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

Acciari, V.; Aliu, E.; Beilicke, M.; Benbow, W.; Boettcher, M.; Bradbury, S.; Buckley, J.; Bugaev, V.; Butt, Y.; Celik, O.; Cesarini, A.; Ciupik, L.; Chow, Y.; Cogan, P.; Colin, P.; Cui, W.; Daniel, M.; Ergin, TÜLÜN; Falcone, A.; Fegan, S.; Finley, J.; Finnegan, G.; Fortin, P.; Fortson, L.; Furniss, A.; Gall, D.; Gillanders, G.; Grube, J.; Guenette, R.; Gyuk, G.; Hanna, D.; Hays, E.; Holder, J.; Horan, D.; Hui, C.; Humensky, T.; Imran, A.; Kaaret, P.; Karlsson, N.; Kertzman, M.; Kieda, D.; Konopelko, A.; Krawczynski, H.; Krennrich, F.; Lang, M.; LeBohec, S.; Lee, K.; Maier, G.; McCann, A.; McCutcheon, M.; Moriarty, P.; Mukherjee, R.; Nagai, T.; Niemiec, J.; Ong, R.; Pandel, D.; Perkins, J.; Petry, D.; Pohl, M.; Quinn, J.; Ragan, K.; Reyes, L.; Reynolds, P.; Roache, E.; Rose, H.; Schroedter, M.; Sembroski, G.; Smith, A.; Steele, D.; Swordy, S.; Toner, J.; Vassiliev, V.; Wagner, R.; Wakely, S.; Ward, J.; Weekes, T.; Weinstein, A.; White, R.; Williams, D.; Wissel, S.; Wood, M.; Zitzer, B.

doi:10.1086/592244

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

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

ASTROPHYSICAL JOURNAL LETTERS, vol.684, no.2, 2008 (SCI-Expanded)

Publication Type: Article / Article
Volume: 684 Issue: 2
Publication Date: 2008
Doi Number: 10.1086/592244
Journal Name: ASTROPHYSICAL JOURNAL LETTERS
Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
Keywords: BL Lacertae objects : individual (W Comae), gamma rays : observations, HIGH-ENERGY EMISSION, RADIO-SOURCES, EGRET, ASTRONOMY, SPECTRA, BLAZARS
Middle East Technical University Affiliated: Yes

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.