STARSPOT DISTRIBUTIONS ON FULLY CONVECTIVE M DWARFS: IMPLICATIONS FOR RADIAL VELOCITY PLANET SEARCHES
STARSPOT DISTRIBUTIONS ON FULLY CONVECTIVE M DWARFS: IMPLICATIONS FOR RADIAL VELOCITY PLANET SEARCHES
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DOI：
10.1088/0004-637x/812/1/42
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发表时间：
2015-09
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通讯作者：
John R. Barnes;S. Jeffers;H. Jones;Ya. V. Pavlenko;Ya. V. Pavlenko;James S. Jenkins;James S. Jenkins;C. Haswell;M. Lohr
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文献类型：
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作者：
John R. Barnes;S. Jeffers;H. Jones;Ya. V. Pavlenko;Ya. V. Pavlenko;James S. Jenkins;James S. Jenkins;C. Haswell;M. Lohr
由于M4.5-M9矮星的赤道自转速度平均约为10 km s-1，因此针对这一恒星群体的径向速度测量可能需要找到有效消除星点抖动的方法。我们提出了第一个高分辨率的多普勒图像的M4.5矮星，GJ 791.2A，和M9矮星，LP 944-20。这两个对象的时间序列光谱揭示了许多线轮廓扭曲的旋转周期的每个星星，我们解释为星点。瞬态失真的模拟与点/光球对比度比，对应于模型大气温度差T phot-T spot？> = 300和200 K。GJ 791.2 A是一颗完全对流的星星，v sin i = 35.1 km s−1。虽然我们在高纬度地区发现了更多的星点结构，但我们重建了一系列相位和纬度的星点，平均星点填充率为1.3%。LP 944-20是已知最明亮的晚M矮星之一，光谱类型为M9 V，v sin i = 30.8 km s−1。它的光谱时间序列表现出两个占主导地位的瞬态线失真，重建为高纬度的斑点，而平均点填充因子只有1.5%found.The低对比度斑点的发生主要是在高纬度地区，我们看到在这里的两个目标，是，在一般情况下，可能是负责低振幅光度变化看到晚M矮星。对于GJ 791.2A，由星点特征引起的径向速度产生了138 m s−1的均方根速度变化，使用我们重建的表面亮度分布可以减少1.9倍。
Since M4.5–M9 dwarfs exhibit equatorial rotation velocities of the order of 10 km s−1 on average, radial velocity surveys targeting this stellar population will likely need to find methods to effectively remove starspot jitter. We present the first high resolution Doppler images of the M4.5 dwarf, GJ 791.2A, and the M9 dwarf, LP 944-20. The time series spectra of both objects reveal numerous line profile distortions over the rotation period of each star, which we interpret as starspots. The transient distortions are modeled with spot/photosphere contrast ratios that correspond to model atmosphere temperature differences of T phot − T spot ?> = 300 and 200 K. GJ 791.2A is a fully convective star with v sin i = 35.1 km s−1. Although we find more starspot structure at high latitudes, we reconstruct spots at a range of phases and latitudes with a mean spot filling of ∼3%. LP 944-20 is one of the brightest known late-M dwarfs, with spectral type M9V and v sin i = 30.8 km s−1. Its spectral time series exhibits two dominant transient line distortions that are reconstructed as high latitude spots, while a mean spot filling factor of only 1.5% is found. The occurrence of low-contrast spots at predominantly high latitudes, which we see in both targets here, is, in general, likely to be responsible for the low amplitude photometric variability seen in late-M dwarfs. For GJ 791.2A, the radial velocities induced by the starspot features yield an rms velocity variability of 138 m s−1, which can be reduced by a factor of 1.9 using our reconstructed surface brightness distributions.