Article (Scientific journals)
Spitzer Observations of GJ3470b: a Very Low-density Neptune-size Planet Orbiting a Metal-rich M dwarf
Demory, Brice-Olivier; Torres, Guillermo; Neves, Vasco et al.
2013In Astrophysical Journal
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Keywords :
Astrophysics - Earth and Planetary Astrophysics
Abstract :
[en] We present Spitzer/IRAC 4.5-micron transit photometry of GJ3470b, a Neptune-size planet orbiting a M1.5 dwarf star with a 3.3-day period recently discovered in the course of the HARPS M-dwarf survey. We refine the stellar parameters by employing purely empirical mass-luminosity and surface brightness relations constrained by our updated value for the mean stellar density, and additional information from new near-infrared spectroscopic observations. We derive a stellar mass of M_star = 0.539+0.047-0.043 M_sun and a radius of R_star = 0.568+0.037-0.031 R_sun. We determine the host star of GJ3470b to be metal-rich, with a metallicity of [Fe/H] = +0.20 +/- 0.10 and an effective temperature of Teff = 3600 +/- 100 K. The revised stellar parameters yield a planetary radius R_pl = 4.83+0.22-0.21 R_Earth that is 13 percent larger than the value previously reported in the literature. We find a planetary mass M_pl = 13.9+1.5-1.4 M_Earth that translates to a very low planetary density, rho_pl = 0.72+0.13-0.12 gcm-3, which is 33% smaller than the original value. With a mean density half of that of GJ436b, GJ3470b is an example of a very low-density low-mass planet, similar to Kepler-11d, Kepler-11e, and Kepler-18c but orbiting a much brighter nearby star that is more conducive to follow-up studies.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Demory, Brice-Olivier
Torres, Guillermo
Neves, Vasco
Rogers, Leslie
Gillon, Michaël  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique et traitement de l'image
Horch, Elliott
Sullivan, Peter
Bonfils, Xavier
Delfosse, Xavier
Forveille, Thierry
Lovis, Christophe
Mayor, Michel
Santos, Nuno
Seager, Sara
Smalley, Barry
Udry, Stephane
More authors (6 more) Less
Language :
English
Title :
Spitzer Observations of GJ3470b: a Very Low-density Neptune-size Planet Orbiting a Metal-rich M dwarf
Publication date :
01 January 2013
Journal title :
Astrophysical Journal
ISSN :
0004-637X
eISSN :
1538-4357
Publisher :
IOP Publishing, Bristol, United Kingdom
Peer reviewed :
Peer Reviewed verified by ORBi
Commentary :
9 pages, 6 figures, submitted to ApJ
eprintid: arXiv:1301.6555
Available on ORBi :
since 04 February 2013

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