标题： 赛弗特星系 NGC 5252 中的核外非恒星黑洞 显示英文标题

标题： An Off-Nucleus Nonstellar Black Hole in the Seyfert Galaxy NGC 5252

摘要： 我们报告了在NGC 5252中发现的一个超亮X射线源（ULX；CXO J133815.6+043255）。这个ULX是一个非核点源，距离NGC 5252的中心22$^{\prime\prime}$远，X射线光度为1.5$\times$ $10^{40}$ erg s$^{-1}$。它是少数几个在无线电、光学、紫外波段有明显对应体的ULX之一。对该ULX的后续光学光谱显示有强发射线。[O III]发射线的红移与NGC 5252的系统速度一致，表明ULX与NGC 5252有引力束缚关系。[O III]的流量似乎与普通活动星系核（AGN）的X射线和射电光度以相同的方式相关，这表明[O III]发射本质上与ULX相关联。基于多波段数据，我们认为该ULX不太可能是背景AGN。更可能的情况是一个吸积黑洞，其黑洞质量为$\geq 10^4M_\odot$，可能是合并矮星系的剥离残骸。 显示英文摘要

摘要： We report the discovery of a ultraluminous X-ray source (ULX; CXO J133815.6+043255) in NGC 5252. This ULX is an off-nuclear point-source, which is 22$^{\prime\prime}$ away from the center of NGC 5252, and has an X-ray luminosity of 1.5 $\times$ $10^{40}$erg s$^{-1}$. It is one of the rare examples of ULX, which exhibits clear counterparts in radio, optical, UV bands. Follow-up optical spectrum of the ULX shows strong emission lines. The redshift of [O III] emission line coincides with the systematic velocity of NGC 5252, suggesting the ULX is gravitationally bound to NGC 5252. The flux of [O III] appears to be correlated with both X-ray and radio luminosity in the same manner as ordinary AGNs, indicating that the [O III] emission is intrinsically associated with the ULX. Based on the multiwavelength data, we argue that the ULX is unlikely to be a background AGN. A more likely option is an accreting BH with a black hole mass of $\geq 10^4M_\odot$, which might be a stripped remnant of a merging dwarf galaxy.