Emission mechanism and source distances of γ-ray bursts
Emission mechanism and source distances of γ-ray bursts
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作者：
E. Liang
已报道的大多数∼射线暴的连续谱(γ20kev-2 MeV)类似于简单的指数1-4。因此，传统的观点认为它们是热等离子体(KT≳100keV除外，特别是1979年3月5日事件)的光学薄的自由(Bremstralung)发射。我在这里指出：(1)与源距离无关，如果源确实是磁场为B≳1012G的中子星，则自由-自由解释存在固有的困难，因为这些热热电子的同步发射率将大大超过自由发射率，对于任何与观测所要求的τES≪1一致的合理电子密度；(2)光谱数据可以同样好地拟合，如果不是更好的话，可以用中等相对论(KT∼MC2)电子的光学薄热同步谱来拟合；(3)由于同步加速器自吸收(或高能康普顿失真)而没有可观测到的低能量周转，这给光度和距离的来源带来了有趣的上限。大多数源是非宇宙学的(<；10kpc-1mpc)，但不一定像一些作者建议的使用自由-自由光谱解释的那样接近(例如，参见参考文献)。2)。
The reported continuum spectra (∼20 keV–2 MeV) of mostγ-ray bursts resemble a simple exponential1–4. Hence, the conventional view is that they are the optically thin free–free (bremstralung) emission of a hot thermal plasma (kT≳ 100 keV with the exception of a few soft events, notably the 5 March 1979 event). I show here that: (1) independent of the source distance, there is an inherent difficulty with the free–free interpretation if the sources are indeed neutron stars with magnetic field B ≳ 1012G, because the synchrotron emissivity of these hot thermal electrons would greatly exceed then free–free emissivity for any reasonable electron density consistent withτes≪ 1 required by observations; (2) the spectral data can be fitted equally well, if not better, by optically thin thermal synchrotron spectra of mildly relativistic (kT∼mc2) electrons; (3) the absence of observable low-energy turnover due to synchrotron self-absorption (or high energy Compton distortion) puts interesting upper limits to the source of luminosity and distance. Most sources are noncosmological (<10 kpc–1 Mpc) but not necessarily as nearby as some authors have suggested using the free–free spectral interpretation (see, for example, ref. 2).