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Evolutionary Analysis of Gaseous Sub-Neptune-mass Planets with MESA

Chen, Howard and Rogers, Leslie A. (2016) Evolutionary Analysis of Gaseous Sub-Neptune-mass Planets with MESA. Astrophysical Journal, 831 (2). Art. No. 180. ISSN 0004-637X. doi:10.3847/0004-637X/831/2/180.

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Sub-Neptune-sized exoplanets represent the most common types of planets in the Milky Way, yet many of their properties are unknown. Here, we present a prescription to adapt the capabilities of the stellar evolution toolkit Modules for Experiments in Stellar Astrophysics to model sub-Neptune-mass planets with H/He envelopes. With the addition of routines treating the planet core luminosity, heavy-element enrichment, atmospheric boundary condition, and mass-loss due to hydrodynamic winds, the evolutionary pathways of planets with diverse starting conditions are more accurately constrained. Using these dynamical models, we construct mass-composition relationships of planets from 1-400 M⊕ and investigate how mass-loss impacts their composition and evolution history. We demonstrate that planet radii are typically insensitive to the evolution pathway that brought the planet to its instantaneous mass, composition and age, with variations from hysteresis ≾2%. We find that planet envelope mass-loss timescales, τ_(env), vary non-monotonically with H/He envelope mass fractions (at fixed planet mass). In our simulations of young (100 Myr) low-mass (M_p ≾ 10M⊕) planets with rocky cores, τ_(env) is maximized at M_(env)/M_p = 1% to 3%. The resulting convergent mass-loss evolution could potentially imprint itself on the close-in planet population as a preferred H/He mass fraction of ~1%. Looking ahead, we anticipate that this numerical code will see widespread applications complementing both 3D models and observational exoplanet surveys.

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URLURL TypeDescription Paper
Rogers, Leslie A.0000-0003-0638-3455
Additional Information:© 2016 American Astronomical Society. Received 2015 August 29; revised 2016 August 26; accepted 2016 August 29; published 2016 November 7. We thank Dr. James Owen for assisting us with the atmospheric boundary conditions and Prof. Phil Arras for providing us with helpful templates that enhanced the efficiency of simulating MESA planets. We also thank Dr. Eric Lopez for great suggestions for our manuscript. H.C. acknowledges the Undergraduate Research Opportunities Program (UROP) at Boston University for funding this research, while he was in residence at Caltech during the summer of 2014 and throughout the academic year. The authors thank Professors Philip Muirhead and Heather Knutson for facilitating the summer research. L.A.R. gratefully acknowledges support provided by NASA through the Hubble Fellowship Grant #HF-51313 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. This work was performed in part under contract with the Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. Most of the calculations have made use of H.C.'s MSI GE70 APACHE laptop, which was supported by his parents to pursue his interest in computational astrophysics and planetary science. In conclusion, we express our gratitude to the MESA code creators, Dr. Bill Paxton, and Professors Lars Bildsten and Frank Timmes, without whom this project would not have been possible.
Funding AgencyGrant Number
Boston UniversityUNSPECIFIED
NASA Hubble FellowshipHF-51313
NASANAS 5-26555
Caltech Summer Undergraduate Research Fellowship (SURF)UNSPECIFIED
Subject Keywords:methods: numerical – planets and satellites: atmospheres – planets and satellites: interiors – planets and satellites: physical evolution
Issue or Number:2
Record Number:CaltechAUTHORS:20161107-115319620
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Official Citation:Howard Chen and Leslie A. Rogers 2016 ApJ 831 180
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:71772
Deposited By: Tony Diaz
Deposited On:07 Nov 2016 20:27
Last Modified:11 Nov 2021 04:50

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