Exoplanet characterization by proxy: a transiting 2.15 R⊕ planet near the habitable zone of the late K dwarf Kepler-61

Ballard, Sarah and Charbonneau, David and Fressin, Francois and Torres, Guillermo and Irwin, Jonathan and Desert, Jean Michel and Newton, Elisabeth and Mann, Andrew W. and Ciardi, David R. and Crepp, Justin R. and Henze, Christopher E. and Bryson, Stephen T. and Howell, Steven B. and Horch, Elliott P. and Everett, Mark E. and Shporer, Avi (2013) Exoplanet characterization by proxy: a transiting 2.15 R⊕ planet near the habitable zone of the late K dwarf Kepler-61. The Astrophysical Journal, 773 (2). pp. 98-125. ISSN 0004-637X

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Abstract

We present the validation and characterization of Kepler-61b: a 2.15 R ⊕ planet orbiting near the inner edge of the habitable zone of a low-mass star. Our characterization of the host star Kepler-61 is based upon a comparison with a set of spectroscopically similar stars with directly measured radii and temperatures. We apply a stellar prior drawn from the weighted mean of these properties, in tandem with the Kepler photometry, to infer a planetary radius for Kepler-61b of 2.15 ± 0.13 R ⊕ and an equilibrium temperature of 273 ± 13 K (given its period of 59.87756 ± 0.00020 days and assuming a planetary albedo of 0.3). The technique of leveraging the physical properties of nearby 'proxy' stars allows for an independent check on stellar characterization via the traditional measurements with stellar spectra and evolutionary models. In this case, such a check had implications for the putative habitability of Kepler-61b: the planet is 10% warmer and larger than inferred from K-band spectral characterization. From the Kepler photometry, we estimate a stellar rotation period of 36 days, which implies a stellar age of >1 Gyr. We summarize the evidence for the planetary nature of the Kepler-61 transit signal, which we conclude is 30,000 times more likely to be due to a planet than a blend scenario. Finally, we discuss possible compositions for Kepler-61b with a comparison to theoretical models as well as to known exoplanets with similar radii and dynamically measured masses.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Access to published version in accordance with the copyright policy of the publisher.
Faculty / Department / School: No Faculty
Date Deposited: 05 Jun 2017 02:45
Last Modified: 27 Jun 2017 00:57
Uncontrolled Keywords: eclipses; planetary systems; stars: individual (Kepler-61, KOI 1361, KIC 6960913);
Fields of Research : 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
Socio-Economic Objective: E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
Identification Number or DOI: 10.1088/0004-637X/773/2/98
URI: http://eprints.usq.edu.au/id/eprint/32125

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