Weather on Other Worlds. IV. H alpha Emission and Photometric Variability Are Not Correlated in L0-T8 Dwarfs
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Univ Arizona, Dept AstronUniv Arizona, Lunar & Planetary Lab
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2017-05-10
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Weather on Other Worlds. IV. H alpha Emission and Photometric Variability Are Not Correlated in L0-T8 Dwarfs 2017, 840 (2):83 The Astrophysical JournalJournal
The Astrophysical JournalRights
© 2017. The American Astronomical Society. All rights reserved.Collection Information
This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.Abstract
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 Ha emission among eight L3-T2 ultra-cool dwarfs with extensive previous photometric monitoring, some of which are known to be variable at 3.6 mu m or 4.5 mu m. We detected Ha only in the non-variable T2 dwarf 2MASS J12545393-0122474. The remaining seven objects do not show Ha 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 Ha 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 H alpha 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.ISSN
1538-4357Version
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http://stacks.iop.org/0004-637X/840/i=2/a=83?key=crossref.d613b951baff2c62381cae704a80551aae974a485f413a2113503eed53cd6c53
10.3847/1538-4357/aa6f11