Quantifying the Transit Light Source Effect: Measurements of Spot Temperature and Coverage on the Photosphere of AU Microscopii with High-resolution Spectroscopy and Multicolor Photometry
Quantifying the Transit Light Source Effect: Measurements of Spot Temperature and Coverage on the Photosphere of AU Microscopii with High-resolution Spectroscopy and Multicolor Photometry
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DOI：
10.3847/1538-4357/ad0bed
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发表时间：
2023-10
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通讯作者：
W. Waalkes;Z. Berta-Thompson;Elisabeth Newton;A. Mann;Peter Gao;H. Wakeford;L. Alderson;P. Plavchan
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作者：
W. Waalkes;Z. Berta-Thompson;Elisabeth Newton;A. Mann;Peter Gao;H. Wakeford;L. Alderson;P. Plavchan
显微镜座Au（Au Mic）是一颗活跃的主序前M矮星，自转周期为4.86天。围绕Au Mic运行的两颗凌日行星Au Mic B和C是温暖的亚海王星，周期为8.5天和18.9天，是年轻行星大气观测的目标。在这里，我们研究Au Mic的未被掩盖的恒星黑子使用地面测光和光谱，以补充其行星的当前和未来的透射光谱。我们收集了Las Cumbres天文台（LCO）0.4 m SBIG测光研究星星的旋转调制和LCO网络的机器人Echelle光谱仪高分辨率光谱测量不同的光谱成分内的综合光谱的星星，参数化的三个光谱成分和它们的覆盖率。我们发现Au Mic的表面至少有两个光谱成分：一个是温度为4003−14+15 K的光球，另一个是温度为3003−71+63 K的冷点，覆盖了39% ± 4%的全球平均面积，在整个旋转过程中，平均面积增加和减少了5.1% ± 0.3%。我们还检测到填充因子小于0.5%的第三通量分量和在8500和10,000 K之间的很大程度上不确定的温度，我们归因于耀斑通量不完全忽略时，时间平均光谱。我们包括使用两个温度模型，我们发现强烈同意与三个温度的结果的斑点特性的测量。我们扩大使用各种技术来研究星点，将有助于我们更好地了解这个系统，并可能有应用程序来解释传输光谱的系外行星过境恒星的活动范围广泛的水平。
AU Microscopii (AU Mic) is an active 24 ± 3 Myr pre-main-sequence M dwarf in the stellar neighborhood (d = 9.7 pc) with a rotation period of 4.86 days. The two transiting planets orbiting AU Mic, AU Mic b and c, are warm sub-Neptunes on 8.5 and 18.9 day periods and are targets of interest for atmospheric observations of young planets. Here we study AU Mic’s unocculted starspots using ground-based photometry and spectra in order to complement current and future transmission spectroscopy of its planets. We gathered multicolor Las Cumbres Observatory (LCO) 0.4 m SBIG photometry to study the star's rotational modulations and LCO Network of Robotic Echelle Spectrographs high-resolution spectra to measure the different spectral components within the integrated spectrum of the star, parameterized by three spectral components and their coverage fractions. We find AU Mic’s surface has at least two spectral components: a T amb = 4003−14+15 K ambient photosphere and cool spots that have a temperature of T spot = 3003−71+63 K, covering a globally averaged area of 39% ± 4% which increases and decreases by 5.1% ± 0.3% from the average throughout a rotation. We also detect a third flux component with a filling factor less than 0.5% and a largely uncertain temperature between 8500 and 10,000 K that we attribute to flare flux not entirely omitted when time averaging the spectra. We include measurements of spot characteristics using a two-temperature model, which we find agree strongly with the three-temperature results. Our expanded use of various techniques to study starspots will help us better understand this system and may have applications for interpreting the transmission spectra for exoplanets transiting stars of a wide range of activity levels.