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arXiv 0803.1821astro-ph
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用INTEGRAL观测到的伽玛暴的全球特征和推测的大规模低光度伽玛暴

Global characteristics of GRBs observed with INTEGRAL and the inferred large population of low-luminosity GRBs

S. Foley, S. McGlynn, L. Hanlon, S. McBreen, B. McBreen

摘要:

INTEGRAL拥有两台灵敏的伽马射线仪器,截至2007年7月已探测到46次伽马射线暴。我们提出的光谱,空间和时间的属性的爆发的INTEGRAL伽玛射线暴目录使用的数据从成像仪,IBIS,光谱仪,SPI。用幂律、能带模型和准热模型计算了伽玛暴的光谱特性。光谱滞后,即低能量伽马射线相对于高能量伽马射线到达的时间延迟,测量了31个伽玛暴。用幂律分布拟合的光子指数分布与Swift得到的结果一致。峰值通量分布表明,INTEGRAL比Swift探测到更多的弱伽玛暴,因为它在较小的视场内具有更高的灵敏度。在IBIS的完全编码视场中,大于~0.15 ph cm^-2 s^-1的伽玛暴的全天速率约为1400 yr^-1。在光谱滞后分布中识别出两组,一组具有短滞后<0.75 s(在25-50 keV和50-300 keV之间),另一组具有长滞后>0.75 s。大多数的长滞后伽玛暴被推断有低的红移,因为它们的长光谱滞后,它们的倾向有低的峰值能量和微弱的光学和X射线余辉。它们主要是在超银道面方向观测到的,四极矩Q=-0.225+/-0.090,因此反映了宇宙的局部大尺度结构。低光度的长滞后伽玛暴在Ib/c型超新星中的比例约为25%。其中一些爆发可能是由没有超新星的大质量恒星的坍缩产生的,或者是由不同的祖先产生的,比如两颗白矮星的合并,或者一颗白矮星与一颗中子星或黑洞的合并,可能是在没有宿主星系的星团环境中。

英文摘要:

INTEGRAL has two sensitive gamma-ray instruments that have detected 46 gamma-ray bursts (GRBs) up to July 2007. We present the spectral, spatial, and temporal properties of the bursts in the INTEGRAL GRB catalogue using data from the imager, IBIS, and spectrometer, SPI. Spectral properties of the GRBs are determined using power-law, Band model and quasithermal model fits to the prompt emission. Spectral lags, i.e. the time delay in the arrival of low-energy gamma-rays with respect to high-energy gamma-rays, are measured for 31 of the GRBs. The photon index distribution of power-law fits to the prompt emission spectra is consistent with that obtained by Swift. The peak flux distribution shows that INTEGRAL detects proportionally more weak GRBs than Swift because of its higher sensitivity in a smaller field of view. The all-sky rate of GRBs above ~0.15 ph cm^-2 s^-1 is ~1400 yr^-1 in the fully coded field of view of IBIS. Two groups are identified in the spectral lag distribution, one with short lags <0.75 s (between 25-50 keV and 50-300 keV) and one with long lags >0.75 s. Most of the long-lag GRBs are inferred to have low redshifts because of their long spectral lags, their tendency to have low peak energies and their faint optical and X-ray afterglows. They are mainly observed in the direction of the supergalactic plane with a quadrupole moment of Q=-0.225+/-0.090 and hence reflect the local large-scale structure of the Universe. The rate of long-lag GRBs with inferred low luminosity is ~25% of Type Ib/c supernovae. Some of these bursts could be produced by the collapse of a massive star without a supernova or by a different progenitor, such as the merger of two white dwarfs or a white dwarf with a neutron star or black hole, possibly in the cluster environment without a host galaxy.

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