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

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

Citation Formats
V. A. Acciari et al. , “VERITAS discovery of > 200 GeV gamma-ray emission from the intermediate-frequency-peaked BL Lacertae object W Comae,” ASTROPHYSICAL JOURNAL LETTERS, vol. 684, no. 2, pp. 0–0, 2008, Accessed: 00, 2020. [Online]. Available: