POSTER PAPER 2.10
Rotation & Activity in Mid-M to L Dwarfs
Subhanjoy Mohanty, Gibor Basri
Institute: Astronomy Department, University of California, Berkeley
Contact Email: subu@astron.berkeley.edu
Abstract:
We analyze rotation velocities and chromospheric H-alpha activity, derived from multi-year, high-resolution spectra, in 56 mid-M to L dwarfs. Rotation velocities are found to increase from mid-M to L. This is consistent with a lengthening of spin-down timescale with later type, though in the L types the trend may also be a function of stellar age. From M5 to M8.5, a saturation-type rotation-activity relation is seen, similar to that in earlier types. However, the saturation velocity in our case is much higher, at ~12 km/s. A sharp drop in activity is observed at ~M9, with later types showing little or no H-alpha emission, in spite of rapid rotation. This may be due to the very high resistivities in the predominantly neutral atmospheres of these cool objects.
Index Keywords: Rotation Velocity; Chromospheric Activity; M Dwarfs; L Dwarfs
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Manuscript submitted: 2001-Sep-20
"The Future of Cool-Star Astrophysics", 2003, Eds. A. Brown,
G. M. Harper, & T. R. Ayres.
Proceedings of 12th Cambridge Workshop on Cool Stars, Stellar Systems,
& The Sun,
© 2003 University of Colorado.