes, models including these effects suffer a number of cycles of mass transfer and detachment. During mass transfer, the systems should reveal themselves as low-mass X-ray binaries (LMXBs), whereas when they are detached they behave as binary radio pulsars. We show that at these stages irradiated models are in a Roche lobe overflow (RLOF) state or in a quasi-RLOF state. Quasi-RLOF stars have radii slightly smaller than their Roche lobes. Remarkably, these conditions are attained for an orbital period as well as donor mass values in the range corresponding to a family of binary radio pulsars known as ''redbacks''. Thus, redback companions should be quasi-RLOF stars. We show that the characteristics of the redback system PSR J1723-2837 are accounted for by these models. In each mass-transfer cycle these systems should switch from LMXB to binary radio pulsar states with a timescale of approximately one million years. However, there is recent and fast growing evidence of systems switching on far shorter, human timescales. This should be related to instabilities in the accretion disk surrounding the neutron star and/or radio ejection, still to be included in the model having the quasi-RLOF state as a general condition.

  1. Young Radio Pulsars in Galactic Globular Clusters

    CERN Document Server

    Boyles, Jason; Turk, Phil J; Mnatsakanov, Robert; Lynch, Ryan S; Ransom, Scott M; Freire, Paulo C; Belczynski, Khris

    2011-01-01

    Currently three isolated radio pulsars and one binary radio pulsar with no evidence of any previous recycling are known in 97 surveyed Galactic globular clusters. As pointed out by Lyne et al., the presence of these pulsars cannot be explained by core-collapse supernovae, as is commonly assumed for their counterparts in the Galactic disk. We apply a Bayesian analysis to the results from surveys for radio pulsars in globular clusters and find the number of potentially observable non-recycled radio pulsars present in all clusters to be -0.6. In this case, the potentially observable population of such young pulsars is 447^{+1420}_{-399} (the error bars give the 95% confidence interval) and their birth rate is 0.012^{+0.037}_{-0.010} pulsars per century. The mostly likely creation scenario to explain these pulsars is the electron capture supernova of a OMgNe white dwarf.

  2. Low-Mass X-Ray Binaries, Millisecond Radio Pulsars, and the Cosmic Star Formation Rate

    CERN Document Server

    White, N E; White, Nicholas E.; Ghosh, Pranab

    1998-01-01

    We report on the implications of the peak in the cosmic star-formation rate (SFR) at redshift z ~ 1.5 for the resulting population of low-mass X-ray binaries(LMXB) and for that of their descendants, the millisecond radio pulsars (MRP). Since the evolutionary timescales of LMXBs, their progenitors, and their descendants are thought be significant fractions of the time-interval between the SFR peak and the present epoch, there is a lag in the turn-on of the LMXB population, with the peak activity occurring at z ~ 0.5 - 1.0. The peak in the MRP population is delayed further, occurring at z < 0.5. We show that the discrepancy between the birthrate of LMXBs and MRPs, found under the assumption of a stead-state SFR, can be resolved for the population as a whole when the effects of a time-variable SFR are included. A discrepancy may persist for LMXBs with short orbital periods, although a detailed population synthesis will be required to confirm this. Further, since the integrated X-ray luminosity distribution of...

  3. A Radio Pulsar Search of the Gamma-ray Binaries LS I +61 303 and LS 5039

    CERN Document Server

    McSwain, M Virginia; Ransom, Scott M; Roberts, Mallory S E; Dougherty, Sean M; Pooley, Guy G

    2011-01-01

    LS I +61 303 and LS 5039 are exceptionally rare examples of HMXBs with MeV-TeV emission, making them two of only five known or proposed "gamma-ray binaries". There has been disagreement within the literature over whether these systems are microquasars, with stellar winds accreting onto a compact object to produce high energy emission and relativistic jets, or whether their emission properties might be better explained by a relativistic pulsar wind colliding with the stellar wind. Here we present an attempt to detect radio pulsars in both systems with the Green Bank Telescope. The upper limits of flux density are between 4.1-14.5 uJy, and we discuss the null results of the search. Our spherically symmetric model of the wind of LS 5039 demonstrates that any pulsar emission will be strongly absorbed by the dense wind unless there is an evacuated region formed by a relativistic colliding wind shock. LS I +61 303 contains a rapidly rotating Be star whose wind is concentrated near the stellar equator. As long as th...

  4. Observations of Binary and Millisecond Pulsars at Xinjiang Astronomical Observatory

    Indian Academy of Sciences (India)

    Jingbo Wang; Na Wang; Jianping Yuan; Zhiyong Liu

    2014-09-01

    We present the first results of radio timing observations of binary and millisecond pulsars in China. We have timed four binary pulsars for 9 years, using Nanshan 25-m radio telescope. The long time span has enabled us to determine their rotation and orbital parameters.

  5. Eccentric Binary Millisecond Pulsars

    CERN Document Server

    Freire, Paulo C C

    2009-01-01

    In this paper we review the recent discovery of several millisecond pulsars (MSPs) in eccentric binary systems. Timing these MSPs we were able to estimate (and in one case precisely measure) their masses. These results suggest that, as a class, MSPs have a much wider range of masses (1.3 to > 2 solar masses) than the normal and mildly recycled pulsars found in double neutron star (DNS) systems (1.25 < Mp < 1.44 solar masses). This is very likely to be due to the prolonged accretion episode that is thought to be required to form a MSP. The likely existence of massive MSPs makes them a powerful probe for understanding the behavior of matter at densities larger than that of the atomic nucleus; in particular, the precise measurement of the mass of PSR J1903+0327 ($1.67 +/- 0.01 solar masses) excludes several "soft" equations of state for dense matter.

  6. Coherent Radio Emission from Pulsars

    CERN Document Server

    Mitra, Dipanjan; Gil, Janusz

    2015-01-01

    We review a physical model where the high brightness temperature of 10$^{25}-10^{30}$ K observed in pulsar radio emission is explained by coherent curvature radiation excited in the relativistic electron-positron plasma in the pulsar magnetosphere.

  7. Millisecond Pulsars in Close Binaries

    CERN Document Server

    Tauris, Thomas M

    2015-01-01

    In this Habilitationsschrift (Habilitation thesis) I present my research carried out over the last four years at the Argelander Institute for Astronomy (AIfA) and the Max Planck Institute for Radio Astronomy (MPIfR). The thesis summarizes my main findings and has been written to fulfill the requirements for the Habilitation qualification at the University of Bonn. Although my work is mainly focused on the topic of millisecond pulsars (MSPs), there is a fairly broad spread of research areas ranging from the formation of neutron stars (NSs) in various supernova (SN) events, to their evolution, for example, via accretion processes in binary and triple systems, and finally to their possible destruction in merger events. The thesis is organized in the following manner: A general introduction to neutron stars and millisecond pulsars is given in Chapter 1. A selection of key papers published in 2011-2014 are presented in Chapters 2-10, ordered within five main research areas (ultra-stripped SNe in close binaries, ma...

  8. X-ray variability and evidence for pulsations from the unique radio pulsar/X-ray binary transition object FIRST J102347.6+003841

    NARCIS (Netherlands)

    Archibald, A.M.; Kaspi, V.M.; Bogdanov, S.; Hessels, J.W.T.; Stairs, I.H.; Ransom, S.M.; McLaughlin, M.A.

    2010-01-01

    We report on observations of the unusual neutron-star binary system FIRST J102347.6+003841 carried out using the XMM-Newton satellite. This system consists of a radio millisecond pulsar (PSR J1023+0038) in a 0.198 day orbit with a ~0.2 M sun Roche-lobe-filling companion and appears to have had an ac

  9. A Radio Pulsar Spinning at 716 Hz

    CERN Document Server

    Hessels, J W T; Stairs, I H; Freire, P C C; Kaspi, V M; Camilo, F; Hessels, Jason W.T.; Ransom, Scott M.; Stairs, Ingrid H.; Freire, Paulo C.C.; Kaspi, Victoria M.; Camilo, Fernando

    2006-01-01

    We have discovered a 716-Hz eclipsing binary radio pulsar in the globular cluster Terzan 5 using the Green Bank Telescope. It is the fastest-spinning neutron star ever found, breaking the 23-year-old record held by the 642-Hz pulsar B1937+21. The difficulty in detecting this pulsar, due to its very low flux density and high eclipse fraction (~40% of the orbit), suggests that even faster-spinning neutron stars exist. If the pulsar has a mass less than 2 Msun, then its radius is constrained by the spin rate to be < 16 km. The short period of this pulsar also constrains models that suggest gravitational radiation, through an r-mode instability, limits the maximum spin frequency of neutron stars.

  10. Gravitational Radiation from Compact Binary Pulsars

    CERN Document Server

    Antoniadis, John

    2014-01-01

    An outstanding question in modern Physics is whether general relativity (GR) is a complete description of gravity among bodies at macroscopic scales. Currently, the best experiments supporting this hypothesis are based on high-precision timing of radio pulsars. This chapter reviews recent advances in the field with a focus on compact binary millisecond pulsars with white-dwarf (WD) companions. These systems - if modeled properly - provide an unparalleled test ground for physically motivated alternatives to GR that deviate significantly in the strong-field regime. Recent improvements in observational techniques and advances in our understanding of WD interiors have enabled a series of precise mass measurements in such systems. These masses, combined with high-precision radio timing of the pulsars, result to stringent constraints on the radiative properties of gravity, qualitatively very different from what was available in the past.

  11. A Cosmic Census of Radio Pulsars with the SKA

    CERN Document Server

    Keane, E F; Kramer, M; Stappers, B W; Bates, S D; Burgay, M; Chatterjee, S; Champion, D J; Eatough, R P; Hessels, J W T; Janssen, G; Lee, K J; van Leeuwen, J; Margueron, J; Oertel, M; Possenti, A; Ransom, S; Theureau, G; Torne, P

    2015-01-01

    The Square Kilometre Array (SKA) will make ground breaking discoveries in pulsar science. In this chapter we outline the SKA surveys for new pulsars, as well as how we will perform the necessary follow-up timing observations. The SKA's wide field-of-view, high sensitivity, multi-beaming and sub-arraying capabilities, coupled with advanced pulsar search backends, will result in the discovery of a large population of pulsars. These will enable the SKA's pulsar science goals (tests of General Relativity with pulsar binary systems, investigating black hole theorems with pulsar-black hole binaries, and direct detection of gravitational waves in a pulsar timing array). Using SKA1-MID and SKA1-LOW we will survey the Milky Way to unprecedented depth, increasing the number of known pulsars by more than an order of magnitude. SKA2 will potentially find all the Galactic radio-emitting pulsars in the SKA sky which are beamed in our direction. This will give a clear picture of the birth properties of pulsars and of the gr...

  12. Gamma-ray binaries: pulsars in disguise ?

    CERN Document Server

    Dubus, G

    2006-01-01

    LS 5039 and LSI +61 303 are unique amongst high-mass X-ray binaries (HMXB) for their spatially-resolved radio emission and their counterpart at >GeV gamma-ray energies, canonically attributed to non-thermal particles in an accretion-powered relativistic jet. The only other HMXB known to emit very high energy (VHE) gamma-rays, PSR B1259-63, harbours a non-accreting millisecond pulsar. I investigate whether the interaction of the relativistic wind from a young pulsar with the wind from its stellar companion, as in PSR B1259-63, constitutes a viable scenario to explain the observations of LS 5039 and LSI +61 303. Emission would arise from the shocked pulsar wind material, which then flows away to large distances in a comet-shape tail, reproducing on a smaller scale what is observed in isolated, high motion pulsars interacting with the ISM. Simple expectations for the SED are derived and are shown to depend on few input parameters. Detailed modelling of the particle evolution is compared to the observations from ...

  13. An Eccentric Binary Millisecond Pulsar in the Galactic Plane

    Science.gov (United States)

    Champion, David J.; Ransom, Scott M.; Lazarus, Patrick; Camilo, Fernando; Bassa, Cess; Kaspi, Victoria M.; Nice, David J.; Freire, Paulo C. C.; Stairs, Ingrid H.; vanLeeuwen, Joeri; Stappers, Ben W.; Cordes, James M.; Hessels, Jason W. T.; Lorimer, Duncan R.; Arzoumanian, Zaven; Backer, Don C.; Bhat, N. D. Ramesh; Chatterjee, Shami; Cognard, Ismael; Deneva, Julia S.; Faucher-Giguere, Claude-Andre; Gaensler, Bryan M.; Han, JinLin; Jenet, Fredrick A.; Kasian, Laura

    2008-01-01

    Binary pulsar systems are superb probes of stellar and binary evolution and the physics of extreme environments. In a survey with the Arecibo telescope, we have found PSR J1903+0327, a radio pulsar with a rotational period of 2.15 milliseconds in a highly eccentric (e = 0.44) 95-day orbit around a solar mass (M.) companion. Infrared observations identify a possible main-sequence companion star. Conventional binary stellar evolution models predict neither large orbital eccentricities nor main-sequence companions around millisecond pulsars. Alternative formation scenarios involve recycling a neutron star in a globular cluster, then ejecting it into the Galactic disk, or membership in a hierarchical triple system. A relativistic analysis of timing observations of the pulsar finds its mass to be 1.74 +/- 0.04 Solar Mass, an unusually high value.

  14. An Eccentric Binary Millisecond Pulsar in the Galactic Plane

    CERN Document Server

    Champion, D J; Lazarus, P; Camilo, F; Bassa, C; Kaspi, V M; Nice, D J; Freire, P C C; Stairs, I H; Van Leeuwen, J; Stappers, B W; Cordes, J M; Hessels, J W T; Lorimer, D R; Arzoumanian, Z; Backer, D C; Bhat, N D R; Chatterjee, S; Cognard, I; Deneva, J S; Faucher-Giguere, C -A; Gaensler, B M; Han, J L; Jenet, F A; Kasian, L; Kondratiev, V I; Krämer, M; Lazio, J; McLaughlin, M A; Venkataraman, A; Vlemmings, W

    2008-01-01

    Binary pulsar systems are superb probes of stellar and binary evolution and the physics of extreme environments. In a survey with the Arecibo telescope, we have found PSR J1903+0327, a radio pulsar with a rotational period of 2.15 ms in a highly eccentric (e = 0.44) 95-day orbit around a solar mass companion. Infrared observations identify a possible main-sequence companion star. Conventional binary stellar evolution models predict neither large orbital eccentricities nor main-sequence companions around millisecond pulsars. Alternative formation scenarios involve recycling a neutron star in a globular cluster then ejecting it into the Galactic disk or membership in a hierarchical triple system. A relativistic analysis of timing observations of the pulsar finds its mass to be 1.74+/-0.04 Msun, an unusually high value.

  15. Radio Pulsars: The Neutron Star Population & Fundamental Physics

    CERN Document Server

    Kaspi, Victoria M

    2016-01-01

    Radio pulsars are unique laboratories for a wide range of physics and astrophysics. Understanding how they are created, how they evolve and where we find them in the Galaxy, with or without binary companions, is highly constraining of theories of stellar and binary evolution. Pulsars' relationship with a recently discovered variety of apparently different classes of neutron stars is an interesting modern astrophysical puzzle which we consider in Part I of this review. Radio pulsars are also famous for allowing us to probe the laws of nature at a fundamental level. They act as precise cosmic clocks and, when in a binary system with a companion star, provide indispensable venues for precision tests of gravity. The different applications of radio pulsars for fundamental physics will be discussed in Part II. We finish by making mention of the newly discovered class of astrophysical objects, the Fast Radio Bursts, which may or may not be related to radio pulsars or neutron stars, but which were discovered in obser...

  16. The Aid of Optical Studies in Understanding Millisecond Pulsar Binaries

    CERN Document Server

    Wadiasingh, Zorawar; Venter, Christo; Boettcher, Markus

    2016-01-01

    A large number of new "black widow" and "redback" energetic millisecond pulsars with irradiated stellar companions have been discovered through radio and optical searches of unidentified \\textit{Fermi} sources. Synchrotron emission, from particles accelerated up to several TeV in the intrabinary shock, exhibits modulation at the binary orbital period. Our simulated double-peaked X-ray light curves modulated at the orbital period, produced by relativistic Doppler-boosting along the intrabinary shock, are found to qualitatively match those observed in many sources. In this model, redbacks and transitional pulsar systems where the double-peaked X-ray light curve is observed at inferior conjunction have intrinsically different shock geometry than other millisecond pulsar binaries where the light curve is centered at superior conjunction. We discuss, and advocate, how current and future optical observations may aid in constraining the emission geometry, intrabinary shock and the unknown physics of pulsar winds.

  17. Binary Millisecond Pulsar Discovery via Gamma-Ray Pulsations

    CERN Document Server

    Pletsch, H J; Fehrmann, H; Allen, B; Kramer, M; Aulbert, C; Ackermann, M; Ajello, M; de Angelis, A; Atwood, W B; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Bechtol, K; Bellazzini, R; Borgland, A W; Bottacini, E; Brandt, T J; Bregeon, J; Brigida, M; Bruel, P; Buehler, R; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Cecchi, C; Celik, Ö; Charles, E; Chaves, R C G; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; Cutini, S; D'Ammando, F; Dermer, C D; Digel, S W; Drell, P S; Drlica-Wagner, A; Dubois, R; Dumora, D; Favuzzi, C; Ferrara, E C; Franckowiak, A; Fukazawa, Y; Fusco, P; Gargano, F; Gehrels, N; Germani, S; Giglietto, N; Giordano, F; Giroletti, M; Godfrey, G; Grenier, I A; Grondin, M -H; Grove, J E; Guiriec, S; Hadasch, D; Hanabata, Y; Harding, A K; Hartog, P R den; Hayashida, M; Hays, E; Hill, A B; Hou, X; Hughes, R E; Johannesson, G; Jackson, M S; Jogler, T; Johnson, A S; Johnson, W N; Kataoka, J; Kerr, M; Knödlseder, J; Kuss, M; Lande, J; Larsson, S; Latronico, L; Lemoine-Goumard, M; Longo, F; Loparco, F; Lovellette, M N; Lubrano, P; Massaro, F; Mayer, M; Mazziotta, M N; McEnery, J E; Mehault, J; Michelson, P F; Mitthumsiri, W; Mizuno, T; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nakamori, T; Nemmen, R; Nuss, E; Ohno, M; Ohsugi, T; Omodei, N; Orienti, M; Orlando, E; de Palma, F; Paneque, D; Perkins, J S; Piron, F; Pivato, G; Porter, T A; Raino, S; Rando, R; Ray, P S; Razzano, M; Reimer, A; Reimer, O; Reposeur, T; Ritz, S; Romani, R W; Romoli, C; Sanchez, D A; Parkinson, P M Saz; Schulz, A; Sgro, C; Silva, E do Couto e; Siskind, E J; Smith, D A; Spandre, G; Spinelli, P; Suson, D J; Takahashi, H; Tanaka, T; Thayer, J B; Thayer, J G; Thompson, D J; Tibaldo, L; Tinivella, M; Troja, E; Usher, T L; Vandenbroucke, J; Vasileiou, V; Vianello, G; Vitale, V; Waite, A P; Winer, B L; Wood, K S; Wood, M; Yang, Z; Zimmer, S; 10.1126/science.1229054

    2012-01-01

    Millisecond pulsars (MSPs), old neutron stars spun-up by accreting matter from a companion star, can reach high rotation rates of hundreds of revolutions per second. Until now, all such "recycled" rotation-powered pulsars have been detected by their spin-modulated radio emission. In a computing-intensive blind search of gamma-ray data from the Fermi Large Area Telescope (with partial constraints from optical data), we detected a 2.5-millisecond pulsar, PSR J1311-3430. This unambiguously explains a formerly unidentified gamma-ray source that had been a decade-long enigma, confirming previous conjectures. The pulsar is in a circular orbit with an orbital period of only 93 minutes, the shortest of any spin-powered pulsar binary ever found.

  18. Searching for Pulsars in Close Binary Systems

    CERN Document Server

    Jouteux, S; Stappers, B W; Jonker, P; Van der Klis, M

    2001-01-01

    We present a detailed mathematical analysis of the Fourier response of binary pulsar signals whose frequencies are modulated by circular orbital motion. The fluctuation power spectrum of such signals is found to be \

  19. Radio-quiet Gamma-ray Pulsars

    Science.gov (United States)

    Lin, Lupin Chun-Che

    2016-09-01

    A radio-quiet γ-ray pulsar is a neutron star that has significant γ-ray pulsation but without observed radio emission or only limited emission detected by high sensitivity radio surveys. The launch of the Fermi spacecraft in 2008 opened a new epoch to study the population of these pulsars. In the 2nd Fermi Large Area Telescope catalog of γ-ray pulsars, there are 35 (30 % of the 117 pulsars in the catalog) known samples classified as radio-quiet γ-ray pulsars with radio flux density (S1400) of less than 30 μJy. Accompanying the observations obtained in various wavelengths, astronomers not only have the opportunity to study the emitting nature of radio-quiet γ-ray pulsars but also have proposed different models to explain their radiation mechanism. This article will review the history of the discovery, the emission properties, and the previous efforts to study pulsars in this population. Some particular cases known as Geminga-like pulsars (e.g., PSR J0633+1746, PSR J0007+7303, PSR J2021+4026, and so on) are also specified to discuss their common and specific features.

  20. On the disruption of pulsar and X-ray binaries in globular clusters

    CERN Document Server

    Verbunt, Frank

    2013-01-01

    The stellar encounter rate Gamma has been shown to be strongly correlated with the number of X-ray binaries in clusters and also to the number of radio pulsars. However, the pulsar populations in different clusters show remarkably different characteristics: in some GCs the population is dominated by binary systems, in others by single pulsars and exotic systems that result from exchange encounters. In this paper, we describe a second dynamical parameter for globular clusters, the encounter rate for a single binary, gamma. We find that this parameter provides a good characterization of the differences between the pulsar populations of different globular clusters. The higher gamma is for any particular globular cluster the more isolated pulsars and products of exchange interactions are observed. Furthermore, we also find that slow and "young" pulsars are found almost exclusively in clusters with a high gamma; this suggests that these kinds of objects are formed by the disruption of X-ray binaries, thus halting ...

  1. Properties and geometry of radio pulsar emission

    NARCIS (Netherlands)

    Smits, Johannes Martinus

    2006-01-01

    This thesis consists of a number of studies on the radio emission of pulsars. The central topics are polarisation and multi frequency observations, which both lead to important information on the geometry of the emission. The first chapter introduces different aspects of pulsars that are related to

  2. Upper limits on gravitational wave emission from 78 radio pulsars

    CERN Document Server

    Abbott, B; Adhikari, R; Agresti, J; Ajith, P; Allen, B; Amin, R; Anderson, S B; Anderson, W G; Arain, M; Araya, M; Armandula, H; Ashley, M; Aston, S; Aufmuth, P; Aulbert, C; Babak, S; Ballmer, S; Bantilan, H; Barish, B C; Barker, C; Barker, D; Barr, B; Barriga, P; Barton, M; Bayer, K; Betzwieser, J; Beyersdorf, P T; Bhawal, B; Bilenko, I A; Billingsley, G; Biswas, R; Black, E; Blackburn, K; Blackburn, L; Blair, D; Bland, B; Bogenstahl, J; Bogue, L; Bork, R; Boschi, V; Bose, S; Brady, P R; Braginsky, V B; Brau, J E; Brinkmann, M; Brooks, A; Brown, D A; Bullington, A; Bunkowski, A; Buonanno, A; Burmeister, O; Busby, D; Byer, R L; Cadonati, L; Cagnoli, G; Camp, J B; Cannizzo, J; Cannon, K; Cantley, C A; Cao, J; Cardenas, L; Castaldi, G; Cepeda, C; Chalkey, E; Charlton, P; Chatterji, S; Chelkowski, S; Chen, Y; Chiadini, F; Christensen, N; Clark, J; Cochrane, P; Cokelaer, T; Coldwell, R; Conte, R; Cook, D; Corbitt, T; Coyne, D; Creighton, J D E; Croce, R P; Crooks, D R M; Cruise, A M; Cumming, A; D'Ambrosio, E; Dalrymple, J; Danzmann, K; Davies, G; De Bra, D; DeSalvo, R; Degallaix, J; Degree, M; Demma, T; Dergachev, V; Desai, S; Dhurandhar, S V; Di Credico, A; Dickson, J; Diederichs, G; Dietz, A; Doomes, E E; Drever, R W P; Dumas, J C; Dupuis, R J; Dwyer, J G; Díaz, M; Ehrens, P; Espinoza, E; Etzel, T; Evans, M; Evans, T; Fairhurst, S; Fan, Y; Fazi, D; Fejer, M M; Finn, L S; Fiumara, V; Fotopoulos, N; Franzen, A; Franzen, K Y; Freise, A; Frey, R E; Fricke, T; Fritschel, P; Frolov, V V; Fyffe, M; Galdi, V; Garofoli, J; Gholami, I; Giaime, J A; Giampanis, S; Giardina, K D; Goda, K; Goetz, E; Goggin, L; González, G; Gossler, S; Grant, A; Gras, S; Gray, C; Gray, M; Greenhalgh, J; Gretarsson, A M; Grosso, R; Grote, H; Grünewald, S; Gustafson, R; Günther, M; Hage, B; Hammer, D; Hanna, C; Hanson, J; Harms, J; Harry, G; Harstad, E; Hayler, T; Heefner, J; Heng, I S; Heptonstall, A; Heurs, M; Hewitson, M; Hild, S; Hirose, E; Hoak, D; Hosken, D; Hough, J; Hoyland, D; Huttner, S H; Ingram, D; Innerhofer, E; Ito, M; Itoh, Y; Ivanov, A; Johnson, B; Johnson, W W; Jones, D I; Jones, G; Jones, R; Ju, L; Kalmus, Peter Ignaz Paul; Kalogera, V; Kasprzyk, D; Katsavounidis, E; Kawabe, K; Kawamura, S; Kawazoe, F; Kells, W; Keppel, D G; Khalili, F Ya; Kim, C; King, P; Kissel, J S; Klimenko, S; Kokeyama, K; Kondrashov, V; Kopparapu, R K; Kozak, D; Krishnan, B; Krämer, M; Kwee, P; Lam, P K; Landry, M; Lantz, B; Lazzarini, A; Lei, M; Leiner, J; Leonhardt, V; Leonor, I; Libbrecht, K; Lindquist, P; Lockerbie, N A; Longo, M; Lormand, M; Lubinski, M; Luck, H; Lyne, A G; MacInnis, M; Machenschalk, B; Mageswaran, M; Mailand, K; Malec, M; Mandic, V; Marano, S; Marka, S; Markowitz, J; Maros, E; Martin, I; Marx, J N; Mason, K; Matone, L; Matta, V; Mavalvala, N; McCarthy, R; McClelland, D E; McGuire, S C; McHugh, M; McKenzie, K; McWilliams, S; Meier, T; Melissinos, A C; Mendell, G; Mercer, R A; Meshkov, S; Messaritaki, E; Messenger, C J; Meyers, D; Mikhailov, E; Mitra, S; Mitrofanov, V P; Mitselmakher, G; Mittleman, R; Miyakawa, O; Mohanty, S; Moreno, G; Mossavi, K; Mow Lowry, C; Moylan, A; Mukherjee, S; Muller-Ebhardt, H; Munch, J; Murray, P; Myers, E; Myers, J; Müller, G; Newton, G; Nishizawa, A; Numata, K; O'Reilly, B; O'Shaughnessy, R; Ottaway, D J; Overmier, H; Owen, B J; Pan, Y; Papa, M A; Parameshwaraiah, V; Patel, P; Pedraza, M; Penn, S; Pierro, V; Pinto, I M; Pitkin, M; Pletsch, H; Plissi, M V; Postiglione, F; Prix, R; Quetschke, V; Raab, F; Rabeling, D; Radkins, H; Rahkola, R; Rainer, N; Rakhmanov, M; Ray-Majumder, S; Re, V; Rehbein, H; Reid, S; Reitze, D H; Ribichini, L; Riesen, R; Riles, K; Rivera, B; Robertson, N A; Robinson, C; Robinson, E L; Roddy, S; Rodríguez, A; Rogan, A M; Rollins, J; Romano, J D; Romie, J; Route, R; Rowan, S; Ruet, L; Russell, P; Ryan, K; Rüdiger, A; Sakata, S; Samidi, M; Sancho de la Jordana, L; Sandberg, V; Sannibale, V; Saraf, S; Sarin, P; Sathyaprakash, B S; Sato, S; Saulson, P R; Savage, R; Savov, P; Schediwy, S; Schilling, R; Schnabel, R; Schofield, R; Schutz, B F; Schwinberg, P; Scott, S M; Searle, A C; Sears, B; Seifert, F; Sellers, D; Sengupta, A S; Shawhan, P; Shoemaker, D H; Sibley, A; Sidles, J A; Siemens, X; Sigg, D; Sinha, S; Sintes, A M; Slagmolen, B; Slutsky, J; Smith, J R; Smith, M R; Somiya, K; Strain, K A; Strom, D M; Stuver, A; Summerscales, T Z; Sun, K X; Sung, M; Sutton, P J; Takahashi, H; Tanner, D B; Taylor, R; Thacker, J; Thorne, K A; Thorne, K S; Thüring, A; Tokmakov, K V; Torres, C; Torrie, C; Traylor, G; Trias, M; Tyler, W; Ugolini, D W; Urbanek, K; Vahlbruch, H; Vallisneri, M; Van Den Broeck, C; Varvella, M; Vass, S; Vecchio, A; Veitch, J; Veitch, P; Villar, A; Vorvick, C; Vyachanin, S P; Waldman, S J; Wallace, L; Ward, H; Ward, R; Watts, K; Weidner, A; Weinert, M; Weinstein, A; Weiss, R; Wen, S; Wette, K; Whelan, J T; Whitcomb, S E; Whiting, B F; Wilkinson, C

    2007-01-01

    We present upper limits on the gravitational wave emission from 78 radio pulsars based on data from the third and fourth science runs of the LIGO and GEO600 gravitational wave detectors. The data from both runs have been combined coherently to maximise sensitivity. For the first time pulsars within binary (or multiple) systems have been included in the search by taking into account the signal modulation due to their orbits. Our upper limits are therefore the first measured for 56 of these pulsars. For the remaining 22, our results improve on previous upper limits by up to a factor of 10. For example, our tightest upper limit on the gravitational strain is 3.2e-25 for PSRJ1603-7202, and the equatorial ellipticity of PSRJ2124-3358 is less than 10e-6. Furthermore, our strain upper limit for the Crab pulsar is only three times greater than the fiducial spin-down limit.

  3. The Velocity Distribution of Isolated Radio Pulsars

    CERN Document Server

    Arzoumanian, Z; Cordes, J M

    2002-01-01

    (Abridged) We infer the velocity distribution of radio pulsars by modelling their birth, evolution, and detection in large-scale 0.4 GHz pulsar surveys, and by comparing model distributions of measurable pulsar properties with survey data using a likelihood function. We test models that characterize a population's birth rate, luminosity, shutoff of radio emission, birth locations, and birth velocities. We infer that the radio beam luminosity (i) is comparable to the energy flux of relativistic particles in models for spin-driven magnetospheres, signifying that radio emission losses reach nearly 100% for the oldest pulsars; and (ii) scales approximately as sqrt(Edot) which, in magnetosphere models, is proportional to the voltage drop available for acceleration of particles. We find that a two-component velocity distribution with characteristic velocities of 90 km/s and 500 km/s is greatly preferred to any one-component distribution. We explore some consequences of the preferred birth velocity distribution: (i)...

  4. Multiwavelength observations of the transitional millisecond pulsar binary XSS J12270-4859

    NARCIS (Netherlands)

    de Martino, D.; Papitto, A.; Belloni, T.; Burgay, M.; De Ona Wilhelmi, E.; Li, J.; Pellizzoni, A.; Possenti, A.; Rea, N.; Torres, D.F.

    2015-01-01

    We present an analysis of X-ray, ultraviolet and optical/near-IR photometric data of the transitional millisecond pulsar binary XSS J12270−4859, obtained at different epochs after the transition to a rotation-powered radio pulsar state. The observations, while confirming the large-amplitude orbital

  5. An analysis of radio pulsar nulling statistics

    Science.gov (United States)

    Biggs, James D.

    1992-01-01

    Survival analysis methods are used to seek correlations between the fraction of null pulsars and other pulsar characteristics for an ensemble of 72 radio pulsars. The strongest correlation is found between the null fraction and the pulse period, suggesting that nulling is a manifestation of a faltering emission mechanism. Correlations are also found between the fraction of null pulses and other parameters that have a strong dependence on the pulse period. The results presented here suggest that nulling is broad-band and may ultimately be explained in terms of polar cap models of pulsar emission.

  6. On magnetic fields of radio pulsars

    CERN Document Server

    Nikitina, E B

    2016-01-01

    We used the magneto-dipole radiation mechanism for the braking of radio pulsars to calculate the new values of magnetic inductions at the surfaces of neutron stars. For this aim we estimated the angles ? between the rotation axis and the magnetic moment of the neutron star for 376 radio pulsars using three different methods. It was shown that there was the predominance of small inclinations of the magnetic axes. Using the obtained values of the angle ? we calculated the equatorial magnetic inductions for pulsars considered. These inductions are several times higher as a rule than corresponding values in the known catalogs.

  7. Binary pulsars as dark-matter probes

    CERN Document Server

    Pani, Paolo

    2015-01-01

    During the motion of a binary pulsar around the galactic center, the pulsar and its companion experience a wind of dark-matter particles that can affect the orbital motion through dynamical friction. We show that this effect produces a characteristic seasonal modulation of the orbit and causes a secular change of the orbital period whose magnitude can be well within the astonishing precision of various binary-pulsar observations. Our analysis is valid for binary systems with orbital period longer than a day. By comparing this effect with pulsar-timing measurements, it is possible to derive model-independent upper bounds on the dark-matter density at different distances $D$ from the galactic center. For example, the precision timing of J1713+0747 imposes $\\rho_{\\rm DM}\\lesssim 10^5\\,{\\rm GeV/cm}^3$ at $D\\approx7\\,{\\rm kpc}$. The detection of a binary pulsar at $D\\lesssim 10\\,{\\rm pc}$ could provide stringent constraints on dark-matter halo profiles and on growth models of the central black hole. The Square Kil...

  8. Nature of microstructure in pulsar radio emission

    CERN Document Server

    Machabeli, G Z; Melikidze, G I; Shapakidze, D; Machabeli, George; Khechinashvili, David; Melikidze, George; Shapakidze, David

    2000-01-01

    We present a model for microstructure in pulsar radio emission. We propose that micropulses result from the alteration of the radio wave generation region by nearly transverse drift waves propagating across the pulsar magnetic field and encircling the bundle of the open magnetic field lines. It is demonstrated that such waves can modify significantly curvature of these dipolar field lines. This in turn affects strongly fulfillment of the resonance conditions necessary for the excitation of radio waves. The time-scale of micropulses is therefore determined by the wavelength of drift waves. Main features of the microstructure are naturally explained in the frame of this model.

  9. On Low Mass X-ray Binaries and Millisecond Pulsar

    CERN Document Server

    Burderi, Luciano

    2013-01-01

    The detection, in 1998, of the first Accreting Millisecond Pulsar, started an exciting season of continuing discoveries in the fashinating field of compact binary systems harbouring a neutron star. Indeed, in these last three lustres, thanks to the extraordinary performances of astronomical detectors, on ground as well as on board of satellites, mainly in the Radio, Optical, X-ray, and Gamma-ray bands, astrophysicists had the opportunity to thoroughly investigate the so-called Recycling Scenario: the evolutionary path leading to the formation of a Millisecond Radio Pulsar. The most intriguing phase is certainly the spin-up stage during which, because of the accretion of matter and angular momentum, the neutron star accumulates an extraordinary amount of mechanical rotational energy, up to one percent of its whole rest-mass energy. These millisecond spinning neutron stars are truly extreme physical objects: General and Special Relativity are fully in action, since their surfaces, attaining speeds close to one ...

  10. Evolution of redback radio pulsars in globular clusters

    Science.gov (United States)

    Benvenuto, O. G.; De Vito, M. A.; Horvath, J. E.

    2017-01-01

    Context. We study the evolution of close binary systems composed of a normal, intermediate mass star and a neutron star considering a chemical composition typical of that present in globular clusters (Z = 0.001). Aims: We look for similarities and differences with respect to solar composition donor stars, which we have extensively studied in the past. As a definite example, we perform an application on one of the redbacks located in a globular cluster. Methods: We performed a detailed grid of models in order to find systems that represent the so-called redback binary radio pulsar systems with donor star masses between 0.6 and 2.0 solar masses and orbital periods in the range 0.2-0.9 d. Results: We find that the evolution of these binary systems is rather similar to those corresponding to solar composition objects, allowing us to account for the occurrence of redbacks in globular clusters, as the main physical ingredient is the irradiation feedback. Redback systems are in the quasi-RLOF state, that is, almost filling their corresponding Roche lobe. During the irradiation cycle the system alternates between semi-detached and detached states. While detached the system appears as a binary millisecond pulsar, called a redback. Circumstellar material, as seen in redbacks, is left behind after the previous semi-detached phase. Conclusions: The evolution of binary radio pulsar systems considering irradiation successfully accounts for, and provides a way for, the occurrence of redback pulsars in low-metallicity environments such as globular clusters. This is the case despite possible effects of the low metal content of the donor star that could drive systems away from redback configuration.

  11. Radio polarimetry of Galactic centre pulsars

    CERN Document Server

    Schnitzeler, D H F M; Ferrière, K; Kramer, M; Lee, K J; Noutsos, A; Shannon, R M

    2016-01-01

    To study the strength and structure of the magnetic field in the Galactic centre (GC) we measured Faraday rotation of the radio emission of pulsars which are seen towards the GC. Three of these pulsars have the largest rotation measures (RMs) observed in any Galactic object with the exception of Sgr A*. Their large dispersion measures, RMs and the large RM variation between these pulsars and other known objects in the GC implies that the pulsars lie in the GC and are not merely seen in projection towards the GC. The large RMs of these pulsars indicate large line-of-sight magnetic field components between ~ 16-33 microgauss; combined with recent model predictions for the strength of the magnetic field in the GC this implies that the large-scale magnetic field has a very small inclination angle with respect to the plane of the sky (~ 12 degrees). Foreground objects like the Radio Arc or possibly an ablated, ionized halo around the molecular cloud G0.11-0.11 could contribute to the large RMs of two of the pulsar...

  12. Birth and Evolution of Isolated Radio Pulsars

    CERN Document Server

    Faucher-Giguere, C A

    2005-01-01

    We investigate the birth and evolution of Galactic isolated radio pulsars. We begin by estimating their birth space velocity distribution from proper motion measurements of Brisken et al. (2002, 2003). We find no evidence for multimodality of the distribution and favor one in which the absolute one-dimensional velocity components are exponentially distributed and with a three-dimensional mean velocity of 380^{+40}_{-60} km s^-1. We then proceed with a Monte Carlo-based population synthesis, modelling the birth properties of the pulsars, their time evolution, and their detection in the Parkes and Swinburne Multibeam surveys. We present a population model that appears generally consistent with the observations. Our results suggest that pulsars are born in the spiral arms, with a Galactocentric radial distribution that is well described by the functional form proposed by Yusifov & Kucuk (2004), in which the pulsar surface density peaks at radius ~3 kpc. The birth spin period distribution extends to several h...

  13. An X-ray View of Radio Millisecond Pulsars

    CERN Document Server

    Bogdanov, Slavko

    2007-01-01

    In recent years, X-ray observations with Chandra and XMM-Newton have significantly increased our understanding of rotation-powered (radio) millisecond pulsars (MSPs). Deep Chandra studies of several globular clusters have detected X-ray counterparts to a host of MSPs, including 19 in 47 Tuc alone. These surveys have revealed that most MSPs exhibit thermal emission from their heated magnetic polar caps. Realistic models of this thermal X-ray emission have provided important insight into the basic physics of pulsars and neutron stars. In addition, intrabinary shock X-ray radiation observed in ``black-widow'' and peculiar globular cluster ``exchanged'' binary MSPs give interesting insight into MSP winds and relativistic shock. Thus, the X-ray band contains valuable information regarding the basic properties of MSPs that are not accesible by radio timing observations.

  14. On the connection between accreting X-ray and radio millisecond pulsars

    CERN Document Server

    Tauris, T M

    2012-01-01

    For many years it has been recognized that the terminal stages of mass transfer in a low-mass X-ray binary (LMXB) should cause the magnetosphere of the accreting neutron star to expand, leading to a braking torque acting on the spinning pulsar. After the discovery of radio millisecond pulsars (MSPs) it was therefore somewhat a paradox (e.g. Ruderman et al. 1989) how these pulsars could retain their fast spins following the Roche-lobe decoupling phase, RLDP. Here I present a solution to this so-called "turn-off problem" which was recently found by combining binary stellar evolution models with torque computations (Tauris 2012). The solution is that during the RLDP the spin equilibrium of the pulsar is broken and therefore it remains a fast spinning object. I briefly discuss these findings in view of the two observed spin distributions in the populations of accreting X-ray millisecond pulsars (AXMSPs) and radio MSPs.

  15. Inferring the Composition of Super-Jupiter Mass Companions of Pulsars with Radio Line Spectroscopy

    Science.gov (United States)

    Ray, Alak; Loeb, Abraham

    2017-02-01

    We propose using radio line spectroscopy to detect molecular absorption lines (such as OH at 1.6–1.7 GHz) before and after the total eclipse of black widow and other short orbital period binary pulsars with low-mass companions. The companion in such a binary may be ablated away by energetic particles and high-energy radiation produced by the pulsar wind. The observations will probe the eclipsing wind being ablated by the pulsar and constrain the nature of the companion and its surroundings. Maser emission from the interstellar medium stimulated by a pulsar beam might also be detected from the intrabinary medium. The short temporal resolution allowed by the millisecond pulsars can probe this medium with the high angular resolution of the pulsar beam.

  16. 1974: the discovery of the first binary pulsar

    CERN Document Server

    Damour, Thibault

    2014-01-01

    The 1974 discovery, by Russell A. Hulse and Joseph H. Taylor, of the first binary pulsar PSR 1913+16, opened up new possibilities for the study of relativistic gravity. PSR 1913+16, as well as several other binary pulsars, provided {\\it direct} observational proofs that gravity propagates at the velocity of light and has a quadrupolar structure. Binary pulsars also provided accurate tests of the strong-field regime of relativistic gravity. General Relativity has passed all the binary pulsar tests with flying colors. The discovery of binary pulsars had also very important consequences for astrophysics: accurate measurement of neutron star masses, improved understanding of the possible evolution scenarios for the co-evolution of binary stars, proof of the existence of binary neutron stars emitting gravitational waves for hundreds of millions of years, before coalescing in catastrophic events probably leading to an important emission of electromagnetic radiation and neutrinos. This article reviews the history of...

  17. A New Class of Radio Quiet Pulsars

    CERN Document Server

    Baring, M G; Baring, Matthew G.; Harding, Alice K.

    1997-01-01

    The complete absence of radio pulsars with periods exceeding a few seconds has lead to the popular notion of the existence of a high $P$ death line. In the standard picture, beyond this boundary, pulsars with low spin rates cannot accelerate particles above the stellar surface to high enough energies to initiated pair cascades through curvature radiation, and the pair creation needed for radio emission is strongly suppressed. In this paper we postulate the existence of another pulsar ``death line,'' corresponding to high magnetic fields $B$ in the upper portion of the $\\dot{P}$--$P$ diagram, a domain where few radio pulsars are observed. The origin of this high $B$ boundary, which occurs when $B$ becomes comparable to or exceeds $10^{13}$ Gauss, is again due to the suppression of magnetic pair creation $\\gamma\\to e^+e^-$, but in this instance, primarily because of ineffective competition with the exotic QED process of magnetic photon splitting. This paper describes the origin, shape and position of the new ``...

  18. Stokes tomography of radio pulsar magnetospheres. II. Millisecond pulsars

    CERN Document Server

    Chung, C T Y

    2011-01-01

    The radio polarization characteristics of millisecond pulsars (MSPs) differ significantly from those of non-recycled pulsars. In particular, the position angle (PA) swings of many MSPs deviate from the S-shape predicted by the rotating vector model, even after relativistic aberration is accounted for, indicating that they have non-dipolar magnetic geometries, likely due to a history of accretion. Stokes tomography uses phase portraits of the Stokes parameters as a diagnostic tool to infer a pulsar's magnetic geometry and orientation. This paper applies Stokes tomography to MSPs, generalizing the technique to handle interpulse emission. We present an atlas of look-up tables for the Stokes phase portraits and PA swings of MSPs with current-modified dipole fields, filled core and hollow cone beams, and two empirical linear polarization models. We compare our look-up tables to data from 15 MSPs and find that the Stokes phase portraits for a current-modified dipole approximately match several MSPs whose PA swings ...

  19. Upper limits on gravitational wave emission from 78 radio pulsars

    Science.gov (United States)

    Abbott, B.; Abbott, R.; Adhikari, R.; Agresti, J.; Ajith, P.; Allen, B.; Amin, R.; Anderson, S. B.; Anderson, W. G.; Arain, M.; Araya, M.; Armandula, H.; Ashley, M.; Aston, S.; Aufmuth, P.; Aulbert, C.; Babak, S.; Ballmer, S.; Bantilan, H.; Barish, B. C.; Barker, C.; Barker, D.; Barr, B.; Barriga, P.; Barton, M. A.; Bayer, K.; Belczynski, K.; Betzwieser, J.; Beyersdorf, P. T.; Bhawal, B.; Bilenko, I. A.; Billingsley, G.; Biswas, R.; Black, E.; Blackburn, K.; Blackburn, L.; Blair, D.; Bland, B.; Bogenstahl, J.; Bogue, L.; Bork, R.; Boschi, V.; Bose, S.; Brady, P. R.; Braginsky, V. B.; Brau, J. E.; Brinkmann, M.; Brooks, A.; Brown, D. A.; Bullington, A.; Bunkowski, A.; Buonanno, A.; Burmeister, O.; Busby, D.; Butler, W. E.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Camp, J. B.; Cannizzo, J.; Cannon, K.; Cantley, C. A.; Cao, J.; Cardenas, L.; Carter, K.; Casey, M. M.; Castaldi, G.; Cepeda, C.; Chalkey, E.; Charlton, P.; Chatterji, S.; Chelkowski, S.; Chen, Y.; Chiadini, F.; Chin, D.; Chin, E.; Chow, J.; Christensen, N.; Clark, J.; Cochrane, P.; Cokelaer, T.; Colacino, C. N.; Coldwell, R.; Conte, R.; Cook, D.; Corbitt, T.; Coward, D.; Coyne, D.; Creighton, J. D. E.; Creighton, T. D.; Croce, R. P.; Crooks, D. R. M.; Cruise, A. M.; Cumming, A.; Dalrymple, J.; D'Ambrosio, E.; Danzmann, K.; Davies, G.; Debra, D.; Degallaix, J.; Degree, M.; Demma, T.; Dergachev, V.; Desai, S.; Desalvo, R.; Dhurandhar, S.; Díaz, M.; Dickson, J.; di Credico, A.; Diederichs, G.; Dietz, A.; Doomes, E. E.; Drever, R. W. P.; Dumas, J.-C.; Dupuis, R. J.; Dwyer, J. G.; Ehrens, P.; Espinoza, E.; Etzel, T.; Evans, M.; Evans, T.; Fairhurst, S.; Fan, Y.; Fazi, D.; Fejer, M. M.; Finn, L. S.; Fiumara, V.; Fotopoulos, N.; Franzen, A.; Franzen, K. Y.; Freise, A.; Frey, R.; Fricke, T.; Fritschel, P.; Frolov, V. V.; Fyffe, M.; Galdi, V.; Ganezer, K. S.; Garofoli, J.; Gholami, I.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Goda, K.; Goetz, E.; Goggin, L.; González, G.; Gossler, S.; Grant, A.; Gras, S.; Gray, C.; Gray, M.; Greenhalgh, J.; Gretarsson, A. M.; Grosso, R.; Grote, H.; Grunewald, S.; Guenther, M.; Gustafson, R.; Hage, B.; Hammer, D.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G.; Harstad, E.; Hayler, T.; Heefner, J.; Heng, I. S.; Heptonstall, A.; Heurs, M.; Hewitson, M.; Hild, S.; Hirose, E.; Hoak, D.; Hosken, D.; Hough, J.; Howell, E.; Hoyland, D.; Huttner, S. H.; Ingram, D.; Innerhofer, E.; Ito, M.; Itoh, Y.; Ivanov, A.; Jackrel, D.; Johnson, B.; Johnson, W. W.; Jones, D. I.; Jones, G.; Jones, R.; Ju, L.; Kalmus, P.; Kalogera, V.; Kasprzyk, D.; Katsavounidis, E.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Kells, W.; Keppel, D. G.; Khalili, F. Ya.; Kim, C.; King, P.; Kissel, J. S.; Klimenko, S.; Kokeyama, K.; Kondrashov, V.; Kopparapu, R. K.; Kozak, D.; Krishnan, B.; Kwee, P.; Lam, P. K.; Landry, M.; Lantz, B.; Lazzarini, A.; Lee, B.; Lei, M.; Leiner, J.; Leonhardt, V.; Leonor, I.; Libbrecht, K.; Lindquist, P.; Lockerbie, N. A.; Longo, M.; Lormand, M.; Lubiński, M.; Lück, H.; Machenschalk, B.; Macinnis, M.; Mageswaran, M.; Mailand, K.; Malec, M.; Mandic, V.; Marano, S.; Márka, S.; Markowitz, J.; Maros, E.; Martin, I.; Marx, J. N.; Mason, K.; Matone, L.; Matta, V.; Mavalvala, N.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McHugh, M.; McKenzie, K.; McNabb, J. W. C.; McWilliams, S.; Meier, T.; Melissinos, A.; Mendell, G.; Mercer, R. A.; Meshkov, S.; Messaritaki, E.; Messenger, C. J.; Meyers, D.; Mikhailov, E.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Miyakawa, O.; Mohanty, S.; Moreno, G.; Mossavi, K.; Mowlowry, C.; Moylan, A.; Mudge, D.; Mueller, G.; Mukherjee, S.; Müller-Ebhardt, H.; Munch, J.; Murray, P.; Myers, E.; Myers, J.; Nash, T.; Newton, G.; Nishizawa, A.; Nocera, F.; Numata, K.; O'Reilly, B.; O'Shaughnessy, R.; Ottaway, D. J.; Overmier, H.; Owen, B. J.; Pan, Y.; Papa, M. A.; Parameshwaraiah, V.; Parameswariah, C.; Patel, P.; Pedraza, M.; Penn, S.; Pierro, V.; Pinto, I. M.; Pitkin, M.; Pletsch, H.; Plissi, M. V.; Postiglione, F.; Prix, R.; Quetschke, V.; Raab, F.; Rabeling, D.; Radkins, H.; Rahkola, R.; Rainer, N.; Rakhmanov, M.; Rawlins, K.; Ray-Majumder, S.; Re, V.; Regimbau, T.; Rehbein, H.; Reid, S.; Reitze, D. H.; Ribichini, L.; Riesen, R.; Riles, K.; Rivera, B.; Robertson, N. A.; Robinson, C.; Robinson, E. L.; Roddy, S.; Rodriguez, A.; Rogan, A. M.; Rollins, J.; Romano, J. D.; Romie, J.; Route, R.; Rowan, S.; Rüdiger, A.; Ruet, L.; Russell, P.; Ryan, K.; Sakata, S.; Samidi, M.; de La Jordana, L. Sancho; Sandberg, V.; Sanders, G. H.; Sannibale, V.; Saraf, S.; Sarin, P.; Sathyaprakash, B. S.; Sato, S.; Saulson, P. R.; Savage, R.; Savov, P.; Sazonov, A.; Schediwy, S.; Schilling, R.; Schnabel, R.; Schofield, R.; Schutz, B. F.; Schwinberg, P.; Scott, S. M.; Searle, A. C.; Sears, B.; Seifert, F.; Sellers, D.; Sengupta, A. S.; Shawhan, P.; Shoemaker, D. H.; Sibley, A.; Sidles, J. A.; Siemens, X.; Sigg, D.; Sinha, S.; Sintes, A. M.; Slagmolen, B. J. J.; Slutsky, J.; Smith, J. R.; Smith, M. R.; Somiya, K.; Strain, K. A.; Strom, D. M.; Stuver, A.; Summerscales, T. Z.; Sun, K.-X.; Sung, M.; Sutton, P. J.; Takahashi, H.; Tanner, D. B.; Tarallo, M.; Taylor, R.; Taylor, R.; Thacker, J.; Thorne, K. A.; Thorne, K. S.; Thüring, A.; Tokmakov, K. V.; Torres, C.; Torrie, C.; Traylor, G.; Trias, M.; Tyler, W.; Ugolini, D.; Ungarelli, C.; Urbanek, K.; Vahlbruch, H.; Vallisneri, M.; van den Broeck, C.; van Putten, M.; Varvella, M.; Vass, S.; Vecchio, A.; Veitch, J.; Veitch, P.; Villar, A.; Vorvick, C.; Vyachanin, S. P.; Waldman, S. J.; Wallace, L.; Ward, H.; Ward, R.; Watts, K.; Webber, D.; Weidner, A.; Weinert, M.; Weinstein, A.; Weiss, R.; Wen, S.; Wette, K.; Whelan, J. T.; Whitbeck, D. M.; Whitcomb, S. E.; Whiting, B. F.; Wiley, S.; Wilkinson, C.; Willems, P. A.; Williams, L.; Willke, B.; Wilmut, I.; Winkler, W.; Wipf, C. C.; Wise, S.; Wiseman, A. G.; Woan, G.; Woods, D.; Wooley, R.; Worden, J.; Wu, W.; Yakushin, I.; Yamamoto, H.; Yan, Z.; Yoshida, S.; Yunes, N.; Zanolin, M.; Zhang, J.; Zhang, L.; Zhao, C.; Zotov, N.; Zucker, M.; Zur Mühlen, H.; Zweizig, J.; Kramer, M.; Lyne, A. G.

    2007-08-01

    We present upper limits on the gravitational wave emission from 78 radio pulsars based on data from the third and fourth science runs of the LIGO and GEO 600 gravitational wave detectors. The data from both runs have been combined coherently to maximize sensitivity. For the first time, pulsars within binary (or multiple) systems have been included in the search by taking into account the signal modulation due to their orbits. Our upper limits are therefore the first measured for 56 of these pulsars. For the remaining 22, our results improve on previous upper limits by up to a factor of 10. For example, our tightest upper limit on the gravitational strain is 2.6×10-25 for PSR J1603-7202, and the equatorial ellipticity of PSR J2124 3358 is less than 10-6. Furthermore, our strain upper limit for the Crab pulsar is only 2.2 times greater than the fiducial spin-down limit.

  20. VizieR Online Data Catalog: X-ray and radio sources in binaries (Malkov+, 2015)

    Science.gov (United States)

    Malkov, O. Y.; Tessema, S. B.; Kniazev, A. Y.

    2016-05-01

    We have also compiled a general list of 239 radio pulsars in binary systems. The list is supplied with indication of photometric, spectroscopic or X-ray binarity, and with cross-identification data. (4 data files).

  1. New algorithms for radio pulsar search

    CERN Document Server

    Smith, Kendrick M

    2016-01-01

    The computational cost of searching for new pulsars is a limiting factor for upcoming radio telescopes such as SKA. We introduce four new algorithms: an optimal constant-period search, a coherent tree search which permits optimal searching with O(1) cost per model, a semicoherent search which combines information from coherent subsearches while preserving as much phase information as possible, and a hierarchical search which interpolates between the coherent and semicoherent limits. Taken together, these algorithms improve the computational cost of pulsar search by several orders of magnitude. In this paper, we consider the simple case of a constant-acceleration phase model, but our methods should generalize to more complex search spaces.

  2. The nature of pulsar radio emission

    Science.gov (United States)

    Dyks, J.; Rudak, B.; Demorest, P.

    2010-01-01

    High-quality averaged radio profiles of some pulsars exhibit double, highly symmetric features both in emission and in absorption. It is shown that both types of feature are produced by a split fan beam of extraordinary-mode curvature radiation that is emitted/absorbed by radially extended streams of magnetospheric plasma. With no emissivity in the plane of the stream, such a beam produces bifurcated emission components (BFCs) when our line of sight passes through the plane. An example of a double component created in this way is present in the averaged profile of the 5-ms pulsar J1012+5307. We show that the component can indeed be very well fitted by the textbook formula for the non-coherent beam of curvature radiation in the polarization state that is orthogonal to the plane of electron trajectory. The observed width of the BFC decreases with increasing frequency at a rate that confirms the curvature origin. Likewise, the double absorption features (double notches) are produced by the same beam of the extraordinary-mode curvature radiation, when it is eclipsed by thin plasma streams. The intrinsic property of curvature radiation to create bifurcated fan beams explains the double features in terms of a very natural geometry and implies the curvature origin of pulsar radio emission. Similarly, the `double conal' profiles of class D result from a cut through a wider stream with finite extent in magnetic azimuth. Therefore, their width reacts very slowly to changes of viewing geometry resulting from geodetic precession. The stream-cut interpretation implies a highly non-orthodox origin of both the famous S-swing of polarization angle and the low-frequency pulse broadening in D profiles. The azimuthal structure of polarization modes in the curvature radiation beam provides an explanation for the polarized `multiple imaging' and the edge depolarization of pulsar profiles.

  3. THERMAL X-RAY EMISSION FROM THE SHOCKED STELLAR WIND OF PULSAR GAMMA-RAY BINARIES

    Energy Technology Data Exchange (ETDEWEB)

    Zabalza, V.; Paredes, J. M. [Departament d' Astronomia i Meteorologia, Institut de Ciencies del Cosmos (ICC), Universitat de Barcelona (IEEC-UB), Marti i Franques 1, E08028 Barcelona (Spain); Bosch-Ramon, V., E-mail: vzabalza@am.ub.es [Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2 (Ireland)

    2011-12-10

    Gamma-ray-loud X-ray binaries are binary systems that show non-thermal broadband emission from radio to gamma rays. If the system comprises a massive star and a young non-accreting pulsar, their winds will collide producing broadband non-thermal emission, most likely originated in the shocked pulsar wind. Thermal X-ray emission is expected from the shocked stellar wind, but until now it has neither been detected nor studied in the context of gamma-ray binaries. We present a semi-analytic model of the thermal X-ray emission from the shocked stellar wind in pulsar gamma-ray binaries, and find that the thermal X-ray emission increases monotonically with the pulsar spin-down luminosity, reaching luminosities of the order of 10{sup 33} erg s{sup -1}. The lack of thermal features in the X-ray spectrum of gamma-ray binaries can then be used to constrain the properties of the pulsar and stellar winds. By fitting the observed X-ray spectra of gamma-ray binaries with a source model composed of an absorbed non-thermal power law and the computed thermal X-ray emission, we are able to derive upper limits on the spin-down luminosity of the putative pulsar. We applied this method to LS 5039, the only gamma-ray binary with a radial, powerful wind, and obtain an upper limit on the pulsar spin-down luminosity of {approx}6 Multiplication-Sign 10{sup 36} erg s{sup -1}. Given the energetic constraints from its high-energy gamma-ray emission, a non-thermal to spin-down luminosity ratio very close to unity may be required.

  4. The nature of pulsar radio emission

    CERN Document Server

    Dyks, J; Demorest, P

    2009-01-01

    High-quality averaged radio profiles of some pulsars exhibit double, highly symmetric features both in `absorption' and emission. Averaged profile of a 5-ms pulsar J1012+5307 hosts a distinct, extremely symmetric, and bifurcated emission component (BFC) with deep central minimum. We show that the component can be very well fitted by the textbook formula for the non-coherent beam of curvature radiation (CR) in the polarisation state that is orthogonal to the plane of electron trajectory. The separation Delta_bfc of maxima in the BFC is observed to decrease with increasing frequency nu_obs at the rate that is consistent with the curvature origin (Delta_bfc proportional to nu_obs^(-1/3)). With zero emissivity in the plane of electron trajectory, the extraordinary-mode beam can naturally produce deep double absorption features (double notches) observed in other pulsars. The bifurcated emission components are observed when the line of sight passes through splitted fan beams produced by radially-extended streams of...

  5. Accretion, Ablation and Propeller Evolution in Close Millisecond Pulsar Binary Systems

    CERN Document Server

    Kiel, P D

    2013-01-01

    A model for the formation and evolution of binary millisecond radio pulsars in systems with low mass companions (< 0.1 Msun) is investigated using a binary population synthesis technique. Taking into account the non conservative evolution of the system due to mass loss from an accretion disk as a result of propeller action and from the companion via ablation by the pulsar, the transition from the accretion powered to rotation powered phase is investigated. It is shown that the operation of the propeller and ablation mechanisms can be responsible for the formation and evolution of black widow millisecond pulsar systems from the low mass X-ray binary phase at an orbital period of ~0.1 day. For a range of population synthesis input parameters, the results reveal that a population of black widow millisecond pulsars characterized by orbital periods as long as ~0.4 days and companion masses as low as ~0.005 Msun can be produced. The orbital periods and minimum companion mass of this radio millisecond pulsar popu...

  6. Gravitational waves from binary supermassive black holes missing in pulsar observations.

    Science.gov (United States)

    Shannon, R M; Ravi, V; Lentati, L T; Lasky, P D; Hobbs, G; Kerr, M; Manchester, R N; Coles, W A; Levin, Y; Bailes, M; Bhat, N D R; Burke-Spolaor, S; Dai, S; Keith, M J; Osłowski, S; Reardon, D J; van Straten, W; Toomey, L; Wang, J-B; Wen, L; Wyithe, J S B; Zhu, X-J

    2015-09-25

    Gravitational waves are expected to be radiated by supermassive black hole binaries formed during galaxy mergers. A stochastic superposition of gravitational waves from all such binary systems would modulate the arrival times of pulses from radio pulsars. Using observations of millisecond pulsars obtained with the Parkes radio telescope, we constrained the characteristic amplitude of this background, A(c,yr), to be <1.0 × 10(-15) with 95% confidence. This limit excludes predicted ranges for A(c,yr) from current models with 91 to 99.7% probability. We conclude that binary evolution is either stalled or dramatically accelerated by galactic-center environments and that higher-cadence and shorter-wavelength observations would be more sensitive to gravitational waves.

  7. Gravitational waves from binary supermassive black holes missing in pulsar observations

    CERN Document Server

    Shannon, R M; Lentati, L T; Lasky, P D; Hobbs, G; Kerr, M; Manchester, R N; Coles, W A; Levin, Y; Bailes, M; Bhat, N D R; Burke-Spolaor, S; Dai, S; Keith, M J; Osłowski, S; Reardon, D J; van Straten, W; Toomey, L; Wang, J -B; Wen, L; Wyithe, J S B; Zhu, X -J

    2015-01-01

    Gravitational waves are expected to be radiated by supermassive black hole binaries formed during galaxy mergers. A stochastic superposition of gravitational waves from all such binary systems will modulate the arrival times of pulses from radio pulsars. Using observations of millisecond pulsars obtained with the Parkes radio telescope, we constrain the characteristic amplitude of this background, $A_{\\rm c,yr}$, to be < $1.0\\times10^{-15}$ with 95% confidence. This limit excludes predicted ranges for $A_{\\rm c,yr}$ from current models with 91-99.7% probability. We conclude that binary evolution is either stalled or dramatically accelerated by galactic-center environments, and that higher-cadence and shorter-wavelength observations would result in an increased sensitivity to gravitational waves.

  8. On binary pulsars and the force of gravity

    CERN Document Server

    Palle, D

    2002-01-01

    We reanalyze a binary pulsar system and show that the orbital period change rate can be completely understood as a curvature backreaction process. Appreciating a detailed theoretical and observational study of relativistic binary pulsar systems, especially the system of Hulse and Taylor, we conclude that general relativity and astrophysical observations rule out the existence of gravitational radiation. Thus, the force of gravity is not a local gauge force.

  9. Radio Searches for Pulsars and Short-Duration Transients

    CERN Document Server

    McLaughlin, Maura

    2011-01-01

    I discuss methods and current software packages for radio searches for pulsars and short-duration transients. I then describe the properties of the current pulsar population and the status of and predictions for ongoing and future surveys. The presently observed pulsar population numbers around 2000 and is expected to roughly double over the next five years, with the number of millisecond pulsars expected to more than triple. Finally, I discuss individual objects discovered in the Green Bank Telescope 350-MHz Drift-Scan Survey and the Arecibo Pulsar ALFA Survey.

  10. Are the infrared-faint radio sources pulsars?

    Science.gov (United States)

    Cameron, A. D.; Keith, M.; Hobbs, G.; Norris, R. P.; Mao, M. Y.; Middelberg, E.

    2011-07-01

    Infrared-faint radio sources (IFRS) are objects which are strong at radio wavelengths but undetected in sensitive Spitzer observations at infrared wavelengths. Their nature is uncertain and most have not yet been associated with any known astrophysical object. One possibility is that they are radio pulsars. To test this hypothesis we undertook observations of 16 of these sources with the Parkes Radio Telescope. Our results limit the radio emission to a pulsed flux density of less than 0.21 mJy (assuming a 50 per cent duty cycle). This is well below the flux density of the IFRS. We therefore conclude that these IFRS are not radio pulsars.

  11. Are the infrared-faint radio sources pulsars?

    CERN Document Server

    Keith, A D Cameron M J; Norris, R P; Mao, M Y; Middelberg, E

    2011-01-01

    Infrared-Faint Radio Sources (IFRS) are objects which are strong at radio wavelengths but undetected in sensitive Spitzer observations at infrared wavelengths. Their nature is uncertain and most have not yet been associated with any known astrophysical object. One possibility is that they are radio pulsars. To test this hypothesis we undertook observations of 16 of these sources with the Parkes Radio Telescope. Our results limit the radio emission to a pulsed flux density of less than 0.21 mJy (assuming a 50% duty cycle). This is well below the flux density of the IFRS. We therefore conclude that these IFRS are not radio pulsars.

  12. Transformation of a Star into a Planet in a Millisecond Pulsar Binary

    CERN Document Server

    Bailes, M; Bhalerao, V; Bhat, N D R; Burgay, M; Burke-Spolaor, S; D'Amico, N; Johnsto, S; Keith, M J; Kramer, M; Kulkarni, S R; Levin, L; Lyne, A G; Milia, S; Possenti, A; Spitler, L; Stappers, B; van Straten, W

    2011-01-01

    Millisecond pulsars are thought to be neutron stars that have been spun-up by accretion of matter from a binary companion. Although most are in binary systems, some 30% are solitary, and their origin is therefore mysterious. PSR J1719-1438, a 5.7 ms pulsar, was detected in a recent survey with the Parkes 64m radio telescope. We show that it is in a binary system with an orbital period of 2.2 h. Its companion's mass is near that of Jupiter, but its minimum density of 23 g cm$^{-3}$ suggests that it may be an ultra-low mass carbon white dwarf. This system may thus have once been an Ultra Compact Low-Mass X-ray Binary, where the companion narrowly avoided complete destruction.

  13. 1FGL J0523.5-2529: A New Probable Gamma-ray Pulsar Binary

    CERN Document Server

    Strader, Jay; Sonbas, Eda; Sokolovsky, Kirill; Sand, David J; Moskvitin, Alexander S; Cheung, C C

    2014-01-01

    We report optical photometric and SOAR spectroscopic observations of an X-ray source found within the localization error of the Fermi-LAT unidentified gamma-ray source J0523.5-2529. The optical data show periodic flux modulation and radial velocity variations indicative of a binary with a 16.5-hr period. The data suggest a massive non-degenerate secondary (~> 0.8 M_sun), and we argue the source is likely a pulsar binary. The radial velocities have good phase coverage and show evidence for a measurable eccentricity (e=0.04). There is no clear sign of irradiation of the secondary in either photometry or spectroscopy. The spatial location out of the Galactic plane and gamma-ray luminosity of the source are more consistent with classification as a recycled millisecond pulsar than as a young pulsar. Future radio timing observations can confirm the identity of the primary and further characterize this interesting system.

  14. Radio Searches of Fermi LAT Sources and Blind Search Pulsars: The Fermi Pulsar Search Consortium

    CERN Document Server

    Ray, P S; Parent, D; Bhattacharya, D; Bhattacharyya, B; Camilo, F; Cognard, I; Theureau, G; Ferrara, E C; Harding, A K; Thompson, D J; Freire, P C C; Guillemot, L; Gupta, Y; Roy, J; Hessels, J W T; Johnston, S; Keith, M; Shannon, R; Kerr, M; Michelson, P F; Romani, R W; Kramer, M; McLaughlin, M A; Ransom, S M; Roberts, M S E; Parkinson, P M Saz; Ziegler, M; Smith, D A; Stappers, B W; Weltevrede, P; Wood, K S

    2012-01-01

    We present a summary of the Fermi Pulsar Search Consortium (PSC), an international collaboration of radio astronomers and members of the Large Area Telescope (LAT) collaboration, whose goal is to organize radio follow-up observations of Fermi pulsars and pulsar candidates among the LAT gamma-ray source population. The PSC includes pulsar observers with expertise using the world's largest radio telescopes that together cover the full sky. We have performed very deep observations of all 35 pulsars discovered in blind frequency searches of the LAT data, resulting in the discovery of radio pulsations from four of them. We have also searched over 300 LAT gamma-ray sources that do not have strong associations with known gamma-ray emitting source classes and have pulsar-like spectra and variability characteristics. These searches have led to the discovery of a total of 43 new radio millisecond pulsars (MSPs) and four normal pulsars. These discoveries greatly increase the known population of MSPs in the Galactic disk...

  15. The NANOGrav Nine-year Data Set: Mass and Geometric Measurements of Binary Millisecond Pulsars

    CERN Document Server

    Fonseca, Emmanuel; Ellis, Justin A; Stairs, Ingrid H; Nice, David J; Ransom, Scott M; Demorest, Paul B; Arzoumanian, Zaven; Crowter, Kathryn; Dolch, Timothy; Ferdman, Robert D; Gonzalez, Marjorie E; Jones, Glenn; Jones, Megan L; Lam, Michael T; Levin, Lina; McLaughlin, Maura A; Stovall, Kevin; Swiggum, Joseph K; Zhu, Weiwei

    2016-01-01

    We analyse 24 binary radio pulsars in the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) nine-year data set. We made fourteen significant measurements of Shapiro delay, including new detections in four pulsar-binary systems (PSRs J0613$-$0200, J2017+0603, J2302+4442, and J2317+1439), and derive estimates of the binary-component masses and orbital inclination for these MSP-binary systems. We find a wide range of binary pulsar masses, with values as low as $m_{\\rm p} = 1.18^{+0.10}_{-0.09}\\text{ M}_{\\odot}$ for PSR J1918$-$0642 and as high as $m_{\\rm p} = 1.928^{+0.017}_{-0.017}\\text{ M}_{\\odot}$ for PSR J1614$-$2230 (both 68.3\\% confidence). We make an improved measurement of the Shapiro timing delay in the PSR J1918$-$0642 and J2043+1711 systems, measuring the pulsar mass in the latter system to be $m_{\\rm p} = 1.41^{+0.21}_{-0.18}\\text{ M}_{\\odot}$ (68.3\\% confidence) for the first time. We measure secular variations of one or more orbital elements in many systems, and use these meas...

  16. Magnetic field decay in normal radio pulsars

    CERN Document Server

    Igoshev, A P

    2015-01-01

    We analyse the origin of the magnetic field decay in normal radio pulsars found by us in a recent study. This decay has a typical time scale $\\sim 4 \\times 10^5$~yrs, and operates in the range $\\sim 10^5$~--~few$\\times 10^5$~yrs. We demonstrate that this field evolution may be either due to the Ohmic decay related to the scattering from phonons, or due to the Hall cascade which reaches the Hall attractor. According to our analysis the first possibility seems to be more reliable. So, we attribute the discovered field decay mainly to the Ohmic decay on phonons which is saturated at the age few$\\times 10^5$~yrs, when a NS cools down to the critical temperature below which the phonon scattering does not contribute much to the resistivity of the crust. Some role of the Hall effect and attractor is not excluded, and will be analysed in our further studies.

  17. Compactified pulsar wind nebula model of gamma-ray loud binary LSI +61 303

    CERN Document Server

    Neronov, A

    2007-01-01

    We show that radio-to-TeV properties of the binary system LSI +61 303 can be explained by interaction of the compact object (a young pulsar) with the inhomogeneities of the wind from companion Be star. We develop a model scenario of "compactified" pulsar wind nebula formed in result of such interaction. To test the model assumptions about geometry of the system we re-analyze the available X-ray observations to study in more details the variations of the hydrogen column density on long (orbital) and short (several kilosecond) time scales.

  18. On the nature and evolution of the unique binary pulsar J1903+0327

    CERN Document Server

    Freire, P C C; Wex, N; Stairs, I H; Champion, D J; Ransom, S M; Lazarus, P; Kaspi, V M; Hessels, J W T; Kramer, M; Cordes, J M; Verbiest, J P W; Podsiadlowski, P; Nice, D ~J; Deneva, J S; Lorimer, D R; Stappers, B W; McLaughlin, M A; Camilo, F

    2010-01-01

    (abridged) PSR J1903+0327, a millisecond pulsar in an eccentric (e = 0.44) 95-day orbit with a (~ 1Msun) companion poses a challenge to our understanding of stellar evolution in binary and multiple-star systems. Here we describe optical and radio observations which rule out most of the scenarios proposed to explain formation of this system. Radio timing measurements of three post-Keplerian effects yield the most precise measurement of the mass of a millisecond pulsar to date: 1.667 +/- 0.021 solar masses (99.7% confidence limit) (...). Optical spectroscopy of a proposed main sequence counterpart show that its orbital motion mirrors the pulsar's 95-day orbit; being therefore its binary companion (...) The optical detection also provides a measurement of the systemic radial velocity of the binary; this and the proper motion measured from pulsar timing allow the determination of the systemic 3-D velocity in the Galaxy. We find that the system is always within 270 pc of the plane of the Galaxy, but always more th...

  19. GMRT Discovery of A Millisecond Pulsar in a Very Eccentric Binary System

    CERN Document Server

    Freire, P C; Ransom, S M; Ishwara-Chandra, C H; Freire, Paulo C.; Gupta, Yashwant; Ransom, Scott M.

    2004-01-01

    We report the discovery of the binary millisecond pulsar J0514-4002A, which is the first known pulsar in the globular cluster NGC 1851 and the first pulsar discovered using the Giant Metrewave Radio Telescope (GMRT). The pulsar has a rotational period of 4.99 ms, an orbital period of 18.8 days, and the most eccentric pulsar orbit yet measured (e = 0.89). The companion has a minimum mass of 0.9 M_sun and its nature is presently unclear. After accreting matter from a low-mass companion star which spun it up to a (few) millisecond spin period, the pulsar eventually exchanged the low-mass star for its more massive present companion. This is exactly the same process that could form a system containing a millisecond pulsar and a black hole; the discovery of NGC 1851A demonstrates that such systems might exist in the Universe, provided that stellar mass black holes exist in globular clusters.

  20. Discovery of Two High-Magnetic-Field Radio Pulsars

    CERN Document Server

    Camilo, F M; Lyne, A G; Manchester, R N; Bell, J F; D'Amico, N; McKay, N P F; Crawford, F

    2000-01-01

    We report the discovery of two young isolated radio pulsars with very high inferred magnetic fields. PSR J1119-6127 has period P = 0.407 s, and the largest period derivative known among radio pulsars, Pdot = 4.0e-12. Under standard assumptions these parameters imply a characteristic spin-down age of only tau = 1.6 kyr and a surface dipole magnetic field strength of B = 4.1e13 G. We have measured a stationary period-second-derivative for this pulsar, resulting in a braking index of n = 2.91+-0.05. We have also observed a glitch in the rotation of the pulsar, with fractional period change Delta_P/P = -4.4e-9. Archival radio imaging data suggest the presence of a previously uncataloged supernova remnant centered on the pulsar. The second pulsar, PSR J1814-1744, has P = 3.975 s and Pdot = 7.4e-13. These parameters imply tau = 85 kyr, and B = 5.5e13 G, the largest of any known radio pulsar. Both PSR J1119-6127 and PSR J1814-1744 show apparently normal radio emission in a regime of magnetic field strength where som...

  1. A Search for X-ray Counterparts of Radio Pulsars

    CERN Document Server

    Prinz, Tobias

    2015-01-01

    We describe a systematic search for X-ray counterparts of radio pulsars. The search was accomplished by cross-correlating the radio timing positions of all radio pulsars from the ATNF pulsar database (version 1.54) with archival XMM-Newton and Chandra observations publicly released by August 1st 2015. In total, 171 of the archival XMM-Newton observations and 215 of the archival Chandra datasets where found to have a radio pulsar serendipitously in the field of view. From the 283 radio pulsars covered by these datasets we identified 19 previously undetected X-ray counterparts. For 6 of them the statistics was sufficient to model the energy spectrum with one- or two-component models. For the remaining new detections and for those pulsars for which we determined an upper limit to their counting rate we computed the energy flux by assuming a Crab-like spectrum. Additionally, we derived upper limits on the neutron stars' surface temperature and on the non-thermal X-ray efficiency for those pulsars for which the sp...

  2. The NANOGrav Nine-year Data Set: Mass and Geometric Measurements of Binary Millisecond Pulsars

    Science.gov (United States)

    Fonseca, Emmanuel; Pennucci, Timothy T.; Ellis, Justin A.; Stairs, Ingrid H.; Nice, David J.; Ransom, Scott M.; Demorest, Paul B.; Arzoumanian, Zaven; Crowter, Kathryn; Dolch, Timothy; Ferdman, Robert D.; Gonzalez, Marjorie E.; Jones, Glenn; Jones, Megan L.; Lam, Michael T.; Levin, Lina; McLaughlin, Maura A.; Stovall, Kevin; Swiggum, Joseph K.; Zhu, Weiwei

    2016-12-01

    We analyze 24 binary radio pulsars in the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) nine-year data set. We make 14 significant measurements of the Shapiro delay, including new detections in four pulsar-binary systems (PSRs J0613-0200, J2017+0603, J2302+4442, and J2317+1439), and derive estimates of the binary-component masses and orbital inclination for these MSP-binary systems. We find a wide range of binary pulsar masses, with values as low as {m}{{p}}={1.18}-0.09+0.10 {M}⊙ for PSR J1918-0642 and as high as {m}{{p}}={1.928}-0.017+0.017 {M}⊙ for PSR J1614-2230 (both 68.3% credibility). We make an improved measurement of the Shapiro timing delay in the PSR J1918-0642 and J2043+1711 systems, measuring the pulsar mass in the latter system to be {m}{{p}}={1.41}-0.18+0.21 {M}⊙ (68.3% credibility) for the first time. We measure secular variations of one or more orbital elements in many systems, and use these measurements to further constrain our estimates of the pulsar and companion masses whenever possible. In particular, we used the observed Shapiro delay and periastron advance due to relativistic gravity in the PSR J1903+0327 system to derive a pulsar mass of {m}{{p}}={1.65}-0.02+0.02 {M}⊙ (68.3% credibility). We discuss the implications that our mass measurements have on the overall neutron-star mass distribution, and on the “mass/orbital-period” correlation due to extended mass transfer.

  3. Radio Emission Physics in the Crab Pulsar

    CERN Document Server

    Eilek, J A

    2016-01-01

    We review our high-time-resolution radio observations of the Crab pulsar and compare our data to a variety of models for the emission physics. The Main Pulse and the Low-Frequency Interpulse come from regions somewhere in the high-altitude emission zones (caustics) that also produce pulsed X-ray and gamma-ray emission. Although no emission model can fully explain these two components, the most likely models suggest they arise from a combination of beam-driven instabilities, coherent charge bunching and strong electromagnetic turbulence. Because the radio power fluctuates on a wide range of timescales, we know the emission zones are patchy and dynamic. It is tempting to invoke unsteady pair creation in high-altitude gaps as source of the variability, but current pair cascade models cannot explain the densities required by any of the likely models. It is harder to account for the mysterious High-Frequency Interpulse. We understand neither its origin within the magnetosphere nor the striking emission bands in it...

  4. The timing behaviour of radio pulsars

    CERN Document Server

    Hobbs, G

    2009-01-01

    The purpose of this review paper is to summarise the pulsar timing method, to provide an overview of recent research into the spin-down of pulsars over decadal timescales and to highlight the science that can be achieved using high-precision timing of millisecond pulsars.

  5. The Einstein@Home Search for Radio Pulsars and PSR J2007+2722 Discovery

    Science.gov (United States)

    Allen, B.; Knispel, B.; Cordes, J. M.; Deneva, J. S.; Hessels, J. W. T.; Anderson, D.; Aulbert, C.; Bock, O.; Brazier, A.; Chatterjee, S.; Demorest, P. B.; Eggenstein, H. B.; Fehrmann, H.; Gotthelf, E. V.; Hammer, D.; Kaspi, V. M.; Kramer, M.; Lyne, A. G.; Machenschalk, B.; McLaughlin, M. A.; Messenger, C.; Pletsch, H. J.; Ransom, S. M.; Stairs, I. H.; Stappers, B. W.; Bhat, N. D. R.; Bogdanov, S.; Camilo, F.; Champion, D. J.; Crawford, F.; Desvignes, G.; Freire, P. C. C.; Heald, G.; Jenet, F. A.; Lazarus, P.; Lee, K. J.; van Leeuwen, J.; Lynch, R.; Papa, M. A.; Prix, R.; Rosen, R.; Scholz, P.; Siemens, X.; Stovall, K.; Venkataraman, A.; Zhu, W.

    2013-08-01

    Einstein@Home aggregates the computer power of hundreds of thousands of volunteers from 193 countries, to search for new neutron stars using data from electromagnetic and gravitational-wave detectors. This paper presents a detailed description of the search for new radio pulsars using Pulsar ALFA survey data from the Arecibo Observatory. The enormous computing power allows this search to cover a new region of parameter space; it can detect pulsars in binary systems with orbital periods as short as 11 minutes. We also describe the first Einstein@Home discovery, the 40.8 Hz isolated pulsar PSR J2007+2722, and provide a full timing model. PSR J2007+2722's pulse profile is remarkably wide with emission over almost the entire spin period. This neutron star is most likely a disrupted recycled pulsar, about as old as its characteristic spin-down age of 404 Myr. However, there is a small chance that it was born recently, with a low magnetic field. If so, upper limits on the X-ray flux suggest but cannot prove that PSR J2007+2722 is at least ~100 kyr old. In the future, we expect that the massive computing power provided by volunteers should enable many additional radio pulsar discoveries.

  6. THE EINSTEIN-HOME SEARCH FOR RADIO PULSARS AND PSR J2007+2722 DISCOVERY

    Energy Technology Data Exchange (ETDEWEB)

    Allen, B.; Knispel, B.; Aulbert, C.; Bock, O.; Eggenstein, H. B.; Fehrmann, H.; Machenschalk, B. [Max-Planck-Institut fuer Gravitationsphysik, D-30167 Hannover (Germany); Cordes, J. M.; Brazier, A.; Chatterjee, S. [Department of Astronomy, Cornell University, Ithaca, NY 14853 (United States); Deneva, J. S. [Arecibo Observatory, HC3 Box 53995, Arecibo, PR 00612 (United States); Hessels, J. W. T. [ASTRON, the Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA, Dwingeloo (Netherlands); Anderson, D. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Demorest, P. B. [NRAO (National Radio Astronomy Observatory), Charlottesville, VA 22903 (United States); Gotthelf, E. V. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Hammer, D. [Department of Physics, University of Wisconsin-Milwaukee, Milwaukee, WI 53211 (United States); Kaspi, V. M. [Department of Physics, McGill University, Montreal, QC H3A2T8 (Canada); Kramer, M. [Max-Planck-Institut fuer Radioastronomie, D-53121 Bonn (Germany); Lyne, A. G. [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL (United Kingdom); McLaughlin, M. A., E-mail: bruce.allen@aei.mpg.de [Department of Physics, West Virginia University, Morgantown, WV 26506 (United States); and others

    2013-08-20

    Einstein-Home aggregates the computer power of hundreds of thousands of volunteers from 193 countries, to search for new neutron stars using data from electromagnetic and gravitational-wave detectors. This paper presents a detailed description of the search for new radio pulsars using Pulsar ALFA survey data from the Arecibo Observatory. The enormous computing power allows this search to cover a new region of parameter space; it can detect pulsars in binary systems with orbital periods as short as 11 minutes. We also describe the first Einstein-Home discovery, the 40.8 Hz isolated pulsar PSR J2007+2722, and provide a full timing model. PSR J2007+2722's pulse profile is remarkably wide with emission over almost the entire spin period. This neutron star is most likely a disrupted recycled pulsar, about as old as its characteristic spin-down age of 404 Myr. However, there is a small chance that it was born recently, with a low magnetic field. If so, upper limits on the X-ray flux suggest but cannot prove that PSR J2007+2722 is at least {approx}100 kyr old. In the future, we expect that the massive computing power provided by volunteers should enable many additional radio pulsar discoveries.

  7. Spectroscopic Studies of X-Ray Binary Pulsars

    Indian Academy of Sciences (India)

    F. Nagase

    2002-03-01

    Several new features of X-ray binary pulsars are revealed from recent observations with ASCA, RXTE, BeppoSAX and other X-ray observatories. Among these, I will review in this paper some recent progress in spectroscopic studies of accreting X-ray pulsars in binary systems (XBPs). First, I will discuss soft excess features observed in the energy spectra of XBPs and propose that it is a common feature for various subclasses of XBPs. Next I will present some recent results of high resolution spectroscopy with ASCA and Chandra.

  8. A SEARCH FOR RAPIDLY SPINNING PULSARS AND FAST TRANSIENTS IN UNIDENTIFIED RADIO SOURCES WITH THE NRAO 43 METER TELESCOPE

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Deborah; Crawford, Fronefield; Gilpin, Claire [Department of Physics and Astronomy, Franklin and Marshall College, P.O. Box 3003, Lancaster, PA 17604 (United States); Langston, Glen [National Radio Astronomy Observatory, P.O. Box 2, Green Bank, WV 24944 (United States)

    2013-04-15

    We have searched 75 unidentified radio sources selected from the NRAO VLA Sky Survey catalog for the presence of rapidly spinning pulsars and short, dispersed radio bursts. The sources are radio bright, have no identifications or optical source coincidences, are more than 5% linearly polarized, and are spatially unresolved in the catalog. If these sources are fast-spinning pulsars (e.g., sub-millisecond pulsars), previous large-scale pulsar surveys may have missed detection due to instrumental and computational limitations, eclipsing effects, or diffractive scintillation. The discovery of a sub-millisecond pulsar would significantly constrain the neutron star equation of state and would have implications for models predicting a rapid slowdown of highly recycled X-ray pulsars to millisecond periods from, e.g., accretion disk decoupling. These same sources were previously searched unsuccessfully for pulsations at 610 MHz with the Lovell Telescope at Jodrell Bank. This new search was conducted at a different epoch with a new 800 MHz backend on the NRAO 43 m Telescope at a center frequency of 1200 MHz. Our search was sensitive to sub-millisecond pulsars in highly accelerated binary systems and to short transient pulses. No periodic or transient signals were detected from any of the target sources. We conclude that diffractive scintillation, dispersive smearing, and binary acceleration are unlikely to have prevented detection of the large majority of the sources if they are pulsars, though we cannot rule out eclipsing, nulling or intermittent emission, or radio interference as possible factors for some non-detections. Other (speculative) possibilities for what these sources might include radio-emitting magnetic cataclysmic variables or older pulsars with aligned magnetic and spin axes.

  9. The Binary Companion of Young, Relativistic Pulsar J1906+0746

    CERN Document Server

    van Leeuwen, Joeri; Stairs, Ingrid H; Lorimer, D R; Camilo, F; Chatterjee, S; Cognard, I; Desvignes, G; Freire, P C C; Janssen, G H; Kramer, M; Lyne, A G; Nice, D J; Ransom, S M; Stappers, B W; Weisberg, J M

    2014-01-01

    PSR J1906+0746 is a young pulsar in the relativistic binary with the second-shortest known orbital period, of 3.98 hours. We here present a timing study based on five years of observations, conducted with the 5 largest radio telescopes in the world, aimed at determining the companion nature. Through the measurement of three post-Keplerian orbital parameters we find the pulsar mass to be 1.291(11) M_sol, and the companion mass 1.322(11) M_sol respectively. These masses fit well in the observed collection of double neutron stars, but are also compatible with other white dwarfs around young pulsars such as J1906+0746. Neither radio pulsations nor dispersion-inducing outflows that could have further established the companion nature were detected. We derive an HI-absorption distance, which indicates that an optical confirmation of a white dwarf companion is very challenging. The pulsar is fading fast due to geodetic precession, limiting future timing improvements. We conclude that young pulsar J1906+0746 is likely...

  10. THE BINARY COMPANION OF YOUNG, RELATIVISTIC PULSAR J1906+0746

    Energy Technology Data Exchange (ETDEWEB)

    Van Leeuwen, J.; Janssen, G. H. [ASTRON, The Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA Dwingeloo (Netherlands); Kasian, L.; Stairs, I. H. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1 (Canada); Lorimer, D. R. [Department of Physics, West Virginia University, Morgantown, WV 26506 (United States); Camilo, F. [Arecibo Observatory, HC3 Box 53995, Arecibo, PR 00612 (United States); Chatterjee, S. [Center for Radiophysics and Space Research, Cornell University, Ithaca, NY 14853 (United States); Cognard, I. [Laboratoire de Physique et Chimie de l' Environnement et de l' Espace LPC2E CNRS-Université d' Orléans, F-45071 Orléans (France); Desvignes, G.; Freire, P. C. C.; Kramer, M. [Max-Planck-Institut für Radioastronomie, D-53121 Bonn (Germany); Lyne, A. G.; Stappers, B. W. [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Nice, D. J. [Department of Physics, Lafayette College, Easton, PA 18042 (United States); Ransom, S. M. [NRAO (National Radio Astronomy Observatory), Charlottesville, VA 22903 (United States); Weisberg, J. M., E-mail: leeuwen@astron.nl [Department of Physics and Astronomy, Carleton College, Northfield, MN 55057 (United States)

    2015-01-10

    PSR J1906+0746 is a young pulsar in the relativistic binary with the second-shortest known orbital period, of 3.98 hr. We here present a timing study based on five years of observations, conducted with the five largest radio telescopes in the world, aimed at determining the companion nature. Through the measurement of three post-Keplerian orbital parameters, we find the pulsar mass to be 1.291(11) M {sub ☉}, and the companion mass 1.322(11) M {sub ☉}, respectively. These masses fit well in the observed collection of double neutron stars (DNSs), but are also compatible with other systems where a young pulsar such as J1906+0746 is orbited by a white dwarf (WD). Neither radio pulsations nor dispersion-inducing outflows that could have further established the companion nature were detected. We derive an H I-absorption distance, which indicates that an optical confirmation of a WD companion is very challenging. The pulsar is fading fast due to geodetic precession, limiting future timing improvements. We conclude that the young pulsar J1906+0746 is likely part of a DNS, or is otherwise orbited by an older WD, in an exotic system formed through two stages of mass transfer.

  11. Pulsar-Black Hole Binaries in the Galactic Center

    CERN Document Server

    Faucher-Giguere, C -A

    2010-01-01

    Binaries consisting of a pulsar and a black hole (BH) are a holy grail of astrophysics, both for their significance for stellar evolution and for their potential application as probes of strong gravity. In spite of extensive surveys of our Galaxy and its system of globular clusters, no pulsar-black hole (PSR-BH) binary has been found to date. Clues as to where such systems might exist are therefore highly desirable. We show that if the central parsec around Sgr A* harbors a cluster of ~25,000 stellar BHs (as predicted by mass segregation arguments) and if it is also rich in recycled pulsar binaries (by analogy with globular clusters), then 3-body exchange interactions should produce PSR-BHs in the Galactic center. Simple estimates of the formation rate and survival time of these binaries suggest that a few PSR-BHs should be present in the central parsec today. The proposed formation mechanism makes unique predictions for the PSR-BH properties: 1) the binary would reside within ~1 pc of Sgr A*; 2) the pulsar w...

  12. On pulsar-driven mass ejection in low-mass X-ray binaries

    Institute of Scientific and Technical Information of China (English)

    Lei Fu; Xiang-Dong Li

    2011-01-01

    There is accumulating evidence for mass ejection in low-mass X-ray binaries (LMXBs) driven by radio pulsar activity during X-ray quiescence.We consider the condition for mass ejection by comparing the radiation pressure from a millisecond pulsar,and the gas pressure at the inner Lagrange point or at the surrounding accretion disk.We calculate the critical spin period of the pulsar below which mass ejection is allowed.Combining with the evolution of the mass transfer rate,we present constraints on the orbital periods of the systems.We show that mass ejection could happen in both wide and compact LMXBs.It may be caused by transient accretion due to thermal instability in the accretion disks in the former,and irradiation-driven mass-transfer cycles in the latter.

  13. Radio Quiet Pulsars with Ultra-Strong Magnetic Fields

    CERN Document Server

    Baring, M G; Baring, Matthew G.; Harding, Alice K.

    1998-01-01

    The notable absence of radio pulsars having measured magnetic dipole surface field strengths above $B_0\\sim 3\\times 10^{13}$ Gauss naturally raises the question of whether this forms an upper limit to pulsar magnetization. Recently there has been increasing evidence that neutron stars possessing higher dipole spin-down fields do in fact exist, including a growing list of anomalous X-ray pulsars (AXPs) with long periods and spinning down with high period derivatives, implying surface fields of $10^{14}$--$10^{15}$ Gauss. Furthermore, the recently reported X-ray period and period derivative for the Soft Gamma-ray Repeater (SGR) source SGR1806-20 suggest a surface field around $10^{15}$ Gauss. None of these high-field pulsars have yet been detected as radio pulsars. We propose that high-field pulsars should be radio-quiet because electron-positron pair production in their magnetospheres, thought to be essential for radio emission, is efficiently suppressed in ultra-strong fields ($B_0\\gtrsim 4\\times 10^{13}$ Gau...

  14. Radio pulsars and transients in the Galactic center

    Energy Technology Data Exchange (ETDEWEB)

    Lazio, Joseph [Naval Research Laboratory, 4555 Overlook Ave. SW, Washington, DC 20375-5351 (United States); Deneva, J S [Astronomy Department and NAIC, Cornell University, Ithaca, NY 14853 (United States); Bower, Geoffrey C [Astronomy Department and Radio Astronomy Laboratory, University of California, Berkeley, CA 94720 (United States); Cordes, J M [Astronomy Department and NAIC, Cornell University, Ithaca, NY 14853 (United States); Hyman, Scott D [Department of Physics and Engineering, Sweet Briar College, Sweet Briar, VA 24595 (United States); Backer, D C [Astronomy Department and Radio Astronomy Laboratory, University of California, Berkeley, CA 94720 (United States); Bhat, R [Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, Victoria 3122 (Australia); Chatterjee, S [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Demorest, P [Astronomy Department and Radio Astronomy Laboratory, University of California, Berkeley, CA 94720 (United States); Ransom, S M [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Vlemmings, W [Jodrell Bank Observatory, University of Manchester, Macclesfleld, Cheshire, SK11 9DL, UK (United Kingdom)

    2006-12-15

    Radio pulsars and transients provide powerful probes of the star formation history, interstellar medium, and gravitational potential of the Galactic center. Historical radio observations of the Galactic center have not emphasized the time domain aspect of observing this region. We summarize a series of recent searches for and observations of radio transients and pulsars that make use of two advances in technology. The first is the formation of large fields of view ({approx}> 1{sup 0}) at relatively longer wavelengths ({lambda} > 1 m), and the second is the construction of receivers and instruments capable of collecting data on microsecond time scales at relatively short wavelengths ({approx} 3 cm)

  15. Do the enigmatic ``Infrared-Faint Radio Sources'' include pulsars?

    Science.gov (United States)

    Hobbs, George; Middelberg, Enno; Norris, Ray; Keith, Michael; Mao, Minnie; Champion, David

    2009-04-01

    The Australia Telescope Large Area Survey (ATLAS) team have surveyed seven square degrees of sky at 1.4GHz. During processing some unexpected infrared-faint radio sources (IFRS sources) were discovered. The nature of these sources is not understood, but it is possible that some of these sources may be pulsars within our own galaxy. We propose to observe the IFRS sources with steep spectral indices using standard search techniques to determine whether or not they are pulsars. A pulsar detection would 1) remove a subset of the IFRS sources from the ATLAS sample so they would not need to be observed with large optical/IR telescopes to find their hosts and 2) be intrinsically interesting as the pulsar would be a millisecond pulsar and/or have an extreme spatial velocity.

  16. Binary pulsar with a very small mass function

    Science.gov (United States)

    Dewey, R. J.; Maguire, C. M.; Rawley, L. A.; Stokes, G. H.; Taylor, J. H.

    1986-08-01

    Radiotelescope pulse-arrival-time (PAT) data of PSR1831-00, primarily at 390 MHz, were collected to characterize the evolution of the binary pulsars. The data were used to calculate, the right ascension and declination, pulsar and orbital periods, dispersion measure, semi-major axis, eccentricity, and time of periastron. The orbital period and semi-major axis are used to calculate the mass function. Comparisons are made with other binary and millisecond pulsars, noting the high degree of similarity with the other objects. The limitations imposed on the evolution of the objects by the observed physical characteristics lead to two possible evolutionary models: mass transfer after or during the formation of the neutron star, or no mass transfer. The first model would have required a contact phase during evolution of the primary. The second model posits a three solar mass primary which was also in contact during its evolution and which went to supernova.

  17. On the high frequency polarization of pulsar radio emission

    CERN Document Server

    Von Hoensbroech, A; Krawczyk, A

    1998-01-01

    We have analyzed the polarization properties of pulsars at an observing frequency of 4.9 GHz. Together with low frequency data, we are able to trace polarization profiles over more than three octaves into an interesting frequency regime. At those high frequencies the polarization properties often undergo important changes such as significant depolarization. A detailed analysis allowed us to identify parameters, which regulate those changes. A significant correlation was found between the integrated degree of polarization and the loss of rotational energy E^dot. The data were also used to review the widely established pulsar profile classification scheme of core- and cone-type beams. We have discovered the existence of pulsars which show a strongly increasing degree of circular polarization towards high frequencies. Previously unpublished average polarization profiles, recorded at the 100m Effelsberg radio telescope, are presented for 32 radio pulsars at 4.9 GHz. The data were used to derive polarimetric param...

  18. An exact solution of Haugan's binary pulsar equation of motion

    Science.gov (United States)

    Weinstein, M.; Mor, A.

    1988-05-01

    In his work on the post-Newtonian arrival-time analysis for a pulsary binary system, Haugan (1985) derived and integrated the two-body equation of the motion of the pulsar. The purpose of the present study is to show that there is an exact solution to this nonlinear equation, without any need of far-reaching assumptions and neglected nonlinear terms.

  19. Youngest Radio Pulsar Revealed with Green Bank Telescope

    Science.gov (United States)

    2002-04-01

    Astronomers using the National Science Foundation's (NSF) newly commissioned Robert C. Byrd Green Bank Telescope (GBT) have detected remarkably faint radio signals from an 820 year-old pulsar, making it the youngest radio-emitting pulsar known. This discovery pushes the boundaries of radio telescope sensitivity for discovering pulsars, and will enable scientists to conduct observations that could lead to a better understanding of how these stars evolve. The Robert C. Byrd Green Bank Telescope Robert C. Byrd Green Bank Telescope "Important questions about pulsars may be answered by long-term monitoring of objects such as the one we just detected," said Fernando Camilo of Columbia University in New York City. "Young pulsars are particularly rare, and being able to study such a young one at radio wavelengths provides an outstanding opportunity to learn critical facts about their evolution and workings." The results of this research, based on observations conducted on February 22-23, 2002, were accepted for publication in the Astrophysical Journal Letters. Scientists have long suspected that a pulsar - a rapidly spinning, superdense neutron star - was born when a giant star ended its life in a cataclysmic supernova explosion observed in late summer of 1181, as suggested by Japanese and Chinese historical records. For the past 20 years, astronomers have searched this supernova remnant (3C58), located 10,000 light-years away in the constellation Cassiopeia, for the telltale pulsations of a newly born pulsar. Late in 2001, data from NASA's Chandra X-ray satellite confirmed its existence, but it remained an elusive quarry for radio telescopes. "We believed from historical records and certainly knew from recent X-ray observations that this star was there," Camilo remarked, "but despite many attempts, no one had been able to find any radio pulsations from it because the signals are, it turns out, incredibly weak." For comparison, this pulsar's radio emission is some 250

  20. Five new millisecond pulsars from a radio survey of 14 unidentified Fermi-LAT gamma-ray sources

    NARCIS (Netherlands)

    M. Kerr; F. Camilo; T.J. Johnson; E.C. Ferrara; L. Guillemot; A.K. Harding; J. Hessels; S. Johnston; M. Keith; M. Kramer; S.M. Ransom; P.S. Ray; J.E. Reynolds; J. Sarkissian; K.S. Wood

    2012-01-01

    We have discovered five millisecond pulsars (MSPs) in a survey of 14 unidentified Fermi Large Area Telescope sources in the southern sky using the Parkes radio telescope. PSRs J0101-6422, J1514-4946, and J1902-5105 reside in binaries, while PSRs J1658-5324 and J1747-4036 are isolated. Using an ephem

  1. The Arecibo 430-MHz Intermediate Galactic Latitude Survey: Discovery of Nine Radio Pulsars

    CERN Document Server

    Navarro, J; Freire, P C; Navarro, Jose; Anderson, Stuart; Freire, Paulo C.

    2003-01-01

    We have used the Arecibo Radio Telescope to search for millisecond pulsars in two intermediate Galactic latitude regions (7 deg < | b | < 20 deg) accessible to this telescope. For these latitudes the useful millisecond pulsar search volume achieved by Arecibo's 430-MHz beam is predicted to be maximal. Searching a total of 130 square degrees, we have discovered nine new pulsars and detected four previously known objects. We compare the results of this survey with those of other 430-MHz surveys carried out at Arecibo and of an intermediate latitude survey made at Parkes that included part of our search area; the latter independently found two of the nine pulsars we have discovered. At least six of our discoveries are isolated pulsars with ages between 5 and 300 Myr; one of these, PSR J1819+1305, exhibits very marked and periodic nulling. We have also found a recycled pulsar, PSR J2016+1948. With a rotational period of 65 ms, this is a member of a binary system with a 635-day orbital period. We discuss som...

  2. Developing radio beam geometry and luminosity models of pulsars

    CERN Document Server

    Gonthier, P L; Giacherio, B M; Arevalo, R A; Harding, A K

    2006-01-01

    Our recent studies of pulsar population statistics suggest that improvements of radio and gamma-ray beam geometry and luminosity models require further refinement. The goal of this project is to constrain the viewing geometry for some radio pulsars, especially three-peaked pulse profiles, in order to limit the uncertainty of the magnetic inclination and impact angles. We perform fits of the pulse profile and position angle sweep of radio pulsars for the available frequencies. We assume a single core and conal beams described by Gaussians. We incorporate three different size cones with frequency dependence from the work of Mitra & Deshpande (1999). We obtain separate spectral indices for the core and cone beams and explore the trends of the ratio of core to cone peak fluxes. This ratio is observed to have some dependence with period. However, we cannot establish the suggested functional form of this ratio as indicated by the work of Arzoumanian, Chernoff & Cordes (2002).

  3. X-ray Observations of High-B Radio Pulsars

    CERN Document Server

    Olausen, S A; Vogel, J K; Kaspi, V M; Lyne, A G; Espinoza, C M; Stappers, B W; Manchester, R N; McLaughlin, M A

    2013-01-01

    The study of high-magnetic-field pulsars is important for examining the relationships between radio pulsars, magnetars, and X-ray-isolated neutron stars (XINSs). Here we report on X-ray observations of three such high-magnetic-field radio pulsars. We first present the results of a deep XMM-Newton observation of PSR J1734-3333, taken to follow up on its initial detection in 2009. The pulsar's spectrum is well fit by a blackbody with a temperature of 300 +/- 60 eV, with bolometric luminosity L_bb = 2.0(+2.2 -0.7)e+32 erg/s = 0.0036E_dot for a distance of 6.1 kpc. We detect no X-ray pulsations from the source, setting a 1 sigma upper limit on the pulsed fraction of 60% in the 0.5-3 keV band. We compare PSR J1734-3333 to other rotation-powered pulsars of similar age and find that it is significantly hotter, supporting the hypothesis that the magnetic field affects the observed thermal properties of pulsars. We also report on XMM-Newton and Chandra observations of PSRs B1845-19 and J1001-5939. We do not detect eit...

  4. The LOFAR Pilot Surveys for Pulsars and Fast Radio Transients

    CERN Document Server

    Coenen, Thijs; Hessels, Jason W T; Stappers, Ben W; Kondratiev, Vladislav I; Alexov, A; Breton, R P; Bilous, A; Cooper, S; Falcke, H; Fallows, R A; Gajjar, V; Grießmeier, J -M; Hassall, T E; Karastergiou, A; Keane, E F; Kramer, M; Kuniyoshi, M; Noutsos, A; Osłowski, S; Pilia, M; Serylak, M; Schrijvers, C; Sobey, C; ter Veen, S; Verbiest, J; Weltevrede, P; Wijnholds, S; Zagkouris, K; van Amesfoort, A S; Anderson, J; Asgekar, A; Avruch, I M; Bell, M E; Bentum, M J; Bernardi, G; Best, P; Bonafede, A; Breitling, F; Broderick, J; Brüggen, M; Butcher, H R; Ciardi, B; Corstanje, A; Deller, A; Duscha, S; Eislöffel, J; Fender, R; Ferrari, C; Frieswijk, W; Garrett, M A; de Gasperin, F; de Geus, E; Gunst, A W; Hamaker, J P; Heald, G; Hoeft, M; van der Horst, A; Juette, E; Kuper, G; Law, C; Mann, G; McFadden, R; McKay-Bukowski, D; McKean, J P; Munk, H; Orru, E; Paas, H; Pandey-Pommier, M; Polatidis, A G; Reich, W; Renting, A; Röttgering, H; Rowlinson, A; Scaife, A M M; Schwarz, D; Sluman, J; Smirnov, O; Swinbank, J; Tagger, M; Tang, Y; Tasse, C; Thoudam, S; Toribio, C; Vermeulen, R; Vocks, C; van Weeren, R J; Wucknitz, O; Zarka, P; Zensus, A

    2014-01-01

    We have conducted two pilot surveys for radio pulsars and fast transients with the Low-Frequency Array (LOFAR) around 140 MHz and here report on the first low-frequency fast-radio burst limit and the discovery of two new pulsars. The first survey, the LOFAR Pilot Pulsar Survey (LPPS), observed a large fraction of the northern sky, ~1.4 x 10^4 sq. deg, with 1-hr dwell times. Each observation covered ~75 sq. deg using 7 independent fields formed by incoherently summing the high-band antenna fields. The second pilot survey, the LOFAR Tied-Array Survey (LOTAS), spanned ~600 sq. deg, with roughly a 5-fold increase in sensitivity compared with LPPS. Using a coherent sum of the 6 LOFAR "Superterp" stations, we formed 19 tied-array beams, together covering 4 sq. deg per pointing. From LPPS we derive a limit on the occurrence, at 142 MHz, of dispersed radio bursts of 107 Jy for the narrowest searched burst duration of 0.66 ms. In LPPS, we re-detected 65 previously known pulsars. LOTAS discovered two pulsars, the firs...

  5. A Massive Pulsar in a Compact Relativistic Binary

    CERN Document Server

    Antoniadis, John; Wex, Norbert; Tauris, Thomas M; Lynch, Ryan S; van Kerkwijk, Marten H; Kramer, Michael; Bassa, Cees; Dhillon, Vik S; Driebe, Thomas; Hessels, Jason W T; Kaspi, Victoria M; Kondratiev, Vladislav I; Langer, Norbert; Marsh, Thomas R; McLaughlin, Maura A; Pennucci, Timothy T; Ransom, Scott M; Stairs, Ingrid H; van Leeuwen, Joeri; Verbiest, Joris P W; Whelan, David G; 10.1126/science.1233232

    2013-01-01

    Many physically motivated extensions to general relativity (GR) predict significant deviations in the properties of spacetime surrounding massive neutron stars. We report the measurement of a 2.01 +/- 0.04 solar mass pulsar in a 2.46-hr orbit with a 0.172 +/- 0.003 solar mass white dwarf. The high pulsar mass and the compact orbit make this system a sensitive laboratory of a previously untested strong-field gravity regime. Thus far, the observed orbital decay agrees with GR, supporting its validity even for the extreme conditions present in the system. The resulting constraints on deviations support the use of GR-based templates for ground-based gravitational wave detectors. Additionally, the system strengthens recent constraints on the properties of dense matter and provides insight to binary stellar astrophysics and pulsar recycling.

  6. Is Coherence Essential to Account for Pulsar Radio Emission?

    CERN Document Server

    Zhang, B; Qiao, G J; Zhang, Bing

    1999-01-01

    Based on definitions, two joint-criteria, namely, the optical-thin constraint and the energy budget constraint, are proposed to judge whether the emission nature of radio pulsars is incoherent or obligatory to be coherent. We find that the widely accepted criterion, $kT_B \\le \\epsilon$, is not a rational criterion to describe the optical-thin condition, even for the simplest case. The energy budget constraint could be released by introducing a certain efficient radiation mechanism (e.g. the inverse Compton scattering, QL98) with emission power of a single particle as high as a critical value $P_{sing,c} to interpret high luminosities of pulsars in terms of incoherent emission mechanisms, if the optical-thin constraint could be released by certain mechanism as well. Coherence may not be an essential condition to account for pulsar radio emission.

  7. Sampling the Radio Transient Universe: Studies of Pulsars and the Search for Extraterrestrial Intelligence

    Science.gov (United States)

    Chennamangalam, Jayanth

    The transient radio universe is a relatively unexplored area of astronomy, offering a variety of phenomena, from solar and Jovian bursts, to flare stars, pulsars, and bursts of Galactic and potentially even cosmological origin. Among these, perhaps the most widely studied radio transients, pulsars are fast-spinning neutron stars that emit radio beams from their magnetic poles. In spite of over 40 years of research on pulsars, we have more questions than answers on these exotic compact objects, chief among them the nature of their emission mechanism. Nevertheless, the wealth of phenomena exhibited by pulsars make them one of the most useful astrophysical tools. With their high densities, pulsars are probes of the nature of ultra-dense matter. Characterized by their high timing stability, pulsars can be used to verify the predictions of general relativity, discover planets around them, study bodies in the solar system, and even serve as an interplanetary (and possibly some day, interstellar) navigation aid. Pulsars are also used to study the nature of the interstellar medium, much like a flashlight illuminating airborne dust in a dark room. Studies of pulsars in the Galactic center can help answer questions about the massive black hole in the region and the star formation history in its vicinity. Millisecond pulsars in globular clusters are long-lived tracers of their progenitors, low-mass X-ray binaries, and can be used to study the dynamical history of those clusters. Another source of interest in radio transient astronomy is the hitherto undetected engineered signal from extraterrestrial intelligence. The Search for Extraterrestrial Intelligence (SETI) is an ongoing attempt at discovering the presence of technological life elsewhere in the Galaxy. In this work, I present my forays into two aspects of the study of the radio transient universe---pulsars and SETI. Firstly, I describe my work on the luminosity function and population size of pulsars in the globular

  8. Timing the Eccentric Binary Millisecond Pulsar in NGC 1851

    CERN Document Server

    Freire, P C; Gupta, Y; Freire, Paulo C.; Ransom, Scott M.; Gupta, Yashwant

    2007-01-01

    We have used the Green Bank Telescope to observe the millisecond pulsar PSR J0514-4002A on 43 occasions spread over 2 years. This 5-ms pulsar is located in the globular cluster NGC 1851; it belongs to a binary system and has a highly eccentric (e = 0.888) orbit. We have obtained a phase-coherent timing solution for this object, including very precise position, spin and orbital parameters. The pulsar is located 4.6" (about 1.3 core radii) from the center of the cluster, and is likely to lie on its more distant half. The non-detection of eclipses at superior conjunction can be used, given the peculiar geometry of this system, to rule out the possibility of an extended companion. We have measured the rate of advance of periastron for this binary system to be $\\dot{\\omega}$ = 0.01289(4) degrees per year, which if due completely to general relativity, implies a total system mass of 2.453(14) solar masses. Given the known mass function, the pulsar mass has to be 0.96 solar masses, implying that it is a heavy white...

  9. Swinging between rotation and accretion power in a millisecond binary pulsar

    CERN Document Server

    Papitto, A; Bozzo, E; Rea, N; Pavan, L; Campana, S; Romano, P; Burderi, L; Di Salvo, T; Riggio, A; Torres, D F; Falanga, M; Hessels, J W T; Burgay, M; Sarkissian, J M; Wieringa, M H; Filipović, M D; Wong, G F

    2013-01-01

    Radio pulsars are neutron stars that emit radiation modulated and powered by the rotation of their magnetic field, and which consequently decelerate (Pacini, 1967). The very fast millisecond spin periods measured in old radio pulsars (Backer et al. 1982) are thought to be the outcome of an earlier X-ray bright phase, during which the neutron star accretes matter and angular momentum from a low mass companion star in a binary system (Alpar et al. 1982; Radhakrishnan & Srinivasan 1982). This evolutionary scenario has been supported by the detection of X-ray millisecond pulsations from several accreting neutron stars in the past fifteen years (Wijnands & van der Klis 1998), as well as by the indirect evidence for the presence of a disk in the past around a millisecond radio pulsar now powered by rotation (Archibald et al. 2009). However, a transition between a rotation-powered and an accretion-powered state was never observed. Here we present the detection of millisecond X-ray pulsations from an accretin...

  10. The Eccentric Binary Millisecond Pulsar in NGC 1851

    CERN Document Server

    Freire, Paulo C C; Gupta, Yashwant

    2007-01-01

    PSR J0514-4002A is a 5-ms pulsar is located in the globular cluster NGC 1851; it belongs to a highly eccentric (e = 0.888) binary system. It is one of the earliest known examples of a numerous and fast-growing class of eccentric binary MSPs recently discovered in globular clusters. Using the GBT, we have obtained a phase-coherent timing solution for the pulsar, which includes a measurement of the rate of advance of periastron: 0.01289(4) degrees per year, which if due completely to general relativity, implies a total system mass of 2.453(14) solar masses. We also derive m_p 0.96 solar masses. The companion is likely to be a massive white dwarf star.

  11. A millisecond pulsar in an extremely wide binary system

    CERN Document Server

    Bassa, C G; Stappers, B W; Tauris, T M; Wevers, T; Jonker, P G; Lentati, L; Verbiest, J P W; Desvignes, G; Graikou, E; Guillemot, L; Freire, P C C; Lazarus, P; Caballero, R N; Champion, D J; Cognard, I; Jessner, A; Jordan, C; Karuppusamy, R; Kramer, M; Lazaridis, K; Lee, K J; Liu, K; Lyne, A G; McKee, J; Oslowski, S; Perrodin, D; Sanidas, S; Shaifullah, G; Smits, R; Theureau, G; Tiburzi, C; Zhu, W W

    2016-01-01

    We report on 22 yrs of radio timing observations of the millisecond pulsar J1024$-$0719 by the telescopes participating in the European Pulsar Timing Array (EPTA). These observations reveal a significant second derivative of the pulsar spin frequency and confirm the discrepancy between the parallax and Shklovskii distances that has been reported earlier. We also present optical astrometry, photometry and spectroscopy of 2MASS J10243869$-$0719190. We find that it is a low-metallicity main-sequence star (K7V spectral type, $\\mathrm{[M/H]}=-1.0$, $T_\\mathrm{eff}=4050\\pm50$ K) and that its position, proper motion and distance are consistent with those of PSR J1024$-$0719. We conclude that PSR J1024$-$0719 and 2MASS J10243869$-$0719190 form a common proper motion pair and are gravitationally bound. The gravitational interaction between the main-sequence star and the pulsar accounts for the spin frequency derivatives, which in turn resolves the distance discrepancy. Our observations suggest that the pulsar and main...

  12. Modified gravity and binary pulsars: the Lorentz violating case

    CERN Document Server

    Blas, Diego

    2016-01-01

    The dynamics of binary pulsars can be used to test different aspects of gravitation. This is particularly important to constrain alternatives to general relativity in regimes which are not probed by other methods. In this short contribution, I will describe the case of theories of gravity without Lorentz invariance. The latter are important in the context of quantum gravity and modify the laws of gravity at basically all scales.

  13. Parkes radio searches of Fermi gamma-ray sources and millisecond pulsar discoveries

    CERN Document Server

    Camilo, F; Ray, P S; Ransom, S M; Sarkissian, J; Cromartie, H T; Johnston, S; Reynolds, J E; Wolff, M T; Freire, P C C; Bhattacharyya, B; Ferrara, E C; Keith, M; Michelson, P F; Parkinson, P M Saz; Wood, K S

    2015-01-01

    In a search with the Parkes radio telescope of 56 unidentified Fermi-LAT gamma-ray sources, we have detected 11 millisecond pulsars (MSPs), 10 of them discoveries, of which five were reported in Kerr et al. (2012). We did not detect radio pulsations from another six pulsars now known in these sources. We describe the completed survey, which included multiple observations of many targets done to minimize the impact of interstellar scintillation, acceleration effects in binary systems, and eclipses. We consider that 23 of the 39 remaining sources may still be viable pulsar candidates. We present timing solutions and polarimetry for five of the MSPs, and gamma-ray pulsations for PSR J1903-7051 (pulsations for five others were reported in the second Fermi-LAT catalog of gamma-ray pulsars). Two of the new MSPs are isolated and five are in >1 d circular orbits with 0.2-0.3 Msun presumed white dwarf companions. PSR J0955-6150, in a 24 d orbit with a ~0.25 Msun companion but eccentricity of 0.11, belongs to a recentl...

  14. Radio emissions from pulsar companions : a refutable explanation for galactic transients and fast radio bursts

    CERN Document Server

    Mottez, Fabrice

    2014-01-01

    The six known highly dispersed fast radio bursts are attributed to extragalactic radio sources, of unknown origin but extremely energetic. We propose here a new explanation - not requiring an extreme release of energy - involving a body (planet, asteroid, white dwarf) orbiting an extragalactic pulsar. We investigate a theory of radio waves associated to such pulsar-orbiting bodies. We focus our analysis on the waves emitted from the magnetic wake of the body in the pulsar wind. After deriving their properties, we compare them with the observations of various transient radio signals in order to see if they could originate from pulsar-orbiting bodies. The analysis is based on the theory of Alfv\\'en wings: for a body immersed in a pulsar wind, a system of two stationary Alfv\\'en waves is attached to the body, provided that the wind is highly magnetized. When destabilized through plasma instabilities, Alfv\\'en wings can be the locus of strong radio sources convected with the pulsar wind. Assuming a cyclotron mase...

  15. A current circuit model of pulsar radio emission

    CERN Document Server

    Kunzl, T A; Jessner, A; Kunzl, Th.

    2002-01-01

    We present the outline of a new model for the coherent radio emission of pulsars that succeeds in reproducing the energetics and brightness temperatures of the observed radio emission from the observationally deduced distances of 50-100 pulsar radii above the neutron star in a narrow region. The restrictions imposed by energy conservation, plasma dynamics of the coherent radiation process and propagation effects are used to apply the action of a plasma process like coherent inverse Compton scattering (CICS) (see Benford, 1992). In accordance with our findings (Kunzl et al. 1998a) this process requires Lorentz factors of about 10 which are lower than in most other radio emission models. This implies that no significant pair production can take place near the surface and we expect charge densities close to the Goldreich-Julian value (Goldreich & Julian (1969)). To fulfill the energetic and electrodynamic constraints the model requires constant re-acceleration in dissipation regions which can be interpreted ...

  16. Hunting for Orphaned Central Compact Objects among Radio Pulsars

    CERN Document Server

    Luo, J; Ho, W C G; Bogdanov, S; Kaspi, V M; He, C

    2015-01-01

    Central compact objects (CCOs) are a handful of young neutron stars found at the center of supernova remnants (SNRs). They show high thermal X-ray luminosities but no radio emission. Spin-down rate measurements of the three CCOs with X-ray pulsations indicate surface dipole fields much weaker than those of typical young pulsars. To investigate if CCOs and known radio pulsars are objects at different evolutionary stages, we carried out a census of all weak-field (<1e11 G) isolated radio pulsars in the Galactic plane to search for CCO-like X-ray emission. None of the 12 candidates is detected at X-ray energies, with luminosity limits of 1e32-1e34 erg/s. We consider a scenario in which the weak surface fields of CCOs are due to rapid accretion of supernova materials and show that as the buried field diffuses back to the surface, a CCO descendant is expected to leave the P-Pdot parameter space of our candidates at a young age of a few times 10kyr. Hence, the candidates are likely to be just old ordinary pulsar...

  17. Radio pulsar death lines to SGRs/AXPs and white dwarfs pulsars

    Energy Technology Data Exchange (ETDEWEB)

    Lobato, Ronaldo V.; Malheiro, M. [Departamento de Física, Instituto Tecnológico de Aeronáutica, ITA - DCTA, Vila das Acácias, São José dos Campos, 12228-900 SP (Brazil); Coelho, J. G. [INPE - Instituto Nacional de Pesquisas Espaciais, Divisão de Astrofísica, Av. dos Astronautas 1758, São José dos Campos, 12227-010 SP (Brazil)

    2015-12-17

    Recently, an alternative model based on white dwarfs pulsars has been proposed to explain a class of pulsars known as Soft Gamma Repeaters (SGR) and Anomalus X-Ray Pulsars (AXP) [1], usually named as magnetars. In this model, the magnetized white dwarfs can have surface magnetic field B ∼ 10{sup 7} − 10{sup 10} G and rotate very fast with angular frequencies Ω ∼ 1 rad/s, allowing them to produce large electromagnetic (EM) potentials and generate electron-positron pairs. These EM potentials are comparable with the ones of neutron star pulsars with strong magnetic fields and even larger. In this study we consider two possible processes associated with the particle acceleration, both of them are common used to explain radio emission in neutron star pulsars: in the first process the pair production happens near to the star polar caps, i.e. inside of the light cylinder where magnetic field lines are closed; in the second one the creation of pair happens in the outer magnetosphere, i.e. far away of the star surface where magnetic field lines are open [2]. The analysis of the possibility of radio emission were done for 23 SGRs/AXPs of the McGill Online Magnetar Catalog [3] that contains the current information available on these sources. The results of this work show that the model where the particles production occur in the outer magnetosphere emission “o2” is the process compatible with the astronomical observations of absence of radio emission for almost all SGRs/AXPs when these sources are understood as white dwarf pulsars. Our work is a first attempted to find an explanation for the puzzle why for almost all the SGRs/AXPs was expected radio emission, but it was observed in only four of them. These four sources, as it was suggested recently [4], seem to belong to an high magnetic field neutron star pulsar category, different from all the others SGRs/AXPs that our work indicate to belong to a new class of white dwarf pulsars, very fast and magnetized.

  18. Radio pulsar death lines to SGRs/AXPs and white dwarfs pulsars

    Science.gov (United States)

    Lobato, Ronaldo V.; Coelho, J. G.; Malheiro, M.

    2015-12-01

    Recently, an alternative model based on white dwarfs pulsars has been proposed to explain a class of pulsars known as Soft Gamma Repeaters (SGR) and Anomalus X-Ray Pulsars (AXP) [1], usually named as magnetars. In this model, the magnetized white dwarfs can have surface magnetic field B ˜ 107 - 1010 G and rotate very fast with angular frequencies Ω ˜ 1 rad/s, allowing them to produce large electromagnetic (EM) potentials and generate electron-positron pairs. These EM potentials are comparable with the ones of neutron star pulsars with strong magnetic fields and even larger. In this study we consider two possible processes associated with the particle acceleration, both of them are common used to explain radio emission in neutron star pulsars: in the first process the pair production happens near to the star polar caps, i.e. inside of the light cylinder where magnetic field lines are closed; in the second one the creation of pair happens in the outer magnetosphere, i.e. far away of the star surface where magnetic field lines are open [2]. The analysis of the possibility of radio emission were done for 23 SGRs/AXPs of the McGill Online Magnetar Catalog [3] that contains the current information available on these sources. The results of this work show that the model where the particles production occur in the outer magnetosphere emission "o2" is the process compatible with the astronomical observations of absence of radio emission for almost all SGRs/AXPs when these sources are understood as white dwarf pulsars. Our work is a first attempted to find an explanation for the puzzle why for almost all the SGRs/AXPs was expected radio emission, but it was observed in only four of them. These four sources, as it was suggested recently [4], seem to belong to an high magnetic field neutron star pulsar category, different from all the others SGRs/AXPs that our work indicate to belong to a new class of white dwarf pulsars, very fast and magnetized.

  19. Long-term observations of the pulsars in 47 Tucanae. I. A study of four elusive binary systems

    CERN Document Server

    Ridolfi, A; Torne, P; Heinke, C O; Berg, M van den; Jordan, C; Kramer, M; Bassa, C G; Sarkissian, J; D'Amico, N; Lorimer, D; Camilo, F; Manchester, R N; Lyne, A

    2016-01-01

    For the past couple of decades, the Parkes radio telescope has been regularly observing the millisecond pulsars in 47 Tucanae (47 Tuc). This long-term timing program was designed to address a wide range of scientific issues related to these pulsars and the globular cluster where they are located. In this paper, the first of a series, we address one of these objectives: the characterization of four previously known binary pulsars for which no precise orbital parameters were known, namely 47 Tuc P, V, W and X (pulsars 47 Tuc R and Y are discussed elsewhere). We determined the previously unknown orbital parameters of 47 Tuc V and X and greatly improved those of 47 Tuc P and W. For pulsars W and X we obtained, for the first time, full coherent timing solutions across the whole data span, which allowed a much more detailed characterization of these systems. 47 Tuc W, a well-known tight eclipsing binary pulsar, exhibits a large orbital period variability, as expected for a system of its class. 47 Tuc X turns out to...

  20. Pulsar timing array based search for supermassive black hole binaries in the SKA era

    CERN Document Server

    Wang, Yan

    2016-01-01

    The advent of next generation radio telescope facilities, such as the Square Kilometer Array (SKA), will usher in an era where a Pulsar Timing Array (PTA) based search for gravitational waves (GWs) will be able to use hundreds of well timed millisecond pulsars rather than the few dozens in existing PTAs. A realistic assessment of the performance of such an extremely large PTA must take into account the data analysis challenge posed by an exponential increase in the parameter space volume due to the large number of so-called pulsar phase parameters. We address this problem and present such an assessment for isolated supermassive black hole binary (SMBHB) searches using a SKA era PTA containing $10^3$ pulsars. We find that an all-sky search will be able to confidently detect non-evolving sources with redshifted chirp mass of $10^{10}$ $M_\\odot$ out to a redshift of about $28$. The detection of GW signals from optically identified SMBHB candidates similar to PSO J334+01 is assured. If no SMBHB detections occur, ...

  1. Discovery of two millisecond pulsars in Fermi sources with the Nancay Radio Telescope

    CERN Document Server

    Cognard, I; Johnson, T J; Smith, D A; Venter, C; Harding, A K; Wolff, M T; Cheung, C C; Donato, D; Abdo, A A; Ballet, J; Camilo, F; Desvignes, G; Dumora, D; Ferrara, E C; Freire, P C C; Grove, J E; Keith, M; Kramer, M; Lyne, A G; Michelson, P F; Parent, D; Ransom, S M; Ray, P S; Romani, R W; Parkinson, P M Saz; Stappers, B W; Theureau, G; Thompson, D J; Weltevrede, P; Wood, K S

    2011-01-01

    We report the discovery of two millisecond pulsars in a search for radio pulsations at the positions of \\emph{Fermi Large Area Telescope} sources with no previously known counterparts, using the Nan\\c{c}ay radio telescope. The two millisecond pulsars, PSRs J2017+0603 and J2302+4442, have rotational periods of 2.896 and 5.192 ms and are both in binary systems with low-eccentricity orbits and orbital periods of 2.2 and 125.9 days respectively, suggesting long recycling processes. Gamma-ray pulsations were subsequently detected for both objects, indicating that they power the associated \\emph{Fermi} sources in which they were found. The gamma-ray light curves and spectral properties are similar to those of previously-detected gamma-ray millisecond pulsars. Detailed modeling of the observed radio and gamma-ray light curves shows that the gamma-ray emission seems to originate at high altitudes in their magnetospheres. Additionally, X-ray observations revealed the presence of an X-ray source at the position of PSR ...

  2. Scattering of pulsar radio emission by the interstellar plasma

    CERN Document Server

    Coles, W A; Gao, J J; Hobbs, G; Verbiest, J P W

    2010-01-01

    We present simulations of scattering phenomena which are important in pulsar observations, but which are analytically intractable. The simulation code, which has also been used for solar wind and atmospheric scattering problems, is available from the authors. These simulations reveal an unexpectedly important role of dispersion in combination with refraction. We demonstrate the effect of analyzing observations which are shorter than the refractive scale. We examine time-of-arrival fluctuations in detail: showing their correlation with intensity and dispersion measure; providing a heuristic model from which one can estimate their contribution to pulsar timing observations; and showing that much of the effect can be corrected making use of measured intensity and dispersion. Finally, we analyze observations of the millisecond pulsar J0437$-$4715, made with the Parkes radio telescope, that show timing fluctuations which are correlated with intensity. We demonstrate that these timing fluctuations can be corrected,...

  3. A massive millisecond pulsar in an eccentric binary

    Science.gov (United States)

    Barr, E. D.; Freire, P. C. C.; Kramer, M.; Champion, D. J.; Berezina, M.; Bassa, C. G.; Lyne, A. G.; Stappers, B. W.

    2017-02-01

    The recent discovery of a population of eccentric (e ˜ 0.1) millisecond pulsar (MSP) binaries with low-mass white dwarf companions in the Galactic field represents a challenge to evolutionary models that explain MSP formation as recycling: All such models predict that the orbits become highly circularized during a long period of accretion. The members of this new population exhibit remarkably similar properties (orbital periods, eccentricities, companion masses, spin periods), and several models have been put forward that suggest a common formation channel. In this work, we present the results of an extensive timing campaign focusing on one member of this new population, PSR J1946+3417. Through the measurement of both the advance of periastron and the Shapiro delay for this system, we determine the mass of the pulsar, mass of the companion and the inclination of the orbit to be 1.828(22) M⊙, 0.2656(19) M⊙ and 76.4 ± 0.6 degrees, respectively, under the assumption that general relativity is the true description of gravity. Notably, this is the third highest mass measured for any pulsar. Using these masses and the astrometric properties of PSR J1946+3417, we examine three proposed formation channels for eccentric MSP binaries. While our results are consistent with circumbinary disc-driven eccentricity growth or neutron star to strange star phase transition, we rule out rotationally delayed accretion-induced collapse as the mechanism responsible for the configuration of the PSR J1946+3417 system.

  4. Arecibo Pulsar Survey Using ALFA. III. Probing Radio Pulsar Intermittency and Transients

    CERN Document Server

    Deneva, J S; McLaughlin, M A; Nice, D J; Lorimer, D R; Crawford, F; Bhat, N D R; Camilo, F; Champion, D J; Freire, P C C; Edel, S; Kondratiev, V I; Hessels, J W T; Jenet, F A; Kasian, L; Kaspi, V M; Krämer, M; Lazarus, P; Van Leeuwen, J; Ransom, S M; Stairs, I H; Stappers, B W; Brazier, A; Venkataraman, A; Zollweg, J A

    2008-01-01

    We present radio transient search algorithms, results, and statistics from the ongoing Arecibo Pulsar ALFA (PALFA) Survey of the Galactic plane. We have discovered seven objects by detecting isolated dispersed pulses and one of the new discoveries has a duty cycle of 0.01%, the smallest known. The impact of selection effects on the detectability and classification of intermittent sources is discussed, and the relative efficiencies of periodicity vs. single pulse searches are compared for various pulsar classes. We find that scintillation, off-axis detection and few rotation periods within an observation may misrepresent normal periodic pulsars as intermittent sources. Finally, we derive constraints on transient pulse rate and flux density from the PALFA survey parameters and results.

  5. Spin Period Evolution of Recycled Pulsar in Accreting Binary

    CERN Document Server

    Wang, J; Zhao, Y H; Kojima, Y; Yin, H X; SOng, L M

    2010-01-01

    We investigate the spin-period evolutions of recycled pulsars in binary accreting systems. Taking both the accretion induced field decay and spin-up into consideration, we calculate their spin-period evolutions influenced by the initial magnetic-field strengths, initial spin-periods and accretion rates, respectively. The results indicate that the minimum spin-period (or maximum spin frequency) of millisecond pulsar (MSP) is independent of the initial conditions and accretion rate when the neutron star (NS) accretes $\\sim> 0.2\\ms$. The accretion torque with the fastness parameter and gravitational wave (GW) radiation torque may be responsible for the formation of the minimum spin-period (maximum spin frequency). The fastest spin frequency (716 Hz) of MSP can be inferred to associate with a critical fastness parameter about $\\omega_{c}=0.55$. Furthermore, the comparisons with the observational data are presented in the field-period ($B-P$) diagram.

  6. Discovery of a millisecond pulsar in the 5.4 day binary 3FGL J1417.5-4402: observing the late phase of pulsar recycling

    CERN Document Server

    Camilo, F; Ransom, S M; Halpern, J P; Bogdanov, S; Kerr, M; Ray, P S; Cordes, J M; Sarkissian, J; Barr, E D; Ferrara, E C

    2016-01-01

    In a search of the unidentified Fermi gamma-ray source 3FGL J1417.5-4402 with the Parkes radio telescope, we discovered PSR J1417-4402, a 2.66 ms pulsar having the same 5.4 day orbital period as the optical and X-ray binary identified by Strader et al. The existence of radio pulsations implies that the neutron star is currently not accreting. Substantial outflows from the companion render the radio pulsar undetectable for more than half of the orbit, and may contribute to the observed Halpha emission. Our initial pulsar observations, together with the optically inferred orbit and inclination, imply a mass ratio of 0.171+/-0.002, a companion mass of M_2=0.33+/-0.03 Msun, and a neutron star mass in the range 1.77radio dispersion measure distance of 1.6 kpc. The smaller distance would reduce the inferred Roche-lobe filling factor, increase the inferred i...

  7. Radio pulsar activity and the crustal Hall drift

    CERN Document Server

    Geppert, U; Melikidze, G

    2013-01-01

    Models of pulsar radio emission that are based on an inner accelerating region require the existence of very strong and small scale surface magnetic field structures at or near the canonical polar cap. The aim of this paper is to identify a mechanism that creates such field structures and maintains them over a pulsar's lifetime. The likely physical process that can create the required 'magnetic spots' is the Hall drift occurring in the crust of a neutron star. It is demonstrated, that the Hall drift can produce small scale strong surface magnetic field anomalies (spots) on timescales of $10^4$ years by means of non-linear interaction between poloidal and toroidal components of the subsurface magnetic field. These anomalies are characterized by strengths of about $10^{14}$ G and curvature radii of field lines of about $10^6$ cm, both of which are fundamental for generation of observable radio emission.

  8. Elementary Wideband Timing of Radio Pulsars

    CERN Document Server

    Pennucci, Timothy T; Ransom, Scott M

    2014-01-01

    We present an algorithm for the simultaneous measurement of a pulse time-of-arrival (TOA) and dispersion measure (DM) from folded wideband pulsar data. We extend the prescription put forth by Taylor (1992) to accommodate a general two-dimensional template ``portrait'', the alignment of which can be used to measure a pulse phase and DM. We show that there is a dedispersion reference frequency that removes the covariance between the two measured quantities, and note that the recovered pulse profile scaling amplitudes can provide useful information. We experiment with pulse modeling by using Gaussian-component scheme that allows for independent component evolution with frequency, a ``fiducial component'', and the inclusion of scattering. A demonstration on three years of wideband data on the bright millisecond pulsar J1824-2452A (M28A) from the Green Bank Telescope, and a suite of Monte Carlo analyses showcase and validate the algorithm. By using a simple model portrait of M28A we obtain DM trends comparable to ...

  9. Statistical study of the pulse width distribution for radio pulsars

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Pulse widths of standard pulse profiles for 262 pulsars were measured by using the Urumqi 25 m radio telescope at 1.54 GHz.For the simplest case of circular emission beam,we applied Monte Carlo simulations to the pulse width distribution.Different density functions of magnetic inclination angle α and observer angle ξ were considered.Using Kolmogorov-Smirnov tests,we derived the most probable distribution for α and ξ.

  10. Arecibo PALFA survey and Einstein@Home: binary pulsar discovery by volunteer computing

    NARCIS (Netherlands)

    Knispel, B.; Lazarus, P.; Allen, B.; Anderson, D.; Aulbert, C.; Bhat, N.D.R.; Bock, O.; Bogdanov, S.; Brazier, A.; Camilo, F.; Chatterjee, S.; Cordes, J.M.; Crawford, F.; Deneva, J.S.; Desvignes, G.; Fehrmann, H.; Freire, P.C.C.; Hammer, D.; Hessels, J.W.T.; Jenet, F.A.; Kaspi, V.M.; Kramer, M.; van Leeuwen, J.; Lorimer, D.R.; Lyne, A.G.; Machenschalk, B.; McLaughlin, M.A.; Messenger, C.; Nice, D.J.; Papa, M.A.; Pletsch, H.J.; Prix, R.; Ransom, S.M.; Siemens, X.; Stairs, I.H.; Stappers, B.W.; Stovall, K.; Venkataraman, A.

    2011-01-01

    We report the discovery of the 20.7 ms binary pulsar J1952+2630, made using the distributed computing project Einstein@Home in Pulsar ALFA survey observations with the Arecibo telescope. Follow-up observations with the Arecibo telescope confirm the binary nature of the system. We obtain a circular o

  11. The Einstein@Home search for radio pulsars and PSR J2007+2722

    CERN Document Server

    Allen, B; Cordes, J M; Deneva, J S; Hessels, J W T; Anderson, D; Aulbert, C; Bock, O; Brazier, A; Chatterjee, S; Demorest, P B; Eggenstein, H B; Fehrmann, H; Gotthelf, E V; Hammer, D; Kaspi, V M; Kramer, M; Lyne, A G; Machenschalk, B; McLaughlin, M A; Messenger, C; Pletsch, H J; Ransom, S M; Stairs, I H; Stappers, B W; Bhat, N D R; Bogdanov, S; Camilo, F; Champion, D J; Crawford, F; Desvignes, G; Freire, P C C; Heald, G; Jenet, F A; Lazarus, P; Lee, K J; van Leeuwen, J; Lynch, R; Papa, M A; Prix, R; Rosen, R; Scholz, P; Siemens, X; Stovall, K; Venkataraman, A; Zhu, W

    2013-01-01

    Einstein@Home aggregates the computer power of hundreds of thousands of volunteers from 192 countries, to search for new neutron stars using data from electromagnetic and gravitational-wave detectors. This paper presents a detailed description of the search for new radio pulsars using PALFA survey data from the Arecibo Observatory. The enormous computing power allows this search to cover a new region of parameter space; it can detect pulsars in binary systems with orbital periods as short as 11 min. We also describe the first Einstein@Home discovery, the 40.8 Hz isolated pulsar PSR J2007+2722, and provide a full timing model. PSR J2007+2722's pulse profile is remarkably wide with emission over almost the entire spin period. This neutron star is most likely a disrupted recycled pulsar, about as old as its characteristic spin-down age of 404 Myr. However there is a small chance that it was born recently, with a low magnetic field. If so, upper limits on the X-ray flux suggest but can not prove that PSR J2007+27...

  12. A Radio Search For Pulsar Companions To SDSS Low-Mass White Dwarfs

    CERN Document Server

    Agueros, Marcel A; Silvestri, Nicole M; Kleinman, S J; Anderson, Scott F; Liebert, James W

    2009-01-01

    We have conducted a search for pulsar companions to 15 low-mass white dwarfs (LMWDs; M < 0.4 M_Sun) at 820 MHz with the NRAO Green Bank Telescope (GBT). These LMWDs were spectroscopically identified in the Sloan Digital Sky Survey (SDSS), and do not show the photometric excess or spectroscopic signature associated with a companion in their discovery data. However, LMWDs are believed to evolve in binary systems and to have either a more massive WD or a neutron star as a companion. Indeed, evolutionary models of low-mass X-ray binaries, the precursors of millisecond pulsars (MSPs), produce significant numbers of LMWDs (e.g., Benvenuto & De Vito 2005), suggesting that the SDSS LMWDs may have neutron star companions. No convincing pulsar signal is detected in our data. This is consistent with the findings of van Leeuwen et al. (2007), who conducted a GBT search for radio pulsations at 340 MHz from unseen companions to eight SDSS WDs (five are still considered LMWDs; the three others are now classified as "...

  13. Tests of Gravitational Symmetries with Radio Pulsars

    CERN Document Server

    Shao, Lijing

    2016-01-01

    Symmetries play important roles in modern theories of physical laws. In this paper, we review several experimental tests of important symmetries associated with the gravitational interaction, including the universality of free fall for self-gravitating bodies, time-shift symmetry in the gravitational constant, local position invariance and local Lorentz invariance of gravity, and spacetime translational symmetries. Recent experimental explorations for post-Newtonian gravity are discussed, of which, those from pulsar astronomy are highlighted. All of these tests, of very different aspects of gravity theories, at very different length scales, favor to very high precision the predictions of the strong equivalence principle (SEP) and, in particular, general relativity which embodies SEP completely. As the founding principles of gravity, these symmetries are motivated to be promoted to even stricter tests in future.

  14. Tests of gravitational symmetries with radio pulsars

    Science.gov (United States)

    Shao, LiJing; Wex, Norbert

    2016-09-01

    Symmetries play important roles in modern theories of physical laws. In this paper, we review several experimental tests of important symmetries associated with the gravitational interaction, including the universality of free fall for self-gravitating bodies, time-shift symmetry in the gravitational constant, local position invariance and local Lorentz invariance of gravity, and spacetime translational symmetries. Recent experimental explorations for post-Newtonian gravity are discussed, of which, those from pulsar astronomy are highlighted. All of these tests, of very different aspects of gravity theories, at very different length scales, favor to very high precision the predictions of the strong equivalence principle (SEP) and, in particular, general relativity which embodies SEP completely. As the founding principles of gravity, these symmetries are motivated to be promoted to even stricter tests in future.

  15. A study of microglitches in Hartebeesthoek radio pulsar

    Science.gov (United States)

    Onuchukwu, C. C.; Chukwude, A. E.

    2016-09-01

    We carried out a statistical analysis of microglitch events on a sample of radio pulsars. The distributions of microglitch events in frequency (ν) and first frequency derivative ({ν'}) indicate that the size of a microglitch and sign combinations of events in ν and {ν'} are purely randomized. Assuming that the probability of a given size of a microglitch event occurring scales inversely as the absolute size of the event in both ν and {ν'}, we constructed a cumulative distribution function (CDF) for the absolute sizes of microglitches. In most of the pulsars, the theoretical CDF matched the observed values. This is an indication that microglitches in pulsar may be interpreted as an avalanche process in which angular momentum is transferred erratically from the flywheel-like superfluid interior to the slowly decelerating solid crust. Analysis of the waiting time indicates that it is purely Poisson distributed with mean microglitch rate spin down rate (r˜-0.6) and the characteristic age of the pulsar (τ) with (r˜-0.4/{-}0.5).

  16. A Shapiro delay detection in the binary system hosting the millisecond pulsar PSR J1910-5959A

    CERN Document Server

    Corongiu, A; Possenti, A; Camilo, F; D'Amico, N; Lyne, A G; Manchester, R N; Sarkissian, J M; Bailes, M; Johnston, S; Kramer, M; van Straten, W

    2012-01-01

    PSR J1910-5959A is a binary pulsar with a helium white dwarf companion located about 6 arcmin from the center of the globular cluster NGC6752. Based on 12 years of observations at the Parkes radio telescope, the relativistic Shapiro delay has been detected in this system. We obtain a companion mass Mc = 0.180+/-0.018Msun (1sigma) implying that the pulsar mass lies in the range 1.1Msun <= Mp <= 1.5Msun. We compare our results with previous optical determinations of the companion mass, and examine prospects for using this new measurement for calibrating the mass-radius relation for helium white dwarfs and for investigating their evolution in a pulsar binary system. Finally we examine the set of binary systems hosting a millisecond pulsar and a low mass helium white dwarf for which the mass of both stars has been measured. We confirm that the correlation between the companion mass and the orbital period predicted by Tauris & Savonije reproduces the observed values but find that the predicted Mp - Pb co...

  17. Modulated Gamma-ray emission from compact millisecond pulsar binary systems

    CERN Document Server

    Bednarek, W

    2013-01-01

    A significant amount of the millisecond pulsars has been discovered within binary systems. In several such binary systems the masses of the companion stars have been derived allowing to distinguish two classes of objects, called the Black Widow and the Redback binaries. Pulsars in these binary systems are expected to produce winds which, colliding with stellar winds, create conditions for acceleration of electrons. These electrons should interact with the anisotropic radiation from the companion stars producing gamma-ray emission modulated with the orbital period of the binary system. We consider the interaction of a millisecond pulsar (MSP) wind with a very inhomogeneous stellar wind from the companion star within binary systems of the Black Widow and Redback types. It is expected that the pulsar wind should mix efficiently with the inhomogeneous stellar wind. Electrons accelerated in such mixed, turbulent winds can interact with the magnetic field and also strong radiation from the companion star producing ...

  18. Multi-wavelength observations of the transitional millisecond pulsar binary XSSJ12270-4859

    CERN Document Server

    de Martino, Domitilla; Belloni, Tomaso; Burgay, Marta; Wilhelmi, Emma De Ona; Li, J; Pellizzoni, Alberto; Possenti, Andrea; Rea, Nanda; Torres, Diego F

    2015-01-01

    We present an analysis of X-ray, Ultraviolet and optical/near-IR photometric data of the transitional millisecond pulsar binary XSSJ12270-4859, obtained at different epochs after the transition to a rotation-powered radio pulsar state. The observations, while confirming the large-amplitude orbital modulation found in previous studies after the state change, also reveal an energy dependence of the amplitudes as well as variations on time scale of months. The amplitude variations are anti-correlated in the X-ray and the UV/optical bands. The average X-ray spectrum is described by a power law with \\Gamma index of 1.07(8) without requiring an additional thermal component. The power law index \\Gamma varies from 1.2 to 1.0 between superior and inferior conjunction of the neutron star. We interpret the observed X-ray behaviour in terms of synchrotron radiation emitted in an extended intrabinary shock, located between the pulsar and the donor star, which is eclipsed due to the companion orbital motion. The G5 type do...

  19. Precision astrometry of pulsars and other compact radio sources in the globular cluster M15

    CERN Document Server

    Kirsten, Franz; Freire, Paulo; Kramer, Michael; Rottmann, Helge; Campbell, Robert M

    2014-01-01

    The globular cluster (GC) M15 (NGC 7078) is host to at least eight pulsars and two low mass X-ray binaries (LMXBs) one of which is also visible in the radio regime. Here we present the results of a multi-epoch global very long baseline interferometry (VLBI) campaign aiming at i) measuring the proper motion of the known compact radio sources, ii) finding and classifying thus far undetected compact radio sources in the GC, and iii) detecting a signature of the putative intermediate mass black hole (IMBH) proposed to reside at the core of M15. We measure the sky motion in right ascension ($\\mu_{\\alpha}$) and declination ($\\mu_{\\delta}$) of the pulsars M15A and M15C and of the LMXB AC211 to be $(\\mu_{\\alpha},\\,\\mu_{\\delta})_{\\text{M15A}}=(-0.54\\pm0.14,\\,-4.33\\pm0.25)\\,$mas$\\,$yr$^{-1}$, $(\\mu_{\\alpha},\\,\\mu_{\\delta})_{\\text{M15C}}=(-0.75\\pm0.09,\\,-3.52\\pm0.13)\\,$mas$\\,$yr$^{-1}$, and $(\\mu_{\\alpha},\\,\\mu_{\\delta})_{\\text{AC211}}=(-0.46\\pm0.08,\\,-4.31\\pm0.20)\\,$mas$\\,$yr$^{-1}$, respectively. Based on these measur...

  20. Impact of the orbital uncertainties on the timing of pulsars in binary systems

    CERN Document Server

    Caliandro, G Andrea; Rea, Nanda

    2012-01-01

    The detection of pulsations from an X-ray binary is an unambiguous signature of the presence of a neutron star in the system. When the pulsations are missed in the radio band, their detection at other wavelengths, like X-ray or gamma-rays, requires orbital demodulation, since the length of the observations are often comparable to, or longer than the system orbital period. The detailed knowledge of the orbital parameters of binary systems plays a crucial role in the detection of the spin period of pulsars, since any uncertainty in their determination translates into a loss in the coherence of the signal during the demodulation process. In this paper, we present an analytical study aimed at unveiling how the uncertainties in the orbital parameters might impact on periodicity searches. We find a correlation between the power of the signal in the demodulated arrival time series and the uncertainty in each of the orbital parameters. This correlation is also a function of the pulsar frequency. We test our analytica...

  1. Fast Radio Burst Discovered in the Arecibo Pulsar ALFA Survey

    CERN Document Server

    Spitler, L G; Hessels, J W T; Lorimer, D R; McLaughlin, M A; Chatterjee, S; Crawford, F; Deneva, J S; Kaspi, V M; Wharton, R S; Allen, B; Bogdanov, S; Brazier, A; Camilo, F; Freire, P C C; Jenet, F A; Karako-Argaman, C; Knispel, B; Lazarus, P; Lee, K J; van Leeuwen, J; Lynch, R; Lyne, A G; Ransom, S M; Scholz, P; Siemens, X; Stairs, I H; Stovall, K; Swiggum, J K; Venkataraman, A; Zhu, W W; Aulbert, C; Fehrmann, H

    2014-01-01

    Recent work has exploited pulsar survey data to identify temporally isolated, millisecond-duration radio bursts with large dispersion measures (DMs). These bursts have been interpreted as arising from a population of extragalactic sources, in which case they would provide unprecedented opportunities for probing the intergalactic medium; they may also be linked to new source classes. Until now, however, all so-called fast radio bursts (FRBs) have been detected with the Parkes radio telescope and its 13-beam receiver, casting some concern about the astrophysical nature of these signals. Here we present FRB 121102, the first FRB discovery from a geographic location other than Parkes. FRB 121102 was found in the Galactic anti-center region in the 1.4-GHz Pulsar ALFA survey with the Arecibo Observatory with a DM = 557.4 $\\pm$ 3 pc cm$^{-3}$, pulse width of $3\\; \\pm 0.5$ ms, and no evidence of interstellar scattering. The observed delay of the signal arrival time with frequency agrees precisely with the expectation...

  2. Differences between radio-loud and radio-quiet gamma-ray pulsars as revealed by Fermi

    CERN Document Server

    Hui, C Y; Takata, J; Ng, C W; Cheng, K S

    2016-01-01

    By comparing the properties of non-recycled radio-loud $\\gamma-$ray pulsars and radio-quiet $\\gamma-$ray pulsars, we have searched for the differences between these two populations. We found that the $\\gamma-$ray spectral curvature of radio-quiet pulsars can be larger than that of radio-loud pulsars. Based on the full sample of non-recycled $\\gamma-$ray pulsars, their distributions of the magnetic field strength at the light cylinder are also found to be different. We notice that this might be resulted from the observational bias. In re-examining the previously reported difference of $\\gamma-$ray-to-X-ray flux ratios, we found the significance can be hampered by their statistical uncertainties. In the context of outer gap model, we discuss the expected properties of these two populations and compare with the possible differences identified in our analysis.

  3. A precise mass measurement of the intermediate-mass binary pulsar PSR J1802-2124

    CERN Document Server

    Ferdman, Robert D; Kramer, Michael; McLaughlin, Maura A; Lorimer, Duncan R; Nice, David J; Manchester, Richard N; Hobbs, George; Lyne, Andrew G; Camilo, Fernando; Possenti, Andrea; Demorest, Paul B; Cognard, Ismael; Desvignes, Gregory; Theureau, Gilles; Faulkner, Andrew; Backer, Donald C

    2010-01-01

    PSR J1802-2124 is a 12.6-ms pulsar in a 16.8-hour binary orbit with a relatively massive white dwarf (WD) companion. These properties make it a member of the intermediate-mass class of binary pulsar (IMBP) systems. We have been timing this pulsar since its discovery in 2002. Concentrated observations at the Green Bank Telescope, augmented with data from the Parkes and Nancay observatories, have allowed us to determine the general relativistic Shapiro delay. This has yielded pulsar and white dwarf mass measurements of 1.24(11) and 0.78(4) solar masses (68% confidence), respectively. The low mass of the pulsar, the high mass of the WD companion, the short orbital period, and the pulsar spin period may be explained by the system having gone through a common-envelope phase in its evolution. We argue that selection effects may contribute to the relatively small number of known IMBPs.

  4. Searching for debris disks around seven radio pulsars

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhongxiang; Wang, Xuebing [Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China); Ng, C.-Y. [Department of Physics, The University of Hong Kong, Pokfulam Road (Hong Kong); Li, Aigen [Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211 (United States); Kaplan, David L. [Physics Department, University of WisconsinMilwaukee, Milwaukee, WI 53211 (United States)

    2014-10-01

    We report on our searches for debris disks around seven relatively nearby radio pulsars, which are isolated sources that were carefully selected as targets on the basis of our deep K{sub s} -band imaging survey. The K{sub s} images obtained with the 6.5 m Baade Magellan Telescope at Las Campanas Observatory are analyzed together with the Spitzer/IRAC images at 4.5 and 8.0 μm and the WISE images at 3.4, 4.6, 12, and 22 μm. No infrared counterparts of these pulsars are found, with flux upper limits of ∼μJy at near-infrared (λ < 10 μm) and ∼10-1000 μJy at mid-infrared wavelengths (λ > 10 μm). The results of this search are discussed in terms of the efficiency of converting the pulsar spin-down energy to thermal energy and X-ray heating of debris disks, with a comparison made of the two magnetars 4U 0142+61 and 1E 2259+586, which are suggested to harbor a debris disk.

  5. Cosmic-Lab: Optical companions to binary Millisecond Pulsars

    CERN Document Server

    Pallanca, Cristina

    2014-01-01

    Millisecond Pulsars (MSPs) are fast rotating, highly magnetized neutron stars. According to the "canonical recycling scenario", MSPs form in binary systems containing a neutron star which is spun up through mass accretion from the evolving companion. Therefore, the final stage consists of a binary made of a MSP and the core of the deeply peeled companion. In the last years, however an increasing number of systems deviating from these expectations has been discovered, thus strongly indicating that our understanding of MSPs is far to be complete. The identification of the optical companions to binary MSPs is crucial to constrain the formation and evolution of these objects. In dense environments such as Globular Clusters (GCs), it also allows us to get insights on the cluster internal dynamics. By using deep photometric data, acquired both from space and ground-based telescopes, we identified 5 new companions to MSPs. Three of them being located in GCs and two in the Galactic Field. The three new identification...

  6. A Massive Millisecond Pulsar in an Eccentric Binary

    CERN Document Server

    Barr, E D; Kramer, M; Champion, D J; Berezina, M; Bassa, C G; Lyne, A G; Stappers, B W

    2016-01-01

    The recent discovery of a population of eccentric (e ~ 0.1) millisecond pulsar (MSP) binaries with low-mass white dwarf companions in the Galactic field represents a challenge to evolutionary models that explain MSP formation as recycling: all such models predict that the orbits become highly circularised during a long period of accretion. The members of this new population exhibit remarkably similar properties (orbital periods, eccentricities, companion masses, spin periods) and several models have been put forward that suggest a common formation channel. In this work we present the results of an extensive timing campaign focusing on one member of this new population, PSR J1946+3417. Through measurement of the both the advance of periastron and Shapiro delay for this system, we determine the mass of the pulsar, companion and the inclination of the orbit to be 1.828(22) Msun, 0.2656(19) Msun and 76.4(6) , under the assumption that general relativity is the true description of gravity. Notably, this is the thi...

  7. An Eccentric Binary Millisecond Pulsar with a Helium White Dwarf Companion in the Galactic field

    Science.gov (United States)

    Antoniadis, John; Kaplan, David L.; Stovall, Kevin; Freire, Paulo C. C.; Deneva, Julia S.; Koester, Detlev; Jenet, Fredrick; Martinez, Jose G.

    2016-10-01

    Low-mass white dwarfs (LMWDs) are believed to be exclusive products of binary evolution, as the universe is not old enough to produce them from single stars. Because of the strong tidal forces operating during the binary interaction phase, the remnant systems observed today are expected to have negligible eccentricities. Here, we report on the first unambiguous identification of an LMWD in an eccentric (e = 0.13) orbit around the millisecond pulsar PSR J2234+0511, which directly contradicts this picture. We use our spectra and radio-timing solution (derived elsewhere) to infer the WD temperature ({T}{{eff}}=8600+/- 190 K), and peculiar systemic velocity relative to the local standard of rest (≃ 31 km s-1). We also place model-independent constraints on the WD radius ({R}{{WD}}={0.024}-0.002+0.004 {R}⊙ ) and surface gravity ({log} g={7.11}-0.16+0.08 dex). The WD and kinematic properties are consistent with the expectations for low-mass X-ray binary evolution and disfavor a dynamic three-body formation channel. In the case of the high eccentricity being the result of a spontaneous phase transition, we infer a mass of ˜1.60 M ⊙ for the pulsar progenitor, which is too low for the quark-nova mechanism proposed by Jiang et al., and too high for the scenario of Freire & Tauris, in which a WD collapses into a neutron star via a rotationally delayed accretion-induced collapse. We find that eccentricity pumping via interaction with a circumbinary disk is consistent with our inferred parameters. Finally, we report tentative evidence for pulsations that, if confirmed, would transform the star into an unprecedented laboratory for WD physics.

  8. Formation of binary millisecond pulsars with relatively high surface dipole magnetic fields

    CERN Document Server

    Sutantyo, W

    2000-01-01

    We have carried out numerical evolutionary calculations of binary systems to investigate the formation of binary millisecond pulsars (pulsars with white dwarf companions). We apply the ``standard scenario'' in which the binary pulsars are formed from low-mass and intermediate-mass X-ray binaries as well the alternative scenario in which the neutron stars are formed by accretion-induced collapse (AIC) of white dwarfs. The mass transfer processes are carefully followed by taking into account a number of binary interactions. Assuming that the magnetic fields of the neutron stars decay due to the accretion, we calculate the pulsar surface dipole magnetic field strength at the end of the mass transfer as a function of the final orbital period. We find that while the observed data of the majority of pulsars are compatible with the derived relations, we fail to produce binary pulsars with relatively high magnetic fields and short orbital periods (such as PSR B0655+64). We conclude that those systems are most likely ...

  9. Fast radio burst discovered in the Arecibo pulsar ALFA survey

    Energy Technology Data Exchange (ETDEWEB)

    Spitler, L. G.; Freire, P. C. C.; Lazarus, P.; Lee, K. J. [Max-Planck-Institut für Radioastronomie, D-53121 Bonn (Germany); Cordes, J. M.; Chatterjee, S.; Wharton, R. S.; Brazier, A. [Department of Astronomy and Space Sciences, Cornell University, Ithaca, NY 14853 (United States); Hessels, J. W. T. [ASTRON, Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA, Dwingeloo (Netherlands); Lorimer, D. R.; McLaughlin, M. A. [Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506 (United States); Crawford, F. [Department of Physics and Astronomy, Franklin and Marshall College, Lancaster, PA 17604-3003 (United States); Deneva, J. S. [Naval Research Laboratory, 4555 Overlook Ave SW, Washington, DC 20375 (United States); Kaspi, V. M.; Karako-Argaman, C. [Department of Physics, McGill University, Montreal, QC H3A 2T8 (Canada); Allen, B. [Physics Department, University of Wisconsin-Milwaukee, Milwaukee, WI 53211 (United States); Bogdanov, S.; Camilo, F. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Jenet, F. A. [Center for Gravitational Wave Astronomy, University of Texas at Brownsville, Brownsville, TX 78520 (United States); Knispel, B., E-mail: lspitler@mpifr-bonn.mpg.de [Leibniz Universität, Hannover, D-30167 Hannover (Germany); and others

    2014-08-01

    Recent work has exploited pulsar survey data to identify temporally isolated, millisecond-duration radio bursts with large dispersion measures (DMs). These bursts have been interpreted as arising from a population of extragalactic sources, in which case they would provide unprecedented opportunities for probing the intergalactic medium; they may also be linked to new source classes. Until now, however, all so-called fast radio bursts (FRBs) have been detected with the Parkes radio telescope and its 13-beam receiver, casting some concern about the astrophysical nature of these signals. Here we present FRB 121102, the first FRB discovery from a geographic location other than Parkes. FRB 121102 was found in the Galactic anti-center region in the 1.4 GHz Pulsar Arecibo L-band Feed Array (ALFA) survey with the Arecibo Observatory with a DM = 557.4 ± 2.0 pc cm{sup –3}, pulse width of 3.0 ± 0.5 ms, and no evidence of interstellar scattering. The observed delay of the signal arrival time with frequency agrees precisely with the expectation of dispersion through an ionized medium. Despite its low Galactic latitude (b = –0.°2), the burst has three times the maximum Galactic DM expected along this particular line of sight, suggesting an extragalactic origin. A peculiar aspect of the signal is an inverted spectrum; we interpret this as a consequence of being detected in a sidelobe of the ALFA receiver. FRB 121102's brightness, duration, and the inferred event rate are all consistent with the properties of the previously detected Parkes bursts.

  10. A SHAPIRO DELAY DETECTION IN THE BINARY SYSTEM HOSTING THE MILLISECOND PULSAR PSR J1910-5959A

    Energy Technology Data Exchange (ETDEWEB)

    Corongiu, A.; Burgay, M.; Possenti, A.; D' Amico, N. [INAF-Osservatorio Astronomico di Cagliari, Loc. Poggio dei Pini, Strada 54, I-09012 Capoterra (Italy); Camilo, F. [Columbia Astrophysics Laboratory, Columbia University, 550 West, 120th Street, New York, NY 10027 (United States); Lyne, A. G.; Kramer, M. [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Manchester, R. N.; Johnston, S. [CSIRO Astronomy and Space Science, Australia Telescope National Facility, P.O. Box 76, Epping, NSW 1710 (Australia); Sarkissian, J. M. [Australia Telescope National Facility, CSIRO, Parkes Observatory, P.O. Box 276, Parkes, NSW 2870 (Australia); Bailes, M.; Van Straten, W. [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, P.O. Box 218 Hawthorn, VIC 3122 (Australia)

    2012-12-01

    PSR J1910-5959A is a binary pulsar with a helium white dwarf (HeWD) companion located about 6 arcmin from the center of the globular cluster NGC 6752. Based on 12 years of observations at the Parkes radio telescope, the relativistic Shapiro delay has been detected in this system. We obtain a companion mass M{sub C} = 0.180 {+-} 0.018 M {sub Sun} (1{sigma}) implying that the pulsar mass lies in the range 1.1 M {sub Sun} {<=} M{sub P} {<=} 1.5 M {sub Sun }. We compare our results with previous optical determinations of the companion mass and examine prospects for using this new measurement for calibrating the mass-radius relation for HeWDs and for investigating their evolution in a pulsar binary system. Finally, we examine the set of binary systems hosting a millisecond pulsar and a low-mass HeWD for which the mass of both stars has been measured. We confirm that the correlation between the companion mass and the orbital period predicted by Tauris and Savonije reproduces the observed values but find that the predicted M{sub P} -P{sub B} correlation overestimates the neutron star mass by about 0.5 M {sub Sun} in the orbital period range covered by the observations. Moreover, a few systems do not obey the observed M{sub P} -P{sub B} correlation. We discuss these results in the framework of the mechanisms that inhibit the accretion of matter by a neutron star during its evolution in a low-mass X-ray binary.

  11. An eccentric binary millisecond pulsar with a helium white dwarf companion in the Galactic Field

    CERN Document Server

    Antoniadis, John; Stovall, Kevin; Freire, Paulo C; Deneva, Julia S; Koester, Detlev; Jenet, Frederick; Martinez, Jose

    2016-01-01

    Low-mass white dwarfs (LMWDs) are believed to be exclusive products of binary evolution, as the Universe is not yet old enough to produce them from single stars. Because of the strong tidal forces operating during the binary interaction phase, the remnant host systems observed today are expected to have negligible eccentricities. Here, we report on the first unambiguous identification of a LMWD in an eccentric (e=0.13) orbit with a millisecond pulsar, which directly contradicts this picture. We use our spectra and radio-timing solution (derived elsewhere) to infer the WD temperature T_eff = 8600 +/- 190 K) and 3D systemic velocity (179.5 km\\s). We also place model-independent constraints on the WD radius (R_WD = 0.024+/- 0.004/0.002 R_sun) and surface gravity (log g = 7.11 +/- 0.08/0.16 dex). The WD and kinematic properties are consistent with the expectations for low-mass X-ray binary evolution and disfavour a three-body formation channel. In the case of the high eccentricity being the result of a spontaneou...

  12. Blind search for radio-quiet and radio-loud gamma-ray pulsars with Fermi-LAT data

    CERN Document Server

    Rubtsov, G I

    2014-01-01

    The Fermi Large Area Telescope (LAT) has observed more than a hundred of gamma-ray pulsars, about one third of which are radio-quiet, i.e. not detected at radio frequencies. The most of radio-loud pulsars are detected by Fermi LAT by using the radio timing models, while the radio-quiet ones are discovered in a blind search. The difference in the techniques introduces an observational selection bias and, consequently, the direct comparison of populations is complicated. In order to produce an unbiased sample, we perform a blind search of gamma-ray pulsations using Fermi-LAT data alone. No radio data or observations at optical or X-ray frequencies are involved in the search process. We produce a gamma-ray selected catalog of 25 non-recycled gamma-ray pulsars found in a blind search, including 16 radio-quiet and 9 radio-loud pulsars. This results in the direct measurement of the fraction of radio-quiet pulsars $\\varepsilon_{RQ} = 64\\pm 10\\%$, which is in agreement with the existing estimates from the population ...

  13. Radio-quiet and radio-loud pulsars: similar in Gamma-rays but different in X-rays

    CERN Document Server

    Marelli, M; De Luca, A; Parkinson, P M Saz; Salvetti, D; Hartog, P R Den; Wolff, M T

    2015-01-01

    We present new Chandra and XMM-Newton observations of a sample of eight radio-quiet Gamma-ray pulsars detected by the Fermi Large Area Telescope. For all eight pulsars we identify the X-ray counterpart, based on the X-ray source localization and the best position obtained from Gamma-ray pulsar timing. For PSR J2030+4415 we found evidence for an about 10 arcsec-long pulsar wind nebula. Our new results consolidate the work from Marelli et al. 2011 and confirm that, on average, the Gamma-ray--to--X-ray flux ratios (Fgamma/Fx) of radio-quiet pulsars are higher than for the radio-loud ones. Furthermore, while the Fgamma/Fx distribution features a single peak for the radio-quiet pulsars, the distribution is more dispersed for the radio-loud ones, possibly showing two peaks. We discuss possible implications of these different distributions based on current models for pulsar X-ray emission.

  14. Einstein@Home Discovery of 24 Pulsars in the Parkes Multi-beam Pulsar Survey

    OpenAIRE

    Knispel, B.; Eatough, R.; Kim, H.; Keane, E; Allen, B.; Anderson, D; Aulbert, C.; Bock, O.; Crawford, F; Eggenstein, H.; Fehrmann, H.; Hammer, D.; Kramer, M.; Lyne, A,; Machenschalk, B.

    2013-01-01

    We have conducted a new search for radio pulsars in compact binary systems in the Parkes multi-beam pulsar survey (PMPS) data, employing novel methods to remove the Doppler modulation from binary motion. This has yielded unparalleled sensitivity to pulsars in compact binaries. The required computation time of approximately 17000 CPU core years was provided by the distributed volunteer computing project Einstein@Home, which has a sustained computing power of about 1 PFlop/s. We discovered 24 n...

  15. The birth of radio millisecond pulsars and their high-energy signature

    CERN Document Server

    Tam, P H T; Kong, A K H; Takata, J; Leung, G C K; Cheng, K S; Hui, C Y

    2014-01-01

    Millisecond pulsars (MSPs) are thought to born in low-mass X-ray binaries when the neutron star has gained enough angular momentum from the accreting materials of its companion star. It is generally believed that a radio MSP is born when the neutron star stops accreting and enters a rotation-powered state. Exactly what happens during the transition time was poorly understood until a year ago. In the past year, observations have revealed a few objects that not only switched from one state to the other (as predicted in the above picture), but also have swung between the two states within weeks to years. In this work, we present observations of two of these transition objects (PSR J1023+0038 and XSS J12270-4859) and a theoretical framework that tries to explain their high-energy radiation.

  16. GAMMA-RAY SIGNAL FROM THE PULSAR WIND IN THE BINARY PULSAR SYSTEM PSR B1259-63/LS 2883

    Energy Technology Data Exchange (ETDEWEB)

    Khangulyan, Dmitry [Institute of Space and Astronautical Science/JAXA, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Aharonian, Felix A. [Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2 (Ireland); Bogovalov, Sergey V. [National Research Nuclear University-MEPHI, Kashirskoe Shosse 31, Moscow 115409 (Russian Federation); Ribo, Marc, E-mail: khangul@astro.isas.jaxa.jp, E-mail: felix.aharonian@dias.ie, E-mail: svbogovalov@mephi.ru, E-mail: mribo@am.ub.es [Departament d' Astronomia i Meteorologia, Institut de Ciences del Cosmos (ICC), Universitat de Barcelona (IEEC-UB), Marti i Franques 1, E-08028 Barcelona (Spain)

    2011-12-01

    Binary pulsar systems emit potentially detectable components of gamma-ray emission due to Comptonization of the optical radiation of the companion star by relativistic electrons of the pulsar wind, both before and after termination of the wind. The recent optical observations of binary pulsar system PSR B1259-63/LS 2883 revealed radiation properties of the companion star which differ significantly from previous measurements. In this paper, we study the implications of these observations for the interaction rate of the unshocked pulsar wind with the stellar photons and the related consequences for fluxes of high energy and very high energy (VHE) gamma rays. We show that the signal should be strong enough to be detected with Fermi close to the periastron passage, unless the pulsar wind is strongly anisotropic or the Lorentz factor of the wind is smaller than 10{sup 3} or larger than 10{sup 5}. The higher luminosity of the optical star also has two important implications: (1) attenuation of gamma rays due to photon-photon pair production and (2) Compton drag of the unshocked wind. While the first effect has an impact on the light curve of VHE gamma rays, the second effect may significantly decrease the energy available for particle acceleration after termination of the wind.

  17. Stokes tomography of radio pulsar magnetospheres. I. Linear polarization

    CERN Document Server

    Chung, C T Y

    2010-01-01

    Polarimetric studies of pulsar radio emission traditionally concentrate on how the Stokes vector (I, Q, U, V) varies with pulse longitude, with special emphasis on the position angle (PA) swing of the linearly polarized component. The interpretation of the PA swing in terms of the rotating vector model is limited by the assumption of an axisymmetric magnetic field and the degeneracy of the output with respect to the orientation and magnetic geometry of the pulsar; different combinations of the latter two properties can produce similar PA swings. This paper introduces Stokes phase portraits as a supplementary diagnostic tool with which the orientation and magnetic geometry can be inferred more accurately. The Stokes phase portraits feature unique patterns in the I-Q, I-U, and Q-U planes, whose shapes depend sensitively on the magnetic geometry, inclination angle, beam and polarization patterns, and emission altitude. We construct look-up tables of Stokes phase portraits and PA swings for pure and current-modif...

  18. A Search for Very High Energy Gamma Rays from the Missing Link Binary Pulsar J1023+0038 with VERITAS

    Science.gov (United States)

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

    2016-11-01

    The binary millisecond radio pulsar PSR J1023+0038 exhibits many characteristics similar to the gamma-ray binary system PSR B1259-63/LS 2883, making it an ideal candidate for the study of high-energy nonthermal emission. It has been the subject of multiwavelength campaigns following the disappearance of the pulsed radio emission in 2013 June, which revealed the appearance of an accretion disk around the neutron star. We present the results of very high energy (VHE) gamma-ray observations carried out by the Very Energetic Radiation Imaging Telescope Array System before and after this change of state. Searches for steady and pulsed emission of both data sets yield no significant gamma-ray signal above 100 GeV, and upper limits are given for both a steady and pulsed gamma-ray flux. These upper limits are used to constrain the magnetic field strength in the shock region of the PSR J1023+0038 system. Assuming that VHE gamma rays are produced via an inverse Compton mechanism in the shock region, we constrain the shock magnetic field to be greater than ˜2 G before the disappearance of the radio pulsar and greater than ˜10 G afterward.

  19. Assessing the effects of timing irregularities on radio pulsars anomalous braking indices

    Science.gov (United States)

    Chukwude, A. E.; Chidi Odo, Finbarr

    2016-10-01

    We investigate the statistical effects of non-discrete timing irregularities on observed radio pulsar braking indices using correlations between the second derivative of the measured anomalous frequency (̈νobs) and some parameters that have been widely used to quantify pulsar timing fluctuations (the timing activity parameter (A), the amount of timing fluctuations absorbed by the cubic term (σR23) and a measure of pulsar rotational stability (σz)) in a large sample of 366 Jodrell Bank Observatory radio pulsars. The result demonstrates that anomalous braking indices are largely artifacts produced by aggregations of fluctuations that occur within or outside the pulsar system. For a subsample of 223 normal radio pulsars whose observed timing activity appeared consistent with instabilities in rotation of the underlying neutron stars (or timing noise) over timescales of ˜ 10 - 40 yr, |̈νobs| strongly correlates (with correlation coefficient |r| ˜ 0.80 - 0.90) with the pulsar timing activity parameters and spin-down properties. On the other hand, no meaningful correlations (r < 0.3) were found between ̈νobs and the timing activity diagnostics and spin-down parameters in the remaining 143 objects, whose timing activity appears significantly dominated by white noise fluctuations. The current result can be better understood if the timing noise in isolated pulsars originates from intrinsic spin-down processes of the underlying neutron stars, but white noise fluctuations largely arise from processes external to the pulsar system.

  20. Pulsar wind model of close massive gamma-ray binaries: The influence of geometry in the pulsar wind zone processes

    CERN Document Server

    Sierpowska-Bartosik, Agnieszka

    2008-01-01

    Several gamma-ray binaries have been recently detected by the High-Energy Stereoscopy Array (H.E.S.S.) and the Major Atmospheric Imaging Cerenkov (MAGIC) telescope. In at least two cases, their nature is unknown, since a distinctive, final observational feature for a black hole or a pulsar compact object companion is still missing. In this paper we aim to provide the details of a theoretical model of close gamma-ray binaries containing a young energetic pulsar as compact object. This model includes a detailed account of the system geometry, the angular dependence of processes such as Klein-Nishina inverse Compton and gamma-gamma absorption, and a Monte Carlo simulation of cascading. We present and derive the used formulae and give all details about their numerical implementation, particularly, on the computation of cascades. In this model, emphasis is put in the processes occurring in the pulsar wind zone of the binary, i.e., the region between the pulsar and the shock in between of the two stars, since as we...

  1. PuMa-II: A wide band pulsar machine for the Westerbork Synthesis Radio Telescope

    NARCIS (Netherlands)

    Karuppusamy, R.; Stappers, B.; van Straten, W.

    2008-01-01

    The Pulsar Machine II (PuMa-II) is the new flexible pulsar processing back-end system at the Westerbork Synthesis Radio Telescope (WSRT), specifically designed to take advantage of the upgraded WSRT. The instrument is based on a computer cluster running the Linux operating system, with minimal custo

  2. The Einstein@Home Search for Radio Pulsars and PSR J2007+2722 Discovery

    NARCIS (Netherlands)

    Allen, B.; Knispel, B.; Cordes, J.M.; Deneva, J.S.; Hessels, J.W.T.; Anderson, D.; Aulbert, C.; Bock, O.; Brazier, A.; Chatterjee, S.; Demorest, P.B.; Eggenstein, H.B.; Fehrmann, H.; Gotthelf, E.V.; Hammer, D.; Kaspi, V.M.; Kramer, M.; Lyne, A.G.; Machenschalk, B.; McLaughlin, M.A.; Messenger, C.; Pletsch, H.J.; Ransom, S.M.; Stairs, I.H.; Stappers, B.W.; Bhat, N.D.R.; Bogdanov, S.; Camilo, F.; Champion, D.J.; Crawford, F.; Desvignes, G.; Freire, P.C.C.; Heald, G.; Jenet, F.A.; Lazarus, P.; Lee, K.J.; van Leeuwen, J.; Lynch, R.; Papa, M.A.; Prix, R.; Rosen, R.; Scholz, P.; Siemens, X.; Stovall, K.; Venkataraman, A.; Zhu, W.

    2013-01-01

    Einstein@Home aggregates the computer power of hundreds of thousands of volunteers from 193 countries, to search for new neutron stars using data from electromagnetic and gravitational-wave detectors. This paper presents a detailed description of the search for new radio pulsars using Pulsar ALFA su

  3. Match filtering approach for signal acquisition in radio-pulsar navigation

    NARCIS (Netherlands)

    Heusdens, R.; Engelen, S.; Buist, P.J.; Noroozi, A.; Sundaramoorthy, P.P.; Verhoeven, C.J.M.; Bentum, M.; Gill, E.K.A.

    2012-01-01

    Pulsars with their periodic pulses and known positions are ideal beacons for navigation. The challenge, however, is the detection of the very weak pulsar signals that are submerged in noise. Radio based approaches allow the use of advanced techniques and methods for the detection and acquisition of

  4. A search for dispersed radio bursts in archival Parkes Multibeam Pulsar Survey data

    CERN Document Server

    Bagchi, Manjari; McLaughlin, Maura

    2012-01-01

    A number of different classes of potentially extra-terrestrial bursts of radio emission have been observed in surveys with the Parkes 64m radio telescope, including "Rotating Radio Transients", the "Lorimer burst" and "perytons". Rotating Radio Transients are radio pulsars which are best detectable in single-pulse searches. The Lorimer burst is a highly dispersed isolated radio burst with properties suggestive of extragalactic origin. Perytons share the frequency-swept nature of the Rotating Radio Transients and Lorimer burst, but unlike these events appear in all thirteen beams of the Parkes Multibeam receiver and are probably a form of peculiar radio frequency interference. In order to constrain these and other radio source populations further, we searched the archival Parkes Multibeam Pulsar Survey data for events similar to any of these. We did not find any new Rotating Radio Transients or bursts like the Lorimer burst. We did, however, discover four peryton-like events. Similar to the perytons, these fou...

  5. Modelling the $\\gamma$-ray and radio light curves of the double pulsar system

    CERN Document Server

    Seyffert, A S; Harding, A K; Johnson, T J

    2014-01-01

    Guillemot et al. recently reported the discovery of $\\gamma$-ray pulsations from the 22.7ms pulsar (pulsar A) in the famous double pulsar system J0737-3039A/B. The $\\gamma$-ray light curve (LC) of pulsar A has two peaks separated by approximately half a rotation, and these are non-coincident with the observed radio and X-ray peaks. This suggests that the $\\gamma$-ray emission originates in a part of the magnetosphere distinct from where the radio and X-ray radiation is generated. Thus far, three different methods have been applied to constrain the viewing geometry of pulsar A (its inclination and observer angles $\\alpha$ and $\\zeta$): geometric modelling of the radio and $\\gamma$-ray light curves, modelling of the position angle sweep in phase seen in the radio polarisation data, and independent studies of the time evolution of the radio pulse profile of pulsar A. These three independent, complementary methods have yielded consistent results: pulsar A's rotation axis is likely perpendicular to the orbital pla...

  6. A radio pulsing white dwarf binary star

    CERN Document Server

    Marsh, T R; Hümmerich, S; Hambsch, F -J; Bernhard, K; Lloyd, C; Breedt, E; Stanway, E R; Steeghs, D T; Parsons, S G; Toloza, O; Schreiber, M R; Jonker, P G; van Roestel, J; Kupfer, T; Pala, A F; Dhillon, V S; Hardy, L K; Littlefair, S P; Aungwerojwit, A; Arjyotha, S; Koester, D; Bochinski, J J; Haswell, C A; Frank, P; Wheatley, P J

    2016-01-01

    White dwarfs are compact stars, similar in size to Earth but ~200,000 times more massive. Isolated white dwarfs emit most of their power from ultraviolet to near-infrared wavelengths, but when in close orbits with less dense stars, white dwarfs can strip material from their companions, and the resulting mass transfer can generate atomic line and X-ray emission, as well as near- and mid-infrared radiation if the white dwarf is magnetic. However, even in binaries, white dwarfs are rarely detected at far-infrared or radio frequencies. Here we report the discovery of a white dwarf / cool star binary that emits from X-ray to radio wavelengths. The star, AR Scorpii (henceforth AR Sco), was classified in the early 1970s as a delta-Scuti star, a common variety of periodic variable star. Our observations reveal instead a 3.56 hr period close binary, pulsing in brightness on a period of 1.97 min. The pulses are so intense that AR Sco's optical flux can increase by a factor of four within 30 s, and they are detectable a...

  7. The High Time Resolution Universe Pulsar Survey - VII: discovery of five millisecond pulsars and the different luminosity properties of binary and isolated recycled pulsars

    CERN Document Server

    Burgay, M; Bates, S D; Bhat, N D R; Burke-Spolaor, S; Champion, D J; Coster, P; D'Amico, N; Johnston, S; Keith, M J; Kramer, M; Levin, L; Lyne, A G; Milia, S; Ng, C; Possenti, A; Stappers, B W; Thornton, D; Tiburzi, C; van Straten, W; Bassa, C G

    2013-01-01

    This paper presents the discovery and timing parameters for five millisecond pulsars (MSPs), four in binary systems with probable white dwarf companions and one isolated, found in ongoing processing of the High Time Resolution Universe Pulsar Survey (HTRU). We also present high quality polarimetric data on four of them. These further discoveries confirm the high potential of our survey in finding pulsars with very short spin periods. At least two of these five MSPs are excellent candidates to be included in the Pulsar Timing Array projects. Thanks to the wealth of MSP discoveries in the HTRU survey, we revisit the question of whether the luminosity distributions of isolated and binary MSPs are different. Using the Cordes and Lazio distance model and our new and catalogue flux density measurements, we find that 41 of the 42 most luminous MSPs in the Galactic disk are in binaries and a statistical analysis suggests that the luminosity functions differ with 99.9% significance. We conclude that the formation proc...

  8. Radio emission from RS CVn binary systems

    Energy Technology Data Exchange (ETDEWEB)

    Doiron, D.J.

    1984-01-01

    The RS CVn binary stellar systems UX Ari, HR 1099, AR Lac, HR 5110, II Peg, lambda And, and SZ Psc were investigated by use of radio interferometry during the period from July 1982 through August 1983. Interferometry took two forms: Very Large Array (VLA) observations and Very Long Baseline Interferometry (VLBI). The VLA observations determined the characteristic polarization and flux behavior of the centimeter wavelength radio emission. The observed spectral index was near zero during quiescent periods, rising to between 0.5 and 1.0 during active periods. No net linear polarization is observed to a limit of 1.7%. This is expected since the Faraday depth of thermal electrons deduced from x-ray observations is approx. 10/sup 5/. Circular polarization is observed to be less than 20% at all frequencies often with a helicity reversal between 1.6 GHz and 5 GHz. The VLBI observations have shown that the brightness temperatures are often T/sub B/ approx.> 10/sup 10/ /sup 0/K and size sources smaller than or comparable to the overall size of the binary system. These data are consistent with incoherent gyrosynchrotron emission from mildly relativistic electrons which are optically thick to their own radiation at 1.6 GHz and optically thin at 5 GHz and above. The spectral behavior suggests that the radio emission is due to a power-law distribution of electrons.

  9. High-Precision Timing of 5 Millisecond Pulsars: Space Velocities, Binary Evolution and Equivalence Principles

    CERN Document Server

    Gonzalez, M E; Ferdman, R D; Freire, P C C; Nice, D J; Demorest, P B; Ransom, S M; Kramer, M; Camilo, F; Hobbs, G; Manchester, R N; Lyne, A G

    2011-01-01

    We present high-precision timing of five millisecond pulsars (MSPs) carried out for more than seven years; four pulsars are in binary systems and one is isolated. We are able to measure the pulsars' proper motions and derive an estimate for their space velocities. The measured two-dimensional velocities are in the range 70-210 km/s, consistent with those measured for other MSPs. We also use all the available proper motion information for isolated and binary MSPs to update the known velocity distribution for these populations. As found by earlier works, we find that the velocity distribution of binary and isolated MSPs are indistinguishable with the current data. Four of the pulsars in our observing program are highly recycled with low-mass white dwarf companions and we are able to derive accurate binary parameters for these systems. For three of these binary systems we are able to place initial constraints on the pulsar masses with best-fit values in the range 1.0-1.6 M_sun. The implications of the results pr...

  10. Pulsar timing and the detection of black hole binary systems in globular clusters

    CERN Document Server

    Jenet, F A; Lommen, A N; Jenet, Fredrick A.; Creighton, Teviet; Lommen, Andrea

    2005-01-01

    The possible existence of intermediate mass binary black holes (IMBBHs) in globular clusters (GCs) offers a unique geometry in which to detect space-time oscillations. For certain pulsar-IMBBH configurations possible within a GC, the usual far-field plane wave approximation for the IMBBH metric perturbation severely underestimates the magnitude of the induced pulsar pulse time-of-arrival (TOA) fluctuations. In this letter, the expected TOA fluctuations induced by an IMBBH lying close to the line-of-sight between a pulsar and the Earth are calculated for the first time. For an IMBBH consisting of 10 Msolar and 10^3 Msolar components, a 10 year orbital period, and located 0.1 lyr from the Earth-Pulsar line of sight, the induced pulsar timing residual amplitude will be of order 5 to 500 ns.

  11. Discovery of millisecond pulsars in radio searches of southern Fermi LAT sources

    CERN Document Server

    Keith, M J; Ray, P S; Ferrara, E C; Parkinson, P M Saz; Celik, O; Belfiore, A; Donato, D; Cheung, C C; Abdo, A A; Camilo, F; Freire, P C C; Guillemot, L; Harding, A K; Kramer, M; Michelson, P F; Ransom, S M; Romani, R W; Smith, D A; Thompson, D J; Weltevrede, P; Wood, K S

    2011-01-01

    Using the Parkes radio telescope we have carried out deep observations of eleven unassociated gamma-ray sources. Periodicity searches of these data have discovered two millisecond pulsars, PSR J1103-5403 (1FGL J1103.9-5355) and PSR J2241-5236 (1FGL J2241.9-5236), and a long period pulsar, PSR J1604-44 (1FGL J1604.7-4443). In addition we searched for but did not detect any radio pulsations from six gammaray pulsars discovered by the Fermi satellite to a level of - 0.04 mJy (for pulsars with a 10% duty cycle). Timing of the millisecond pulsar PSR J1103-5403 has shown that its position is 9' from the centroid of the gamma-ray source. Since these observations were carried out, independent evidence has shown that 1FGL J1103.9-5355 is associated with the flat spectrum radio source PKS 1101-536. It appears certain that the pulsar is not associated with the gamma-ray source, despite the seemingly low probability of a chance detection of a radio millisecond pulsar. We consider that PSR J1604-44 is a chance discovery o...

  12. NEW DISCOVERIES FROM THE ARECIBO 327 MHz DRIFT PULSAR SURVEY RADIO TRANSIENT SEARCH

    Energy Technology Data Exchange (ETDEWEB)

    Deneva, J. S. [National Research Council, resident at the Naval Research Laboratory, Washington, DC 20375 (United States); Stovall, K. [Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM 87131 (United States); McLaughlin, M. A.; Bagchi, M.; Garver-Daniels, N. [Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506 (United States); Bates, S. D. [The Institute of Mathematical Sciences, Chennai, 600113 (India); Freire, P. C. C.; Martinez, J. G. [Max-Planck-Institut für Radioastronomie, Bonn (Germany); Jenet, F. [Center for Advanced Radio Astronomy, Department of Physics and Astronomy, University of Texas at Brownsville, Brownsville, TX 78520 (United States)

    2016-04-10

    We present Clusterrank, a new algorithm for identifying dispersed astrophysical pulses. Such pulses are commonly detected from Galactic pulsars and rotating radio transients (RRATs), which are neutron stars with sporadic radio emission. More recently, isolated, highly dispersed pulses dubbed fast radio bursts (FRBs) have been identified as the potential signature of an extragalactic cataclysmic radio source distinct from pulsars and RRATs. Clusterrank helped us discover 14 pulsars and 8 RRATs in data from the Arecibo 327 MHz Drift Pulsar Survey (AO327). The new RRATs have DMs in the range 23.5–86.6 pc cm{sup −3} and periods in the range 0.172–3.901 s. The new pulsars have DMs in the range 23.6–133.3 pc cm{sup −3} and periods in the range 1.249–5.012 s, and include two nullers and a mode-switching object. We estimate an upper limit on the all-sky FRB rate of 10{sup 5} day{sup −1} for bursts with a width of 10 ms and flux density ≳83 mJy. The DMs of all new discoveries are consistent with a Galactic origin. In comparing statistics of the new RRATs with sources from the RRATalog, we find that both sets are drawn from the same period distribution. In contrast, we find that the period distribution of the new pulsars is different from the period distributions of canonical pulsars in the ATNF catalog or pulsars found in AO327 data by a periodicity search. This indicates that Clusterrank is a powerful complement to periodicity searches and uncovers a subset of the pulsar population that has so far been underrepresented in survey results and therefore in Galactic pulsar population models.

  13. Einstein@Home Discovery of a PALFA Millisecond Pulsar in an Eccentric Binary Orbit

    NARCIS (Netherlands)

    Knispel, B.; Lyne, A.G.; Stappers, B.W.; Freire, P.C.C.; Lazarus, P.; Allen, B.; Aulbert, C.; Bock, O.; Bogdanov, S.; Brazier, A.; Camilo, F.; Cardoso, F.; Chatterjee, S.; Cordes, J.M.; Crawford, F.; Deneva, J.S.; Eggenstein, H.B.; Fehrmann, H.; Ferdman, R.; Hessels, J.W.T.; Jenet, F.A.; Karako-Argaman, C.; Kaspi, V.M.; van Leeuwen, J.; Lorimer, D.R.; Lynch, R.; Machenschalk, B.; Madsen, E.; McLaughlin, M.A.; Patel, C.; Ransom, S.M.; Scholz, P.; Siemens, X.; Spitler, L.G.; Stairs, I.H.; Stovall, K.; Swiggum, J.K.; Venkataraman, A.; Wharton, R.S.; Zhu, W.W.

    2015-01-01

    We report the discovery of the millisecond pulsar (MSP) PSR J1950+2414 (P = 4.3 ms) in a binary system with an eccentric (e = 0.08) 22 day orbit in Pulsar Arecibo L-band Feed Array survey observations with the Arecibo telescope. Its companion star has a median mass of 0.3 M⊙ and is most likely a whi

  14. Spectral indices for radio emission of 228 pulsars

    Science.gov (United States)

    Han, Jun; Wang, Chen; Xu, Jun; Han, Jin-Lin

    2016-10-01

    We determine spectral indices of 228 pulsars by using Parkes pulsar data observed at 1.4 GHz, among which 200 spectra are newly determined. The indices are distributed in the range from ‑4.84 to ‑0.46. Together with known pulsar spectra from literature, we tried to find clues to the pulsar emission process. The weak correlations between the spectral index, the spin-down energy loss rate E and the potential drop in the polar gap ΔΨ hint that emission properties are related to the particle acceleration process in a pulsar's magnetosphere.

  15. 2FGL J1653.6-0159: A New Low in Evaporating Pulsar Binary Periods

    CERN Document Server

    Romani, Roger W; Cenko, S Bradley

    2014-01-01

    We have identified an optical binary with orbital period P_b=4488s as the probable counterpart of the Fermi source 2FGL J1653.6-0159. Although pulsations have not yet been detected, the source properties are consistent with an evaporating millisecond pulsar binary; this P_b=75min is the record low for a spin-powered system. The heated side of the companion shows coherent radial velocity variations, with amplitude K=666.9+/-7.5 km/s for a large mass function of f(M)=1.60+/-0.05 M_sun. This heating suggests a pulsar luminosity ~3x10^34 erg/s. The colors and spectra show additional hard emission dominating at binary minimum. This system is similar to PSR J1311-3430, with a low mass H-depleted companion, a dense shrouding wind and, likely, a large pulsar mass.

  16. X-ray emission from the double neutron star binary B1534+12: Powered by the pulsar wind?

    CERN Document Server

    Kargaltsev, O; Garmire, G P

    2006-01-01

    We report the detection of the double neutron star binary (DNSB) B1534+12 (= J1537+1155) with the Chandra X-ray Observatory. This DNSB (orbital period 10.1 hr) consists of the millisecond (recycled) pulsar J1537+1155A (P_A=37.9 ms) and a neutron star not detected in the radio. After the remarkable double pulsar binary J0737-3039, it is the only other DNSB detected in X-rays. We measured the flux of (2.2\\pm 0.6)\\times10^{-15} ergs s^{-1} cm^{-2} in the 0.3-6 keV band. The small number of collected counts allows only crude estimates of spectral parameters. The power-law fit yields the photon index of 3.2\\pm 0.5 and the unabsorbed 0.2-10 keV luminosity L_X=6\\times10^{29} ergs s^{-1} = 3\\times 10^{-4}Edot_A, where Edot_A is the spin-down power of J1537+1155A. Alternatively, the spectrum can be fitted by a blackbody model with T = 2.2 MK and the projected emitting area of ~ 5\\times 10^3 m^2. The distribution of photon arrival times over binary orbital phase shows a deficit of X-ray emission around apastron, which ...

  17. Observations and modeling of the companions of short period binary millisecond pulsars: evidence for high-mass neutron stars

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, Joshua; Halpern, Jules [Department of Astronomy, Columbia University, Mail Code 5246, 550 West 120th Street, New York, NY 10027 (United States)

    2014-10-01

    We present observations of fields containing eight recently discovered binary millisecond pulsars using the telescopes at MDM Observatory. Optical counterparts to four of these systems are detected, one of which, PSR J2214+3000, is a novel detection. Additionally, we present the fully phase-resolved B, V, and R light curves of the optical counterparts to two objects, PSR J1810+1744 and PSR J2215+5135 for which we employ model fitting using the eclipsing light curve (ELC) model of Orosz and Hauschildt to measure the unknown system parameters. For PSR J1810+1744, we find that the system parameters cannot be fit even assuming that 100% of the spin-down luminosity of the pulsar is irradiating the secondary, and so radial velocity measurements of this object will be required for the complete solution. However, PSR J2215+5135 exhibits light curves that are extremely well constrained using the ELC model and we find that the mass of the neutron star is constrained by these and the radio observations to be M {sub NS} > 1.75 M {sub ☉} at the 3σ level. We also find a discrepancy between the model temperature and the measured colors of this object, which we interpret as possible evidence for an additional high-temperature source such as a quiescent disk. Given this and the fact that PSR J2215+5135 contains a relatively high mass companion (M {sub c} > 0.1 M {sub ☉}), we propose that similar to the binary pulsar systems PSR J1023+0038 and IGR J18245–2452, the pulsar may transition between accretion- and rotation-powered modes.

  18. RADIO-QUIET AND RADIO-LOUD PULSARS: SIMILAR IN GAMMA-RAYS BUT DIFFERENT IN X-RAYS

    Energy Technology Data Exchange (ETDEWEB)

    Marelli, M.; Mignani, R. P.; Luca, A. De; Salvetti, D. [INAF—Istituto di Astrofisica Spaziale e Fisica Cosmica Milano, via E. Bassini 15, I-20133, Milano (Italy); Parkinson, P. M. Saz [Santa Cruz Institute for Particle Physics, Department of Physics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Hartog, P. R. Den [Stanford University HEPL/KIPAC, 452 Lomita Mall, Stanford, CA 94305-4085 (United States); Wolff, M. T., E-mail: marelli@iasf-milano.inaf.it [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States)

    2015-04-01

    We present new Chandra and XMM-Newton observations of a sample of eight radio-quiet (RQ) γ-ray pulsars detected by the Fermi Large Area Telescope. For all eight pulsars we identify the X-ray counterpart, based on the X-ray source localization and the best position obtained from γ-ray pulsar timing. For PSR J2030+4415 we found evidence for a ∼10″-long pulsar wind nebula. Our new results consolidate the work from Marelli et al. and confirm that, on average, the γ-ray-to-X-ray flux ratios (F{sub γ}/F{sub X}) of RQ pulsars are higher than for the radio-loud (RL) ones. Furthermore, while the F{sub γ}/F{sub X} distribution features a single peak for the RQ pulsars, the distribution is more dispersed for the RL ones, possibly showing two peaks. We discuss possible implications of these different distributions based on current models for pulsar X-ray emission.

  19. Arecibo PALFA Survey and Einstein@Home: Binary Pulsar Discovery by Volunteer Computing

    OpenAIRE

    Knispel, B.; Lazarus, P; Allen, B.; Anderson, D; Aulbert, C.; Bhat, N; Bock, O.; Bogdanov, S.; Brazier, A.; Camilo, F.; S Chatterjee; Cordes, J.; Crawford, F; Deneva, J.; Desvignes, G.

    2011-01-01

    We report the discovery of the 20.7 ms binary pulsar J1952+2630, made using the distributed computing project Einstein@Home in Pulsar ALFA survey observations with the Arecibo telescope. Follow-up observations with the Arecibo telescope confirm the binary nature of the system. We obtain a circular orbital solution with an orbital period of 9.4 hr, a projected orbital radius of 2.8 lt-s, and a mass function of f = 0.15 solar masses by analysis of spin period measurements. No evidence of orbita...

  20. Dispersion by pulsars, magnetars, fast radio bursts and massive electromagnetism at very low radio frequencies

    Science.gov (United States)

    Bentum, Mark J.; Bonetti, Luca; Spallicci, Alessandro D. A. M.

    2017-01-01

    Our understanding of the universe relies mostly on electromagnetism. As photons are the messengers, fundamental physics is concerned in testing their properties. Photon mass upper limits have been earlier set through pulsar observations, but new investigations are offered by the excess of dispersion measure (DM), sometimes observed with pulsar and magnetar data at low frequencies, or with the fast radio bursts (FRBs), of yet unknown origin. Arguments for the excess of DM do not reach a consensus, but are not mutually exclusive. Thus, we remind that for massive electromagnetism, dispersion goes as the inverse of the frequency squared. Thereby, new avenues are offered also by the recently operating ground observatories in 10-80 MHz domain and by the proposed Orbiting Low Frequency Antennas for Radio astronomy (OLFAR). The latter acts as a large aperture dish by employing a swarm of nano-satellites observing the sky for the first time in the 0.1-15 MHz spectrum. The swarm must be deployed sufficiently away from the ionosphere to avoid distorsions from terrestrial interference, especially during solar maxima, and offer stable conditions for calibration during observations.

  1. Dispersion by pulsars, magnetars, fast radio bursts and massive electromagnetism at very low radio frequencies

    CERN Document Server

    Bentum, Mark J; Spallicci, Alessandro D A M

    2016-01-01

    Our understanding of the universe relies mostly on electromagnetism. As photons are the messengers, fundamental physics is concerned in testing their properties. Photon mass upper limits have been earlier set through pulsar observations, but new investigations are offered by the excess of dispersion measure (DM) sometimes observed with pulsar and magnetar data at low frequencies, or with the fast radio bursts (FRBs), of yet unknown origin. Arguments for the excess of DM do not reach a consensus, but are not mutually exclusive. Thus, we remind that for massive electromagnetism, dispersion goes as the inverse of the frequency squared. Thereby, new avenues are offered also by the recently operating ground observatories in 10-80 MHz domain and by the proposed Orbiting Low Frequency Antennas for Radio astronomy (OLFAR). The latter acts as a large aperture dish by employing a swarm of nano-satellites observing the sky for the first time in the 0.1 - 15 MHz spectrum. The swarm must be deployed sufficiently away from...

  2. New millisecond pulsars detected by the Fermi Large Area Telescope and the radio/gamma-ray connection

    CERN Document Server

    Espinoza, C M; Celik, O; Weltevrede, P; Stappers, B W; Smith, D A; Kerr, M; Zavlin, V E; Cognard, I; Eatough, R P; Freire, P C C; Janssen, G H; Camilo, F; Desvignes, G; Hewitt, J W; Hou, X; Johnston, S; Keith, M; Kramer, M; Lyne, A; Manchester, R N; Ransom, S M; Ray, P S; Shannon, R; Theureau, G; Webb, N

    2012-01-01

    We report on the discovery of gamma-ray pulsations from five millisecond pulsars (MSPs) using the Fermi Large Area Telescope (LAT) and timing ephemerides provided by various radio observatories. We also present confirmation of the gamma-ray pulsations from a sixth source, PSR J2051-0827. Five of these six MSPs are in binary systems: PSRs J1713+0747, J1741+1351, J1600-3053 and the two black widow binary pulsars PSRs J0610-2100 and 2051-0827. The only isolated MSP is the nearby PSR J1024-0719, which is also known to emit X-rays. We present X-ray observations in the direction of PSRs J1600-3053 and J2051-0827. While the latter is firmly detected, we an only give upper limits for the X-ray flux of the former. There are no dedicated X-ray observations available for the other 3 objects. The MSPs mentioned above, together with most of the MSPs detected by Fermi, are used to put together a sample of 30 gamma-ray MSPs which is used to study the morphology and phase connection of radio and gamma-ray pulse profiles. We ...

  3. Observing the Plasma-Physical Processes of Pulsar Radio Emission with Arecibo

    Science.gov (United States)

    Rankin, Joanna M.

    2017-01-01

    With their enormous densities and fields, neutron stars entail some of the most exotic physics in the cosmos. Similarly, the physical mechanisms of pulsar radio emission are no less exotic, and we are only now beginning to understand them. The talk will provide an introduction to the phenomenology of radio pulsar emission and focus on those aspects of the exquisite Arecibo observations that bear on their challenging emission physics.The commonalities of the radio beamforms of most slow pulsars (and some millisecond pulsars) argue strongly that their magnetic fields have a nearly dipolar structure at the height of their radio emission regions. These heights can often be determined by aberration/retardation analyses. Similarly, measurement of the orientation of the polarized radio emission with respect to the emitting magnetic field facilitates identification of the physical(X/O) emission modes and study of the plasma coupling to the electromagnetic radiation.While the physics of primary plasma generation above the pulsar polar cap is only beginning to be understood, it is clear that the radio pulsars we see are able to generate copious amounts of electron-positron plasma in their emission regions. Within the nearly dipolar field structure of these emission regions, the plasma density is near to that of the Goldreich-Julian model, and so the physical conditions in these regions can be accurately estimated.These conditions show that the plasma frequencies in the emission regions are much higher than the frequency of the emitted radiation, such that the plasma couples most easily to the extraordinary mode as observed. Therefore, the only surviving emission mechanism is curvature radiation from charged solitons, produced by the two-stream instability. Such soliton emission has probably been observed directly in the Crab pulsar; however, a physical theory of charged soliton radiation does not yet exist.

  4. Extracting the three- and four-graviton vertices from binary pulsars and coalescing binaries

    CERN Document Server

    Cannella, Umberto; Maggiore, Michele; Sanctuary, Hillary; Sturani, Riccardo

    2009-01-01

    Using a formulation of the post-Newtonian expansion in terms of Feynman graphs, we discuss how various tests of General Relativity (GR) can be translated into measurement of the three- and four-graviton vertices. In problems involving only the conservative dynamics of a system, a deviation of the three-graviton vertex from the GR prediction is equivalent, to lowest order, to the introduction of the parameter beta_{PPN} in the parametrized post-Newtonian formalism, and its strongest bound comes from lunar laser ranging, which measures it at the 0.02% level. Deviation of the three-graviton vertex from the GR prediction, however, also affects the radiative sector of the theory. We show that the timing of the Hulse-Taylor binary pulsar provides a bound on the deviation of the three-graviton vertex from the GR prediction at the 0.1% level. For coalescing binaries at interferometers we find that, because of degeneracies with other parameters in the template such as mass and spin, even a third-generation ground-base...

  5. PONDER - A Real time software backend for pulsar and IPS observations at the Ooty Radio Telescope

    CERN Document Server

    Naidu, Arun; Manoharan, P K; Krishnakumar, M A

    2015-01-01

    This paper describes a new real-time versatile backend, the Pulsar Ooty Radio Telescope New Digital Efficient Receiver (PONDER), which has been designed to operate along with the legacy analog system of the Ooty Radio Telescope (ORT). PONDER makes use of the current state of the art computing hardware, a Graphical Processing Unit (GPU) and sufficiently large disk storage to support high time resolution real-time data of pulsar observations, obtained by coherent dedispersion over a bandpass of 16 MHz. Four different modes for pulsar observations are implemented in PONDER to provide standard reduced data products, such as time-stamped integrated profiles and dedispersed time series, allowing faster avenues to scientific results for a variety of pulsar studies. Additionally, PONDER also supports general modes of interplanetary scintillation (IPS) measurements and very long baseline interferometry data recording. The IPS mode yields a single polarisation correlated time series of solar wind scintillation over a b...

  6. Millisecond Pulsar Ages: Implications of Binary Evolution and a Maximum Spin Frequency

    CERN Document Server

    Kiziltan, Bulent

    2009-01-01

    In the absence of constraints from the binary companion or supernova remnant, the standard method for estimating pulsar ages is to infer an age from the rate of spin-down. While the generic spin-down age may give realistic estimates for normal pulsars, it can fail for pulsars with very short periods. Details of the spin-up process during the low mass X-ray binary phase pose additional constraints on the period (P) and spin-down rates (Pdot) that may consequently affect the age estimate. Here, we propose a new recipe to estimate millisecond pulsar (MSP) ages that parametrically incorporates constraints arising from binary evolution and limiting physics. We show that the standard method can be improved by this approach to achieve age estimates closer to the true age whilst the standard spin-down age may over- or under-estimate the age of the pulsar by more than a factor of ~10 in the millisecond regime. We use this approach to analyze the population on a broader scale. For instance, in order to understand the d...

  7. Precession of the Orbital Plane of Binary Pulsars and Significant Variabilities

    Institute of Scientific and Technical Information of China (English)

    Bi-Ping Gong

    2005-01-01

    There are two ways of expressing the precession of orbital plane of a binary pulsar system, given by Barker & O'Connell, Apostolatos et al. and Kidder, respectively. We point out that these two ways actually come from the same Lagrangian under different degrees of freedom. Damour & Schafer and Wex & Kopeikin applied Barker & O'Connell's orbital precession velocity in pulsar timing measurement. This paper applies Apostolatos et al.'s and Kidder's orbital precession velocity. We show that Damour & Schafer's treatment corresponds to negligible Spin-Orbit induced precession of periastron, while Wex & Kopeikin and this paper both found significant (but not equivalent) effects. The observational data of two typical binary pulsars, PSR J2051-0827 and PSR J1713+0747, apparently support a significant Spin-Orbit coupling effect. Specific binary pulsars with orbital plane nearly edge on could discriminate between Wex & Kopeikin and this paper: if the orbital period derivative of the double-pulsar system PSRs J0737-3039 A and B, with orbital inclination angle i =87.7+17 -29 deg, is much larger than that of the gravitational radiation induced one, then the expression in this paper is supported, otherwise Wex & Kopeikin's is supported.

  8. Arecibo PALFA Survey and Einstein@Home: Binary Pulsar Discovery by Volunteer Computing

    Science.gov (United States)

    Knispel, B.; Lazarus, P.; Allen, B.; Anderson, D.; Aulbert, C.; Bhat, N. D. R.; Bock, O.; Bogdanov, S.; Brazier, A.; Camilo, F.; Chatterjee, S.; Cordes, J. M.; Crawford, F.; Deneva, J. S.; Desvignes, G.; Fehrmann, H.; Freire, P. C. C.; Hammer, D.; Hessels, J. W. T.; Jenet, F. A.; Kaspi, V. M.; Kramer, M.; van Leeuwen, J.; Lorimer, D. R.; Lyne, A. G.; Machenschalk, B.; McLaughlin, M. A.; Messenger, C.; Nice, D. J.; Papa, M. A.; Pletsch, H. J.; Prix, R.; Ransom, S. M.; Siemens, X.; Stairs, I. H.; Stappers, B. W.; Stovall, K.; Venkataraman, A.

    2011-05-01

    We report the discovery of the 20.7 ms binary pulsar J1952+2630, made using the distributed computing project Einstein@Home in Pulsar ALFA survey observations with the Arecibo telescope. Follow-up observations with the Arecibo telescope confirm the binary nature of the system. We obtain a circular orbital solution with an orbital period of 9.4 hr, a projected orbital radius of 2.8 lt-s, and a mass function of f = 0.15 M sun by analysis of spin period measurements. No evidence of orbital eccentricity is apparent; we set a 2σ upper limit e <~ 1.7 × 10-3. The orbital parameters suggest a massive white dwarf companion with a minimum mass of 0.95 M sun, assuming a pulsar mass of 1.4 M sun. Most likely, this pulsar belongs to the rare class of intermediate-mass binary pulsars. Future timing observations will aim to determine the parameters of this system further, measure relativistic effects, and elucidate the nature of the companion star.

  9. Arecibo PALFA Survey and Einstein@Home: Binary Pulsar Discovery by Volunteer Computing

    CERN Document Server

    Knispel, B; Allen, B; Anderson, D; Aulbert, C; Bhat, N D R; Bock, O; Bogdanov, S; Brazier, A; Camilo, F; Chatterjee, S; Cordes, J M; Crawford, F; Deneva, J S; Desvignes, G; Fehrmann, H; Freire, P C C; Hammer, D; Hessels, J W T; Jenet, F A; Kaspi, V M; Kramer, M; van Leeuwen, J; Lorimer, D R; Lyne, A G; Machenschalk, B; McLaughlin, M A; Messenger, C; Nice, D J; Papa, M A; Pletsch, H J; Prix, R; Ransom, S M; Siemens, X; Stairs, I H; Stappers, B W; Stovall, K; Venkataraman, A

    2011-01-01

    We report the discovery of the 20.7-ms binary pulsar J1952+2630, made using the distributed computing project Einstein@Home in Pulsar ALFA survey observations with the Arecibo telescope. Follow-up observations with the Arecibo telescope confirm the binary nature of the system. We obtain a circular orbital solution with an orbital period of 9.4 hr, a projected orbital radius of 2.8 lt-s, and a mass function of f = 0.15 solar masses by analysis of spin period measurements. No evidence of orbital eccentricity is apparent; we set a 2-sigma upper limit e < 1.7e-3. The orbital parameters suggest a massive white dwarf companion with a minimum mass of 0.95 solar masses, assuming a pulsar mass of 1.4 solar masses. Most likely, this pulsar belongs to the rare class of intermediate mass binary pulsars. Future timing observations will aim to determine the parameters of this system further, measure relativistic effects, and elucidate the nature of the companion star.

  10. Gravitational waves from resolvable massive black hole binary systems and observations with Pulsar Timing Arrays

    CERN Document Server

    Sesana, A; Volonteri, M

    2008-01-01

    Massive black holes are key components of the assembly and evolution of cosmic structures and a number of surveys are currently on-going or planned to probe the demographics of these objects and to gain insight into the relevant physical processes. Pulsar Timing Arrays (PTAs) currently provide the only means to observe gravitational radiation from massive black hole binary systems with masses >10^7 solar masses. The whole cosmic population produces a stochastic background that could be detectable with upcoming Pulsar Timing Arrays. Sources sufficiently close and/or massive generate gravitational radiation that significantly exceeds the level of the background and could be individually resolved. We consider a wide range of massive black hole binary assembly scenarios, we investigate the distribution of the main physical parameters of the sources, such as masses and redshift, and explore the consequences for Pulsar Timing Arrays observations. Depending on the specific massive black hole population model, we est...

  11. Are there real orthogonal polarization modes in pulsar radio emission?

    Institute of Scientific and Technical Information of China (English)

    徐仁新; 乔国俊

    2000-01-01

    The orthogonal polarization modes (OPM) have been reported observationally and widely accepted by pulsar researchers. However, no acceptable theory can explain the origin of the OPM, which becomes a mystery in pulsar research field. Here a possible way to solve this mystery is pre-sented. We ask a question: Does there exist any real so-called OPM in pulsar radiation? It is proposed that the ’observed OPM’ in individual pulses could be the results of depolarization of pulsar radiation and the observational uncertainties originated f rom polarimeter in observation. A possible method to check this idea is suggested. If the idea is verified, the pulsar research would be influenced significant-ly in theory and in observation.

  12. Are there real orthogonal polarization modes in pulsar radio emission?

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The orthogonal polarization modes (OPM) have been reported observationally and widely accepted by pulsar researchers. However, no acceptable theory can explain the origin of the OPM, which becomes a mystery in pulsar research field. Here a possible way to solve this mystery is presented. We ask a question: Does there exist any real so-called OPM in pulsar radiation? It is proposed that the 'observed OPM' in individual pulses could be the results of depolarization of pulsar radiation and the observational uncertainties originated from polarimeter in observation. A possible method to check this idea is suggested. If the idea is verified, the pulsar research would be influenced significantly in theory and in observation.

  13. Radio emission from the high-mass X-ray binary BP Cru: first detection

    CERN Document Server

    Pestalozzi, M; Hobbs, G; Lopez-Sanchez, A R

    2009-01-01

    BP Cru is a well known high-mass X-ray binary composed of a late B hypergiant (Wray 977) and a neutron star, also observed as the X-ray pulsar GX 301-2. No information about emission from BP Cru in other bands than X-rays and optical has been reported to date in the literature, though massive X-ray binaries containing black holes can have radio emission from a jet. In order to assess the presence of a radio jet, we searched for radio emission towards BP Cru using the Australia Compact Array Telescope during a survey for radio emission from Be/X-ray transients. We probed the 41.5d orbit of BP Cru with the Australia Telescope Compact Array not only close to periastron but also close to apastron. BP Cru was clearly detected in our data on 4, possibly 6, of 12 occasions at 4.8 and 8.6 GHz. Our data suggest that the spectral index of the radio emission is modulated either by the X-ray flux or the orbital phase of the system. We propose that the radio emission of BP Cru probably arises from two components: a persis...

  14. Discovery of an ultracompact gamma-ray millisecond pulsar binary candidate

    CERN Document Server

    Kong, A K H; Hui, C Y; Tam, P H T; Hu, C P; Takata, J; Lin, L C C; Cheng, K S; Yen, T -C; Park, S M; Kim, C L

    2014-01-01

    We report multi-wavelength observations of the unidentified Fermi object 2FGL J1653.6-0159. With the help of high-resolution X-ray observation, we have identified an X-ray and optical counterpart of 2FGL J1653.6-0159. The source exhibits a periodic modulation of 74.93 min in optical and possibly also in X-ray. We suggest that 2FGL J1653.6-0159 is a compact binary system with an orbital period of 74.93 min. Combining the gamma-ray and X-ray properties, 2FGL J1653.6-0159 is potentially a black widow/redback type gamma-ray millisecond pulsar (MSP). The optical and X-ray lightcurve profile shows that the companion is mildly heated by the high-energy emission and the X-rays are from intrabinary shock. Although no radio pulsation has been detected yet, we estimated that the spin period of the MSP is ~2 ms based on a theoretical model. If pulsation can be confirmed in the future, 2FGL J1653.6-0159 will become the first ultracompact rotation-powered MSP.

  15. The Braking Index of Radio-quiet Gamma-ray Pulsar

    CERN Document Server

    Clark, C J; Wu, J; Guillemot, L; Camilo, F; Johnson, T J; Kerr, M; Allen, B; Aulbert, C; Beer, C; Bock, O; Cuéllar, A; Eggenstein, H B; Fehrmann, H; Kramer, M; Machenschalk, B; Nieder, L

    2016-01-01

    We report the discovery and timing measurements of PSR J1208-6238, a young and highly magnetized gamma-ray pulsar, with a spin period of 440 ms. The pulsar was discovered in gamma-ray photon data from the Fermi Large Area Telescope (LAT) during a blind-search survey of unidentified LAT sources, running on the distributed volunteer computing system Einstein@Home. No radio pulsations were detected in dedicated follow-up searches with the Parkes radio telescope, with a flux density upper limit at 1369 MHz of 30 $\\mu$Jy. By timing this pulsar's gamma-ray pulsations, we measure its braking index over five years of LAT observations to be $n = 2.598 \\pm 0.001 \\pm 0.1$, where the first uncertainty is statistical and the second estimates the bias due to timing noise. Assuming its braking index has been similar since birth, the pulsar has an estimated age of around 2,700 yr, making it the youngest pulsar to be found in a blind search of gamma-ray data and the youngest known radio-quiet gamma-ray pulsar. Despite its you...

  16. A Chandra X-Ray observation of the binary millisecond pulsar PSR J1023+0038

    NARCIS (Netherlands)

    Bogdanov, S.; Archibald, A.M.; Hessels, J.W.T.; Kaspi, V.M.; Lorimer, D.; McLaughlin, M.A.; Ransom, S.M.; Stairs, I.H.

    2011-01-01

    We present a Chandra X-Ray Observatory ACIS-S variability, spectroscopy, and imaging study of the peculiar binary containing the millisecond pulsar J1023+0038. The X-ray emission from the system exhibits highly significant (12.5σ) large-amplitude (factor of two to three) orbital variability over the

  17. Search for Differences between Radio-loud and Radio-quiet Gamma-Ray Pulsar Populations with Fermi-LAT Data

    Science.gov (United States)

    Sokolova, E. V.; Rubtsov, G. I.

    2016-12-01

    Observations by the Fermi-Large Area Telescope (LAT) have enabled us to explore the population of non-recycled gamma-ray pulsars with a set of 112 objects. It was recently noted that there are apparent differences in the properties of radio-quiet and radio-loud subsets. In particular, the average observed radio-loud pulsar is younger than the average radio-quiet one and is located at lower Galactic latitude. Even so, the analysis based on the full list of pulsars may suffer from selection effects. Namely, most radio-loud pulsars are first discovered in the radio band, while radio-quiet ones are found using the gamma-ray data. In this work we perform a blind search for gamma-ray pulsars using the Fermi-LAT data alone, using all point sources from the 3FGL catalog as the candidates. Unlike our previous work, the present catalog is constructed with a semi-coherent method based on the time-differencing technique and covers the full range of characteristic ages down to 1 kyr. The search resulted in a catalog of 40 non-recycled pulsars, 25 of which are radio-quiet. All pulsars found in the search were previously known gamma-ray pulsars. We find no statistically significant differences in age or in distributions in Galactic latitude for the radio-loud and radio-quiet pulsars, while the distributions in rotation period are marginally different with a statistical probability of 4× {10}-3. The fraction of radio-quiet pulsars is estimated as {ε }{RQ}=(63+/- 8) % . The results are in agreement with the predictions of the outer magnetosphere models, while the polar cap models are disfavored.

  18. SAS-2 gamma-ray observations of PSR 1747-46. [radio pulsar

    Science.gov (United States)

    Thompson, D. J.; Fichtel, C. E.; Kniffen, D. A.; Ogelman, H. B.; Lamb, R. C.

    1976-01-01

    Evidence is reported for the observation of gamma-ray emission from the radio pulsar PSR 1747-46 by the gamma-ray telescope aboard SAS 2. The evidence is based on the presence of both an approximately 3-sigma enhancement of gamma rays at the pulsar's location and an approximately 4-sigma peak in the phase plot of 79 gamma-ray events whose phase was calculated from the pulsar's known period. The gamma-ray pulsation is found to appear at a phase lag of about 0.16 from that predicted by the radio observations. The pulsed gamma-ray fluxes above 35 MeV and 100 MeV are estimated, and it is shown that the gamma-ray pulse width is similar to the radio pulse width. It is concluded that PSR 1747-46 is a most likely candidate for pulsed gamma-ray emission.

  19. New Discoveries from the Arecibo 327 MHz Drift Pulsar Survey Radio Transient Search

    CERN Document Server

    Deneva, J S; McLaughlin, M A; Bagchi, M; Bates, S D; Freire, P C C; Martinez, J G; Jenet, F; Garver-Daniels, N

    2016-01-01

    We present Clusterrank, a new algorithm for identifying dispersed astrophysical pulses. Such pulses are commonly detected from Galactic pulsars and rotating radio transients (RRATs), which are neutron stars with sporadic radio emission. More recently, isolated, highly dispersed pulses dubbed fast radio bursts (FRBs) have been identified as the potential signature of an extragalactic cataclysmic radio source distinct from pulsars and RRATs. Clusterrank helped us discover 14 pulsars and 8 RRATs in data from the Arecibo 327 MHz Drift Pulsar Survey (AO327). The new RRATs have DMs in the range $23.5 - 86.6$ pc cm$^{-3}$ and periods in the range $0.172 - 3.901$ s. The new pulsars have DMs in the range $23.6 - 133.3$ pc cm$^{-3}$ and periods in the range $1.249 - 5.012$ s, and include two nullers and a mode-switching object. We estimate an upper limit on the all-sky FRB rate of $10^5$ day$^{-1}$ for bursts with a width of 10 ms and flux density $\\gtrsim 83$ mJy. The DMs of all new discoveries are consistent with a G...

  20. FERMI OBSERVATION OF THE TRANSITIONAL PULSAR BINARY XSS J12270–4859

    Energy Technology Data Exchange (ETDEWEB)

    Xing, Yi; Wang, Zhongxiang [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, China (China)

    2015-07-20

    Because of the disappearance of its accretion disk during the time period of 2012 November–December, XSS J12270–4859 has recently been identified as a transitional millisecond pulsar binary, joining PSR J1023+0038. We have carried out a detailed analysis of the Fermi Large Area Telescope data for this binary. While both spectra  are well-described by an exponentially cut-off power law before and after the disk-disappearance transition, which is typical for pulsars’ emissions in Fermi's 0.2–300 GeV band, we have detected a factor of 2 flux decrease related to the transition. A weak orbital modulation is possibly seen, but is only detectable in the after-transition data, making it the same as orbital modulations found in X-rays. In the long-term light curve of the source before the transition, a factor of 3 flux variations are seen. Compared to the properties of J1023+0038, we discuss the implications from these results. We suggest that since the modulation is aligned with the modulations in X-rays in the orbital phase, it possibly arises due to the occultation of the γ-ray emitting region by the companion. The origin of the variations in the long-term light curve is not clear because the source field also contains unidentified radio or X-ray sources and their contamination cannot be excluded. Multi-wavelength observations of the source field will help identify the origin of the variations by detecting any related flux changes from the in-field sources.

  1. Precision astrometry of pulsars and other compact radio sources in the globular cluster M15

    Science.gov (United States)

    Kirsten, Franz; Vlemmings, Wouter; Freire, Paulo; Kramer, Michael; Rottmann, Helge; Campbell, Robert M.

    2014-05-01

    The globular cluster (GC) M15 (NGC 7078) is host to at least eight pulsars and two low mass X-ray binaries (LMXBs), one of which is also visible in the radio regime. Here we present the results of a multi-epoch global very long baseline interferometry (VLBI) campaign aiming at i) measuring the proper motion of the known compact radio sources; ii) finding and classifying thus far undetected compact radio sources in the GC; and iii) detecting a signature of the putative intermediate mass black hole (IMBH) proposed to reside at the core of M15. We measure the sky motion in right ascension (μα) and declination (μδ) of the pulsars M15A and M15C and of the LMXB AC211 to be (μα,μδ)M15A = (-0.54 ± 0.14, -4.33 ± 0.25) mas yr-1, (μα,μδ)M15C = (-0.75 ± 0.09, -3.52 ± 0.13) mas yr-1, and (μα,μδ)AC211 = (-0.46 ± 0.08, - 4.31 ± 0.20) mas yr-1, respectively. Based on these measurements we estimate the global proper motion of M15 to be (μα,μδ) = (-0.58 ± 0.18, -4.05 ± 0.34) mas yr-1. We detect two previously known but unclassified compact sources within our field of view. Our observations indicate that one them is of extragalactic origin while the other one is a foreground source, quite likely an LMXB. The double neutron star system M15C became fainter during the observations, disappeared for one year and is now observable again - an effect possibly caused by geodetic precession. The LMXB AC211 shows a double lobed structure in one of the observations indicative of an outburst during this campaign. With the inclusion of the last two of a total of seven observations we confirm the upper mass limit for a putative IMBH to be M•< 500 M⊙.

  2. The Braking Index of a Radio-quiet Gamma-ray Pulsar

    OpenAIRE

    Clark, C J; Pletsch, H. J.; Wu, J.; Guillemot, L.; Camilo, F.; Johnson, T. J.; Kerr, M.; Allen, B.; Aulbert, C.; Beer, C; Bock, O.; Cuéllar, A.; Eggenstein, H. B.; Fehrmann, H.; Kramer, M.

    2016-01-01

    We report the discovery and timing measurements of PSR J1208-6238, a young and highly magnetized gamma-ray pulsar, with a spin period of 440 ms. The pulsar was discovered in gamma-ray photon data from the Fermi Large Area Telescope (LAT) during a blind-search survey of unidentified LAT sources, running on the distributed volunteer computing system Einstein@Home. No radio pulsations were detected in dedicated follow-up searches with the Parkes radio telescope, with a flux density upper limit a...

  3. A Likely Millisecond Pulsar Binary Counterpart for Fermi Source 2FGL J2039.6-5620

    Science.gov (United States)

    Romani, Roger W.

    2015-10-01

    We have identified an optical/X-ray binary with an orbital period of Pb = 5.47 hr as the likely counterpart of the Fermi source 2FGL J2039.6-5620. GROND, SOAR, and DES observations provide an accurate orbital period and allow us to compare to the light curve of an archival XMM exposure. Like many short-period optical/X-ray binaries associated with Large Area Telescope sources, this may be an interacting (black widow/redback) millisecond pulsar binary. The X-ray light curve is consistent with the emission associated with an intrabinary shock. The optical light curve shows evidence of companion heating, but has a peculiar asymmetric double peak. The nature of this optical structure is not yet clear; additional optical studies and, in particular, detection of an orbital modulation in a γ-ray pulsar are needed to elucidate the nature of this peculiar source.

  4. A model for gamma-ray binaries, based on the effect of pair production feedback in shocked pulsar winds

    CERN Document Server

    Derishev, E

    2016-01-01

    We analyze the model of gamma-ray binaries, consisting of a massive star and a pulsar with ultrarelativistic wind. We consider radiation from energetic particles, accelerated at the pulsar wind termination shock, and feedback of this radiation on the wind through production of secondary electron-positron pairs. We show that the pair feedback limits the Lorentz factor of the pulsar wind and creates a population of very energetic pairs, whose radiation may be responsible for the observed gamma-ray signal.

  5. A Search for Rapidly Spinning Pulsars and Fast Transients in Unidentified Radio Sources with the NRAO 43-Meter Telescope

    CERN Document Server

    Schmidt, Deborah; Langston, Glen; Gilpin, Claire

    2013-01-01

    We have searched 75 unidentified radio sources selected from the NRAO VLA Sky Survey (NVSS) catalog for the presence of rapidly spinning pulsars and short, dispersed radio bursts. The sources are radio bright, have no identifications or optical source coincidences, are more than 5% linearly polarized, and are spatially unresolved in the catalog. If these sources are fast-spinning pulsars (e.g. sub-millisecond pulsars), previous large-scale pulsar surveys may have missed detection due to instrumental and computational limitations, eclipsing effects, or diffractive scintillation. The discovery of a sub-millisecond pulsar would significantly constrain the neutron star equation of state and would have implications for models predicting a rapid slowdown of highly recycled X-ray pulsars to millisecond periods from, e.g., accretion disk decoupling. These same sources were previously searched unsuccessfully for pulsations at 610 MHz with the Lovell Telescope at Jodrell Bank. This new search was conducted at a differe...

  6. Pulsar timing arrays and the challenge of massive black hole binary astrophysics

    CERN Document Server

    Sesana, Alberto

    2014-01-01

    Pulsar timing arrays (PTAs) are designed to detect gravitational waves (GWs) at nHz frequencies. The expected dominant signal is given by the superposition of all waves emitted by the cosmological population of supermassive black hole (SMBH) binaries. Such superposition creates an incoherent stochastic background, on top of which particularly bright or nearby sources might be individually resolved. In this contribution I describe the properties of the expected GW signal, highlighting its dependence on the overall binary population, the relation between SMBHs and their hosts, and their coupling with the stellar and gaseous environment. I describe the status of current PTA efforts, and prospect of future detection and SMBH binary astrophysics.

  7. Shining Light on Quantum Gravity with Pulsar-Black Hole Binaries

    CERN Document Server

    Estes, John; Lippert, Matthew; Simonetti, John H

    2016-01-01

    Pulsars are some of the most accurate clocks found in nature, while black holes offer a unique arena for the study of quantum gravity. As such, pulsar-black hole (PSR-BH) binaries provide ideal astrophysical systems for detecting effects of quantum gravity. With the success of aLIGO and the advent of instruments like the SKA and eLISA, the prospects for discovery of such PSR-BH binaries are very promising. We argue that PSR-BH binaries can serve as ready-made testing grounds for proposed resolutions to the black hole information paradox. We propose using timing signals from a pulsar beam passing through the region near a BH event horizon as a probe of quantum gravitational effects. In particular, we demonstrate that fluctuations of the geometry outside a black hole lead to an increase in the measured root-mean-square deviation of arrival times of pulsar pulses traveling near the horizon. This allows for a clear observational test of the nonviolent nonlocality proposal for black hole information escape. For a ...

  8. Post-outburst radio monitoring of the high magnetic field pulsar PSR J1119-6127

    Science.gov (United States)

    Majid, Walid A.; Pearlman, Aaron B.; Kocz, Jonathan; Prince, Thomas A.; Lippuner, Jonas; Horiuchi, Shinji

    2017-01-01

    We have carried out radio monitoring observations of PSR J11119-6127 following its recent X-ray outburst in July 2016. While initial observations failed to detect the presence of pulsed emission, subsequent observations two weeks later show bright detections of the pulsar at S-band and a significant detection at X-band as the S-band pulse profile returns to a single-peaked shape. From these measurements, we were able to estimate a spectral index over a relatively wide range of radio wavelengths. We also detected an unusual multiple-peaked radio profile and single pulse events. Further observations show an evolving pulse profile that is quite unique among known radio pulsars. PSR J1119-6127 is clearly a transition object, i.e. a high-magnetic field neutron star that is normally a rotation-powered pulsar in radio and X-rays, but also shows transient magnetar-like behavior, i.e. behavior unlikely to be powered solely by rotation, but also by release of stored magnetic energy. We will discuss recent results and implications for understanding the emission behavior of high magnetic field pulsars.This research was performed at the Jet Propulsion Laboratory, California Institute of Technology, under the Research and Technology Development Program, under a contract with the National Aeronautics and Space Administration.

  9. Observing the dynamics of supermassive black hole binaries with pulsar timing arrays.

    Science.gov (United States)

    Mingarelli, C M F; Grover, K; Sidery, T; Smith, R J E; Vecchio, A

    2012-08-24

    Pulsar timing arrays are a prime tool to study unexplored astrophysical regimes with gravitational waves. Here, we show that the detection of gravitational radiation from individually resolvable supermassive black hole binary systems can yield direct information about the masses and spins of the black holes, provided that the gravitational-wave-induced timing fluctuations both at the pulsar and at Earth are detected. This in turn provides a map of the nonlinear dynamics of the gravitational field and a new avenue to tackle open problems in astrophysics connected to the formation and evolution of supermassive black holes. We discuss the potential, the challenges, and the limitations of these observations.

  10. Observing Radio Pulsars in the Galactic Centre with the Square Kilometre Array

    CERN Document Server

    Eatough, R P; Casanellas, J; Chatterjee, S; Cordes, J M; Demorest, P B; Kramer, M; Lee, K J; Liu, K; Ransom, S M; Wex, N

    2015-01-01

    The discovery and timing of radio pulsars within the Galactic centre is a fundamental aspect of the SKA Science Case, responding to the topic of "Strong Field Tests of Gravity with Pulsars and Black Holes" (Kramer et al. 2004; Cordes et al. 2004). Pulsars have in many ways proven to be excellent tools for testing the General theory of Relativity and alternative gravity theories (see Wex (2014) for a recent review). Timing a pulsar in orbit around a companion, provides a unique way of probing the relativistic dynamics and spacetime of such a system. The strictest tests of gravity, in strong field conditions, are expected to come from a pulsar orbiting a black hole. In this sense, a pulsar in a close orbit ($P_{\\rm orb}$ < 1 yr) around our nearest supermassive black hole candidate, Sagittarius A* - at a distance of ~8.3 kpc in the Galactic centre (Gillessen et al. 2009a) - would be the ideal tool. Given the size of the orbit and the relativistic effects associated with it, even a slowly spinning pulsar would...

  11. Simultaneous X-ray and radio observations of the radio-mode-switching pulsar PSR B1822-09

    Science.gov (United States)

    Hermsen, W.; Kuiper, L.; Hessels, J. W. T.; Mitra, D.; Rankin, J. M.; Stappers, B. W.; Wright, G. A. E.; Basu, R.; Szary, A.; van Leeuwen, J.

    2017-04-01

    We report on simultaneous X-ray and radio observations of the radio-mode-switching pulsar PSR B1822-09 with ESA's XMM-Newton and the Westerbork Synthesis Radio Telescope, Giant Metrewave Radio Telescope and Lovell radio telescopes. PSR B1822-09 switches between a radio-bright and radio-quiet mode, and we discovered a relationship between the durations of its modes and a known underlying radio-modulation time-scale within the modes. We discovered X-ray (energies 0.2-1.4 keV) pulsations with a broad sinusoidal pulse, slightly lagging the radio main pulse in phase by 0.094 ± 0.017, with an energy-dependent pulsed fraction varying from ∼0.15 at 0.3 keV to ∼0.6 at 1 keV. No evidence is found for simultaneous X-ray and radio mode switching. The total X-ray spectrum consists of a cool component (T ∼0.96 × 106 K, hotspot radius R ∼2.0 km) and a hot component (T ∼2.2 × 106 K, R ∼100 m). The hot component can be ascribed to the pulsed emission and the cool component to the unpulsed emission. The high-energy characteristics of PSR B1822-09 resemble those of middle-aged pulsars such as PSR B0656+14, PSR B1055-52 and Geminga, including an indication for pulsed high-energy gamma-ray emission in Fermi Large Area Telescope data. Explanations for the high pulsed fraction seem to require different temperatures at the two poles of this orthogonal rotator, or magnetic anisotropic beaming effects in its strong magnetic field. In our X-ray skymap, we found a harder source at only 5.1 ± 0.5 arcsec from PSR B1822-09, which might be a pulsar wind nebula.

  12. Statistics of interpulse radio pulsars: the key to solving the alignment/counter-alignment problem

    Science.gov (United States)

    Arzamasskiy, L. I.; Beskin, V. S.; Pirov, K. K.

    2017-04-01

    At present, there are theoretical models of radio pulsar evolution that predict both the alignment, i.e. evolution of inclination angle χ between magnetic and rotational axes to 0°, and its counter-alignment, i.e. evolution to 90°. At the same time, both models describe well the pulsar distribution on the P-dot{P} diagram. For this reason, up to now it was impossible to determine the braking mechanisms since it was rather difficult to estimate the evolution of the inclination angle based on observations. In this paper, we demonstrate that the statistics of interpulse pulsars can give us the key to solve the alignment/counter-alignment problem as the number of interpulse pulsars (having both χ ∼ 0° and χ ∼ 90°) drastically depends on the evolution of the inclination angle.

  13. Correlations between pulsed X-ray flux and radio arrival time in the Vela pulsar

    CERN Document Server

    Lommen, A N; Gwinn, C; Arzoumanian, Z; Harding, A; Strickman, M S; Dodson, R; McCulloch, P; Moffett, D

    2007-01-01

    We report the results of simultaneous observations of the Vela pulsar in X-rays and radio from the RXTE satellite and the Mount Pleasant Radio Observatory in Tasmania. We sought correlations between the Vela's X-ray and radio flux densities and radio arrival times on a pulse by pulse basis. We found significantly higher flux density in Vela's main X-ray peak during radio pulses that arrived early. This excess flux shifts to the 'trough' following the 2nd X-ray peak during radio pulses that arrive later. We suggest that the mechanism producing the radio pulses is intimately connected to the mechanism producing X-rays. Current models using resonant absorption in the outer magnetosphere as a cause of the radio emission, and less directly of the X-ray emission, are explored as a possible explanation for the correlation.

  14. The Braking Index of a Radio-quiet Gamma-Ray Pulsar

    Science.gov (United States)

    Clark, C. J.; Pletsch, H. J.; Wu, J.; Guillemot, L.; Camilo, F.; Johnson, T. J.; Kerr, M.; Allen, B.; Aulbert, C.; Beer, C.; Bock, O.; Cuéllar, A.; Eggenstein, H. B.; Fehrmann, H.; Kramer, M.; Machenschalk, B.; Nieder, L.

    2016-11-01

    We report the discovery and timing measurements of PSR J1208-6238, a young and highly magnetized gamma-ray pulsar, with a spin period of 440 ms. The pulsar was discovered in gamma-ray photon data from the Fermi Large Area Telescope (LAT) during a blind-search survey of unidentified LAT sources, running on the distributed volunteer computing system Einstein@Home. No radio pulsations were detected in dedicated follow-up searches with the Parkes radio telescope, with a flux density upper limit at 1369 MHz of 30 μJy. By timing this pulsar’s gamma-ray pulsations, we measure its braking index over five years of LAT observations to be n = 2.598 ± 0.001 ± 0.1, where the first uncertainty is statistical and the second estimates the bias due to timing noise. Assuming its braking index has been similar since birth, the pulsar has an estimated age of around 2700 years, making it the youngest pulsar to be found in a blind search of gamma-ray data and the youngest known radio-quiet gamma-ray pulsar. Despite its young age, the pulsar is not associated with any known supernova remnant or pulsar wind nebula. The pulsar’s inferred dipolar surface magnetic field strength is 3.8 × 1013 G, almost 90% of the quantum-critical level. We investigate some potential physical causes of the braking index deviating from the simple dipole model but find that LAT data covering a longer time interval will be necessary to distinguish between these.

  15. The hunt for new pulsars with the Green Bank Telescope

    CERN Document Server

    Lynch, Ryan S; Banaszak, Shawn; Becker, Alison; Berndsen, Aaron; Biwer, Chris; Boyles, Jason; Cardoso, Rogerio F; Cherry, Angus; Dartez, Louis P; Day, David; Epstein, Courtney R; Flanigan, Joe; Ford, Anthony; Garcia, Alejandro; Hessels, Jason W T; Jenet, Fredrick A; Kaplan, David L; Karako-Argaman, Chen; Kaspi, Victoria M; Kondratiev, Vladislav I; Lorimer, Duncan R; Lunsford, Grady; Martinez, Jose; McLaughlin, Maura A; McPhee, Christie A; Pennucci, Tim; Ransom, Scott M; Roberts, Mallory S E; Rohr, Matt; Siemens, Xavi; Stairs, Ingrid H; Stovall, Kevin; van Leeuwen, Joeri; Walker, Arielle; Wells, Brad

    2013-01-01

    The Green Bank Telescope (GBT) is the largest fully steerable radio telescope in the world and is one of our greatest tools for discovering and studying radio pulsars. Over the last decade, the GBT has successfully found over 100 new pulsars through large-area surveys. Here I discuss the two most recent---the GBT 350 MHz Drift-scan survey and the Green Bank North Celestial Cap survey. The primary science goal of both surveys is to find interesting individual pulsars, including young pulsars, rotating radio transients, exotic binary systems, and especially bright millisecond pulsars (MSPs) suitable for inclusion in Pulsar Timing Arrays, which are trying to directly detect gravitational waves. These two surveys have combined to discover 85 pulsars to date, among which are 14 MSPs and many unique and fascinating systems. I present highlights from these surveys and discuss future plans. I also discuss recent results from targeted GBT pulsar searches of globular clusters and Fermi sources.

  16. Radio Pulsar Death Line Revisited Is PSR J2144-3933 Anomalous?

    CERN Document Server

    Zhang, B; Muslimov, A G; Zhang, Bing; Harding, Alice K.; Muslimov, Alexander G.

    2000-01-01

    We reinvestigate the radio pulsar ``death lines'' within the framework of two different types of polar cap acceleration models, i.e., the vacuum gap model and the space-charge-limited flow model, with either curvature radiation or inverse Compton scattering photons as the source of pairs. General relativistic frame-dragging is taken into account in both models. We find that the inverse Compton scattering induced space-charge-limited flow model can sustain strong pair production in some long-period pulsars, which allows the newly detected 8.5s pulsar PSR J2144-3933 to be radio loud, without assuming a special neutron star equation-of-state or ad hoc magnetic field configurations.

  17. SPAN512: A new mid-latitude pulsar survey with the Nancay Radio Telescope

    CERN Document Server

    Desvignes, Gregory; Champion, David; Lazarus, Patrick; Lespagnol, Patrice; Smith, David A; Theureau, Gilles

    2012-01-01

    We present an ongoing survey with the Nan\\c{c}ay Radio Telescope at L-band. The targeted area is $74^\\circ \\lesssim l <150^\\circ$ and $3.5^\\circ < |b| < 5^\\circ$. This survey is characterized by a long integration time (18 min), large bandwidth (512 MHz) and high time and frequency resolution (64 $\\mu$s and 0.5 MHz) giving a nominal sensitivity limit of 0.055 mJy for long period pulsars. This is about 2 times better than the mid-latitude HTRU survey, and is designed to be complementary with current large scale surveys. This survey will be more sensitive to transients (RRATs, intermittent pulsars), distant and faint millisecond pulsars as well as scintillating sources (or any other kind of radio faint sources) than all previous short-integration surveys.

  18. Detection of decametre-wavelength pulsed radio emission of 40 known pulsars

    Science.gov (United States)

    Zakharenko, V. V.; Vasylieva, I. Y.; Konovalenko, A. A.; Ulyanov, O. M.; Serylak, M.; Zarka, P.; Grießmeier, J.-M.; Cognard, I.; Nikolaenko, V. S.

    2013-06-01

    The study of pulsars at the lowest radio frequencies observable from the ground (10-30 MHz) is complicated by strong interstellar (dispersion, scattering) and ionospheric (scintillation, refraction) propagation effects, as well as intense Galactic background noise and interference. However, it permits us to measure interstellar plasma parameters (the effects of which increase by a power of two to >4 times the wavelength), the spectrum and the pulse profile at low frequencies more accurately. Up to now, only ˜10 pulsars have been successfully detected at these frequencies. The recent upgrade of the receivers at the Ukrainian T-shaped Radio telescope, second modification (UTR-2) has increased its sensitivity and motivated a new search for pulsed radio emissions. In this work we carried out a survey of known pulsars with declination above -10°, period >0.1 s and dispersion measure (DM) < 30 pc cm-3, i.e. a sample of 74 sources. Our goal was either to detect pulsars not recorded before in the decametre range or to identify factors that prevent their detection. As a result, we have detected the radio emission of 40 pulsars, i.e. 55 per cent of the observed sample. For 30 of them, this was a first detection at these frequencies. Parameters of their average profiles have been calculated, including the intrinsic widening of the pulse (not due to interstellar scattering) with decreasing frequency. Furthermore, two pulsars beyond the selected DM (B0138+59 with DM ≈ 35 pc cm-3 and B0525+21 with DM ≈51 pc cm-3) were also detected. Our results indicate that there is still room to detect new transient and pulsed sources with low-frequency observations.

  19. Constraints on Individual Supermassive Black Hole Binaries from Pulsar Timing Array Limits on Continuous Gravitational Waves

    CERN Document Server

    Schutz, Katelin

    2015-01-01

    Pulsar timing arrays (PTAs) are placing increasingly stringent constraints on the strain amplitude of continuous gravitational waves emitted by supermassive black hole binaries on subparsec scales. In this paper, we incorporate independent measurements of the dynamical masses $M_{\\rm bh}$ of supermassive black holes in specific galaxies at known distances and leverage this additional information to further constrain whether or not those galaxies could host a detectable supermassive black hole binary. We estimate the strain amplitudes from individual binaries as a function of binary mass ratio for two samples of nearby galaxies: (1) those with direct dynamical measurements of $M_{\\rm bh}$ in the literature, and (2) the 116 most massive early-type galaxies (and thus likely hosts of the most massive black holes) within 108 Mpc from the MASSIVE Survey. Our exploratory analysis shows that the current PTA upper limits on continuous waves can already constrain the mass ratios of hypothetical black hole binaries in a...

  20. Synchronous X-ray and radio mode switches: a rapid global transformation of the pulsar magnetosphere

    NARCIS (Netherlands)

    Hermsen, W.; Hessels, J.W.; Kuiper, L.; Leeuwen, van J.; Mitra, D.; Plaa, de J.; Rankin, J.M.; Stappers, B.W.; Wright, G.A.E.; Basu, R.; Alexov, A.; Coenen, T.; Griessmeier, J.M.; Hassall, T.E.; Karastergiou, A.; Keane, E.; Kondratiev, V.I.; Kramer, M.; Kuniyoshi, M.; Noutsos, A.; Serylak, M.; Pilia, M.; Sobey, C.; Weltevrede, P.; Zagkouris, K.; Asgekar, A.; Avruch, I.M.; Batejat, F.; Bell, M.E.; Bell, M.R.; Bentum, M.J.; Bernardi, G.; Best, P.; Birzan, L.; Bonfede, A.; Breitling, F.; Broderick, J.; Brüggen, M.; Butcher, H.R.; Ciardi, B.; Duscha, S.; Eislöffel, J.; Falcke, H.; Fender, R.; Ferrari, C.; Frieswijk, W.; Garrett, M.A.; Gasperin, de F.; Geus, de E.; Gunst, A.W.; Heald, G.; Hoeft, M.; Homeffer, A.; Iabobelli, M.; Kuper, G.; Maat, P.; Macario, G.; Markoff, S.; McKean, J.P.; Mevius, M.; Miller-Jones, J.C.A.; Morganti, R.; Munk, H.; Orrú, E.; Paas, H.; Pandey-Pommier, M.; Pandey, V.N.; Pizzo, R.; Polatidis, A.G.; Rawlings, S.; Reich, W.; Röttgering, H.; Scaife, A.M.M.; Schoenmakers, A.; Shulevski, A.; Sluman, J.; Steinmetz, M.; Tagger, M.; Tang, Y.; Tasse, C.; Veen, ter S.; Vermeulen, R.; Brink, van de R.H.; Weeren, van R.J.; Weijers, R.A.M.J.; Wise, M.W.; Wucknitz, O.; Yatawatta, S.; Zarka, P.

    2013-01-01

    Pulsars emit from low-frequency radio waves up to high-energy gamma-rays, generated anywhere from the stellar surface out to the edge of the magnetosphere. Detecting correlated mode changes across the electromagnetic spectrum is therefore key to understanding the physical relationship among the emis

  1. A study of the evolution of radio pulsars through improved population synthesis

    NARCIS (Netherlands)

    Hartman, J.W.; Bhattacharya, D.; Wijers, R.A.M.J.; Verbunt, F.

    1997-01-01

    We simulate the birth and evolution of radio pulsars throughout the Galaxy and their observation in a region around the Sun, using recently derived models for the velocity distribution of neutron stars and for the galactic distribution of free electrons. We confirm our previous result that the prope

  2. Radio upper limits for the accreting millisecond X-ray pulsar IGR J17511-3057

    NARCIS (Netherlands)

    Miller-Jones, J.C.A.; Russell, D.M.; Migliari, S.

    2009-01-01

    We report on recent radio observations of the newly-detected accreting millisecond X-ray pulsar, IGR J17511-3057 (ATels #2196, #2197, #2198, #2199, #2215, #2216, #2220, #2221). We used the Very Large Array (VLA) to observe the source under observing program AM971. The array was in its relatively com

  3. EINSTEIN-HOME DISCOVERY OF 24 PULSARS IN THE PARKES MULTI-BEAM PULSAR SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Knispel, B.; Kim, H.; Allen, B.; Aulbert, C.; Bock, O.; Eggenstein, H.-B.; Fehrmann, H.; Machenschalk, B. [Albert-Einstein-Institut, Max-Planck-Institut fuer Gravitationsphysik, D-30167 Hannover (Germany); Eatough, R. P.; Keane, E. F.; Kramer, M. [Max-Planck-Institut fuer Radioastronomie, D-53121 Bonn (Germany); Anderson, D. [University of California at Berkeley, Berkeley, CA 94720 (United States); Crawford, F.; Rastawicki, D. [Department of Physics and Astronomy, Franklin and Marshall College, P.O. Box 3003, Lancaster, PA 17604 (United States); Hammer, D.; Papa, M. A.; Siemens, X. [Physics Department, University of Wisconsin-Milwaukee, Milwaukee, WI 53211 (United States); Lyne, A. G. [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Miller, R. B. [Department of Physics, West Virginia University, 111 White Hall, Morgantown, WV 26506 (United States); Sarkissian, J., E-mail: benjamin.knispel@aei.mpg.de [CSIRO Parkes Observatory, Parkes, NSW 2870 (Australia); and others

    2013-09-10

    We have conducted a new search for radio pulsars in compact binary systems in the Parkes multi-beam pulsar survey (PMPS) data, employing novel methods to remove the Doppler modulation from binary motion. This has yielded unparalleled sensitivity to pulsars in compact binaries. The required computation time of Almost-Equal-To 17, 000 CPU core years was provided by the distributed volunteer computing project Einstein-Home, which has a sustained computing power of about 1 PFlop s{sup -1}. We discovered 24 new pulsars in our search, 18 of which were isolated pulsars, and 6 were members of binary systems. Despite the wide filterbank channels and relatively slow sampling time of the PMPS data, we found pulsars with very large ratios of dispersion measure (DM) to spin period. Among those is PSR J1748-3009, the millisecond pulsar with the highest known DM ( Almost-Equal-To 420 pc cm{sup -3}). We also discovered PSR J1840-0643, which is in a binary system with an orbital period of 937 days, the fourth largest known. The new pulsar J1750-2536 likely belongs to the rare class of intermediate-mass binary pulsars. Three of the isolated pulsars show long-term nulling or intermittency in their emission, further increasing this growing family. Our discoveries demonstrate the value of distributed volunteer computing for data-driven astronomy and the importance of applying new analysis methods to extensively searched data.

  4. Einstein@Home Discovery of 24 Pulsars in the Parkes Multi-beam Pulsar Survey

    Science.gov (United States)

    Knispel, B.; Eatough, R. P.; Kim, H.; Keane, E. F.; Allen, B.; Anderson, D.; Aulbert, C.; Bock, O.; Crawford, F.; Eggenstein, H.-B.; Fehrmann, H.; Hammer, D.; Kramer, M.; Lyne, A. G.; Machenschalk, B.; Miller, R. B.; Papa, M. A.; Rastawicki, D.; Sarkissian, J.; Siemens, X.; Stappers, B. W.

    2013-09-01

    We have conducted a new search for radio pulsars in compact binary systems in the Parkes multi-beam pulsar survey (PMPS) data, employing novel methods to remove the Doppler modulation from binary motion. This has yielded unparalleled sensitivity to pulsars in compact binaries. The required computation time of ≈17, 000 CPU core years was provided by the distributed volunteer computing project Einstein@Home, which has a sustained computing power of about 1 PFlop s-1. We discovered 24 new pulsars in our search, 18 of which were isolated pulsars, and 6 were members of binary systems. Despite the wide filterbank channels and relatively slow sampling time of the PMPS data, we found pulsars with very large ratios of dispersion measure (DM) to spin period. Among those is PSR J1748-3009, the millisecond pulsar with the highest known DM (≈420 pc cm-3). We also discovered PSR J1840-0643, which is in a binary system with an orbital period of 937 days, the fourth largest known. The new pulsar J1750-2536 likely belongs to the rare class of intermediate-mass binary pulsars. Three of the isolated pulsars show long-term nulling or intermittency in their emission, further increasing this growing family. Our discoveries demonstrate the value of distributed volunteer computing for data-driven astronomy and the importance of applying new analysis methods to extensively searched data.

  5. Correlation between X-ray Lightcurve Shape and Radio Arrival Time in the Vela Pulsar

    CERN Document Server

    Lommen, A; Gwinn, C; Arzoumanian, Z; Harding, A; Strickman, M S; Dodson, R; McCulloch, P; Moffett, D

    2006-01-01

    We report the results of simultaneous observations of the Vela pulsar in X-rays and radio from the RXTE satellite and the Mount Pleasant Radio Observatory in Tasmania. We sought correlations between the Vela's X-ray emission and radio arrival times on a pulse by pulse basis. At a confidence level of 99.8% we have found significantly higher flux density in Vela's main X-ray peak during radio pulses that arrived early. This excess flux shifts to the 'trough' following the 2nd X-ray peak during radio pulses that arrive later. Our results suggest that the mechanism producing the radio pulses is intimately connected to the mechanism producing X-rays. Current models using resonant absorption of radio emission in the outer magnetosphere as a cause of the X-ray emission are explored as a possible explanation for the correlation.

  6. Properties and Evolution of the Redback Millisecond Pulsar Binary PSR J2129-0429

    CERN Document Server

    Bellm, Eric C; Breton, Rene P; Phinney, E Sterl; Bhalerao, Varun B; Camilo, Fernando; Dahal, Sumit; Djorgovski, S G; Drake, Andrew J; Hessels, J W T; Laher, Russ R; Levitan, David B; Lewis, Fraser; Mahabal, Ashish A; Ofek, Eran O; Prince, Thomas A; Ransom, Scott M; Roberts, Mallory S E; Russell, David M; Sesar, Branimir; Surace, Jason A; Tang, Sumin

    2015-01-01

    PSR J2129-0429 is a "redback" eclipsing millisecond pulsar binary with an unusually long 15.2 hour orbit. It was discovered by the Green Bank Telescope in a targeted search of unidentified Fermi gamma-ray sources. The pulsar companion is optically bright (mean $m_R = 16.6$ mag), allowing us to construct the longest baseline photometric dataset available for such a system. We present ten years of archival and new photometry of the companion from LINEAR, CRTS, PTF, the Palomar 60-inch, and LCOGT. Radial velocity spectroscopy using the Double-Beam Spectrograph on the Palomar 200-inch indicates that the pulsar is massive: $1.74\\pm0.18 M_\\odot$. The G-type pulsar companion has mass $0.44\\pm0.04 M_\\odot$, one of the heaviest known redback companions. It is currently 95\\% Roche-lobe filling and only mildly irradiated by the pulsar. We identify a clear 13.1 mmag yr$^{-1}$ secular decline in the mean magnitude of the companion as well as smaller-scale variations in the optical lightcurve shape. This behavior may indic...

  7. On the pulse-width statistics in radio pulsars. III. Importance of the conal profile components

    CERN Document Server

    Maciesiak, K; Melikidze, G

    2012-01-01

    This work is a continuation of two previous papers of a series, in which we examined the pulse-width statistics of normal radio pulsars. In the first paper we compiled the largest ever database of pulsars with interpulses in their mean profiles. In the second one we confirmed the existence of the lower boundary in the scatter plot of core component pulse-widths versus pulsar period W50 sim 2.5 P^{-0.5}[deg], first discovered by Rankin using much smaller number of interpulse cases. In this paper we show that the same lower boundary also exists for conal profile components. Rankin proposed a very simple method of estimation of pulsar inclination angle based on comparing the width W50 of its core component with the period dependent value of the lower boundary. We claim that this method can be extended to conal components as well. To explain an existence of the lower boundary Rankin proposed that the core emission originates at or near the polar cap surface. We demonstrated clearly that no coherent pulsar radio e...

  8. NuSTAR Observations of the State Transition of Millisecond Pulsar Binary PSR J1023+0038

    CERN Document Server

    Tendulkar, Shriharsh P; An, Hongjun; Kaspi, Victoria M; Archibald, Anne M; Bassa, Cees; Bellm, Eric; Bogdanov, Slavko; Harrison, Fiona A; Hessels, Jason W T; Janssen, Gemma H; Lyne, Andrew G; Patruno, Alessandro; Stappers, Benjamin; Stern, Daniel; Tomsick, John A; Boggs, Steven E; Chakrabarty, Deepto; Christensen, Finn E; Craig, William W; Hailey, Charles A; Zhang, William

    2014-01-01

    We report NuSTAR observations of the millisecond pulsar - low mass X-ray binary (LMXB) transition system PSR J1023+0038 from June and October 2013, before and after the formation of an accretion disk around the neutron star. Between June 10-12, a few days to two weeks before the radio disappearance of the pulsar, the 3-79 keV X-ray spectrum was well fit by a simple power law with a photon index of Gamma=1.17 +/-0.08 (at 90% confidence) with a 3-79 keV luminosity of 7.4+/-0.4 x 10^32 erg/s. Significant orbital modulation was observed with a modulation fraction of 36+/-10%. During the October 19-21 observation, the spectrum is described by a softer power law (Gamma=1.66+/-0.06) with an average luminosity of 5.8+/-0.2 x 10^33 erg/s and a peak luminosity of ~1.2 x 10^34 erg/s observed during a flare. No significant orbital modulation was detected. The spectral observations are consistent with previous and current multi-wavelength observations and show the hard X-ray power law extending to 79 keV without a spectra...

  9. Search for differences between radio-loud and radio-quiet gamma-ray pulsar populations with Fermi-LAT data

    CERN Document Server

    Sokolova, E V

    2016-01-01

    Observations by Fermi LAT enabled us to explore the population of non-recycled gamma-ray pulsars with the set of 89 objects. It was recently noted that there are apparent differences in properties of radio-quiet and radio-loud subsets. In particular, average observed radio-loud pulsar is younger than radio-quiet one and is located at smaller galactic latitude. Even so, the analysis based on the full list of pulsars may suffer from selection effects. Namely, most of radio-loud pulsars are first discovered in the radio-band, while radio-quiet ones are found using the gamma-ray data. In this work we perform a blind search for gamma-ray pulsars using the Fermi LAT data alone using all point sources from 3FGL catalog as the candidates. Unlike preceding blind search, the present catalog is constructed with novel semi-coherent method and covers the full range of characteristic ages down to 1 kyr. The search resulted in the catalog of 40 non-recycled pulsars, 26 of which are radio-quiet. There are no statistically si...

  10. On 'An exact solution of Haugan's binary pulsar equation of motion'

    Science.gov (United States)

    Haugan, Mark P.

    1988-10-01

    The analysis of the equation for the relative orbit of a post-Newtonian two-body system published recently by Weinstein and Mor (45.066.104) does not properly incorporate the Newtonian limit. As a result, the solution they derive is of no use for dealing with the motion of the binary pulsar. The claim that the form of their solution implies that earlier treatments of post-Newtonian orbital motion have missed significant effects is mistaken.

  11. EVOLUTION OF TRANSIENT LOW-MASS X-RAY BINARIES TO REDBACK MILLISECOND PULSARS

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Kun; Li, Xiang-Dong, E-mail: lixd@nju.edu.cn [Department of Astronomy, Nanjing University, Nanjing 210046 (China)

    2015-11-20

    Redback millisecond pulsars (MSPs; hereafter redbacks) are a subpopulation of eclipsing MSPs in close binaries. The formation processes of these systems are not clear. The three pulsars showing transitions between rotation- and accretion-powered states belong to both redbacks and transient low-mass X-ray binaries (LMXBs), suggesting a possible evolutionary link between them. Through binary evolution calculations, we show that the accretion disks in almost all LMXBs are subject to the thermal-viscous instability during certain evolutionary stages, and the parameter space for the disk instability covers the distribution of known redbacks in the orbital period—companion mass plane. We accordingly suggest that the abrupt reduction of the mass accretion rate during quiescence of transient LMXBs provides a plausible way to switch on the pulsar activity, leading to the formation of redbacks, if the neutron star has been spun up to be an energetic MSP. We investigate the evolution of redbacks, taking into account the evaporation feedback, and discuss its possible influence on the formation of black widow MSPs.

  12. Radio Detection of the Fermi-LAT Blind Search Millisecond Pulsar J1311-3430

    Science.gov (United States)

    Ray, P. S.; Ransom, S. M.; Cheung, C. C.; Giroletti, M.; Cognard, I.; Camilo, F.; Bhattacharyya, B.; Roy, J.; Romani, R. W.; Ferrara, E. C.; Guillemot, L.; Johnston, S.; Keith, M.; Kerr, M.; Kramer, M.; Pletsch, H. J.; Parkinson, P. M. Saz

    2013-01-01

    We report the detection of radio emission from PSR J1311.3430, the first millisecond pulsar (MSP) discovered in a blind search of Fermi Large Area Telescope (LAT) gamma-ray data. We detected radio pulsations at 2 GHz, visible for less than 10% of approximately 4.5 hr of observations using the Green Bank Telescope (GBT). Observations at 5 GHz with the GBT and at several lower frequencies with Parkes, Nan cay, and the Giant Metrewave Radio Telescope resulted in non-detections. We also report the faint detection of a steep spectrum continuum radio source (0.1 mJy at 5 GHz) in interferometric imaging observations with the Jansky Very Large Array. These detections demonstrate that PSR J1311.3430 is not radio quiet and provide additional evidence that radio-quiet MSPs are rare. The radio dispersion measure of 37.8 pc cm(exp -3) provides a distance estimate of 1.4 kpc for the system, yielding a gamma-ray efficiency of 30%, typical of LAT-detected MSPs. We see apparent excess delay in the radio pulses as the pulsar appears from eclipse and we speculate on possible mechanisms for the non-detections of the pulse at other orbital phases and observing frequencies.

  13. RADIO DETECTION OF THE FERMI-LAT BLIND SEARCH MILLISECOND PULSAR J1311-3430

    Energy Technology Data Exchange (ETDEWEB)

    Ray, P. S.; Wood, K. S. [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States); Ransom, S. M. [National Radio Astronomy Observatory (NRAO), Charlottesville, VA 22903 (United States); Cheung, C. C. [National Academy of Sciences, Washington, DC 20001 (United States); Giroletti, M. [INAF Istituto di Radioastronomia, I-40129 Bologna (Italy); Cognard, I. [Laboratoire de Physique et Chimie de l' Environnement, LPCE UMR 6115 CNRS, F-45071 Orleans Cedex 02 (France); Camilo, F. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Bhattacharyya, B. [Inter-University Centre for Astronomy and Astrophysics, Pune 411 007 (India); Roy, J. [National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune 411 007 (India); Romani, R. W.; Kerr, M. [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); Ferrara, E. C. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Guillemot, L.; Kramer, M. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany); Johnston, S.; Keith, M. [CSIRO Astronomy and Space Science, Australia Telescope National Facility, Epping NSW 1710 (Australia); Pletsch, H. J. [Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, D-30167 Hannover (Germany); Saz Parkinson, P. M., E-mail: Paul.Ray@nrl.navy.mil [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)

    2013-01-20

    We report the detection of radio emission from PSR J1311-3430, the first millisecond pulsar (MSP) discovered in a blind search of Fermi Large Area Telescope (LAT) gamma-ray data. We detected radio pulsations at 2 GHz, visible for <10% of {approx}4.5 hr of observations using the Green Bank Telescope (GBT). Observations at 5 GHz with the GBT and at several lower frequencies with Parkes, Nancay, and the Giant Metrewave Radio Telescope resulted in non-detections. We also report the faint detection of a steep spectrum continuum radio source (0.1 mJy at 5 GHz) in interferometric imaging observations with the Jansky Very Large Array. These detections demonstrate that PSR J1311-3430 is not radio quiet and provide additional evidence that radio-quiet MSPs are rare. The radio dispersion measure of 37.8 pc cm{sup -3} provides a distance estimate of 1.4 kpc for the system, yielding a gamma-ray efficiency of 30%, typical of LAT-detected MSPs. We see apparent excess delay in the radio pulses as the pulsar appears from eclipse and we speculate on possible mechanisms for the non-detections of the pulse at other orbital phases and observing frequencies.

  14. Discovery of Low DM Fast Radio Transients: Geminga Pulsar Caught in the Act

    CERN Document Server

    Maan, Yogesh

    2015-01-01

    We report discovery of several energetic radio bursts at 34 MHz, using the Gauribidanur radio telescope. The radio bursts exhibit two important properties associated with the propagation of astronomical signals through the interstellar medium: (i) frequency dependent dispersive delays across the observing bandwidth, and (ii) Faraday rotation of the plane of linear polarization. These bursts sample a range of dispersion measures (DM; 1.4--3.6$~{\\rm pc}~{\\rm cm}^{-3}$), and show DM-variation at timescales of the order of a minute. Using groups of bursts having a consistent DM, we show that the bursts have originated from the radio-quiet gamma-ray pulsar Geminga. Detection of these bursts supports the existence of occasional radio emission from Geminga. The rare occurrence of these bursts, and the short timescale variation in their DM (if really caused by the intervening medium or the pulsar magnetosphere), might provide clues as to why the pulsar has not been detected in earlier sensitive searches. We present d...

  15. Interpretation of the Low-Frequency Peculiarities in the Radio Profile Structure of the Crab Pulsar

    CERN Document Server

    Petrova, S A

    2008-01-01

    The theory of magnetized induced scattering off relativistic gyrating particles is developed. It is directly applicable to the magnetosphere of a pulsar, in which case the particles acquire gyration energies as a result of resonant absorption of radio emission. In the course of the radio beam scattering into background the scattered radiation concentrates along the ambient magnetic field. The scattering from different harmonics of the particle gyrofrequency takes place at different characteristic altitudes in the magnetosphere and, because of the rotational effect, gives rise to different components in the pulse profile. It is demonstrated that the induced scattering from the first harmonic into the state under the resonance can account for the so-called low-frequency component in the radio profile of the Crab pulsar. The precursor component is believed to result from the induced scattering between the two states well below the resonance. It is shown that these ideas are strongly supported by the polarization...

  16. Optical polarisation of the Crab pulsar: precision measurements and comparison to the radio emission

    CERN Document Server

    Słowikowska, Agnieszka; Kramer, Michael; Stefanescu, Alexander

    2009-01-01

    The linear polarisation of the Crab pulsar and its close environment was derived from observations with the high-speed photo-polarimeter OPTIMA at the 2.56-m Nordic Optical Telescope in the optical spectral range (400 - 750 nm). Time resolution as short as 11 microseconds, which corresponds to a phase interval of 1/3000 of the pulsar rotation, and high statistics allow the derivation of polarisation details never achieved before. The degree of optical polarisation and the position angle correlate in surprising details with the light curves at optical wavelengths and at radio frequencies of 610 and 1400 MHz. Our observations show that there exists a subtle connection between presumed non-coherent (optical) and coherent (radio) emissions. This finding supports previously detected correlations between the optical intensity of the Crab and the occurrence of giant radio pulses. Interpretation of our observations require more elaborate theoretical models than those currently available in the literature.

  17. A Magnetar-like Outburst from a High-B Radio Pulsar

    CERN Document Server

    Archibald, R F; Tendulkar, S P; Scholz, P

    2016-01-01

    Radio pulsars are believed to have their emission powered by the loss of rotational kinetic energy. By contrast, magnetars show intense X-ray and gamma-ray radiation whose luminosity greatly exceeds that due to spin-down and is believed to be powered by intense internal magnetic fields. A basic prediction of this picture is that radio pulsars of high magnetic field should show magnetar-like emission. Here we report on a magnetar-like X-ray outburst from the radio pulsar PSR J1119-6127, heralded by two short bright X-ray bursts on 2016 July 27 and 28 (Kennea et al. 2016; Younes et al. 2016). Using Target-of-Opportunity data from the Swift X-ray Telescope and NuSTAR, we show that this pulsar's flux has brightened by a factor of > 160 in the 0.5-10 keV band, and its previously soft X-ray spectrum has undergone a strong hardening, with strong pulsations appearing for the first time above 2.5 keV, with phase-averaged emission detectable up to 25 keV. By comparing Swift-XRT and NuSTAR timing data with a pre-outburs...

  18. Search for the Giant Pulses Search for the Giant Pulses - an extreme phenomenon in radio pulsar emission

    CERN Document Server

    Kazantsev, A N

    2016-01-01

    Here we present results of our search for Giant Pulses(GPs) from pulsars of Northern Hemisphere. Our survey was carried out at a frequency of 111 MHz using the Large Phased Array (LPA) radio telescope. Up to now we have detected regular generation of strong pulses satisfying the criteria of GPs from 2 pulsars: B1133+16, B1237+25.

  19. Phase offsets between core and conal components of radio pulsars and their emission altitudes

    CERN Document Server

    Kapoor, R C

    2002-01-01

    We present a new method for investigating emission altitudes of radio pulsar core and conal components by attributing them different altitudes and by providing a framework to understand the resulting longitude offsets between them which are frequently observed. By investigating the contributions to these offsets due to aberration and the magnetic field line sweepback, we show that they are always dominated by aberration for all emission altitudes and inclination angles. This directly allows the conclusion that the core emission does not necessarily come from the surface. Our results and the observational trends imply that for a large number of pulsars the emission altitudes of core and conal components are close when compared to the light cylinder radius but not necessarily relative to the stellar radius. The core/cone altitude differences that we find are typically larger than the individual altitudes ascribed to them so far. Widely different core/cone altitudes for some pulsars are also supported by data an...

  20. The PALFA Survey: Going to great depths to find radio pulsars

    CERN Document Server

    Lazarus, P; Bhat, N D R; Bogdanov, S; Bouchard, A; Brazier, A; Camilo, F; Cardoso, F; Chatterjee, S; Cordes, J M; Crawford, F; Deneva, J S; Desvignes, G; Freire, P C C; Hessels, J W T; Jenet, F A; Kaspi, V M; Knispel, B; van Leeuwen, J; Lorimer, D R; Lynch, R; Lyne, A G; McLaughlin, M A; Nice, D J; Ransom, S M; Scholz, P; Siemens, X; Stairs, I H; Stappers, B W; Stovall, K; Swiggum, J

    2012-01-01

    The on-going PALFA survey is searching the Galactic plane (|b| < 5 deg., 32 < l < 77 deg. and 168 < l < 214 deg.) for radio pulsars at 1.4 GHz using ALFA, the 7-beam receiver installed at the Arecibo Observatory. By the end of August 2012, the PALFA survey has discovered 100 pulsars, including 17 millisecond pulsars (P < 30 ms). Many of these discoveries are among the pulsars with the largest DM/P ratios, proving that the PALFA survey is capable of probing the Galactic plane for millisecond pulsars to a much greater depth than any previous survey. This is due to the survey's high sensitivity, relatively high observing frequency, and its high time and frequency resolution. Recently the rate of discoveries has increased, due to a new more sensitive spectrometer, two updated complementary search pipelines, the development of online collaborative tools, and access to new computing resources. Looking forward, focus has shifted to the application of artificial intelligence systems to identify puls...

  1. Very Long Baseline Interferometry Experiment on Giant Radio Pulses of Crab Pulsar toward Fast Radio Burst Detection

    CERN Document Server

    Takefuji, K; Kondo, T; Mikami, R; Takeuchi, H; Misawa, H; Tsuchiya, F; Kita, H; Sekido, M

    2016-01-01

    We report on a very long baseline interferometry (VLBI) experiment on giant radio pulses (GPs) from the Crab pulsar in the radio 1.4 to 1.7 GHz range to demonstrate a VLBI technique for searching for fast radio bursts (FRBs). We carried out the experiment on 26 July 2014 using the Kashima 34 m and Usuda 64 m radio telescopes of the Japanese VLBI Network (JVN) with a baseline of about 200 km. During the approximately 1 h observation, we could detect 35 GPs by high-time-resolution VLBI. Moreover, we determined the dispersion measure (DM) to be 56.7585 +/- 0.0025 on the basis of the mean DM of the 35 GPs detected by VLBI. We confirmed that the sensitivity of a detection of GPs using our technique is superior to that of a single-dish mode detection using the same telescope.

  2. Simulations of an inhomogeneous stellar wind interacting with a pulsar wind in a binary system

    CERN Document Server

    Paredes-Fortuny, Xavier; Perucho, Manel; Ribó, Marc

    2014-01-01

    Binary systems containing a massive star and a non-accreting pulsar present strong interaction between the stellar and the pulsar winds. The properties of this interaction, which largely determine the non-thermal radiation in these systems, strongly depend on the structure of the stellar wind, which can be clumpy or strongly anisotropic, as in Be stars. We study numerically the influence of inhomogeneities in the stellar wind on the structure of the two-wind interaction region. We carried out for the first time axisymmetric, relativistic hydrodynamical simulations, with Lorentz factors of ~6 and accounting for the impact of instabilities, to study the impact in the two-wind interaction structure of an over-dense region of the stellar wind. We also followed the evolution of this over-dense region or clump as it faces the impact of the pulsar wind. For typical system parameters, and adopting a stellar wind inhomogeneity with a density contrast >~10, clumps with radii of a few percent of the binary size can sign...

  3. Possible optical detection of a fast, nearby radio pulsar PSR B1133+16

    CERN Document Server

    Zharikov, S V; Mennickent, R E; Komarova, V N

    2007-01-01

    Aims: We performed deep optical observations of the field of an old, fast-moving radio pulsar PSR B1133+16 in an attempt to detect its optical counterpart and a bow shock nebula. Methods: The observations were carried out using the direct imaging mode of FORS1 at the ESO VLT/UT1 telescope in the B, R, and H_alpha bands. We also used archival images of the same field obtained with the VLT in the B band and with the Chandra/ACIS in X-rays. Results: In the B band we detected a faint (B=28.1+/-0.3) source that may be the optical counterpart of PSR B1133+16, as it is positionally consistent with the radio pulsar and with the X-ray counterpart candidate published earlier. Its upper limit in the R band implies a color index B-R <0.5, which is compatible with the index values for most pulsars identified in the optical range. The derived optical luminosity and its ratio to the X-ray luminosity of the candidate are consistent with expected values derived from a sample of pulsars detected in both spectral domains. No...

  4. Wide-Band, Low-Frequency Pulse Profiles of 100 Radio Pulsars with LOFAR

    CERN Document Server

    Pilia, M; Stappers, B W; Kondratiev, V I; Kramer, M; van Leeuwen, J; Weltevrede, P; Lyne, A G; Zagkouris, K; Hassall, T E; Bilous, A V; Breton, R P; Falcke, H; Grießmeier, J -M; Keane, E; Karastergiou, A; Kuniyoshi, M; Noutsos, A; Osłowski, S; Serylak, M; Sobey, C; ter Veen, S; Alexov, A; Anderson, J; Asgekar, A; Avruch, I M; Bell, M E; Bentum, M J; Bernardi, G; Bîrzan, L; Bonafede, A; Breitling, F; Broderick, J W; Brüggen, M; Ciardi, B; Corbel, S; de Geus, E; de Jong, A; Deller, A; Duscha, S; Eislöffel, J; Fallows, R A; Fender, R; Ferrari, C; Frieswijk, W; Garrett, M A; Gunst, A W; Hamaker, J P; Heald, G; Horneffer, A; Jonker, P; Juette, E; Kuper, G; Maat, P; Mann, G; Markoff, S; McFadden, R; McKay-Bukowski, D; Miller-Jones, J C A; Nelles, A; Paas, H; Pandey-Pommier, M; Pietka, M; Pizzo, R; Polatidis, A G; Reich, W; Röttgering, H; Rowlinson, A; Schwarz, D; Smirnov, O; Steinmetz, M; Stewart, A; Swinbank, J D; Tagger, M; Tang, Y; Tasse, C; Thoudam, S; Toribio, M C; van der Horst, A J; Vermeulen, R; Vocks, C; van Weeren, R J; Wijers, R A M J; Wijnands, R; Wijnholds, S J; Wucknitz, O; Zarka, P

    2015-01-01

    LOFAR offers the unique capability of observing pulsars across the 10-240 MHz frequency range with a fractional bandwidth of roughly 50%. This spectral range is well-suited for studying the frequency evolution of pulse profile morphology caused by both intrinsic and extrinsic effects: such as changing emission altitude in the pulsar magnetosphere or scatter broadening by the interstellar medium, respectively. The magnitude of most of these effects increases rapidly towards low frequencies. LOFAR can thus address a number of open questions about the nature of radio pulsar emission and its propagation through the interstellar medium. We present the average pulse profiles of 100 pulsars observed in the two LOFAR frequency bands: High Band (120-167 MHz, 100 profiles) and Low Band (15-62 MHz, 26 profiles). We compare them with Westerbork Synthesis Radio Telescope (WSRT) and Lovell Telescope observations at higher frequencies (350 and1400 MHz) in order to study the profile evolution. The profiles are aligned in abs...

  5. New limits on the photon mass with radio pulsars in the Magellanic clouds

    Science.gov (United States)

    Wei, Jun-Jie; Zhang, Er-Kang; Zhang, Song-Bo; Wu, Xue-Feng

    2017-02-01

    A conservative constraint on the rest mass of the photon can be estimated under the assumption that the frequency dependence of dispersion from astronomical sources is mainly contributed by the nonzero photon mass effect. Photon mass limits have been set earlier through the optical emissions of the Crab Nebula pulsar, but we demonstrate that these limits can be significantly improved with the dispersion measure (DM) measurements of radio pulsars in the Large and Small Magellanic Clouds. The combination of DM measurements of pulsars and distances of the Magellanic Clouds provides a strict upper limit on the photon mass as low as mγ ≤2.0×10-45{ }{g}, which is at least four orders of magnitude smaller than the constraint from the Crab Nebula pulsar. Although our limit is not as tight as the current best result (∼10-47{ }{g}) from a fast radio burst (FRB 150418) at a cosmological distance, the cosmological origin of FRB 150418 remains under debate; and our limit can reach the same high precision of FRB 150418 when it has an extragalactic origin (∼10-45{ }{g}).

  6. New Limits on the Photon Mass with Radio Pulsars in the Magellanic Clouds

    CERN Document Server

    Wei, Jun-Jie; Zhang, Song-Bo; Wu, Xue-Feng

    2016-01-01

    A conservative constraint on the rest mass of the photon can be estimated under the assumption that the frequency dependence of dispersion from astronomical sources is mainly contributed by the nonzero photon mass effect. Photon mass limits have been earlier set through the optical emissions of the Crab Nebula pulsar, but we prove that these limits can be significantly improved with the dispersion measure (DM) measurements of radio pulsars in the Large and Small Magellanic Clouds. The combination of DM measurements of pulsars and distances of the Magellanic Clouds provide a strict upper limit on the photon mass as low as $m_{\\gamma} \\leq2.0\\times10^{-45}~\\rm{g}$, which is at least four orders of magnitude smaller than the constraint from the Crab Nebula pulsar. Although our limit is not as tight as the current best result ($\\sim10^{-47}~\\rm{g}$) from a fast radio burst (FRB 150418) at a cosmological distance, the cosmological origin of FRB 150418 remains under debate; and our limit can reach the same high pre...

  7. High Frequency Cut-off and Changing of Radio Emission Mechanism in Pulsars

    CERN Document Server

    Kontorovich, V M

    2012-01-01

    Pulsars are the fast rotating neutron stars with strong magnetic field emitting over a wide frequency range. In spite of the efforts during 40 years after the discovery of pulsars, the mechanism of their radio emission remains to be unknown so far. We propose a new approach to solving this problem. The object of our study is a sample of pulsars with a high-frequency break of the spectrum from Pushchino catalogue. A theoretical explanation of the observed dependence of the high-frequency break from the pulsar period is given. The dependence of the break position from the magnetic field is predicted. This explanation is based on a new mechanism for electron emission in the inner polar gap. Radiation occurs when electrons are accelerated in the electric field rising from zero at the star surface. Acceleration passes through a maximum and tends to zero when the electron velocity approaches the velocity of light. The all radiated power is allocated to the radio band. The averaging over the polar cap, with some nat...

  8. X-ray and Rotational Luminosity Correlation and Magnetic Heating of the Radio Pulsars

    CERN Document Server

    Shibata, S; Yatsu, Y; Enoto, T; Bamba, A

    2016-01-01

    Previous works have suggested a correlation between the X-ray luminosity Lx and the rotational luminosity Lrot of the radio pulsars.However, none of the obtained regression lines are statistically acceptable due to large scatters. We construct a statistical model which has an intrinsic Lx-Lrot relation and reproduces the observed Lx distribution about it by using a Monte Carlo simulator, which takes into account the effects obscuring the intrinsic relation,i.e., the anisotropy of radiation, additional heating, uncertainty in distance and detection limit of the instruments. From the ATNF pulsar catalog we collect 57 `ordinary radio pulsars' with significant detection and 42 with upper limits.The sample does not include the high-magnetic field pulsars (>10^{13} G), which are separately analyzed. We obtain a statistically acceptable relation Lx (0.5 - 10 keV)= 10^{31.69} (Lrot / L_0)^{c_1} with c_1 = 1.03 \\pm 0.27 and L_0 =10^{35.38}. The distribution about the obtained Lx-Lrot relation is reproduced well by the...

  9. Particle acceleration and radio emission for SGRs/AXPs as white dwarf pulsars

    Science.gov (United States)

    Lobato, R. V.; Coelho, Jaziel; Malheiro, M.

    2015-07-01

    Recently, an alternative model based on white dwarfs pulsars has been proposed to explain a class of pulsars known as Soft Gamma Repeaters (SGR) and Anomalus X-Ray Pulsars (AXP) [6][4], usually named as magnetars. In this model the magnetized white dwarfs can have surface magnetic field B ∼ 107 — 1010G and rotate very fast with frequencies ω ∼ 1 rad/s, allowing them to produce large electromagnetic (EM) potentials and generate electron-positron pairs. These EM potentials are comparable with the ones of neutron stars pulsars with strong magnetic fields. In our study we consider two possible processes associated with the particle acceleration: in one we have the pair production near to the star polar caps i.e., inside the light cylinder where magnetic-field lines are closed, on the other the creation of pair is in the Outer Magnetosphere i.e., far away of the star surface where magnetic field are open [1]. This analysis of the possibility of radio emission was done for all the 23 SGRs/AXPs of the McGill Online Magnetar Catalog [7] that contains the current information available on these sources. Our work is a first attempted to find an explanation for the puzzle why for all the SGRs/AXPs was expected radio emission, but it was observed in only four of them.

  10. Einstein@Home DISCOVERY OF A PALFA MILLISECOND PULSAR IN AN ECCENTRIC BINARY ORBIT

    Energy Technology Data Exchange (ETDEWEB)

    Knispel, B.; Allen, B. [Leibniz Universität, Hannover, D-30167 Hannover (Germany); Lyne, A. G.; Stappers, B. W. [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL (United Kingdom); Freire, P. C. C.; Lazarus, P. [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Aulbert, C.; Bock, O.; Eggenstein, H.-B.; Fehrmann, H. [Max-Planck-Institut für Gravitationsphysik, Callinstr. 38, D-30167 Hannover (Germany); Bogdanov, S.; Camilo, F. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Brazier, A.; Chatterjee, S.; Cordes, J. M. [Department of Astronomy and Center for Radiophysics and Space Research, Cornell University, Ithaca, NY 14853 (United States); Cardoso, F. [Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506 (United States); Crawford, F. [Department of Physics and Astronomy, Franklin and Marshall College, Lancaster, PA 17604-3003 (United States); Deneva, J. S. [National Research Council, resident at the Naval Research Laboratory, Washington, DC 20375 (United States); Ferdman, R. [Department of Physics, McGill University, Montreal, QC H3A 2T8 (Canada); Hessels, J. W. T., E-mail: benjamin.knispel@aei.mpg.de [ASTRON, Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA, Dwingeloo (Netherlands); and others

    2015-06-10

    We report the discovery of the millisecond pulsar (MSP) PSR J1950+2414 (P = 4.3 ms) in a binary system with an eccentric (e = 0.08) 22 day orbit in Pulsar Arecibo L-band Feed Array survey observations with the Arecibo telescope. Its companion star has a median mass of 0.3 M{sub ⊙} and is most likely a white dwarf (WD). Fully recycled MSPs like this one are thought to be old neutron stars spun-up by mass transfer from a companion star. This process should circularize the orbit, as is observed for the vast majority of binary MSPs, which predominantly have orbital eccentricities e < 0.001. However, four recently discovered binary MSPs have orbits with 0. 027 < e < 0.44; PSR J1950+2414 is the fifth such system to be discovered. The upper limits for its intrinsic spin period derivative and inferred surface magnetic field strength are comparable to those of the general MSP population. The large eccentricities are incompatible with the predictions of the standard recycling scenario: something unusual happened during their evolution. Proposed scenarios are (a) initial evolution of the pulsar in a triple system which became dynamically unstable, (b) origin in an exchange encounter in an environment with high stellar density, (c) rotationally delayed accretion-induced collapse of a super-Chandrasekhar WD, and (d) dynamical interaction of the binary with a circumbinary disk. We compare the properties of all five known eccentric MSPs with the predictions of these formation channels. Future measurements of the masses and proper motion might allow us to firmly exclude some of the proposed formation scenarios.

  11. Einstein@Home Discovery of a PALFA Millisecond Pulsar in an Eccentric Binary Orbit

    Science.gov (United States)

    Knispel, B.; Lyne, A. G.; Stappers, B. W.; Freire, P. C. C.; Lazarus, P.; Allen, B.; Aulbert, C.; Bock, O.; Bogdanov, S.; Brazier, A.; Camilo, F.; Cardoso, F.; Chatterjee, S.; Cordes, J. M.; Crawford, F.; Deneva, J. S.; Eggenstein, H.-B.; Fehrmann, H.; Ferdman, R.; Hessels, J. W. T.; Jenet, F. A.; Karako-Argaman, C.; Kaspi, V. M.; van Leeuwen, J.; Lorimer, D. R.; Lynch, R.; Machenschalk, B.; Madsen, E.; McLaughlin, M. A.; Patel, C.; Ransom, S. M.; Scholz, P.; Siemens, X.; Spitler, L. G.; Stairs, I. H.; Stovall, K.; Swiggum, J. K.; Venkataraman, A.; Wharton, R. S.; Zhu, W. W.

    2015-06-01

    We report the discovery of the millisecond pulsar (MSP) PSR J1950+2414 (P = 4.3 ms) in a binary system with an eccentric (e = 0.08) 22 day orbit in Pulsar Arecibo L-band Feed Array survey observations with the Arecibo telescope. Its companion star has a median mass of 0.3 M⊙ and is most likely a white dwarf (WD). Fully recycled MSPs like this one are thought to be old neutron stars spun-up by mass transfer from a companion star. This process should circularize the orbit, as is observed for the vast majority of binary MSPs, which predominantly have orbital eccentricities e < 0.001. However, four recently discovered binary MSPs have orbits with 0. 027 < e < 0.44; PSR J1950+2414 is the fifth such system to be discovered. The upper limits for its intrinsic spin period derivative and inferred surface magnetic field strength are comparable to those of the general MSP population. The large eccentricities are incompatible with the predictions of the standard recycling scenario: something unusual happened during their evolution. Proposed scenarios are (a) initial evolution of the pulsar in a triple system which became dynamically unstable, (b) origin in an exchange encounter in an environment with high stellar density, (c) rotationally delayed accretion-induced collapse of a super-Chandrasekhar WD, and (d) dynamical interaction of the binary with a circumbinary disk. We compare the properties of all five known eccentric MSPs with the predictions of these formation channels. Future measurements of the masses and proper motion might allow us to firmly exclude some of the proposed formation scenarios.

  12. Resolving multiple supermassive black hole binaries with pulsar timing arrays II: genetic algorithm implementation

    CERN Document Server

    Petiteau, Antoine; Sesana, Alberto; de Araujo, Mariana

    2012-01-01

    Pulsar timing arrays (PTAs) might detect gravitational waves (GWs) from massive black hole (MBH) binaries within this decade. The signal is expected to be an incoherent superposition of several nearly-monochromatic waves of different strength. The brightest sources might be individually resolved, and the overall deconvolved, at least partially, in its individual components. In this paper we extend the maximum-likelihood based method developed in Babak & Sesana 2012, to search for individual MBH binaries in PTA data. We model the signal as a collection of circular monochromatic binaries, each characterized by three free parameters: two angles defining the sky location, and the frequency. We marginalize over all other source parameters and we apply an efficient multi-search genetic algorithm to maximize the likelihood function and look for sources in synthetic datasets. On datasets characterized by white Gaussian noise plus few injected sources with signal-to-noise ratio (SNR) in the range 10-60, our search...

  13. A Magnetar-like Outburst from a High-B Radio Pulsar

    Science.gov (United States)

    Archibald, R. F.; Kaspi, V. M.; Tendulkar, S. P.; Scholz, P.

    2016-09-01

    Radio pulsars are believed to have their emission powered by the loss of rotational kinetic energy. By contrast, magnetars show intense X-ray and γ-ray radiation whose luminosity greatly exceeds that due to spin down and magnetar luminosity is believed to be powered by intense internal magnetic fields. A basic prediction of this picture is that radio pulsars of high magnetic field should show magnetar-like emission. Here we report on a magnetar-like X-ray outburst from the radio pulsar PSR J1119-6127, heralded by two short bright X-ray bursts on 2016 July 27 and 28. Using target of opportunity data from the Swift X-ray Telescope and NuSTAR, we show that this pulsar’s flux has brightened by a factor of \\gt 160 in the 0.5-10 keV band, and that its previously soft X-ray spectrum has undergone a strong hardening with strong pulsations appearing for the first time above 2.5 keV, with phase-averaged emission detectable up to 25 keV. By comparing Swift-XRT and NuSTAR timing data with a pre-outburst ephemeris derived from Fermi Large Area Telescope data, we find that the source has contemporaneously undergone a large spin-up glitch of amplitude {{Δ }}ν /ν =5.74(8)× {10}-6. The collection of phenomena observed thus far in this outburst strongly mirrors those in most magnetar outbursts and provides an unambiguous connection between the radio pulsar and magnetar populations.

  14. Radio upper limits for the accreting millisecond X-ray pulsar IGR J17511-3057

    Science.gov (United States)

    Miller-Jones, J. C. A.; Russell, D. M.; Migliari, S.

    2009-10-01

    We report on recent radio observations of the newly-detected accreting millisecond X-ray pulsar, IGR J17511-3057 (ATels #2196, #2197, #2198, #2199, #2215, #2216, #2220, #2221). We used the Very Large Array (VLA) to observe the source under observing program AM971. The array was in its relatively compact 'C' and 'DNC' configurations, and the observations were made at 8.46 GHz. In no case was the source significantly detected.

  15. Thermal Radio Emission from Radiative Shocks in Colliding Wind Binaries

    Science.gov (United States)

    Montes, G.; González, R. F.; Cantó, J.; Pérez-Torres, M. A.; Alberdi, A.

    2011-10-01

    We present a semi-analytic model for computing the thermal radio continuum emission from radiative shocks within colliding wind binaries. Assuming a thin shell approximation, we calculate the contribution of the wind collision region (WCR) to the total thermal emission for close binaries. We investigate the effect of the binary separation on the total spectrum. In addition, we point out the relevance of taking into account this contribution for the correct interpretation of the observations, and the accuracy of parameters derived from them.

  16. A Stochastic Acceleration Model of Radio Emission from Pulsar Wind Nebulae

    Science.gov (United States)

    Tanaka, S.; Asano, K.

    2016-06-01

    The broadband emission of Pulsar Wind Nebulae (PWNe) is well described by non-thermal emissions from accelerated electrons and positrons. However, the difference of spectral indices at radio and X-rays are not reproduced by the standard shock particle acceleration and cooling processes, and then, for example, the broken power-law spectrum for the particle energy distribution at the injection has been groundlessly adopted. Here, we propose a possible resolution for the particle distribution; the radio emitting particles are not accelerated at the pulsar wind termination shock but are stochastically accelerated by turbulence inside the PWNe. The turbulence may be induced by the interaction of the pulsar wind with the supernova ejecta. We upgrade our one-zone spectral evolution model including the stochastic acceleration and apply it to the Crab Nebula. We consider both continuous and impulsive injections of particles to the stochastic acceleration process. The radio emission in the Crab Nebula is reproduced by our stochastic acceleration model. The required forms of the momentum diffusion coefficient will be discussed.

  17. Population synthesis of radio and gamma-ray millisecond pulsars using Markov Chain Monte Carlo techniques

    Science.gov (United States)

    Gonthier, Peter L.; Koh, Yew-Meng; Kust Harding, Alice

    2016-04-01

    We present preliminary results of a new population synthesis of millisecond pulsars (MSP) from the Galactic disk using Markov Chain Monte Carlo techniques to better understand the model parameter space. We include empirical radio and gamma-ray luminosity models that are dependent on the pulsar period and period derivative with freely varying exponents. The magnitudes of the model luminosities are adjusted to reproduce the number of MSPs detected by a group of thirteen radio surveys as well as the MSP birth rate in the Galaxy and the number of MSPs detected by Fermi. We explore various high-energy emission geometries like the slot gap, outer gap, two pole caustic and pair starved polar cap models. The parameters associated with the birth distributions for the mass accretion rate, magnetic field, and period distributions are well constrained. With the set of four free parameters, we employ Markov Chain Monte Carlo simulations to explore the model parameter space. We present preliminary comparisons of the simulated and detected distributions of radio and gamma-ray pulsar characteristics. We estimate the contribution of MSPs to the diffuse gamma-ray background with a special focus on the Galactic Center.We express our gratitude for the generous support of the National Science Foundation (RUI: AST-1009731), Fermi Guest Investigator Program and the NASA Astrophysics Theory and Fundamental Program (NNX09AQ71G).

  18. The identification of the optical companion to the binary millisecond pulsar J0610-2100 in the Galactic field

    OpenAIRE

    C. Pallanca(University of Bologna); Mignani, R. P.; Dalessandro, E.; Ferraro, F. R.; Lanzoni, B; Possenti, A; Burgay, M; Sabbi, E.

    2012-01-01

    We have used deep V and R images acquired at the ESO Very Large Telescope to identify the optical companion to the binary pulsar PSR J0610-2100, one of the black-widow millisecond pulsars recently detected by the Fermi Gamma-ray Telescope in the Galactic plane. We found a faint star (V~26.7) nearly coincident (\\delta r ~0".28) with the pulsar nominal position. This star is visible only in half of the available images, while it disappears in the deepest ones (those acquired under the best seei...

  19. Finding Pulsars with Einstein@Home

    Science.gov (United States)

    Knispel, Benjamin; Allen, B.; Cordes, J.; Deneva, J.; Anderson, D.; Aulbert, C.; Bhat, N. D. R.; Bock, O.; Bogdanov, S.; Brazier, A.; Camilo, F.; Champion, D. J.; Chatterjee, S.; Crawford, F.; Demorest, P. B.; Fehrmann, H.; Freire, P. C. C.; Gonzalez, M. E.; Hammer, D.; Hessels, J. W. T.; Jenet, F. A.; Kasian, L.; Kaspi, V. M.; Kramer, M.; Lazarus, P.; van Leeuwen, J.; Lorimer, D. R.; Lyne, A. G.; Machenschalk, B.; McLaughlin, M. A.; Messenger, C.; Nice, D. J.; Papa, M. A.; Pletsch, H. J.; Prix, R.; Ransom, S. M.; Siemens, X.; Stairs, I. H.; Stappers, B. W.; Stovall, K.; Venkataraman, A.; Desvignes, G.

    2011-01-01

    The Einstein@Home project is a global distributed computing project and aggregates the computer power of hundreds of thousands of volunteers from 192 countries to "mine" large data sets. Its long-term goal is the detection of continuous gravitational waves in data from the LIGO interferometric gravitational wave detectors. Since March 2009 about a third of Einstein@Home's computation cycles is also used to search for tight binary pulsars in PALFA radio data from the Arecibo observatory. In July 2010, two new pulsars were found by Einstein@Home, J2007+2722 and J1952+26, the latter in a binary system with 9.4 hours orbital period. Here, we present an overview of the status of the Einstein@Home project and describe its search for radio pulsars in binaries with periods larger than 11 minutes. Further, we briefly review Einstein@Home's pulsar discoveries.

  20. Multifrequency Study of Giant Radio Pulses from the Crab Pulsar with K5 VLBI Recording Terminal

    CERN Document Server

    Popov, M V; Kondratiev, V I; Bilous, A V; Moshkina, O; Oreshko, V V; Ilyasov, Yu P; Sekido, M; Kondo, T

    2009-01-01

    Simultaneous multifrequency observations of the Crab pulsar giant pulses (GPs) were performed with the 64-m Kalyazin radio telescope at four frequencies 0.6, 1.4, 2.2 and 8.3 GHz using the K5 VLBI recording terminal. K5 terminal provided continuous recording in 16 4-MHz wide frequency channels distributed over 4 frequency bands. Several thousands of GPs were detected during about 6 hours of observations in two successive days in July 2005. Radio spectra of single GPs were analysed at separate frequencies and over whole frequency range. These spectra manifest notable modulation both on large ($\\Delta\

  1. Einstein@Home Discovery of a PALFA Millisecond Pulsar in an Eccentric Binary Orbit

    CERN Document Server

    Knispel, B; Stappers, B W; Freire, P C C; Lazarus, P; Allen, B; Aulbert, C; Bock, O; Bogdanov, S; Brazier, A; Camilo, F; Cardoso, F; Chatterjee, S; Cordes, J M; Crawford, F; Deneva, J S; Eggenstein, H -B; Fehrmann, H; Ferdman, R; Hessels, J W T; Jenet, F A; Karako-Argaman, C; Kaspi, V M; van Leeuwen, J; Lorimer, D R; Lynch, R; Machenschalk, B; Madsen, E; McLaughlin, M A; Patel, C; Ransom, S M; Scholz, P; Siemens, X; Spitler, L G; Stairs, I H; Stovall, K; Swiggum, J K; Venkataraman, A; Wharton, R S; Zhu, W W

    2015-01-01

    We report the discovery of the millisecond pulsar (MSP) PSR J1950+2414 ($P=4.3$ ms) in a binary system with an eccentric ($e=0.08$) orbit in Pulsar ALFA survey observations with the Arecibo telescope. Its companion star has a median mass of 0.3 $M_\\odot$ and is most likely a white dwarf. Fully recycled MSPs like this one are thought to be old neutron stars spun-up by mass transfer from a companion star. This process should circularize the orbit, as is observed for the vast majority of binary MSPs, which predominantly have orbital eccentricities $e < 0.001$. However, four recently discovered binary MSPs have orbits with larger eccentricities ($0.03 < e < 0.4$); PSR J1950+2414 is only the fifth such system to be discovered. The upper limits for the the intrinsic spin period derivative and inferred surface magnetic field strength are comparable to those of the general MSP population. The large eccentricities of these systems are not compatible with the predictions of the standard recycling scenario: som...

  2. Spectral Properties of the X-ray Binary Pulsar LMC X-4 during Different Intensity States

    Indian Academy of Sciences (India)

    S. Naik; B. Paul

    2002-03-01

    We present spectral variations of the binary X-ray pulsar LMC X-4 observed with the RXTE/PCA during different phases of its 30.5 day long third period. Only out-of-eclipse data were used for this study. The 3–25 keV spectrum, modeled with high energy cut-off power-law and iron line emission is found to show strong dependence on the intensity state. Correlations between the Fe line emission flux and different parameters of the continuum are presented here.

  3. Testing Lorentz violation with binary pulsars: constraints on standard model extension

    Institute of Scientific and Technical Information of China (English)

    Yi Xie

    2013-01-01

    Under the standard model extension (SME) framework,Lorentz invariance is tested in five binary pulsars:PSR J0737-3039,PSR B 1534+ 12,PSR J 1756-2251,PSR B1913+16 and PSR B2127+11C.By analyzing the advance of periastron,we obtain the constraints on a dimensionless combination of SME parameters that is sensitive to timing observations.The results imply no evidence for the break of Lorentz invariance at the 10-10 level,one order of magnitude larger than the previous estimation.

  4. Using Pulsar Timing observations to understand the formation and evolution of supermassive black hole binaries

    Science.gov (United States)

    Cornish, Neil; Sampson, Laura; McWilliams, Sean

    2015-04-01

    The astrophysical processes that form and harden supermassive black hole binaries impart distinct features that may be observed in the gravitational-wave spectrum within the sensitive frequency range of Pulsar Timing Arrays (PTA). We investigate how well the various formation and hardening mechanisms can be constrained by applying Bayesian inference to simulated PTA data sets. We find that even without strong priors on the merger rate, any detection of the signal will place interesting constraints on the astrophysical models. Folding in priors on the merger rate allows us to place interesting constraints on the astrophysical models even before a detection is made.

  5. Fast radio bursts as giant pulses from young rapidly rotating pulsars

    Science.gov (United States)

    Lyutikov, Maxim; Burzawa, Lukasz; Popov, Sergei B.

    2016-10-01

    We discuss possible association of fast radio bursts (FRBs) with supergiant pulses emitted by young pulsars (ages ˜ tens to hundreds of years) born with regular magnetic field but very short - few milliseconds - spin periods. We assume that FRBs are extra-Galactic events coming from distances d ≲ 100 Mpc and that most of the dispersion measure (DM) comes from the material in the freshly ejected SNR shell. We then predict that for a given burst the DM should decrease with time and that FRBs are not expected to be seen below ˜300 MHz due to free-free absorption in the expanding ejecta. A supernova might have been detected years before the burst; FRBs are mostly associated with star-forming galaxies. The model requires that some pulsars are born with very fast spins, of the order of few milliseconds. The observed distribution of spin-down powers dot{E} in young energetic pulsars is consistent with equal birth rate per decade of dot{E}. Accepting this injection distribution and scaling the intrinsic brightness of FRBs with dot{E}, we predict the following properties of a large sample of FRBs: (i) the brightest observed events come from a broad distribution in distances; (ii) for repeating bursts brightness either remains nearly constant (if the spin-down time is longer than the age of the pulsar) or decreases with time otherwise; in the latter case DM ∝ dot{E}.

  6. Repeating Fast Radio Bursts from Highly Magnetized Pulsars Travelling through Asteroid Belts

    CERN Document Server

    Dai, Z G; Wu, X F; Huang, Y F

    2016-01-01

    Very recently Spitler et al. (2016) reported their detections of ten additional bright bursts from the direction of the fast radio burst (FRB) 121102. This repeating FRB is obviously distinct from the other non-repeating FRBs and thus challenges all of the energy source models but giant pulses from young pulsars. Here we propose a different model, in which highly magnetized pulsars travel through asteroid belts of other stars. We show that a repeating FRB could originate from this pulsar encountering with lots of asteroids in the belt. During such an impact, an electric field induced on a radially elongated, transversely compressed asteroid near the pulsar's surface is strong enough to accelerate electrons to an ultra-relativistic speed instantaneously. Subsequent movement of these electrons along the magnetic field lines not only gives rise to a current loop, but also produces coherent curvature radiation, which can well account for the properties of an FRB. While the high repetitive rate estimated is well c...

  7. Searches for Radio Pulsars & Fast Transients and Multiwavelength Studies of Single-pulse Emission

    Science.gov (United States)

    Mickaliger, Mitchell B.

    1227-6208 has a period of 34.53 ms, a DM of 362.6 pc cm-3, is in a 6.7 day binary orbit. PSR J1546-59 has a period of 7.80 ms and a DM of 168.3 pc cm-3. PSR J1725-3853 is an isolated 4.79-ms pulsar with a DM of 158.2 pc cm-3. PSR J1753-2822 has a period of 18.62 ms, a DM of 298.4 pc cm-3, and is in a 9.3 hour binary orbit. These pulsars were likely missed in earlier processing efforts due to the fact that they have both high DMs and short periods, and also the large number of candidates that needed to be looked through. These discoveries suggest that further pulsars are awaiting discovery in the multibeam survey data. We also searched for single pulses out to a DM of 5000 pc cm-3 with widths of up to two seconds in our reprocessing of the PMPS data. We recorded single pulses from 264 known pulsars and 15 RRATs. We fit amplitude distributions of the pulsars with lognormal distributions and power-law tails, finding that some pulsars show a deviation from a lognormal distribution in the form of an excess of high-energy pulses. Fitting lognormal distributions to the amplitudes of pulses from RRATs showed similar behavior for most RRATs. Here, however, there seem to be two distinct populations of pulses, with the first population being consistent with noise. For pulsars that were detected in a periodicity search, we computed the ratio of their single-pulse S/N to their FFT S/N and looked for correlations between this ratio and physical parameters of the pulsars. We found a few strong correlations, but they all seem to be due to the strongest correlation between the ratio and spin period.

  8. PSR J1753-2240: A mildly recycled pulsar in an eccentric binary system

    CERN Document Server

    Keith, M J; Lyne, A G; Eatough, R P; Stairs, I H; Possenti, A; Camilo, F; Manchester, R N

    2008-01-01

    We report the discovery of PSR J1753-2240 in the Parkes Multibeam Pulsar Survey database. This 95-ms pulsar is in an eccentric binary system with a 13.6-day orbital period. Period derivative measurements imply a characteristic age in excess of 1 Gyr, suggesting that the pulsar has undergone an episode of accretion-induced spin-up. The eccentricity and spin period are indicative of the companion being a second neutron star, so that the system is similar to that of PSR J1811-1736, although other companion types cannot be ruled out at this time. The companion mass is constrained by geometry to lie above 0.48 solar masses, although long-term timing observations will give additional constraints. If the companion is a white dwarf or main sequence star, optical observations may yield a direct detection of the companion. If the system is indeed one of the few known double neutron star systems, it would lie significantly far from the recently proposed spin-period/eccentricity relationship.

  9. FIVE NEW MILLISECOND PULSARS FROM A RADIO SURVEY OF 14 UNIDENTIFIED FERMI-LAT GAMMA-RAY SOURCES

    Energy Technology Data Exchange (ETDEWEB)

    Kerr, M. [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); Camilo, F. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Johnson, T. J. [National Academy of Sciences, Washington, DC 20001 (United States); Ferrara, E. C.; Harding, A. K. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Guillemot, L.; Kramer, M. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn (Germany); Hessels, J. [Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo (Netherlands); Johnston, S.; Keith, M.; Reynolds, J. E. [CSIRO Astronomy and Space Science, Australia Telescope National Facility, Epping, NSW 1710 (Australia); Ransom, S. M. [National Radio Astronomy Observatory (NRAO), Charlottesville, VA 22903 (United States); Ray, P. S.; Wood, K. S. [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States); Sarkissian, J., E-mail: kerrm@stanford.edu, E-mail: fernando@astro.columbia.edu, E-mail: tyrel.j.johnson@gmail.com [CSIRO Parkes Observatory, Parkes, NSW 2870 (Australia)

    2012-03-20

    We have discovered five millisecond pulsars (MSPs) in a survey of 14 unidentified Fermi Large Area Telescope sources in the southern sky using the Parkes radio telescope. PSRs J0101-6422, J1514-4946, and J1902-5105 reside in binaries, while PSRs J1658-5324 and J1747-4036 are isolated. Using an ephemeris derived from timing observations of PSR J0101-6422 (P = 2.57 ms, DM = 12 pc cm{sup -3}), we have detected {gamma}-ray pulsations and measured its proper motion. Its {gamma}-ray spectrum (a power law of {Gamma} = 0.9 with a cutoff at 1.6 GeV) and efficiency are typical of other MSPs, but its radio and {gamma}-ray light curves challenge simple geometric models of emission. The high success rate of this survey-enabled by selecting {gamma}-ray sources based on their detailed spectral characteristics-and other similarly successful searches indicate that a substantial fraction of the local population of MSPs may soon be known.

  10. Five New Millisecond Pulsars from a Radio Survey of 14 Unidentified Fermi-LAT Gamma-Ray Sources

    Science.gov (United States)

    Kerr, M.; Camilo, F.; Johnson, T. J.; Ferrara, E. C.; Guillemot, L.; Harding, A. K.; Hessels, J.; Johnson, S.; Keith, M.; Kramer, M.; Ransom, S. M.; Ray, P. S.; Reynolds, J. E.; Sarkissian, J.; Wood, K. S.

    2012-01-01

    We have discovered five millisecond pulsars (MSPs) in a survey of 14 unidentified Ferm;'LAT sources in the southern sky using the Parkes radio telescope. PSRs J0101-6422, J1514-4946, and J1902-5105 reside in binaries, while PSRs J1658-5324 and J1747-4036 are isolated. Using an ephemeris derived from timing observations of PSR JOl01-6422 (P=2.57ms, DH=12pc/cubic cm ), we have detected gamma-ray pulsations and measured its proper motion. Its gamma-ray spectrum (a power law of Gamma = 0.9 with a cutoff at 1.6 GeV) and efficiency are typical of other MSPs, but its radio and gamma-ray light curves challenge simple geometric models of emission. The high success rate of this survey -- enabled by selecting gamma-ray sources based on their detailed spectral characteristics -- and other similarly successful searches indicate that a substantial fraction of the local population of MSPs may soon be known.

  11. On the evolution of the radio pulsar PSR J1734-3333

    Science.gov (United States)

    Çalişkan, Ş.; Ertan, Ü.; Alpar, M. A.; Trümper, J. E.; Kylafis, N. D.

    2013-05-01

    Recent measurements showed that the period derivative of the `high-B' radio pulsar PSR J1734-3333 is increasing with time. For neutron stars evolving with fallback discs, this rotational behaviour is expected in certain phases of the long-term evolution. Using the same model as employed earlier to explain the evolution of anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters, we show that the period, the first and second period derivatives and the X-ray luminosity of this source can simultaneously acquire the observed values for a neutron star evolving with a fallback disc. We find that the required strength of the dipole field that can produce the source properties is in the range 1012-1013 G on the pole of the neutron star. When the model source reaches the current state properties of PSR J1734-3333, accretion on to the star has not started yet, allowing the source to operate as a regular radio pulsar. Our results imply that PSR J1734-3333 is at an age of ˜3 × 104-2 × 105 yr. Such sources will have properties like the X-ray dim isolated neutron stars or transient AXPs at a later epoch of weak accretion from the diminished fallback disc.

  12. Polarimetric evidence of a white dwarf pulsar in the binary system AR Scorpii

    Science.gov (United States)

    Buckley, D. A. H.; Meintjes, P. J.; Potter, S. B.; Marsh, T. R.; Gänsicke, B. T.

    2017-01-01

    The variable star AR Scorpii (AR Sco) was recently discovered to pulse in brightness every 1.97 min from ultraviolet wavelengths into the radio regime. The system is composed of a cool, low-mass star in a tight, 3.55-hour orbit with a more massive white dwarf. Here we report new optical observations of AR Sco that show strong linear polarization (up to 40%) that varies strongly and periodically on both the spin period of the white dwarf and the beat period between the spin and orbital period, as well as low-level (up to a few per cent) circular polarization. These observations support the notion that, similar to neutron-star pulsars, the pulsed luminosity of AR Sco is powered by the spin-down of the rapidly rotating white dwarf that is highly magnetized (up to 500 MG). The morphology of the modulated linear polarization is similar to that seen in the Crab pulsar, albeit with a more complex waveform owing to the presence of two periodic signals of similar frequency. Magnetic interactions between the two component stars, coupled with synchrotron radiation from the white dwarf, power the observed polarized and non-polarized emission. AR Sco is therefore the first example of a white dwarf pulsar.

  13. Pulsar observations with European telescopes for testing gravity and detecting gravitational waves

    CERN Document Server

    Perrodin, D; Janssen, G H; Karuppusamy, R; Kramer, M; Lee, K; Liu, K; McKee, J; Purver, M; Sanidas, S; Smits, R; Stappers, B W; Zhu, W; Concu, R; Melis, A; Burgay, M; Casu, S; Corongiu, A; Egron, E; Iacolina, N; Pellizzoni, A; Pilia, M; Trois, A

    2016-01-01

    A background of nanohertz gravitational waves from supermassive black hole binaries could soon be detected by pulsar timing arrays, which measure the times-of-arrival of radio pulses from millisecond pulsars with very high precision. The European Pulsar Timing Array uses five large European radio telescopes to monitor high-precision millisecond pulsars, imposing in this way strong constraints on a gravitational wave background. To achieve the necessary precision needed to detect gravitational waves, the Large European Array for Pulsars (LEAP) performs simultaneous observations of pulsars with all five telescopes, which allows us to coherently add the radio pulses, maximize the signal-to-noise of pulsar signals and increase the precision of times-of-arrival. We report on the progress made and results obtained by the LEAP collaboration, and in particular on the addition of the Sardinia Radio Telescope to the LEAP observations during its scientific validation phase. In addition, we discuss how LEAP can be used t...

  14. Relativistic Measurements from Timing the Binary Pulsar PSR B1913+16

    CERN Document Server

    Weisberg, Joel M

    2016-01-01

    We present relativistic analyses of 9257 measurements of times-of-arrival from the first binary pulsar, PSR B1913+16, acquired over the last thirty-five years. The determination of the 'Keplerian' orbital elements plus two relativistic terms completely characterizes the binary system, aside from an unknown rotation about the line of sight; leading to a determination of the masses of the pulsar and its companion: 1.438 $\\pm$ 0.001 solar masses and 1.390 $\\pm$ 0.001 solar masses, respectively. In addition, the complete system characterization allows the creation of tests of relativistic gravitation by comparing measured and predicted sizes of various relativistic phenomena. We find that the ratio of observed orbital period decrease due to gravitational wave damping (corrected by a kinematic term) to the general relativistic prediction, is 0.9983 pm 0.0016; thereby confirming the existence and strength of gravitational radiation as predicted by general relativity. For the first time in this system, we have also ...

  15. BeppoSAX observation of the X-ray binary pulsar Vela X-1

    Science.gov (United States)

    Orlandini, M.; Dal Fiume, D.; Nicastro, L.; Giarrusso, S.; Segreto, A.; Piraino, S.; Cusumano, G.; Del Sordo, S.; Guainazzi, M.; Piro, L.

    1997-05-01

    We report on the spectral (pulse averaged) and timing analysis of the ~20 ksec observation of the X-ray binary pulsar Vela X-1 performed during the BeppoSAX Science Verification Phase. The source was observed in two different intensity states: the low state is probably due to an erratic intensity dip and shows a decrease of a factor ~2 in intensity, and a factor 10 in NH. We have not been able to fit the 2-100 keV continuum spectrum with the standard (for an X-ray pulsar) power law modified by a high energy cutoff because of the flattening of the spectrum in ~10-30 keV. The timing analysis confirms previous results: the pulse profile changes from a five-peak structure for energies less than 15 keV, to a simpler two-peak shape at higher energies. The Fourier analysis shows a very complex harmonic component: up to 23 harmonics are clearly visible in the power spectrum, with a dominant first harmonic for low energy data, and a second one as the more prominent for energies greater than 15 keV. The aperiodic component in the Vela X-1 power spectrum presents a knee at about 1 Hz. The pulse period, corrected for binary motion, is 283.206+/-0.001 sec.

  16. The Correlation between Dispersion Measure and X-ray Column Density from Radio Pulsars

    CERN Document Server

    He, C; Kaspi, V M

    2013-01-01

    Pulsars are remarkable objects that emit across the entire electromagnetic spectrum, providing a powerful probe of the interstellar medium. In this study, we investigate the relation between dispersion measure (DM) and X-ray absorption column density NH using 68 radio pulsars detected at X-ray energies with the Chandra X-ray Observatory or XMM-Newton. We find a best-fit empirical linear relation of NH (10^20 cm^-2)= 0.30+0.13-0.09 DM (pc cm^-3), which corresponds to an average ionization of 10+4-3%, confirming the ratio of one free electron per ten neutral hydrogen atoms commonly assumed in the literature. We also compare different NH estimates and note that some NH values obtained from X-ray observations are higher than the total Galactic HI column density along the same line of sight, while the optical extinction generally gives the best NH predictions.

  17. Investigation of the Earth Ionosphere using the Radio Emission of Pulsars

    CERN Document Server

    Ulyanov, O M; Mukha, D V; Seredkina, A A

    2013-01-01

    The investigation of the Earth ionosphere both in a quiet and a disturbed states is still desirable. Despite recent progress in its modeling and in estimating the electron concentration along the line of sight by GPS signals, the impact of the disturbed ionosphere and magnetic field on the wave propagation still remains not sufficiently understood. This is due to lack of information on the polarization of GPS signals, and due to poorly conditioned models of the ionosphere at high altitudes and strong perturbations. In this article we consider a possibility of using the data of pulsar radio emission, along with the traditional GPS system data, for the vertical and oblique sounding of the ionosphere. This approach also allows to monitor parameters of the propagation medium, such as the dispersion measure and the rotation measure using changes of the polarization between pulses. By using a selected pulsar constellation it is possible to increase the number of directions in which parameters of the ionosphere and ...

  18. Directional Statistics for Polarization Observations of Individual Pulses from Radio Pulsars

    CERN Document Server

    McKinnon, M M

    2010-01-01

    Radio polarimetry is a three-dimensional statistical problem. The three-dimensional aspect of the problem arises from the Stokes parameters Q, U, and V, which completely describe the polarization of electromagnetic radiation and conceptually define the orientation of a polarization vector in the Poincar'e sphere. The statistical aspect of the problem arises from the random fluctuations in the source-intrinsic polarization and the instrumental noise. A simple model for the polarization of pulsar radio emission has been used to derive the three-dimensional statistics of radio polarimetry. The model is based upon the proposition that the observed polarization is due to the incoherent superposition of two, highly polarized, orthogonal modes. The directional statistics derived from the model follow the Bingham-Mardia and Fisher family of distributions. The model assumptions are supported by the qualitative agreement between the statistics derived from it and those measured with polarization observations of the ind...

  19. Detection of cyclotron resonance scattering feature in high-mass X-ray binary pulsar SMC X-2

    Science.gov (United States)

    Jaisawal, Gaurava K.; Naik, Sachindra

    2016-09-01

    We report broad-band spectral properties of the high-mass X-ray binary pulsar SMC X-2 by using three simultaneous Nuclear Spectroscopy Telescope Array and Swift/XRT observations during its 2015 outburst. The pulsar was significantly bright, reaching a luminosity up to as high as ˜5.5 × 1038 erg s-1 in 1-70 keV range. Spin period of the pulsar was estimated to be 2.37 s. Pulse profiles were found to be strongly luminosity dependent. The 1-70 keV energy spectrum of the pulsar was well described with three different continuum models such as (i) negative and positive power law with exponential cutoff, (ii) Fermi-Dirac cutoff power law and (iii) cutoff power-law models. Apart from the presence of an iron line at ˜6.4 keV, a model independent absorption like feature at ˜27 keV was detected in the pulsar spectrum. This feature was identified as a cyclotron absorption line and detected for the first time in this pulsar. Corresponding magnetic field of the neutron star was estimated to be ˜2.3 × 1012 G. The cyclotron line energy showed a marginal negative dependence on the luminosity. The cyclotron line parameters were found to be variable with pulse phase and interpreted as due to the effect of emission geometry or complicated structure of the pulsar magnetic field.

  20. Einstein@Home Discovery of 24 Pulsars in the Parkes Multi-beam Pulsar Survey

    CERN Document Server

    Knispel, B; Kim, H; Keane, E F; Allen, B; Anderson, D; Aulbert, C; Bock, O; Crawford, F; Eggenstein, H -B; Fehrmann, H; Hammer, D; Kramer, M; Lyne, A G; Machenschalk, B; Miller, R B; Papa, M A; Rastawicki, D; Sarkissian, J; Siemens, X; Stappers, B W

    2013-01-01

    We have conducted a new search for radio pulsars in compact binary systems in the Parkes multi-beam pulsar survey (PMPS) data, employing novel methods to remove the Doppler modulation from binary motion. This has yielded unparalleled sensitivity to pulsars in compact binaries. The required computation time of approximately 17 000 CPU core years was provided by the distributed volunteer computing project Einstein@Home, which has a sustained computing power of about one PFlop/s. We discovered 24 new pulsars in our search, of which 18 were isolated pulsars, and six were members of binary systems. Despite the wide filterbank channels and relatively slow sampling time of the PMPS data, we found pulsars with very large ratios of dispersion measure (DM) to spin period. Among those is PSR J1748-3009, the millisecond pulsar with the highest known DM (420 pc cm^{-3}). We also discovered PSR J1840-0643, which is in a binary system with an orbital period of 937 days, the fourth largest known. The new pulsar J1750-2531 li...

  1. A Strange Star Scenario for the Formation of Eccentric Millisecond Pulsar/Helium White Dwarf Binaries

    CERN Document Server

    Jiang, Long; Dey, Jishnu; Dey, Mira

    2015-01-01

    According to the recycling scenario, millisecond pulsars (MSPs) have evolved from low-mass X-ray binaries (LMXBs). Their orbits are expected to be circular due to tidal interactions during the binary evolution, as observed in most of the binary MSPs. There are some peculiar systems that do not fit this picture. Three recent examples are PSRs J2234$+$06, J1946$+$3417 and J1950$+$2414, all of which are MSPs in eccentric orbits but with mass functions compatible with expected He white dwarf companions. It has been suggested these MSPs may have formed from delayed accretion-induced collapse of massive white dwarfs, or the eccentricity may be induced by dynamical interaction between the binary and a circumbinary disk. Assuming that the core density of accreting neutron stars in LMXBs may reach the density of quark deconfinement, which can lead to phase transition from neutron stars to strange quark stars, we show that the resultant MSPs are likely to have an eccentric orbit, due to the sudden loss of the gravitati...

  2. Long-term Radio Observations of the Intermittent Pulsar B1931+24

    CERN Document Server

    Young, N J; Lyne, A G; Weltevrede, P; Kramer, M; Cognard, I

    2012-01-01

    We present an analysis of approximately 13-yr of observations of the intermittent pulsar B1931+24 to further elucidate its behaviour. We find that while the source exhibits a wide range of nulling (~4-39 d) and radio-emitting (~1-19 d) timescales, it cycles between its different emission phases over an average timescale of approximately 38 d, which is remarkably stable over many years. On average, the neutron star is found to be radio emitting for 26 +- 6 % of the time. No evidence is obtained to suggest that the pulsar undergoes any systematic, intrinsic variations in pulse intensity during the radio-emitting phases. In addition, we find no evidence for any correlation between the length of consecutive emission phases. An analysis of the rotational behaviour of the source shows that it consistently assumes the same spin-down rates, i.e. nudot = -16 +- 1 x 10^-15 s^-2 when emitting and nudot = -10.8 +- 0.4 x 10^-15 s^-2 when not emitting, over the entire observation span. Coupled with the stable switching tim...

  3. The binary millisecond pulsar PSR J1023+0038 during its accretion state - I. Optical variability

    Science.gov (United States)

    Shahbaz, T.; Linares, M.; Nevado, S. P.; Rodríguez-Gil, P.; Casares, J.; Dhillon, V. S.; Marsh, T. R.; Littlefair, S.; Leckngam, A.; Poshyachinda, S.

    2015-11-01

    We present time-resolved optical photometry of the binary millisecond `redback' pulsar PSR J1023+0038 (=AY Sex) during its low-mass X-ray binary phase. The light curves taken between 2014 January and April show an underlying sinusoidal modulation due to the irradiated secondary star and accretion disc. We also observe superimposed rapid flaring on time-scales as short as ˜20 s with amplitudes of ˜0.1-0.5 mag and additional large flare events on time-scales of ˜5-60 min with amplitudes of ˜0.5-1.0 mag. The power density spectrum of the optical flare light curves is dominated by a red-noise component, typical of aperiodic activity in X-ray binaries. Simultaneous X-ray and UV observations by the Swift satellite reveal strong correlations that are consistent with X-ray reprocessing of the UV light, most likely in the outer regions of the accretion disc. On some nights we also observe sharp-edged, rectangular, flat-bottomed dips randomly distributed in orbital phase, with a median duration of ˜250 s and a median ingress/egress time of ˜20 s. These rectangular dips are similar to the mode-switching behaviour between disc `active' and `passive' luminosity states, observed in the X-ray light curves of other redback millisecond pulsars. This is the first time that the optical analogue of the X-ray mode-switching has been observed. The properties of the passive- and active-state light curves can be explained in terms of clumpy accretion from a trapped inner accretion disc near the corotation radius, resulting in rectangular, flat-bottomed optical and X-ray light curves.

  4. Discovery of the Binary Pulsar PSR B1259-63 in Very-High-Energy Gamma Rays around Periastron with H.E.S.S

    CERN Document Server

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

    2005-01-01

    We report the discovery of very-high-energy (VHE) gamma-ray emission of the binary system PSR B1259-63/SS 2883 of a radio pulsar orbiting a massive, luminous Be star in a highly eccentric orbit. The observations around the 2004 periastron passage of the pulsar were performed with the four 13 m Cherenkov telescopes of the H.E.S.S. experiment, recently installed in Namibia and in full operation since December 2003. Between February and June 2004, a gamma-ray signal from the binary system was detected with a total significance above 13 sigma. The flux was found to vary significantly on timescales of days which makes PSR B1259-63 the first variable galactic source of VHE gamma-rays observed so far. Strong emission signals were observed in pre- and post-periastron phases with a flux minimum around periastron, followed by a gradual flux decrease in the months after. The measured time-averaged energy spectrum above a mean threshold energy of 380 GeV can be fitted by a simple power law F_0(E/1 TeV)^-Gamma with a phot...

  5. DISCOVERY OF PSR J1227−4853: A TRANSITION FROM A LOW-MASS X-RAY BINARY TO A REDBACK MILLISECOND PULSAR

    Energy Technology Data Exchange (ETDEWEB)

    Roy, Jayanta; Bhattacharyya, Bhaswati; Stappers, Ben [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, M13 9PL (United Kingdom); Ray, Paul S.; Wolff, Michael; Wood, Kent S. [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States); Chengalur, Jayaram N. [National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune 411 007 (India); Deneva, Julia [NRC Research Associate, resident at Naval Research Laboratory, Washington, DC 20375-5352 (United States); Camilo, Fernando [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Johnson, Tyrel J. [College of Science, George Mason University, Fairfax, VA 22030, USA, resident at Naval Research Laboratory, Washington, DC 20375 (United States); Hessels, Jason W. T.; Bassa, Cees G. [ASTRON, the Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA, Dwingeloo (Netherlands); Keane, Evan F. [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Mail H30, P.O. Box 218, VIC 3122 (Australia); Ferrara, Elizabeth C.; Harding, Alice K. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2015-02-10

    XSS J12270−4859 is an X-ray binary associated with the Fermi Large Area Telescope gamma-ray source 1FGL J1227.9−4852. In 2012 December, this source underwent a transition where the X-ray and optical luminosity dropped and the spectral signatures of an accretion disk disappeared. We report the discovery of a 1.69 millisecond pulsar (MSP), PSR J1227−4853, at a dispersion measure of 43.4 pc cm{sup −3} associated with this source, using the Giant Metrewave Radio Telescope (GMRT) at 607 MHz. This demonstrates that, post-transition, the system hosts an active radio MSP. This is the third system after PSR J1023+0038 and PSR J1824−2452I showing evidence of state switching between radio MSP and low-mass X-ray binary states. We report timing observations of PSR J1227−4853 with the GMRT and Parkes, which give a precise determination of the rotational and orbital parameters of the system. The companion mass measurement of 0.17–0.46 M{sub ⊙} suggests that this is a redback system. PSR J1227−4853 is eclipsed for about 40% of its orbit at 607 MHz with additional short-duration eclipses at all orbital phases. We also find that the pulsar is very energetic, with a spin-down luminosity of ∼10{sup 35} erg s{sup −1}. We report simultaneous imaging and timing observations with the GMRT, which suggests that eclipses are caused by absorption rather than dispersion smearing or scattering.

  6. Radio detection of the young binary HD 160934

    CERN Document Server

    Azulay, R; Marcaide, J M; Marti-Vidal, I; Arroyo-Torres, B

    2013-01-01

    Precise determination of dynamical masses of pre-main-sequence (PMS) stars is essential to calibrate stellar evolution models that are widely used to derive theoretical masses of young low-mass objects. Binary stars in young, nearby loose associations are particularly good candidates for this calibration since all members share a common age. Interestingly, some of these young binaries present a persistent and compact radio emission, which makes them excellent targets for astrometric VLBI studies. We aim to monitor the orbital motion of the binary system HD 160934, a member of the AB Doradus moving group. We observed HD 160934 with the Very Large Array and the European VLBI Network at 8.4 and 5 GHz, respectively. The orbital information derived from these observations was analyzed along with previously reported orbital measurements. We show that the two components of the binary, HD 160934 A and HD 160934 c, display compact radio emission at VLBI scales, providing precise information on the relative orbit. Revi...

  7. Radio detection of the young binary HD 160934

    Science.gov (United States)

    Azulay, R.; Guirado, J. C.; Marcaide, J. M.; Martí-Vidal, I.; Arroyo-Torres, B.

    2014-01-01

    Context. Precise determination of dynamical masses of pre-main-sequence (PMS) stars is essential to calibrate stellar evolution models that are widely used to derive theoretical masses of young low-mass objects. Binary stars in young, nearby loose associations are particularly good candidates for this calibration since all members share a common age. Interestingly, some of these young binaries present a persistent and compact radio emission, which makes them excellent targets for astrometric VLBI studies. Aims: We aim to monitor the orbital motion of the binary system HD 160934, a member of the AB Doradus moving group. Methods: We observed HD 160934 with the Very Large Array and the European VLBI Network at 8.4 and 5 GHz, respectively. The orbital information derived from these observations was analyzed along with previously reported orbital measurements. Results: We show that the two components of the binary, HD 160934 A and HD 160934 c, display compact radio emission at VLBI scales, providing precise information on the relative orbit. Revised orbital elements were estimated. Conclusions: Future VLBI monitoring of this pair should determine precise model-independent mass estimates for the A and c components, which will serve as calibration tests for PMS evolutionary models.

  8. Fast radio bursts as giant pulses from young rapidly rotating pulsars

    CERN Document Server

    Lyutikov, Maxim; Popov, Sergei B

    2016-01-01

    We discuss possible association of fast radio bursts (FRBs) with supergiant pulses emitted by young pulsars (ages $\\sim$ tens to hundreds of years) born with regular magnetic field but very short -- few milliseconds -- spin periods. FRBs are extra-Galactic events coming from distances $d \\lesssim 100$ Mpc. Most of the dispersion measure (DM) comes from the material in the freshly ejected SNR shell; for a given burst the DM should decrease with time. FRBs are not expected to be seen below $\\sim 300 $ MHz due to free-free absorption in the expanding ejecta. A supernova might have been detected years before the burst; FRBs are mostly associated with star forming galaxies. The model requires that some pulsars are born with very fast spins, of the order of few milliseconds. The observed distribution of spin-down powers $\\dot{E}$ in young energetic pulsars is consistent with equal birth rate per decade of $\\dot{E}$. Accepting this injection spectrum and scaling the intrinsic brightness of FRBs with $\\dot{E}$, we pr...

  9. Millisecond and Binary Pulsars as Nature's Frequency Standards; 3, Fourier Analysis and Spectral Sensitivity of Timing Observations to Low-Frequency Noise

    CERN Document Server

    Kopeikin, S M; Kopeikin, Sergei M.; Potapov, Vladimir A.

    1998-01-01

    Millisecond and binary pulsars are the most stable natural frequency standards which admits to introduce modified versions of universal and ephemeris time scales based correspondingly on the intrinsic rotation of pulsar and on its orbital motion around barycenter of a binary system. Measured stability of these time scales depends on numerous physical phenomena which affect rotational and orbital motion of the pulsar and observer on the Earth, perturb propagation of electromagnetic pulses from pulsar to the observer and bring about random fluctuations in the rate of atomic clock used as a primary time reference in timing observations. On the long time intervals the main reason for the instability of the pulsar time scales is the presence of correlated, low-frequency timing noise in residuals of times of arrivals (TOA) of pulses from the pulsar which has both astrophysical and geophysical origin. Hence, the timing noise can carry out the important physical information about interstellar medium, interior structu...

  10. Tests of the universality of free fall for strongly self-gravitating bodies with radio pulsars

    CERN Document Server

    Freire, Paulo C C; Wex, Norbert

    2012-01-01

    In this paper, we review tests of the strong equivalence principle (SEP) derived from binary pulsar data. The extreme difference in binding energy between both components and the precise measurement of the orbital motion provided by pulsar timing allow the only current precision SEP tests for strongly self-gravitating bodies. We start by highlighting why such tests are conceptually important. We then review previous work where limits on SEP violation are obtained with an ensemble of wide binary systems with small eccentricity orbits. Then we propose a new SEP violation test based on the measurement of the variation of the orbital eccentricity de/dt. This new method has the following advantages: a) unlike previous methods it is not based on probabilistic considerations, b) it can make a direct detection of SEP violation, c) the measurement of de/dt is not contaminated by any known external effects, which implies that this SEP test is only restricted by the measurement precision of de/dt. In the final part of t...

  11. Tests of the universality of free fall for strongly self-gravitating bodies with radio pulsars

    Science.gov (United States)

    Freire, Paulo C. C.; Kramer, Michael; Wex, Norbert

    2012-09-01

    In this paper, we review tests of the strong equivalence principle (SEP) derived from pulsar-white dwarf binary data. The extreme difference in the binding energy between both components and the precise measurement of the orbital motion provided by pulsar timing allow the only current precision SEP tests for strongly self-gravitating bodies. We start by highlighting why such tests are conceptually important. We then review previous work where limits on SEP violation are obtained with an ensemble of wide binary systems with small eccentricity orbits. Then, we propose a new SEP violation test based on the measurement of the variation of the orbital eccentricity (ė). This new method has the following advantages: (a) unlike previous methods it is not based on probabilistic considerations, (b) it can make a direct detection of SEP violation and (c) the measurement of ė is not contaminated by any known external effects, which implies that this SEP test is only restricted by the measurement precision of ė. In the final part of the review, we conceptually compare the SEP test with the test for dipolar radiation damping, a phenomenon closely related to SEP violation, and speculate on future prospects by new types of tests in globular clusters and future triple systems.

  12. The identification of the optical companion to the binary millisecond pulsar J0610-2100 in the Galactic field

    CERN Document Server

    Pallanca, C; Dalessandro, E; Ferraro, F R; Lanzoni, B; Possenti, A; Burgay, M; Sabbi, E

    2012-01-01

    We have used deep V and R images acquired at the ESO Very Large Telescope to identify the optical companion to the binary pulsar PSR J0610-2100, one of the black-widow millisecond pulsars recently detected by the Fermi Gamma-ray Telescope in the Galactic plane. We found a faint star (V~26.7) nearly coincident (\\delta r ~0".28) with the pulsar nominal position. This star is visible only in half of the available images, while it disappears in the deepest ones (those acquired under the best seeing conditions), thus indicating that it is variable. Although our observations do not sample the entire orbital period (P=0.28 d) of the pulsar, we found that the optical modulation of the variable star nicely correlates with the pulsar orbital period and describes a well defined peak (R~25.6) at \\Phi=0.75, suggesting a modulation due to the pulsar heating. We tentatively conclude that the companion to PSR J0610-2100 is a heavily ablated very low mass star (~ 0.02Msun) that completely filled its Roche Lobe.

  13. Astrophysical constraints on massive black hole binary evolution from Pulsar Timing Arrays

    CERN Document Server

    Middleton, Hannah; Farr, Will M; Sesana, Alberto; Vecchio, Alberto

    2015-01-01

    We consider massive black hole binary systems and information that can be derived about their population and formation history solely from current and possible future pulsar timing array (PTA) results. We use models of the stochastic gravitational-wave background from circular massive black hole binaries with chirp mass in the range $10^6 - 10^{11} M_\\odot$ evolving solely due to radiation reaction. Our parameterised models for the black hole merger history make only weak assumptions about the properties of the black holes merging over cosmic time. We show that current PTA results place a model-independent upper limit on the merger density of massive black hole binaries, but provide no information about their redshift or mass distribution. We show that even in the case of a detection resulting from a factor of 10 increase in amplitude sensitivity, PTAs will only put weak constraints on the source merger density as a function of mass, and will not provide any additional information on the redshift distribution...

  14. The binary millisecond pulsar PSR J1023+0038 during its accretion state - I. Optical variability

    CERN Document Server

    Shahbaz, T; Nevado, S P; Rodríguez-Gil, P; Casares, J; Dhillon, V S; Marsh, T R; Littlefair, S; Leckngam, A; Poshyachinda, S

    2015-01-01

    We present time-resolved optical photometry of the binary millisecond `redback' pulsar PSR J1023+0038 (=AY Sex) during its low-mass X-ray binary phase. The light curves taken between 2014 January and April show an underlying sinusoidal modulation due to the irradiated secondary star and accretion disc. We also observe superimposed rapid flaring on time-scales as short as ~20 s with amplitudes of ~0.1-0.5 mag and additional large flare events on time-scales of ~5-60 min with amplitudes ~0.5-1.0 mag. The power density spectrum of the optical flare light curves is dominated by a red-noise component, typical of aperiodic activity in X-ray binaries. Simultaneous X-ray and UV observations by the Swift satellite reveal strong correlations that are consistent with X-ray reprocessing of the UV light, most likely in the outer regions of the accretion disc. On some nights we also observe sharp-edged, rectangular, flat-bottomed dips randomly distributed in orbital phase, with a median duration of ~250 s and a median ingr...

  15. A LIKELY MILLISECOND PULSAR BINARY COUNTERPART FOR FERMI SOURCE 2FGL J2039.6–5620

    Energy Technology Data Exchange (ETDEWEB)

    Romani, Roger W., E-mail: rwr@astro.stanford.edu [Department of Physics, Stanford University, Stanford, CA 94305-4060 (United States)

    2015-10-20

    We have identified an optical/X-ray binary with an orbital period of P{sub b} = 5.47 hr as the likely counterpart of the Fermi source 2FGL J2039.6−5620. GROND, SOAR, and DES observations provide an accurate orbital period and allow us to compare to the light curve of an archival XMM exposure. Like many short-period optical/X-ray binaries associated with Large Area Telescope sources, this may be an interacting (black widow/redback) millisecond pulsar binary. The X-ray light curve is consistent with the emission associated with an intrabinary shock. The optical light curve shows evidence of companion heating, but has a peculiar asymmetric double peak. The nature of this optical structure is not yet clear; additional optical studies and, in particular, detection of an orbital modulation in a γ-ray pulsar are needed to elucidate the nature of this peculiar source.

  16. Carrying the physics of black-hole binary evolution into gravitational-wave models for pulsar-timing arrays

    Science.gov (United States)

    Taylor, Stephen; Sampson, Laura; Simon, Joseph

    2016-03-01

    There has recently been significant interest in how the galactic environments of supermassive black-hole binaries influences the stochastic gravitational-wave background signal from a population of these systems, and in how the resulting detection prospects for pulsar-timing arrays are effected. Tackling these problems requires us to have robust and computationally-efficient models for the strain spectrum as a function of different environment influences or the binary orbital eccentricity. In this talk we describe a new method of constructing these models from a small number of synthesized black-hole binary populations which have varying input physics. We use these populations to train an interpolant via Gaussian-process regression, allowing us to carry real physics into our subsequent pulsar-timing array inferences, and to also correctly propagate forward uncertainties from our interpolation.

  17. A Highly Eccentric 3.9-Millisecond Binary Pulsar in the Globular Cluster NGC 6652

    CERN Document Server

    DeCesar, Megan E; Kaplan, David L; Ray, Paul S; Geller, Aaron M

    2015-01-01

    We present the Robert C. Byrd Green Bank Telescope discovery of the highly eccentric binary millisecond pulsar PSR J1835$-$3259A in the Fermi Large Area Telescope-detected globular cluster NGC 6652. Timing over one orbit yields the pulse period 3.89 ms, orbital period 9.25 d, eccentricity $\\sim 0.95$, and an unusually high companion mass of $0.74\\,M_{\\odot}$ assuming a $1.4\\,M_{\\odot}$ pulsar. We caution that the lack of data near periastron prevents a precise measurement of the eccentricity, and that further timing is necessary to constrain this and the other orbital parameters. From tidal considerations, we find that the companion must be a compact object. This system likely formed through an exchange encounter in the dense cluster environment. Our initial timing results predict the measurements of at least two post-Keplerian parameters with long-term phase-connected timing: the rate of periastron advance $\\dot{\\omega} \\sim 0.1^{\\circ}\\,$yr$^{-1}$, requiring 1 yr of phase connection; and the Einstein delay ...

  18. European Pulsar Timing Array Limits on Continuous Gravitational Waves from Individual Supermassive Black Hole Binaries

    CERN Document Server

    Babak, Stanislav; Sesana, Alberto; Brem, Patrick; Rosado, Pablo A; Taylor, Stephen R; Lassus, Antoine; Hessels, Jason W T; Bassa, Cees G; Burgay, Marta; Caballero, R Nicolas; Champion, David J; Cognard, Ismael; Desvignes, Gregory; Gair, Jonathan R; Guillemot, Lucas; Janssen, Gemma H; Karuppusamy, Ramesh; Kramer, Michael; Lazarus, Patrick; Lee, K J; Lentati, Lindley; Liu, Kuo; Mingarelli, Chiara M F; Oslowsky, Stefan; Perrodin, Delphine; Possenti, Andrea; Purver, Mark B; Sanidas, Sotiris; Smits, Roy; Stappers, Ben; Theureau, Gilles; Tiburzi, Caterina; van Haasteren, Rutger; Vecchio, Alberto; Verbiest, Joris P W

    2015-01-01

    We have searched for continuous gravitational wave (CGW) signals produced by individually resolvable, circular supermassive black hole binaries (SMBHBs) in the latest EPTA dataset, which consists of ultra-precise timing data on 41 millisecond pulsars. We develop frequentist and Bayesian detection algorithms to search both for monochromatic and frequency-evolving systems. None of the adopted algorithms show evidence for the presence of such a CGW signal, indicating that the data are best described by pulsar and radiometer noise only. Depending on the adopted detection algorithm, the 95\\% upper limit on the sky-averaged strain amplitude lies in the range $6\\times 10^{-15}10^9$M$_\\odot$ out to a distance of about 25Mpc, and with $\\cal{M}_c>10^{10}$M$_\\odot$ out to a distance of about 1Gpc ($z\\approx0.2$). We show that state-of-the-art SMBHB population models predict $<1\\%$ probability of detecting a CGW with the current EPTA dataset, consistent with the reported non-detection. We stress, however, that PTA lim...

  19. A characteristic observable signature of preferred frame effects in relativistic binary pulsars

    CERN Document Server

    Wex, N

    2007-01-01

    In this paper we develop a consistent, phenomenological methodology to measure preferred-frame effects (PFEs) in binary pulsars that exhibit a high rate of periastron advance. We show that in these systems the existence of a preferred frame for gravity leads to an observable characteristic `signature' in the timing data, which uniquely identifies this effect. We expand the standard Damour-Deruelle timing formula to incorporate this `signature' and show how this new PFE timing model can be used to either measure or constrain the parameters related to a violation of the local Lorentz invariance of gravity in the strong internal fields of neutron stars. In particular, we demonstrate that in the presence of PFEs we expect a set of the new timing parameters to have a unique relationship that can be measured and tested incontrovertibly. This new methodology is applied to the Double Pulsar, which turns out to be the ideal test system for this kind of experiments.The currently available dataset allows us only to stud...

  20. BeppoSAX observation of the X-ray binary pulsar Vela X-1

    CERN Document Server

    Orlandini, M; Nicastro, L; Giarrusso, S; Segreto, A; Piraino, S; Cusumano, G; Del Sordo, S; Guainazzi, M; Piro, L

    1997-01-01

    We report on the spectral (pulse averaged) and timing analysis of the ~ 20 ksec observation of the X-ray binary pulsar Vela X-1 performed during the BeppoSAX Science Verification Phase. The source was observed in two different intensity states: the low state is probably due to an erratic intensity dip and shows a decrease of a factor ~ 2 in intensity, and a factor 10 in Nh. We have not been able to fit the 2-100 keV continuum spectrum with the standard (for an X--ray pulsar) power law modified by a high energy cutoff because of the flattening of the spectrum in ~ 10-30 keV. The timing analysis confirms previous results: the pulse profile changes from a five-peak structure for energies less than 15 keV, to a simpler two-peak shape at higher energies. The Fourier analysis shows a very complex harmonic component: up to 23 harmonics are clearly visible in the power spectrum, with a dominant first harmonic for low energy data, and a second one as the more prominent for energies greater than 15 keV. The aperiodic c...

  1. High-Energy $\\gamma$-Ray Observations of Two Young, Energetic Radio Pulsars

    CERN Document Server

    Kaspi, V M; Mattox, J R; Manchester, R N; Bailes, M; Pace, R

    1999-01-01

    We present results of Compton Gamma-Ray Observatory EGRET observations of the unidentified high-energy gamma-ray sources 2EG J1049-5847 (GEV J1047-5840, 3EG J1048-5840) and 2EG J1103-6106 (3EG J1102-6103). These sources are spatially coincident with the young, energetic radio pulsars PSRs B1046-58 and J1105-6107, respectively. We find evidence for an association between PSR B1046-58 and 2EG J1049-5847. The gamma-ray pulse profile, obtained by folding time-tagged photons having energies above 400 MeV using contemporaneous radio ephemerides, has probability of arising by chance of 1.2E-4 according to the binning-independent H-test. A spatial analysis of the on-pulse photons reveals a point source of equivalent significance 10.2 sigma. Off-pulse, the significance drops to 5.8 sigma. Archival ASCA data show that the only hard X-ray point source in the 95% confidence error box of the gamma-ray source is spatially coincident with the pulsar within the 1' uncertainty (Pivovaroff, Kaspi & Gotthelf 1999). The doub...

  2. Probing dense matter in compact star cores with radio pulsar data

    CERN Document Server

    Alford, Mark G

    2014-01-01

    Astrophysical observations of compact stars provide, in addition to collider experiments, the other big source of information on matter under extreme conditions. The largest and most precise data set about neutron stars is the timing data of radio pulsars. We show how this unique data can be used to learn about the ultra-dense matter in the compact star interior. The method relies on astro-seismology based on special global oscillation modes (r-modes) that emit gravitational waves. They would prevent pulsars from spinning with their observed high frequencies, unless the damping of these modes, determined by the microscopic properties of matter, can prevent this. We show that for each form of matter there is a distinct region in a frequency/spindown-rate diagram where r-modes can be present. We find that stars containing ungapped quark matter are consistent with both the observed radio and x-ray data, whereas, even when taking into account the considerable uncertainties, neutron star models with standard visco...

  3. A model for distortions of polarisation-angle curves in radio pulsars

    CERN Document Server

    Dyks, J; Oslowski, S; Saha, L; Guillemot, L; Cognard, I; Rudak, B

    2016-01-01

    Some radio pulsar profiles (in particular those of millisecond pulsars contain wide emission structures which cover large intervals of pulse phase. Local distortions of an average curve of polarisation angle (PA) can be identified in such profiles, and they are often found to be associated with absorption features or narrow emission components. The features may be interpreted as a convolution of a lateral profile of an emitter with a microscopic radiation pattern of a non-negligible angular extent. We study a model which assumes that such an extended microbeam of the X-mode curvature radiation is spreading the radiation polarised at a fixed position angle within an interval of pulse phase. The model is capable of interpreting the strongly dissimilar polarisation of double notches in PSR B1821-24A (for which we present new polarisation data from the Nancay Radio Telescope) and PSR J0437-4715. It also explains a step-like change in PA observed at the bifurcated trailing component in the profile of J0437-4715. A...

  4. PSR J1738+0333: The First Millisecond Pulsar + Pulsating White Dwarf Binary

    CERN Document Server

    Kilic, Mukremin; Gianninas, A; Brown, Warren R

    2014-01-01

    We report the discovery of the first millisecond pulsar with a pulsating white dwarf companion. Following the recent discoveries of pulsations in extremely low-mass (ELM, <0.3 Msol) white dwarfs (WDs), we targeted ELM WD companions to two millisecond pulsars with high-speed Gemini photometry. We find significant optical variability in PSR J1738+0333 with periods between roughly 1790-3060 s, consistent in timescale with theoretical and empirical observations of pulsations in 0.17 Msol He-core ELM WDs. We additionally put stringent limits on a lack of variability in PSR J1909-3744, showing this ELM WD is not variable to <0.1 per cent amplitude. Thanks to the accurate distance and radius estimates from radio timing measurements, PSR J1738+0333 becomes a benchmark for low-mass, pulsating WDs. Future, more extensive time-series photometry of this system offers an unprecedented opportunity to constrain the physical parameters (including the cooling age) and interior structure of this ELM WD, and in turn, the ...

  5. Space Radio Astronomy in the next 1000001 (binary) years

    CERN Document Server

    Gurvits, L I

    2012-01-01

    Radio astronomy and active exploration of space are peers: both began by efforts of enthusiasts in the 1930s and got a major technological boost in the 1940s-50s. Thus, for the sake of a brief review at this very special conference, it is fair to estimate the present age of these human endeavours as 1000001 (binary) years. These years saw a lot of challenging and fruitful concerted efforts by radio astronomers and space explorers. Among the high points one can mention several highly successful space-borne CMB observatories, three orbital VLBI missions, the first examples of radio observations at spectral windows hitherto closed for Earth-based observers and many yet to be implemented initiatives which are at various stages of their paths toward launch-pads of all major world space agencies. In this review I will give a bird-eye picture of the past achievements of space-oriented radio astronomy and zoom into several projects and ideas that will further push the presence of radio astronomy into the space agenda...

  6. A 350-MHz GBT Survey of 50 Faint Fermi Gamma-ray Sources for Radio Millisecond Pulsars

    CERN Document Server

    Hessels, Jason W T; McLaughlin, Maura A; Ray, Paul S; Bangale, Priyadarshini; Ransom, Scott M; Kerr, Matthew; Camilo, Fernando; DeCesar, Megan E

    2015-01-01

    We have used the Green Bank Telescope at 350MHz to search 50 faint, unidentified Fermi Gamma-ray sources for radio pulsations. So far, these searches have resulted in the discovery of 10 millisecond pulsars, which are plausible counterparts to these unidentified Fermi sources. Here we briefly describe this survey and the characteristics of the newly discovered MSPs.

  7. Discovery of the Millisecond Pulsar PSR J2043+1711 in a Fermi Source with the Nancay Radio Telescope

    Science.gov (United States)

    Guillemot, L.; Freire, P. C. C.; Cognard, I.; Johnson, T. J.; Takahashi, Y.; Kataoka, J.; Desvignes, G.; Camilo, F.; Ferrara, E. C.; Harding, A. K.; Janssen, G. H.; Keith, M.; Kerr, M.; Kramer, M.; Parent, D.; Ransom, S. M.; Ray, P. S.; Saz Parkinson, P. M.; Smith, D. A.; Stappers, W.; Theureau, G.

    2012-01-01

    We report the discovery of the millisecond pulsar PSR J2043+1711 in a search of a Fermi Large Area Telescope (LAT) source with no known associations, with the Nancay Radio Telescope. The new pulsar, confirmed with the Green Bank Telescope, has a spin period of 2.38 ms, is relatively nearby (d approx. < 2 kpc) and is in a 1.48-d orbit around a low-mass companion, probably an He-type white dwarf. Using an ephemeris based on Arecibo, Nancay and Westerbork timing measurements, pulsed gamma-ray emission was detected in the data recorded by the Fermi LAT. The gamma-ray light curve and spectral properties are typical of other gamma-ray millisecond pulsars seen with Fermi. X-ray observations of the pulsar with Suzaku and the Swift X-ray Telescope yielded no detection. At 1.4 GHz, we observe strong flux density variations because of interstellar diffractive scintillation; however, a sharp peak can be observed at this frequency during bright scintillation states. At 327 MHz, the pulsar is detected with a much higher signal-to-noise ratio and its flux density is far more steady. However, at that frequency the Arecibo instrumentation cannot yet fully resolve the pulse profile. Despite that, our pulse time-of-arrival measurements have a post-fit residual rms of 2 micro s. This and the expected stability of this system have made PSR J2043+1711 one of the first new Fermi-selected millisecond pulsars to be added to pulsar gravitational wave timing arrays. It has also allowed a significant measurement of relativistic delays in the times of arrival of the pulses due to the curvature of space-time near the companion, but not yet with enough precision to derive useful masses for the pulsar and the companion. Nevertheless, a mass for the pulsar between 1.7 and 2.0 solar Mass can be derived if a standard millisecond pulsar formation model is assumed. In this paper, we also present a comprehensive summary of pulsar searches in Fermi LAT sources with the Nancay Radio Telescope to date.

  8. A radio-pulsing white dwarf binary star

    Science.gov (United States)

    Marsh, T. R.; Gänsicke, B. T.; Hümmerich, S.; Hambsch, F.-J.; Bernhard, K.; Lloyd, C.; Breedt, E.; Stanway, E. R.; Steeghs, D. T.; Parsons, S. G.; Toloza, O.; Schreiber, M. R.; Jonker, P. G.; van Roestel, J.; Kupfer, T.; Pala, A. F.; Dhillon, V. S.; Hardy, L. K.; Littlefair, S. P.; Aungwerojwit, A.; Arjyotha, S.; Koester, D.; Bochinski, J. J.; Haswell, C. A.; Frank, P.; Wheatley, P. J.

    2016-09-01

    White dwarfs are compact stars, similar in size to Earth but approximately 200,000 times more massive. Isolated white dwarfs emit most of their power from ultraviolet to near-infrared wavelengths, but when in close orbits with less dense stars, white dwarfs can strip material from their companions and the resulting mass transfer can generate atomic line and X-ray emission, as well as near- and mid-infrared radiation if the white dwarf is magnetic. However, even in binaries, white dwarfs are rarely detected at far-infrared or radio frequencies. Here we report the discovery of a white dwarf/cool star binary that emits from X-ray to radio wavelengths. The star, AR Scorpii (henceforth AR Sco), was classified in the early 1970s as a δ-Scuti star, a common variety of periodic variable star. Our observations reveal instead a 3.56-hour period close binary, pulsing in brightness on a period of 1.97 minutes. The pulses are so intense that AR Sco’s optical flux can increase by a factor of four within 30 seconds, and they are also detectable at radio frequencies. They reflect the spin of a magnetic white dwarf, which we find to be slowing down on a 107-year timescale. The spin-down power is an order of magnitude larger than that seen in electromagnetic radiation, which, together with an absence of obvious signs of accretion, suggests that AR Sco is primarily spin-powered. Although the pulsations are driven by the white dwarf’s spin, they mainly originate from the cool star. AR Sco’s broadband spectrum is characteristic of synchrotron radiation, requiring relativistic electrons. These must either originate from near the white dwarf or be generated in situ at the M star through direct interaction with the white dwarf’s magnetosphere.

  9. NuSTAR observations of the state transition of millisecond pulsar binary PSR J1023+0038

    Energy Technology Data Exchange (ETDEWEB)

    Tendulkar, Shriharsh P.; Bellm, Eric; Harrison, Fiona A. [California Institute of Technology, 1200 E California Blvd, MC 249-17, Pasadena, CA 91125 (United States); Yang, Chengwei; An, Hongjun; Kaspi, Victoria M. [Department of Physics, McGill University, 3600 University St, Montreal, QC H3A 2T8 (Canada); Archibald, Anne M.; Bassa, Cees; Hessels, Jason W. T.; Janssen, Gemma H. [ASTRON, The Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA, Dwingeloo (Netherlands); Bogdanov, Slavko [Columbia Astrophysics Laboratory, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Lyne, Andrew G.; Stappers, Benjamin [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester, Manchester M13 9PL (United Kingdom); Patruno, Alessandro [Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden (Netherlands); Stern, Daniel [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Tomsick, John A.; Boggs, Steven E.; Craig, William W. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Chakrabarty, Deepto [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 70 Vassar Street, Cambridge, MA 02139 (United States); Christensen, Finn E., E-mail: spt@astro.caltech.edu [DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark); and others

    2014-08-20

    We report NuSTAR observations of the millisecond pulsar-low-mass X-ray binary (LMXB) transition system PSR J1023+0038 from 2013 June and October, before and after the formation of an accretion disk around the neutron star. Between June 10 and 12, a few days to two weeks before the radio disappearance of the pulsar, the 3-79 keV X-ray spectrum was well fit by a simple power law with a photon index of Γ=1.17{sub −0.07}{sup +0.08} (at 90% confidence) with a 3-79 keV luminosity of 7.4 ± 0.4 × 10{sup 32} erg s{sup –1}. Significant orbital modulation was observed with a modulation fraction of 36% ± 10%. During the October 19-21 observation, the spectrum is described by a softer power law (Γ=1.66{sub −0.05}{sup +0.06}) with an average luminosity of 5.8 ± 0.2 × 10{sup 33} erg s{sup –1} and a peak luminosity of ≈1.2 × 10{sup 34} erg s{sup –1} observed during a flare. No significant orbital modulation was detected. The spectral observations are consistent with previous and current multiwavelength observations and show the hard X-ray power law extending to 79 keV without a spectral break. Sharp-edged, flat-bottomed dips are observed with widths between 30 and 1000 s and ingress and egress timescales of 30-60 s. No change in hardness ratio was observed during the dips. Consecutive dip separations are log-normal in distribution with a typical separation of approximately 400 s. These dips are distinct from dipping activity observed in LMXBs. We compare and contrast these dips to observations of dips and state changes in the similar transition systems PSR J1824–2452I and XSS J1227.0–4859 and discuss possible interpretations based on the transitions in the inner disk.

  10. A Search for Very High-Energy Gamma Rays from the Missing Link Binary Pulsar J1023+0038 with VERITAS

    CERN Document Server

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

    2016-01-01

    The binary millisecond radio pulsar PSR J1023+0038 exhibits many characteristics similar to the gamma-ray binary system PSR B1259--63/LS 2883, making it an ideal candidate for the study of high-energy non-thermal emission. It has been the subject of multi-wavelength campaigns following the disappearance of the pulsed radio emission in 2013 June, which revealed the appearance of an accretion disk around the neutron star. We present the results of very high-energy gamma-ray observations carried out by VERITAS before and after this change of state. Searches for steady and pulsed emission of both data sets yield no significant gamma-ray signal above 100 GeV, and upper limits are given for both a steady and pulsed gamma-ray flux. These upper limits are used to constrain the magnetic field strength in the shock region of the PSR J1023+0038 system. Assuming that very high-energy gamma rays are produced via an inverse-Compton mechanism in the shock region, we constrain the shock magnetic field to be greater than $\\si...

  11. Radio polarization characteristics of two RS CVn binaries

    Science.gov (United States)

    Mutel, R. L.; Lestrade, J.-F.; Doiron, D. J.

    1985-07-01

    The authors report the results of multifrequency epoch VLA observations of polarized radio emission from the nearby active RS CVn binaries UX Arietis and HR 1099. For both systems, there is an excellent correlation between handedness of circular polarization and frequency. Helicity reversal is almost always seen between 1.4 and 5.0 GHz, possibly due to optical depth effects. There may also be an anticorrelation between total intensity and fractional circular polarization, especially at 5 GHz. This is consistent with models in which intense flares are associated with compact self-absorbed synchrotron sources, while the quiescent emission arises from larger gyrosynchrotron-emitting plasma.

  12. Challenging the Presence of Scalar Charge and Dipolar Radiation in Binary Pulsars

    CERN Document Server

    Yagi, Kent; Yunes, Nicolas

    2016-01-01

    Corrections to general relativity that introduce long-ranged scalar fields which are non-minimally coupled to curvature typically predict that neutron stars possess a non-trivial scalar field profile. An observer far from a star is most sensitive to the spherically-symmetric piece of this profile that decays linearly with the inverse of the distance, the so-called scalar charge, which is related to the emission of dipolar radiation from compact binaries. The presence of dipolar radiation has the potential to very strongly constrain extended theories of gravity. These facts may lead people to believe that gravitational theories with long-ranged scalar fields have already been constrained strongly from binary pulsar observations. Here we challenge this "lore" by investigating the decoupling limit of Gauss-Bonnet gravity as an example, in which the scalar field couples linearly to the Gauss-Bonnet density in the action. We prove a theorem that neutron stars in this theory cannot possess a scalar charge. Thus Gau...

  13. PSR J1907+0602: A Radio-Faint Gamma-Ray Pulsar Powering a Bright TeV Pulsar Wind Nebula

    CERN Document Server

    Abdo, A A

    2010-01-01

    We present multiwavelength studies of the 106.6 ms gamma-ray pulsar PSR J1907+06 near the TeV source MGRO J1908+06. Timing observations with Fermi result in a precise position determination for the pulsar of R.A. = 19h07m547(2), decl. = +06:02:16(2) placing the pulsar firmly within the TeV source extent, suggesting the TeV source is the pulsar wind nebula of PSR J1907+0602. Pulsed gamma-ray emission is clearly visible at energies from 100 MeV to above 10 GeV. The phase-averaged power-law index in the energy range E > 0.1 GeV is = 1.76 \\pm 0.05 with an exponential cutoff energy E_{c} = 3.6 \\pm 0.5 GeV. We present the energy-dependent gamma-ray pulsed light curve as well as limits on off-pulse emission associated with the TeV source. We also report the detection of very faint (flux density of ~3.4 microJy) radio pulsations with the Arecibo telescope at 1.5 GHz having a dispersion measure DM = 82.1 \\pm 1.1 cm^{-3}pc. This indicates a distance of 3.2 \\pm 0.6 kpc and a pseudo-luminosity of L_{1400} ~ 0.035 mJy kpc...

  14. Contrasting behaviour from two Be/X-ray binary pulsars: insights into differing neutron star accretion modes

    CERN Document Server

    Townsend, L J; Hill, A B; Coe, M J; Corbet, R H D; Bird, A J

    2013-01-01

    In this paper we present the identification of two periodic X-ray signals coming from the direction of the Small Magellanic Cloud (SMC). On detection with the Rossi X-ray Timing Explorer (RXTE), the 175.4s and 85.4s pulsations were considered to originate from new Be/X-ray binary (BeXRB) pulsars with unknown locations. Using rapid follow-up INTEGRAL and XMM-Newton observations, we show the first pulsar (designated SXP175) to be coincident with a candidate high-mass X-ray binary (HMXB) in the northern bar region of the SMC undergoing a small Type II outburst. The orbital period (87d) and spectral class (B0-B0.5IIIe) of this system are determined and presented here for the first time. The second pulsar is shown not to be new at all, but is consistent with being SXP91.1 - a pulsar discovered at the very beginning of the 13 year long RXTE key monitoring programme of the SMC. Whilst it is theoretically possible for accreting neutron stars to change spin period so dramatically over such a short time, the X-ray and ...

  15. Contrasting Behaviour from Two Be/X-ray Binary Pulsars: Insights into Differing Neutron Star Accretion Modes

    Science.gov (United States)

    Townsend, L. J.; Drave, S. P.; Hill, A. B.; Coe, M. J.; Corbet, R. H. D.; Bird, A. J.

    2013-01-01

    In this paper we present the identification of two periodic X-ray signals coming from the direction of the Small Magellanic Cloud (SMC). On detection with the Rossi X-ray Timing Explorer (RXTE), the 175.4 s and 85.4 s pulsations were considered to originate from new Be/X-ray binary (BeXRB) pulsars with unknown locations. Using rapid follow-up INTEGRAL and XMM-Newton observations, we show the first pulsar (designated SXP175) to be coincident with a candidate high-mass X-ray binary (HMXB) in the northern bar region of the SMC undergoing a small Type II outburst. The orbital period (87d) and spectral class (B0-B0.5IIIe) of this system are determined and presented here for the first time. The second pulsar is shown not to be new at all, but is consistent with being SXP91.1 - a pulsar discovered at the very beginning of the 13 year long RXTE key monitoring programme of the SMC. Whilst it is theoretically possible for accreting neutron stars to change spin period so dramatically over such a short time, the X-ray and optical data available for this source suggest this spin-up is continuous during long phases of X-ray quiescence, where accretion driven spin-up of the neutron star should be minimal.

  16. High energy emission from the nebula around the Black Widow binary system containing millisecond pulsar B1957+20

    CERN Document Server

    Bednarek, W

    2013-01-01

    The features of pulsed $\\gamma$-ray emission from classical and millisecond pulsars indicate that the high energy radiation processes in their inner magnetospheres occur in a similar way. In the last decade several TeV $\\gamma$-ray nebulae have been discovered around classical pulsars. The above facts suggest that $\\gamma$-rays should be produced also in the surroundings of millisecond pulsars. We discuss a model for the bow shock nebula around the well known Black Widow binary system containing the millisecond pulsar B1957+20. This model predicts the existence of a synchrotron X-ray and inverse Compton $\\gamma$-ray nebula around this system. We want to find out whether $\\gamma$-ray emission from the nebula around B1957+20 could be detected by the future and present Cherenkov telescopes. Using the Monte Carlo method we followed the propagation of relativistic electrons in the vicinity of the pulsar. We calculated the very high energy radiation produced by them in the synchrotron process and the inverse Compto...

  17. The Identification of the Optical Companion to the Binary Millisecond Pulsar J0610-2100 in the Galactic Field

    Science.gov (United States)

    Pallanca, C.; Mignani, R. P.; Dalessandro, E.; Ferraro, F. R.; Lanzoni, B.; Possenti, A.; Burgay, M.; Sabbi, E.

    2012-08-01

    We have used deep V and R images acquired at the ESO Very Large Telescope to identify the optical companion to the binary PSR J0610-2100, one of the black-widow millisecond pulsars recently detected by the Fermi Gamma-ray Space Telescope in the Galactic plane. We found a faint star (V ~ 26.7) nearly coincident (δr ~ 0farcs28) with the pulsar nominal position. This star is visible only in half of the available images, while it disappears in the deepest ones (those acquired under the best-seeing conditions), thus indicating that it is variable. Although our observations do not sample the entire orbital period (P = 0.28 days) of the pulsar, we found that the optical modulation of the variable star nicely correlates with the pulsar orbital period and describes a well-defined peak (R ~ 25.6) at Φ = 0.75, suggesting a modulation due to the pulsar heating. We tentatively conclude that the companion to PSR J0610-2100 is a heavily ablated very low mass star (≈0.02 M ⊙) that completely filled its Roche lobe.

  18. Nature of eclipsing pulsars

    CERN Document Server

    Khechinashvili, D; Gil, J; Khechinashvili, David; Melikidze, George; Gil, Janusz

    2000-01-01

    We present a model for pulsar radio eclipses in some binary systems, and test this model for PSRs B1957+20 and J2051-0827. We suggest that in these binaries the companion stars are degenerate dwarfs with strong surface magnetic fields. The magnetospheres of these stars are permanently infused by the relativistic particles of the pulsar wind. We argue that the radio waves emitted by the pulsar split into the eigenmodes of the electron-positron plasma as they enter the companion's magnetosphere and are then strongly damped due to cyclotron resonance with the ambient plasma particles. Our model explains in a natural way the anomalous duration and behavior of radio eclipses observed in such systems. In particular, it provides stable, continuous, and frequency-dependent eclipses, in agreement with the observations. We predict a significant variation of linear polarization both at eclipse ingress and egress. In this paper we also suggest several possible mechanisms of generation of the optical and $X$-ray emission ...

  19. Radio observations of the TeV source HESS J1943+213: a new case of a pulsar wind nebula?

    CERN Document Server

    Gabanyi, K E; Giacani, E; Paragi, Z; Pidopryhora, Y; Frey, S

    2011-01-01

    Recently, the H.E.S.S. Collaboration discovered a very high energy gamma-ray point source close to the Galactic plane. They offered three possible explanations for the nature of the source: a gamma-ray binary, a pulsar wind nebula, or a BL Lac object. They concluded that the observations favoured an extreme BL Lac object interpretation. We investigated the nature of the radio source reported as the counterpart of the very high energy gamma-ray source. We performed high-resolution radio interferometric observations with the European Very Long Baseline Interferometry Network at a frequency of 1.6 GHz on 2011 May 18. We also reanalysed archival 1.4-GHz radio continuum and HI spectral line data taken with the Very Large Array. The accurate position of the radio source, as observed with EVN, is ~ 4" off from the one obtained in the NRAO VLA Sky Survey. The new position is in excellent agreement with that of the proposed X-ray counterpart of the TeV source. From HI absorption data, a distance of about 11.5 +/- 1.5 ...

  20. Millisecond and Binary Pulsars as Nature's Frequency Standards; 2, Effects of Low-Frequency Timing Noise on Residuals and Measured Parameters

    CERN Document Server

    Kopeikin, S M

    1998-01-01

    Pulsars are the most stable natural frequency standards. They can be applied to a number of principal problems of modern astronomy and time-keeping metrology. The full exploration of pulsar properties requires obtaining unbiased estimates of the spin and orbital parameters. These estimates depend essentially on the random noise component being revealed in the residuals of time of arrivals (TOA). In the present paper, the influence of low-frequency ("red") timing noise with spectral indices from 1 to 6 on TOA residuals, variances, and covariances of estimates of measured parameters of single and binary pulsars are studied. In order to determine their functional dependence on time, an analytic technique of processing of observational data in time domain is developed which takes into account both stationary and non-stationary components of noise. Our analysis includes a simplified timing model of a binary pulsar in a circular orbit and procedure of estimation of pulsar parameters and residuals under the influenc...

  1. On the power spectra of the wind-fed X-ray binary pulsar GX 301 - 2

    Science.gov (United States)

    Orlandini, Mauro; Morfill, G. E.

    1992-01-01

    A phenomenological model of accretion which is applied to the wind-fed X-ray binary pulsar GX 301 - 2 is developed, assuming that the accretion onto the neutron star does not occur from a continuous flux of plasma, but from blobs of matter which are threaded by the magnetic field lines onto the magnetic polar caps of the neutron star. These 'lumps' are produced at the magnetospheric limit by magnetohydrodynamical instability, introducing a 'noise' in the accretion process, due to the discontinuity in the flux of matter onto the neutron star. This model is able to describe the change of slope observed in the continuum component of the power spectra of the X-ray binary pulsar GX 301 - 2, in the frequency range 0.01 - 0.1 Hz. The physical properties of the infalling blobs derived in the model are in agreement with the constraints imposed by observations.

  2. The formation of low-mass helium white dwarfs orbiting pulsars: Evolution of low-mass X-ray binaries below the bifurcation period

    CERN Document Server

    Istrate, Alina; Langer, Norbert

    2014-01-01

    Millisecond pulsars (MSPs) are generally believed to be old neutron stars (NSs) which have been spun up to high rotation rates via accretion of matter from a companion star in a low-mass X-ray binary (LMXB). However, many details of this recycling scenario remain to be understood. Here we investigate binary evolution in close LMXBs to study the formation of radio MSPs with low-mass helium white dwarf companions (He WDs) in tight binaries with orbital periods P_orb = 2-9 hr. In particular, we examine: i) if such observed systems can be reproduced from theoretical modelling using standard prescriptions of orbital angular momentum losses (i.e. with respect to the nature and the strength of magnetic braking), ii) if our computations of the Roche-lobe detachments can match the observed orbital periods, and iii) if the correlation between WD mass and orbital period (M_WD, P_orb) is valid for systems with P_orb < 2 days. Numerical calculations with a detailed stellar evolution code were used to trace the mass-tra...

  3. VARIABILITY OF THE PULSED RADIO EMISSION FROM THE LARGE MAGELLANIC CLOUD PULSAR PSR J0529-6652

    Energy Technology Data Exchange (ETDEWEB)

    Crawford, F.; Altemose, D.; Li, H. [Department of Physics and Astronomy, Franklin and Marshall College, P.O. Box 3003, Lancaster, PA 17604 (United States); Lorimer, D. R. [Department of Physics, West Virginia University, Morgantown, WV 26506 (United States)

    2013-01-10

    We have studied the variability of PSR J0529-6652, a radio pulsar in the Large Magellanic Cloud (LMC), using observations conducted at 1390 MHz with the Parkes 64 m telescope. PSR J0529-6652 is detectable as a single pulse emitter, with amplitudes that classify the pulses as giant pulses. This makes PSR J0529-6652 the second known giant pulse emitter in the LMC, after PSR B0540-69. The fraction of the emitted pulses detectable from PSR J0529-6652 at this frequency is roughly two orders of magnitude greater than it is for either PSR B0540-69 or the Crab pulsar (if the latter were located in the LMC). We have measured a pulse nulling fraction of 83.3% {+-} 1.5% and an intrinsic modulation index of 4.07 {+-} 0.29 for PSR J0529-6652. The modulation index is significantly larger than values previously measured for typical radio pulsars but is comparable to values reported for members of several other neutron star classes. The large modulation index, giant pulses, and large nulling fraction suggest that this pulsar is phenomenologically more similar to these other, more variable sources, despite having spin and physical characteristics that are typical of the unrecycled radio pulsar population. The large modulation index also does not appear to be consistent with the small value predicted for this pulsar by a model of polar cap emission outlined by Gil and Sendyk. This conclusion depends to some extent on the assumption that PSR J0529-6652 is exhibiting core emission, as suggested by its simple profile morphology, narrow profile width, and previously measured profile polarization characteristics.

  4. Radio Phase-Resolved Spectra of the Conal-Double Pulsar B1133+16

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Based on dividing the profile into a number of absolute phase intervals, the phase-resolved spectra (PHRS) are derived from published time-aligned average profiles at radio frequencies over two decades for the classic conal-double pulsar B1133+16. The relative spectral index, defined as the difference between the spectral indices of a reference and the given arbitrary phase interval, is obtained by power-law fit at each phase interval. The derived phase-resolved spectra show an "M-like" shape, of which the leading part and trailing part are approximately symmetrical. The basic feature of the PHRS is that the spectrum first flattens then steepens as the pulse phase sweeps from the profile center to the profile edges. The PHRS provide a coherent explanation of the major features of profile evolution of B1133+16, namely, the pulse width shrinkage with increasing frequency and the frequency evolution of the relative intensity between the leading and trailing conal components, and the bridge emission. The PHRS may be an indicator for emission spectral variation across the pulsar magnetosphere. Possible mapping from PHRS to emission-location-dependent spectral variation is presented, and some intrinsic mechanisms are discussed.

  5. Location of the emitting regions in the mode-switching radio pulsar PSR 1926 + 18

    Science.gov (United States)

    Nowakowski, L. A.

    1994-01-01

    We present an analysis of average single-frequency profiles of the radio pulsar PSR 1926 + 18 in two different modes. Assuming a purely dipolar field and taking into account retardation, aberration, magnetic line curvature, and ignoring the magnetic field line sweepback, we come to the following conclusions: (1) mode switching in PSR 1926 + 18 at 430 MHz may be understood in terms of different emission heights of the two modes; (2) the weaker mode appears when regions emitting the first two components move away from the star by an additional distance of not more than several kilometers from their original locations; (3) the trailing conal component is emitted essentially from the same layer of the magnetosphere in both modes, in contrast to the first conal component, which appears to change its location in the magnetosphere; (4) core and conal components are emitted from distinctly different emission heights: core components not more than 75 km, and conal components not less than 215 km from the surface of the star. Our model infers three-dimensional information about the emitting region from single-frequency observations. It has been tested previously with a mode switching pulsar that had one component in the average profile in two modes. This paper shows that the same model can explain positions and widths of the components in a more complex profile during mode switching, provided that the components can be traced from one mode to another.

  6. Low Frequency Radio Emission of Pulsar PSR J1907+0919 Associated with the Magnetar SGR 1900+14

    CERN Document Server

    Shitov, Yu P; Kutuzov, S M; Shitov, Yu. P.

    2000-01-01

    The soft gamma repeater SGR 1900+14 was observed in Pushchino observatorysince 1988 December using BSA radio telescope operating at 111 MHz. We havedetected the pulsed radio emission (Shitov 1999) with the same 5.16 s periodthat was reported earlier for this object. The timing analysis has shown thatthis new radio pulsar PSR J1907+0919 associated with SGR 1900+14 has asuperstrong magnetic field, which is 8.1 * 10^14 G, thereby confirming that itis a "magnetar". The dispersion measure of PSR J1907+0919 is 281.4(9) pc *cm^(-3) which gives an estimate of the pulsar's distance as about 5.8 kpc.

  7. Multifrequency radio observations of SNR J0536-6735 (N 59B) with associated pulsar

    CERN Document Server

    Bozzetto, L M; Crawford, E J; De Horta, A Y; Stupar, M

    2012-01-01

    We present a study of new Australian Telescope Compact Array (ATCA) observations of supernova remnant, SNR J0536-6735. This remnant appears to follow a shell morphology with a diameter of D=36x29 pc (with 1 pc uncertainty in each direction). There is an embedded Hii region on the northern limb of the remnant which made various analysis and measurements (such as flux density, spectral index and polarisation) difficult. The radio-continuum emission followed the same structure as the optical emission, allowing for extent and flux density estimates at 20 cm. We estimate a surface brightness for the SNR at 1 GHz of 2.55x10^-21 W m^-2 Hz^-1 sr^-1. Also, we detect a distinctive radio-continuum point source which confirms the previous suggestion of this remnant being associated with a pulsar wind nebulae (PWN). The tail of this remnant isn't seen in the radio-continuum images and is only seen in the optical and X-ray images.

  8. The Green Bank Telescope 350 MHz Drift-scan Survey II: Data Analysis and the Timing of 10 New Pulsars, Including a Relativistic Binary

    CERN Document Server

    Lynch, Ryan S; Ransom, Scott M; Stairs, Ingrid H; Lorimer, Duncan R; McLaughlin, Maura A; Hessels, Jason W T; Kaspi, Victoria M; Kondratiev, Vladislav I; Archibald, Anne M; Berndsen, Aaron; Cardoso, Rogerio F; Cherry, Angus; Karako-Argaman, Chen; van Leeuwen, Joeri; McPhee, Christie A; Pennucci, Tim; Roberts, Mallory S E

    2012-01-01

    We have completed a 350 MHz drift scan survey using the Robert C. Byrd Green Bank Telescope with the goal of finding new radio pulsars, especially millisecond pulsars that can be timed to high precision. This survey covered ~10300 square degrees and all of the data have now been fully processed. We have discovered a total of 31 new pulsars, seven of which are recycled pulsars. A companion paper by Boyles et al. (2012) describes the survey strategy, sky coverage, and instrumental set-up, and presents timing solutions for the first 13 pulsars. Here we describe the data analysis pipeline, survey sensitivity, and follow-up observations of new pulsars, and present timing solutions for 10 other pulsars. We highlight several sources---two interesting nulling pulsars, an isolated millisecond pulsar with a measurement of proper motion, and a partially recycled pulsar, PSR J0348+0432, which has a white dwarf companion in a relativistic orbit. PSR J0348+0432 will enable unprecedented tests of theories of gravity.

  9. High-energy emission from the nebula around the Black Widow binary system containing millisecond pulsar B1957+20

    Science.gov (United States)

    Bednarek, W.; Sitarek, J.

    2013-02-01

    Context. The features of pulsed γ-ray emission from classical and millisecond pulsars indicate that the high energy radiation processes in their inner magnetospheres occur in a similar way. In the past decade several TeV γ-ray nebulae have been discovered around classical pulsars. The above facts suggest that γ-rays should be produced also in the surroundings of millisecond pulsars. Aims: We discuss a model for the bow shock nebula around the well known Black Widow binary system containing the millisecond pulsar B1957+20. This model predicts the existence of a synchrotron X-ray and inverse Compton γ-ray nebula around this system. We want to find out whether γ-ray emission from the nebula around B1957+20 could be detected by the future and present Cherenkov telescopes. Methods: Using the Monte Carlo method we followed the propagation of relativistic electrons in the vicinity of the pulsar. We calculated the very high energy radiation produced by them in the synchrotron process and the inverse Compton scattering of the microwave background radiation and of the infrared radiation from the galactic disk. We also computed the X-ray emission produced by the electrons in the synchrotron process. Results: We show that the hard X-ray tail emission observed from the vicinity of B1957+20 can be explained by our model. Moreover, we predict that the TeV γ-ray emission produced by the electrons in the inverse Compton process should be detectable by the future Cherenkov Telescope Array and possibly by the long term observations with the present Cherenkov arrays such as MAGIC and VERITAS. The γ-ray emission from B1957+20 is expected to be extended, inhomogeneous, and shifted from the present location of the binary system by a distance comparable to the radius of the nebula.

  10. Ain't No Crab, PWN Got A Brand New Bag: Correlated radio and X-ray Structures in Pulsar Wind Nebulae

    CERN Document Server

    Roberts, M S E; Gaensler, B M; Brogan, C L; Tam, C R; Romani, R W; Roberts, Mallory S.E.; Lyutikov, Maxim; Gaensler, Bryan M.; Brogan, Crystal; Tam, Cindy R.; Romani, Roger W.

    2004-01-01

    The traditional view of radio pulsar wind nebulae (PWN), encouraged by the Crab nebula's X-ray and radio morphologies, is that they are a result of the integrated history of their pulsars' wind. The radio emission should therefore be largely unaffected by recent pulsar activity, and hence minimally correlated with structures in the X-ray nebulae. Observations of several PWN, both stationary (sPWN) and rapidly moving (rPWN), now show clear morphological relationships between structures in the radio and X-ray with radio intensity variations on the order of unity. We present high-resolution X-ray and radio images of several PWN of both types and discuss the morphological relationships between the two wavebands.

  11. X-Ray Measurement of the Spin-down of Calvera: A Radio- and Gamma-Ray-Quiet Pulsar

    Science.gov (United States)

    Halpern, J. P.; Bogdanov, S.; Gotthelf, E. V.

    2013-12-01

    We measure spin-down of the 59 ms X-ray pulsar Calvera by comparing the XMM-Newton discovery data from 2009 with new Chandra timing observations taken in 2013. Its period derivative is \\dot{P}=(3.19+/- \\,0.08)\\times 10^{-15}, which corresponds to spin-down luminosity \\dot{E}=6.1\\times 10^{35} erg s-1, characteristic age \\tau _c\\equiv P/2\\dot{P}=2.9\\times 10^5 yr, and surface dipole magnetic field strength Bs = 4.4 × 1011 G. These values rule out a mildly recycled pulsar, but Calvera could be an orphaned central compact object (anti-magnetar), with a magnetic field that was initially buried by supernova debris and is now reemerging and approaching normal strength. We also performed unsuccessful searches for high-energy γ-rays from Calvera in both imaging and timing of >100 MeV Fermi photons. Even though the distance to Calvera is uncertain by an order of magnitude, an upper limit of d < 2 kpc inferred from X-ray spectra implies a γ-ray luminosity limit of <3.3 × 1032 erg s-1, which is less than that of any pulsar of comparable \\dot{E}. Calvera shares some properties with PSR J1740+1000, a young radio pulsar that we show by virtue of its lack of proper motion was born outside of the Galactic disk. As an energetic, high-Galactic-latitude pulsar, Calvera is unique in being undetected in both radio and γ-rays to faint limits, which should place interesting constraints on models for particle acceleration and beam patterns in pulsar magnetospheres.

  12. Gravitational radiation reaction in the binary pulsar and the quadrupole-formula controversy

    Science.gov (United States)

    Damour, T.

    1983-09-01

    The orbital motion of a binary pulsar system is investigated analytically. The two-body problem is reduced to a one-body problem, which is solved while terms of the order c to the -5th are disregarded; then the full problem is solved to the order G cubed by the variation of arbitrary constants, an aproach based on earlier work by Bel et al. (1981), Damour and Deruelle (1981), and Damour (1982, 1983). The isolated Schwarzschild mass' of each compact object is employed, rather than the integral of a Newtonian density, and the derivation does not involve quadrupole moment, energy flux at infinity, balance equations, energy, angular momentum, or radiation-damping force. No acceleration of the system center of mass is found, and the quantitative calculations of the secular decrease in the periastron-return time are shown to agree with the 'quadrupole formula' and with the secular acceleration of the orbital motion of PSR 1913+16 observed by Taylor et al. (1979).

  13. Targeting supermassive black hole binaries and gravitational wave sources for the pulsar timing array

    CERN Document Server

    Rosado, Pablo A

    2013-01-01

    This paper presents a technique to search for supermassive black hole binaries (MBHBs) in the Sloan Digital Sky Survey (SDSS). The search is based on the peculiar properties of merging galaxies that are found in a mock galaxy catalog from the Millennium Simulation. MBHBs are expected to be the main gravitational wave (GW) sources for pulsar timing arrays (PTAs); however, it is still unclear if the observed GW signal will be produced by a few single MBHBs, or if it will have the properties of a stochastic background. The goal of this work is to produce a map of the sky in which each galaxy is assigned a probability of having suffered a recent merger, and of hosting a MBHB that could be detected by PTAs. This constitutes a step forward in the understanding of the expected PTA signal: the skymap can be used to investigate the clustering properties of PTA sources and the spatial distribution of the observable GW signal power; moreover, galaxies with the highest probabilities could be used as inputs in targeted se...

  14. The optical counterpart of sax j1808.4{3658 in quiescence: evidence of an active radio pulsar?

    Directory of Open Access Journals (Sweden)

    L. Burderi

    2004-01-01

    Full Text Available La contraparte optica del pulsar binario SAX J1808.4-3658 que emite en rayos X con un per odo de milisegundos, ha sido detectada durante su estapa de quietud a V = 21.5 mag; lo cual es inconsistente con la d ebil emisi on de la estrella compa~nera. Proponemos que la emisi on en el optico de este sistema durante su etapa de quietud es debida a la irradiaci on de la estrella compa~nera y a un disco de acreci on permanente provocado por la energ a rotacional producida por el r apido giro de la estrella de neutrones que act ua como un dipolo magn etico rotante (radio pulsar. En este escenario, la compa~nera se comporta como un bol ometro, reprocesando en el optico parte de la potencia emitida por el pulsar. La fracci on reprocesada depende s olo de par ametros conocidos del sistema binario; la temperatura de cuerpo negro asociada a la estrella compa~nera puede predecirse y rati carse con observaciones. Nuestros c alculos indican que las magnitudes opticas observadas son totalmente compatibles con esta hip otesis. En el caso de que esto sea as , la luminosidad observada en el optico puede ser la primera evidencia de que hay un radio pulsar activo en este sistema en quietud.

  15. Instant Radio Spectra of Giant Pulses from the Crab Pulsar Over Decimeter to Decameter Wave Band

    Science.gov (United States)

    Popov, M. V.; Kuzmin, A. D.; Ulyanov, O. M.; Deshpande, A. A.; Ershov, A. A.; Kondratiev, V. I.; Kostyuk, S. V.; Losovsky, B. Ya.; Soglasnov, V. A.; Zakharenko, V. V.

    2006-08-01

    We present results of simultaneous multi-frequency observations of giant radio pulses (GPs) from the Crab pulsar PSR B0531+21 at frequencies of 23, 111 and 600 MHz. For the first time GPs were detected at such low frequency as 23 MHz. Among 45 GPs detected in the overall observations time with 600 MHz, 12 GPs were identified as simultaneous ones at 600 and 23 MHz. At 111 MHz among 128 GPs detected in the overall observations time with 600 MHz, 21 GPs were identified as simultaneous ones at 600 and 111 MHz. Spectral indexes for the power-law frequency dependence of GPs energy were enclosed between -3.1 and -1.6. Mean spectral index equals to -2.7 ± 0.1 and is the same for both frequency combinations 600-111 MHz and 600-23 MHz. A big scatter in values of the individual spectral indexes and a large number of unidentified giant pulses, indicate that a real form of spectra of individual giant pulses does not follow a simple power law. The shape of giant pulses at all three frequencies is governed by the scattering of radio waves on the inhomogeneities of the interstellar plasma. The pulse scatter broadening and their frequency dependence was measured as τ[SC]=20(ν/100)^-3.5^±^0.1 ms, where frequency ν is in MHz. The main results of these observations are present on the figure bellow.

  16. Dark Matter-induced Collapse of Neutron Stars: A Possible Link Between Fast Radio Bursts and the Missing Pulsar Problem

    CERN Document Server

    Fuller, Jim

    2014-01-01

    Fast radio bursts (FRBs) are an emerging class of short and bright radio transients whose sources remain enigmatic. Within the galactic center, the non-detection of pulsars within the inner $\\sim \\!10\\,{\\rm pc}$ has created a missing pulsar problem that has intensified with time. With all reserve, we advance the notion that the two problems could be linked by a common solution: the collapse of neutron stars (NS) due to capture and sedimentation of dark matter (DM) within their cores. Bramante \\& Linden (2014), Phys.\\ Rev.\\ Lett.~19, 191301 showed that certain DM properties allow for rapid NS collapse within the high DM density environments near galactic centers while permitting NS survival elsewhere. Each DM-induced collapse could generate an FRB as the NS magnetosphere is suddenly expelled. This scenario could explain several features of FRBs: their short time scales, large energies, locally produced scattering tails, and high event rates. Our scenario predicts that FRBs are localized to galactic centers...

  17. Probing the Pulsar Wind in the gamma-ray Binary System PSR B1259-63/SS 2883

    CERN Document Server

    Takata, Jumpei

    2009-01-01

    The spectral energy distribution from the X-ray to the very high energy regime ($>100$ GeV) has been investigated for the $\\gamma$-ray binary system PSR B1259-63/SS2883 as a function of orbital phase within the framework of a simple model of a pulsar wind nebula. The emission model is based on the synchrotron radiation process for the X-ray regime and the inverse Compton scattering process boosting stellar photons from the Be star companion to the very high energy (100GeV-TeV) regime. With this model, the observed temporal behavior can, in principle, be used to probe the pulsar wind properties at the shock as a function of the orbital phase. Due to theoretical uncertainties in the detailed microphysics of the acceleration process and the conversion of magnetic energy into particle kinetic energy, the observed X-ray data for the entire orbit are fit using two different methods.

  18. SKA-Japan Pulsar Science with the Square Kilometre Array

    CERN Document Server

    Takahashi, Keitaro; Iwata, Kengo; Kameya, Osamu; Kumamoto, Hiroki; Kuroyanagi, Sachiko; Mikami, Ryo; Naruko, Atsushi; Ohno, Hiroshi; Shibata, Shinpei; Terasawa, Toshio; Yonemaru, Naoyuki; Yoo, Chulmoon

    2016-01-01

    The Square Kilometre Array will revolutionize pulsar studies with its wide field-of-view, wide-band observation and high sensitivity, increasing the number of observable pulsars by more than an order of magnitude. Pulsars are of interest not only for the study of neutron stars themselves but for their usage as tools for probing fundamental physics such as general relativity, gravitational waves and nuclear interaction. In this article, we summarize the activity and interests of SKA-Japan Pulsar Science Working Group, focusing on an investigation of modified gravity theory with the supermassive black hole in the Galactic Centre, gravitational-wave detection from cosmic strings and binary supermassive black holes, a study of the physical state of plasma close to pulsars using giant radio pulses and determination of magnetic field structure of Galaxy with pulsar pairs.

  19. The Feasibility of Using Black Widow Pulsars in Pulsar Timing Arrays for Gravitational Wave Detection

    CERN Document Server

    Bochenek, Christopher; Demorest, Paul

    2015-01-01

    In the past five years, approximately one third of the 65 pulsars discovered by radio observations of Fermi unassociated sources are black widow pulsars (BWPs). BWPs are binary millisecond pulsars with companion masses ranging from 0.01-0.1 solar masses which often exhibit radio eclipses. The bloated companions in BWP systems exert small torques on the system causing the orbit to change on small but measurable time scales. Because adding parameters to a timing model reduces sensitivity to a gravitational wave (GW) signal, the need to fit many orbital frequency derivatives to the timing data is potentially problematic for using BWPs to detect GWs with pulsar timing arrays. Using simulated data with up to four orbital frequency derivatives, we show that fitting for orbital frequency derivatives absorbs less than 5% of the low frequency spectrum expected from a stochastic gravitational wave background signal. Furthermore, this result does not change with orbital period. Therefore, we suggest that if timing syste...

  20. Non-thermal emission from high-energy binaries through interferometric radio observations

    CERN Document Server

    Marcote, B

    2016-01-01

    High-mass binary systems involve extreme environments that produce non-thermal emission from radio to gamma rays. Only three types of these systems are known to emit persistent gamma-ray emission: colliding-wind binaries, high-mass X-ray binaries and gamma-ray binaries. This thesis is focused on the radio emission of high-mass binary systems through interferometric observations, and we have explored several of these sources with low- and high-frequency radio observations, and very high-resolution VLBI ones. We have studied two gamma-ray binaries, LS 5039 and LS I +61 303, at low frequencies. We have obtained their light-curves and spectra, and we have determined the physical properties of their radio emitting regions. We have also studied the gamma-ray binary HESS J0632+057 through VLBI observations. A new colliding wind binary, HD 93129A, has been discovered through VLBI and optical observations. Finally, we have conducted radio observations of two sources that were candidates to be gamma-ray binaries.

  1. Implementation of a goodness-of-fit test for finding optimal concurrent radio and {\\gamma}-ray pulsar light curves

    CERN Document Server

    Seyffert, A S; Harding, A K; Allison, J; Schutte, W D

    2016-01-01

    Since the launch of the Fermi Large Area Telescope in 2008 the number of known ${\\gamma}$-ray pulsars has increased immensely to over 200, many of which are also visible in the radio and X-ray bands. Seyffert et al. (2011) demonstrated how constraints on the viewing geometries of some of these pulsars could be obtained by comparing their observed radio and ${\\gamma}$-ray light curves by eye to light curves from geometric models. While these constraints compare reasonably well with those yielded by more rigorous single-wavelength approaches, they are still a somewhat subjective representation of how well the models reproduce the observed radio and ${\\gamma}$-ray light curves. Constructing a more rigorous approach is, however, made difficult by the large uncertainties associated with the ${\\gamma}$-ray light curves as compared to those associated with the radio light curves. Naively applying a ${\\chi}^{2}$-like goodness-of-fit test to both bands invariably results in constraints dictated by the radio light curv...

  2. 脉冲星巡天观测进展和近邻脉冲星样本估算%Progress on Radio Pulsar Survey and Estimate the Neighbor Pulsar Population

    Institute of Scientific and Technical Information of China (English)

    张蕾; 王培; 李菂; 张洁; 岳友岭; 刘姝

    2015-01-01

    射电脉冲星巡天是探测获取更多脉冲星的重要途径.首先介绍了影响射电脉冲星巡天效率的因素,着重分析灵敏度和观测频率两个重要因素,并通过定义脉冲星探测率,简化对脉冲星巡天效率的估算.此外,总结了现有脉冲星巡天项目,利用Parkes多波束脉冲星及两次扩充巡天(Swinburne中纬度脉冲星巡天和Parkes高纬度脉冲星巡天)结果,采用包含时间演化的脉冲星分布模拟软件PsrPopPy,模拟得到脉冲星在银河系中分布的样本,并对近邻太阳系1kpc距离内的脉冲星数目进行了估算,获得了近邻脉冲星样本,可为脉冲星高能辐射对探测宇宙线正电子谱影响等研究提供可靠输入量.%Radio surveys are an important way to detect new pulsars. We first reviewed the main factors affecting sensitivities of pulsar searches in radio bands. These factors can be grouped into two categories. First, the instrumental factors include telescope size, observation frequency, observation bandwidth, integration time, sampling rate, digitization loss, and system temperature. Second, the intrinsic properties of pulsars include dispersion, period, and effective pulse width. We defined a generic detection rate (DR) that combine all these factors to be the number of pulsars detected with specific integration time per pointing. We summarized the results of all radio pulsar surveys. The most successful pulsar survey so far is Parkes multibeam pulsar survey (PKSMB), which detected 1086 normal pulsars. The PKSMB was expanded by two more surveys, namely, Parkes-Swinbume multibeam survey (PKSSW) and Parkes high-latitude multibeam pulsar survey (PKSHL), which in total detected 1377 normal pulsars. We utilized the software package PsrPopPy, which adopts a time evolution model of pulsar parameters, to simulate the Galactic pulsar distribution. The results of Parkes multi-beam pulsar survey and its two extensions were used as inputs of PsrPopPy to constrain

  3. Formation of Binary Millisecond Pulsars by Accretion-Induced Collapse of White Dwarfs under Wind-Driven Evolution

    CERN Document Server

    Ablimit, Iminhaji

    2014-01-01

    Accretion-induced collapse of massive white dwarfs (WDs) has been proposed to be an important channel to form binary millisecond pulsars (MSPs). Recent investigations on thermal timescale mass transfer in WD binaries demonstrate that the resultant MSPs are likely to have relatively wide orbit periods ($\\gtrsim 10$ days). Here we calculate the evolution of WD binaries taking into account the excited wind from the companion star induced by X-ray irradiation of the accreting WD, which may drive rapid mass transfer even when the companion star is less massive than the WD. This scenario can naturally explain the formation of the strong-field neutron star in the low-mass X-ray binary 4U 1822$-$37. After AIC the mass transfer resumes when the companion star refills its Roche lobe, and the neutron star is recycled due to mass accretion. A large fraction of the binaries will evolve to become binary MSPs with a He WD companion, with the orbital periods distributed between $\\gtrsim 0.1$ day and $\\lesssim 30$ days, while...

  4. Modeling the Effect of Kick Velocity during the Accretion Induced Collapse of White Dwarfs on Binary Pulsars

    Science.gov (United States)

    Taani, Ali

    2016-07-01

    The kick velocity which arises during the binary interaction plays an important role in disruption or surviving the binary systems. This paper attempts to draw an evolutionary connection of the long-period (Porb ≥ 2 d) millisecond pulsars (MSPs) with orbits of low eccentricity (e ≤ 0.2). We propose that a kick velocity caused by dynamical effects of asymmetric collapse imparted to the companion star through an accretion induced collapse (AIC) of white dwarfs-that become unstable once they approach the Chandrasekhar limit-can account for the differences in their orbital period distributions. Furthermore, in some cases, an appropriate kick can disrupt the binary system and result in the birth of isolated MSPs. Otherwise, the binary survives and an eccentric binary MSP is formed. In this case only the binding energy equivalent (0.2M⊙) of mass is lost and the system remains intact in a symmetric collapse. Consequently, the AIC decreases the mass of the neutron star and increases the orbital period leading to orbit circularization. We present the results of our model and discuss the possible implications for the binary MSPs in galactic disk and globular clusters.

  5. A pilot ASKAP survey of radio transient events in the region around the intermittent pulsar PSR J1107-5907

    CERN Document Server

    Hobbs, G; Bell, M E; Kerr, M; Rowlinson, A; Johnston, S; Shannon, R M; Voronkov, M A; Ward, C; Banyer, J; Hancock, P J; Murphy, Tara; Allison, J R; Amy, S W; Ball, L; Bannister, K; Bock, D C -J; Brodrick, D; Brothers, M; Brown, A J; Bunton, J D; Chapman, J; Chippendale, A P; Chung, Y; DeBoer, D; Diamond, P; Edwards, P G; Ekers, R; Ferris, R H; Forsyth, R; Gough, R; Grancea, A; Gupta, N; Harvey-Smith, L; Hay, S; Hayman, D B; Hotan, A W; Hoyle, S; Humphreys, B; Indermuehle, B; Jacka, C E; Jackson, C A; Jackson, S; Jeganathan, K; Joseph, J; Kendall, R; Kiraly, D; Koribalski, B; Leach, M; Lenc, E; MacLeod, A; Mader, S; Marquarding, M; Marvil, J; McClure-Griffiths, N; McConnell, D; Mirtschin, P; Neuhold, S; Ng, A; Norris, R P; O'Sullivan, J; Pearce, S; Phillips, C J; Popping, A; Qiao, R Y; Reynolds, J E; Roberts, P; Sault, R J; Schinckel, A E T; Serra, P; Shaw, R; Shimwell, T W; Storey, M; Sweetnam, A W; Tzioumis, A; Westmeier, T; Whiting, M; Wilson, C D

    2015-01-01

    We use observations from the Boolardy Engineering Test Array (BETA) of the Australian Square Kilometre Array Pathfinder (ASKAP) telescope to search for transient radio sources in the field around the intermittent pulsar PSR J1107-5907. The pulsar is thought to switch between an "off" state in which no emission is detectable, a weak state and a strong state. We ran three independent transient detection pipelines on two-minute snapshot images from a 13 hour BETA observation in order to 1) study the emission from the pulsar, 2) search for other transient emission from elsewhere in the image and 3) to compare the results from the different transient detection pipelines. The pulsar was easily detected as a transient source and, over the course of the observations, it switched into the strong state three times giving a typical timescale between the strong emission states of 3.7 hours. After the first switch it remained in the strong state for almost 40 minutes. The other strong states lasted less than 4 minutes. Th...

  6. Wide-Band Spectra of Giant Radio Pulses from the Crab Pulsar

    CERN Document Server

    Mikami, Ryo; Tanaka, Shuta J; Kisaka, Shota; Sekido, Mamoru; Takefuji, Kazuhiro; Takeuchi, Hiroshi; Misawa, Hiroaki; Tsuchiya, Fuminori; Kita, Hajime; Yonekura, Yoshinori; Terasawa, Toshio

    2016-01-01

    We present the results of the simultaneous observation of the Giant Radio Pulses (GRPs) from the Crab pulsar at 0.3, 1.6, 2.2, 6.7 and 8.4 GHz with four telescopes in Japan. We obtain 3194 and 272 GRPs occurring at the main pulse and the interpulse phases, respectively. A few GRPs detected at both 0.3 and 8.4 GHz are the most wide-band samples ever reported. In the frequency range from 0.3 to 2.2 GHz, we find that about 70\\% or more of the GRP spectra are consistent with single power-laws and the spectral indices of them are distributed from $-4$ to $-1$. We also find that a significant number of GRPs have so hard spectral index $\\sim -1$) that the fluence at 0.3 GHz is below the detection limit (``dim-hard' GRPs). Stacking light curves of such dim-hard GRPs at 0.3 GHz, we detect consistent enhancement compared to the off-GRP light curve. Our samples show apparent correlations between the fluences and the spectral hardness, which indicates that more energetic GRPs tend to show softer spectra. Our comprehensiv...

  7. The ratio of profile peak separations as a probe of pulsar radio-beam structure

    Science.gov (United States)

    Dyks, J.; Pierbattista, M.

    2015-12-01

    The known population of pulsars contains objects with four- and five-component profiles, for which the peak-to-peak separations between the inner and outer components can be measured. These Q- and M-type profiles can be interpreted as a result of sightline cut through a nested-cone beam, or through a set of azimuthal fan beams. We show that the ratio RW of the components' separations provides a useful measure of the beam shape, which is mostly independent of parameters that determine the beam scale and complicate interpretation of simpler profiles. In particular, the method does not depend on the emission altitude and the dipole tilt distribution. The different structures of the radio beam imply manifestly different statistical distributions of RW, with the conal model being several orders of magnitude less consistent with data than the fan-beam model. To bring the conal model into consistency with data, strong effects of observational selection need to be called for, with 80 per cent of Q and M profiles assumed to be undetected because of intrinsic blending effects. It is concluded that the statistical properties of Q and M profiles are more consistent with the fan-shaped beams, than with the traditional nested-cone geometry.

  8. NuSTAR observations of the young, energetic radio pulsar PSR B1509-58

    CERN Document Server

    Chen, Ge; Kaspi, Victoria M; Harrison, Fiona; Madsen, Kristen; Stern, Daniel

    2015-01-01

    We report on Nuclear Spectroscopic Telescope Array (NuSTAR) hard X-ray observations of the young rotation-powered radio pulsar PSR B1509$-$58 in the supernova remnant MSH 15$-$52. We confirm the previously reported curvature in the hard X-ray spectrum, showing that a log parabolic model provides a statistically superior fit to the spectrum compared with the standard power law. The log parabolic model describes the NuSTAR data, as well as previously published gamma-ray data obtained with COMPTEL and AGILE, all together spanning 3 keV through 500 MeV. Our spectral modelling allows us to constrain the peak of the broadband high energy spectrum to be at 2.6$\\pm$0.8 MeV, an improvement of nearly an order of magnitude over previous measurements. In addition, we calculate NuSTAR spectra in 26 pulse phase bins and confirm previously reported variations of photon indices with phase. Finally, we measure the pulsed fraction of PSR B1509$-$58 in the hard X-ray energy band for the first time. Using the energy resolved pul...

  9. The ratio of profile peak separations as a probe of pulsar radio-beam structure

    CERN Document Server

    Dyks, J

    2015-01-01

    The known population of pulsars contains objects with four and five component profiles, for which the peak-to-peak separations between the inner and outer components can be measured. These Q and M type profiles can be interpreted as a result of sightline cut through a nested cone beam, or through a set of azimuthal fan beams. We show that the ratio R_W of the components' separations provides a useful measure of the beam shape, which is mostly independent of parameters that determine the beam scale and complicate interpretation of simpler profiles. In particular, the method does not depend on the emission altitude and the dipole tilt distribution. The different structures of the radio beam imply manifestly different statistical distributions of R_W, with the conal model being several orders of magnitude less consistent with data than the fan beam model. To bring the conal model into consistency with data, strong effects of observational selection need to be called for, with 80% of Q and M profiles assumed to b...

  10. Fermi pulsar revolution

    CERN Document Server

    Caraveo, Patrizia A

    2010-01-01

    2009 has been an extraordinary year for gamma-ray pulsar astronomy and 2010 promises to be equally good. Not only have we registered an extraordinary increase in the number of pulsars detected in gamma rays, but we have also witnessed the birth of new sub-families: first of all, the radio-quiet gamma pulsars and later an ever growing number of millisecond pulsars, a real surprise. We started with a sample of 7 gamma-ray emitting neutron stars (6 radio pulsars and Geminga) and now the Fermi-LAT harvest encompasses 24 "Geminga-like" new gamma-ray pulsars, a dozen millisecond pulsars and about thirty radio pulsars. Moreover, radio searches targeted to LAT unidentified sources yielded 18 new radio millisecond pulsars, several of which have been already detected also in gamma rays. Thus, currently the family of gamma-ray emitting neutron stars seems to be evenly divided between classical radio pulsars, millisecond pulsars and radio quiet neutron stars.

  11. Investigation of iron emission lines in the eclipsing high mass X-ray binary pulsar OAO 1657-415

    CERN Document Server

    Jaisawal, Gaurava K

    2016-01-01

    We present the results obtained from timing and spectral studies of high mass X-ray binary pulsar OAO 1657-415 using a Suzaku observations in 2011 September. X-ray pulsations were detected in the light curves up to $\\sim$70 keV. The continuum spectra during the high- and low-flux regions in light curves were well described by high energy cutoff power-law model along with a blackbody component and iron fluorescent lines at 6.4 keV and 7.06 keV. Time resolved spectroscopy was carried out by dividing the entire observations into 18 narrow segments. Presence of additional dense matter at various orbital phases was confirmed as the cause of low-flux regions in the observations. Presence of additional matter at several orbital phases of the pulsar was interpreted as due to the inhomogeneously distributed clumps of matter around the neutron star. Using clumpy wind hypothesis, the physical parameters of the clumps causing the high- and low-flux episodes in the pulsar light curve were estimated. The equivalent width o...

  12. Programmable Ultra Lightweight System Adaptable Radio (PULSAR) Low Cost Telemetry - Access from Space Advanced Technologies or Down the Middle

    Science.gov (United States)

    Sims. Herb; Varnavas, Kosta; Eberly, Eric

    2013-01-01

    Software Defined Radio (SDR) technology has been proven in the commercial sector since the early 1990's. Today's rapid advancement in mobile telephone reliability and power management capabilities exemplifies the effectiveness of the SDR technology for the modern communications market. In contrast, presently qualified satellite transponder applications were developed during the early 1960's space program. Programmable Ultra Lightweight System Adaptable Radio (PULSAR, NASA-MSFC SDR) technology revolutionizes satellite transponder technology by increasing data through-put capability by, at least, an order of magnitude. PULSAR leverages existing Marshall Space Flight Center SDR designs and commercially enhanced capabilities to provide a path to a radiation tolerant SDR transponder. These innovations will (1) reduce the cost of NASA Low Earth Orbit (LEO) and Deep Space transponders, (2) decrease power requirements, and (3) a commensurate volume reduction. Also, PULSAR increases flexibility to implement multiple transponder types by utilizing the same hardware with altered logic - no analog hardware change is required - all of which can be accomplished in orbit. This provides high capability, low cost, transponders to programs of all sizes. The final project outcome would be the introduction of a Technology Readiness Level (TRL) 7 low-cost CubeSat to SmallSat telemetry system into the NASA Portfolio.

  13. Pulsed Gamma Rays from the Original Millisecond and Black Widow Pulsars: a case for Caustic Radio Emission?

    CERN Document Server

    Guillemot, L; Venter, C; Kerr, M; Pancrazi, B; Livingstone, M; Janssen, G H; Jaroenjittichai, P; Kramer, M; Cognard, I; Stappers, B W; Harding, A K; Camilo, F; Espinoza, C M; Freire, P C C; Gargano, F; Grove, J E; Johnston, S; Michelson, P F; Noutsos, A; Parent, D; Ransom, S M; Ray, P S; Shannon, R; Smith, D A; Theureau, G; Thorsett, S E; Webb, N

    2011-01-01

    We report the detection of pulsed gamma-ray emission from the fast millisecond pulsars (MSPs) B1937+21 (also known as J1939+2134) and B1957+20 (J1959+2048) using 18 months of survey data recorded by the \\emph{Fermi} Large Area Telescope (LAT) and timing solutions based on radio observations conducted at the Westerbork and Nan\\c{c}ay radio telescopes. In addition, we analyzed archival \\emph{RXTE} and \\emph{XMM-Newton} X-ray data for the two MSPs, confirming the X-ray emission properties of PSR B1937+21 and finding evidence ($\\sim 4\\sigma$) for pulsed emission from PSR B1957+20 for the first time. In both cases the gamma-ray emission profile is characterized by two peaks separated by half a rotation and are in close alignment with components observed in radio and X-rays. These two pulsars join PSRs J0034-0534 and J2214+3000 to form an emerging class of gamma-ray MSPs with phase-aligned peaks in different energy bands. The modeling of the radio and gamma-ray emission profiles suggests co-located emission regions...

  14. Pulsed Gamma Rays from the Original Millisecond and Black Widow Pulsars: A Case for Caustic Radio Emission?

    Science.gov (United States)

    Guillemot, L.; Johnson, T. J.; Venter, C.; Kerr, M.; Pancrazi, B.; Livingstone, M.; Janssen, G. H.; Jaroenjittichai, P.; Kramer, M.; Cognard, I.; Stappers, B. W.; Harding, A. K.; Camilo, F.; Espinoza, C. M.; Freire, P. C. C.; Gargano, F.; Grove, J. E.; Johnston, S.; Michelson, P. F.; Noutsos, A.; Parent, D.; Ransom, S. M.; Ray, P. S.; Shannon, R.; Smith, D. A.; Theureau, G.; Thorsett, S. E.; Webb, N.

    2012-01-01

    We report the detection of pulsed gamma-ray emission from the fast millisecond pulsars (MSPs) B1937+21 (also known as J1939+2134) and B1957+20 (J1959+2048) using 18 months of survey data recorded by the Fermi Large Area Telescope and timing solutions based on radio observations conducted at the Westerbork and Nançay radio telescopes. In addition, we analyzed archival Rossi X-ray Timing Explorer and XMM-Newton X-ray data for the two MSPs, confirming the X-ray emission properties of PSR B1937+21 and finding evidence (~4σ) for pulsed emission from PSR B1957+20 for the first time. In both cases the gamma-ray emission profile is characterized by two peaks separated by half a rotation and are in close alignment with components observed in radio and X-rays. These two pulsars join PSRs J0034-0534 and J2214+3000 to form an emerging class of gamma-ray MSPs with phase-aligned peaks in different energy bands. The modeling of the radio and gamma-ray emission profiles suggests co-located emission regions in the outer magnetosphere.

  15. Pulsed Gamma Rays from the Original Millisecond and Black Widow Pulsars: A Case for Caustic Radio Emission?

    Science.gov (United States)

    Guillemot, L.; Johnson, T. J.; Venter, C.; Kerr, M.; Pancrazi, B.; Livingstone, M.; Janssen, G. H.; Jaroenjittichai, P.; Kramer, M.; Cognard, I.; Stappers, B. W.; Harding, A. K.; Camilo, F.; Espinoza, C. M.; Freire, P. C. C.; Gargano, F.; Grove, J. E.; Johnston, S.; Michelson, P. F.; Noutsos, A.; Parent, D.; Ransom, S. M.; Ray, P. S.; Shannon, R.; Smith, D. A.

    2011-01-01

    We report the detection of pulsed gamma-ray emission from the fast millisecond pulsars (MSPs) B1937+21 (also known as J1939+2134) and B1957+20 (J1959+2048) using 18 months of survey data recorded by the Fermi Large Area Telescope (LAT) and timing solutions based on radio observations conducted at the Westerbork and Nancay radio telescopes. In addition, we analyzed archival RXTE and XMM-Newton X-ray data for the two MSPs, confirming the X-ray emission properties of PSR B1937+21 and finding evidence (approx. 4(sigma)) for pulsed emission from PSR B1957+20 for the first time. In both cases the gamma-ray emission profile is characterized by two peaks separated by half a rotation and are in close alignment with components observed in radio and X-rays. These two pulsars join PSRs J0034..0534 and J2214+3000 to form an emerging class of gamma-ray MSPs with phase-aligned peaks in different energy bands. The modeling of the radio and gamma-ray emission pro les suggests co-located emission regions in the outer magnetosphere.

  16. Radio Counterparts of Compact Binary Mergers detectable in Gravitational Waves: A Simulation for an Optimized Survey

    CERN Document Server

    Hotokezaka, Kenta; Hallinan, Gregg; Lazio, T Joseph W; Nakar, Ehud; Piran, Tsvi

    2016-01-01

    Mergers of binary neutron stars and black hole-neutron star binaries produce gravitational-wave (GW) emission and outflows with significant kinetic energies. These outflows result in radio emissions through synchrotron radiation of accelerated electrons in shocks formed with the circum-merger medium. We explore the detectability of these synchrotron generated radio signals by follow-up observations of GW merger events lacking a detection of electromagnetic counterparts in other wavelengths. We model radio light curves arising from (i) sub-relativistic merger ejecta and (ii) ultra-relativistic jets. The former produces radio remnants on timescales of a few years and the latter produces $\\gamma$-ray bursts in the direction of the jet and orphan radio afterglows extending over wider angles on timescales of a week to a month. The intensity and duration of these radio counterparts depend on the kinetic energies of the outflows and on circum-merger densities. We estimate the detectability of the radio counterparts ...

  17. Constraints on Black Hole/Host Galaxy Co-evolution and Binary Stalling Using Pulsar Timing Arrays

    CERN Document Server

    Simon, Joseph

    2016-01-01

    Pulsar timing arrays are now setting increasingly tight limits on the gravitational wave background from binary supermassive black holes. But as upper limits grow more constraining, what can be implied about galaxy evolution? We investigate which astrophysical parameters have the largest impact on strain spectrum predictions and provide a simple framework to directly translate between measured values for the parameters of galaxy evolution and PTA limits on the gravitational wave background of binary supermassive black holes. We find that the most influential observable is the relation between a host galaxy's central bulge and its central black hole, $\\mbox{$M_{\\bullet}$-$M_{\\rm bulge}$}$, which has the largest effect on the mean value of the characteristic strain amplitude. However, the variance of each prediction is dominated by uncertainties in the galaxy stellar mass function. Using this framework with the best published PTA limit, we can set limits on the shape and scatter of the $\\mbox{$M_{\\bullet}$-$M_{...

  18. Discovery of a Be/X-ray pulsar binary and associated supernova remnant in the Wing of the SMC

    CERN Document Server

    Hénault-Brunet, V; Guerrero, M A; Sun, W; Chu, Y -H; Evans, C J; Gallagher, J S; Gruendl, R A; Reyes-Iturbide, J

    2011-01-01

    We report on a new Be/X-ray pulsar binary located in the Wing of the Small Magellanic Cloud (SMC). The strong pulsed X-ray source was discovered with the Chandra and XMM-Newton X-ray observatories. The X-ray pulse period of 1062 s is consistently determined from both Chandra and XMM-Newton observations, revealing one of the slowest rotating X-ray pulsars known in the SMC. The optical counterpart of the X-ray source is the emission-line star 2dFS 3831. Its B0-0.5(III)e+ spectral type is determined from VLT-FLAMES and 2dF optical spectroscopy, establishing the system as a Be/X-ray binary (Be-XRB). The hard X-ray spectrum is well fitted by a power-law with additional thermal and blackbody components, the latter reminiscent of persistent Be-XRBs. This system is the first evidence of a recent supernova in the low density surroundings of NGC 602. We detect a shell nebula around 2dFS 3831 in H-alpha and [O III] images and conclude that it is most likely a supernova remnant. If it is linked to the supernova explosion...

  19. NUSTAR OBSERVATIONS OF THE YOUNG, ENERGETIC RADIO PULSAR PSR B1509–58

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Ge; Kaspi, Victoria M. [Department of Physics, McGill University, Montreal, Quebec, H3A 2T8 (Canada); An, Hongjun [Department of Physics/KIPAC, Stanford University, Stanford, CA 94305-4060 (United States); Harrison, Fiona A.; Madsen, Kristin K. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Stern, Daniel [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Mail Stop 169-221, Pasadena, CA 91109 (United States)

    2016-02-01

    We report on Nuclear Spectroscopic Telescope Array (NuSTAR) hard X-ray observations of the young rotation-powered radio pulsar PSR B1509−59 in the supernova remnant MSH 15−52. We confirm the previously reported curvature in the hard X-ray spectrum, showing that a log parabolic model provides a statistically superior fit to the spectrum compared with the standard power law. The log parabolic model describes the NuSTAR data, as well as previously published γ-ray data obtained with COMPTEL and AGILE, all together spanning 3 keV through 500 MeV. Our spectral modeling allows us to constrain the peak of the broadband high energy spectrum to be at 2.6 ± 0.8 MeV, an improvement of nearly an order of magnitude in precision over previous measurements. In addition, we calculate NuSTAR spectra in 26 pulse phase bins and confirm previously reported variations of photon indices with phase. Finally, we measure the pulsed fraction of PSR B1509−58 in the hard X-ray energy band for the first time. Using the energy resolved pulsed fraction results, we estimate that the pulsar’s off-pulse emission has a photon index value between 1.26 and 1.96. Our results support a model in which the pulsar’s lack of GeV emission is due to viewing geometry, with the X-rays originating from synchrotron emission from secondary pairs in the magnetosphere.

  20. RADIO-SELECTED BINARY ACTIVE GALACTIC NUCLEI FROM THE VERY LARGE ARRAY STRIPE 82 SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Hai [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52245 (United States); Myers, A. D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Djorgovski, S. G.; Yan, Lin [California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Wrobel, J. M. [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States); Stockton, A. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

    2015-01-20

    Galaxy mergers play an important role in the growth of galaxies and their supermassive black holes. Simulations suggest that tidal interactions could enhance black hole accretion, which can be tested by the fraction of binary active galactic nuclei (AGNs) among galaxy mergers. However, determining the fraction requires a statistical sample of binaries. We have identified kiloparsec-scale binary AGNs directly from high-resolution radio imaging. Inside the 92 deg{sup 2} covered by the high-resolution Very Large Array survey of the Sloan Digital Sky Survey (SDSS) Stripe 82 field, we identified 22 grade A and 30 grade B candidates of binary radio AGNs with angular separations less than 5'' (10 kpc at z = 0.1). Eight of the candidates have optical spectra for both components from the SDSS spectroscopic surveys and our Keck program. Two grade B candidates are projected pairs, but the remaining six candidates are all compelling cases of binary AGNs based on either emission line ratios or the excess in radio power compared to the Hα-traced star formation rate. Only two of the six binaries were previously discovered by an optical spectroscopic search. Based on these results, we estimate that ∼60% of our binary candidates would be confirmed once we obtain complete spectroscopic information. We conclude that wide-area high-resolution radio surveys offer an efficient method to identify large samples of binary AGNs. These radio-selected binary AGNs complement binaries identified at other wavelengths and are useful for understanding the triggering mechanisms of black hole accretion.

  1. INTEGRAL detection of the multi-peaked emission from the Be/X-ray binary pulsar GRO J1008-57

    DEFF Research Database (Denmark)

    Fiocchi, M.; Sguera, A.; Chenevez, Jérôme

    2014-01-01

    Recent observations from the on-going INTEGRAL Galactic Plane Scanning programme (PI: A. Bazzano) have detected increasing X-ray flux from the Be/X-ray binary pulsar GRO J1008-57, confirming the re-brightening detected by MAXI/GSC (ATel #6819). The source was in the field of view of the IBIS...

  2. The Quiescent X-Ray Properties of the Accreting Millisecond X-Ray Pulsar and Eclipsing binary Swift J1749.4-2807

    NARCIS (Netherlands)

    N. Degenaar; A. Patruno; R. Wijnands

    2012-01-01

    Swift J1749.4-2807 is a transient neutron star low-mass X-ray binary that contains an accreting millisecond X-ray pulsar spinning at 518 Hz. It is the first of its kind that displays X-ray eclipses, which holds significant promise to precisely constrain the mass of the neutron star. We report on a s

  3. The Double Pulsar System J0737-3039

    Science.gov (United States)

    Lorimer, D. R.

    The double pulsar system J0737 - 3039 - a 22.7 ms pulsar in a compact 2.4 hr orbit about a 2.7 s pulsar was one of the long-awaited "holy grails" of pulsar astronomy. After only two years of timing, the system is close to surpassing the original Hulse-Taylor binary as a test of general relativity. On-going timing should soon reveal second-order effects in the post-Newtonian parameters. In addition, the observed interactions of the radio beams of the two pulsars provide a unique laboratory for probing neutron star magnetospheres and relativistic winds. Finally, a revised estimate of the cosmic rate of double neutron star mergers including J0737 - 3039 boosts previous estimates by an order of magnitude and suggests a high detection rate for the advanced LIGO gravitational wave detector.

  4. PSR J2021+3651 A Young Radio Pulsar Coincident with an Unidentified EGRET Gamma-ray Source

    CERN Document Server

    Roberts, M S E; Ransom, S M; Kaspi, V M; Freire, P C C; Crawford, F; Lorimer, D R; Roberts, Mallory S.E.; Hessels, Jason W.T.; Ransom, Scott M.; Kaspi, Victoria M.; Freire, Paulo C.C.; Crawford, Fronefield; Lorimer, Duncan R.

    2002-01-01

    We report on a deep search for radio pulsations toward five unidentified ASCA X-ray sources coincident with EGRET gamma-ray sources. This search has led to the discovery of a young and energetic pulsar using data obtained with the new Wideband Arecibo Pulsar Processor. PSR J2021+3651 is likely associated with the X-ray source AX J2021.1+3651, which in turn is likely associated with the COS B high energy gamma-ray source 2CG 075+00, also known as GeV J2020+3658 or 3EG J2021+3716. PSR J2021+3651 has a rotation period P = 104 ms and P_dot = 9.6x10^{-14}, implying a characteristic age ~17 kyr and a spin-down luminosity E_dot ~ 3.4x10^{36}ergs/s. The dispersion measure DM ~ 371 pc cm^{-3} is by far the highest of any observed pulsar in the Galactic longitude range 55 10 kpc, and a high gamma-ray efficiency of \\~15%, but the true distance may be closer if there is a significant contribution to the DM from excess gas in the Cygnus region. The implied luminosity of the associated X-ray source suggests the X-ray emis...

  5. Measurement of Gravitational Spin-Orbit Coupling in a Binary Pulsar System

    Science.gov (United States)

    Stairs, I. H.; Thorsett. S. E.; Arzoumanian, Z.

    2004-01-01

    In relativistic gravity, a spinning pulsar will precess as it orbits a compact companion star. We have measured the effect of such precession on the average shape and polarization of the radiation from PSR B1534+12. We have also detected, with limited precision, special-relativistic aberration of the revolving pulsar beam due to orbital motion. Our observations fix the system geometry, including the misalignment between the spin and orbital angular momenta, and yield a measurement of the precession timescale consistent with the predictions of General Relativity.

  6. Formation and evolution of X-ray binaries

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    We review recent progress in theoretical understanding of X-ray binaries,which has largely been driven by new observations.We select several topics including formation of compact low-mass X-ray binaries,the evolutionary connection between low-mass X-ray binaries and binary and millisecond radio pulsars,and ultraluminous X-ray sources,to illustrate the interplay between theories and observations.

  7. Search for Millisecond Pulsars for the Pulsar Timing Array project

    Science.gov (United States)

    Milia, S.

    2012-03-01

    Pulsars are rapidly rotating highly magnetised neutron stars (i.e. ultra dense stars, where about one solar mass is concentrated in a sphere with a radius of ~ 10 km), which irradiate radio beams in a fashion similar to a lighthouse. As a consequence, whenever the beams cut our line of sight we perceive a radio pulses, one (or two) per pulsar rotation, with a frequency up to hundred of times a second. Owing to their compact nature, rapid spin and high inertia, pulsars are in general fairly stable rotators, hence the Times of Arrival (TOAs) of the pulses at a radio telescope can be used as the ticks of a clock. This holds true in particular for the sub­class of the millisecond pulsars (MSPs), having a spin period smaller than the conventional limit of 30 ms, whose very rapid rotation and relatively older age provide better rotational stability than the ordinary pulsars. Indeed, some MSPs rotate so regularly that they can rival the best atomic clocks on Earth over timespan of few months or years.This feature allows us to use MSPs as tools in a cosmic laboratory, by exploiting a procedure called timing, which consists in the repeated and regular measurement of the TOAs from a pulsar and then in the search for trends in the series of the TOAs over various timespans, from fraction of seconds to decades.For example the study of pulsars in binary systems has already provided the most stringent tests to date of General Relativity in strong gravitational fields and has unambiguously showed the occurrence of the emission of gravitational waves from a binary system comprising two massive bodies in a close orbit. In last decades a new exciting perspective has been opened, i.e. to use pulsars also for a direct detection of the so far elusive gravitational waves and thereby applying the pulsar timing for cosmological studies. In fact, the gravitational waves (GWs) going across our Galaxy pass over all the Galactic pulsars and the Earth, perturbing the space­time at the

  8. DEEP X-RAY OBSERVATIONS OF THE YOUNG HIGH-MAGNETIC-FIELD RADIO PULSAR J1119-6127 AND SUPERNOVA REMNANT G292.2-0.5

    Energy Technology Data Exchange (ETDEWEB)

    Ng, C.-Y.; Kaspi, V. M. [Department of Physics, McGill University, Montreal, QC H3A 2T8 (Canada); Ho, W. C. G. [School of Mathematics, University of Southampton, Southampton SO17 1BJ (United Kingdom); Weltevrede, P. [Jodrell Bank Centre for Astrophysics, University of Manchester, Alan Turing Building, Manchester M13 9PL (United Kingdom); Bogdanov, S. [Columbia Astrophysics Laboratory, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Shannon, R. [CSIRO Astronomy and Space Sciences, Australia Telescope National Facility, Marsfield, NSW 2210 (Australia); Gonzalez, M. E., E-mail: ncy@physics.mcgill.ca [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1 (Canada)

    2012-12-10

    High-magnetic-field radio pulsars are important transition objects for understanding the connection between magnetars and conventional radio pulsars. We present a detailed study of the young radio pulsar J1119-6127, which has a characteristic age of 1900 yr and a spin-down-inferred magnetic field of 4.1 Multiplication-Sign 10{sup 13} G, and its associated supernova remnant G292.2-0.5, using deep XMM-Newton and Chandra X-ray Observatory exposures of over 120 ks from each telescope. The pulsar emission shows strong modulation below 2.5 keV with a single-peaked profile and a large pulsed fraction of 0.48 {+-} 0.12. Employing a magnetic, partially ionized hydrogen atmosphere model, we find that the observed pulse profile can be produced by a single hot spot of temperature 0.13 keV covering about one-third of the stellar surface, and we place an upper limit of 0.08 keV for an antipodal hot spot with the same area. The non-uniform surface temperature distribution could be the result of anisotropic heat conduction under a strong magnetic field, and a single-peaked profile seems common among high-B radio pulsars. For the associated remnant G292.2-0.5, its large diameter could be attributed to fast expansion in a low-density wind cavity, likely formed by a Wolf-Rayet progenitor, similar to two other high-B radio pulsars.

  9. Star Cluster Buzzing With Pulsars

    Science.gov (United States)

    2005-01-01

    A dense globular star cluster near the center of our Milky Way Galaxy holds a buzzing beehive of rapidly-spinning millisecond pulsars, according to astronomers who discovered 21 new pulsars in the cluster using the National Science Foundation's 100-meter Robert C. Byrd Green Bank Telescope (GBT) in West Virginia. The cluster, called Terzan 5, now holds the record for pulsars, with 24, including three known before the GBT observations. Pulsar Diagram Pulsar Diagram: Click on image for more detail. "We hit the jackpot when we looked at this cluster," said Scott Ransom, an astronomer at the National Radio Astronomy Observatory in Charlottesville, VA. "Not only does this cluster have a lot of pulsars -- and we still expect to find more in it -- but the pulsars in it are very interesting. They include at least 13 in binary systems, two of which are eclipsing, and the four fastest-rotating pulsars known in any globular cluster, with the fastest two rotating nearly 600 times per second, roughly as fast as a household blender," Ransom added. Ransom and his colleagues reported their findings to the American Astronomical Society's meeting in San Diego, CA, and in the online journal Science Express. The star cluster's numerous pulsars are expected to yield a bonanza of new information about not only the pulsars themselves, but also about the dense stellar environment in which they reside and probably even about nuclear physics, according to the scientists. For example, preliminary measurements indicate that two of the pulsars are more massive than some theoretical models would allow. "All these exotic pulsars will keep us busy for years to come," said Jason Hessels, a Ph.D student at McGill University in Montreal. Globular clusters are dense agglomerations of up to millions of stars, all of which formed at about the same time. Pulsars are spinning, superdense neutron stars that whirl "lighthouse beams" of radio waves or light around as they spin. A neutron star is what is

  10. Fermi Study of 5--300 GeV Emission from the High-mass Pulsar Binary PSR B1259-63/LS 2883

    Science.gov (United States)

    Xing, Yi; Wang, Zhongxiang; Takata, Jumpei

    2016-09-01

    We report the results from our detailed analysis of the Fermi Large Area Telescope data for the pulsar binary PSR B1259-63/LS 2883. During the GeV flares that occurred when the pulsar was in the periastron passages, we have detected a 5-300 GeV component at ≃5σ in emission from the binary. The detection verifies the presence of the component that has been marginally found in previous studies of the binary. Furthermore, we have discovered that this component was marginally present even in the quiescent state of the binary, specifically the mean anomaly phase 0.7-0.9. The component can be described by a power law with a photon index Γ ˜ 1.4, and the flux in the flares is approximately one order of magnitude higher than that in quiescence. We discuss the origin of this component. It likely arises from the inverse-Compton process: due to the interaction between the winds from the pulsar and its massive companion, high-energy particles from the shock scatter the seed photons from the companion to GeV/TeV energies. Based on this scenario, model fits to the broad-band X-ray to TeV spectra of the binary in the flaring and quiescent states are provided.

  11. 2S1553-542: a Be/X-ray binary pulsar on the far side of the Galaxy

    CERN Document Server

    Lutovinov, Alexander A; Townsend, Lee J; Tsygankov, Sergey S; Kennea, Jamie

    2016-01-01

    We report the results of a comprehensive analysis of X-ray (Chandra and Swift observatories), optical (Southern African Large Telescope, SALT) and near-infrared (the VVV survey) observations of the Be/X-ray binary pulsar 2S1553-542. Accurate coordinates for the X-ray source are determined and are used to identify the faint optical/infrared counterpart for the first time. Using VVV and SALTICAM photometry, we have constructed the spectral energy distribution (SED) for this star and found a moderate NIR excess that is typical for Be stars and arises due to the presence of circumstellar material (disk). A comparison of the SED with those of known Be/X-ray binaries has allowed us to estimate the spectral type of the companion star as B1-2V and the distance to the system as $>15$ kpc. This distance estimation is supported by the X-ray data and makes 2S1553-542 one of the most distant X-ray binaries within the Milky Way, residing on the far side in the Scutum-Centaurus arm or even further.

  12. Search for a Correlation Between Very-High-Energy Gamma Rays and Giant Radio Pulses in the Crab Pulsar

    Science.gov (United States)

    Aliu, E.; Archambault, S.; Arlen, T.; Aune, T.; Beilicke, M.; Benbow, W.; Bouvier, A.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cesarini, A.; Ciupik, L.; Collins-Hughes, E.; Connolly, M. P.; Cui, W.; Dickherber, R.; Duke, C.; Dumm, J.; Falcone, A.; Federici, S.; Feng, Q.; Finley, J. P.; Finnegan, G.; Fortson, L.; Perkins, J. S.

    2012-01-01

    We present the results of a joint observational campaign between the Green Bank radio telescope and the VERITAS gamma-ray telescope, which searched for a correlation between the emission of very-high-energy (VHE) gamma rays ( E(sub Gamma) > 150 GeV) and giant radio pulses (GRPs) from the Crab pulsar at 8.9 GHz. A total of 15,366 GRPs were recorded during 11.6 hr of simultaneous observations, which were made across four nights in 2008 December and in 2009 November and December. We searched for an enhancement of the pulsed gamma-ray emission within time windows placed around the arrival time of the GRP events. In total, eight different time windows with durations ranging from 0.033 ms to 72 s were positioned at three different locations relative to the GRP to search for enhanced gamma-ray emission which lagged, led, or was concurrent with, the GRP event. Furthermore, we performed separate searches on main pulse GRPs and interpulse GRPs and on the most energetic GRPs in our data sample. No significant enhancement of pulsed VHE emission was found in any of the preformed searches. We set upper limits of 5-10 times the average VHE flux of the Crab pulsar on the flux simultaneous with interpulse GRPs on single-rotation-period timescales. On approx. 8 s timescales around interpulse GRPs, we set an upper limit of 2-3 times the average VHE flux. Within the framework of recent models for pulsed VHE emission from the Crab pulsar, the expected VHE-GRP emission correlations are below the derived limits.

  13. A Compact X-Ray Source in the Radio Pulsar-wind Nebula G141.2+5.0

    Science.gov (United States)

    Reynolds, Stephen P.; Borkowski, Kazimierz J.

    2016-01-01

    We report the results of a 50 ks Chandra observation of the recently discovered radio object G141.2+5.0, presumed to be a pulsar-wind nebula. We find a moderately bright unresolved X-ray source that we designate CXOU J033712.8 615302 coincident with the central peak radio emission. An absorbed power-law fit to the 241 counts describes the data well, with absorbing column {N}H=6.7(4.0,9.7)× {10}21 cm-2 and photon index {{Γ }}=1.8(1.4,2.2). For a distance of 4 kpc, the unabsorbed luminosity between 0.5 and 8 keV is {1.7}-0.3+0.4× {10}32 erg s-1 (90% confidence intervals). Both LX and Γ are quite typical of pulsars in PWNe. No extended emission is seen; we estimate a conservative 3σ upper limit to the surface brightness of any X-ray PWN near the point source to be 3× {10}-17 erg cm-2 s-1 arcsec-2 between 0.5 and 8 keV, assuming the same spectrum as the point source; for a nebula of diameter 13\\prime\\prime , the flux limit is 6% of the flux of the point source. The steep radio spectrum of the PWN (α ˜ -0.7), if continued to the X-ray without a break, predicts {L}{{X}} {{(nebula)}}˜ 1× {10}33 erg s-1, so additional spectral steepening between radio and X-rays is required, as is true of all known PWNe. The high Galactic latitude gives a z-distance of 350 pc above the Galactic plane, quite unusual for a Population I object.

  14. Multi-wavelength emissions from the millisecond pulsar binary PSR J1023+0038 during an accretion active state

    CERN Document Server

    Takata, J; Leung, G C K; Kong, A K H; Tam, P H T; Hui, C Y; Wu, E M H; Xing, Y; Cao, Y; Tang, S; Wang, Z; Cheng, K S

    2013-01-01

    Recent observations strongly suggest that the millisecond pulsar binary PSR J1023+0038 has developed an accretion disk since 2013 June. We present the multi-wavelength analysis of PSR J1023+0038, which reveals that 1) its gamma-rays suddenly brightened within a few days in June/July 2013 and has remained at a high gamma-ray state for several months; 2) both UV and X-ray fluxes have increased by roughly an order of magnitude, and 3) the spectral energy distribution has changed significantly after the gamma-ray sudden flux change. Time variabilities associated with UV and X-rays are on the order of 100-500 seconds and 50-100 seconds respectively. Our model suggests that a newly formed accretion disk due to the sudden increase of the stellar wind could explain the changes of all these observed features. The increase of UV is emitted from the disk, and a new component in gamma-rays is produced by inverse Compton scattering between the new UV component and pulsar wind. The increase of X-rays results from the enhan...

  15. Suzaku view of Be/X-ray binary pulsar GX 304-1 during Type I X-ray outbursts

    CERN Document Server

    Jaisawal, Gaurava K; Epili, Prahlad

    2016-01-01

    We report the timing and spectral properties of Be/X-ray binary pulsar GX 304-1 by using two Suzaku observations during its 2010 August and 2012 January X-ray outbursts. Pulsations at ~275 s were clearly detected in the light curves from both the observations. Pulse profiles were found to be strongly energy-dependent. During 2010 observation, prominent dips seen in soft X-ray ($\\leq$10 keV) pulse profiles were found to be absent at higher energies. However, during 2012 observation, the pulse profiles were complex due to the presence of several dips. Significant changes in the shape of the pulse profiles were detected at high energies ($>$35 keV). A phase shift of $\\sim$0.3 was detected while comparing the phase of main dip in pulse profiles below and above $\\sim$35 keV. Broad-band energy spectrum of pulsar was well described by a partially absorbed Negative and Positive power-law with Exponential cutoff (NPEX) model with 6.4 keV iron line and a cyclotron absorption feature. Energy of cyclotron absorption line...

  16. A Compact X-ray Source in the Radio Pulsar-Wind Nebula G141.2+5.0

    CERN Document Server

    Reynolds, Stephen P

    2016-01-01

    We report the results of a 50 ks Chandra observation of the recently discovered radio object G141.2+5.0, presumed to be a pulsar-wind nebula. We find a moderately bright unresolved X-ray source which we designate CXOU J033712.8 615302 coincident with the central peak radio emission. An absorbed power-law fit to the 241 counts describes the data well, with absorbing column $N_H = 6.7 (4.0, 9.7) \\times 10^{21}$ cm$^{-2}$ and photon index $\\Gamma = 1.8 (1.4, 2.2)$. For a distance of 4 kpc, the unabsorbed luminosity between 0.5 and 8 keV is $ 1.7^{+0.4}_{-0.3} \\times 10^{32}$ erg s$^{-1}$ (90\\% confidence intervals). Both $L_X$ and $\\Gamma$ are quite typical of pulsars in PWNe. No extended emission is seen; we estimate a conservative $3 \\sigma$ upper limit to the surface brightness of any X-ray PWN near the point source to be $3 \\times 10^{-17}$ erg cm$^{-2}$ s$^{-1}$ arcsec$^{-2}$ between 0.5 and 8 keV, assuming the same spectrum as the point source; for a nebula of diameter $13"$, the flux limit is 6\\% of the f...

  17. Merger of a white dwarf-neutron star binary to 1029 carat diamonds: origin of the pulsar planets

    Science.gov (United States)

    Margalit, Ben; Metzger, Brian D.

    2017-03-01

    We show that the merger and tidal disruption of a carbon/oxygen (C/O) white dwarf (WD) by a neutron star (NS) binary companion provides a natural formation scenario for the PSR B1257+12 planetary system. Starting with initial conditions for the debris disc produced of the disrupted WD, we model its long-term viscous evolution, including for the first time the effects of mass and angular momentum loss during the early radiatively inefficient accretion flow (RIAF) phase and accounting for the unusual C/O composition on the disc opacity. For plausible values of the disc viscosity α ∼ 10-3-10-2 and the RIAF mass-loss efficiency, we find that the disc mass remaining near the planet formation radius at the time of solid condensation is sufficient to explain the pulsar planets. Rapid rocky planet formation via gravitational instability of the solid carbon dominated disc is facilitated by the suppression of vertical shear instabilities due to the high solid-to-gas ratio. Additional evidence supporting a WD-NS merger scenario includes (1) the low observed occurrence rate of pulsar planets (≲1 per cent of NS birth), comparable to the expected WD-NS merger rate; (2) accretion by the NS during the RIAF phase is sufficient to spin PSR B1257+12 up to its observed 6 ms period; (3) similar models of 'low angular momentum' discs, such as those produced from supernova fallback, find insufficient mass reaching the planet formation radius. The unusually high space velocity of PSR B1257+12 of ≳326 km s-1 suggests a possible connection to the calcium-rich transients, dim supernovae which occur in the outskirts of their host galaxies and were proposed to result from mergers of WD-NS binaries receiving supernova kicks. The C/O disc composition implied by our model likely results in carbon-rich planets with diamond interiors.

  18. Investigation of the bi-drifting subpulses of radio pulsar B1839-04 utilising the open-source data-analysis project PSRSALSA

    CERN Document Server

    Weltevrede, Patrick

    2016-01-01

    The usefulness and versatility of the PSRSALSA open-source pulsar data-analysis project is demonstrated through an analysis of the radio pulsar B1839-04. This study focuses on the phenomenon of bi-drifting, an effect where the drift direction of subpulses is systematically different in different pulse profile components. Bi-drifting is extremely rare in the pulsar population. Various tools in PSRSALSA, including those allowing quantification of periodicities in the subpulse modulation, their flux distribution, and polarization properties, are exploited to obtain a comprehensive picture of the radio properties of PSR B1839-04. In particular, the second harmonic in the fluctuation spectra of the subpulse modulation is exploited to convincingly demonstrate the existence of bi-drifting. Bi-drifting is confirmed with a completely independent method allowing the average modulation cycle to be determined. Polarization measurements were used to obtain a robust constraint on the magnetic inclination angle of less than...

  19. Radio Counterparts of Compact Binary Mergers Detectable in Gravitational Waves: A Simulation for an Optimized Survey

    Science.gov (United States)

    Hotokezaka, K.; Nissanke, S.; Hallinan, G.; Lazio, T. J. W.; Nakar, E.; Piran, T.

    2016-11-01

    Mergers of binary neutron stars and black hole-neutron star binaries produce gravitational-wave (GW) emission and outflows with significant kinetic energies. These outflows result in radio emissions through synchrotron radiation. We explore the detectability of these synchrotron-generated radio signals by follow-up observations of GW merger events lacking a detection of electromagnetic counterparts in other wavelengths. We model radio light curves arising from (i) sub-relativistic merger ejecta and (ii) ultra-relativistic jets. The former produce radio remnants on timescales of a few years and the latter produce γ-ray bursts in the direction of the jet and orphan-radio afterglows extending over wider angles on timescales of weeks. Based on the derived light curves, we suggest an optimized survey at 1.4 GHz with five epochs separated by a logarithmic time interval. We estimate the detectability of the radio counterparts of simulated GW-merger events to be detected by advanced LIGO and Virgo by current and future radio facilities. The detectable distances for these GW merger events could be as high as 1 Gpc. Around 20%-60% of the long-lasting radio remnants will be detectable in the case of the moderate kinetic energy of 3\\cdot {10}50 erg and a circum-merger density of 0.1 {{cm}}-3 or larger, while 5%-20% of the orphan-radio afterglows with kinetic energy of 1048 erg will be detectable. The detection likelihood increases if one focuses on the well-localizable GW events. We discuss the background noise due to radio fluxes of host galaxies and false positives arising from extragalactic radio transients and variable active galactic nuclei, and we show that the quiet radio transient sky is of great advantage when searching for the radio counterparts.

  20. High space velocities of single radio pulsars versus low orbital eccentricities and masses of double neutron stars: Evidence for two different neutron star formation mechanisms

    NARCIS (Netherlands)

    van den Heuvel, E.P.J.

    2010-01-01

    Radio pulsars tend to be high-velocity objects, which implies that the majority of them received a velocity kick of several hundreds of km s(-1) at birth. However, six of the eight known double neutron stars in the galactic disk have quite low orbital eccentricities (0.085-0.27), indicating - taking

  1. Fermi Study of 5-300 GeV emission from the high-mass pulsar binary PSR B1259-63/LS 2883

    CERN Document Server

    Xing, Yi; Takata, Jumpei

    2016-01-01

    We report the results from our detailed analysis of the Fermi Large Area Telescope (LAT) data for the pulsar binary PSR B1259-63/LS 2883. During the GeV flares that occurred when the pulsar was in the periastron passages, we have detected a 5--300 GeV component at $\\simeq 5\\sigma$ in emission from the binary. The detection verifies the presence of the component that has been marginally found in the previous studies of the binary. Furthermore, we have discovered that this component was present even in the quiescent state of the binary, specifically the mean anomaly phase 0.7--0.9. The component can be described by a power law with photon index $\\Gamma\\sim 1.4$, and the flux in the flares is approximately one order of magnitude higher than that in quiescence. We discuss the origin of this component. It likely arises from the inverse-Compton process: high-energy particles from the shock, due to the interaction between the winds from the pulsar and massive companion, scatter the seed photons from the companion to...

  2. Three Millisecond Pulsars in Fermi LAT Unassociated Bright Sources

    Science.gov (United States)

    Ransom, S. M.; Ray, P. S.; Camilo, F.; Roberts, M. S. E.; Celik, O.; Wolff, M. T.; Cheung, C. C.; Kerr, M.; Pennucci, T.; DeCesar, M. E.; Cognard, I.; Lyne, A. G.; Stappers, B. W.; Freire, P. C. C.; Grove, J. E.; Abdo, A. A.; Desvignes, G.; Donato, D.; Ferrara, E. C.; Gehrels, N.; Guillemot, L.; Gwon, C.; Johnston, S.; Harding, A. K.; Thompson, D. J.

    2010-01-01

    We searched for radio pulsars in 25 of the non-variable, unassociated sources in the Fermi LAT Bright Source List with the Green Bank Telescope at 820 MHz. We report the discovery of three radio and gamma-ray millisecond pulsar (MSPs) from a high Galactic latitude subset of these sources. All of the pulsars are in binary systems, which would have made them virtually impossible to detect in blind gamma-ray pulsation searches. They seem to be relatively normal, nearby (<= 2 kpc) MSPs. These observations, in combination with the Fermi detection of gamma-rays from other known radio MSPs, imply that most, if not all, radio MSPs are efficient gamma-ray producers. The gamma-ray spectra of the pulsars are power law in nature with exponential cutoffs at a few Ge V, as has been found with most other pulsars. The MSPs have all been detected as X-ray point sources. Their soft X-ray luminosities of approx 10(exp 30) - 10(exp 31) erg/s are typical of the rare radio MSPs seen in X-rays.

  3. The High Time Resolution Universe Pulsar Survey XII : Galactic plane acceleration search and the discovery of 60 pulsars

    CERN Document Server

    Ng, C; Bailes, M; Barr, E D; Bates, S D; Bhat, N D R; Burgay, M; Burke-Spolaor, S; Flynn, C M L; Jameson, A; Johnston, S; Keith, M J; Kramer, M; Levin, L; Petroff, E; Possenti, A; Stappers, B W; van Straten, W; Tiburzi, C; Eatough, R P; Lyne, A G

    2015-01-01

    We present initial results from the low-latitude Galactic plane region of the High Time Resolution Universe pulsar survey conducted at the Parkes 64-m radio telescope. We discuss the computational challenges arising from the processing of the terabyte-sized survey data. Two new radio interference mitigation techniques are introduced, as well as a partially-coherent segmented acceleration search algorithm which aims to increase our chances of discovering highly-relativistic short-orbit binary systems, covering a parameter space including potential pulsar-black hole binaries. We show that under a constant acceleration approximation, a ratio of data length over orbital period of ~0.1 results in the highest effectiveness for this search algorithm. From the 50 per cent of data processed thus far, we have re-detected 435 previously known pulsars and discovered a further 60 pulsars, two of which are fast-spinning pulsars with periods less than 30ms. PSR J1101-6424 is a millisecond pulsar whose heavy white dwarf (WD)...

  4. Discovery of Pulsed Gamma Rays from the Young Radio Pulsar PSR J1028-5819 with the Fermi Large Area Telescope

    CERN Document Server

    2009-01-01

    Radio pulsar PSR J1028-5819 was recently discovered in a high-frequency search (at 3.1 GHz)in the error circle of the EGRET source 3EG J1027-5817. The spin-down power of this young pulsar is great enough to make it very likely the counterpart for the EGRET source. We report here the discovery of gamma-ray pulsations from PSR J1028-5819 in early observations by the Large Area Telescope (LAT) on the Fermi Gamma-Ray Space Telescope. The gamma-ray light curve shows two sharp peaks having phase separation of 0.460 +- 0.004, trailing the very narrow radio pulse by 0.200 +- 0.003 in phase, very similar to that of other known $\\gamma$-ray pulsars. The measured gamma-ray flux gives an efficiency for the pulsar of 10-20% (for outer magnetosphere beam models). No evidence of a surrounding pulsar wind nebula is seen in the current Fermi data but limits on associated emission are weak because the source lies in a crowded region with high background emission. However, the improved angular resolution afforded by the LAT ena...

  5. Discovery of Pulsed Gamma Rays from the Young Radio Pulsar PSR J1028-5819 with the Fermi Large Area Telescope

    Energy Technology Data Exchange (ETDEWEB)

    Abdo, Aous A.; /Naval Research Lab, Wash., D.C.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Atwood, W.B.; /UC, Santa Cruz; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Barbiellini, Guido; /INFN, Trieste /Trieste U.; Baring, Matthew G.; /Rice U.; Bastieri, Denis; /INFN, Padua /Padua U.; Baughman, B.M.; /Ohio State U.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bellazzini, R.; /INFN, Pisa; Berenji, B.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bloom, Elliott D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bregeon, J.; /INFN, Pisa; Brez, A.; /INFN, Pisa; Brigida, M.; /Bari U. /INFN, Bari; Bruel, P.; /Ecole Polytechnique; Burnett, Thompson H.; /Washington U., Seattle; Caliandro, G.A.; /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /IASF, Milan /IASF, Milan /DAPNIA, Saclay /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /George Mason U. /Naval Research Lab, Wash., D.C. /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Montpellier U. /Sonoma State U. /Stockholm U., OKC /Royal Inst. Tech., Stockholm /Stockholm U. /Naval Research Lab, Wash., D.C. /INFN, Trieste /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /NASA, Goddard /UC, Santa Cruz /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /CENBG, Gradignan /CENBG, Gradignan /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Montpellier U. /Bari U. /INFN, Bari /Ecole Polytechnique /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Trieste /Hiroshima U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; /more authors..

    2009-05-15

    Radio pulsar PSR J1028-5819 was recently discovered in a high-frequency search (at 3.1 GHz) in the error circle of the Energetic Gamma-Ray Experiment Telescope (EGRET) source 3EG J1027-5817. The spin-down power of this young pulsar is great enough to make it very likely the counterpart for the EGRET source. We report here the discovery of {gamma}-ray pulsations from PSR J1028-5819 in early observations by the Large Area Telescope (LAT) on the Fermi Gamma-Ray Space Telescope. The {gamma}-ray light curve shows two sharp peaks having phase separation of 0.460 {+-} 0.004, trailing the very narrow radio pulse by 0.200 {+-} 0.003 in phase, very similar to that of other known {gamma}-ray pulsars. The measured {gamma}-ray flux gives an efficiency for the pulsar of {approx}10-20% (for outer magnetosphere beam models). No evidence of a surrounding pulsar wind nebula is seen in the current Fermi data but limits on associated emission are weak because the source lies in a crowded region with high background emission. However, the improved angular resolution afforded by the LAT enables the disentanglement of the previous COS-B and EGRET source detections into at least two distinct sources, one of which is now identified as PSR J1028-5819.

  6. An extensive and autonomous deep space navigation system using radio pulsars

    NARCIS (Netherlands)

    Kestillä, A.A.; Engelen, S.; Gill, E.K.A.; Verhoeven, C.J.M.; Bentum, M.J.; Irahhauten, Z.

    2010-01-01

    Interstellar navigation poses significant challenges in all aspects of a spacecraft. One of them is reliable, low-cost, real-time navigation, especially when there is a considerable distance between Earth and the spacecraft in question. In this paper, a complete system for navigation using pulsar ra

  7. Nobel Prize in Physics 1993 "for the discovery of a new type of pulsar, a discovery that has opened up new possibilities for the study of gravitation" : Russell A. Hulse and Joseph H. Taylor Jr.

    CERN Multimedia

    1994-01-01

    Prof. J. H. Taylor Jr. presents "Binary pulsars and relativistic gravity" Spinning freely on their axes, and emitting radio noise detectable over interastellar distances, pulsars make extraordinarily stable natural clocks. Detailed comparisons of""pulsar time" with time kept by atomic clocks on Earth have opened the way for tests of gravity under conditions much more relativistic than found anywhere within the solar system. Among other results,these experiments have demonstrated the existence,quadrupolar nature, and propagation speed of gravitational waves.

  8. Evading the Vainshtein Mechanism with Anomalous Gravitational Wave Speed: Constraints on Modified Gravity from Binary Pulsars

    Science.gov (United States)

    Beltrán Jiménez, Jose; Piazza, Federico; Velten, Hermano

    2016-02-01

    By using observations of the Hulse-Taylor pulsar, we constrain the gravitational wave (GW) speed to the level of 1 0-2 . We apply this result to scalar-tensor theories that generalize Galileon 4 and 5 models, which display anomalous propagation speed and coupling to matter for GWs. We argue that this effect survives conventional screening due to the persistence of a scalar field gradient inside virialized overdensities, which effectively "pierces" the Vainshtein screening. In specific branches of solutions, our result allows us to directly constrain the cosmological couplings in the effective field theory of dark energy formalism.

  9. Swinging between rotation and accretion power in a binary millisecond pulsar

    Directory of Open Access Journals (Sweden)

    Papitto A.

    2014-01-01

    While accreting mass, the X-ray emission of IGR J18245–2452 varies dramatically on time-scales ranging from a second to a few hours. We interpret a state characterised by a lower flux and pulsed fraction, and by sudden increases of the hardness of the X-ray emission, in terms of the onset of a magnetospheric centrifugal inhibition of the accretion flow. Prospects of finding new members of the newly established class of transitional pulsars are also briefly discussed.

  10. Interstellar Medium Effects on Radio Pulsars PSR B1937+21 and PSR B2224+65, and Implications for Gravitational Wave Detection

    Science.gov (United States)

    Dolch, Timothy; Chatterjee, Shami; Cordes, James M.; Paul, Demorest; Halmrast, Daniel; Jessup, Cody; Jones, Glenn; Lam, Michael T.; Lyne, Andrew; McLaughlin, Maura; Ramette, Joshua; Stinebring, Dan; Stappers, Benjamin; Stovall, Kevin

    2017-01-01

    Noise in pulsar timing residuals due to the ionized interstellar medium (IISM) is a critical limiting factor for pulsar timing arrays (PTAs) as gravitational wave detectors. PSR B1937+21 is the brightest millisecond pulsar in the northern sky and serves as a laboratory for studying uncertainties and systematic changes in pulse times-of-arrival. Its high flux, its high degree of scattering along the line-of-sight, and its giant pulses interact in a dynamic way to affect individual times-of-arrival on different timescales. Noise budget results on this pulsar are relevant to understanding the timing of other millisecond pulsars. We present data from an Arecibo Observatory campaign on PSR B1937+21 at 1.4GHz, the standard radio frequency at which the times-of-arrival of PSR B1937+21 and other PTA pulsars are routinely measured for the North American Nanohertz Observatory for Gravitational Waves (NANOGrav). The campaign was strategized to probe the pulsar’s noise budget, particularly with respect to the IISM from high S/N dynamic spectra that show flux distributed irregularly across the bandwidth from interstellar scintillation. Similarly, PSR B2224+65, while not a NANOGrav pulsar, is associated with the Guitar Nebula, a region with significant ISM density fluctuations. We also present data from a Green Bank Telescope monitoring campaign on PSR B2224+65 at 342MHz and 1.4GHz, which uses dispersion measure (DM) variations to constrain the influence of the IISM on the pulsar’s times-of-arrival. By utilizing the dynamic spectra, single pulse, and DM data from these campaigns, we analyze the noise budgets of these pulsars on very short and very long timescales due to the changing intervening IISM.

  11. On the nature of the 'radio-quiet' black hole binaries

    NARCIS (Netherlands)

    Soleri, Paolo; Fender, Rob

    2011-01-01

    The coupling between accretion processes and ejection mechanisms in accreting black holes in binary systems can be investigated by empirical relations between the X-ray/radio and X-ray/optical-infrared luminosities. These correlations are valid over several orders of magnitude and were initially tho

  12. The radio/X-ray domain of black hole X-ray binaries at the lowest radio luminosities

    CERN Document Server

    Gallo, E; Russell, D M; Jonker, P G; Homan, J; Plotkin, R M; Markoff, S; Miller, B P; Corbel, S; Fender, R P

    2014-01-01

    [Abridged] We report on deep, coordinated radio and X-ray observations of the black hole X-ray binary XTE J1118+480 in quiescence. The source was observed with the Karl G. Jansky Very Large Array for a total of 17.5 hrs at 5.3 GHz, yielding a 4.8 \\pm 1.4 microJy radio source at a position consistent with the binary system. At a distance of 1.7 kpc, this corresponds to an integrated radio luminosity between 4-8E+25 erg/s, depending on the spectral index. This is the lowest radio luminosity measured for any accreting black hole to date. Simultaneous observations with the Chandra X-ray Telescope detected XTE J1118+480 at 1.2E-14 erg/s/cm^2 (1-10 keV), corresponding to an Eddington ratio of ~4E-9 for a 7.5 solar mass black hole. Combining these new measurements with data from the 2005 and 2000 outbursts available in the literature, we find evidence for a relationship of the form ellr=alpha+beta*ellx (where ell denotes logarithmic luminosities), with beta=0.72\\pm0.09. XTE J1118+480 is thus the third system, togeth...

  13. THERMAL ABSORPTION AS THE CAUSE OF GIGAHERTZ-PEAKED SPECTRA IN PULSARS AND MAGNETARS

    Energy Technology Data Exchange (ETDEWEB)

    Lewandowski, Wojciech; Rożko, Karolina; Kijak, Jarosław; Melikidze, George I., E-mail: boe@astro.ia.uz.zgora.pl [Institute of Astronomy, University of Zielona Gora, Szafrana 2, 65-516 Zielona Gora (Poland)

    2015-07-20

    We present a model that explains the observed deviation of the spectra of some pulsars and magnetars from the power-law spectra that are seen in the bulk of the pulsar population. Our model is based on the assumption that the observed variety of pulsar spectra can be naturally explained by the thermal free–free absorption that takes place in the surroundings of the pulsars. In this context, the variety of the pulsar spectra can be explained according to the shape, density, and temperature of the absorbing media and the optical path of the line of sight across it. We have put specific emphasis on the case of the radio magnetar SGR J1745–2900 (also known as the Sgr A* magnetar), modeling the rapid variations of the pulsar spectrum after the outburst of 2013 April as due to the free–free absorption of the radio emission in the electron material ejected during the magnetar outburst. The ejecta expands with time and consequently the absorption rate decreases and the shape of the spectrum changes in such a way that the peak frequency shifts toward the lower radio frequencies. In the hypothesis of an absorbing medium, we also discuss the similarity between the spectral behavior of the binary pulsar B1259–63 and the spectral peculiarities of isolated pulsars.

  14. Radio Observations as a Tool to Investigate Shocks and Asymmetries in Accreting White Dwarf Binaries

    Science.gov (United States)

    Weston, Jennifer Helen Seng; E-Nova Project

    2017-01-01

    In this dissertation, I use radio observations with the Karl G. Jansky Very Large Array (VLA) to reveal that colliding flows within the ejecta from nova explosions can lead to shocks that accelerate particles and produce radio synchrotron emission. In both novae V1723 Aql and V5589 Sgr, radio emission within the first one to two months deviated strongly from the classic thermal model for radio emission from novae. Three years of radio observations of V1723 Aql show that multiple outflows from the system collided to create non-thermal shocks with a brightness temperature of >106 K. After these shocks faded, the radio light curve became roughly consistent with an expanding thermal shell. However, resolved images of V1723 Aql show elongated material that apparently rotates its major axis over the course of 15 months. In the case of nova V5589 Sgr, I show that the early radio emission is dominated by a shock-powered non-thermal flare that produces strong (kTx > 33 keV) X-rays. These findings have important implications for understanding how normal novae generate GeV gamma-rays.Additionally, I present VLA observations of the symbiotic star CH Cyg and two small surveys of symbiotic binaries. Radio observations of CH Cyg tie the ejection of a collimated jet to a change of state in the accretion disk, strengthening the link between bipolar outflows from accreting white dwarfs and other types of accreting compact objects. Next, I use a survey of eleven accretion-driven symbiotic binaries to determine that the radio brightness of a symbiotic system could potentially be used as an indicator of whether it is powered predominantly by shell burning on the surface of the white dwarf or by accretion. This survey also produces the first radio detections of seven of the target systems. In the second survey of seventeen symbiotic binaries, I spatially resolve extended radio emission in several systems for the first time. The results from these surveys provide some support for the

  15. Radio emission of the Galactic X-rays binaries with relativistic jets

    CERN Document Server

    Trushkin, S A

    2000-01-01

    Variable non-thermal radio emission from Galactic X-ray binaries is a trace of relativistic jets, created near accretion disks. The spectral characteristics of a lot of radio flares in the X-ray binaries with jets (RJXB) is discussed in this report. We carried out several long daily monitoring programs with the RATAN-600 radio telescope of the sources: SS433, Cyg X-3, LSI+61o303, GRS 1915+10 and some others. We also reviewed some data from the GBI monitoring program at two frequencies and hard X-ray BATSE (20-100 keV) and soft X-ray RTXE (2-12 keV) ASM data. We confirmed that flaring radio emission of Cyg X-3 correlated with hard and anti-correlated with soft X-ray emission during the strong flare (>$ Jy) in May 1997. During two orbital periods we investigated radio light curves of the remarkable X-binary LSI+61o303. Two flaring events near a phase 0.6 of the 26.5-day orbital period have been detected for first time at four frequencies simultaneously. Powerful flaring events of SS433 were detected at six freq...

  16. Distribution of inhomogeneities in the interstellar plasma in the directions of three distant pulsars from observations with the RadioAstron ground-space interferometer

    Science.gov (United States)

    Popov, M. V.; Andrianov, A. S.; Bartel, N.; Gwinn, C.; Joshi, B. C.; Jauncey, D.; Kardashev, N. S.; Rudnitskii, A. G.; Smirnova, T. V.; Soglasnov, V. A.; Fadeev, E. N.; Shishov, V. I.

    2016-09-01

    The RadioAstron ground-space interferometer has been used to measure the angular sizes of the scattering disks of the three distant pulsars B1641-45, B1749-28, and B1933+16. The observations were carried out with the participation of the Westerbork Synthesis Radio Telescope; two 32-m telescopes at Torun, Poland and Svetloe, Russia (the latter being one antenna of the KVAZAR network); the Saint Croix VLBA antenna; the Arecibo radio telescope; the Parkes, Narrabri (ATCA), Mopra, Hobart, and Ceduna Australian radio telescopes; and the Hartebeesthoek radio telescope in South Africa. The full widths at half maximum of the scattering disks were 27 mas at 1668 MHz for B1641-45, 0.5 mas at 1668 MHz for B1749-28, and 12.3 at 316 MHz and 0.84 mas at 1668 MHz for B1933+16. The characteristic time scales for scatter-broadening of the pulses on inhomogeneities in the interstellar plasma τsc were also measured for these pulsars using various methods. Joint knowledge of the size of the scattering disk and the scatter-broadening time scale enables estimation of the distance to the effective scattering screen d. For B1641-45, d = 3.0 kpc for a distance to the pulsar D = 4.9 kpc, and for B1749-28, d = 0.95 kpc for D = 1.3 kpc. Observations of B1933+16 were carried out simultaneously at 316 and 1668 MHz. The positions of the screen derived using the measurements at the two frequencies agree: d 1 = 2.6 and d 2 = 2.7 kpc, for a distance to the pulsar of 3.7 kpc. Two screens were detected for this pulsar from an analysis of parabolic arcs in the secondary dynamic spectrum at 1668 MHz, at 1.3 and 3.1 kpc. The scattering screens for two of the pulsars are identified with real physical objects located along the lines of sight toward the pulsars: G339.1-04 (B1641-45) and G0.55-0.85 (B1749-28).

  17. The origin of the frequency-dependent behaviour of pulsar radio profiles

    CERN Document Server

    Dyks, J

    2014-01-01

    We present further development of a pulsar emission model based on multiple streams diverging away from the magnetic dipole axis, and forming azimuthally-structured fan-shaped beams. It is shown that this geometry, successfully tested on profiles with bifurcated features, naturally solves several classical pulsar problems and avoids some difficulties of the traditional nested cone/core model. This is best visible for profiles with several components, such as those of class T, Q and M, because they most clearly exhibit a range of effects previously interpreted within the conal model. In particular, with no reference to the flaring boundary of the polar magnetic flux tube, the stream model explains the apparent radius-to-frequency mapping (RFM), including its reduced strength for the inner pair of components. The lag of the central component (apparent `core') with respect to the centroids of the flanking (`conal') components can also be naturally explained with no reference to emission rings located at disparat...

  18. Investigating the magnetic inclination angle distribution of $\\gamma$-ray-loud radio pulsars

    CERN Document Server

    Rookyard, S C; Johnston, S

    2014-01-01

    Several studies have shown the distribution of pulsars' magnetic inclination angles to be skewed towards low values compared with the distribution expected if the rotation and magnetic axes are placed randomly on the star. Here we focus on a sample of 28 $\\gamma$-ray-detected pulsars using data taken as part of the Parkes telescope's \\emph{FERMI} timing program. In doing so we find a preference in the sample for low magnetic inclination angles, $\\alpha$, in stark contrast to both the expectation that the magnetic and rotation axes are orientated randomly at the birth of the pulsar and to $\\gamma$-ray-emission-model-based expected biases. In this paper, after exploring potential explanations, we conclude that there are two possible causes of this preference, namely that low $\\alpha$ values are intrinsic to the sample, or that the emission regions extend outside what is traditionally thought to be the open-field-line region in a way which is dependent on the magnetic inclination. Each possibility is expected to...

  19. Discovery of the optical counterparts to four energetic Fermi millisecond pulsars

    Energy Technology Data Exchange (ETDEWEB)

    Breton, R. P. [School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ (United Kingdom); Van Kerkwijk, M. H. [Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4 (Canada); Roberts, M. S. E. [Eureka Scientific Inc., 2452 Delmer Street, Suite 100, Oakland, CA 94602-3017 (United States); Hessels, J. W. T. [ASTRON, The Netherlands Institute for Radio Astronomy, Postbus 2, 7990-AA Dwingeloo (Netherlands); Camilo, F. [Columbia Astrophysics Laboratory, Columbia University, 550 West, 120th Street, New York, NY 10027 (United States); McLaughlin, M. A. [Department of Physics, White Hall, West Virginia University, Morgantown, WV 26506 (United States); Ransom, S. M. [National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States); Ray, P. S. [Space Science Division, Naval Research Laboratory, Code 7655, 4555 Overlook Avenue SW, Washington, DC 20375 (United States); Stairs, I. H., E-mail: r.breton@soton.ac.uk [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1 (Canada)

    2013-06-01

    In the last few years, over 43 millisecond radio pulsars have been discovered by targeted searches of unidentified γ-ray sources found by the Fermi Gamma-Ray Space Telescope. A large fraction of these millisecond pulsars are in compact binaries with low-mass companions. These systems often show eclipses of the pulsar signal and are commonly known as black widows and redbacks because the pulsar is gradually destroying its companion. In this paper, we report on the optical discovery of four strongly irradiated millisecond pulsar companions. All four sources show modulations of their color and luminosity at the known orbital periods from radio timing. Light curve modeling of our exploratory data shows that the equilibrium temperature reached on the companion's dayside with respect to their nightside is consistent with about 10%-30% of the available spin-down energy from the pulsar being reprocessed to increase the companion's dayside temperature. This value compares well with the range observed in other irradiated pulsar binaries and offers insights about the energetics of the pulsar wind and the production of γ-ray emission. In addition, this provides a simple way of estimating the brightness of irradiated pulsar companions given the pulsar spin-down luminosity. Our analysis also suggests that two of the four new irradiated pulsar companions are only partially filling their Roche lobe. Some of these sources are relatively bright and represent good targets for spectroscopic follow-up. These measurements could enable, among other things, mass determination of the neutron stars in these systems.

  20. X-ray measurement of the spin-down of CalverA: A radio- and gamma-ray-quiet pulsar

    Energy Technology Data Exchange (ETDEWEB)

    Halpern, J. P.; Bogdanov, S.; Gotthelf, E. V., E-mail: jules@astro.columbia.edu [Columbia Astrophysics Laboratory, Columbia University, 550 West 120th Street, New York, NY 10027-6601 (United States)

    2013-12-01

    We measure spin-down of the 59 ms X-ray pulsar Calvera by comparing the XMM-Newton discovery data from 2009 with new Chandra timing observations taken in 2013. Its period derivative is P-dot =(3.19± 0.08)×10{sup −15}, which corresponds to spin-down luminosity E-dot =6.1×10{sup 35} erg s{sup –1}, characteristic age τ{sub c}≡P/2 P-dot =2.9×10{sup 5} yr, and surface dipole magnetic field strength B{sub s} = 4.4 × 10{sup 11} G. These values rule out a mildly recycled pulsar, but Calvera could be an orphaned central compact object (anti-magnetar), with a magnetic field that was initially buried by supernova debris and is now reemerging and approaching normal strength. We also performed unsuccessful searches for high-energy γ-rays from Calvera in both imaging and timing of >100 MeV Fermi photons. Even though the distance to Calvera is uncertain by an order of magnitude, an upper limit of d < 2 kpc inferred from X-ray spectra implies a γ-ray luminosity limit of <3.3 × 10{sup 32} erg s{sup –1}, which is less than that of any pulsar of comparable E-dot . Calvera shares some properties with PSR J1740+1000, a young radio pulsar that we show by virtue of its lack of proper motion was born outside of the Galactic disk. As an energetic, high-Galactic-latitude pulsar, Calvera is unique in being undetected in both radio and γ-rays to faint limits, which should place interesting constraints on models for particle acceleration and beam patterns in pulsar magnetospheres.

  1. Merger of a White Dwarf-Neutron Star Binary to $10^{29}$ Carat Diamonds: Origin of the Pulsar Planets

    CERN Document Server

    Margalit, Ben

    2016-01-01

    We show that the merger and tidal disruption of a C/O white dwarf (WD) by a neutron star (NS) binary companion provides a natural formation scenario for the PSR B1257+12 planetary system. Starting with initial conditions for the debris disk produced of the disrupted WD, we model its long term viscous evolution, including for the first time the effects of mass and angular momentum loss during the early radiatively inefficient accretion flow (RIAF) phase and accounting for the unusual C/O composition on the disk opacity. For plausible values of the disk viscosity $\\alpha \\sim 10^{-3}-10^{-2}$ and the RIAF mass loss efficiency, we find that the disk mass remaining near the planet formation radius at the time of solid condensation is sufficient to explain the pulsar planets. Rapid rocky planet formation via gravitational instability of the solid carbon-dominated disk is facilitated by the suppression of vertical shear instabilities due to the high solid-to-gas ratio. Additional evidence supporting a WD-NS merger ...

  2. Low Mass X-Ray Binaries in the Inner Galaxy: Implications for Millisecond Pulsars and the GeV Excess

    Energy Technology Data Exchange (ETDEWEB)

    Haggard, Daryl; Heinke, Craig; Hooper, Dan; Linden, Tim

    2017-01-10

    If millisecond pulsars (MSPs) are responsible for the excess gamma-ray emission observed from the region surrounding the Galactic Center, the same region should also contain a large population of low-mass X-ray binaries (LMXBs). In this study, we compile and utilize a sizable catalog of LMXBs observed in the the Milky Way's globular cluster system and in the Inner Galaxy, as well as the gamma-ray emission observed from globular clusters, to estimate the flux of gamma rays predicted from MSPs in the Inner Galaxy. From this comparison, we conclude that only up to $\\sim$4-23% of the observed gamma-ray excess is likely to originate from MSPs. This result is consistent with, and more robust than, previous estimates which utilized smaller samples of both globular clusters and LMXBs. If MSPs had been responsible for the entirety of the observed excess, INTEGRAL should have detected $\\sim$$10^3$ LMXBs from within a $10^{\\circ}$ radius around the Galactic Center, whereas only 42 LMXBs (and 46 additional LMXB candidates) have been observed.

  3. Search for a correlation between very-high-energy gamma rays and giant radio pulses in the Crab pulsar

    CERN Document Server

    Aliu, E; Arlen, T; Aune, T; Beilicke, M; Benbow, W; Bouvier, A; Buckley, J H; Bugaev, V; Byrum, K; Cesarini, A; Ciupik, L; Collins-Hughes, E; Connolly, M P; Cui, W; Dickherber, R; Duke, C; Dumm, J; Falcone, A; Federici, S; Feng, Q; Finley, J P; Finnegan, G; Fortson, L; Furniss, A; Galante, N; Gall, D; Gillanders, G H; Godambe, S; Griffin, S; Grube, J; Gyuk, G; Hanna, D; Holder, J; Huan, H; Hughes, G; Humensky, T B; Kaaret, P; Karlsson, N; Khassen, Y; Kieda, D; Krawczynski, H; Krennrich, F; Lang, M J; LeBohec, S; Lee, K; Lyutikov, M; Madhavan, A S; Maier, G; Majumdar, P; McArthur, S; McCann, A; Moriarty, P; Mukherjee, R; Nelson, T; de Bhroithe, A O'Faolain; Ong, R A; Orr, M; Otte, A N; Park, N; Perkins, J S; Pohl, M; Prokoph, H; Quinn, J; Ragan, K; Reyes, L C; Reynolds, P T; Roache, E; Saxon, D B; Schroedter, M; Sembroski, G H; Senturk, G D; Smith, A W; Staszak, D; Telezhinsky, I; Tesic, G; Theiling, M; Thibadeau, S; Tsurusaki, K; Varlotta, A; Vincent, S; Vivier, M; Wagner, R G; Wakely, S P; Weekes, T C; Weinstein, A; Welsing, R; Williams, D A; Zitzer, B; Kondratiev, V

    2012-01-01

    We present the results of a joint observational campaign between the Green Bank radio telescope and the VERITAS gamma-ray telescope, which searched for a correlation between the emission of very-high-energy (VHE) gamma rays ($E_{\\gamma} >$ 150 GeV) and Giant Radio Pulses (GRPs) from the Crab pulsar at 8.9 GHz. A total of 15366 GRPs were recorded during 11.6 hours of simultaneous observations, which were made across four nights in December 2008 and in November and December 2009. We searched for an enhancement of the pulsed gamma-ray emission within time windows placed around the arrival time of the GRP events. In total, 8 different time windows with durations ranging from 0.033 ms to 72 s were positioned at three different locations relative to the GRP to search for enhanced gamma-ray emission which lagged, led, or was concurrent with, the GRP event. Further, we performed separate searches on main pulse GRPs and interpulse GRPs and on the most energetic GRPs in our data sample. No significant enhancement of pu...

  4. Can we see pulsars around Sgr A*? - The latest searches with the Effelsberg telescope

    CERN Document Server

    Eatough, R P; Klein, B; Karuppusamy, R; Champion, D J; Freire, P C C; Wex, N; Liu, K

    2012-01-01

    Radio pulsars in relativistic binary systems are unique tools to study the curved space-time around massive compact objects. The discovery of a pulsar closely orbiting the super-massive black hole at the centre of our Galaxy, Sgr A*, would provide a superb test-bed for gravitational physics. To date, the absence of any radio pulsar discoveries within a few arc minutes of Sgr A* has been explained by one principal factor: extreme scattering of radio waves caused by inhomogeneities in the ionized component of the interstellar medium in the central 100 pc around Sgr A*. Scattering, which causes temporal broadening of pulses, can only be mitigated by observing at higher frequencies. Here we describe recent searches of the Galactic centre region performed at a frequency of 18.95 GHz with the Effelsberg radio telescope.

  5. Radio Observations as a Tool to Investigate Shocks and Asymmetries in Accreting White Dwarf Binaries

    Science.gov (United States)

    Weston, Jennifer H. S.

    2016-07-01

    This dissertation uses radio observations with the Karl G. Jansky Very Large Array (VLA) to investigate the mechanisms that power and shape accreting white dwarfs (WD) and their ejecta. We test the predictions of both simple spherical and steady-state radio emission models by examining nova V1723 Aql, nova V5589 Sgr, symbiotic CH Cyg, and two small surveys of symbiotic binaries. First, we highlight classical nova V1723 Aql with three years of radio observations alongside optical and X-ray observations. We use these observations to show that multiple outflows from the system collided to create early non-thermal shocks with a brightness temperature of ≥106 K. While the late-time radio light curve is roughly consistent an expanding thermal shell of mass 2x10-4 M⊙ solar masses, resolved images of V1723 Aql show elongated material that apparently rotates its major axis over the course of 15 months, much like what is seen in gamma-ray producing nova V959 Mon, suggesting similar structures in the two systems. Next, we examine nova V5589 Sgr, where we find that the early radio emission is dominated by a shock-powered non-thermal flare that produces strong (kTx > 33 keV) X-rays. We additionally find roughly 10-5 M⊙ solar masses of thermal bremsstrahlung emitting material, all at a distance of ~4 kpc. The similarities in the evolution of both V1723 Aql and V5589 Sgr to that of nova V959 Mon suggest that these systems may all have dense equatorial tori shaping faster flows at their poles. Turning our focus to symbiotic binaries, we first use our radio observations of CH Cyg to link the ejection of a collimated jet to a change of state in the accretion disk. We additionally estimate the amount of mass ejected during this period (10-7 M⊙ masses), and improve measurements of the period of jet precession (P=12013 ± 74 days). We then use our survey of eleven accretion-driven symbiotic systems to determine that the radio brightness of a symbiotic system could potentially

  6. RADIO POLARIZATION OBSERVATIONS OF THE SNAIL: A CRUSHED PULSAR WIND NEBULA IN G327.1–1.1 WITH A HIGHLY ORDERED MAGNETIC FIELD

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Y. K.; Ng, C.-Y. [Department of Physics, The University of Hong Kong, Pokfulam Road (Hong Kong); Bucciantini, N. [INAF—Osservatorio Astrofisico di Arcetri, L.go E. Fermi 5, I-50125 Firenze (Italy); Slane, P. O. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Gaensler, B. M. [Dunlap Institute for Astronomy and Astrophysics, The University of Toronto, Toronto, ON M5S 3H4 (Canada); Temim, T., E-mail: ncy@bohr.physics.hku.hk [Observational Cosmology Lab, Code 665, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2016-04-01

    Pulsar wind nebulae (PWNe) are suggested to be acceleration sites of cosmic rays in the Galaxy. While the magnetic field plays an important role in the acceleration process, previous observations of magnetic field configurations of PWNe are rare, particularly for evolved systems. We present a radio polarization study of the “Snail” PWN inside the supernova remnant G327.1−1.1 using the Australia Telescope Compact Array. This PWN is believed to have been recently crushed by the supernova (SN) reverse shock. The radio morphology is composed of a main circular body with a finger-like protrusion. We detected a strong linear polarization signal from the emission, which reflects a highly ordered magnetic field in the PWN and is in contrast to the turbulent environment with a tangled magnetic field generally expected from hydrodynamical simulations. This could suggest that the characteristic turbulence scale is larger than the radio beam size. We built a toy model to explore this possibility, and found that a simulated PWN with a turbulence scale of about one-eighth to one-sixth of the nebula radius and a pulsar wind filling factor of 50%–75% provides the best match to observations. This implies substantial mixing between the SN ejecta and pulsar wind material in this system.

  7. X-ray states of redback millisecond pulsars

    CERN Document Server

    Linares, Manuel

    2014-01-01

    Compact binary millisecond pulsars with main-sequence donors, often referred to as "redbacks", constitute the long-sought link between low-mass X-ray binaries and millisecond radio pulsars, and offer a unique probe of the interaction between pulsar winds and accretion flows. We present a systematic study of eight nearby redbacks, using more than 100 observations obtained with Swift's X-ray Telescope. We distinguish between three main states: pulsar, disk and outburst states. We find X-ray mode switching in the disk state of PSR J1023+0038 and XSS J12270-4859, similar to what was found in the other redback which showed evidence for accretion: rapid, recurrent changes in X-ray luminosity (0.5-10 keV, L$_\\mathrm{X}$), between [6-9]$\\times$10$^{32}$ erg s$^{-1}$ (disk-passive state) and [3-5]$\\times$10$^{33}$ erg s$^{-1}$ (disk-active state). This strongly suggests that mode switching $-$which has not been observed in quiescent low-mass X-ray binaries$-$ is universal among redback millisecond pulsars in the disk ...

  8. A large spin-up rate measured with INTEGRAL in the High Mass X-ray Binary Pulsar SAXJ2103.5+4545

    CERN Document Server

    Sidoli, L; Larsson, S; Chernyakova, M; Kreykenbohm, I; Kretschmar, P; Paizis, A; Santangelo, A; Ferrigno, C; Falanga, M

    2005-01-01

    The High Mass X-ray Binary Pulsar SAXJ2103.5+4545 has been observed with INTEGRAL several times during the last outburst in 2002-2004. We report a comprehensive study of all INTEGRAL observations, allowing a study of the pulse period evolution during the recent outburst. We measured a very rapid spin-up episode, lasting 130days, which decreased the pulse period by 1.8s. The spin-up rate, pdot=-1.5e-7 s/s, is the largest ever measured for SAXJ2103.5+4545, and it is among the fastest for an accreting pulsar. The pulse profile shows evidence for temporal variability, apparently not related to the source flux or to the orbital phase. The X-ray spectrum is hard and there is significant emission up to 150keV. A new derivation of the orbital period, based on RXTE data, is also reported.

  9. X-ray pulsar rush in 1998

    Energy Technology Data Exchange (ETDEWEB)

    Imanishi, K.; Tsujimoto, K.; Nishiuchi, Mamiko; Yokogawa, J.; Koyama, K. [Kyoto Univ., Faculty of Science, Kyoto (Japan)

    1999-08-01

    We present recent remarkable topics about discoveries of X-ray pulsars. 1. Pulsations from two Soft Gamma-ray Repeaters: These pulsars have enormously strong magnetic field (B {approx} 10{sup 15} G), thus these are called as 'magnetar', new type of X-ray pulsars. 2. New Crab-like pulsars: These discoveries lead to suggesting universality of Crab-like pulsars. 3. An X-ray bursting millisecond pulsar: This is strong evidence for the recycle theory of generating radio millisecond pulsars. 4. X-ray pulsar rush in the SMC: This indicates the younger star formation history in the SMC. (author)

  10. MERLIN radio detection of an interaction zone within a binary Orion proplyd system

    CERN Document Server

    Graham, M F; Garrington, S T; O'Brien, T J; Henney, W J; O'Dell, C R

    2002-01-01

    Presented here are high angular resolution MERLIN 5 GHz (6 cm) continuum observations of the binary proplyd system, LV 1 in the Orion nebula, which consists of proplyd 168--326SE and its binary proplyd companion 168--326NW (separation 0.4 arcsec). Accurate astrometric alignment allows a detailed comparison between these data and published HST PC Halpha and [Oiii] images. Thermal radio sources coincide with the two proplyds and originate in the ionized photoevaporating flows seen in the optical emission lines. Flow velocities of approx 50 km/s from the ionized proplyd surfaces and \\geq 100 km/s from a possible micro-jet have been detected using the Manchester Echelle spectrometer. A third radio source is found to coincide with a region of extended, high excitation, optical line emission that lies between the binary proplyds 168--326SE/326NW . This is modelled as a bowshock due to the collision of the photoevaporating flows from the two proplyds. Both a thermal and a non-thermal origin for the radio emission in...

  11. The optical companion to the binary millisecond pulsar J1824-2452H in the globular cluster M28

    CERN Document Server

    Pallanca, C; Ferraro, F R; Lanzoni, B; Rood, R T; Possenti, A; D'Amico, N; Freire, P C; Stairs, I; Ransom, S M; Begin, S

    2010-01-01

    We report on the optical identification of the companion star to the eclipsing millisecond pulsar PSR J1824-2452H in the galactic globular cluster M28 (NGC 6626). This star is at only 0.2" from the nominal position of the pulsar and it shows optical variability (~ 0.25 mag) that nicely correlates with the pulsar orbital period. It is located on the blue side of the cluster main sequence, ~1.5 mag fainter than the turn-off point. The observed light curve shows two distinct and asymmetric minima, suggesting that the companion star is suffering tidal distortion from the pulsar. This discovery increases the number of non-degenerate MSP companions optically identified so far in globular clusters (4 out of 7), suggesting that these systems could be a common outcome of the pulsar recycling process, at least in dense environments where they can be originated by exchange interactions.

  12. A radio map of the colliding winds in the very massive binary system HD 93129A

    Science.gov (United States)

    Benaglia, P.; Marcote, B.; Moldón, J.; Nelan, E.; De Becker, M.; Dougherty, S. M.; Koribalski, B. S.

    2015-07-01

    Context. Radio observations are an effective tool for discovering particle acceleration regions in colliding-wind binaries through detection of synchrotron radiation. Wind-collision region (WCR) models can reproduce the radio continuum spectra of massive binaries. However, key constraints for models come from high-resolution imaging. Only five WCRs have been resolved to date at radio frequencies on milliarcsec (mas) angular scales. The source HD 93129A, a prototype of the very few known O2 I stars, is a promising target for study. Recently, a second massive, early-type star about 50 mas away was discovered, and a non-thermal radio source was detected in the region. Preliminary long-baseline array data suggest that a significant fraction of the radio emission from the system comes from a putative WCR. Aims: We seek evidence that HD 93129A is a massive binary system with colliding stellar winds that produce non-thermal radiation through spatially resolved images of the radio emitting regions. Methods: We completed observations with the Australian Long Baseline Array (LBA) to resolve the system at mas angular resolutions and reduced archival Australia Telescope Compact Array (ATCA) data to derive the total radio emission. We also compiled optical astrometric data of the system in a homogeneous way. We reduced historical Hubble Space Telescope data and obtained absolute and relative astrometry with milliarcsec accuracy. Results: The astrometric analysis leads us to conclude that the two stars in HD 93129A form a gravitationally bound system. The LBA data reveal an extended arc-shaped non-thermal source between the two stars, which is indicative of a WCR. The wind momentum-rate ratio of the two stellar winds is estimated. The ATCA data show a point source with a change in flux level between 2003-4 and 2008-9, which is modeled with a non-thermal power-law spectrum with spectral indices of -1.03 ± 0.09 and -1.21 ± 0.03, respectively. The mass-loss rates derived from the

  13. Study of luminosity and spin-up relation in X-ray binary pulsars with long-term monitoring by MAXI/GSC and Fermi/GBM

    CERN Document Server

    Sugizaki, Mutsumi; Nakajima, Motoki; Yamaoka, Kazutaka

    2015-01-01

    We study the relation between luminosity and spin-period change in X-ray binary pulsars using long-term light curve obtained by the MAXI/GSC all-sky survey and pulse period data from the Fermi/GBM pulsar project. X-ray binaries, consisting of a highly magnetized neutron star and a stellar companion, originate X-ray emission according to the energy of the accretion matter onto the neutron star. The accretion matter also transfers the angular momentum at the Alfven radius, and then spin up the neutron star. Therefore, the X-ray luminosity and the spin-up rate are supposed to be well correlated. We analyzed the luminosity and period-change relation using the data taken by continuous monitoring of MAXI/GSC and Fermi/GBM for Be/X-ray binaries, GX 304$-$1, A 0535$+$26, GRO J1008$-$57, KS 1947$+$300, and 2S 1417$-$624, which occurred large outbursts in the last four years. We discuss the results comparing the obtained observed relation with that of the theoretical model by Ghosh \\& Lamb (1979).

  14. Near-infrared observations of the Be/X-ray binary pulsar A0535+262

    Institute of Scientific and Technical Information of China (English)

    Sachindra Naik; Blesson Mathew; D. P. K. Banerjee; N. M. Ashok; Rajeev R. Jaiswal

    2012-01-01

    We present the results obtained from extensive near-infrared (IR) spectro-scopic and photometric observations of the Be/X-ray binary A0535+262/HDE 245770 at different phases of its ~ 111 d orbital period.This observation campaign is part of the monitoring program of selective Be/X-ray binary systems aimed at understanding X-ray and near-IR properties at different orbital phases,especially during the periastron passage of the neutron star.The near-IR observations presented here were carried out using the 1.2 m telescope at the Mt.Abu IR Observatory.Though the source was relatively faint for spectroscopic observations with the 1.2 m telescope,we monitored the source closely during the 2011 February-March giant X-ray outburst to primarily investigate whether any drastic changes in the near-IR JHK spectra took place at the periastron passage.Changes of such a striking nature were expected to be detectable in our spectra.Photometric observations of the Be star show a gradual and systematic fading in the JHK light curves since the onset of the X-ray outburst,which could suggest a mild evacuation/truncation of the circumstellar disk of the Be companion.Near-IR spectroscopy of the object shows that the JHK spectra are dominated by the emission lines of hydrogen Brackett and Paschen series and HeI lines at 1.0830,1.7002 and 2.0585 μm.The presence of all the hydrogen emission lines in the JHK spectra,along with the absence of any significant change in the continuum of the Be companion during X-ray quiescent and X-ray outburst phases,suggests that the near- IR line emitting regions of the disk are not significantly affected during the X-ray outburst.

  15. An X-ray Synchrotron Nebula Associated with the Radio Pulsar PSR B1853+01 in the Supernova Remnant W44

    Science.gov (United States)

    Harrus, I.; Hughes, J. P.

    1995-12-01

    We present results of a study using ASCA X-ray data from the vicinity of the radio pulsar PSR B1853+01 located within the supernova remnant (SNR) W44. PSR B1853+01 is a 267 ms pulsar, which to date has only been detected in the radio band. Previous observations at soft X-ray energies (e.g., ROSAT HRI) have failed to detect any significant X-ray emission (pulsed or unpulsed) from the pulsar. In addition, no high energy tail was seen in the Ginga spectrum of W44 leading to a 3sigma upper limit of 3.6x 10(-12) ergs cm(-2) s(-1) for the 2--10 keV flux of a Crab-like power-law component contributing to the spectrum of W44. Over the 0.5--5 keV band, the ASCA data show soft thermal (kT ~ 0.5 keV) emission from W44 with a morphology very similar to that observed before by Einstein and ROSAT. In the high energy band (5--10 keV) the SNR for the most part is not visible and instead an unresolved source coincident with the position of PSR B1853+01 is evident. The observed ASCA spectra are consistent with a power-law origin (photon index ~ 3.5) for the X-ray emission from this source at a flux level below the Ginga upper limit. The maximum allowed size for the source is determined directly from the ASCA data (1.5(') ). We also report on our timing analysis, which failed to detect pulsations from the X-ray source at the pulsar's period. Based on these lines of evidence, we suggest that the new hard source in W44 represents the X-ray synchrotron nebula surrounding PSR B1853+01, rather than the beamed output of the pulsar itself. The ratio of the nebula's X-ray luminosity to the spin-down energy loss of the pulsar is consistent with that of other known plerions, lending further support to our interpretation. This is the first indirect detection in the X-ray band of the pulsar associated with W44.

  16. Pulsar Candidates Toward Fermi Unassociated Sources

    CERN Document Server

    Frail, D A; Jagannathan, P; Intema, H T

    2016-01-01

    We report on a search for steep spectrum radio sources within the 95% confidence error ellipses of the Fermi unassociated sources from the Large Array Telescope (LAT). Using existing catalogs and the newly released GMRT all-sky survey at 150 MHz we identify compact radio sources that are bright at MHz frequencies but faint or absent at GHz frequencies. Such steep spectrum radio sources are rare and constitute a sample of pulsar candidates, selected independently of period, dispersion measure, interstellar scattering and orbital parameters. We find point-like, steep spectrum candidates toward 11 Fermi sources. Based on the gamma-ray/radio positional coincidence, the rarity of such radio sources, and the properties of the 3FGL sources themselves, we argue that many of these sources could be pulsars. They may have been missed by previous radio periodicity searches due to interstellar propagation effects or because they lie in an unusually tight binary. If this hypothesis is correct, then renewed gamma-ray and ra...

  17. Modelling interaction of relativistic and non-relativistic winds in binary system PSR B1259-63/SS2883 - II. Impact of magnetization and anisotropy of the pulsar wind

    CERN Document Server

    Bogovalov, S; Koldoba, A V; Ustyugova, G V; Aharonian, F A

    2011-01-01

    In this paper, we present a numerical study of the properties of the flow produced by the collision of a magnetized anisotropic pulsar wind with its environment in binary system. We compare the impact of both the magnetic field and the wind anisotropy to the benchmark case of a purely hydrodynamical (HD) interaction of isotropic winds, which has been studied in detail by Bogovalov et al. (2008). We consider the interaction in axisymmetric approximation, i.e. the pulsar rotation axis is assumed to be oriented along the line between the pulsar and the optical star and the effects related to the pulsar orbiting are neglected. The impact of the magnetic field is studied for the case of weak magnetization (with magnetization parameter $\\sigma<0.1$), which is consistent with conventional models of pulsar winds. The effects related to anisotropy in pulsar winds are modeled assuming that the kinetic energy flux in a non-magnetized pulsar wind is strongly anisotropic, with the minimum at the pulsar rotation axis an...

  18. Astronomers Discover Fastest-Spinning Pulsar

    Science.gov (United States)

    2006-01-01

    pulsars. Giant stars explode as supernovae and leave rotating pulsars which gradually slow down. However, if a pulsar has a companion star from which it can draw material, that incoming material imparts its spin, or angular momentum, to the pulsar. As a result, the pulsar spins faster. "In a dense cluster, interactions between the stars will create more binary pairs that can yield more fast-rotating pulsars," Ransom said. The great sensitivity of the giant, 100-meter diameter GBT, along with a special signal processor, called the Pulsar Spigot, made possible the discovery of so many millisecond pulsars in Terzan 5. "We think there are many more pulsars to be found in Terzan 5 and other clusters, and given that the fast ones are often hidden by eclipses, some of them may be spinning even faster than this new one," Ransom said. "We're excited about using this outstanding new telescope to answer some important questions about fundamental physics," he said. In addition to Hessels, Ransom and Stairs, the research team includes Paulo Freire of Arecibo Observatory in Puerto Rico, Victoria Kaspi, of McGill University, and Fernando Camilo, of Columbia University. Their report is being published in Science Express, the online version of the journal Science. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. The pulsar research also was supported by the Canada Foundation for Innovation, the Natural Sciences and Engineering Research Council of Canada, the Quebec Foundation for Research on Nature and Technology, the Canadian Institute for Advanced Research, the Canada Research Chairs Program, and the National Science Foundation..

  19. Radio detection prospects for a bulge population of millisecond pulsars as suggested by Fermi LAT observations of the inner Galaxy

    CERN Document Server

    Calore, Francesca; Donato, Fiorenza; Hessels, Jason W T; Weniger, Christoph

    2015-01-01

    Analogously to globular clusters, the dense stellar environment of the Galactic center has been proposed to host a large population of as-yet undetected millisecond pulsars (MSPs). Recently, this hypothesis found support in the analysis of gamma rays from the inner Galaxy seen by the Large Area Telescope (LAT) aboard the Fermi satellite, which revealed a possible excess of diffuse GeV photons in the inner 15 deg about the Galactic center (Fermi GeV excess). The excess can be interpreted as the collective emission of thousands of MSPs in the Galactic bulge, with a spherical distribution that strongly peaks towards the Galactic center. In order to fully establish the MSP interpretation, it is essential to find corroborating evidence in multi-wavelength searches, most notably through the detection of radio pulsation from individual bulge MSPs. Based on globular cluster observations and the gamma-ray emission from the inner Galaxy, we investigate the prospects for detecting MSPs in the Galactic bulge. While previ...

  20. High-fidelity radio astronomical polarimetry using a millisecond pulsar as a polarized reference source

    CERN Document Server

    van Straten, W

    2012-01-01

    A new method of polarimetric calibration is presented in which the instrumental response is derived from regular observations of PSR J0437-4715 based on the assumption that the mean polarized emission from this millisecond pulsar remains constant over time. The technique is applicable to any experiment in which high-fidelity polarimetry is required over long time scales; it is demonstrated by calibrating 7.2 years of high-precision timing observations of PSR J1022+1001 made at the Parkes Observatory. Application of the new technique followed by arrival time estimation using matrix template matching yields post-fit residuals with an uncertainty-weighted standard deviation of 880 ns, two times smaller than that of arrival time residuals obtained via conventional methods of calibration and arrival time estimation. The precision achieved by this experiment yields the first significant measurements of the secular variation of the projected semi-major axis, the precession of periastron, and the Shapiro delay; it al...

  1. ON THE FORMATION OF ECCENTRIC MILLISECOND PULSARS WITH HELIUM WHITE-DWARF COMPANIONS

    Energy Technology Data Exchange (ETDEWEB)

    Antoniadis, John, E-mail: antoniadis@dunlap.utoronto.ca [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Dunlap Institute for Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, Ontario M5S 3H4 (Canada)

    2014-12-20

    Millisecond pulsars (MSPs) orbiting helium white dwarfs (WDs) in eccentric orbits challenge the established binary-evolution paradigm that predicts efficient orbital circularization during the mass-transfer episode that spins up the pulsar. Freire and Tauris recently proposed that these binary MSPs may instead form from the rotationally delayed accretion-induced collapse of a massive WD. However, their hypothesis predicts that eccentric systems preferably host low-mass pulsars and travel with small systemic velocities—in tension with new observational constraints. Here, I show that a substantial growth in eccentricity may alternatively arise from the dynamical interaction of the binary with a circumbinary disk. Such a disk may form from ejected donor material during hydrogen flash episodes, when the neutron star is already an active radio pulsar and tidal forces can no longer circularize the binary. I demonstrate that a short-lived (10{sup 4}-10{sup 5} yr) disk can result in eccentricities of e ≅ 0.01-0.15 for orbital periods between 15 and 50 days. Finally, I propose that, more generally, the disk hypothesis may explain the lack of circular binary pulsars for the aforementioned orbital-period range.

  2. On the Formation of Eccentric Millisecond Pulsars with Helium White-dwarf Companions

    Science.gov (United States)

    Antoniadis, John

    2014-12-01

    Millisecond pulsars (MSPs) orbiting helium white dwarfs (WDs) in eccentric orbits challenge the established binary-evolution paradigm that predicts efficient orbital circularization during the mass-transfer episode that spins up the pulsar. Freire & Tauris recently proposed that these binary MSPs may instead form from the rotationally delayed accretion-induced collapse of a massive WD. However, their hypothesis predicts that eccentric systems preferably host low-mass pulsars and travel with small systemic velocities—in tension with new observational constraints. Here, I show that a substantial growth in eccentricity may alternatively arise from the dynamical interaction of the binary with a circumbinary disk. Such a disk may form from ejected donor material during hydrogen flash episodes, when the neutron star is already an active radio pulsar and tidal forces can no longer circularize the binary. I demonstrate that a short-lived (104-105 yr) disk can result in eccentricities of e ~= 0.01-0.15 for orbital periods between 15 and 50 days. Finally, I propose that, more generally, the disk hypothesis may explain the lack of circular binary pulsars for the aforementioned orbital-period range.

  3. Application of the Ghosh & Lamb Relation to the Spin-up/down Behavior in the X-ray Binary Pulsar 4U 1626-67

    CERN Document Server

    Takagi, Toshihiro; Sugizaki, Mutsumi; Makishima, Kazuo; Morii, Mikio

    2016-01-01

    We analyzed continuous MAXI/GSC data of the X-ray binary pulsar 4U 1626-67 from 2009 October to 2013 September, and determined the pulse period and the pulse-period derivative for every 60-d interval by the epoch folding method. The obtained periods are consistent with those provided by the Fermi/GBM pulsar project. In all the 60-d intervals, the pulsar was observed to spin up, with the spin-up rate positively correlated with the 2-20 keV flux. We applied the accretion torque model proposed by Ghosh & Lamb (1979, ApJ, 234, 296) to the MAXI/GSC data, as well as the past data including both spin-up and spin-down phases. The Ghosh & Lamb relation was confirmed to successfully explain the observed relation between the spin-up/down rate and the flux. By comparing the model-predicted luminosity with the observed flux, the source distance was constrained as 5-13 kpc, which is consistent with that by Chakrabarty (1998, ApJ, 492, 342). Conversely, if the source distance is assumed, the data can constrain the m...

  4. 363. WE-Heraeus seminar on neutron stars and pulsars - 40 years after the discovery. Posters and contributed talks

    Energy Technology Data Exchange (ETDEWEB)

    Becker, W.; Huang, H.H. (eds.)

    2007-07-01

    The following topics were dealt with: X-ray observation of pulsars, gamma-ray observation of pulsars, radio observations of pulsars, theory of neutron stars and pulsars, AXPs, SGRs, and strange stars, gravitayional waves, analysis tools with software. (HSI)

  5. Discovery of an X-Ray Synchrotron Nebula Associated with the Radio Pulsar PSR B1853+01 in the Supernova Remnant W44

    Science.gov (United States)

    Harrus, Ilana M.; Hughes, John P.; Helfand, David J.

    1996-06-01

    We report the detection, using data from the Advanced Satellite for Cosmology and Astrophysics (ASCA), of a hard X-ray source in the vicinity of the radio pulsar PSR B1853+01, which is located within the supernova remnant (SNR) W44. PSR B1853+01, a 267 ms pulsar, has to date been detected only in the radio band. Previous observations at soft X-ray energies (e.g., with ROSAT HRI) have failed to detect any significant X-ray emission (pulsed or unpulsed) from the pulsar. In addition, no high-energy emission (>~4 keV) has been detected previously from W44. Over the 0.5--4.0 keV band, the ASCA data show soft thermal emission from W44, with a morphology very similar to that observed earlier by Einstein and ROSAT. In the high-energy band (4.0--9.5 keV), the SNR is, for the most part, invisible, although a source coincident with the position of PSR B1853+01 is evident. The observed ASCA spectra are consistent with a power-law origin (photon index ~2.3) for the X-ray emission from this source at a flux level (flux density ~0.5 mu Jy at 1 keV) consistent with previous upper limits. The maximum allowed size for the source is determined directly from the ASCA data (~30"). Timing analysis of the hard X-ray source failed to detect pulsations at the pulsar's period. Based on these lines of evidence, we conclude that the new hard source in W44 represents an X-ray synchrotron nebula associated with PSR B1853+01, rather than the beamed output of the pulsar itself. This discovery adds W44 to the small group of previously known plerionic SNRs. This nebula lies at the low end of, but is consistent with, the correlation between X-ray luminosity and pulsar spin-down energy loss found for such objects, lending further support to our interpretation.

  6. The High Time Resolution Universe Pulsar Survey IV: Discovery and polarimetry of millisecond pulsars

    CERN Document Server

    Keith, M J; Bailes, M; Bates, S D; Bhat, N D R; Burgay, M; Burke-Spolaor, S; D'Amico, N; Jameson, A; Kramer, M; Levin, L; Milia, S; Possenti, A; Stappers, B W; van Straten, W; Parent, D

    2011-01-01

    We present the discovery of six millisecond pulsars (MSPs) in the High Time Resolution Universe (HTRU) survey for pulsars and fast transients carried out with the Parkes radio telescope. All six are in binary systems with approximately circular orbits and are likely to have white dwarf companions. PSR J1017-7156 has a high flux density and a narrow pulse width, making it ideal for precision timing experiments. PSRs J1446-4701 and J1125-5825 are coincident with gamma-ray sources, and folding the high-energy photons with the radio timing ephemeris shows evidence of pulsed gamma-ray emission. PSR J1502-6752 has a spin period of 26.7 ms, and its low period derivative implies that it is a recycled pulsar. The orbital parameters indicate it has a very low mass function, and therefore a companion mass much lower than usually expected for such a mildly recycled pulsar. In addition we present polarisation profiles for all 12 MSPs discovered in the HTRU survey to date. Similar to previous observations of MSPs, we find ...

  7. Radio emission from RS CVn binaries. II. Polarization and spectral properties

    Energy Technology Data Exchange (ETDEWEB)

    Mutel, R.L.; Morris, D.H.; Doiron, D.J.; Lestrade, J.F.

    1987-05-01

    Multiepoch radio observations of circular polarization and spectral characteristics of several close, late-type stellar binaries are reported. The median luminosity of four well-studied systems ranged from 16.2 to 17.1 ergs/s/Hz. For individual systems, the fractional circular polarization decreases with increasing luminosity, particularly at frequencies above 5 GHz. Eclipsing binaries have significantly lower average circular polarization compared with noneclipsing systems. Helicity reversal is almost always observed between 1.4 and 4.9 GHz for systems with high orbital inclination. Comparison with ten years of previously published polarization observations for two RS CVn stellar systems show that the same helicity occurs at a given frequency for a given source, indicating a very stable, large-scale magnetic field geometry. These spectral and polarization characteristics strongly support a model of inhomogeneous gyrosynchrotron emission arising from electrons with power law energy spectra interacting with inhomogeneous magnetic fields. 35 references.

  8. A COMPACT RADIO COUNTERPART TO THE ENERGETIC X-RAY PULSAR ASSOCIATED WITH THE TEV GAMMA-RAY SOURCE J1813-178

    Directory of Open Access Journals (Sweden)

    Sergio Dzib

    2010-01-01

    Full Text Available Reportamos la detección de una fuente de radio compacta y variable coinci- dente con CXOU J181335.1{174957, el pulsar de rayos-X localizado cerca del cen- tro de la remanente de supernova joven G12.82{0.02, la cual traslapa con la fuente TeV compacta HESS J1813{178. La fuente de radio compacta, que llamamos VLA J181335.1{174957, fue detectada en observaciones hechas a 4.86 GHz con el VLA en 2006. Nuevas observaciones hechas con el VLA en 2009 no detectan la fuente a un nivel 1.9+-0.7 veces (2.8o más bajo que el de 2006. Sugerimos que VLA J181335.1{ 174957 podría estar relacionada con alguna de las recientemente detectadas clases de pulsares de radio variables, pero no podemos alcanzar una conclusión más sólida.

  9. Radio Emission from the Be/Black Hole Binary MWC 656

    CERN Document Server

    Dzib, S A; Jaron, F

    2015-01-01

    Context. MWC 656 is the recently discovered first binary system case composed of a Be-type star and an accreting black hole. Its low X-ray luminosity indicates that the system is in a quiescent X-ray state. Aims. The aim of our investigation is to establish if the MWC 656 system has detectable radio emission and if the radio characteristics are consistent with those of quiescent black hole systems. Methods.We used three archived VLA data sets, one hour each, at 3 GHz and seven new VLA observations, two hours each, at 10 GHz to produce very high sensitivity images, down to $\\sim$1$\\,\\mu$Jy. Results.We detected the source twice in the new observations: in the first VLA run, at periastron passage, with a flux density of 14.2$\\,\\pm\\,$2.9 $\\mu$Jy and by combining all together the other six VLA runs, with a flux density of $3.7 \\pm 1.4$ $\\mu$Jy. The resulting combined map of the archived observations has the sensitivity of $1 \\sigma = 6.6\\, \\mu Jy$ but no radio emission is there detected. Conclusions. The radio and...

  10. Current Flows in Pulsar Magnetospheres

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The global structure of .current flows in pulsar magnetosphere is investigated, with rough calculations of the circuit elements. It is emphasized that the potential of the critical field lines (the field lines that intersect the null surface at the light cylinder radius) should be the same as that of interstellar medium, and that pulsars whose rotation axes and magnetic dipole axes are parallel should be positively charged, in order to close the pulsar's current flows. The statistical relation between the radio luminosity and pulsar's electric charge (or the spindown power) may hint that the millisecond pulsars could be low-mass bare strange stars.

  11. Recycling Pulsars: spins, masses and ages

    CERN Document Server

    Tauris, T M; Langer, N

    2012-01-01

    Although the first millisecond pulsars (MSPs) were discovered 30 years ago we still do not understand all details of their formation process. Here, we present new results from Tauris, Langer & Kramer (2012) on the recycling scenario leading to radio MSPs with helium or carbon-oxygen white dwarf companions via evolution of low- and intermediate mass X-ray binaries (LMXBs, IMXBs). We discuss the location of the spin-up line in the (P,Pdot)-diagram and estimate the amount of accreted mass needed to obtain a given spin period and compare with observations. Finally, we constrain the true ages of observed recycled pulsars via calculated isochrones in the (P,Pdot)-diagram.

  12. Bayesian inference for pulsar timing models

    CERN Document Server

    Vigeland, Sarah J

    2013-01-01

    The extremely regular, periodic radio emission from millisecond pulsars make them useful tools for studying neutron star astrophysics, general relativity, and low-frequency gravitational waves. These studies require that the observed pulse time of arrivals are fit to complicated timing models that describe numerous effects such as the astrometry of the source, the evolution of the pulsar's spin, the presence of a binary companion, and the propagation of the pulses through the interstellar medium. In this paper, we discuss the benefits of using Bayesian inference to obtain these timing solutions. These include the validation of linearized least-squares model fits when they are correct, and the proper characterization of parameter uncertainties when they are not; the incorporation of prior parameter information and of models of correlated noise; and the Bayesian comparison of alternative timing models. We describe our computational setup, which combines the timing models of tempo2 with the nested-sampling integ...

  13. Identification of HESS J1303-631 as a Pulsar Wind Nebula through gamma-ray, X-ray and radio observations

    CERN Document Server

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

    2012-01-01

    The previously unidentified very high-energy (VHE; E > 100 GeV) \\gamma-ray source HESS J1303-631, discovered in 2004, is re-examined including new data from the H.E.S.S. Cherenkov telescope array. Archival data from the XMM-Newton X-ray satellite and from the PMN radio survey are also examined. Detailed morphological and spectral studies of VHE \\gamma-ray emission as well as of the XMM-Newton X-ray data are performed. Significant energy-dependent morphology of the \\gamma-ray source is detected with high-energy emission (E > 10 TeV) positionally coincident with the pulsar PSR J1301-6305 and lower energy emission (E <2 TeV) extending \\sim 0.4^{\\circ} to the South-East of the pulsar. The spectrum of the VHE source can be described with a power-law with an exponential cut-off N_{0} = (5.6 \\pm 0.5) X 10^{-12} TeV^-1 cm^-2 s^-1, \\Gamma = 1.5 \\pm 0.2) and E_{\\rm cut} = (7.7 \\pm 2.2) TeV. The PWN is also detected in X-rays, extending \\sim 2-3' from the pulsar position towards the center of the \\gamma-ray emission ...

  14. On the puzzling high-energy pulsations of the energetic radio-quiet γ-ray pulsar J1813–1246

    Energy Technology Data Exchange (ETDEWEB)

    Marelli, M.; Pizzocaro, D.; De Luca, A.; Caraveo, P.; Salvetti, D. [INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica Milano, via E. Bassini 15, I-20133 Milano (Italy); Harding, A. [Astrophysics Science Division, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Wood, K. S. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Saz Parkinson, P. M. [Department of Physics, The University of Hong Kong, Pokfulam Road (Hong Kong); Acero, F., E-mail: marelli@lambrate.inaf.it [Laboratoire AIM, CEA-IRFU/CNRS/Universit Paris Diderot, Service d' Astrophysique, CEA Saclay, F-91191 Gif sur Yvette (France)

    2014-11-10

    We have analyzed the new deep XMM-Newton and Chandra observations of the energetic, radio-quiet pulsar J1813–1246. The X-ray spectrum is nonthermal, very hard, and absorbed. Based on spectral considerations, we propose that J1813 is located at a distance further than 2.5 kpc. J1813 is highly pulsed in the X-ray domain, with a light curve characterized by two sharp, asymmetrical peaks, separated by 0.5 in phase. We detected no significant X-ray spectral changes during the pulsar phase. We extended the available Fermi ephemeris to five years. We found two glitches. The γ-ray light curve is characterized by two peaks, separated by 0.5 in phase, with a bridge in between and no off-pulse emission. The spectrum shows clear evolution in phase, being softer at the peaks and hardening toward the bridge. Surprisingly, both X-ray peaks lag behind the γ-ray ones by a quarter of phase. We found a hint of detection in the 30-500 keV band with INTEGRAL, which is consistent with the extrapolation of both the soft X-ray and γ-ray emission of J1813. The unique X-ray and γ-ray phasing suggests a singular emission geometry. We discuss some possibilities within the current pulsar emission models. Finally, we develop an alternative geometrical model where the X-ray emission comes from polar cap pair cascades.

  15. A population of gamma-ray millisecond pulsars seen with the Fermi Large Area Telescope.

    Science.gov (United States)

    Abdo, A A; Ackermann, M; Ajello, M; Atwood, W B; Axelsson, M; Baldini, L; Ballet, J; Barbiellini, G; Baring, M G; Bastieri, D; Baughman, B M; Bechtol, K; Bellazzini, R; Berenji, B; Bignami, G F; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Bregeon, J; Brez, A; Brigida, M; Bruel, P; Burnett, T H; Caliandro, G A; Cameron, R A; Camilo, F; Caraveo, P A; Carlson, P; Casandjian, J M; Cecchi, C; Celik, O; Charles, E; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cognard, I; Cohen-Tanugi, J; Cominsky, L R; Conrad, J; Corbet, R; Cutini, S; Dermer, C D; Desvignes, G; de Angelis, A; de Luca, A; de Palma, F; Digel, S W; Dormody, M; do Couto e Silva, E; Drell, P S; Dubois, R; Dumora, D; Edmonds, Y; Farnier, C; Favuzzi, C; Fegan, S J; Focke, W B; Frailis, M; Freire, P C C; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giebels, B; Giglietto, N; Giordano, F; Glanzman, T; Godfrey, G; Grenier, I A; Grondin, M H; Grove, J E; Guillemot, L; Guiriec, S; Hanabata, Y; Harding, A K; Hayashida, M; Hays, E; Hobbs, G; Hughes, R E; Jóhannesson, G; Johnson, A S; Johnson, R P; Johnson, T J; Johnson, W N; Johnston, S; Kamae, T; Katagiri, H; Kataoka, J; Kawai, N; Kerr, M; Knödlseder, J; Kocian, M L; Kramer, M; Kuss, M; Lande, J; Latronico, L; Lemoine-Goumard, M; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Makeev, A; Manchester, R N; Marelli, M; Mazziotta, M N; McConville, W; McEnery, J E; McLaughlin, M A; Meurer, C; Michelson, P F; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nolan, P L; Norris, J P; Nuss, E; Ohsugi, T; Omodei, N; Orlando, E; Ormes, J F; Paneque, D; Panetta, J H; Parent, D; Pelassa, V; Pepe, M; Pesce-Rollins, M; Piron, F; Porter, T A; Rainò, S; Rando, R; Ransom, S M; Ray, P S; Razzano, M; Rea, N; Reimer, A; Reimer, O; Reposeur, T; Ritz, S; Rochester, L S; Rodriguez, A Y; Romani, R W; Roth, M; Ryde, F; Sadrozinski, H F W; Sanchez, D; Sander, A; Saz Parkinson, P M; Scargle, J D; Schalk, T L; Sgrò, C; Siskind, E J; Smith, D A; Smith, P D; Spandre, G; Spinelli, P; Stappers, B W; Starck, J L; Striani, E; Strickman, M S; Suson, D J; Tajima, H; Takahashi, H; Tanaka, T; Thayer, J B; Thayer, J G; Theureau, G; Thompson, D J; Thorsett, S E; Tibaldo, L; Torres, D F; Tosti, G; Tramacere, A; Uchiyama, Y; Usher, T L; Van Etten, A; Vasileiou, V; Venter, C; Vilchez, N; Vitale, V; Waite, A P; Wallace, E; Wang, P; Watters, K; Webb, N; Weltevrede, P; Winer, B L; Wood, K S; Ylinen, T; Ziegler, M

    2009-08-14

    Pulsars are born with subsecond spin periods and slow by electromagnetic braking for several tens of millions of years, when detectable radiation ceases. A second life can occur for neutron stars in binary systems. They can acquire mass and angular momentum from their companions, to be spun up to millisecond periods and begin radiating again. We searched Fermi Large Area Telescope data for pulsations from all known millisecond pulsars (MSPs) outside of globular clusters, using rotation parameters from radio telescopes. Strong gamma-ray pulsations were detected for eight MSPs. The gamma-ray pulse profiles and spectral properties resemble those of young gamma-ray pulsars. The basic emission mechanism seems to be the same for MSPs and young pulsars, with the emission originating in regions far from the neutron star surface.

  16. Identification of HESS J1303-631 as a pulsar wind nebula through γ-ray, X-ray, and radio observations

    Science.gov (United States)

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

    2012-12-01

    Aims: The previously unidentified very high-energy (VHE; E > 100 GeV) γ-ray source HESS J1303-631, discovered in 2004, is re-examined including new data from the H.E.S.S. Cherenkov telescope array in order to identify this object. Archival data from the XMM-Newton X-ray satellite and from the PMN radio survey are also examined. Methods: Detailed morphological and spectral studies of VHE γ-ray emission as well as of the XMM-Newton X-ray data are performed. Radio data from the PMN survey are used as well to construct a leptonic model of the source. The γ-ray and X-ray spectra and radio upper limit are used to construct a one zone leptonic model of the spectral energy distribution (SED). Results: Significant energy-dependent morphology of the γ-ray source is detected with high-energy emission (E > 10 TeV) positionally coincident with the pulsar PSR J1301-6305 and lower energy emission (E < 2 TeV) extending 0.4° to the southeast of the pulsar. The spectrum of the VHE source can be described with a power-law with an exponential cut-off N0 = (5.6 ± 0.5) × 10-12 TeV-1 cm-2 s-1, Γ = 1.5 ± 0.2) and Ecut = (7.7 ± 2.2) TeV. The pulsar wind nebula (PWN) is also detected in X-rays, extending 2-3' from the pulsar position towards the center of the γ-ray emission region. A potential radio counterpart from the PMN survey is also discussed, showing a hint for a counterpart at the edge of the X-ray PWN trail and is taken as an upper limit in the SED. The extended X-ray PWN has an unabsorbed flux of F_2{-10 keV ˜ 1.6+0.2-0.4× 10-13 erg cm-2 s-1} and is detected at a significance of 6.5σ. The SED is well described by a one zone leptonic scenario which, with its associated caveats, predicts a very low average magnetic field for this source. Conclusions: Significant energy-dependent morphology of this source, as well as the identification of an associated X-ray PWN from XMM-Newton observations enable identification of the VHE source as an evolved PWN associated to the

  17. Simultaneous Observations of Giant Pulses from the Crab Pulsar, with the Murchison Widefield Array and Parkes Radio Telescope: Implications for the Giant Pulse Emission Mechanism

    CERN Document Server

    Oronsaye, S I; Bhat, N D R; Tremblay, S E; McSweeney, S J; Tingay, S J; van Straten, W; Jameson, A; Bernardi, G; Bowman, J D; Briggs, F; Cappallo, R J; Deshpande, A A; Greenhill, L J; Hazelton, B J; Johnston-Hollitt, M; Kaplan, D L; Lonsdale, C J; McWhirter, S R; Mitchell, D A; Morales, M F; Morgan, E; Oberoi, D; Prabu, T; Shankar, N Udaya; Srivani, K S; Subrahmanyan, R; Wayth, R B; Webster, R L; Williams, A; Williams, C L

    2015-01-01

    We report on observations of giant pulses from the Crab pulsar performed simultaneously with the Parkes radio telescope and the incoherent combination of the Murchison Widefield Array (MWA) antenna tiles. The observations were performed over a duration of approximately one hour at a center frequency of 1382 MHz with 340 MHz bandwidth at Parkes, and at a center frequency of 193 MHz with 15 MHz bandwidth at the MWA. Our analysis has led to the detection of 55 giant pulses at the MWA and 2075 at Parkes above a threshold of 3.5$\\sigma$ and 6.5$\\sigma$ respectively. We detected 51$\\%$ of the MWA giant pulses at the Parkes radio telescope, with spectral indices in the range of $-3.6>\\alpha> -4.9$ ($S_{\\rm \

  18. Observational Constraints on Radio Transient Emissions from Binary Neutron Star Mergers

    Science.gov (United States)

    Papadopoulos, Joanna; Dispoto, D.; Cardena, B.; Kavic, M.; Ellingson, S.; Simonetti, J.; Cutchin, S.; Patterson, C.

    2012-01-01

    The merger of a binary neutron star pair is expected to generate a strong transient radio signal. This emission will be strongest at low-frequency and will disperse as it transverses the interstellar medium arriving at Earth after coincidentally emitted gravitational or (higher frequency) electromagnetic signals. The rate of compact object merger events is poorly constrained by observations. The Eight-meter-wavelength Transient Array (ETA) telescope is a low-frequency radio telescope initially located at the Pisgah Astronomical Research Institute (PARI), which is sensitive to a frequency range of 29-47 MHz. It is being upgraded and relocated to western Virginia where it will continue to conduct low frequency observations. This instrument is an all-sky instrument designed to detect astronomical sources of radio transients. Using a series of observations taken during the ETA's first science run, we were able to constrain the rate of such merger events to <1.3 x 10-5 Mpc-3/yr.

  19. Pulsar Timing Arrays

    OpenAIRE

    Joshi, Bhal Chandra

    2013-01-01

    In the last decade, the use of an ensemble of radio pulsars to constrain the characteristic strain caused by a stochastic gravitational wave background has advanced the cause of detection of very low frequency gravitational waves significantly. This electromagnetic means of gravitational wave detection, called Pulsar Timing Array(PTA), is reviewed in this article. The principle of operation of PTA, the current operating PTAs and their status is presented along-with a discussion of the main ch...

  20. Application of the Ghosh & Lamb relation to the spin-up/down behavior in the X-ray binary pulsar 4U 1626-67

    Science.gov (United States)

    Takagi, Toshihiro; Mihara, Tatehiro; Sugizaki, Mutsumi; Makishima, Kazuo; Morii, Mikio

    2016-06-01

    We analyzed continuous Monitor of All-sky X-ray Image/Gas Slit Camera (MAXI/GSC) data of the X-ray binary pulsar 4U 1626-67 from 2009 October to 2013 September, and determined the pulse period and the pulse-period derivative for every 60-d interval by the epoch folding method. The obtained periods are consistent with those provided by the Fermi/Gamma-ray Burst Monitor pulsar project. In all the 60-d intervals, the pulsar was observed to spin up, with the spin-up rate positively correlated with the 2-20 keV flux. We applied the accretion torque model proposed by Ghosh and Lamb (1979, ApJ, 234, 296) to the MAXI/GSC data, as well as the past data including both spin-up and spin-down phases. The "Ghosh & Lamb" relation was confirmed to successfully explain the observed relation between the spin-up/down rate and the flux. By comparing the model-predicted luminosity with the observed flux, the source distance was constrained as 5-13 kpc, which is consistent with that found by Chakrabarty (1998, ApJ, 492, 342). Conversely, if the source distance is assumed, the data can constrain the mass and radius of the neutron star, because the Ghosh & Lamb model depends on these parameters. We attempted this idea, and found that an assumed distance of, e.g., 10 kpc gives a mass in the range of 1.81-1.90 solar mass, and a radius of 11.4-11.5 km, although these results are still subject to considerable systematic uncertainties, other than distance.

  1. A radio-map of the colliding winds in the very massive binary system HD 93129A

    CERN Document Server

    Benaglia, Paula; Moldon, Javier; Nelan, Ed; De Becker, Michael; Dougherty, Sean M; Koribalski, Baerbel

    2015-01-01

    Radio observations are an effective tool to discover particle acceleration regions in colliding-wind binaries, through detection of synchrotron radiation; these regions are natural laboratories for the study of relativistic particles. Wind-collision region (WCR) models can reproduce the radio continuum spectra of massive binaries that contain both thermal and non-thermal radio emission; however, key constraints for models come from high-resolution imaging. Only five WCRs have been resolved to date at radio frequencies at milliarcsec (mas) angular scales. The source HD 93129A, prototype of the very few known O2 I stars, is a promising target for study: recently, a second massive, early-type star about 50 mas away was discovered, and a non-thermal radio source detected in the region. Preliminary long-baseline array data suggest that a significant fraction of the radio emission from the system comes from a putative WCR. We sought evidence that HD 93129A is a massive binary system with colliding stellar winds tha...

  2. Identification of the High-Energy Gamma-Ray Source 3FGL J1544.6-1125 as a Transitional Millisecond Pulsar Binary in an Accreting State

    CERN Document Server

    Bogdanov, Slavko

    2015-01-01

    We present X-ray, ultraviolet, and optical observations of 1RXS J154439.4-112820, the most probable counterpart of the unassociated Fermi LAT source 3FGL J1544.6-1125. The optical data reveal rapid variability, which is a feature of accreting systems. The X-ray data exhibit large-amplitude flux variations in the form of fast switching (within ~10 s) between two distinct flux levels that differ by a factor of $\\approx$10. The detailed optical and X-ray behavior is virtually identical to that seen in the accretion-disk-dominated states of the transitional millisecond pulsar binaries PSR J1023+0038 and XSS J12270-4859, which are also associated with $\\gamma$-ray sources. Based on the available observational evidence, we conclude that 1RXS J154439.4-112820 and 3FGL J1544.6-1125 are the same object, with the X-rays arising from intermittent low-luminosity accretion onto a millisecond pulsar and the $\\gamma$-rays originating from an accretion-driven outflow. 1RXS J154439.4-112820 is only the fourth $\\gamma$-ray emi...

  3. Gamma rays from Galactic pulsars

    OpenAIRE

    2014-01-01

    Gamma rays from young pulsars and milli-second pulsars are expected to contribute to the diffuse gamma-ray emission measured by the {\\it Fermi} Large Area Telescope (LAT) at high latitudes. We derive the contribution of the pulsars undetected counterpart by using information from radio to gamma rays and we show that they explain only a small fraction of the isotropic diffuse gamma-ray background.

  4. The VLT-FLAMES Tarantula Survey: The fastest rotating O-type star and shortest period LMC pulsar - remnants of a supernova disrupted binary?

    CERN Document Server

    Dufton, P L; Evans, C J; Brott, I; Cantiello, M; de Koter, A; de Mink, S E; Fraser, M; Hénault-Brunet, V; Howarth, I D; Langer, N; Lennon, D J; Markova, N; Sana, H; Taylor, W D

    2011-01-01

    We present a spectroscopic analysis of an extremely rapidly rotating late O-type star, VFTS102, observed during a spectroscopic survey of 30 Doradus. VFTS102 has a projected rotational velocity larger than 500\\kms\\ and probably as large as 600\\kms; as such it would appear to be the most rapidly rotating massive star currently identified. Its radial velocity differs by 40\\kms\\ from the mean for 30 Doradus, suggesting that it is a runaway. VFTS102 lies 12 pcs from the X-ray pulsar PSR J0537-6910 in the tail of its X-ray diffuse emission. We suggest that these objects originated from a binary system with the rotational and radial velocities of VFTS102 resulting from mass transfer from the progenitor of PSR J0537-691 and the supernova explosion respectively.

  5. Understanding pulsar magnetospheres with the SKA

    CERN Document Server

    Karastergiou, A; Andersson, N; Breton, R; Brook, P; Gwinn, C; Lewandowska, N; Keane, E; Kramer, M; Macquart, J -P; Serylak, M; Shannon, R; Stappers, B; van Leeuwen, J; Verbiest, J P W; Weltevrede, P; Wright, G

    2015-01-01

    The SKA will discover tens of thousands of pulsars and provide unprecedented data quality on these, as well as the currently known population, due to its unrivalled sensitivity. Here, we outline the state of the art of our understanding of magnetospheric radio emission from pulsars and how we will use the SKA to solve the open problems in pulsar magnetospheric physics.

  6. Understanding the residual patterns of timing solutions of radio pulsars with a model of magnetic field oscillation

    Science.gov (United States)

    Gao, Xu-Dong; Zhang, Shuang-Nan; Yi, Shu-Xu; Xie, Yi; Fu, Jian-Ning

    2016-06-01

    We explain some phenomena existing generally in the timing residuals: amplitude and sign of the second derivative of a pulsar's spin-frequency (ddot{ν }), some sophisticated residual patterns, which also change with the time span of data segments. The sample is taken from Hobbs et al., in which the pulsar's spin-frequency and its first derivative have been subtracted from the timing solution fitting. We first classify the timing residual patterns into different types based on the sign of ddot{ν }. Then we use the magnetic field oscillation model developed in our group to fit successfully the different kinds of timing residuals with the Markov Chain Monte Carlo method. Finally, we simulate the spin evolution over 20 years for a pulsar with typical parameters and analyse the data with the conventional timing solution fitting. By choosing different segments of the simulated data, we find that most of the observed residual patterns can be reproduced successfully. This is the first time that the observed residual patterns are fitted by a model and reproduced by simulations with very few parameters. From the distribution of the different residual patterns in the P-dot{P} diagram, we argue that (1) a single magnetic field oscillation mode exists commonly in all pulsars throughout their lifetimes; (2) there may be a transition period over the lifetimes of pulsars, in which multiple magnetic field oscillation modes exist.

  7. Pulsar population synthesis using palfa detections and pulsar search collaboratory discoveries including a wide DNS system and a nearby MSP

    Science.gov (United States)

    Swiggum, Joseph Karl

    Using the ensemble of detections from pulsar surveys, we can learn about the sizes and characteristics of underlying populations. In this thesis, I analyze results from the Pulsar Arecibo L-band Feed Array (PALFA) precursor and Green Bank Telescope 350 MHz Drift Scan surveys; I examine survey sensitivity to see how detections can inform pulsar population models, I look at new ways of including young scientists -- high school students -- in the discovery process and I present timing solutions for students' discoveries (including a nearby millisecond pulsar and a pulsar in a wide-orbit double neutron star system). The PALFA survey is on-going and uses the ALFA 7-beam receiver at 1400 MHz to search both inner and outer Galactic sectors visible from Arecibo (32° ?£? 77° and 168° ?£? 214°) close to the Galactic plane (|b| ? 5°) for pulsars. The PALFA precursor survey observed a subset of this region, (|b| ? 1°) and detected 45 pulsars, including one known millisecond pulsar (MSP) and 11 previously unknown, long-period (normal) pulsars. I assess the sensitivity of the PALFA precursor survey and use the number of normal pulsar and MSP detections to infer the size of each underlying Galactic population. Based on 44 normal pulsar detections and one MSP, we constrain each population size to 107,000+36,000-25,000 and 15,000 +85,000-6,000 respectively with 95% confidence. Based on these constraints, we predict yields for the full PALFA survey and find a deficiency in normal pulsar detections, possibly due to radio frequency interference and/or scintillation, neither of which are currently accounted for in population simulations. The GBT 350 MHz Drift Scan survey collected data in the summer of 2007 while the GBT was stationary, undergoing track replacement. Results discussed here come from ~20% of the survey data, which were processed and donated to the Pulsar Search Collaboratory (PSC). The PSC is a joint outreach program between WVU and NRAO, involving high school

  8. Characterizing X-Ray and Radio Emission in the Black Hole X-Ray Binary V404 Cygni During Quiescence

    DEFF Research Database (Denmark)

    Rana, Vikram; Loh, Alan; Corbel, Stephane

    2016-01-01

    We present results from multi-wavelength simultaneous X-ray and radio observations of the black hole X-ray binary V404 Cyg in quiescence. Our coverage with NuSTAR provides the very first opportunity to study the X-ray spectrum of V404 Cyg at energies above 10 keV. The unabsorbed broadband (0...

  9. Discovery of the Optical Counterparts to Four Energetic Fermi Millisecond Pulsars

    CERN Document Server

    Breton, R P; Roberts, M S E; Hessels, J W T; Camilo, F; McLaughlin, M A; Ransom, S M; Ray, P S; Stairs, I H

    2013-01-01

    In the last few years, over 43 millisecond radio pulsars have been discovered by targeted searches of unidentified gamma-ray sources found by the Fermi Gamma-Ray Space Telescope. A large fraction of these millisecond pulsars are in compact binaries with low-mass companions. These systems often show eclipses of the pulsar signal and are commonly known as black widows and redbacks because the pulsar is gradually destroying its companion. In this paper, we report on the optical discovery of four strongly irradiated millisecond pulsar companions. All four sources show modulations of their color and luminosity at the known orbital periods from radio timing. Light curve modelling of our exploratory data shows that the equilibrium temperature reached on the companion's dayside with respect to their nightside is consistent with about 10-30% of the available spin-down energy from the pulsar being reprocessed to increase the companion's dayside temperature. This value compares well with the range observed in other irra...

  10. Polarization observations of 20 millisecond pulsars

    CERN Document Server

    Yan, Wenming; van Straten, Willem; Reynolds, John; Hobbs, George; Wang, Na; Bailes, Matthew; Bhat, Ramesh; Burke-Spolaor, Sarah; Champion, David; Coles, William; Hotan, Aidan; Khoo, Jonathan; Oslowski, Stefan; Sarkissian, John; Verbiest, Joris; Yardley, Daniel

    2011-01-01

    Polarization profiles are presented for 20 millisecond pulsars that are being observed as part of the Parkes Pulsar Timing Array project. The observations used the Parkes multibeam receiver with a central frequency of 1369 MHz and the Parkes digital filterbank pulsar signal-processing system PDFB2. Because of the large total observing time, the summed polarization profiles have very high signal/noise ratios and show many previously undetected profile features. Thirteen of the 20 pulsars show emission over more than half of the pulse period. Polarization variations across the profiles are complex and the observed position angle variations are generally not in accord with the rotating-vector model for pulsar polarization. Never-the-less, the polarization properties are broadly similar to those of normal (non-millisecond) pulsars, suggesting that the basic radio emission mechanism is the same in both classes of pulsar. The results support the idea that radio emission from millisecond pulsars originates high in t...

  11. Recycled Pulsars: Spins, Masses and Ages

    CERN Document Server

    Tauris, Thomas M

    2016-01-01

    Recycled pulsars are mainly characterized by their spin periods, B-fields and masses. All these quantities are affected by previous interactions with a companion star in a binary system. Therefore, we can use these quantities as fossil records and learn about binary evolution. Here, I briefly review the distribution of these observed quantities and summarize our current understanding of the pulsar recycling process.

  12. Radio emission from RS CVn binaries. II - Polarization and spectral properties

    Science.gov (United States)

    Mutel, R. L.; Morris, D. H.; Doiron, D. J.; Lestrade, J. F.

    1987-05-01

    Multi-epoch radio observations of circular polarization and spectral characteristics of several close, late-type stellar binaries (mainly of the RS CVn class) are reported. The median luminosity of four well-studied systems ranged from 16.2 ≤ log(LR) ≤ 17.1 erg s-1Hz-1. For individual systems, the fractional circular polarization decreases with increasing luminosity, particularly at frequencies f ≥ 5 GHz. Eclipsing binaries have significantly lower average circular polarization compared with non-eclipsing systems. Helicity reversal is almost always observed between 1.4 and 4.9 GHz for systems with high orbital inclination. These spectral and polarization characteristics, combined with direct measurements of the brightness temperature using previously published VLBI observations, strongly support a model of inhomogeneous gyrosynchrotron emission arising from electrons with power law energy spectra interacting with inhomogeneous magnetic fields. The source emission region is probably cospatial with the large coronal loops deduced from X-ray observations.

  13. Double-double radio galaxies: remnants of merger of supermassive binary black holes

    CERN Document Server

    Liu, F K; Cao, S L; Wu, Xue-Bing

    2003-01-01

    The activity of active galaxy may be triggered by the merge of galaxies and present-day galaxies are probably the product of successive minor mergers. The frequent galactic merges at high redshift imply that active galaxy harbors supermassive unequal-mass binary black holes in its center at least once during its life time. In this paper, we showed that the recently discovered double-lobed FR II radio galaxies are the remnants of such supermassive binary black holes. The inspiraling secondary black hole opens a gap in the accretion disk and removes the inner accretion disk when it merges into the primary black hole, leaving a big hole of about several hundreds of Schwarzschild radius in the vicinity of the post-merged supermassive black hole and leading to an interruption of jet formation. When the outer accretion disk slowly refills the big hole on a viscous time scale, the jet formation restarts and the interaction of the recurrent jets and the inter-galactic medium forms a secondary pair of lobes. We applie...

  14. Spin Tilts in the Double Pulsar Reveal Off-Center Supernova Kick and Tumble

    CERN Document Server

    Farr, Will M; Lyutikov, Maxim; Kalogera, Vassiliki

    2011-01-01

    The system PSR J0737-3039 is the only binary pulsar known to consist of two radio pulsars (PSR J0737-3039 A and PSR J0737-3039 B). This configuration allows measurements of spin orientation for both pulsars: pulsar A's spin is tilted from the orbital angular momentum by no more than 14 degrees; pulsar B's by 130 degrees. This spin-spin misalignment requires that the origin of most of B's spin is its supernova; the spin could originate from a substantial off-center kick, causing pulsar B to tumble to its misaligned state. Under the typical assumption of an instantaneous kick and using current constraints on the kick magnitude, it must have been displaced from the center of mass of the exploding star by at least 1 km and probably 5--10 km. Regardless of the details of the process that produced pulsar B's current spin, the orientation of the spins in the J0737-3039 system provides a direct, unique constraint on angular momentum production in supernovae.

  15. The Pulsar Search Collaboratory

    CERN Document Server

    Rosen, Rachel; McLaughlin, Maura A; Lynch, Ryan; Kondratiev, Vlad I; Boyles, Jason R; Wilson, M Terry; Lorimer, Duncan R; Ransom, Scott; 10.3847/AER2010004

    2010-01-01

    The Pulsar Search Collaboratory [PSC, NSF #0737641] is a joint project between the National Radio Astronomy Observatory (NRAO) and West Virginia University (WVU) designed to interest high school students in science, technology, engineering, and mathematics [STEM] related career paths by helping them to conduct authentic scientific research. The 3- year PSC program, which began in summer 2008, teaches students to analyze astronomical radio data acquired with the 100-m Robert C. Byrd Green Bank Telescope for the purpose of discovering new pulsars. We present the results of the first complete year of the PSC, which includes two astronomical discoveries.

  16. Regimes of Pulsar Pair Formation and Particle Energetics

    CERN Document Server

    Harding, A K; Muslimov, A G; Harding, Alice K.; Zhang, Alexander G. Muslimov & Bing

    2002-01-01

    We investigate the conditions required for the production of electron-positron pairs above a pulsar polar cap (PC) and the influence of pair production on the energetics of the primary particle acceleration. Assuming space-charge limited flow acceleration including the inertial frame-dragging effect, we allow both one-photon and two-photon pair production by either curvature radiation (CR) photons or photons resulting from inverse-Compton scattering of thermal photons from the PC by primary electrons. We find that, while only the younger pulsars can produce pairs through CR, nearly all known radio pulsars are capable of producing pairs through non-resonant inverse-Compton scatterings. The effect of the neutron star equations of state on the pair death lines is explored. We show that pair production is facilitated in more compact stars and more massive stars. Therefore accretion of mass by pulsars in binary systems may allow pair production in most of the millisecond pulsar population. We also find that two-ph...

  17. SPIN TILTS IN THE DOUBLE PULSAR REVEAL SUPERNOVA SPIN ANGULAR-MOMENTUM PRODUCTION

    Energy Technology Data Exchange (ETDEWEB)

    Farr, Will M.; Kremer, Kyle; Kalogera, Vassiliki [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States); Lyutikov, Maxim, E-mail: w-farr@northwestern.edu, E-mail: kylekremer2012@u.northwestern.edu, E-mail: vicky@northwestern.edu, E-mail: lyutikov@purdue.edu [Physics Department, Purdue University, 525 Northwestern Avenue, West Lafayette, IN 47907 (United States)

    2011-12-01

    The system PSR J0737-3039 is the only binary pulsar known to consist of two radio pulsars (PSR J0737-3039 A and PSR J0737-3039 B). This unique configuration allows measurements of spin orientation for both pulsars: pulsar A's spin is tilted from the orbital angular momentum by no more than 14 deg at 95% confidence; pulsar B's by 130 {+-} 1 deg at 99.7% confidence. This spin-spin misalignment requires that the origin of most of B's present-day spin is connected to the supernova that formed pulsar B. Under the simplified assumption of a single, instantaneous kick during the supernova, the spin could be thought of as originating from the off-center nature of the kick, causing pulsar B to tumble to its misaligned state. With this assumption, and using current constraints on the kick magnitude, we find that pulsar B's instantaneous kick must have been displaced from the center of mass of the exploding star by at least 1 km and probably 5-10 km. Regardless of the details of the kick mechanism and the process that produced pulsar B's current spin, the measured spin-spin misalignment in the double pulsar system provides an empirical, direct constraint on the angular momentum production in this supernova. This constraint can be used to guide core-collapse simulations and the quest for understanding the spins and kicks of compact objects.

  18. X-ray states of redback millisecond pulsars

    Energy Technology Data Exchange (ETDEWEB)

    Linares, M. [Instituto de Astrofísica de Canarias, c/Vía Láctea s/n, E-38205 La Laguna, Tenerife (Spain)

    2014-11-01

    Compact binary millisecond pulsars with main-sequence donors, often referred to as 'redbacks', constitute the long-sought link between low-mass X-ray binaries and millisecond radio pulsars and offer a unique probe of the interaction between pulsar winds and accretion flows. We present a systematic study of eight nearby redbacks, using more than 100 observations obtained with Swift's X-ray Telescope. We distinguish between three main states: pulsar, disk, and outburst states. We find X-ray mode switching in the disk state of PSR J1023+0038 and XSS J12270-4859, similar to what was found in the other redback that showed evidence for accretion: rapid, recurrent changes in X-ray luminosity (0.5-10 keV, L {sub X}), between (6-9) × 10{sup 32} erg s{sup –1} (disk-passive state) and (3-5) × 10{sup 33} erg s{sup –1} (disk-active state). This strongly suggests that mode switching—which has not been observed in quiescent low-mass X-ray binaries—is universal among redback millisecond pulsars in the disk state. We briefly explore the implications for accretion disk truncation and find that the inferred magnetospheric radius in the disk state of PSR J1023+0038 and XSS J12270-4859 lies outside the light cylinder. Finally, we note that all three redbacks that have developed accretion disks have relatively high L {sub X} in the pulsar state (>10{sup 32} erg s{sup –1}).

  19. Interplanetary spacecraft navigation using pulsars

    CERN Document Server

    Deng, X P; You, X P; Li, M T; Keith, M J; Shannon, R M; Coles, W; Manchester, R N; Zheng, J H; Yu, X Z; Gao, D; Wu, X; Chen, D

    2013-01-01

    We demonstrate how observations of pulsars can be used to help navigate a spacecraft travelling in the solar system. We make use of archival observations of millisecond pulsars from the Parkes radio telescope in order to demonstrate the effectiveness of the method and highlight issues, such as pulsar spin irregularities, which need to be accounted for. We show that observations of four millisecond pulsars every seven days using a realistic X-ray telescope on the spacecraft throughout a journey from Earth to Mars can lead to position determinations better than approx. 20km and velocity measurements with a precision of approx. 0.1m/s.

  20. Multi-wavelength properties of IGR J05007-7047 (LXP 38.55) and identification as a Be X-ray binary pulsar in the LMC

    CERN Document Server

    Vasilopoulos, G; Delvaux, C; Sturm, R; Udalski, A

    2016-01-01

    We report on the results of a $\\sim$40 d multi-wavelength monitoring of the Be X-ray binary system IGR J05007-7047 (LXP 38.55). During that period the system was monitored in the X-rays using the Swift telescope and in the optical with multiple instruments. When the X-ray luminosity exceeded $10^{36}$ erg/s we triggered an XMM-Newton ToO observation. Timing analysis of the photon events collected during the XMM-Newton observation reveals coherent X-ray pulsations with a period of 38.551(3) s (1 {\\sigma}), making it the 17$^{th}$ known high-mass X-ray binary pulsar in the LMC. During the outburst, the X-ray spectrum is fitted best with a model composed of an absorbed power law ($\\Gamma =0.63$) plus a high-temperature black-body (kT $\\sim$ 2 keV) component. By analysing $\\sim$12 yr of available OGLE optical data we derived a 30.776(5) d optical period, confirming the previously reported X-ray period of the system as its orbital period. During our X-ray monitoring the system showed limited optical variability wh...

  1. Gamma-ray observations of the Be/pulsar binary 1A 0535+262 during a giant X-ray outburst

    CERN Document Server

    Acciari, V A; Araya, M; Arlen, T; Aune, T; Beilicke, M; Benbow, W; Bradbury, S M; Buckley, J H; Bugaev, V; Byrum, K; Cannon, A; Cesarini, A; Ciupik, L; Collins-Hughes, E; Cui, W; Dickherber, R; Duke, C; Falcone, A; Finley, J P; Fortson, L; Furniss, A; Galante, N; Gall, D; Godambe, S; Griffin, S; Guenette, R; Gyuk, G; Hanna, D; Holder, J; Hughes, G; Hui, C M; Humensky, T B; Imran, A; Kaaret, P; Kertzman, M; Krawczynski, H; Krennrich, F; Madhavan, A S; Maier, G; Majumdar, P; McArthur, S; Moriarty, P; Ong, R A; Otte, A N; Pandel, D; Park, N; Perkins, J S; Pohl, M; Prokoph, H; Quinn, J; Ragan, K; Reyes, L C; Reynolds, P T; Roache, E; Rose, H J; Saxon, D B; Sembroski, G H; Senturk, G Demet; Smith, A W; Tešić, G; Theiling, M; Thibadeau, S; Varlotta, A; Vincent, S; Vivier, M; Wakely, S P; Ward, J E; Weekes, T C; Weinstein, A; Weisgarber, T; Weng, S; Williams, D A; Wood, M; Zitzer, B

    2011-01-01

    Giant X-ray outbursts, with luminosities of about $ 10^{37}$ erg s$^{-1}$, are observed roughly every 5 years from the nearby Be/pulsar binary 1A 0535+262. In this article, we present observations of the source with VERITAS at very-high energies (VHE; E$>$100 GeV) triggered by the X-ray outburst in December 2009. The observations started shortly after the onset of the outburst, and they provided comprehensive coverage of the episode, as well as the 111-day binary orbit. No VHE emission is evident at any time. We also examined data from the contemporaneous observations of 1A 0535+262 with the Fermi/LAT at high energy photons (HE; E$>$0.1 GeV) and failed to detect the source at GeV energies. The X-ray continua measured with the Swift/XRT and the RXTE/PCA can be well described by the combination of blackbody and Comptonized emission from thermal electrons. Therefore, the gamma-ray and X-ray observations suggest the absence of a significant population of non-thermal particles in the system. This distinguishes 1A~...

  2. X-shaped radio galaxies as observational evidence for the interaction of supermassive binary black holes and accretion disk at pc scale

    CERN Document Server

    Liu, F K

    2004-01-01

    A supermassive black hole binary may form during galaxy mergering. we investigate the interaction of the supermassive binary black holes (SMBBHs) and an accretion disk and show that the detected X-shaped structure in some FRII radio galaxies may be due to the interaction-realignment of inclined binary and accretion disk occurred within the pc scale of the galaxy center. We compare in detail the model and observations and show that the configuration is consistent very well with the observations of X-shaped radio sources. X-shaped radio feature form only in FRII radio sources due to the strong interaction between the binary and a standard disk, while the absence of X-shaped FRI radio galaxies is due to that the interaction between the binary and the radiatively inefficient accretion flow in FRI radio sources is negligible. It is suggested that the binary would keep misaligned with the outer disk for most of the life time of FRII radio galaxies and the orientation of jet in most FRII radio galaxies distributes r...

  3. On the puzzling high-energy pulsations of the energetic radio-quiet $\\gamma$-ray pulsar J1813$-$1246

    CERN Document Server

    Marelli, M; Pizzocaro, D; De Luca, A; Wood, K S; Caraveo, P; Salvetti, D; Parkinson, P M Saz; Acero, F

    2014-01-01

    We have analyzed the new deep {\\it XMM-Newton} and {\\it Chandra} observations of the energetic radio-quiet pulsar J1813$-$1246. The X-ray spectrum is non-thermal, very hard and absorbed. Based on spectral considerations, we propose that J1813 is located at a distance further than 2.5 kpc. J1813 is highly pulsed in the X-ray domain, with a light curve characterized by two sharp, asymmetrical peaks, separated by 0.5 in phase. We detected no significant X-ray spectral changes during the pulsar phase. We extended the available {\\it Fermi} ephemeris to five years. We found two glitches. The $\\gamma$-ray lightcurve is characterized by two peaks, separated by 0.5 in phase, with a bridge in between and no off-pulse emission. The spectrum shows clear evolution in phase, being softer at the peaks and hardenning towards the bridge. The X-ray peaks lag the $\\gamma$-ray ones by 0.25 in phase. We found a hint of detection in the 30-500 keV band with {\\it INTEGRAL} IBIS/ISGRI, that is consistent with the extrapolation of bo...

  4. High-energy observations of the millisecond pulsar PSR J0218+4232

    NARCIS (Netherlands)

    Verbunt, F; Kuiper, L; Belloni, T; Johnston, HM; deBruyn, AG; Hermsen, W; vanderKlis, M

    1996-01-01

    The very luminous millisecond binary radio pulsar PSR J0218+4232 has been detected in soft X-rays, at a luminosity of 8.4 x 10(32)erg s(-1) between 0.1 - 2.4 keV. The EGRET source 2EG J0220+4228 has a position which is consistent with that of PSR J0218+4232. Both the X-ray source and the gamma-ray s

  5. A 20 cm Search for Pulsars in Globular Clusters with Arecibo and the GBT

    CERN Document Server

    Hessels, J W T; Freire, P C C; Kaspi, V M; Lorimer, D R; Ransom, S M; Stairs, I H; Backer, Donald C.; Freire, Paulo C.C.; Hessels, Jason W.T.; Kaspi, Victoria M.; Lorimer, Duncan R.; Ransom, Scott M.; Stairs, Ingrid H.

    2004-01-01

    We are conducting deep searches for radio pulsations at L-band (~ 20cm) towards more than 30 globular clusters using the 305m Arecibo telescope in Puerto Rico and the 100m Green Bank Telescope in West Virginia. With roughly three quarters of our search data analyzed, we have discovered 12 new millisecond pulsars, 11 of which are in binary systems, and at least three of which eclipse. We have timing solutions for several of these systems.

  6. On the formation of eccentric millisecond pulsars with helium white-dwarf companions

    CERN Document Server

    Antoniadis, John

    2014-01-01

    Millisecond pulsars (MSPs) orbiting helium white-dwarfs (WD) in eccentric orbits challenge the established binary-evolution paradigm that predicts efficient orbital circularization during the mass-transfer episode that spins up the pulsar. Freire and Tauris (2014) recently proposed that these binary MSPs may instead form from the rotationally-delayed accretion-induced collapse of a massive WD. This scenario predicts that eccentric systems preferably host low-mass pulsars and travel with small systemic velocities -- in tension with new observational constraints. Here, I show that a substantial growth in eccentricity may alternatively arise from the dynamical interaction of the binary with a circumbinary disk. Such a disk may form from ejected donor material during hydrogen flash episodes, when the neutron star is already an active radio pulsar and tidal forces can no longer circularize the binary. I demonstrate that a short-lived (10^4-10^5 yrs disk can result to eccentricities of e ~ 0.01-0.15 for orbital per...

  7. Radio Polarization Observations of the Snail: A Crushed Pulsar Wind Nebula in G327.1-1.1 with a Highly Ordered Magnetic Field

    CERN Document Server

    Ma, Y K; Bucciantini, N; Slane, P O; Gaensler, B M; Temim, T

    2016-01-01

    Pulsar wind nebulae (PWNe) are suggested to be acceleration sites of cosmic rays in the Galaxy. While the magnetic field plays an important role in the acceleration process, previous observations of magnetic field configurations of PWNe are rare, particularly for evolved systems. We present a radio polarization study of the "Snail" PWN inside the supernova remnant G327.1-1.1 using the Australia Telescope Compact Array. This PWN is believed to have been recently crushed by the supernova (SN) reverse shock. The radio morphology is composed of a main circular body with a finger-like protrusion. We detected a strong linear polarization signal from the emission, which reflects a highly ordered magnetic field in the PWN and is in contrast to the turbulent environment with a tangled magnetic field generally expected from hydrodynamical simulations. This could suggest that the characteristic turbulence scale is larger than the radio beam size. We built a toy model to explore this possibility, and found that a simulat...

  8. A Hybrid Spin-Down Model and its Application to the Radio Quiet X-Ray Pulsar 1E 1207.4-5209

    Institute of Scientific and Technical Information of China (English)

    张灵娣; 彭秋和; 罗新炼

    2003-01-01

    A series of newly published papers are focusing on the formation of the absorption features discovered by Chandra and XMM-Newton from the young radio quiet x-ray pulsar 1E 1207.4-5209. We try to interpret it as cyclotron absorption lines since this possibility could not be ruled out. With new development and application of a hybrid model, i.e., the magnetic dipole spin-down model combined with the neutrino cyclotron radiation spin-down model, we can easily avoid the contradiction between the normal rotation energy loss rate and the relatively lower magnetic field, and then we obtain the possible initial spin period (~0.420s). We suppose that the progenitor of 1E 1207.4-5209 may be a white dwarf.

  9. The relativistic pulsar-white dwarf binary PSR J1738+0333 I. Mass determination and evolutionary history

    CERN Document Server

    Antoniadis, J; Koester, D; Freire, P C C; Wex, N; Tauris, T M; Kramer, M; Bassa, C G

    2012-01-01

    PSR J1738+0333 is one of the four millisecond pulsars known to be orbited by a white dwarf companion bright enough for optical spectroscopy. Of these, it has the shortest orbital period, making it especially interesting for a range of astrophysical and gravity related questions. We present a spectroscopic and photometric study of the white dwarf companion and infer its radial velocity curve, effective temperature, surface gravity and luminosity. We find that the white dwarf has properties consistent with those of low-mass white dwarfs with thick hydrogen envelopes, and use the corresponding mass-radius relation to infer its mass; M_WD = 0.181 +/- +0.007/-0.005 solar masses. Combined with the mass ratio q=8.1 +/- 0.2 inferred from the radial velocities and the precise pulsar timing ephemeris, the neutron star mass is constrained to M_PSR = 1.47 +/- +0.07/-0.06 solar masses. Contrary to expectations, the latter is only slightly above the Chandrasekhar limit. We find that, even if the birth mass of the neutron s...

  10. CXOU J005047.9-731817: a 292-s X-ray binary pulsar in the Small Magellanic Cloud

    CERN Document Server

    Esposito, P; Sidoli, L; Castillo, G A Rodríguez; Masetti, N; D'Avanzo, P; Campana, S

    2013-01-01

    We report on the discovery of a transient X-ray pulsars, located in the Small Magellanic Cloud, with a pulse period of 292 s. A series of Chandra pointings fortuitously recorded in 2010 April-May the occurrence of a two-weeks-long outburst, during which the source luminosity increased by a factor of about 100, reaching a peak of ~1E36 erg/s (for a distance of 61 kpc). Complex-shape and energy-dependent pulsations were detected close to the outburst peak and during the very first part of its decay phase. During the outburst, the phase-averaged spectrum of the pulsar was well described by an absorbed power law with photon index ~0.6, but large variations as a function of phase were present. The source was also detected by Chandra several times (during 2002, 2003, 2006, and 2010) at a quiescent level of ~1E34 erg/s. In 2012 we performed an infrared photometric follow-up of the R ~ 15 mag optical counterpart with the ESO/VLT and a spectroscopic observation by means of the CTIO telescope. The optical spectra sugge...

  11. "Missing Link" Revealing Fast-Spinning Pulsar Mysteries

    Science.gov (United States)

    2009-05-01

    Astronomers have discovered a unique double-star system that represents a "missing link" stage in what they believe is the birth process of the most rapidly-spinning stars in the Universe -- millisecond pulsars. "We've thought for some time that we knew how these pulsars get 'spun up' to rotate so swiftly, and this system looks like it's showing us the process in action," said Anne Archibald, of McGill University in Montreal, Canada. Pulsar and Companion Neutron star with accretion disk (left) drawing material from companion star (right). CREDIT:Bill Saxton, NRAO/AUI/NSF Animations of this system and its evolution. Pulsars are superdense neutron stars, the remnants left after massive stars have exploded as supernovae. Their powerful magnetic fields generate lighthouse-like beams of light and radio waves that sweep around as the star rotates. Most rotate a few to tens of times a second, slowing down over thousands of years. However, some, dubbed millisecond pulsars, rotate hundreds of times a second. Astronomers believe the fast rotation is caused by a companion star dumping material onto the neutron star and spinning it up. The material from the companion would form a flat, spinning disk around the neutron star, and during this period, the radio waves characteristic of a pulsar would not be seen coming from the system. As the amount of matter falling onto the neutron star decreased and stopped, the radio waves could emerge, and the object would be recognized as a pulsar. This sequence of events is apparently what happened with a binary-star system some 4000 light-years from Earth. The millisecond pulsar in this system, called J1023, was discovered by the National Science Foundation's (NSF) Robert C. Byrd Green Bank Telescope (GBT) in West Virginia in 2007 in a survey led by astronomers at West Virginia University and the National Radio Astronomy Observatory (NRAO). The astronomers then found that the object had been detected by NSF's Very Large Array (VLA) radio

  12. Nonlinear reflection from the surface of neutron stars and features of radio emission from the pulsar in the Crab nebula

    Science.gov (United States)

    Kontorovich, V. M.

    2016-08-01

    There are no explanations for the high-frequency component of the emission from the pulsar in the Crab nebula, but it may be a manifestation of instability in nonlinear reflection from the star's surface. Radiation from relativistic positrons flying from the magnetosphere to the star and accelerated by the electric field of the polar gap is reflected. The instability involves stimulated scattering on surface waves.

  13. X-ray Measurement of the Spin-Down of Calvera: a Radio- and Gamma-ray-Quiet Pulsar

    CERN Document Server

    Halpern, J P; Gotthelf, E V

    2013-01-01

    We measure spin-down of the 59 ms X-ray pulsar Calvera by comparing the XMM-Newton discovery data from 2009 with new Chandra timing observations taken in 2013. Its period derivative is P-dot = (3.19+/-0.08)e-15, which corresponds to spin-down luminosity E-dot = 6.1e35 erg/s, characteristic age tau_c = P/2P-dot = 2.9e5 yr, and surface dipole magnetic field strength B_s = 4.4e11 G. These values rule out a mildly recycled pulsar, but Calvera could be an orphaned central compact object (anti-magnetar), with a magnetic field that was initially buried by supernova debris and is now reemerging and approaching normal strength. We also performed unsuccessful searches for high-energy gamma-rays from Calvera in both imaging and timing of >100 MeV Fermi photons. Even though the distance to Calvera is uncertain by an order of magnitude, an upper limit of d < 2 kpc inferred from X-ray spectra implies a gamma-ray luminosity limit of < 3.3e32 erg/s, which is less than that of any pulsar of comparable E-dot. Calvera sha...

  14. Pulsar Timing Techniques

    CERN Document Server

    Lommen, Andrea N

    2013-01-01

    We describe the procedure, nuances, issues, and choices involved in creating times-of-arrival (TOAs), residuals and error bars from a set of radio pulsar timing data. We discuss the issue of mis-matched templates, the problem that wide- bandwidth backends introduce, possible solutions to that problem, and correcting for offsets introduced by various observing systems.

  15. RY Scuti: Infrared and radio observations of the mass-loss wind of a massive binary star system

    Science.gov (United States)

    Gehrz, R. D.; Hayward, T. L.; Houck, J. R.; Miles, J. W.; Hjellming, R. M.; Jones, T. J.; Woodward, Charles E.; Prentice, Ricarda; Forrest, W. J.; Libonate, S.

    1995-01-01

    We report infrared (IR) imaging, IR photometry, IR spectroscopy, optical/IR photopolarimetry, and Very Large Array (VLA) radio observations of the peculiar binary star RY Scuti. These observations provide an unprecedented view of the detailed spatial structure of the equatorial mass-loss wind of a massive, luminous, 'overcontact' binary system. The binary star (0.43 AU separation) is surrounded by a flattened equatorial disk with an outer radius of approximately = 3 x 10(exp 16) cm (2000 AU) that emits strongly in the IR and radio. The inside of the disk is ionized and emits free-free radiation from hydrogen and 12.8 micrometers forbidden-line emission from (Ne II); the outside of the disk emits thermal radiation from silicate dust. Radio continuum emission is also produced in a compact H II region surrounding the binary. The dust may have a polycyclic aromatic hydrocarbon (PAH) component. We use a rudimentary geometric model in which the thermal IR and radio emission from the disk are assumed to arise in a pair of concentric toroidal rings to estimate the physical properties of the disk. The mean radius of the ionized gas toroid is approximately = 1.3 x 10(exp 16) cm (870 AU), and the mean radius of the dust toroid is approximately = 2.2 x 10(exp 16) cm (1470 AU). RY Scuti has a small intrinsic polarization, with the electric vector perpendicular to the equatorial disk, that is probably caused by electron scattering from hot gas close to the central binary. We conclude that neon in the nebula is overabundant with respect to hydrogen and helium by a factor of between 1.6 and 10. Our IR/radio image data suggest that the circumstellar disk is part of an extensive radiation driven mass-loss outflow that is strongly confined to the equatorial plane of the binary system. The sharp spatial separation of the outer dust torous from the inner ionized gas torus confirms earlier suggestions that dust formation in the circumstellar ejecta of very hot stars must occur in

  16. Luminosity Dependent Study of the High Mass X-ray Binary Pulsar 4U 0114 + 65 with ASCA

    Indian Academy of Sciences (India)

    U. Mukherjee; B. Paul

    2006-03-01

    Here we report the spectral characteristics of the high and low states of the pulsar 4U 0114+65 and examine the change in the parameters of the spectral model. A power lawand a photoelectric absorption by material along the line of sight together with a high energy cut-off suffice to describe the continuum spectrum in both the states. A fluorescence iron line at ∼ 6.4 keV is present in the high as well as in the low state, though it is less intense in the latter. The photon index, cut-off energy and e-folding energy values hardly show any discernible change over the states. We compare these spectral characteristics as observed with ASCA with those of other satellites. We also compare the spectral characteristics of 4U 0114 + 650 with other X-ray sources which show intensity variation at different time scales.

  17. NuSTAR Observations of the State Transition of Millisecond Pulsar Binary PSR J1023+0038

    DEFF Research Database (Denmark)

    Tendulkar, Shriharsh P.; Yang, Chengwei; An, Hongjun

    2014-01-01

    disappearance of the pulsar, the 3-79 keV X-ray spectrum was well fit by a simple power law with a photon index of Gamma = 1.17(-0.07)(+0.08) (at 90% confidence) with a 3-79 keV luminosity of 7.4 +/- 0.4 x 10(32) erg s(-1). Significant orbital modulation was observed with a modulation fraction of 36% +/- 10......-60 s. No change in hardness ratio was observed during the dips. Consecutive dip separations are log-normal in distribution with a typical separation of approximately 400 s. These dips are distinct from dipping activity observed in LMXBs. We compare and contrast these dips to observations of dips...... and state changes in the similar transition systems PSR J1824-2452I and XSS J1227.0-4859 and discuss possible interpretations based on the transitions in the inner disk....

  18. NuSTAR Observations of the State Transition of Millisecond Pulsar Binary PSR J1023+0038

    DEFF Research Database (Denmark)

    Tendulkar, Shriharsh P.; Yang, Chengwei; An, Hongjun

    2014-01-01

    of the pulsar, the 3-79 keV X-ray spectrum was well fit by a simple power law with a photon index of Gamma=1.17 +/-0.08 (at 90% confidence) with a 3-79 keV luminosity of 7.4+/-0.4 x 10^32 erg/s. Significant orbital modulation was observed with a modulation fraction of 36+/-10%. During the October 19....... Consecutive dip separations are log-normal in distribution with a typical separation of approximately 400 s. These dips are distinct from dipping activity observed in LMXBs. We compare and contrast these dips to observations of dips and state changes in the similar transition systems PSR J1824-2452I and XSS J......1227.0-4859 and discuss possible interpretations based on the transitions in the inner disk....

  19. A Neutron Star-White Dwarf Binary Model for Repeating Fast Radio Burst 121102

    CERN Document Server

    Gu, Wei-Min; Liu, Tong; Ma, Renyi; Wang, Junfeng

    2016-01-01

    We propose a compact binary model for the fast radio burst (FRB) repeaters, where the system consists of a magnetic white dwarf (WD) and a neutron star (NS) with strong bipolar magnetic fields. When the WD fills its Roche lobe, mass transfer will occur from the WD to the NS through the inner Lagrange point. The accreted magnetized materials may trigger magnetic reconnection when they approach the NS surface, and therefore the electrons can be accelerated to an ultra-relativistic speed. In this scenario, the curvature radiation of the electrons moving along the NS magnetic field lines can account for the characteristic frequency and the timescale of an FRB. Owing to the conservation of angular momentum, the WD may be kicked away after a burst, and the next burst may appear when the system becomes semi-detached again through the gravitational radiation. By comparing our analyses with the observations, we show that such an intermittent Roche lobe overflow mechanism can be responsible for the observed repeating b...

  20. The orthometric parameterisation of the Shapiro delay and an improved test of general relativity with binary pulsars

    CERN Document Server

    Freire, Paulo C C

    2010-01-01

    (abridged) In this paper, we express the relativistic propagational delay of light in the space-time of a binary system (commonly known as the "Shapiro delay") as a sum of harmonics of the orbital period of the system. We do this first for near-circular orbits as a natural expansion of an existing orbital model for low-eccentricity binary systems. The amplitudes of the 3rd and higher harmonics can be described by two new post-Keplerian (PK) parameters proportional to the amplitudes of the third and fourth harmonics (h_3, h_4). For high orbital inclinations we use a PK parameter proportional to the ratio of amplitudes of successive harmonics (sigma) instead of h_4. The new PK parameters are much less correlated with each other than r and s and provide a superior description of the constraints introduced by the Shapiro delay on the orbital inclination and the masses of the components of the binary (...). We extend the h_3,sigma parameterisation to eccentric binaries with high orbital inclinations. For some such...

  1. The relativistic pulsar-white dwarf binary PSR J1738+0333 II. The most stringent test of scalar-tensor gravity

    CERN Document Server

    Freire, Paulo C C; Esposito-Farèse, Gilles; Verbiest, Joris P W; Bailes, Matthew; Jacoby, Bryan A; Kramer, Michael; Stairs, Ingrid H; Antoniadis, John; Janssen, Gemma H

    2012-01-01

    (abridged) We report the results of a 10-year timing campaign on PSR J1738+0333, a 5.85-ms pulsar in a low-eccentricity 8.5-hour orbit with a low-mass white dwarf companion (...) The measurements of proper motion and parallax allow for a precise subtraction of the kinematic contribution to the observed orbital decay; this results in a significant measurement of the intrinsic orbital decay: (-25.9 +/- 3.2) \\times 10^{-15} s/s. This is consistent with the orbital decay from the emission of gravitational waves predicted by general relativity, (-27.7 +1.5/-1.9) \\times 10^{-15} s/s (...). This agreement introduces a tight upper limit on dipolar gravitational wave emission, a prediction of most alternative theories of gravity for asymmetric binary systems such as this. We use this limit to derive the most stringent constraints ever on a wide class of gravity theories, where gravity involves a scalar field contribution. When considering general scalar-tensor theories of gravity, our new bounds are more stringent tha...

  2. X-ray observations of black widow pulsars

    Energy Technology Data Exchange (ETDEWEB)

    Gentile, P. A.; McLaughlin, M. A. [Department of Physics, West Virginia University, Morgantown, WV 26506 (United States); Roberts, M. S. E. [Eureka Scientific Inc., 2452 Delmer Street, Suite 100, Oakland, CA 94602-3017 (United States); Camilo, F. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Hessels, J. W. T. [ASTRON, The Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA, Dwingeloo (Netherlands); Kerr, M. [Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, CA 94305 (United States); Ransom, S. M. [National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States); Ray, P. S. [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States); Stairs, I. H. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1 (Canada)

    2014-03-10

    We describe the first X-ray observations of five short orbital period (P{sub B} < 1 day), γ-ray emitting, binary millisecond pulsars (MSPs). Four of these—PSRs J0023+0923, J1124–3653, J1810+1744, and J2256–1024—are 'black-widow' pulsars, with degenerate companions of mass <<0.1 M {sub ☉}, three of which exhibit radio eclipses. The fifth source, PSR J2215+5135, is an eclipsing 'redback' with a near Roche-lobe filling ∼0.2 solar mass non-degenerate companion. Data were taken using the Chandra X-Ray Observatory and covered a full binary orbit for each pulsar. Two pulsars, PSRs J2215+5135 and J2256–1024, show significant orbital variability while PSR J1124–3653 shows marginal orbital variability. The lightcurves for these three pulsars have X-ray flux minima coinciding with the phases of the radio eclipses. This phenomenon is consistent with an intrabinary shock emission interpretation for the X-rays. The other two pulsars, PSRs J0023+0923 and J1810+1744, are fainter and do not demonstrate variability at a level we can detect in these data. All five spectra are fit with three separate models: a power-law model, a blackbody model, and a combined model with both power-law and blackbody components. The preferred spectral fits yield power-law indices that range from 1.3 to 3.2 and blackbody temperatures in the hundreds of eV. The spectrum for PSR J2215+5135 shows a significant hard X-ray component, with a large number of counts above 2 keV, which is additional evidence for the presence of intrabinary shock emission. This is similar to what has been detected in the low-mass X-ray binary to MSP transition object PSR J1023+0038.

  3. Observing pulsars and fast transients with LOFAR

    CERN Document Server

    Stappers, B W; Alexov, A; Anderson, K; Coenen, T; Hassall, T; Karastergiou, A; Kondratiev, V I; Kramer, M; van Leeuwen, J; Mol, J D; Noutsos, A; Romein, J W; Weltevrede, P; Fender, R; Wijers, R A M J; Bähren, L; Bell, M E; Broderick, J; Daw, E J; Dhillon, V S; Eislöffel, J; Falcke, H; Griessmeier, J; Law, C; Markoff, S; Miller-Jones, J C A; Scheers, B; Spreeuw, H; Swinbank, J; ter Veen, S; Wise, M W; Wucknitz, O; Zarka, P; Anderson, J; Asgekar, A; Avruch, I M; Beck, R; Bennema, P; Bentum, M J; Best, P; Bregman, J; Brentjens, M; van de Brink, R H; Broekema, P C; Brouw, W N; Brüggen, M; de Bruyn, A G; Butcher, H R; Ciardi, B; Conway, J; Dettmar, R -J; van Duin, A; van Enst, J; Garrett, M; Gerbers, M; Grit, T; Gunst, A; van Haarlem, M P; Hamaker, J P; Heald, G; Hoeft, M; Holties, H; Horneffer, A; Koopmans, L V E; Kuper, G; Loose, M; Maat, P; McKay-Bukowski, D; McKean, J P; Miley, G; Morganti, R; Nijboer, R; Noordam, J E; Norden, M; Olofsson, H; Pandey-Pommier, M; Polatidis, A; Reich, W; Röttgering, H; Schoenmakers, A; Sluman, J; Smirnov, O; Steinmetz, M; Sterks, C G M; Tagger, M; Tang, Y; Vermeulen, R; Vermaas, N; Vogt, C; de Vos, M; Wijnholds, S J; Yatawatta, S; Zensus, A

    2011-01-01

    Low frequency radio waves, while challenging to observe, are a rich source of information about pulsars. The LOw Frequency ARray (LOFAR) is a new radio interferometer operating in the lowest 4 octaves of the ionospheric "radio window": 10-240MHz, that will greatly facilitate observing pulsars at low radio frequencies. Through the huge collecting area, long baselines, and flexible digital hardware, it is expected that LOFAR will revolutionize radio astronomy at the lowest frequencies visible from Earth. LOFAR is a next-generation radio telescope and a pathfinder to the Square Kilometre Array (SKA), in that it incorporates advanced multi-beaming techniques between thousands of individual elements. We discuss the motivation for low-frequency pulsar observations in general and the potential of LOFAR in addressing these science goals. We present LOFAR as it is designed to perform high-time-resolution observations of pulsars and other fast transients, and outline the various relevant observing modes and data reduct...

  4. Pulsars in FIRST Observations

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    We identify 16 pulsars from the Survey of Faint Images of the Radio Sky at Twenty-cm (FIRST) at 1.4 GHz. Their positions and total flux densities are extracted from the FIRST catalog. By comparing the source positions with those in the PSR catalog, we obtain better determined positions of PSR J1022+1001,J1518+4904, J1652+2651, and proper motion upper limits of PSR J0751+1807,J1012+5307, and J1640+2224. The proper motions of the other ten pulsars are consistent with the catalog values.

  5. Pulsar timing and general relativity

    Science.gov (United States)

    Backer, D. C.; Hellings, R. W.

    1986-01-01

    Techniques are described for accounting for relativistic effects in the analysis of pulsar signals. Design features of instrumentation used to achieve millisecond accuracy in the signal measurements are discussed. The accuracy of the data permits modeling the pulsar physical characteristics from the natural glitches in the emissions. Relativistic corrections are defined for adjusting for differences between the pulsar motion in its spacetime coordinate system relative to the terrestrial coordinate system, the earth's motion, and the gravitational potentials of solar system bodies. Modifications of the model to allow for a binary pulsar system are outlined, including treatment of the system as a point mass. Finally, a quadrupole model is presented for gravitational radiation and techniques are defined for using pulsars in the search for gravitational waves.

  6. The evolutionary status of the white dwarf companion of the binary pulsar PSR J1713+0747

    CERN Document Server

    Benvenuto, O G; De Vito, M A

    2006-01-01

    Splaver and coworkers have measured the masses of the white dwarf and the neutron star components of the PSR J1713+0747 binary system pair by Shapiro Delay. We attempt to find the original configuration of this system performing a set of binary evolution calculations to simultaneously account for the masses of both stars and the orbital period. We considered initial masses of 1.5 and 1.4 \\msun for the normal (donor) and the neutron star, respectively. We assumed two metallicity values (Z = 0.010 and 0.020), and an initial orbital period near 3 days. We assume that the neutron star is only able to retain \\lesssim 0.10 of the matter transferred by the donor star. Calculations were performed employing our binary hydro code that handles the mass transfer rate in a fully implicit way together with state-of-the-art physical ingredients, diffusion and a non-grey atmospheres. We compare the structure of the resulting white dwarfs with the characteristic age of PSR J1713+0747 finding a nice agreement with observations...

  7. High-precision timing of 42 millisecond pulsars with the European Pulsar Timing Array

    CERN Document Server

    Desvignes, G; Lentati, L; Verbiest, J P W; Champion, D J; Stappers, B W; Janssen, G H; Lazarus, P; Osłowski, S; Babak, S; Bassa, C G; Brem, P; Burgay, M; Cognard, I; Gair, J R; Graikou, E; Guillemot, L; Hessels, J W T; Jessner, A; Jordan, C; Karuppusamy, R; Kramer, M; Lassus, A; Lazaridis, K; Lee, K J; Liu, K; Lyne, A G; McKee, J; Mingarelli, C M F; Perrodin, D; Petiteau, A; Possenti, A; Purver, M B; Rosado, P A; Sanidas, S; Sesana, A; Shaifullah, G; Smits, R; Taylor, S R; Theureau, G; Tiburzi, C; van Haasteren, R; Vecchio, A

    2016-01-01

    We report on the high-precision timing of 42 radio millisecond pulsars (MSPs) observed by the European Pulsar Timing Array (EPTA). This EPTA Data Release 1.0 extends up to mid-2014 and baselines range from 7-18 years. It forms the basis for the stochastic gravitational-wave background, anisotropic background, and continuous-wave limits recently presented by the EPTA elsewhere. The Bayesian timing analysis performed with TempoNest yields the detection of several new parameters: seven parallaxes, nine proper motions and, in the case of six binary pulsars, an apparent change of the semi-major axis. We find the NE2001 Galactic electron density model to be a better match to our parallax distances (after correction from the Lutz-Kelker bias) than the M2 and M3 models by Schnitzeler (2012). However, we measure an average uncertainty of 80\\% (fractional) for NE2001, three times larger than what is typically assumed in the literature. We revisit the transverse velocity distribution for a set of 19 isolated and 57 bina...

  8. Tempo: Pulsar timing data analysis

    Science.gov (United States)

    Manchester, R.; Taylor, J.; Peters, W.; Weisberg, J.; Irwin, A.; Wex, N.; Stairs, I.; Demorest, P.; Nice, D.

    2015-09-01

    Tempo analyzes pulsar timing data. Pulse times of arrival (TOAs), pulsar model parameters, and coded instructions are read from one or more input files. The TOAs are fitted by a pulse timing model incorporating transformation to the solar-system barycenter, pulsar rotation and spin-down and, where necessary, one of several binary models. Program output includes parameter values and uncertainties, residual pulse arrival times, chi-squared statistics, and the covariance matrix of the model. In prediction mode, ephemerides of pulse phase behavior (in the form of polynomial expansions) are calculated from input timing models. Tempo is the basis for the Tempo2 (ascl:1210.015) code.

  9. Pulsar Magnetospheres and Pulsar Winds

    CERN Document Server

    Beskin, Vasily S

    2016-01-01

    Surprisingly, the chronology of nearly 50 years of the pulsar magnetosphere and pulsar wind research is quite similar to the history of our civilization. Using this analogy, I have tried to outline the main results obtained in this field. In addition to my talk, the possibility of particle acceleration due to different processes in the pulsar magnetosphere is discussed in more detail.

  10. Gamma Rays From Rotation-Powered Pulsars

    CERN Document Server

    Harding, A K

    2002-01-01

    The seven known gamma-ray pulsars represent a very small fraction of the more than 1000 presently known radio pulsars, yet they can give us valuable information about pulsar particle acceleration and energetics. Although the theory of acceleration and high-energy emission in pulsars has been studied for over 25 years, the origin of the pulsed gamma rays is a question that remains unanswered. Characteristics of the pulsars detected by the Compton Gamma-Ray Observatory could not clearly distinguish between an emission site at the magnetic poles (polar cap models) and emission from the outer magnetosphere (outer gap models). There are also a number of theoretical issues in both type of model which have yet to be resolved. The two types of models make contrasting predictions for the numbers of radio-loud and radio-quiet gamma-ray pulsars and of their spectral characteristics. GLAST will probably detect at least 50 radio-selected pulsars and possibly many more radio-quiet pulsars. With this large sample, it will b...

  11. Pulsar virtual observatory

    CERN Document Server

    Keith, M; Lyne, A; Brooke, J

    2007-01-01

    The Pulsar Virtual Observatory will provide a means for scientists in all fields to access and analyze the large data sets stored in pulsar surveys without specific knowledge about the data or the processing mechanisms. This is achieved by moving the data and processing tools to a grid resource where the details of the processing are seen by the users as abstract tasks. By developing intelligent scheduling middle-ware the issues of interconnecting tasks and allocating resources are removed from the user domain. This opens up large sets of radio time-series data to a wider audience, enabling greater cross field astronomy, in line with the virtual observatory concept. Implementation of the Pulsar Virtual Observatory is underway, utilising the UK National Grid Service as the principal grid resource.

  12. Discovery of SXP265, a Be/X-ray binary pulsar in the Wing of the Small Magellanic Cloud

    CERN Document Server

    Sturm, R; Vasilopoulos, G; Bartlett, E S; Maggi, P; Rau, A; Greiner, J; Udalski, A

    2014-01-01

    We identify a new candidate for a Be/X-ray binary in the XMM-Newton slew survey and archival Swift observations that is located in the transition region of the Wing of the Small Magellanic Cloud and the Magellanic Bridge. We investigated and classified this source with follow-up XMM-Newton and optical observations. We model the X-ray spectra and search for periodicities and variability in the X-ray observations and the OGLE I-band light curve. The optical counterpart has been classified spectroscopically, with data obtained at the SAAO 1.9 m telescope, and photometrically, with data obtained using GROND at the MPG 2.2 m telescope. The X-ray spectrum is typical of a high-mass X-ray binary with an accreting neutron star. We detect X-ray pulsations, which reveal a neutron-star spin period of P = (264.516+-0.014) s. The source likely shows a persistent X-ray luminosity of a few 10^35 erg/s and in addition type-I outbursts that indicate an orbital period of ~146 d. A periodicity of 0.867 d, found in the optical li...

  13. The evolutionary status of the white dwarf companion of the binary pulsar PSR J1713+0747

    Science.gov (United States)

    Benvenuto, O. G.; Rohrmann, R. D.; De Vito, M. A.

    2006-03-01

    Recently Splaver et al. have measured the masses of the white dwarf and the neutron star (NS) components of the PSR J1713+0747 binary system pair by means of the general relativistic effect known as Shapiro delay with very high accuracy. Employing these data we attempt to find the original configuration that evolved to the observed system. For this purpose we perform a set of binary evolution calculations trying to simultaneously account for the masses of both stars and the orbital period. In doing so, we considered normal (donor) stars with an initial mass of 1.5Msolar, while for the neutron star companion we assumed a mass of 1.4Msolar. We assumed two metallicity values for the donor star (Z= 0.010 and 0.020) and that the initial orbital period was nearly 3d. In order to get a good agreement between the masses of the models and observations we had to assume that the NS is only able to retain Benvenuto & De Vito, that handles the mass transfer rate in a fully implicit way together with state-of-the-art physical ingredients and diffusion processes. Now our code also includes a detailed non-grey treatment for the atmospheres of white dwarfs (WDs). We compare the structure of the resulting WDs with the characteristic age of PSR J1713+0747 finding a nice agreement with observations by Lundgren et al. especially for the case of a donor star with Z= 0.010. This result indicates that, at least for the purposes of this paper, the evolution of this kind of binary system is fairly well understood. The models predict that, due to diffusion, the atmosphere of the white dwarf is an almost hydrogen-pure one. We find that such structures are unable to account for the colours measured by Lundgren et al. within their error bars. Thus, in spite of the very good agreement of the model with the main characteristics of the system, we find that some discrepancies in the WD emergent radiation remain to be explained.

  14. PSR J1024-0719: A Millisecond Pulsar in an Unusual Long-Period Orbit

    CERN Document Server

    Kaplan, D L; Nice, D J; Irrgang, A; Heber, U; Arzoumanian, Z; Beklen, E; Crowter, K; DeCesar, M E; Demorest, P B; Dolch, T; Lynch, R S; McLaughlin, M A; Miller, A A; Ng, C; Pennucci, T T; Ellis, J A; Ferdman, R D; Ferrara, E C; Fonseca, E; Gentile, P A; Jones, G; Jones, M L; Kreuzer, S; Lam, M T; Levin, L; Lorimer, D R; Prince, T A; Ransom, S M; Ray, P S; Spiewak, R; Stairs, I H; Stovall, K; Swiggum, J; Zhu, W

    2016-01-01

    PSR J1024$-$0719 is a millisecond pulsar that was long thought to be isolated. However, puzzling results concerning its velocity, distance, and low rotational period derivative have led to reexamination of its properties. We present updated radio timing observations along with new and archival optical data that show PSR J1024$-$0719 is most likely in a long period (2$-$20 kyr) binary system with a low-mass ($\\approx 0.4\\,M_\\odot$) low-metallicity ($Z \\approx -0.9\\,$ dex) main sequence star. Such a system can explain most of the anomalous properties of this pulsar. We suggest that this system formed through a dynamical exchange in a globular cluster that ejected it into a halo orbit, consistent with the low observed metallicity for the stellar companion. Further astrometric and radio timing observations such as measurement of the third period derivative could strongly constrain the range of orbital parameters.

  15. Coherently dedispersed gated imaging of millisecond pulsars

    CERN Document Server

    Roy, Jayanta

    2013-01-01

    Motivated by the need for rapid localisation of newly discovered faint millisecond pulsars (MSPs) we have developed a coherently dedispersed gating correlator. This gating correlator accounts for the orbital motions of MSPs in binaries while folding the visibilities with best-fit topocentric rotational model derived from periodicity search in simultaneously generated beamformer output. Unique applications of the gating correlator for sensitive interferometric studies of MSPs are illustrated using the Giant Metrewave Radio Telescope (GMRT) interferometric array. We could unambiguously localise five newly discovered Fermi MSPs in the on-off gated image plane with an accuracy of +-1". Immediate knowledge of such precise position allows the use of sensitive coherent beams of array telescopes for follow-up timing observations, which substantially reduces the use of telescope time (~ 20X for the GMRT). In addition, precise a-priori astrometric position reduces the effect of large covariances in timing fit (with dis...

  16. The Quiescent X-Ray Properties of the Accreting Millisecond X-Ray Pulsar and Eclipsing binary Swift J1749.4-2807

    Science.gov (United States)

    Degenaar, N.; Patruno, A.; Wijnands, R.

    2012-09-01

    Swift J1749.4-2807 is a transient neutron star low-mass X-ray binary that contains an accreting millisecond X-ray pulsar spinning at 518 Hz. It is the first of its kind that displays X-ray eclipses, which holds significant promise to precisely constrain the mass of the neutron star. We report on a ~= 105 ks long XMM-Newton observation performed when Swift J1749.4-2807 was in quiescence. We detect the source at a 0.5-10 keV luminosity of sime1 × 1033(D/6.7 kpc)2 erg s-1. The X-ray light curve displays three eclipses that are consistent in orbital phase and duration with the ephemeris derived during outburst. Unlike most quiescent neutron stars, the X-ray spectrum can be adequately described with a simple power law, while a pure-hydrogen atmosphere model does not fit the data. We place an upper limit on the 0.01-100 keV thermal luminosity of the cooling neutron star of <~ 2 × 1033 erg s-1 and constrain its temperature to be <~ 0.1 keV (for an observer at infinity). Timing analysis does not reveal evidence for X-ray pulsations near the known spin frequency of the neutron star or its first overtone with a fractional rms of <~ 34% and <~ 28%, respectively. We discuss the implications of our findings for dynamical mass measurements, the thermal state of the neutron star, and the origin of the quiescent X-ray emission.

  17. Testing Gravity with Pulsars in the SKA Era

    CERN Document Server

    Shao, Lijing; Antoniadis, John; Deller, Adam T; Freire, Paulo C C; Hessels, Jason W T; Janssen, Gemma H; Kramer, Michael; Kunz, Jutta; Lämmerzahl, Claus; Perlick, Volker; Possenti, Andrea; Ransom, Scott; Stappers, Benjamin W; van Straten, Willem

    2015-01-01

    The Square Kilometre Array (SKA) will use pulsars to enable precise measurements of strong gravity effects in pulsar systems, which yield tests of gravitational theories that cannot be carried out anywhere else. The Galactic census of pulsars will discover dozens of relativistic pulsar systems, possibly including pulsar -- black hole binaries which can be used to test the "cosmic censorship conjecture" and the "no-hair theorem". Also, the SKA's remarkable sensitivity will vastly improve the timing precision of millisecond pulsars, allowing probes of potential deviations from general relativity (GR). Aspects of gravitation to be explored include tests of strong equivalence principles, gravitational dipole radiation, extra field components of gravitation, gravitomagnetism, and spacetime symmetries.

  18. A Radio-Selected Black Hole X-ray Binary Candidate in the Milky Way Globular Cluster M62

    CERN Document Server

    Chomiuk, Laura; Maccarone, Thomas J; Miller-Jones, James C A; Heinke, Craig; Noyola, Eva; Seth, Anil C; Ransom, Scott

    2013-01-01

    We report the discovery of a candidate stellar-mass black hole in the Milky Way globular cluster M62. We detected the black hole candidate, which we term M62-VLA1, in the core of the cluster using deep radio continuum imaging from the Karl G. Jansky Very Large Array. M62-VLA1 is a faint source, with a flux density of 18.7 +/- 1.9 microJy at 6.2 GHz and a flat radio spectrum (alpha=-0.24 +/- 0.42, for S_nu = nu^alpha). M62 is the second Milky Way cluster with a candidate stellar-mass black hole; unlike the two candidate black holes previously found in the cluster M22, M62-VLA1 is associated with a Chandra X-ray source, supporting its identification as a black hole X-ray binary. Measurements of its radio and X-ray luminosity, while not simultaneous, place M62-VLA1 squarely on the well-established radio--X-ray correlation for stellar-mass black holes. In archival Hubble Space Telescope imaging, M62-VLA1 is coincident with a star near the lower red giant branch. This possible optical counterpart shows a blue exce...

  19. GOALS, STRATEGIES AND FIRST DISCOVERIES OF AO327, THE ARECIBO ALL-SKY 327 MHz DRIFT PULSAR SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Deneva, J. S. [Arecibo Observatory, HC3 Box 53995, Arecibo, PR 00612 (United States); Stovall, K.; Martinez, J. G.; Jenet, F. [Center for Advanced Radio Astronomy, Department of Physics and Astronomy, University of Texas at Brownsville, Brownsville, TX 78520 (United States); McLaughlin, M. A.; Bates, S. D.; Bagchi, M. [Department of Physics, West Virginia University, 111 White Hall, Morgantown, WV 26506 (United States); Freire, P. C. C. [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany)

    2013-09-20

    We report initial results from AO327, a drift survey for pulsars with the Arecibo telescope at 327 MHz. The first phase of AO327 will cover the sky at declinations of –1° to 28°, excluding the region within 5° of the Galactic plane, where high scattering and dispersion make low-frequency surveys sub-optimal. We record data from a 57 MHz bandwidth with 1024 channels and 125 μs sampling time. The 60 s transit time through the AO327 beam means that the survey is sensitive to very tight relativistic binaries even with no acceleration searches. To date we have detected 44 known pulsars with periods ranging from 3 ms to 2.21 s and discovered 24 new pulsars. The new discoveries include 3 ms pulsars, three objects with periods of a few tens of milliseconds typical of young as well as mildly recycled pulsars, a nuller, and a rotating radio transient. Five of the new discoveries are in binary systems. The second phase of AO327 will cover the sky at declinations of 28°-38°. We compare the sensitivity and search volume of AO327 to the Green Bank North Celestial Cap survey and the GBT350 drift survey, both of which operate at 350 MHz.

  20. Goals, Strategies and First Discoveries of AO327, the Arecibo All-Sky 327 MHz Drift Pulsar Survey

    CERN Document Server

    Deneva, J S; McLaughlin, M A; Bates, S D; Freire, P C C; Martinez, J G; Jenet, F; Bagchi, M

    2013-01-01

    We report initial results from AO327, a drift survey for pulsars with the Arecibo telescope at 327 MHz. The first phase of AO327 will cover the sky at declinations of -1 to 28 degrees, excluding the region within 5 degrees of the Galactic plane, where high scattering and dispersion make low-frequency surveys sub-optimal. We record data from a 57 MHz bandwidth with 1024 channels and 125 us sampling time. The 60 s transit time through the AO327 beam means that the survey is sensitive to very tight relativistic binaries even with no acceleration searches. To date we have detected 44 known pulsars with periods ranging from 3 ms to 2.21 s and discovered 24 new pulsars. The new discoveries include three millisecond pulsars, three objects with periods of a few tens of milliseconds typical of young as well as mildly recycled pulsars, a nuller, and a rotating radio transient. Five of the new discoveries are in binary systems. The second phase of AO327 will cover the sky at declinations of 28 to 38 degrees. We compare ...