M31中新发现的一颗暂现超亮X射线源
A Newly Identified Transient Ultraluminous X-ray Source in M31
- California Institute of Technology（加州理工学院）
- University of Illinois at Urbana-Champaign（伊利诺伊大学厄巴纳-香槟分校）
- Université de Strasbourg（斯特拉斯堡大学）
- CNRS（法国国家科学研究中心）
- Observatoire astronomique de Strasbourg（斯特拉斯堡天文台）
- University of Hertfordshire（赫特福德大学）
- University of Southampton（南安普顿大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
该研究报道了M31中新发现的一颗暂现超亮X射线源ULX-3，其峰值光度约10^39 erg/s，光谱演化异常，并估计暂现ULX发生率为0.18±0.10 yr^-1，强调定期X射线监测的重要性。
AI中文摘要：
超亮X射线源（ULXs）是光度超过典型恒星质量致密天体爱丁顿极限的核外X射线源。虽然大多数已知ULX是相对持久的源，但暂现ULX已作为一个独特的群体出现，为极端超爱丁顿吸积提供了独特见解。我们报告了在M31中新发现的一颗暂现ULX的发现及其X射线特征描述。该源于2021年6月9日被偶然首次探测到，其峰值未吸收0.3-10 keV光度达到约10^39 erg s^-1。其光谱演化表明在后期吸积对流增强，这与爆发衰减期间从超爱丁顿细盘向标准薄盘过渡的预期相反。观测到的X射线光变曲线可以用Hameury & Lasota的盘不稳定性模型重现，特征时标约为41-61天。对于1.4太阳质量的中子星，推断的质量吸积率是超爱丁顿的，但对于10太阳质量的恒星质量黑洞则约为爱丁顿光度。与恒星等时线（假设A_V=1.58）比较时，哈勃源目录中的邻近光学源表明可能存在一颗年龄为log10(年龄/年)约8.5、质量约3.2太阳质量的巨恒星伴星。我们估计M31中暂现ULX的发生率为0.18±0.10 yr^-1。该速率低于先前研究中报道的其他星系的速率。M31 ULX-3扩展了M31中已知暂现ULX的小群体，并强调了持续、定期监测邻近星系X射线的重要性。
英文摘要：
Ultraluminous X-ray sources (ULXs) are off-nuclear X-ray sources with luminosities exceeding the Eddington limit of typical stellar-mass compact objects. While most known ULXs are relatively persistent sources, transient ULXs have emerged as a distinct population that offer unique insight into extreme, super-Eddington accretion. We report the discovery and X-ray characterization of a newly identified transient ULX in M31. First detected serendipitously on 2021 June 9, the source reached a peak unabsorbed $0.3 - 10$ keV luminosity of $\sim10^{39}\ \rm erg\ s^{-1}$. Its spectral evolution suggests increasing advection at later epochs, opposite to the expected transition from a super-Eddington slim disk toward a standard thin disk during the decay of the outburst. The observed X-ray light curve can be reproduced using the disk-instability model of Hameury & Lasota, with characteristic timescales of $\sim41-61$ days. The inferred mass-accretion rate is super-Eddington for a $1.4\,M_{\odot}$ neutron star but approximately Eddington for a $10\,M_{\odot}$ stellar-mass black hole. Nearby optical sources from the Hubble Source Catalog suggest a possible giant donor with an age of $\log_{10}({\rm age/yr})\sim8.5$ and a mass of $\sim3.2\,M_{\odot}$, when compared with stellar isochrones with an assumed $A_V=1.58$. We estimate a transient ULX occurrence rate in M31 of $0.18\pm0.10\ {\rm yr^{-1}}$. This rate is lower than those reported for other galaxies in previous studies. M31 ULX-3 expands the small population of known transient ULXs in M31 and highlights the importance of continued, regular X-ray monitoring of nearby galaxies.
