AI 中文总结
研究八颗开普勒发现的“掩星”恒星，利用SpeX光谱仪发现其He I等谱线具夜间间变异性，吸积率测定存在Paβ与Brγ的差异，验证了高度倾斜盘的自吸收效应。
AI 中文摘要
解释恒星“掩星”现象的一种情景是：最内侧盘区与恒星视线的倾角大于60度，且与最外侧盘的倾角无关（即“错位”或“破碎”盘）。若这些盘中的尘埃与气体取样同一物质，那么侧视盘观测到的气体与尘埃柱密度会高于普通盘。我们利用NASA红外望远镜设施的SpeX光谱仪（光谱分辨率R≈750），研究了开普勒发现的八颗“掩星”恒星的夜间间变异性。1.083微米的He I线呈现出多种轮廓，且每晚都发生变化；多数情况下存在指示气体流入的逆P Cygni轮廓，线轮廓（及连续谱流量水平）常以1天的时间尺度变化，帕邢线与布拉开线也以类似时间尺度变化。其中一颗天体V935 Sco的Paβ与Brγ在5周内从发射线变为吸收线；另一颗天体EPIC 203850058的Paβ在2017年为发射线，2018年完全消失。利用Paβ测定的这些恒星吸积率往往小于利用Brγ测定的，表明前者比后者更易受自吸收影响，这符合高度倾斜盘的预期。
英文摘要
One of the scenarios used to explain the dipper phenomenon in stars is having the innermost disk regions being close to the line of sight to the star - inclined greater than 60 degrees - regardless of the inclination of the outermost disk ("mis-aligned" or "broken" disks). If the dust and gas in these disks sample the same material, edge-on disks will be viewed through larger column densities of gas and dust than the average disk. We have examined inter-night variability of eight Kepler-discovered dipper stars using the SpeX spectrograph on NASA's Infrared Telescope facility at a spectral resolving power of R~750. The He I line at 1.083 microns exhibits a wide variety of profiles, which change from night to night. In the majority of cases, an inverse P Cygni profile, indicative of inflowing gas, is present. The line profile (and continuum flux level) often change on time scales of 1 day. The Paschen and Brackett lines also change on similar time scales. In one object, V935 Sco, Pa beta and Br gamma went from being in emission to being in absorption over the course of 5 weeks. In another, EPIC 203850058, Pa beta went from being in emission in 2017 to vanishing altogether in 2018. The accretion rates determined using Pa beta for these stars tend to be smaller than those using Br gamma, indicating that the former line is more susceptible to self-absorption than the latter, as would be expected for a highly inclined disk.
Comments47 pages, 56 figures
