论文标题
4U 1730-22的热核X射线爆发
The thermonuclear X-ray bursts of 4U 1730-22
论文作者
论文摘要
我们介绍了使用中子星内部组成探索器（NICER）观察到的历史瞬态4U 1730-22的观察结果。自1972年发现以来一直保持静止后，这款X射线二进制于2021年和2022年出现了爆发活性。我们以更好的方式观察到4U 1730-22，总共检测到17个热核X射线爆发。从光谱分析中，我们发现这些X射线爆发可以分为一组明亮和弱的爆发。所有明亮的爆发均显示$ 1 \ sim2 $第二次上升时间和光球半径膨胀阶段，而弱爆发显示出较慢的$ \ sim5 $ second上升，并且倾向于凹形。从光球半径扩展通量中，我们估计源距离为$ 6.9 \ pm0.2 $ kpc。我们考虑对我们的观察结果进行各种解释，并建议如果材料在恒星赤道处稳定燃烧，可能会解释它们，并且不稳定的点火发生在一系列较高的纬度范围内。
We present observations of the historic transient 4U 1730-22 as observed with the Neutron Star Interior Composition Explorer (NICER). After remaining in quiescence since its 1972 discovery, this X-ray binary showed renewed outburst activity in 2021 and 2022. We observed 4U 1730-22 extensively with NICER, detecting a total of 17 thermonuclear X-ray bursts. From a spectroscopic analysis, we find that these X-ray bursts can be divided into a group of bright and weak bursts. All bright bursts showed $1\sim2$ second rise times and a photospheric radius expansion phase, while the weak bursts showed a slower $\sim5$ second rise with a tendency for concave shapes. From the photospheric radius expansion flux, we estimate the source distance at $6.9\pm0.2$ kpc. We consider various interpretations for our observations and suggest that they may be explained if accreted material is burning stably at the stellar equator, and unstable ignition occurs at a range of higher latitudes.
