Abstract
Using recently established empirical calibrations for the impact of chromospheric activity on the radii, effective temperatures, and estimated masses of active low-mass stars and brown dwarfs, we reassess the shape of the initial mass function (IMF) across the stellar/substellar boundary in the Upper Sco star-forming region (age 5-10 Myr). We adjust the observed effective temperatures to warmer values using the observed strength of the chromospheric Hα emission, and redetermine the estimated masses of objects using pre-main-sequence evolutionary tracks in the H-R diagram. The effect of the activity-adjusted temperatures is to shift the objects to higher masses by 3%-100%. While the slope of the resulting IMF at substellar masses is not strongly changed, the peak of the IMF does shift from 0.06 to 0.11 M . Moreover, for objects with masses ≲ 0.2 M , the ratio of brown dwarfs to stars changes from 80% to 33%. These results suggest that activity corrections are essential for studies of the substellar mass function, if the masses are estimated from spectral types or from effective temperatures.
Original language | English (US) |
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Article number | 119 |
Journal | Astrophysical Journal |
Volume | 796 |
Issue number | 2 |
DOIs | |
State | Published - Dec 1 2014 |
Keywords
- Brown dwarfs
- Stars: activity
- Stars: fundamental parameters
- Stars: low-mass
- Stars: luminosity function, mass function
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science