We describe a new, distance-independent method for calculating the magnetic activity strength in low mass dwarfs, L_{H\alpha}/L_{bol}. Using a well-observed sample of nearby stars and cool standards spanning spectral type M0.5 to L0, we compute ``\chi'', the ratio between the continuum flux near H-alpha and the bolometric flux, f_{\lambda6560}/f_{bol}. This ratio may be multiplied by the measured equivalent width of the H-alpha emission line to yield L_{H\alpha}/L_{bol}. We provide \chi values for all objects in our sample, as well as fits to \chi as a function of color and average values by spectral type. This method was used by West et al.(2004) to examine trends in magnetic activity strength in low mass stars.
@article{arxiv.astro-ph/0410422,
title = {The \chi Factor: Determining the Strength of Activity in Low Mass Dwarfs},
author = {Lucianne M. Walkowicz and Suzanne L. Hawley and Andrew A. West},
journal= {arXiv preprint arXiv:astro-ph/0410422},
year = {2009}
}
Comments
11 pages, 5 figures. Accepted for publication in PASP