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arXiv · 0808.0889

VERITAS Discovery of >200GeV Gamma-ray Emission from the Intermediate-frequency-peaked BL Lac Object W Comae

VERITAS Collaboration·V. A. Acciari·E. Aliu·M. Beilicke·W. Benbow·M. Boettcher·S. M. Bradbury·J. H. Buckley·V. Bugaev·Y. Butt·O. Celik·A. Cesarini·L. Ciupik·Y. C. K. Chow·P. Cogan·P. Colin·W. Cui·M. K. Daniel·T. Ergin·A. D. Falcone·S. J. Fegan·J. P. Finley·G. Finnegan·P. Fortin·L. F. Fortson·A. Furniss·D. Gall·G. H. Gillanders·J. Grube·R. Guenette·G. Gyuk·D. Hanna·E. Hays·J. Holder·D. Horan·C. M. Hui·T. B. Humensky·A. Imran·P. Kaaret·N. Karlsson·M. Kertzman·D. B. Kieda·A. Konopelko·H. Krawczynski·F. Krennrich·M. J. Lang·S. LeBohec·K. Lee·G. Maier·A. McCann·M. McCutcheon·P. Moriarty·R. Mukherjee·T. Nagai·J. Niemiec·R. A. Ong·D. Pandel·J. S. Perkins·D. Petry·M. Pohl·J. Quinn·K. Ragan·L. C. Reyes·P. T. Reynolds·E. Roache·H. J. Rose·M. Schroedter·G. H. Sembroski·A. W. Smith·D. Steele·S. P. Swordy·J. A. Toner·V. V. Vassiliev·R. Wagner·S. P. Wakely·J. E. Ward·T. C. Weekes·A. Weinstein·R. J. White·D. A. Williams·S. A. Wissel·M. Wood·B. Zitzer
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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 January and April 2008. A strong outburst of gamma-ray emission was measured in the middle of March, lasting for only four 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 200GeV 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, with the latter offering a more natural set of parameters to fit the data.

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VERITAS Collaboration, V. A. Acciari, E. Aliu, M. Beilicke, W. Benbow, M. Boettcher, S. M. Bradbury, J. H. Buckley, V. Bugaev, Y. Butt, O. Celik, A. Cesarini, L. Ciupik, Y. C. K. Chow, P. Cogan, P. Colin, W. Cui, M. K. Daniel, T. Ergin, A. D. Falcone, S. J. Fegan, J. P. Finley, G. Finnegan, P. Fortin, L. F. Fortson, A. Furniss, D. Gall, G. H. Gillanders, J. Grube, R. Guenette, G. Gyuk, D. Hanna, E. Hays, J. Holder, D. Horan, C. M. Hui, T. B. Humensky, A. Imran, P. Kaaret, N. Karlsson, M. Kertzman, D. B. Kieda, A. Konopelko, H. Krawczynski, F. Krennrich, M. J. Lang, S. LeBohec, K. Lee, G. Maier, A. McCann, M. McCutcheon, P. Moriarty, R. Mukherjee, T. Nagai, J. Niemiec, R. A. Ong, D. Pandel, J. S. Perkins, D. Petry, M. Pohl, J. Quinn, K. Ragan, L. C. Reyes, P. T. Reynolds, E. Roache, H. J. Rose, M. Schroedter, G. H. Sembroski, A. W. Smith, D. Steele, S. P. Swordy, J. A. Toner, V. V. Vassiliev, R. Wagner, S. P. Wakely, J. E. Ward, T. C. Weekes, A. Weinstein, R. J. White, D. A. Williams, S. A. Wissel, M. Wood, B. Zitzer. 2008-08-06. VERITAS Discovery of >200GeV Gamma-ray Emission from the Intermediate-frequency-peaked BL Lac Object W Comae. https://doi.org/10.1086/592244

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