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arXiv 1901.00239astro-ph.HEastro-ph.SR
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低质量X射线双星瞬变过程中爆发率与轨道周期的关系

The relation between outburst rate and orbital period in low-mass X-ray binary transients

Jie Lin, Zhen Yan, Zhanwen Han, Wenfei Yu

摘要:

在对近几十年来观测到的低质量X射线双星瞬变爆发进行全面研究的基础上,研究了低质量X射线双星瞬变爆发的性质。根据Swift/BAT、RXTE/ASM和MAXI的X射线监测数据以及文献中的既往报告估计爆发率。我们发现,几乎所有的LMXBT的轨道周期低于$\sim$ 12小时,只有一个爆发,在这些观测。长周期($P_{\rm orb} \gtrsim$ 12小时)和短周期($P_{\rm orb} \lesssim$ 12小时)系统的爆发率存在系统差异。我们推断,传质速率是负责系统的差异,因为磁盘不稳定性模型(DIM)的建议,传质速率是影响静止时间的关键因素。长周期和短周期LMXBTs之间爆发速率的差异可能是由于供体在不同演化阶段的传质机制不同。根据单星演化轨迹,推导了含有不同金属丰度亚巨星施主的X射线双星的临界轨道周期。临界轨道周期($P_{\rm orb,crit}=$ 12.4小时)与上述根据爆发率统计得到的轨道周期边界一致。此外,我们还发现,在施主星的光度类别为III/IV的样本中,爆发率与轨道周期之间存在负相关。黑洞子样本的最佳拟合幂律指数与那些施主恒星从主序星演化出来的系统的理论预测大致一致。

英文摘要:

We have investigated the outburst properties of low-mass X-ray binary transients (LMXBTs) based on a comprehensive study of the outbursts observed in the past few decades. The outburst rates were estimated based on the X-ray monitoring data from Swift/BAT, RXTE/ASM and MAXI, and previous reports in the literature. We found that almost all LMXBTs with the orbital period below $\sim$12 hr showed only one outburst in these observations. There are systematic difference in the outburst rate between long-period ($P_{\rm orb} \gtrsim$ 12 hr) and short-period ($P_{\rm orb} \lesssim$ 12 hr) systems. We infer that mass transfer rate is responsible for the systematic difference, since the disk instability model (DIM) suggested that the mass transfer rate is a key factor affecting the quiescence time. The difference in outburst rate between long-period and short-period LMXBTs is probably due to the different mass transfer mechanism at different evolutionary stages of the donors. Based on the evolutionary tracks of single stars, we derived the critical orbital period for X-ray binaries that harbor a subgiant donor in various metallicity. The critical orbital period ($P_{\rm orb,crit}=$12.4 hr) is consistent with the above orbital period boundary obtained from the statistics of outburst rates. Furthermore, we found a negative correlation between the outburst rate and the orbital period in the samples for which the luminosity class of the donor star is III/IV. The best-fitting power-law index for the black hole subsamples is roughly consistent with the theoretical prediction for those systems with a donor star evolved off the main sequence.

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