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arXiv 1005.3302astro-ph.HE
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短重现期热核爆发的多仪器X射线观测

Multi-Instrument X-ray Observations of Thermonuclear Bursts with Short Recurrence Times

L. Keek, D. K. Galloway, J. J. M. in 't Zand, A. Heger

摘要:

来自低质量X射线双星的I型X射线爆发是由在中子星上的物质中的热核逃逸引起的。虽然典型的复发时间是几个小时,与理论点火模型预测一致,但也有观测到在前一次事件发生后10分钟或更短的时间内发生爆炸。我们提出了一个全面的评估,这一现象使用的目录3387爆发观察BeppoSAX/WFC和RXTE/PCA X射线仪器。该目录包含136个重现时间小于1小时的爆发,这些爆发来自15个来源,最多可达4个事件的倍数。从所谓的超致密双星中没有观察到短的重现时间,这表明氢燃烧过程起着至关重要的作用。至于中子星的自旋频率是已知的,这些来源都在500赫兹以上的快速旋转,旋转诱导混合可以解释突发复发时间的顺序为10分钟。短复发时间的突发一般发生在所有的质量吸积率,正常的突发观察,但对于个别来源的短复发时间可能会被限制在一个较小的间隔吸积率。这种爆发的比例约为30%。我们还报告了已知的最短复发时间为3.8分钟。

英文摘要:

Type I X-ray bursts from low-mass X-ray binaries result from a thermonuclear runaway in the material accreted onto the neutron star. Although typical recurrence times are a few hours, consistent with theoretical ignition model predictions, there are also observations of bursts occurring as promptly as ten minutes or less after the previous event. We present a comprehensive assessment of this phenomenon using a catalog of 3387 bursts observed with the BeppoSAX/WFCs and RXTE/PCA X-ray instruments. This catalog contains 136 bursts with recurrence times of less than one hour, that come in multiples of up to four events, from 15 sources. Short recurrence times are not observed from so-called ultra-compact binaries, indicating that hydrogen burning processes play a crucial role. As far as the neutron star spin frequency is known, these sources all spin fast at over 500 Hz; the rotationally induced mixing may explain burst recurrence times of the order of 10 min. Short recurrence time bursts generally occur at all mass accretion rates where normal bursts are observed, but for individual sources the short recurrence times may be restricted to a smaller interval of accretion rate. The fraction of such bursts is roughly 30%. We also report the shortest known recurrence time of 3.8 minutes.

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