| BL Lacertae： Hard Optical Spectrum and GeV γ-ray Emission |
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| 引用本文： | Shan-Jie Qian,Xi-Zhen Zhang,T P Krichbaum National Astronomical Observatories,Chinese Academy of Sciences Beijing Max-Planck-Institut für Radioastronomie Auf dem Hügel Bonn Germany.BL Lacertae： Hard Optical Spectrum and GeV γ-ray Emission[J].中国天文和天体物理学报,2004,4(3):231-246. |
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| 作者姓名： | Shan-Jie Qian Xi-Zhen Zhang T P Krichbaum National Astronomical Observatories Chinese Academy of Sciences Beijing Max-Planck-Institut für Radioastronomie Auf dem Hügel Bonn Germany |
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| 作者单位： | Shan-Jie Qian;Xi-Zhen Zhang;T P Krichbaum National Astronomical Observatories，Chinese Academy of Sciences Beijing 100012 Max-Planck-Institut für Radioastronomie Auf dem Hügel 69 53121 Bonn Germany |
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| 摘 要： | The spectral energy distribution (SED) of the γ-ray flare observed in July 1997 in BL Lacertae is re-considered. It is pointed out that the optical observations made by Webb et al. showed the associated optical flare has a hard spectrum (the average spectral index αopt～0.48, Fν∝ν^-α), and the ASCA observations made by Tanihata et al. showed very steep spectra in the soft X-ray band (0.7-1.5 keV) (αx～3-4). We find that the flux densities and spectral indices in both the optical and soft X-ray bands are closely consistent with a ‘canonical‘ synchrotron spectrum emitted by relativistic electrons of a power-law energy distribution with a high energy cutoff, and thus the peak of the SED of the synchrotron radiation (in representation of νFν) is located in the EUV - soft X-ray bands. Therefore, the GeV γ-ray emission observed in the July 1997 outburst may be mainly due to the synchrotron self-Compton (SSC) process, contrasting with the current explanations in terms of external radiation Compton (ERC) process, in which the seed photons are mostly taken to be the UV emission from the clouds of the broad emission line region. We argue that the hard optical spectra observed during the γ-ray outburst may be an important signature for the acceleration of high energy electrons (γe-10^4) in the γ-ray emitting region.
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| 关 键 词： | 光谱能量 γ射线 X射线 光学 |
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