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Register a new userPrecise Gamma-Ray Timing and Radio Observations of 17 Fermi Gamma-Ray Pulsars
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We present precise phase-connected pulse timing solutions for 16 gamma-ray-selected pulsars recently discovered using the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope plus one very faint radio pulsar (PSR J1124-5916) that is more effectively timed with the LAT. We describe the analysis techniques including a maximum likelihood method for determining pulse times of arrival from unbinned photon data. A major result of this work is improved position determinations, which are crucial for multi-wavelength follow up. For most of the pulsars, we overlay the timing localizations on X-ray images from Swift and describe the status of X-ray counterpart associations. We report glitches measured in PSRs J0007+7303, J1124-5916, and J1813-1246. We analyze a new 20 ks Chandra ACIS observation of PSR J0633+0632 that reveals an arcminute-scale X-ray nebula extending to the south of the pulsar. We were also able to precisely localize the X-ray point source counterpart to the pulsar and find a spectrum that can be described by an absorbed blackbody or neutron star atmosphere with a hard powerlaw component. Another Chandra ACIS image of PSR J1732-3131 reveals a faint X-ray point source at a location consistent with the timing position of the pulsar. Finally, we present a compilation of new and archival searches for radio pulsations from each of the gamma-ray-selected pulsars as well as a new Parkes radio observation of PSR J1124-5916 to establish the gamma-ray to radio phase offset.
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L. Guillemot (for the Fermi LAT Collaboration
, for the Fermi Pulsarn Search Consortium
,
2012
Observations of pulsars with the Large Area Telescope (LAT) on the Fermi satellite have revolutionized our view of the gamma-ray pulsar population. For the first time, a large number of young gamma-ray pulsars have been discovered in blind searches of the LAT data. More generally, the LAT has discovered many new gamma-ray sources whose properties suggest that they are powered by unknown pulsars. Radio observations of gamma-ray sources have been key to the success of pulsar studies with the LAT. For example, radio observations of LAT-discovered pulsars provide constraints on the relative beaming fractions, which are crucial for pulsar population studies. Also, radio searches of LAT sources with no known counterparts have been very efficient, with the discovery of over forty millisecond pulsars. I review radio follow-up studies of LAT-discovered pulsars and unidentified sources, and discuss some of the implications of the results.
The Large Area Telescope (LAT) on Fermi has detected ~150 gamma-ray pulsars, about a third of which were discovered in blind searches of the $gamma$-ray data. Because the angular resolution of the LAT is relatively poor and blind searches for pulsars (especially millisecond pulsars, MSPs) are very sensitive to an error in the position, one must typically scan large numbers of locations. Identifying plausible X-ray counterparts of a putative pulsar drastically reduces the number of trials, thus improving the sensitivity of pulsar blind searches with the LAT. I discuss our ongoing program of Swift, XMM-Newton, and Chandra observations of LAT unassociated sources in the context of our blind searches for gamma-ray pulsars.
The Large Area Telescope (LAT) on the Fermi satellite is the first gamma-ray instrument to discover pulsars directly via their gamma-ray emission. Roughly one third of the 117 gamma-ray pulsars detected by the LAT in its first three years were discovered in blind searches of gamma-ray data and most of these are undetectable with current radio telescopes. I review some of the key LAT results and highlight the specific challenges faced in gamma-ray (compared to radio) searches, most of which stem from the long, sparse data sets and the broad, energy-dependent point-spread function (PSF) of the LAT. I discuss some ongoing LAT searches for gamma-ray millisecond pulsars (MSPs) and gamma-ray pulsars around the Galactic Center. Finally, I outline the prospects for future gamma-ray pulsar discoveries as the LAT enters its extended mission phase, including advantages of a possible modification of the LAT observing profile.
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.
The Fermi Large Area Telescope (LAT) has been scanning the gamma-ray sky since 2008. The number of pulsars detected by the LAT now exceeds 200, making them by far the largest class of Galactic gamma-ray emitters. I discuss some of the latest pulsar discoveries made by the LAT, in particular those made since the release of the Pass 8 data.
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