WD 1145+017的快速分光光度法
Fast spectrophotometry of WD 1145+017
摘要：
WD 1145+017是目前已知的唯一一颗表现出行星碎片周期性凌日以及星周气体吸收线的白矮星。我们提出了第一个同时快速光学分光光度法和宽带光度的系统，获得与大加那利望远镜（GTC）和利物浦望远镜（LT），分别。观测的时间跨度为$5.5$ h，略长于碎片的$4.5$ -h轨道周期。将GTC分光光度法分为五个波长带显示没有显著的颜色差异，证实了光学中的灰色过渡。我们认为，吸收的光学厚的结构是一个合理的替代解释的无色性质的过境，可以允许存在的小尺寸（$\simμ$ m）的粒子。我们的数据中记录的最长（$87$ min）和最深（$50$衰减百分比）的过境表现出围绕最小光的复杂结构，可以很好地模拟多个重叠的尘埃云。最强的拱星吸收线Fe II $λ$ 5169在这次凌日期间明显减弱，其等效宽度从平均的$2$ 100减小到$1$ 100，支持拱星气体和尘埃之间的空间相关性。最后，我们利用盖亚数据发布2和档案测光确定白矮星参数。采用含微量氢和金属的氦主导大气，以及变红的$E(B-V)=0.01$，我们发现$T_\mathrm{eff}=15\,020 \pm 520$ K，$\log g=8.07\pm0.07$，对应于$M_\mathrm{WD}=0.63\pm0.05\ \mbox{$ \mathrm{M}_{\odot} $}$和冷却年龄为$224\pm30$ Myr。
英文摘要：
WD 1145+017 is currently the only white dwarf known to exhibit periodic transits of planetary debris as well as absorption lines from circumstellar gas. We present the first simultaneous fast optical spectrophotometry and broad-band photometry of the system, obtained with the Gran Telescopio Canarias (GTC) and the Liverpool Telescope (LT), respectively. The observations spanned $5.5$ h, somewhat longer than the $4.5$-h orbital period of the debris. Dividing the GTC spectrophotometry into five wavelength bands reveals no significant colour differences, confirming grey transits in the optical. We argue that absorption by an optically thick structure is a plausible alternative explanation for the achromatic nature of the transits that can allow the presence of small-sized ($\simμ$m) particles. The longest ($87$ min) and deepest ($50$ per cent attenuation) transit recorded in our data exhibits a complex structure around minimum light that can be well modelled by multiple overlapping dust clouds. The strongest circumstellar absorption line, Fe II $λ$5169, significantly weakens during this transit, with its equivalent width reducing from a mean out-of-transit value of $2$ Å to $1$ Å in-transit, supporting spatial correlation between the circumstellar gas and dust. Finally, we made use of the Gaia Data Release 2 and archival photometry to determine the white dwarf parameters. Adopting a helium-dominated atmosphere containing traces of hydrogen and metals, and a reddening $E(B-V)=0.01$ we find $T_\mathrm{eff}=15\,020 \pm 520$ K, $\log g=8.07\pm0.07$, corresponding to $M_\mathrm{WD}=0.63\pm0.05\ \mbox{$\mathrm{M}_{\odot}$}$ and a cooling age of $224\pm30$ Myr.
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