A trio of metal-rich dust and gas discs found orbiting candidate white dwarfs with K-band excess
A trio of metal-rich dust and gas discs found orbiting candidate white dwarfs with K-band excess
复制标题
发现了三个富含金属的尘埃和气体盘，它们围绕候选白矮星运行，并且具有过量的 K 波段
DOI：
10.1111/j.1365-2966.2012.20421.x
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发表时间：
2011
影响因子：
4.8
通讯作者：
D. Koester
中科院分区：
文献类型：
--
作者：
J. Farihi;B. Gänsicke;P. Steele;J. Girven;M. Burleigh;E. Breedt;D. Koester
本文报道了后续的光度和光谱观测，包括来自SDSS的七颗白色矮星的温暖斯皮策IRAC光度测量，在UKIDSS K波段观测中具有明显的过剩通量。六个科学目标是从16785 DA星星候选者中选出的，这些候选者在SDSS DR 7中通过光谱或光度确定，在空间上与UKIDSS DR 8中的HK检测交叉相关。因此，选择标准是完全独立的恒星质量，有效温度高于8000 K和大气金属的存在（或不存在）。一个目标的红外通量与空间上未分辨的M晚期或L早期伴星相一致，而三颗恒星则表现出与温暖的星周尘埃相一致的过量辐射。这些目标的光谱能量分布类似于已知的尘埃白色矮星，具有高分数红外光度（因此K波段过量）。光谱学显示，盘状过剩的恒星被重元素污染，表明星周物质正在不断吸积。其中一个圆盘显示出气体成分-迄今为止报道的第四个-并围绕一颗相对较冷的星星运行，表明气体是通过碰撞而不是升华产生的，支持了最近事件的图片。由此产生的统计数据产生的下限为0.8%的分数尘埃盘在DA型白色矮星冷却年龄小于1 Gyr。两个总体结果是值得注意的：（i）所有的恒星，其多余的红外线发射是一致的尘埃是富含金属和（ii）没有发现任何恒星温度超过25000 K有这种类型的过剩，尽管足够的敏感性。© 2012作者每月通知的皇家天文学会© 2012 RAS。
This paper reports follow-up photometric and spectroscopic observations, including warm Spitzer IRAC photometry of seven white dwarfs from the SDSS with apparent excess flux in UKIDSS K-band observations. Six of the science targets were selected from 16785 DA star candidates identified either spectroscopically or photometrically within SDSS DR7, spatially cross-correlated with HK detections in UKIDSS DR8. Thus, the selection criteria are completely independent of stellar mass, effective temperature above 8000K and the presence (or absence) of atmospheric metals. The infrared fluxes of one target are compatible with a spatially unresolved late M or early L-type companion, while three stars exhibit excess emissions consistent with warm circumstellar dust. These latter targets have spectral energy distributions similar to known dusty white dwarfs with high fractional infrared luminosities (thus the K-band excesses). Optical spectroscopy reveals the stars with disc-like excesses are polluted with heavy elements, denoting the ongoing accretion of circumstellar material. One of the discs exhibits a gaseous component - the fourth reported to date - and orbits a relatively cool star, indicating the gas is produced via collisions as opposed to sublimation, supporting the picture of a recent event. The resulting statistics yield a lower limit of 0.8 per cent for the fraction dust discs at DA-type white dwarfs with cooling ages less than 1Gyr. Two overall results are noteworthy: (i) all stars whose excess infrared emission is consistent with dust are metal rich and (ii) no stars warmer than 25000K are found to have this type of excess, despite sufficient sensitivity. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.