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A Case for an Atmosphere on Super-Earth 55 Cancri e

Angelo, Isabel and Hu, Renyu (2017) A Case for an Atmosphere on Super-Earth 55 Cancri e. Astronomical Journal, 154 (6). Art. No. 232. ISSN 1538-3881. https://resolver.caltech.edu/CaltechAUTHORS:20171121-095118435

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Abstract

One of the primary questions when characterizing Earth-sized and super-Earth-sized exoplanets is whether they have a substantial atmosphere like Earth and Venus or a bare-rock surface like Mercury. Phase curves of the planets in thermal emission provide clues to this question, because a substantial atmosphere would transport heat more efficiently than a bare-rock surface. Analyzing phase-curve photometric data around secondary eclipses has previously been used to study energy transport in the atmospheres of hot Jupiters. Here we use phase curve, Spitzer time-series photometry to study the thermal emission properties of the super-Earth exoplanet 55 Cancri e. We utilize a semianalytical framework to fit a physical model to the infrared photometric data at 4.5 μm. The model uses parameters of planetary properties including Bond albedo, heat redistribution efficiency (i.e., ratio between radiative timescale and advective timescale of the atmosphere), and the atmospheric greenhouse factor. The phase curve of 55 Cancri e is dominated by thermal emission with an eastward-shifted hotspot. We determine the heat redistribution efficiency to be 1.47^(+0.30)_(-0.25), which implies that the advective timescale is on the same order as the radiative timescale. This requirement cannot be met by the bare-rock planet scenario because heat transport by currents of molten lava would be too slow. The phase curve thus favors the scenario with a substantial atmosphere. Our constraints on the heat redistribution efficiency translate to an atmospheric pressure of ~1.4 bar. The Spitzer 4.5 μm band is thus a window into the deep atmosphere of the planet 55 Cancri e.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.3847/1538-3881/aa9278DOIArticle
http://iopscience.iop.org/article/10.3847/1538-3881/aa9278/metaPublisherArticle
https://arxiv.org/abs/1710.03342arXivDiscussion Paper
ORCID:
AuthorORCID
Angelo, Isabel0000-0002-9751-2664
Additional Information:© 2017 The American Astronomical Society. Received 2017 August 2; revised 2017 October 6; accepted 2017 October 8; published 2017 November 16. We thank Brice-Olivier Demory for the reduced 55 Cancri e photometric data. This work uses observations taken by the Spitzer telescope operated by staff at the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA, where this research was carried out. Support for IA's work was provided by the Caltech Summer Undergraduate Research Fellowship (SURF) Program.
Funders:
Funding AgencyGrant Number
NASA/JPL/CaltechUNSPECIFIED
Caltech Summer Undergraduate Research Fellowship (SURF)UNSPECIFIED
Subject Keywords:occultations – planets and satellites: atmospheres – planets and satellites: individual (55 Cnc e) – planets and satellites: terrestrial planets – techniques: photometric
Issue or Number:6
Record Number:CaltechAUTHORS:20171121-095118435
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20171121-095118435
Official Citation:Isabel Angelo and Renyu Hu 2017 AJ 154 232
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:83391
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:21 Nov 2017 19:17
Last Modified:03 Oct 2019 19:05

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