高能天体物理研究组知识库

I型X射线暴（热核暴）是发生在小质量X射线中子星双星系统中X射线波段流量突然大幅度增加的一种高能现象。在热核闪模型下,此现象被认为主要由中子星表面热核不稳定燃烧主要引起的。典型X射线暴的光变曲线呈现快速上升（1～5 s）、幂指数下降（10～100 s）的单峰结构。随着X射线暴样本的增加,在观测上出现了一类多峰结构的热核暴。在现有的115个暴源中,至少6个暴源有此类多峰结构暴。通过研究多峰暴的观测性质,发现多峰暴只出现在极少数不同类型不同吸积状态的暴源中,其中大部分多峰暴的峰值流量小于爱丁顿极限,除少数多峰暴呈三峰结构以外,大部分多峰暴是双峰结构,并且双峰暴的两峰值相对强弱没有固定规律,暴频振荡在多峰暴当中的出现也无明显规律性。针对这些观测现象,总结了关于多峰暴的多个理论解释。

Type-I (thermonuclear) X-ray bursts show a phenomenon of sudden increase in X-ray intensity, usually occurring in Low-Mass X-ray Binaries (LMXBs). Type-I Xray bursts are considered as unstable ignition of accreted fuel on the surface of an accreting neutron star in the thermonuclear flash model. In a typical X-ray burst, the light curve shows a single-peaked profile with a fast rise and an exponential decay (FRED). With increasing detections of X-ray bursts, some unusual multi-peaked bursts appear. To date, the number of burster increases to 115, but only six sources have been reported with multi-peaked bursts. We find that multi-peaked bursts only appear in a few sources at different accretion rate. The peak flux in most of the multi-peaked bursts is lower than Eddington flux. Except the very rare triple-peaked bursts, most of the multi-peaked bursts are double-peaked bursts, and there is no regularity between the peaks’intensity in each double-peaked burst. The burst oscillation phenomenon has also no obvious regularity in double-peaked X-ray bursts. Finally, we summarize the theoretical models of multi-peaked bursts.