I型X射线暴系统UW CrB的光学光谱与测光分析
Analysis of optical spectroscopy and photometry of the type I X-ray bursting system UW CrB
AI总结：
本文通过两年光学测光与光谱观测研究UW CrB，更新轨道星历与周期，发现17个新光学暴，并修正再处理位点交食认识、解释P-Cygni轮廓成因。
摘要：
UW Coronae Borealis（UW CrB）是一个低质量X射线双星，同时表现出I型X射线暴和光学暴，这些暴通常持续20秒。该系统的双星周期接近2小时，并且由于光学光变曲线中存在交食，被认为具有相对较高的倾角。还有证据表明，系统中存在一个非对称吸积盘；根据交食深度的变化，该盘每5.5天进动一次。本文给出了历时2年获得的UW CrB光学测光和光谱观测。我们利用观测到的光学交食更新了轨道星历，并将轨道周期精化为110.97680(1)分钟。文中共给出17个新的光学暴，其中10个在时间上得到分辨。这些暴的平均e折时间为19±3秒，与此前发现的值一致。光学暴在先前识别出的、以φ=0.967为中心的轨道相位间隙中被观测到，这意味着再处理位点并不像此前认为的那样被交食。最后，我们发现光学光谱中某些原子线内看似存在的P-Cygni轮廓是由瞬态吸收造成的。
英文摘要：
UW Coronae Borealis (UW CrB) is a low mass X-ray binary that shows both Type 1 X-ray and optical bursts, which typically last for 20 s. The system has a binary period of close to 2 hours and is thought to have a relatively high inclination due to the presence of an eclipse in the optical light curve. There is also evidence that an asymmetric disc is present in the system, which precesses every 5.5 days based on changes in the depth of the eclipse. In this paper, we present optical photometry and spectroscopy of UW CrB taken over 2 years. We update the orbital ephemeris using observed optical eclipses and refine the orbital period to 110.97680(1) min. A total of 17 new optical bursts are presented, with 10 of these bursts being resolved temporally. The average $e$-folding time of $19\pm3$s for the bursts is consistent with the previously found value. Optical bursts are observed during a previously identified gap in orbital phase centred on $ϕ=0.967$, meaning the reprocessing site is not eclipsed as previously thought. Finally, we find that the apparent P-Cygni profiles present in some of the atomic lines in the optical spectra are due to transient absorption.
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