arXiv 2205.086202022-05-17astro-ph.SRastro-ph.EP

M矮星伴星的亚巨星表面特征模拟

Modeling Stellar Surface Features on Subgiant Star with an M-dwarf Companion

Maria C. Schutte, Leslie Hebb, Simon Lowry, John Wisniewski, Suzanne L. Hawley, Suvrath Mahadevan, Brett M. Morris, Paul Robertson, Graeme Rohn, Gudmundur Stefansson

备注：: 16 pages, 17 figures; Accepted to AJ
DOI：: 10.3847/1538-3881/ac70ca

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摘要：

了解太阳以外的恒星表面的磁场活动对于系外行星分析非常重要，可以正确描述系外行星的大气层，并进一步描述各种恒星上的恒星活动。模拟不同光谱类型和自转速率的恒星表面特征是理解这些恒星磁活动的关键。利用开普勒望远镜的观测数据，我们使用STarSPot（STSP）星点模拟程序测量了KOI-340的星点位置和大小。KOI-340是一个食双星，由一颗次巨星（$\rm T_{\rm eff} = 5593 \pm 27 K; R_{*} = 1.98 \pm 0.05 R_{\odot}$）和一颗M矮星伴星（$M_{*} = 0.214 \pm 0.006 M_{\odot}$）组成。STSP使用一种新的技术来测量光斑的位置和半径，通过使用凌日次级来使用高精度测光研究和模拟恒星表面上的单个活动区域。我们发现KOI-340主星上的黑子特征的平均大小是恒星半径的$\sim$ 10%，即太阳黑子平均大小的两倍。KOI-340上的斑点出现在每个经度上，并显示出可能的差异旋转迹象。KOI-340的原色的最小斑点面积分数为$2\substack{+12\\ -2} \%$，而太阳的斑点面积最多为0.2%。KOI-340的一次凌日显示出一个与斑一致的凌日信号;这个斑正好出现在一个暗斑之前，表明斑和斑可能共同位于恒星表面。

英文摘要：

Understanding magnetic activity on the surface of stars other than the Sun is important for exoplanet analyses to properly characterize an exoplanet's atmosphere and to further characterize stellar activity on a wide range of stars. Modeling stellar surface features of a variety of spectral types and rotation rates are key to understanding of the magnetic activity of these stars. Using data from Kepler, we use the starspot modeling program STarSPot (STSP) to measure the position and size of spots for KOI-340 which is an eclipsing binary consisting of a subgiant star ($\rm T_{\rm eff} = 5593 \pm 27 K; R_{*} = 1.98 \pm 0.05 R_{\odot}$) with an M-dwarf companion ($M_{*} = 0.214 \pm 0.006 M_{\odot}$). STSP uses a novel technique to measure the spot positions and radii by using the transiting secondary to study and model individual active regions on the stellar surface using high-precision photometry. We find the average size of spot features on KOI-340's primary is $\sim$10% the radius of the star, i.e. two times larger than the mean size of Solar-maximum sunspots. The spots on KOI-340 are present at every longitude and show possible signs of differential rotation. The minimum fractional spotted area of KOI-340's primary is $2\substack{+12\\ -2} \%$ while the spotted area of the Sun is at most 0.2%. One transit of KOI-340 shows a signal in the transit consistent with a plage; this plage occurs right before a dark spot indicating the plage and spot might be co-located on the surface of the star.

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