SPITZER OBSERVATIONS OF GJ 3470 b: A VERY LOW-DENSITY NEPTUNE-SIZE PLANET ORBITING A METAL-RICH M DWARF
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Seager_Spitzer observations.pdf
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Author(s)
Demory, Brice-Olivier
Torres, Guillermo
Neves, Vasco
Rogers, Leslie
Gillon, M.
Horch, Elliott P.
Bonfils, Xavier
Delfosse, Xavier
Forveille, Thierry
Lovis, Christophe
Date Issued
April 2013
Journal
The Astrophysical Journal
Publisher
IOP Publishing
Citation
Demory, Brice-Olivier, Guillermo Torres, Vasco Neves, Leslie Rogers, Michael Gillon, Elliott Horch, Peter Sullivan, et al. “ SPITZER OBSERVATIONS OF GJ 3470 B: A VERY LOW-DENSITY NEPTUNE-SIZE PLANET ORBITING A METAL-RICH M DWARF .” The Astrophysical Journal 768, no. 2 (May 10, 2013): 154.
Version
Author's final manuscript
Abstract
We present Spitzer/IRAC 4.5 μm transit photometry of GJ 3470 b, a Neptune-size planet orbiting an 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[subscript *] = 0.539[+0.047 over -0.043] M[subscript ʘ] and a radius of R[subscript *] = 0.568[+0.037 over -0.031] R[subscript ʘ]. We determine the host star of GJ 3470 b to be metal-rich, with a metallicity of [Fe/H] = +0.20 ± 0.10 and an effective temperature of T [subscript eff] = 3600 ± 100 K. The revised stellar parameters yield a planetary radius Rsubscript p] = 4.83[-0.21 over +0.22] R[subscript ⊕] that is 13% larger than the value previously reported in the literature. We find a planetary mass M[subscript p] = 13.9[+1.5 over -1.4] M[subscript ⊕] that translates to a very low planetary density, P[subscript p] = 0.72[+0.13 over -0.12] g cm[superscript –3], which is 33% smaller than the original value. With a mean density half of that of GJ 436 b, GJ 3470 b is an example of a very low-density low-mass planet, similar to Kepler-11 d, Kepler-11 e, and Kepler-18 c, but orbiting a much brighter nearby star that is more conducive to follow-up studies.
Description
Author's final manuscript: March 7, 2013
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
Massachusetts Institute of Technology. Department of Physics
MIT Kavli Institute for Astrophysics and Space Research
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Creative Commons Attribution-Noncommercial-Share Alike
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DOI of Published Version
https://doi.org/10.1088/0004-637x/768/2/154
