SPITZER OBSERVATIONS OF GJ 3470 b: A VERY LOW-DENSITY NEPTUNE-SIZE PLANET ORBITING A METAL-RICH M DWARF

• Type: Article in International Scientific Journal
• Date: 2013

Authors

Demory, BO (Author) Other; Torres, G (Author) Other; Neves, V (Author) Other; Rogers, L (Author) Other; Gillon, M (Author) Other; Horch, E (Author) Other; Sullivan, P (Author) Other; Bonfils, X (Author) Other; Delfosse, X (Author) Other; Forveille, T (Author) Other; Lovis, C (Author) Other; Mayor, M (Author) Other; N.C. Santos (Author) FCUP; Seager, S (Author) Other; Smalley, B (Author) Other; Udry, S (Author) Other

Journal

Title: Astrophysical Journal

Vol. 768

Final page: 154

ISSN: 0004-637X

Publisher: American Astronomical Society

Indexing

ISI Web of Knowledge - 28 Citations

Scopus - 28 Citations

Other information

Authenticus ID: P-005-0RZ

DOI: 10.1088/0004-637x/768/2/154

Abstract (EN): We present Spitzer/IRAC 4.5 mu m 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-star = 0.539(-0.043)(+0.047) M-circle dot and a radius of R-star = 0.568(-0.031)(+0.037) R-circle dot. We determine the host star of GJ 3470 b to bemetal-rich, with ametallicity of [Fe/H] = +0.20 +/- 0.10 and an effective temperature of T-eff = 3600 +/- 100 K. The revised stellar parameters yield a planetary radius R-p = 4.83(-0.21)(+0.22) R-circle plus that is 13% larger than the value previously reported in the literature. We find a planetary mass M-p = 13.9(-1.4)(+1.5) M-circle plus that translates to a very low planetary density rho(p) = 0.72(-0.12)(+0.13) g cm(-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.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 9