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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 Désert, 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. Astrophysical Journal, 773 (2). Art. No. 98. ISSN 0004-637X.

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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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Ballard, Sarah0000-0002-3247-5081
Charbonneau, David0000-0002-9003-484X
Torres, Guillermo0000-0002-5286-0251
Désert, Jean-Michel0000-0002-0875-8401
Newton, Elisabeth0000-0003-4150-841X
Mann, Andrew W.0000-0003-3654-1602
Ciardi, David R.0000-0002-5741-3047
Crepp, Justin R.0000-0003-0800-0593
Howell, Steven B.0000-0002-2532-2853
Horch, Elliott P.0000-0003-2159-1463
Everett, Mark E.0000-0002-0885-7215
Shporer, Avi0000-0002-1836-3120
Additional Information:© 2013 American Astronomical Society. Received 2012 September 5; accepted 2013 April 22; published 2013 July 30. We thank Perry Berlind and Mike Calkins at the Fred Lawrence Whipple Observatory for gathering the FAST spectra of Kepler-61 and GJ 380. We thank Courtney Dressing for applying the methodology of Dressing & Charbonneau (2013) to deduce the physical properties of Kepler-61 and sharing these values with us. We thank Philip Muirhead, Katherine Hamren, Everett Schlawin, Bárbara Rojas-Ayala, Kevin Covey, and James Lloyd for gathering, reducing, and sharing the TripleSpec K-band spectrum of Kepler-61. We thank the Spitzer team at the Infrared Processing and Analysis Center in Pasadena, California, and in particular Nancy Silbermann for scheduling the Spitzer observations of this program. This work was performed in part under contract with the California Institute of Technology (Caltech) funded by NASA through the Sagan Fellowship Program. It was conducted with observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. This work is also based on observations made with Kepler, which was competitively selected as the tenth Discovery mission. Funding for this mission is provided by NASA's Science Mission Directorate. The authors would like to thank the many people who generously gave so much their time to make this Mission a success. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Subject Keywords:eclipses; planetary systems; stars: individual (Kepler-61, KOI 1361, KIC 6960913)
Issue or Number:2
Record Number:CaltechAUTHORS:20130920-141844033
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Official Citation:Exoplanet Characterization by Proxy: A Transiting 2.15 R ⊕ Planet near the Habitable Zone of the Late K Dwarf Kepler-61 Sarah Ballard et al. 2013 ApJ 773 98
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:41453
Deposited By: Ruth Sustaita
Deposited On:20 Sep 2013 23:17
Last Modified:10 Oct 2019 21:05

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