Phase resolved studies of the high-energy gamma-ray emission from the Crab, Geminga, and Vela pulsars
Sep, 1997
20 pages
Published in:
- Astrophys.J. 494 (1998) 734-746
e-Print:
- astro-ph/9709123 [astro-ph]
DOI:
View in:
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Abstract: (arXiv)
Using the first three and a half years of observations from the Energetic Gamma Ray Telescope (EGRET) on board the Compton Gamma Ray Observatory (CGRO), phase-resolved analyses are performed on the emission from the three brightest high-energy gamma-ray pulsars, Crab, Geminga, and Vela. For each pulsar, it is found that there is detectable high-energy gamma-ray emission above the galactic diffuse background throughout much of the pulsar rotation cycle. A hardness ratio is introduced to characterize the evolution of the spectral index as a function of pulsar phase. While the hardest emission from the Crab and Vela pulsars comes from the bridge region between the two gamma-ray peaks, the hardest emission from Geminga corresponds to the second gamma-ray peak. For all three pulsars, phase-resolved spectra of the pulse profile components reveal that although there is a large variation in the spectral index over the pulsar phase interval, the high-energy spectral turnover, if any, occurs at roughly the same energy in each component. The high-energy gamma-ray emission from the Crab complex appears to include an unpulsed ultra-soft component of spectral index ~ -4.3 which dominates the total emission below 100 MeV. This component is consistent with the expected emission from the tail end of the Crab nebula synchrotron emission.- photon: cosmic radiation
- energy spectrum
- flux
- cosmic radiation: particle source
- pulsar
- time dependence
- statistical analysis
- experimental results
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