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arXiv · 0812.1223

Using Magnetic Activity and Galactic Dynamics to Constrain the Ages of M Dwarfs

Andrew A. West·Suzanne L. Hawley·John J. Bochanski·Kevin R. Covey·Adam J. Burgasser
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Abstract

We present a study of the dynamics and magnetic activity of M dwarfs using the largest spectroscopic sample of low-mass stars ever assembled. The age at which strong surface magnetic activity (as traced by H-alpha) ceases in M dwarfs has been inferred to have a strong dependence on mass (spectral type, surface temperature) and explains previous results showing a large increase in the fraction of active stars at later spectral types. Using spectral observations of more than 40000 M dwarfs from the Sloan Digital Sky Survey, we show that the fraction of active stars decreases as a function of vertical distance from the Galactic plane (a statistical proxy for age), and that the magnitude of this decrease changes significantly for different M spectral types. Adopting a simple dynamical model for thin disk vertical heating, we assign an age for the activity decline at each spectral type, and thus determine the activity lifetimes for M dwarfs. In addition, we derive a statistical age-activity relation for each spectral type using the dynamical model, the vertical distance from the Plane and the H-alpha emission line luminosity of each star (the latter of which also decreases with vertical height above the Galactic plane).

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Andrew A. West, Suzanne L. Hawley, John J. Bochanski, Kevin R. Covey, Adam J. Burgasser. 2008-12-05. Using Magnetic Activity and Galactic Dynamics to Constrain the Ages of M Dwarfs. https://doi.org/10.1017/s1743921309031986

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