arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1009.2808astro-ph.HEastro-ph.COastro-ph.GA
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活动星系核RXJ1633 +4718黑洞吸积盘的X射线观测特征

X-ray observational signature of a black hole accretion disc in an active galactic nucleus RXJ1633+4718

Weimin Yuan, Bifang Liu, Hongyan Zhou, Tinggui Wang

摘要:

我们报告的发现,一个明亮的超软X射线过剩的射电响亮的窄线塞弗特1星系,RXJ 1633 +4718,从档案ROSAT观测。当与黑体配合时,这种发射的热温度低至32.5(+8.0,-6.0)eV。这与迄今为止在活动星系核(AGN)中发现的软X射线过剩的约0.1-0.2keV的正则温度形成了鲜明的对比,并且有趣地接近于该物体中假设吸积盘的最高温度。如果这种发射在本质上确实是黑体,那么导出的光度[3.5(+3.3,-1.5)x10^(44)ergs/s]推断出一个紧凑的发射区,其大小[~ 5x 10 ^(12)cm或0.33 AU]相当于活动星系核质量(3 x10^6 Msun)下黑洞史瓦西半径的几倍。事实上,这种超陡的X射线辐射可以很好地拟合为来自光学厚吸积盘的多温度黑体辐射的(康普顿散射)维恩尾,其参数推断(黑洞质量和吸积率)与使用光学发射线光谱的独立估计很好地一致。因此,我们认为这一功能作为长期寻求的X射线辐射直接从一个磁盘周围的超大质量黑洞的签名,提出了观测证据的黑洞吸积盘活动星系核。未来的观测数据质量会更好,同时对黑洞质量的独立测量也会得到改进,这可能会限制黑洞的自旋。

英文摘要:

We report the discovery of a luminous ultra-soft X-ray excess in a radio-loud narrow-line Seyfert1 galaxy, RXJ1633+4718, from archival ROSAT observations. The thermal temperature of this emission, when fitted with a blackbody, is as low as 32.5(+8.0,-6.0)eV. This is in remarkable contrast to the canonical temperatures of ~0.1-0.2keV found hitherto for the soft X-ray excess in active galactic nuclei (AGN), and is interestingly close to the maximum temperature predicted for a postulated accretion disc in this object. If this emission is indeed blackbody in nature, the derived luminosity [3.5(+3.3,-1.5)x10^(44)ergs/s] infers a compact emitting area with a size [~5x10^(12)cm or 0.33AU in radius] that is comparable to several times the Schwarzschild radius of a black hole at the mass estimated for this AGN (3x10^6Msun). In fact, this ultra-steep X-ray emission can be well fitted as the (Compton scattered) Wien tail of the multi-temperature blackbody emission from an optically thick accretion disc, whose parameters inferred (black hole mass and accretion rate) are in good agreement with independent estimates using optical emission line spectrum. We thus consider this feature as a signature of the long-sought X-ray radiation directly from a disc around a super-massive black hole, presenting observational evidence for a black hole accretion disc in AGN. Future observations with better data quality, together with improved independent measurements of the black hole mass, may constrain the spin of the black hole.

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