VERITAS discovery of > 200 GeV gamma-ray emission from the intermediate-frequency-peaked BL Lacertae object W Comae


Creative Commons License

Acciari V. A. , Aliu E., Beilicke M., Benbow W., Boettcher M., Bradbury S. M. , ...More

ASTROPHYSICAL JOURNAL LETTERS, vol.684, no.2, 2008 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 684 Issue: 2
  • Publication Date: 2008
  • Doi Number: 10.1086/592244
  • Title of Journal : ASTROPHYSICAL JOURNAL LETTERS
  • Keywords: BL Lacertae objects : individual (W Comae), gamma rays : observations, HIGH-ENERGY EMISSION, RADIO-SOURCES, EGRET, ASTRONOMY, SPECTRA, BLAZARS

Abstract

We report the detection of very high energy gamma- ray emission from the intermediate- frequency- peaked BL Lacertae object W Comae (z = 0.102) by VERITAS. The source was observed between 2008 January and April. A strong outburst of gamma-ray emission was measured in the middle of March, lasting for only 4 days. The energy spectrum measured during the two highest flare nights is fit by a power law and is found to be very steep, with a differential photon spectral index of Gamma = 3.81 +/- 0.35(stat) +/- 0.34(syst). The integral photon flux above 200 GeV during those two nights corresponds to roughly 9% of the flux from the Crab Nebula. Quasi-simultaneous Swift observations at X-ray energies were triggered by the VERITAS observations. The spectral energy distribution of the flare data can be described by synchrotron self-Compton (SSC) or external Compton (EC) leptonic jet models.