The High-energy Spectrum of the Nearby Planet-hosting Inactive Mid-M Dwarf LHS 3844
The High-energy Spectrum of the Nearby Planet-hosting Inactive Mid-M Dwarf LHS 3844
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DOI：
10.3847/1538-3881/abfa1c
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发表时间：
2021-04
期刊：
影响因子：
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通讯作者：
Hannah Diamond-Lowe;A. Youngblood;D. Charbonneau;G. King;D. Teal;S. Bastelberger;L. Corrales;
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文献类型：
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作者：
Hannah Diamond-Lowe;A. Youngblood;D. Charbonneau;G. King;D. Teal;S. Bastelberger;L. Corrales;
为了充分描述类地系外行星的大气层或缺乏大气层的特征，我们必须包括其主恒星提供的高能环境。附近的中M矮星LHS 3844拥有一个缺乏大气层的类地世界。我们展示了 HST/COS 捕获的 LHS 3844 从 1131 到 3215 Å 的时间序列紫外光谱。我们在 FUV 中检测到一束耀斑，其绝对能量为 8.96 ± 0.77 × 1028 erg，等效持续时间为 355 ± 31 s。我们分别提取耀斑和静态紫外光谱。对于每个光谱，我们使用 UV 线强度之间的相关性来估计 Lyα 通量。我们使用 Swift-XRT 对软 X 射线通量设定上限，并构建差分发射模型来估计被星际介质遮挡的通量。我们将 XUV 中的差分发射模型通量估计与依赖于 UV 中的 Lyα、Si iv 和 N v 线缩放的其他方法进行比较。对于静态，LHS 3844 的 XUV、FUV 和 NUV 通量相对于其测辐射热光度分别为 log10(L band/L Bol) =−3.65、−4.16 和 −4.48。这些值与 MUSCLES 调查发现的早期 M 矮星样本中发现的作为恒星有效温度函数的高能通量趋势一致。许多光谱上最容易接近的类地系外行星都围绕不活跃的中晚期 M 矮星（如 LHS 3844）运行。M 矮星高能光谱的测量对于系外行星的表征来说是更可取的，但并不总是可行。 LHS 3844 的光谱是这些世界当前辐射环境的有用代表。
To fully characterize the atmospheres, or lack thereof, of terrestrial exoplanets, we must include the high-energy environments provided by their host stars. The nearby mid-M dwarf LHS 3844 hosts a terrestrial world that lacks a substantial atmosphere. We present a time-series UV spectrum of LHS 3844 from 1131 to 3215 Å captured by HST/COS. We detect one flare in the FUV that has an absolute energy of 8.96 ± 0.77 × 1028 erg and an equivalent duration of 355 ± 31 s. We extract the flare and quiescent UV spectra separately. For each spectrum, we estimate the Lyα flux using correlations between UV line strengths. We use Swift-XRT to place an upper limit on the soft X-ray flux and construct a differential emission model to estimate flux that is obscured by the interstellar medium. We compare the differential emission model flux estimates in the XUV to other methods that rely on scaling from the Lyα, Si iv, and N v lines in the UV. The XUV, FUV, and NUV flux of LHS 3844 relative to its bolometric luminosity is log10(L band/L Bol) =−3.65, −4.16, and −4.48, respectively, for the quiescent state. These values agree with trends in high-energy flux as a function of stellar effective temperature found by the MUSCLES survey for a sample of early-M dwarfs. Many of the most spectroscopically accessible terrestrial exoplanets orbit inactive mid-to-late M dwarfs like LHS 3844. Measurements of M dwarf high-energy spectra are preferable for exoplanet characterization but are not always possible. The spectrum of LHS 3844 is a useful proxy for the current radiation environment for these worlds.