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Title: THERMAL EVOLUTION AND STRUCTURE MODELS OF THE TRANSITING SUPER-EARTH GJ 1214b

Abstract

The planet GJ 1214b is the second known super-Earth with a measured mass and radius. Orbiting a quiet M star, it receives considerably less mass-loss driving X-ray and UV radiation than CoRoT-7b, so that the interior may be quite dissimilar in composition, including the possibility of a large fraction of water. We model the interior of GJ 1214b assuming a two-layer (envelope+rock core) structure where the envelope material is either H/He, pure water, or a mixture of H/He and H{sub 2}O. Within this framework, we perform models of the thermal evolution and contraction of the planet. We discuss possible compositions that are consistent with M{sub p} = 6.55 M{sub +}, R{sub p} = 2.678 R{sub +}, an age {tau} = 3-10 Gyr, and the irradiation level of the atmosphere. These conditions require that if water exists in the interior, it must remain in a fluid state, with important consequences for magnetic field generation. These conditions also require the atmosphere to have a deep isothermal region extending down to 80-800 bar, depending on composition. Our results bolster the suggestion of a metal-enriched H/He atmosphere for the planet, as we find water-world models that lack an H/He atmosphere to require an implausiblymore » large water-to-rock ratio of more than 6:1. We instead favor an H/He/H{sub 2}O envelope with high water mass fraction ({approx}0.5-0.85), similar to recent models of the deep envelope of Uranus and Neptune. Even with these high water mass fractions in the H/He envelope, generally the bulk composition of the planet can have subsolar water:rock ratios. Dry, water-enriched, and pure water envelope models differ to an observationally significant level in their tidal Love numbers k{sub 2} of, respectively, {approx}0.018, {approx}0.15, and {approx}0.7.« less

Authors:
;  [1]; ;  [2]
  1. Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)
  2. Institut fuer Physik, Universitaet Rostock, D-18051 Rostock (Germany)
Publication Date:
OSTI Identifier:
21576818
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 733; Journal Issue: 1; Other Information: DOI: 10.1088/0004-637X/733/1/2; Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CHEMICAL COMPOSITION; PLANETARY ATMOSPHERES; PLANETS; WATER; ATMOSPHERES; HYDROGEN COMPOUNDS; OXYGEN COMPOUNDS

Citation Formats

Nettelmann, N., Fortney, J. J., Kramm, U., and Redmer, R. THERMAL EVOLUTION AND STRUCTURE MODELS OF THE TRANSITING SUPER-EARTH GJ 1214b. United States: N. p., 2011. Web. doi:10.1088/0004-637X/733/1/2.
Nettelmann, N., Fortney, J. J., Kramm, U., & Redmer, R. THERMAL EVOLUTION AND STRUCTURE MODELS OF THE TRANSITING SUPER-EARTH GJ 1214b. United States. doi:10.1088/0004-637X/733/1/2.
Nettelmann, N., Fortney, J. J., Kramm, U., and Redmer, R. Fri . "THERMAL EVOLUTION AND STRUCTURE MODELS OF THE TRANSITING SUPER-EARTH GJ 1214b". United States. doi:10.1088/0004-637X/733/1/2.
@article{osti_21576818,
title = {THERMAL EVOLUTION AND STRUCTURE MODELS OF THE TRANSITING SUPER-EARTH GJ 1214b},
author = {Nettelmann, N. and Fortney, J. J. and Kramm, U. and Redmer, R.},
abstractNote = {The planet GJ 1214b is the second known super-Earth with a measured mass and radius. Orbiting a quiet M star, it receives considerably less mass-loss driving X-ray and UV radiation than CoRoT-7b, so that the interior may be quite dissimilar in composition, including the possibility of a large fraction of water. We model the interior of GJ 1214b assuming a two-layer (envelope+rock core) structure where the envelope material is either H/He, pure water, or a mixture of H/He and H{sub 2}O. Within this framework, we perform models of the thermal evolution and contraction of the planet. We discuss possible compositions that are consistent with M{sub p} = 6.55 M{sub +}, R{sub p} = 2.678 R{sub +}, an age {tau} = 3-10 Gyr, and the irradiation level of the atmosphere. These conditions require that if water exists in the interior, it must remain in a fluid state, with important consequences for magnetic field generation. These conditions also require the atmosphere to have a deep isothermal region extending down to 80-800 bar, depending on composition. Our results bolster the suggestion of a metal-enriched H/He atmosphere for the planet, as we find water-world models that lack an H/He atmosphere to require an implausibly large water-to-rock ratio of more than 6:1. We instead favor an H/He/H{sub 2}O envelope with high water mass fraction ({approx}0.5-0.85), similar to recent models of the deep envelope of Uranus and Neptune. Even with these high water mass fractions in the H/He envelope, generally the bulk composition of the planet can have subsolar water:rock ratios. Dry, water-enriched, and pure water envelope models differ to an observationally significant level in their tidal Love numbers k{sub 2} of, respectively, {approx}0.018, {approx}0.15, and {approx}0.7.},
doi = {10.1088/0004-637X/733/1/2},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 733,
place = {United States},
year = {2011},
month = {5}
}