Title: An e-MERLIN & EVN radio counterpart to the ultraluminous X-ray source M82 X-1 Show Chinese title

Title: 一个超亮X射线源M82 X-1的e-MERLIN & EVN射电对应体

Abstract: Ultra-luminous X-ray sources (ULXs) are X-ray bright (L$_{\rm X-ray} >$3$\times$10$^{39}$erg s$^{-1}$) extra-galactic objects that are powered by either neutron stars, or stellar or intermediate-mass black holes (IMBHs) but few have been detected in the radio waveband. In the nearby galaxy M82, the brightest ULX - M82 X$-$1, is thought to be associated with an IMBH but to date does not have a radio counterpart. We present deep wide-band reprocessed e-MERLIN images observed in 2015 May with an r.m.s. sensitivity of 7$\mu$Jy beam$^{-1}$ and report the discovery of a new radio source with an integrated flux of S$_{\rm \nu=4.88\,GHz}$ = 174$\pm$15$\mu$Jy, which is spatially co-incident with the Chandra X-ray position of M82 X$-$1. This source is not detected in archival MERLIN/e-MERLIN observations in the last three decades. A search for intra-observation variability in the 2015 e-MERLIN data was inconclusive, but a comparison with 1.5 GHz e-MERLIN observations taken a week prior yielded no detection. We also detect the source at the same position with milliarcsecond angular resolution in EVN+e-MERLIN data from 2021 March at 53$\pm$10$\mu$Jy. The radio source position is ICRF J2000 RA: 09$^{h}$55$^{m}$50.1172$^{s}$, Dec: +69$^{\circ}$40'46.606" ($\pm$1.5 mas). These radio fluxes are consistent with other radio-detected ULXs on the radio:X-ray plane and points towards a stellar/intermediate-mass black hole. The black hole mass inferred by the `fundamental plane of black hole activity' is 2650 M$_{\odot}$, but this value remains highly uncertain. Show Chinese abstract

Abstract: 超亮X射线源（ULX）是额外银晕星系中的X射线明亮（L$_{\rm X-ray} >$3$\times$10$^{39}$erg s$^{-1}$）的天体，它们的能量来源可能是中子星，或者恒星级质量黑洞和中间质量黑洞（IMBH），但在无线电波段很少被探测到。在附近星系M82中，最亮的ULX——M82 X$-$1，被认为与一个IMBH相关联，但迄今为止没有无线电对应体。我们展示了2015年5月使用e-MERLIN观测到的深度宽波段重新处理图像，其噪声水平为rms。 灵敏度为 7$\mu$Jybeam$^{-1}$，报告发现了一个新的射电源，积分流量为 S$_{\rm \nu=4.88\,GHz}$ = 174$\pm$15$\mu$Jy，该位置与 M82 在 Chandra X 射线观测中的位置一致 X$-$1。 这个源在过去三十年的档案 MERLIN/e-MERLIN 观测中未被探测到。 对 2015 年 e-MERLIN 数据中观测内的变异性搜索结果不确定，但与一周前拍摄的 1.5 GHz e-MERLIN 观测数据对比没有检测到信号。 我们还利用2021年3月的EVN+e-MERLIN数据以毫角秒的角分辨率在同一位置探测到来源，其流量密度为53$\pm$10$\mu$Jy。 该射电源的位置为ICRF J2000赤经：09$^{h}$55$^{m}$50.1172$^{s}$，赤纬：+69$^{\circ}$40'46.606" ($\pm$1.5 mas)。 这些射电通量与其他无线电探测到的超亮X射线源在射电- X射线平面上一致，并指向一个恒星级/中等质量黑洞。 由“黑洞活动的基本平面”推断出的黑洞质量为 2650 M$_{\odot}$，但此值仍极不确定。