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arXiv 1907.02112astro-ph.SRastro-ph.EP
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抑制TRAPPIST-1的无线电发射

Constraining the Radio Emission of TRAPPIST-1

Anna Hughes, Aaron Boley, Rachel Osten, Jacob White

备注：
9 pages, 3 figures, accepted to ApJ
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摘要：

TRAPPIST-1是一颗超冷矮星（UCD），拥有7颗类地行星，其中至少有3颗在宜居带内运行。对这种低质量恒星的无线电发射知之甚少;在射频上几乎没有检测到UCD，检测的可能性与恒星的性质只有松散的关系。相对于其他低质量的恒星，像TRAPPIST-1这样自转缓慢的UCD往往是射电暗淡的，而快速自转的UCD往往有很强的射电辐射，尽管情况并非总是如此。我们目前的无线电观测TRAPPIST-1使用ALMA在97.5 GHz和VLA在44 GHz。TRAPPIST-1在任一频率下均未检测到，我们将$3 σ$的通量上限分别设置为10.6和16.2 $μ$ μ。我们使用我们的结果来约束的磁性和可能的外向高能粒子辐射的恒星。来自UCD的无线电发射的存在表明恒星环境可能对周围行星上的生命构成威胁。回旋同步辐射，在20和100千兆赫之间的频率可辨别的，是唯一的过程，可以用来推断的存在下，在磁重联事件释放的高能粒子。由于M矮星是类地行星的频繁宿主，因此描述它们的恒星辐射是评估可居住性的关键部分。暴露在向外的高能粒子辐射中--可以通过无线电通量追踪--可以侵蚀行星大气。虽然我们的结果并不意味着TRAPPIST-1行星适合生命，但我们没有发现任何证据表明它们因质子通量而明显不适合。

英文摘要：

TRAPPIST-1 is an ultracool dwarf (UCD) with a system of 7 terrestrial planets, at least three of which orbit in the habitable zone. The radio emission of such low-mass stars is poorly understood; few UCDs have been detected at radio frequencies at all, and the likelihood of detection is only loosely correlated with stellar properties. Relative to other low-mass stars, UCDs with slow rotation such as TRAPPIST-1 tend to be radio dim, whereas rapidly rotating UCDs tend to have strong radio emission - although this is not always the case. We present radio observations of TRAPPIST-1 using ALMA at 97.5 GHz and the VLA at 44 GHz. TRAPPIST-1 was not detected at either frequency and we place $3 σ$ upper flux limits of 10.6 and 16.2 $μ$Jy, respectively. We use our results to constrain the magnetic properties and possible outgoing high energy particle radiation from the star. The presence of radio emission from UCDs is indicative of a stellar environment that could pose a threat to life on surrounding planets. Gyrosynchrotron emission, discernible at frequencies between 20 and 100 GHz, is one of the only processes that can be used to infer the presence of high energy particles released during magnetic reconnection events. Since M dwarfs are frequent hosts of terrestrial planets, characterizing their stellar emission is a crucial part of assessing habitability. Exposure to outgoing high energy particle radiation - traceable by radio flux - can erode planetary atmospheres. While our results do not imply that the TRAPPIST-1 planets are suitable for life, we find no evidence that they are overtly unsuitable due to proton fluxes.

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