A Search for Planetary Metastable Helium Absorption in the V1298 Tau System-猫眼课题宝

DOI：

10.3847/1538-3881/ac1bb0

发表时间：

2021-08

期刊：

The Astronomical Journal

影响因子：

通讯作者：

中科院分区：

其他

文献类型：

作者：

S. Vissapragada;G. Stefansson;M. Greklek-McKeon;A. Oklopčić;H. Knutson;J. Ninan;S. Mahadevan;C. Cañas;Yayaati Chachan;W. Cochran;K. Collins;F. Dai;T. David;S. Halverson;S. Hawley;L. Hebb;S. Kanodia;A. Kowalski;J. Livingston;M. Maney;A. Metcalf;C. Morley;L. Ramsey;P. Robertson;Arpita Roy;J. Spake;C. Schwab;R. Terrien;S. Tinyanont;G. Vasisht;J. Wisniewski

在它们生命的早期，行星承受着来自其宿主恒星的极大量的电离辐射。对于具有原始氢和富氦包层的行星，这可能导致大量的质量损失。在年轻的行星系统中直接观测大气逃逸可以帮助阐明行星演化的这一关键阶段。在这项工作中，我们寻找亚稳态氦吸收的示踪剂稀薄气体逃逸大气中的三个行星轨道年轻的太阳模拟V1298头过境。我们使用HET/HPF表征恒星氦线，并发现它在几天到几个月的时间尺度上大幅演变。这条线在一小时的时间尺度上是稳定的，除了一组在恒星耀斑衰减阶段拍摄的光谱，其中吸收随时间增加。利用光束整形扩散器和以氦特征为中心的窄带滤波器，我们用Palomar/WIRC观察到四次凌日：两次部分凌日行星d（P = 12.4天），一次部分凌日行星B（P = 24.1天），一次完全凌日行星c（P = 8.2天）。我们没有探测到行星c的凌日，也没有发现行星B有过度吸收的证据，在我们的带通中ΔR B/R < 0.019。我们发现行星d有一个试探性的吸收信号，Δ Rd/R = 0.0205 ± 0.054，但最佳拟合模型需要在两个月的时间尺度上有相当大的（−100 ± 14分钟）凌日时间偏移。然而，我们的数据表明，V1298 Tau d可能具有很高的质量损失率，使其成为后续观测的优先目标。

Early in their lives, planets endure extreme amounts of ionizing radiation from their host stars. For planets with primordial hydrogen and helium-rich envelopes, this can lead to substantial mass loss. Direct observations of atmospheric escape in young planetary systems can help elucidate this critical stage of planetary evolution. In this work, we search for metastable helium absorption—a tracer of tenuous gas in escaping atmospheres—during transits of three planets orbiting the young solar analog V1298 Tau. We characterize the stellar helium line using HET/HPF, and find that it evolves substantially on timescales of days to months. The line is stable on hour-long timescales except for one set of spectra taken during the decay phase of a stellar flare, where absoprtion increased with time. Utilizing a beam-shaping diffuser and a narrowband filter centered on the helium feature, we observe four transits with Palomar/WIRC: two partial transits of planet d (P = 12.4 days), one partial transit of planet b (P = 24.1 days), and one full transit of planet c (P = 8.2 days). We do not detect the transit of planet c, and we find no evidence of excess absorption for planet b, with ΔR b/R ⋆ < 0.019 in our bandpass. We find a tentative absorption signal for planet d with ΔR d/R ⋆ = 0.0205 ± 0.054, but the best-fit model requires a substantial (−100 ± 14 minutes) transit-timing offset on a two-month timescale. Nevertheless, our data suggest that V1298 Tau d may have a high present-day mass-loss rate, making it a priority target for follow-up observations.

A Search for Planetary Metastable Helium Absorption in the V1298 Tau System

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