Detection of Absorption-Line Features in the X-Ray Spectra of the Galactic Superluminal Source GRO J1655–40
Detection of Absorption-Line Features in the X-Ray Spectra of the Galactic Superluminal Source GRO J1655–40
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DOI：
10.1086/305063
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发表时间：
1998-01
期刊：
影响因子：
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通讯作者：
Y. Ueda;H. Inoue;Y. Tanaka;K. Ebisawa;F. Nagase;T. Kotani;N. Gehrels
中科院分区：
文献类型：
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作者：
Y. Ueda;H. Inoue;Y. Tanaka;K. Ebisawa;F. Nagase;T. Kotani;N. Gehrels
本文报道了在超光速喷流源GRO J1655-40的能谱中探测到铁K吸收线。从1994年到1996年，我们观察了四次ASCA源。当X射线强度较低时（0.27- 0.57crab），在6.63 ± 0.07keV处发现明显的吸收线特征;当X射线强度较高时（2.2crab），在6.95 ± 0.10keV处发现明显的吸收线特征。前者是类氦铁的共振吸收线，后者是类氢铁的共振吸收线。这直接证明了在黑洞附近存在非球形的高度电离等离子体。铁的电离态的变化表明，等离子体被X射线照射的光电离。观测到的等效宽度（类氦Kα线约为60 eV）和电离参数λ（~103）将等离子体的尺寸限制在~1010 cm。这些特性与其他超光速源GRS 1915+105的相似性可能意味着这种高度电离的等离子体的存在与相对论喷流的形成之间存在某种联系。
We report the detection of iron K-absorption lines in the energy spectra of the superluminal jet source GRO J1655-40. We observed the source with ASCA on four occasions from 1994 through 1996. Significant absorption-line features were found at 6.63 ± 0.07 keV when the X-ray intensity was low (0.27-0.57 crab) and at 6.95 ± 0.10 keV when the intensity was high (2.2 crab). The former are interpreted as resonance absorption lines from helium-like iron and the latter are those from hydrogen-like iron, respectively. This gives direct evidence for the presence of highly ionized plasma in a nonspherical configuration in the vicinity of the black hole. The change of the ionization state of iron suggests that the plasma is photoionized by X-ray irradiation. The observed equivalent width (about 60 eV for the helium-like Kα line) and the ionization parameter ξ (~103) constrain the size of the plasma to ~1010 cm. The similarity of these properties to those of the other superluminal source GRS 1915+105 may imply some connection between the presence of such highly ionized plasma and the formation of relativistic jets.