论文标题
I型X射线爆发的光谱和来自环礁和瞬态源4U 1730 $ -22的燃料组成
Type I X-ray bursts' spectra and fuel composition from the atoll and transient source 4U 1730$-$22
论文作者
论文摘要
Nicer观察到来自中子星低质量X射线二进制4U〜1730 $ - $ 22的两次爆发在2021年和2022年，在硬度强度图中显示出相似的光谱演化。在两个爆发中都确定了17种I类X射线爆发。 X射线爆发光谱显示出与黑体模型的明显偏差，首先是$ \ sim10 $ s。由于poynting-Robertson的阻力或积聚磁盘的反射，增加了增强的持续排放，都显着改善了拟合结果。我们发现17个X射线爆发中有12个显示了光球半径的扩展（PRE）特征。考虑到Insight-HXMT观察到的十张X射线爆发中的9次爆发，从4U〜1730--22中展示了78％的爆发。根据爆发时间的上升时间，持续时间，局部积聚速率以及从复发时间估计的爆发燃料组成，我们建议这些前突发是由纯氦驱动的。从预爆发的触地得分通量中，我们估计$ d = 7.54 \ pm {0.46}（x = 0）$ kpc的$ kpc，用于$ m _ {\ rm ns} = 1.4m_ \ odot $和$ r _ {\ odot $和$ r _ {\ rm ns} {\ rm ns} = \ rm ns} = 10〜10〜10〜MM}
NICER observed two outbursts from the neutron star low-mass X-ray binary 4U~1730$-$22 in 2021 and 2022, which showed a similar spectral evolution in the hardness-intensity diagram. Seventeen type I X-ray bursts were identified in both outbursts. The X-ray burst spectra showed clear deviations from the blackbody model, firstly $\sim10$ s after onset. Adding the enhanced persistent emission due to the Poynting-Robertson drag or the reflection from the accretion disk both significantly improved the fitting results. We found that 12 out of 17 X-ray bursts showed the photospheric radius expansion (PRE) characteristic. Considering the nine PRE bursts out of ten X-ray bursts observed by Insight-HXMT, 78\% of bursts from 4U~1730--22 exhibited PRE. According to the burst rise time, the duration, the local accretion rate, and the burst fuel composition estimated from recurrence time, we propose that these PRE bursts were powered by pure helium. From the touchdown flux of PRE bursts, we estimate the source distance of $ d=7.54\pm{0.46} (X=0)$ kpc for a canonical neutron star with $M_{\rm NS}=1.4M_\odot$ and $R_{\rm NS}=10~{\rm km}$.
