A deep XMM–Newton observation of the ultraluminous X-ray source Holmberg II X-1: the case against a 1000-M (cid:1) black hole
A deep XMM–Newton observation of the ultraluminous X-ray source Holmberg II X-1: the case against a 1000-M (cid:1) black hole
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超亮 X 射线源 Holmberg II X-1 的深度 XMM-牛顿观测：针对 1000 米（cid:1）黑洞的案例
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发表时间：
2005
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通讯作者：
P. Uttley
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作者：
M. Goad;T. Roberts;J. Reeves;P. Uttley
我们目前的结果从112-ks长的XMM-牛顿在超亮X射线源（ULX）Holmberg II X-1（Ho II X-1），长期以来被认为是失踪类中等质量黑洞（IMBHs）的最佳候选人之一。我们的数据包括ULX的第一个高质量XMM-牛顿/RGS（反射光栅光谱仪）光谱，以及具有前所未有的信噪比的XMM-牛顿/EPIC（欧洲照片成像相机）光谱。详细的时序分析表明，从分钟到小时的时间尺度上的任何变化都非常微弱（小于百分之几的均方根），尽管光子计数统计可以隐藏更短时间尺度上的更大幅度变化。这一结果表明，如果Ho II X-1窝藏IMBH，那么我们正在观察这个源在一个非常不寻常的和非典型的状态相比，与其他大质量的吸积系统的已知的变异行为。此外，与银河X射线双星不同，我们的光谱分析表明可能存在光学厚低温日冕。综合我们的时间和光谱分析表明，紧凑的同伴最有可能是一个高光度的黑洞双星系统类似于GRS 1915 + 105，银河系微类星体，窝藏一个质量不超过100 M的紧凑物体（cid：1）。KeV光变曲线，用于Ho II X-1的长期观测。将数据分箱为100-s间隔，并减去背景。我们还示出了在相同的频带中，对于相同的孔径的背景发射的相对强度。数据中的间隙是由遥测缓冲区由于高背景重复率而填满引起的。为了清楚起见，我们只显示了暴露时间为75 s或更长的数据箱。
We present results from a 112-ks long look by XMM–Newton at the ultraluminous X-ray source (ULX) Holmberg II X-1 (Ho II X-1), long thought to be the one of best candidates for the missing class of intermediate-mass black holes (IMBHs). Our data comprises the first high-quality XMM–Newton /RGS (reflection grating spectrometer) spectrum of an ULX, and an XMM–Newton /EPIC (European Photo Imaging Camera) spectrum with unprecedented signal-to-noise ratio. A detailed timing analysis shows that any variability on time-scales of minutes to hours is very weak (less than a few per cent fractional rms), though larger amplitude variations on much shorter time-scales could be hidden by photon counting statistics. This result suggests that if Ho II X-1 harbours an IMBH, then we are observing this source in a highly unusual and atypical state when compared with the known variability behaviour of other accreting systems of large mass. Moreover, unlike galactic X-ray binaries, our spectral analysis indicates the possible presence of an optically thick low-temperature corona. Taken together our timing and spectral analysis suggests that the compact companion is most likely a high-luminosity analogue of black hole binary systems similar to GRS 1915 + 105, the galactic microquasar, harbouring a compact object of mass no greater than 100 M (cid:1) . keV light curve for the long look at Ho II X-1. The data is binned to 100-s intervals, and background subtracted. We also show the relative intensity of the background emission in the same band, for the same aperture. The gaps in the data are caused by the telemetry buffers filling up due to the high background flaring rate. For clarity, we only show data bins where we have 75 s or more of exposure.