候选黑洞X射线双星MAXI J1659-152爆发时的VLT/X-Shooter光谱
VLT/X-shooter spectroscopy of the candidate black-hole X-ray binary MAXI J1659-152 in outburst
摘要：
我们呈现了MAXI J1659-152在2010年X射线爆发开始时的光学到近红外光谱。该光谱是在爆发早期由ESO -甚大望远镜（VLT）上的X-射手获得的，同时在较短和较长波长处进行了高质量的观测。在观测时，源处于低硬状态。X射线发射光谱包括许多宽的（~2000 km/s），双峰的H，HeI，HeII的发射轮廓，低质量的X射线双星在爆发期间的特征签名。我们没有探测到低质量伴星的光谱特征。弥漫的星际带的强度的结果在一个下限的总星际消光Av ~ 0.4 mag. Using中性氢柱密度从X射线光谱得到的，我们估计Av ~1 mag. The径向速度结构的星际NaI D和CaII H & K线的结果在一个下限的距离~ 4 +/- 1千秒差距，与以前的估计一致。利用该距离和Av，去红的光谱能量分布表示平坦的圆盘光谱。随后的两个10分钟的X射线光谱显示出显着的变化，在红翼的发射线配置文件，表明在磁盘的密度结构的全球变化，虽然在一个时间尺度上比典型的粘性时间尺度的磁盘短得多。
英文摘要：
We present the optical to near-infrared spectrum of MAXI J1659-152, during the onset of its 2010 X-ray outburst. The spectrum was obtained with X-shooter on the ESO - Very Large Telescope (VLT) early in the outburst simultaneous with high quality observations at both shorter and longer wavelengths. At the time of the observations, the source was in the low-hard state. The X-shooter spectrum includes many broad (~2000 km/s), double-peaked emission profiles of H, HeI, HeII, characteristic signatures of a low-mass X-ray binary during outburst. We detect no spectral signatures of the low-mass companion star. The strength of the diffuse interstellar bands results in a lower limit to the total interstellar extinction of Av ~ 0.4 mag. Using the neutral hydrogen column density obtained from the X-ray spectrum we estimate Av ~1 mag. The radial-velocity structure of the interstellar NaI D and CaII H & K lines results in a lower limit to the distance of ~ 4 +/- 1 kpc, consistent with previous estimates. With this distance and Av, the dereddened spectral energy distribution represents a flat disk spectrum. The two subsequent 10 minute X-shooter spectra show significant variability in the red wing of the emission-line profiles, indicating a global change in the density structure of the disk, though on a timescale much shorter than the typical viscous timescale of the disk.
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