How to Constrain Your M Dwarf: Measuring Effective Temperature, Bolometric Luminosity, Mass, and Radius
Abstract
Precise and accurate parameters for latetype (late K and M) dwarf stars are important for characterization of any orbiting planets, but such determinations have been hampered by these stars’ complex spectra and dissimilarity to the Sun. We exploit an empirically calibrated method to estimate spectroscopic effective temperature (T_{eff}) and the StefanBoltzmann law to determine radii of 183 nearby K7M7 single stars with a precision of 2%5%. Our improved stellar parameters enable us to develop modelindependent relations between T_{eff} or absolute magnitude and radius, as well as between color and T_{eff}. The derived T_{eff}radius relation depends strongly on [Fe/H], as predicted by theory. The relation between absolute K_{S} magnitude and radius can predict radii accurate to ≃ 3%. We derive bolometric corrections to the V{{R}_{C}}{{I}_{C}}grizJH{{K}_{S}} and Gaia passbands as a function of color, accurate to 1%3%. We confront the reliability of predictions from Dartmouth stellar evolution models using a Markov chain Monte Carlo to find the values of unobservable model parameters (mass, age) that best reproduce the observed effective temperature and bolometric flux while satisfying constraints on distance and metallicity as Bayesian priors. With the inferred masses we derive a semiempirical massabsolute magnitude relation with a scatter of 2% in mass. The bestagreement models overpredict stellar T_{eff} values by an average of 2.2% and underpredict stellar radii by 4.6%, similar to differences with values from lowmass eclipsing binaries. These differences are not correlated with metallicity, mass, or indicators of activity, suggesting issues with the underlying model assumptions, e.g., opacities or convective mixing length.
 Publication:

The Astrophysical Journal
 Pub Date:
 May 2015
 DOI:
 10.1088/0004637X/804/1/64
 arXiv:
 arXiv:1501.01635
 Bibcode:
 2015ApJ...804...64M
 Keywords:

 planetary systems;
 stars: abundances;
 stars: fundamental parameters;
 stars: latetype;
 stars: lowmass;
 stars: statistics;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 36 pages, 23 figures, 7 tables. ApJ in press. Machine readable version of Tables 57 included with ancillary data