The gaseous debris disk of the white dwarf SDSS J1228+1040. HST/COS search for far-ultraviolet signatures
The gaseous debris disk of the white dwarf SDSS J1228+1040. HST/COS search for far-ultraviolet signatures
复制标题
DOI：
10.1051/0004-6361/201628403
复制
发表时间：
2016-07
期刊：
影响因子：
--
通讯作者：
S. Hartmann;T. Nagel;T. Rauch;K. Werner
中科院分区：
文献类型：
--
作者：
S. Hartmann;T. Nagel;T. Rauch;K. Werner
白矮星(WD)周围的气体和尘埃碎片盘是由潮汐破碎的行星体形成的。这提供了一个机会，通过测量WD吸积大气中的元素丰度来确定系外物质的组成。要做到这一点，更直接的方法是通过光谱分析光盘本身。目前，通过圆盘发射线探测到的化学元素的数量少于通过WD大气中的发射线探测到的物种的数量。我们评估了一个研究得很好的天体(SDSSJ122859.93+104032.9)的远紫外线光谱，以寻找波长为<；1050埃的盘特征，其中莱曼系列的宽吸收线有效地阻止了WD光球通量。我们使用哈勃太空望远镜/宇宙起源光谱仪进行了FUV观测(950-1240埃)，并使用了存档的光谱。我们将它们与非局域热力学平衡模型光谱进行了比较。此外，我们还研究了CaII红外三重态(IRT)的谱线轮廓，以约束盘的几何形状和成分。在紫外光谱中没有检测到圆盘发射线，表明圆盘的有效温度约为5000K。CaII IRT的长时间变异性用块状地球成分的进动盘模型再现，其表面质量密度为0.3g/cm2，半径从55扩展到90WD。该圆盘呈螺旋形，进动周期约为37年，证实了先前的结果。
Gaseous and dust debris disks around white dwarfs (WDs) are formed from tidally disrupted planetary bodies. This offers an opportunity to determine the composition of exoplanetary material by measuring element abundances in the accreting WD's atmosphere. A more direct way to do this is through spectral analysis of the disks themselves. Currently, the number of chemical elements detected through disk emission-lines is smaller than that of species detected through lines in the WD atmospheres. We assess the far-ultraviolet (FUV) spectrum of one well-studied object (SDSS J122859.93+104032.9) to search for disk signatures at wavelengths <1050 angstrom, where the broad absorption lines of the Lyman series effectively block the WD photospheric flux. We performed FUV observations (950-1240 angstrom) with the Hubble Space Telescope/Cosmic Origins Spectrograph and used archival optical spectra. We compared them with non-local thermodynamic equilibrium model spectra. In addition, we investigate the Ca II infrared triplet (IRT) line profiles to constrain disk geometry and composition. No disk emission-lines were detected in the FUV spectrum, indicating that the disk effective temperature is about 5000K. The long-time variability of the Ca II IRT was reproduced with a precessing disk model of bulk Earth-like composition, having a surface mass density of 0.3g/cm2 and an extension from 55 to 90 WD radii. The disk has a spiral shape that precesses with a period of approximately 37 years, confirming previous results.