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Title: WEATHER ON OTHER WORLDS. II. SURVEY RESULTS: SPOTS ARE UBIQUITOUS ON L AND T DWARFS

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 – K{sub s} colors and surface gravities. We find that 14/23 (61%{sub −20%}{sup +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%{sub −17%}{sup +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%{sub −27%}{sup +20%} of L dwarfs vary by ≥0.2%, and 36%{sub −17%}{sup +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 amore » 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.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [9] ;  [10]
  1. The University of Western Ontario, Department of Physics and Astronomy, 1151 Richmond Avenue, London, ON N6A 3K7 (Canada)
  2. Stony Brook University, Department of Physics and Astronomy, Stony Brook, 100 Nicolls Road, NY 11794-3800 (United States)
  3. The University of Arizona, Department of Astronomy, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)
  4. The University of Arizona, Department of Planetary Sciences and Lunar and Planetary Laboratory, 1629 East University Boulevard, Tucson, AZ 85721 (United States)
  5. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
  6. University of California San Diego, Center for Astrophysics and Space Science, 9500 Gilman Drive, Mail Code 0424, La Jolla, CA 92093 (United States)
  7. NASA Ames Research Center, MS-245-3, Moffett Field, CA 94035 (United States)
  8. Université de Montréal, Département de Physique and Observatoire du Mont Mégantic, C.P. 6128, Succ. Centre-Ville, Montréal, QC, H3C 3J7 (Canada)
  9. Missouri State University, Department of Physics, Astronomy and Materials Science, 901 South National Avenue, Springfield, MO 65897 (United States)
  10. Max-Planck-Institut für Astronomie, Königstuhl 17, 69117, Heidelberg (Germany)
Publication Date:
OSTI Identifier:
22364359
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 799; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; AMPLITUDES; APPROXIMATIONS; COLOR; DIAGRAMS; DWARF STARS; EARTH PLANET; GRAVITATION; MASS; PERIODICITY; PHOTOSPHERE; ROTATION; STARSPOTS; VISIBLE RADIATION; WEATHER