NGTS and HST insights into the long-period modulation in GW Librae
NGTS and HST insights into the long-period modulation in GW Librae
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NGTS 和 HST 对 GW Librae 长周期调制的见解
DOI：
10.1093/mnras/staa4015
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发表时间：
2021
影响因子：
4.8
通讯作者：
Chote P
中科院分区：
文献类型：
--
作者：
Chote P
作为下一代过境调查的一部分，获得了2017年跨越7.5个月的吸积白色矮星系GW Librae的光变曲线。该数据集包括来自148个晴朗夜晚的787小时测光，允许在比以前实现的长得多的观测基线上从一个晚上到另一个晚上跟踪长（小时）和短周期（20分钟）调制信号的行为。在GW Lib的先前观测中间歇性地检测到的长周期调制被发现是一个持续的特征，在几天的时间尺度上在周期为1.83 min和2-4 h的状态之间演化。发现20 min信号在活动期间具有广泛稳定的振幅和频率，但确认了先前注意到的相位不稳定性。用哈勃太空望远镜上的宇宙起源摄谱仪获得的紫外线观测结果表明，4小时调制的紫外线与光通量之比为1.05，20分钟调制的紫外线与光通量之比为1.01，但由于非同时观测而引起的警告。这些结果增加了进一步的观测证据，表明这些神秘的信号必须来自白色矮星，突出了我们在理论上理解驱动它们的机制方面的持续差距。
Light curves of the accreting white dwarf pulsator GW Librae spanning a 7.5-month period in 2017 were obtained as part of theNext-Generation Transit Survey. This data set comprises 787 h of photometry from 148 clear nights, allowing the behaviour of the long (hours) and short-period (20 min) modulation signals to be tracked from night to night over a much longer observing baseline than has been previously achieved. The long-period modulations intermittently detected in previous observations of GW Lib are found to be a persistent feature, evolving between states with periods ≃ 83 min and 2–4 h on time-scales of several days. The 20 min signal is found to have a broadly stable amplitude and frequency for the duration of the campaign, but the previously noted phase instability is confirmed. Ultraviolet observations obtained with the Cosmic Origin Spectrograph on-board theHubble Space Telescopeconstrain the ultraviolet-to-optical flux ratio to ≃5 for the 4 h modulation, and ≲1 for the 20 min period, with caveats introduced by non-simultaneous observations. These results add further observational evidence that these enigmatic signals must originate from the white dwarf, highlighting our continued gap in theoretical understanding of the mechanisms that drive them.