V4641Sgr - A super-Eddington source enshrouded by an extended envelope
V4641Sgr - A super-Eddington source enshrouded by an extended envelope
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V4641Sgr - 被扩展包络包围的超级爱丁顿源
DOI：
10.1051/0004-6361:20020189
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
Russia.
中科院分区：
文献类型：
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作者：
M.Revnivtsev;R. Sunyaev;M.Gilfanov;E. C. Mpa;Garching;H Germany;S. R. Institute;Moscow;Russia.
不寻常的快速瞬态V4641 Sgr的光谱学将其质量限制为8.7{11.7 M（9：6 M是最佳t值），距离限制为7.4{12.3 kpc（Orosz等人，2001年）。在这个距离上，由ASM/RXTE在2{12 keV能带中测量的峰值通量意味着X射线光度超过2{3 10 39 erg s-1，即接近或高于9：6 M黑洞的爱丁顿极限。测光结果表明，在爆发高峰期，视星等相对于静止水平增加了4：7 m，达到mV 3 10 41 erg s 1 30 0 LEdd。我们认为，光学数据强烈建议存在一个扩展的信封周围的源，吸收X射线通量，并重新发射它在光学和紫外线。这些数据还表明，这种包层在紫外线、极紫外线和软X射线中应该是光学薄的。V4641 Sgr在光学耀斑峰值时的观测性质与SS 433非常相似。这个包层很可能是黑洞以接近或超爱丁顿的速度吸积质量的结果。当视光度下降到远低于爱丁顿值时，在源的后续演化过程中，包络消失。因此，这一瞬态源为我们提供了直接的证据，证明了在质量吸积率接近或高于理论模型很久以前预测的临界爱丁顿值时，吸积流的性质会发生巨大变化。
Optical spectroscopy of an unusual fast transient V4641 Sgr constrains its mass to be 8.7{11.7 M (9:6 M is the best t value) and the distance to 7.4{12.3 kpc (Orosz et al. 2001). At this distance the peak flux as measured by ASM/RXTE in 2{12 keV energy band implies the X-ray luminosity exceeding 2{3 10 39 erg s 1 , i.e. near or above the Eddington limit for a 9:6 M black hole. Optical photometry shows that at the peak of the optical outburst the visual magnitude increased by mV > 4:7 m relative to the quiescent level and reached mV 3 10 41 erg s 1 300 LEdd. We argue that the optical data strongly suggest the presence of an extended envelope surrounding the source which absorbs X{ray flux and reemits it in the optical and UV. The data also suggest that this envelope should be optically thin in UV, EUV and soft X-rays. The observed properties of V4641 Sgr at the peak of an optical flare are very similar to those of SS433. This envelope is likely the result of a near- or super-Eddington rate of mass accretion onto the black hole. The envelope vanishes during subsequent evolution of the source when the apparent luminosity drops well below the Eddington value. Thus this transient source provides us with direct proof of the dramatic change in the character of an accretion flow at the mass accretion rate near or above the critical Eddington value as predicted long ago by the theoretical models.