Low-gravity L Dwarfs Are Likely More Variable
In the Weather on Other Worlds Spitzer Exploration Science program, we surveyed 44 nearby L3-T8 dwarfs for spot-induced rotational variability. Among single L3-L9.5 dwarfs, we found that 80% are variable at >0.2% in the 3-5 μm wavelength range, while 36% of T0-T8 were variable at >0.4%. Taking into account viewing angle and sensitivity considerations, both of these findings are consistent with spots being present on ∼100% of L3-T8 dwarfs. Intriguingly, 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.
Physics, Astronomy, and Materials Science
brown dwarfs, stars: low-mass, stars: starspots, stars: variables: general, stars:rotation, techniques: photometric
Metchev, Stanimir, Aren Heinze, Daniel Apai, Davin Flateau, Jacqueline Radigan, Adam Burgasser, Mark Marley, Étienne Artigau, Peter Plavchan, and Bertrand Goldman. "Low-gravity L Dwarfs Are Likely More Variable." Proceedings of the International Astronomical Union 10, no. S314 (2015): 121-123.
Proceedings of the International Astronomical Union