DETECTION OF VERY HARD γ -RAY SPECTRUM FROM THE TEV BLAZAR MRK 501
- Department of High Energy Physics, Tata Institute of Fundamental Research, Mumbai 400005 (India)
- Institute for Theoretical Physics and Astrophysics, Universität Würzburg, D-97074 Würzburg (Germany)
- UM-DAE Center for Excellence in Basic Sciences, Mumbai 400098 (India)
- ETH Zurich, Institute for Particle Physics, Otto-Stern-Weg 5, 8093 Zurich (Switzerland)
The occasional hardening of the GeV-to-TeV spectrum observed from the blazar Mrk 501 has reopened the debate on the physical origin of radiation and particle acceleration processes in TeV blazars. We have used the ∼7 years of Fermi -LAT data to search for the time intervals with unusually hard spectra from the nearby TeV blazar Mrk 501. We detected hard spectral components above 10 GeV with photon index <1.5 at a significance level of more than 5 sigma on 17 occasions, each with 30 day integration time. The photon index of the hardest component reached a value of 0.89 ± 0.29. We interpret these hard spectra as signatures of intermittent injection of sharply peaked and localized particle distributions from the base of the jet.
- OSTI ID:
- 22660988
- Journal Information:
- Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 832; ISSN ASJOAB; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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