Evolutionary Models for Ultracool Dwarfs

Catarina S. Fernandes

doi:10.3847/1538-4357/ab2333

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Evolutionary Models for Ultracool Dwarfs

2019-07-10

Catarina S. Fernandes *

V. Van Grootel

Salmon, Sebastian J. A. J.

DOI：10.3847/1538-4357/ab2333

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Abstract

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Ultracool dwarfs (UCDs) have emerged as key targets for searches of transiting exoplanets. Precise estimates of the host parameters (including mass, age, and radius) are fundamental to constraining the physical properties of orbiting exoplanets. We have extended our evolutionary code Code Liegeois d'Evolution Stellaire to the UCD regime. We include relevant equations of state (EOSs) for H, He, as well as C and O elements to cover the temperature-density regime of UCD interiors. For various metallicities, we couple the interior models to two sets of model atmospheres as surface boundary conditions. We show that including C and O in the EOS has a significant effect close to the H-burning limit mass. The typical systematic error associated with uncertainties in input physics in evolutionary models is similar to 0.0005 M-circle dot. We test model results against observations for objects whose parameters have been determined from independent techniques. We are able to reproduce dynamical mass measurements of LSPM J1314+1320AB within 1 sigma with the condition of varying the metallicity (determined from calibrations) up to 2.5 sigma. For GJ 65AB, a 2 sigma agreement is obtained between individual masses from differential astrometry and those from evolutionary models. We provide tables of UCD models for various masses and metallicities that can be used as reference when estimating parameters for ultracool objects.

Keywords:

stars: late-type

stars: low-mass

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