论文标题
NGC 5474 X-1：旧恒星群中的中子星ULX？
NGC 5474 X-1: a neutron star ULX in an old stellar cluster?
论文作者
论文摘要
我们介绍了超X射线源（ULX）NGC 5474 X-1的光学和X射线研究。在源的明亮状态（$ l_x \ sim 2 \ sim 2 \ times10^{40} $ egs/s）中拍摄的X射线频谱显示，在$ \ simeq 8 $ keV处的广泛吸收线的签名，这可能是一种环状共振共振散射功能。这意味着该系统可以容纳带有磁场$ \ sim 10^{12} $ G的中子星。对该区域的第一个观察结果是，在14个月后进行的Hubble Space望远镜（HST）表明，光源在光学范围内也很明亮。随后的观察结果表明，源的两个范围都消失了（U乐队中的$ 2.8^m $超过$ 2.8^m $，在X射线中以50-100的倍数），并且再也不会变得光明。更深入的HST观察结果使得对供体星光谱级和质量（$ <\，7 $ m $ _ \ odot $）施加约束，并确定一个大约1 Gyr的出色群，其中心位于NGC 5474 x-1的投影距离为$ \ simeq 2 $ PC。 ULX可以是这个旧群集的成员，但是，在ULX周围300 pc的售价为$ \ sim10 $ myr的恒星并不能完全排除它只是意外投射的可能性。
We present the optical and X-ray study of the ultraluminous X-ray source (ULX) NGC 5474 X-1. The X-ray spectrum taken during the bright state of the source ($L_X \sim 2\times10^{40}$ egs/s) shows signatures of a broad absorption line at $\simeq 8$ keV which may be a cyclotron resonant scattering feature. This implies that this system may host a neutron star with a magnetic field $\sim 10^{12}$ G. The first observation of this area with the Hubble Space Telescope (HST) carried out 14 months later revealed that the source was bright in the optical range as well. The subsequent observations have shown that the source faded in both ranges (more than $2.8^m$ in the U band and by a factor of 50-100 in X-rays) and has never become bright again. Deeper HST observations made it possible to impose constraints on the donor star spectral class and mass ($<\,7$ M$_\odot$), as well as to identify a stellar cluster of about 1 Gyr, the centre of which is located at a projected distance of $\simeq 2$ pc from NGC 5474 X-1. The ULX can be a member of this old cluster, however, the presence of stars with ages of $\sim10$ Myr within 300 pc around the ULX does not completely exclude the possibility that it is just an accidental projection.
