Savchenko 2009 Swift暴的死线去哪里了?

主要内容:
其实HETE的也几乎没有(Barraud et al. 2003)

精彩摘抄:

死线是在同步模型下, 低能段的谱指数 f_nu~ nu^alpha, 应该是1/3, 如果掺上了-1/2或者-(p-1)/2的高能段, 则可能在观测上小于1/3(如果谱指数比1/3大, 则在同步谱上不可能, 如果不考虑同步自吸收导致的谱指数为2的贡献的话). 换成光子谱指数就是小于-2/3, 在上图上就是大于2/3(因为他把指数的负号去掉了). 其中蓝线是batse的, 红线是swift的. 可见在2/3的附近, swift的暴很少.

虽然死线可以用黑体成份来解释. 但是如果看到这个图, 则很可能说明但是BATSE的谱测量不够精确才导致这些死线的出现的.

图中在纵坐标上, 谱的个数居然也有error bar, 搞不懂.

文章信息:

arXiv:0903.3556 [ps, pdf, other]

Title: Where are Swift Gamma-ray bursts beyond the "synchrotron deathline"?

Authors: V.Savchenko, A.Neronov

Comments: 11 pages, 20 figures, accepted for publication in MNRAS

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We study time-resolved spectra of the prompt emission of Swift Gamma-ray bursts (GRB). Our goal is to see if previous BATSE claims of the existence of a large amount of spectra with the low energy photon indices harder than 2/3 are consistent with Swift data. We perform a systematic search of the episodes of the spectral hardening down to the photon indices below 2/3 in the prompt emission spectra of Swift GRBs. We show that the data of the BAT instrument on board of Swift are consistent with BATSE data, if one takes into account differences between the two instruments. Much lower statistics of the very hard spectra in Swift GRBs is explained by the smaller field of view and narrower energy band of the BAT telescope.