We have examined the relationship between rotation and activity in 14 late-type (M6-M7) M dwarfs, using high resolution spectra taken at the Keck Observatory and flux-calibrated spectra from the Sloan Digital Sky Survey. Most are inactive at a spectral type where H-alpha emission has previously seen to be very common. We used the cross-correlation technique to quantify the rotational broadening; six of the stars in our sample have vsini>3.5 km/s. Three of these stars do not exhibit H-alpha emission, despite rotating at velocities where previous work has observed strong levels of magnetic field and stellar activity. Our results suggest that rotation and activity in late-type M dwarfs may not always be linked, and open several additional possibilities including a rotation dependant activity threshold, or a Maunder-minimum phenomenon in fully convective stars.
@article{arxiv.0810.0061,
title = {Rotation and Activity in Late-type M Dwarfs},
author = {Andrew A. West and Gibor Basri},
journal= {arXiv preprint arXiv:0810.0061},
year = {2009}
}
Comments
4 pages, 2 figures, to appear in proceedings of Cool Stars 15