| A synchrotron self-Compton scenario for the very high energy γ-ray emission of the intermediate BL Lacertae object W Comae |
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| 基金项目： | Supported by the National Natural Science Foundation of China.Acknowledgements I appreciate the valuable suggestions of the referee. 1 thank Jinming Bai, Liang Chen and Hongtao Liu for their helpful discussions. This work is supported by the National Natural Science Foundation of China under grants 10533050 and the National Basic Research Program （＂973＂ Program） of China under Grant 2009CB824800. |
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| 摘 要： | W Comae has significant variability in multi-wavelengthes, from radio to gamma-ray bands. A bright outburst in optical and X-ray bands was observed in 1998, and most recently, a strong TeV flare was detected by VERITAS in 2008. It is the first TeV intermediate-frequency-peaked BL Lacertae source. I find that both the broadband spectral energy distributions （SEDs） which were quasi-simultaneously obtained during the TeV flare and during the optical/X-ray outburst are well fit by using a single-zone synchrotron ＋ synchrotron-self-Compton model. The satisfactory fitting requires a large beaming factor, i.e., δ- 25 and δ- 20 for the TeV flare and the optical/X-ray outburst, respectively, suggesting that both the optical/X-ray outburst and the TeV flare are from a relativistic jet. The size of the emission region of the TeV flare is three times larger than that of the optical/X-ray outburst, and the strength of the magnetic field for the TeV flare is - 14 times smaller than that of the X-ray/optical outburst, likely indicating that the region of the TeV flare is more distant from the core than that of the X-ray/optical outburst. The inverse Compton component of the TeV flare peaks around 1.3 GeV, but it is around 20 MeV for the X-ray/optical outburst, lower than that for the TeV flare by two orders of magnitude. The model predicts that the optical/X-ray outburst might be accompanied by a strong MeV/GeV emission, but the TeV flare may be not associated with the X-ray/optical outburst. The GeV emission is critical for characterizing the SEDs of the optical/X-ray outburst and the TeV flare. The predicted GeV flux is above the sensitivity of Fermi/LAT, and it could be verified with the observations by Fermi/LAT in the near future.
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| 关 键 词： | 同步加速器 γ射线 变异性 光谱 |
A synchrotron self-Compton scenario for the very high energy γ-ray emission of the intermediate BL Lacertae object W Comae |
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| Authors: | Jin Zhang |
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| Institution: | [1]National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, Kunming 650011, China [2]College of Physics and ElectronicEngineering, Guangxi Teachers Education University, Nanning 530001, China [3]Graduate University of Chinese Academy of Sciences, Beijing 100049, China |
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| Abstract: | BL Lacertae objects： individual： W Comae - gamma-rays observations - gamma-rays theory - radiation mechanisms non-thermal |
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| Keywords: | BL Lacertae objects： individual： W Comae - gamma-rays observations - gamma-rays theory - radiation mechanisms non-thermal |
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