2001/01/22 by C. A. L. Bailer-Jones, C. A. L. Bailer‐Jones, Bailer-Jones, C. A. L.
Physics and Astronomy · #Astro and Planetary Science #Astrophysics (astro-ph) #Astrophysics and Star Formation Studies #FOS: Physical sciences #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0101372
To appear in "Ultracool Dwarf Stars" (Lecture Notes in Physics), H.R.A. Jones, I. Steele (eds), Springer-Verlag, 2001. Also available from http://www.mpia-hd.mpg.de/homes/calj/ultra.html
arxiv created 2001/01/22 · openalex publication_date 2001/01/22 · arxiv updated 2009/12/01 · openalex created_date 2022/10/01 · openalex updated_date 2026/07/28
Photometric I band light curves of 21 ultra cool M and L dwarfs are\npresented. Variability with amplitudes of 0.01 to 0.055 magnitudes (RMS) with\ntypical timescales of an hour to several hours are discovered in half of these\nobjects. Periodic variability is discovered in a few cases, but interestingly\nseveral variable objects show no significant periods, even though the\nobservations were almost certainly sensitive to the expected rotation periods.\nIt is argued that in these cases the variability is due to the evolution of the\nsurface features on timescales of a few hours. This is supported in the case of\n2M1145 for which no common period is found in two separate light curves. It is\nspeculated that these features are photospheric dust clouds, with their\nevolution possibly driven by rotation and turbulence. An alternative\npossibility is magnetically-induced surface features. However, chromospheric\nactivity undergoes a sharp decrease between M7 and L1, whereas a greater\noccurrence of variability is observed in objects later than M9, lending support\nto the dust interpretation.\n