Showing papers by "Mallory S. E. Roberts published in 2008"
Centre national de la recherche scientifique1, University of Bordeaux2, Columbia University3, University of Manchester4, Arecibo Observatory5, Goddard Space Flight Center6, Australia Telescope National Facility7, McGill University8, West Virginia University9, National Radio Astronomy Observatory10, Stanford University11, Paris Diderot University12, University of California, Santa Cruz13
TL;DR: In this paper, the authors describe a comprehensive pulsar monitoring campaign for the Large Area Telescope (LAT) on the {\em Fermi Gamma-ray Space Telescope} (formerly GLAST).
Abstract: We describe a comprehensive pulsar monitoring campaign for the Large Area Telescope (LAT) on the {\em Fermi Gamma-ray Space Telescope} (formerly GLAST). The detection and study of pulsars in gamma rays give insights into the populations of neutron stars and supernova rates in the Galaxy, into particle acceleration mechanisms in neutron star magnetospheres, and into the ``engines'' driving pulsar wind nebulae. LAT's unprecedented sensitivity between 20 MeV and 300 GeV together with its 2.4 sr field-of-view makes detection of many gamma-ray pulsars likely, justifying the monitoring of over two hundred pulsars with large spin-down powers. To search for gamma-ray pulsations from most of these pulsars requires a set of phase-connected timing solutions spanning a year or more to properly align the sparse photon arrival times. We describe the choice of pulsars and the instruments involved in the campaign. Attention is paid to verifications of the LAT pulsar software, using for example giant radio pulses from the Crab and from PSR B1937+21 recorded at Nancay, and using X-ray data on PSR J0218+4232 from XMM-Newton. We demonstrate accuracy of the pulsar phase calculations at the microsecond level. Data Table 1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/ .
111 citations
TL;DR: In this article, the authors reported the discovery of γ-ray pulsations from PSR J2021+3651 in the 100-1500 MeV range using data from the AGILE satellite gathered over 8 months, folded on a densely sampled, contemporaneous radio ephemeris obtained for this purpose at the Green Bank Telescope.
Abstract: Discovered after the end of the Compton Gamma-Ray Observatory mission, the radio pulsar PSR J2021+3651 was long considered a likely counterpart of the high-energy γ-ray source 2CG 075+00 = 3EG J2021+3716 = GeV J2020+3658, but it could not be confirmed due to the lack of a contemporaneous radio pulsar ephemeris to fold the sparse, archival γ-ray photons. Here, we report the discovery of γ-ray pulsations from PSR J2021+3651 in the 100-1500 MeV range using data from the AGILE satellite gathered over 8 months, folded on a densely sampled, contemporaneous radio ephemeris obtained for this purpose at the Green Bank Telescope. The γ-ray pulse consists of two sharp peaks separated by 0.47 ± 0.01 cycles. The single radio pulse leads the first γ-ray peak by 0.165 ± 0.010 cycles. These properties are similar to those of other γ-ray pulsars, and the phase relationship of the peaks can be interpreted in the context of the outer-gap accelerator model for γ-ray emission. Pulse-phase-resolved images show that there is only one dominant source, AGL J2020.5+3653 = PSR J2021+3651, in the region previously containing confused sources 3EG J2021+3716 and 3EG J2016+3657.
54 citations
TL;DR: In this paper, the authors reported the discovery of gamma-ray pulsations from the radio pulsar PSR J2021+3651 in the 100-1500 MeV range using data from the AGILE satellite gathered over 8 months.
Abstract: Discovered after the end of the Compton Gamma-Ray Observatory mission, the radio pulsar PSR J2021+3651 was long considered a likely counterpart of the high-energy gamma-ray source 2CG 075+00 = 3EG J2021+3716 = GeV J2020+3658, but it could not be confirmed due to the lack of a contemporaneous radio pulsar ephemeris to fold the sparse, archival gamma-ray photons. Here, we report the discovery of gamma-ray pulsations from PSR J2021+3651 in the 100-1500 MeV range using data from the AGILE satellite gathered over 8 months, folded on a densely sampled, contemporaneous radio ephemeris obtained for this purpose at the Green Bank Telescope. The gamma-ray pulse consists of two sharp peaks separated by 0.47+/-0.01 cycles. The single radio pulse leads the first gamma-ray peak by 0.165+/-0.010 cycles. These properties are similar to those of other gamma-ray pulsars, and the phase relationship of the peaks can be interpreted in the context of the outer-gap accelerator model for gamma-ray emission. Pulse-phase resolved images show that there is only one dominant source, AGL J2020.5+3653 = PSR J2021+3651 in the region previously containing confused sources 3EG J2021+3716 and 3EG J2016+3657.
42 citations
04 Mar 2008
TL;DR: Using the Green Bank Telescope (GBT) and Pulsar Spigot at 350 MHz, a survey of the Northern Galactic Plane for pulsars and radio transients was conducted by as mentioned in this paper.
Abstract: Using the Green Bank Telescope (GBT) and Pulsar Spigot at 350 MHz, we have surveyed the Northern Galactic Plane for pulsars and radio transients This survey covers roughly 1000 square degrees of sky within 75°
26 citations
TL;DR: In this article, the authors reported the discovery of a partial 2° diameter nonthermal radio shell coincident with Taz, the pulsar wind nebula (PWN) in the error box of the apparently variable γ-ray source 3EG J1809−2328.
Abstract: We report the discovery of a partial ~2° diameter nonthermal radio shell coincident with Taz, the pulsar wind nebula (PWN) in the error box of the apparently variable γ-ray source 3EG J1809–2328. We propose that this radio shell is a newly identified supernova remnant (SNR G7.5–1.7) associated with the PWN. The SNR surrounds an amorphous region of thermal X-rays detected in archival ROSAT and ASCA observations, putting this system in the mixed-morphology class of supernova remnants. G7.5–1.7 is the fifth such supernova remnant coincident with a bright GeV source, and the fourth containing a pulsar wind nebulae.
15 citations
27 Feb 2008
TL;DR: The authors review the multi-wavelength observations of the error boxes of the EGRET sources to see what types of sources this new generation of γ-ray telescopes will be studying and note that most, if not all, of the sources seem to be related to pulsars.
Abstract: At the end of the EGRET mission, the only firmly identified sources of GeV emission in our Galaxy were a handful of young pulsars and a solar flare With the recent launch of AGILE and the imminent launch of GLAST, the sources that EGRET saw will again be studied in γ‐rays We review the multiwavelength observations of the error boxes of Galactic EGRET sources to see what types of sources this new generation of γ‐ray telescopes will be studying I note that most, if not all, of the sources seem to be related to pulsars Several are probably radio pulsars not known during the time of EGRET Others are radio‐quiet pulsars like Geminga Still others are probably the product of a pulsar wind interacting with a dense environment The rest seem to be coincident with things associated with the birth of pulsars ie supernova remnants, molecular clouds, and massive star associations
4 citations
University of Bordeaux1, Centre national de la recherche scientifique2, Columbia University3, University of Manchester4, Arecibo Observatory5, Goddard Space Flight Center6, Australia Telescope National Facility7, McGill University8, West Virginia University9, National Radio Astronomy Observatory10, Stanford University11, Paris Diderot University12, University of California, Santa Cruz13
TL;DR: In this paper, the authors describe a comprehensive pulsar monitoring campaign for the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (formerly GLAST).
Abstract: We describe a comprehensive pulsar monitoring campaign for the Large Area Telescope (LAT) on the {\em Fermi Gamma-ray Space Telescope} (formerly GLAST). The detection and study of pulsars in gamma rays give insights into the populations of neutron stars and supernova rates in the Galaxy, into particle acceleration mechanisms in neutron star magnetospheres, and into the "engines" driving pulsar wind nebulae. LAT's unprecedented sensitivity between 20 MeV and 300 GeV together with its 2.4 sr field-of-view makes detection of many gamma-ray pulsars likely, justifying the monitoring of over two hundred pulsars with large spin-down powers. To search for gamma-ray pulsations from most of these pulsars requires a set of phase-connected timing solutions spanning a year or more to properly align the sparse photon arrival times. We describe the choice of pulsars and the instruments involved in the campaign. Attention is paid to verifications of the LAT pulsar software, using for example giant radio pulses from the Crab and from PSR B1937+21 recorded at Nan\c{c}ay, and using X-ray data on PSR J0218+4232 from XMM-Newton. We demonstrate accuracy of the pulsar phase calculations at the microsecond level. Data Table 1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via this http URL .
2 citations
TL;DR: In this paper, the authors reported the discovery of a partial 2.5-1.7-degree diameter non-thermal radio shell coincident with Taz, the pulsar wind nebula (PWN) in the error box of the apparently variable gamma-ray source 3EG J1809-2328.
Abstract: We report the discovery of a partial ~2deg. diameter non-thermal radio shell coincident with Taz, the pulsar wind nebula (PWN) in the error box of the apparently variable gamma-ray source 3EG J1809-2328. We propose that this radio shell is a newly identified supernova remnant (SNR G7.5-1.7) associated with the PWN. The SNR surrounds an amorphous region of thermal X-rays detected in archival ROSAT and ASCA observations putting this system in the mixed-morphology class of supernova remnants. G7.5-1.7 is the fifth such supernova remnant coincident with a bright GeV source, and the fourth containing a pulsar wind nebulae.
1 citations
23 Apr 2008
TL;DR: In this paper, the authors examined several known low and high-mass X-ray binaries with orbital periods between tens of minutes and several days in EGRET data and found that due to significant background and low statistics, the observations were unable to constrain the modulation fraction of any of the sources.
Abstract: Several known low- and high-mass X-ray binaries with orbital periods between tens of minutes and several days were examined in EGRET data. Instrument thresholds for orbital modulation were calculated, and appropriate observations were analyzed with new software which uses maximum likelihood methods for signal detection, fully accounting for variations in EGRET exposure, as well as the structured gamma-ray background and the energy-dependent point-spread function. While some sources were not detected by EGRET at all, several were marginally detected with less than 5 σ significance. However, due to significant background and low statistics, the observations were unable to constrain the modulation fraction of any of the sources.
1 citations
National Radio Astronomy Observatory1, Purdue University2, APC by Schneider Electric3, National Research Council4, Vanderbilt University5, University of Amsterdam6, Commonwealth Scientific and Industrial Research Organisation7, Lehigh University8, United States Naval Research Laboratory9, University of Cambridge10, University of California, Los Angeles11
TL;DR: This article provided an overview of the observational properties of Galactic sources which emit across 19 orders of magnitude in energy, including pulsar wind nebulae, high mass X-ray binaries, and mixed morphology supernova remnants.
Abstract: Multi-wavelength studies at radio, infrared, optical, X-ray, and TeV wavelengths have discovered probable counterparts to many Galactic sources of GeV emission detected by EGRET. These include pulsar wind nebulae, high mass X-ray binaries, and mixed morphology supernova remnants. Here we provide an overview of the observational properties of Galactic sources which emit across 19 orders of magnitude in energy. We also present new observations of several sources.