Abstract
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 Ha emission; 2M0535-05 would be in precise agreement with theoretical isochrones were it is inactive. The relations that we present are applicable to brown dwarfs and low-mass stars with masses below 0.8 M-circle dot and for which the activity, as measured by the fractional H alpha luminosity, is in the range -4.6 less than or similar to log LH alpha/L-bol less than or similar to -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.
Original language | English |
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Article number | 47 |
Number of pages | 10 |
Journal | Astrophysical Journal |
Volume | 756 |
Issue number | 1 |
DOIs | |
Publication status | Published - 1 Sept 2012 |
Keywords
- MAGNETIC ACTIVITY
- ECLIPSING BINARIES
- ORION NEBULA CLUSTER
- stars: low-mass
- PHYSICAL PARAMETERS
- SKY SURVEY DATA
- H-ALPHA
- AUTOMATED SURVEY CATALOG
- stars: fundamental parameters
- brown dwarfs
- BINARY 2MASS J05352184-0546085
- SIMULTANEOUS MULTIWAVELENGTH OBSERVATIONS
- stars: activity
- SPECTROSCOPIC SURVEY