Evidence for a variable Ultrafast Outflow in the newly discovered Ultraluminous Pulsar NGC 300 ULX-1
Evidence for a variable Ultrafast Outflow in the newly discovered Ultraluminous Pulsar NGC 300 ULX-1
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DOI：
10.1093/mnras/sty1626
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发表时间：
2018-03
影响因子：
4.8
通讯作者：
P. Kosec;Ciro Pinto;D. Walton;A. Fabian;M. Bachetti;M. Brightman;F. Fürst;B. Grefenstette
中科院分区：
文献类型：
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作者：
P. Kosec;Ciro Pinto;D. Walton;A. Fabian;M. Bachetti;M. Brightman;F. Fürst;B. Grefenstette
超光脉冲星明确证明自然界中存在持续的超爱丁顿吸积。他们支持这样一种假设：大多数超亮 X 射线源 (ULX) 是恒星质量的超爱丁顿吸积体，而不是亚爱丁顿中等质量黑洞。超临界吸积理论的一个重要预测是存在以温和相对论速度的中等电离气体的强大流出。在实践中，需要 X 射线光栅（例如 XMM-Newton 上的 RGS）的光谱分辨率来解析 ULX 中的观测特征。使用 RGS，在 3 个 ULX 的光谱中发现了外流（目前已知没有一个是脉冲星）。最近，在 NGC 300 中发现了第四颗超光脉冲星。在此，我们报告在 2016 年 12 月 XMM-Newton 和 NuSTAR 对源的两次同时观测之一期间，在该物体的 X 射线光谱中检测到超快外流 (UFO)，其显着性至少为 3{\sigma}。该外流的预计速度约为 72000 km/s (0.24c) 和高电离度对数值为 3.9 的因子。这是首次同时利用软X射线和硬X射线数据实现对ULX中超快风的探测，也是首次在中子星ULX中探测到UFO。在对该物体的其他观察中，我们没有发现不明飞行物的证据，这可以通过吸收体的块状性质或我们对吸积流的视角的轻微变化来解释。
Ultraluminous pulsars are a definite proof that persistent super-Eddington accretion occurs in nature. They support the scenario according to which most Ultraluminous X-ray Sources (ULXs) are super-Eddington accretors of stellar mass rather than sub-Eddington intermediate mass black holes. An important prediction of theories of supercritical accretion is the existence of powerful outflows of moderately ionized gas at mildly relativistic speeds. In practice, the spectral resolution of X-ray gratings such as RGS onboard XMM-Newton is required to resolve their observational signatures in ULXs. Using RGS, outflows have been discovered in the spectra of 3 ULXs (none of which are currently known to be pulsars). Most recently, the fourth ultraluminous pulsar was discovered in NGC 300. Here we report detection of an ultrafast outflow (UFO) in the X-ray spectrum of the object, with a significance of at least 3{\sigma}, during one of the two simultaneous observations of the source by XMM-Newton and NuSTAR in December 2016. The outflow has a projected velocity of about 72000 km/s (0.24c) and a high ionisation factor with a log value of 3.9. This is the first time a detection of an ultrafast wind in a ULX was achieved using both soft and hard X-ray data simultaneously, and it is also the first detection of a UFO in a neutron star ULX. We find no evidence of the UFO during the other observation of the object, which could be explained by either clumpy nature of the absorber or a slight change in our viewing angle of the accretion flow.