Weather on Other Worlds. IV. Hα Emission and Photometric Variability Are Not Correlated in L0–T8 Dwarfs
Weather on Other Worlds. IV. Hα Emission and Photometric Variability Are Not Correlated in L0–T8 Dwarfs
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L0-T8 矮星中的 Hα 发射和光度变化不相关。
DOI：
10.3847/1538-4357/aa6f11
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
D. Apai
中科院分区：
文献类型：
--
作者：
P. Miles;S. Metchev;A. Heinze;D. Apai
最近的光度学研究表明，几乎所有的L矮星和T矮星上都存在产生通量变化的表面黑子。它们可能的磁性或尘埃性质一直是一个备受争议的问题，由于缺乏诊断性的多波长观测，这一问题的解决受到了阻碍。为了检验磁活动和光度变率之间的相关性，我们在8颗L3-T2超冷矮星中搜索了Hα辐射，其中一些已知在3.6μm或4.5μm变化，我们只在不变的T2矮星2MASS J12545393α0122474中检测到H−辐射。剩下的七个天体没有显示Hα发射，尽管其中六个已知会在光度学上发生变化。将我们的结果与其他86颗L矮星和T矮星的结果相结合，结果表明，在L0到L3.5之间的光谱类型中，Hα辐射的检测率很高(94%)，而在≥L4光谱类型中的检测率要小得多(20%)，而光度变化的检测率在L0到T8矮星之间几乎是恒定的(30%-55%)。我们得出的结论是，由Hα发射所证明的色球活动与大幅度光度变率并不相关。因此，尘埃云是观测到的光谱类型超冷矮星变化的主要驱动因素，至少早在L0就是如此。
Recent photometric studies have revealed that surface spots that produce flux variations are present on virtually all L and T dwarfs. Their likely magnetic or dusty nature has been a much-debated problem, the resolution to which has been hindered by paucity of diagnostic multi-wavelength observations. To test for a correlation between magnetic activity and photometric variability, we searched for Hα emission among eight L3–T2 ultra-cool dwarfs with extensive previous photometric monitoring, some of which are known to be variable at 3.6 μm or 4.5 μm. We detected Hα only in the non-variable T2 dwarf 2MASS J12545393−0122474. The remaining seven objects do not show Hα emission, even though six of them are known to vary photometrically. Combining our results with those for 86 other L and T dwarfs from the literature show that the detection rate of Hα emission is very high (94%) for spectral types between L0 and L3.5 and much smaller (20%) for spectral types ≥L4, while the detection rate of photometric variability is approximately constant (30%–55%) from L0 to T8 dwarfs. We conclude that chromospheric activity, as evidenced by Hα emission, and large-amplitude photometric variability are not correlated. Consequently, dust clouds are the dominant driver of the observed variability of ultra-cool dwarfs at spectral types, at least as early as L0.
影响因子：
64.8
作者：
G. Hallinan;S. P. Littlefair;G. Cotter;S. Bourke;L. K. Harding;J. Pineda;R. P. Butler;A. Golden;G. Basri;J. Doyle;M. Kao;S. Berdyugina;A. Kuznetsov;M. Rupen;A. Antonova
通讯作者：
G. Hallinan;S. P. Littlefair;G. Cotter;S. Bourke;L. K. Harding;J. Pineda;R. P. Butler;A. Golden;G. Basri;J. Doyle;M. Kao;S. Berdyugina;A. Kuznetsov;M. Rupen;A. Antonova