We present the results of a search for the nature of ultraluminous X-ray source (ULX) X-3 in the nearby galaxy NGC 4258. We use archival data from {\it XMM-Newton}, {\it Chandra}, {\it NuSTAR} and {\it HST} observations. Total X-ray data analysed to find the model parameters of the system is indicative of a stellar mass black hole, $\sim$ 10 M$_{\sun}$, as the central compact object. Furthermore, analyses of the optical data from {\it HST} reveal two optical candidates with the 90 per cent confidence level of error radius of 0$\farcs$28. Assuming the optical emission is dominated by the donor star, both of these candidates are found to have spectral types that lie between B3$-$F1 with absolute magnitudes of $M_{\rm V}$ $\approx$ -6.4. Moreover, the age and mass estimates for the candidates are found to be of 10 and 18 Myr and of 13 and 20 M$_{\sun}$, respectively.

中文翻译：

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NGC 4258 中的 ULX Source X-3：探索其 X 射线和光学特性

我们展示了在附近星系 NGC 4258 中搜索超亮 X 射线源 (ULX) X-3 的性质的结果。我们使用来自 {\it XMM-Newton}、{\it Chandra}、{\它 NuSTAR} 和 {\it HST} 观察。为寻找系统模型参数而分析的总 X 射线数据表明，一个恒星质量黑洞 $\sim$ 10 M$_{\sun}$ 作为中心致密天体。此外，对来自 {\it HST} 的光学数据的分析揭示了两个光学候选者，其误差半径的 90% 置信水平为 0$\farcs$28。假设光发射由供体星主导，发现这两个候选星的光谱类型都在 B3$-$F1 之间，绝对星等为 $M_{\rm V}$ $\approx$ -6.4。而且，