The impact of chromospheric activity on observed initial mass functions

Keivan G. Stassun, Aleks Scholz, Trent J. Dupuy, Kaitlin M. Kratter

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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
Original languageEnglish
Article number119
Number of pages5
JournalAstrophysical Journal
Issue number2
Early online date13 Nov 2014
Publication statusPublished - 1 Dec 2014


  • brown dwarfs
  • stars: activity
  • stars: fundamental parameters
  • stars: low-mass
  • stars: luminosity function
  • mass function


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