Broadband X-Ray Spectra of Short Bursts from SGR 1900+14
Broadband X-Ray Spectra of Short Bursts from SGR 1900+14
复制标题
SGR 1900 短爆发的宽带 X 射线光谱 14
DOI：
10.1086/422405
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
P. Woods
中科院分区：
文献类型：
--
作者：
M. Feroci;G. A. Caliandro;E. Massaro;S. Mereghetti;P. Woods
本文报道了在2001年4月18日中期耀斑之后的几个小时内，用BeppoSAX上的窄场仪器观测到的来自SGR1900+14年的10个短爆发的X射线能谱特征。爆发持续时间通常小于1 S，并且常常在短到10ms的时间尺度上显示出显著的时间结构。MECS和PDS仪器的爆发谱在1.5到100keV以上的能量范围内进行了拟合。我们拟合了几个光谱模型，并假设NH值小于5×1022厘米-2，这是从持续发射中的观测得出的。我们的结果表明，广泛使用的光学薄热韧致辐射定律对高于15keV的能量提供了可以接受的光谱拟合，但在较低能量时严重高估了通量。几年前，在SGR 1806-20的短爆发中也观察到了类似的行为，这表明在低能量下光谱的翻滚是这类源的普遍特性。另一种光谱模型，如两个黑体或截止幂定律，对宽带光谱数据提供了明显更好的拟合，并表明所有10个爆发的光谱形状都一致。
We report on the X-ray spectral properties of 10 short bursts from SGR 1900+14 observed with the narrow-field instruments on board BeppoSAX in the hours following the intermediate flare of 2001 April 18. Burst durations are typically shorter than 1 s and often show significant temporal structure on timescales as short as ~10 ms. Burst spectra from the MECS and PDS instruments were fitted across an energy range from 1.5 to above 100 keV. We fitted several spectral models and assumed NH values smaller than 5 × 1022 cm-2, as derived from observations in the persistent emission. Our results show that the widely used optically thin thermal bremsstrahlung law provides acceptable spectral fits for energies higher than 15 keV but severely overestimates the flux at lower energies. Several years ago similar behavior was observed in short bursts from SGR 1806-20, suggesting that the rollover of the spectrum at low energies is a universal property of this class of sources. Alternative spectral models, such as two blackbodies or a cutoff power law, provide significantly better fits to the broadband spectral data and show that all 10 bursts have spectra consistent with the same spectral shape.