The SPHINX M-dwarf Spectral Grid. I. Benchmarking New Model Atmospheres to Derive Fundamental M-dwarf Properties
The SPHINX M-dwarf Spectral Grid. I. Benchmarking New Model Atmospheres to Derive Fundamental M-dwarf Properties
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DOI：
10.3847/1538-4357/acabc2
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发表时间：
2022-06
期刊：
影响因子：
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通讯作者：
A. Iyer;M. Line;P. Muirhead;J. Fortney;E. Gharib-Nezhad
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文献类型：
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作者：
A. Iyer;M. Line;P. Muirhead;J. Fortney;E. Gharib-Nezhad
在我们的太阳和银河系附近，大约70%-80%的恒星是M矮星。相对于太阳型恒星，它们跨越一系列低质量和低温度，促进了整个大气层的分子形成。标准的恒星大气模型主要是为FGK恒星设计的，在表征冷恒星光谱中的宽带分子特征时面临挑战。本文介绍了一个新的一维自洽辐射-对流热化学平衡模型SPHINX，它给出了M矮星低分辨率（R ≥ 250）的大气和光谱网格。我们将最新的预先计算的吸收截面与压力加宽的主要分子在晚K，早期/主序星M。然后，我们验证我们的网格模型确定的基本属性（T eff，log g，[M/H]，半径和C/O）为10个基准M+G双星已知的主机金属丰度和10 M矮星干涉测量角直径。通过使用高斯过程推理工具海星，我们考虑了低分辨率（SpeX，SNIFS和STIS的光谱拼接）观测中的相关和系统噪声，并得出了基本M矮星大气参数的稳健估计。此外，我们评估了光球不均匀性对推断的[M/H]的影响，并发现它可以解释一些偏离观测。我们还探讨了所采用的对流混合长度参数是否会影响推断的半径，有效温度，和[M/H]，并再次发现，可以解释干涉观测和模型导出的参数之间的差异较冷的M矮星。主要是，我们展示了利用低分辨率M矮星光谱中宽带分子吸收特征的独特优势，并展示了改善系外行星宿主和棕矮星同伴基本特性约束的能力。
About 70%–80% of stars in our solar and Galactic neighborhood are M dwarfs. They span a range of low masses and temperatures relative to solar-type stars, facilitating molecule formation throughout their atmospheres. Standard stellar atmosphere models primarily designed for FGK stars face challenges when characterizing broadband molecular features in spectra of cool stars. Here, we introduce SPHINX—a new 1D self-consistent radiative–convective thermochemical equilibrium chemistry model grid of atmospheres and spectra for M dwarfs in low resolution (R ∼ 250). We incorporate the latest precomputed absorption cross sections with pressure broadening for key molecules dominant in late-K, early/main-sequence-M stars. We then validate our grid models by determining fundamental properties (T eff, log g, [M/H], radius, and C/O) for 10 benchmark M+G binary stars with known host metallicities and 10 M dwarfs with interferometrically measured angular diameters. Incorporating the Gaussian process inference tool Starfish, we account for correlated and systematic noise in low-resolution (spectral stitching of SpeX, SNIFS, and STIS) observations and derive robust estimates of fundamental M-dwarf atmospheric parameters. Additionally, we assess the influence of photospheric heterogeneity on inferred [M/H] and find that it could explain some deviations from observations. We also probe whether the adopted convective mixing length parameter influences inferred radii, effective temperature, and [M/H] and again find that may explain discrepancies between interferometric observations and model-derived parameters for cooler M dwarfs. Mainly, we show the unique strength in leveraging broadband molecular absorption features occurring in low-resolution M dwarf spectra and demonstrate the ability to improve constraints on fundamental properties of exoplanet hosts and brown-dwarf companions.