From: LARRY KLAES (ljk4_at_msn.com)
Date: Sat Oct 27 2007 - 21:08:29 PDT
The transiting exoplanet host star GJ 436: a test of stellar evolution
models in the lower main sequence, and revised planetary parameters
Authors: Guillermo Torres (Harvard-Smithsonian Center for Astrophysics)
(Submitted on 25 Oct 2007)
Abstract: Knowledge of the stellar parameters for the parent stars of
transiting exoplanets is pre-requisite for establishing the planet
properties themselves, and often relies on stellar evolution models. GJ 436,
which is orbited by a transiting Neptune-mass object, presents a difficult
case because it is an M dwarf. Stellar models in this mass regime are not as
reliable as for higher mass stars, and tend to underestimate the radius.
Here we use constraints from published transit light curve solutions for GJ
436 along with other spectroscopic quantities to show how the models can
still be used to infer the mass and radius accurately, and at the same time
allow the radius discrepancy to be estimated. Similar systems should be
found during the upcoming Kepler mission, and could provide in this way
valuable constraints to stellar evolution models in the lower main sequence.
The stellar mass and radius of GJ 436 are M = 0.452 [-0.012,+0.014] M(Sun)
and R = 0.464 [-0.011,+0.009] R(Sun), and the radius is 10% larger than
predicted by the standard models, in agreement with previous results from
well studied double-lined eclipsing binaries. We obtain an improved planet
mass and radius of M = 23.17 +/- 0.79 M(Earth) and R = 4.22 [-0.10,+0.09]
R(Earth), a density of rho = 1.69 [-0.12,+0.14] g/cm3, and an orbital
semimajor axis of a = 0.02872 +/- 0.00027 AU.
Comments: Accepted for publication in The Astrophysical Journal Letters, 5
pages including figures and tables, in emulateapj format
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0710.4883v1 [astro-ph]
Submission history
From: Guillermo Torres [view email]
[v1] Thu, 25 Oct 2007 15:00:30 GMT (95kb)
http://arxiv.org/abs/0710.4883
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