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The Densities of Planets in Multiple Stellar Systems

Furlan, E. and Howell, S. B. (2017) The Densities of Planets in Multiple Stellar Systems. Astronomical Journal, 154 (2). Art. No. 66. ISSN 1538-3881. doi:10.3847/1538-3881/aa7b70.

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We analyze the effect of companion stars on the bulk density of 29 planets orbiting 15 stars in the Kepler field. These stars have at least one stellar companion within 2'', and the planets have measured masses and radii, allowing an estimate of their bulk density. The transit dilution by the companion star requires the planet radii to be revised upward, even if the planet orbits the primary star; as a consequence, the planetary bulk density decreases. We find that if planets orbited a faint companion star, they would be more volatile-rich, and in several cases their densities would become unrealistically low, requiring large, inflated atmospheres or unusually large mass fractions in an H/He envelope. In addition, for planets detected in radial velocity data, the primary star has to be the host. We can exclude 14 planets from orbiting the companion star; the remaining 15 planets in seven planetary systems could orbit either the primary or the secondary star, and for five of these planets the decrease in density would be substantial even if they orbited the primary, since the companion is of almost equal brightness as the primary. Substantial follow-up work is required in order to accurately determine the radii of transiting planets. Of particular interest are small, rocky planets that may be habitable; a lower mean density might imply a more volatile-rich composition. Reliable radii, masses, and thus bulk densities will allow us to identify which small planets are truly Earth-like.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Furlan, E.0000-0001-9800-6248
Howell, S. B.0000-0002-2532-2853
Additional Information:© 2017 The American Astronomical Society. Received 2017 April 13; revised 2017 June 19; accepted 2017 June 21; published 2017 July 24. We thank our referee for useful suggestions that improved the presentation and clarity of the paper. Support for this work was provided by NASA through awards issued by JPL/Caltech. This research has made use of the NASA Exoplanet Archive and the Exoplanet Follow-up Observation Program website, which are operated by the California Institute of Technology, under contract with NASA under the Exoplanet Exploration Program. It has also made use of NASA's Astrophysics Data System Bibliographic Services.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Subject Keywords:binaries: general — planets and satellites: composition — planets and satellites: fundamental parameters
Issue or Number:2
Record Number:CaltechAUTHORS:20170712-092903444
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Official Citation:E. Furlan and S. B. Howell 2017 AJ 154 66
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:79002
Deposited By: Tony Diaz
Deposited On:12 Jul 2017 17:03
Last Modified:15 Nov 2021 17:44

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