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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 720096.0, MPI für Astronomie / Publikationen_mpia
Weather on Other Worlds. II. Survey results: Spots are ubiquitous on L and T dwarfs
Authors:Metchev, S. A.; Heinze, A.; Apai, D.; Flateau, D.; Radigan, J.; Burgasser, A.; Marley, M. S.; Artigau, É.; Plavchan, P.; Goldman, B.
Date of Publication (YYYY-MM-DD):2015
Title of Journal:The Astrophysical Journal
Start Page:id. 154 (23 pp)
Audience:Not Specified
Abstract / Description:We present results from the Weather on Other Worlds Spitzer Exploration Science program to investigate photometric variability in L and T dwarfs, usually attributed to patchy clouds. We surveyed 44 L3-T8 dwarfs, spanning a range of J - Ks colors and surface gravities. We find that 14/23 (61%-20%+17%, 95% confidence) of our single L3-L9.5 dwarfs are variable with peak-to-peak amplitudes between 0.2% and 1.5%, and 5/16 (31%-17%+25%) of our single T0-T8 dwarfs are variable with amplitudes between 0.8% and 4.6%. After correcting for sensitivity, we find that 80%-27%+20% of L dwarfs vary by >=0.2%, and 36%-17%+26% of T dwarfs vary by >=0.4%. Given viewing geometry considerations, we conclude that photospheric heterogeneities causing >0.2% 3-5 μm flux variations are present on virtually all L dwarfs, and probably on most T dwarfs. A third of L dwarf variables show irregular light curves, indicating that L dwarfs may have multiple spots that evolve over a single rotation. Also, approximately a third of the periodicities are on timescales >10 hr, suggesting that slowly rotating brown dwarfs may be common. We observe an increase in the maximum amplitudes over the entire spectral type range, revealing a potential for greater temperature contrasts in T dwarfs than in L dwarfs. We find a tentative association (92% confidence) between low surface gravity and high-amplitude variability among L3-L5.5 dwarfs. Although we can not confirm whether lower gravity is also correlated with a higher incidence of variables, the result is promising for the characterization of directly imaged young extrasolar planets through variability.
Free Keywords:brown dwarfs; stars: low-mass; stars: rotation; starspots; stars: variables: general; techniques: photometric
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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