A Search for Polarized Thermal Emission from Directly Imaged Exoplanets and Brown Dwarf Companions to Nearby Stars
A Search for Polarized Thermal Emission from Directly Imaged Exoplanets and Brown Dwarf Companions to Nearby Stars
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DOI：
10.3847/1538-3881/abc33d
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发表时间：
2020-11
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通讯作者：
R. Jensen-Clem;M. Millar-Blanchaer;R. G. van Holstein;D. Mawet;J. Graham;S. Sengupta;M. Marley;F. Snik;A. Vigan;S. Hinkley;J. D. Boer;Julien H. Girard;R. D. de Rosa;B. Bowler;S. Wiktorowicz;M. Perrin;J. Crepp;B. Macintosh
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作者：
R. Jensen-Clem;M. Millar-Blanchaer;R. G. van Holstein;D. Mawet;J. Graham;S. Sengupta;M. Marley;F. Snik;A. Vigan;S. Hinkley;J. D. Boer;Julien H. Girard;R. D. de Rosa;B. Bowler;S. Wiktorowicz;M. Perrin;J. Crepp;B. Macintosh
云状气态巨型系外行星和褐矮星大气中的气溶胶会散射和极化这些物体的热发射。如果这样的物体具有扁圆形或不均匀的云分布，则线性偏振的净度可以显示出从百分之几到百分之几的增加。现代高对比度成像偏振计现在已经准备好检测这种低偏振信号，为了解附近恒星的亚恒星伴星的旋转速度和云特性打开了一个新窗口。在本文中，我们介绍了使用 GPI 和 SPHERE-IRDIS 从两个行星质量伴星和五个褐矮星伴星样本中寻找线性偏振热发射的近红外调查结果。我们探索了代表偏振自由漂浮棕矮星的亚线性偏振状态，并对每个物体的线性偏振程度进行了限制。我们将每个目标的线性偏振度的上限与其旋转速率联系起来，并将我们的结果置于使用高分辨率光谱测量的旋转速率的背景下。
Aerosols in the atmospheres of cloudy gas giant exoplanets and brown dwarfs scatter and polarize these objects’ thermal emission. If such an object has an oblate shape or nonuniform cloud distribution, the net degree of linear polarization can show an increase ranging from several tenths of a percent to a few percent. Modern high-contrast imaging polarimeters are now poised to detect such low-polarization signals, opening up a new window into the rotational velocities and cloud properties of substellar companions to nearby stars. In this paper, we present the results of a near-IR survey searching for linearly polarized thermal emission from a sample of two planetary-mass companions and five brown dwarf companions using GPI and SPHERE-IRDIS. We probe the subpercent linear polarization regime that typifies polarized free-floating brown dwarfs and place limits on each object’s degree of linear polarization. We relate our upper limits on each target’s degree of linear polarization to its rotation rate, and place our results in the context of rotation rates measured using high-resolution spectroscopy.