We present empirical relations for determining the amount by which the effective temperatures and radii—and therefore the estimated masses—of low-mass stars and brown dwarfs are altered due to chromospheric activity .
We base our relations on a large set of low-mass stars in the field with H \alpha activity measurements , and on a set of low-mass eclipsing binaries with X-ray activity measurements from which we indirectly infer the H \alpha activity .
Both samples yield consistent relations linking the amount by which an active object ’ s temperature is suppressed , and its radius inflated , to the strength of its H \alpha emission .
These relations are found to approximately preserve bolometric luminosity .
We apply these relations to the peculiar brown-dwarf eclipsing binary 2M0535 - 05 , in which the active , higher-mass brown dwarf has a cooler temperature than its inactive , lower-mass companion .
The relations correctly reproduce the observed temperatures and radii of 2M0535 - 05 after accounting for the H \alpha emission ; 2M0535 - 05 would be in precise agreement with theoretical isochrones were it inactive .
The relations that we present are applicable to brown dwarfs and low-mass stars with masses below 0.8 M _ { \odot } and for which the activity , as measured by the fractional H \alpha luminosity , is in the range -4.6 \lesssim \log L _ { { H } \alpha } / L _ { bol } \lesssim - 3.3 .
We expect these relations to be most useful for correcting radius and mass estimates of low-mass stars and brown dwarfs over their active lifetimes ( few Gyr ) and when the ages or distances ( and therefore luminosities ) are unknown .
We also discuss the implications of this work for improved determinations of young cluster initial mass functions .