Cloud Atlas: Variability in and out of the Water Band in the Planetary-mass HD 203030B Points to Cloud Sedimentation in Low-gravity L Dwarfs
Cloud Atlas: Variability in and out of the Water Band in the Planetary-mass HD 203030B Points to Cloud Sedimentation in Low-gravity L Dwarfs
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云图：行星质量 HD 203030B 水带内外的变化表明低重力 L 矮星存在云沉积
DOI：
10.3847/1538-4357/ab3d25
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
G. Schneider
中科院分区：
文献类型：
--
作者：
P. Miles;S. Metchev;D. Apai;Yifan Zhou;E. Manjavacas;T. Karalidi;Ben W. P. Lew;A. Burgasser;L. Bedin;N. Cowan;P. Lowrance;M. Marley;Jacqueline Radigan;G. Schneider
我们使用哈勃太空望远镜上的宽视场相机3对年轻的L7.5伴侣HD 203030 B进行了测量。我们的时间序列揭示了与旋转兼容的时间尺度上1.27和1.39 μm处的光度变化。我们发现一个旋转周期小时：与其他棕矮星和行星质量的同伴观察到的年龄小于3亿年。我们测量到的光变幅度为1.1% ± 0.3%（1.27 μm）和1.7% ± 0.4%（1.39 μm），两条光变曲线之间的相位滞后为56° ± 28°。我们将光度振幅和相位的差异归因于一个片状云层，该云层正在下沉到水蒸气变得不透明的水平以下。HD 203030 B和其他几颗已知的年轻的晚L型变星不像较温暖的（较早型和/或较老的）L型变星，后者在1.1-1.7 μm区域的变化对波长的依赖性要小得多。我们进一步认为，最顶层的云甲板下沉到水或一氧化碳气体变得不透明的水平以下，也可以解释更早类型的低重力L型矮星经常增强的变化幅度。因为这些凝析油和气体不透明度水平在T矮星中已经很好地分化，我们不期望在年轻的T矮星与老的T矮星中有相同的变化幅度增强。
We use the Wide Field Camera 3 on the Hubble Space Telescope to spectrophotometrically monitor the young L7.5 companion HD 203030B. Our time series reveal photometric variability at 1.27 and 1.39 μm on timescales compatible with rotation. We find a rotation period of hr: comparable to those observed in other brown dwarfs and planetary-mass companions younger than 300 Myr. We measure variability amplitudes of 1.1% ± 0.3% (1.27 μm) and 1.7% ± 0.4% (1.39 μm), and a phase lag of 56° ± 28° between the two light curves. We attribute the difference in photometric amplitudes and phases to a patchy cloud layer that is sinking below the level where water vapor becomes opaque. HD 203030B and the few other known variable young late-L dwarfs are unlike warmer (earlier-type and/or older) L dwarfs, for which variability is much less wavelength-dependent across the 1.1–1.7 μm region. We further suggest that a sinking of the top-most cloud deck below the level where water or carbon monoxide gas become opaque may also explain the often enhanced variability amplitudes of even earlier-type low-gravity L dwarfs. Because these condensate and gas opacity levels are already well-differentiated in T dwarfs, we do not expect the same variability amplitude enhancement in young versus old T dwarfs.
影响因子：
6.5
作者：
Baraffe, Isabelle;Homeier, Derek;Chabrier, Gilles
通讯作者：
Chabrier, Gilles