Stellar Parameters for Trappist-1

DOI
Publisher DOI
Abstract
TRAPPIST-1 is an ultracool dwarf star transited by seven Earth-sized planets, for which thorough characterization of atmospheric properties, surface conditions encompassing habitability, and internal compositions is possible with current and next-generation telescopes. Accurate modeling of the star is essential to achieve this goal. We aim to obtain updated stellar parameters for TRAPPIST-1 based on new measurements and evolutionary models, compared to those used in discovery studies. We present a new measurement for the parallax of TRAPPIST-1, 82.4 ± 0.8 mas, based on 188 epochs of observations with the TRAPPIST and Liverpool Telescopes from 2013 to 2016. This revised parallax yields an updated luminosity of L ͙=(5.22 ± 0.19) x 10⁻⁴ Lʘ, which is very close to the previous estimate but almost two times more precise. We next present an updated estimate for TRAPPIST-1 stellar mass, based on two approaches: mass from stellar evolution modeling, and empirical mass derived from dynamical masses of equivalently classified ultracool dwarfs in astrometric binaries. We combine them using a Monte-Carlo approach to derive a semi-empirical estimate for the mass of TRAPPIST-1. We also derive estimate for the radius by combining this mass with stellar density inferred from transits, as well as an estimate for the effective temperature from our revised luminosity and radius. Our final results are M ͙= 0.089 ± 0.006 Mʘ, R ͙ =0.121 ± 0.003 Rʘ , and Teff= 2516 ± 41 K. Considering the degree to which the TRAPPIST-1 system will be scrutinized in coming years, these revised and more precise stellar parameters should be considered when assessing the properties of TRAPPIST-1 planets.
Date Issued
2018-01
Publication Type
Article
Subject(s)
Language(s)
en
Author(s)
Grootel, Valérie Van
Fernandes, Catarina S.
Gillon, Michael
Jehin, Emmanuel
Manfroid, Jean
Scuflaire, Richard
Burgasser, Adam J.
Barkaoui, Khalid
Benkhaldoun, Zouhair
Burdanov, Artem
Delrez, Laetitia
Wit, Julien de
Queloz, Didier
Triaud, Amaury H. M. J.
Additional Credits
Journal
Astrophysical journal
Publisher
Institute of Physics Publishing IOP
ISSN
0004-637X
Access(Rights)
open.access
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