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Title: EXOPLANET CHARACTERIZATION BY PROXY: A TRANSITING 2.15 R{sub Circled-Plus} PLANET NEAR THE HABITABLE ZONE OF THE LATE K DWARF KEPLER-61

We present the validation and characterization of Kepler-61b: a 2.15 R{sub Circled-Plus} 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{sub Circled-Plus} 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 concludemore » 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.« less
Authors:
; ; ; ; ;  [1] ; ; ;  [2] ;  [3] ;  [4] ; ; ;  [5] ;  [6] ;  [7]
  1. University of Washington, Seattle, WA 98195 (United States)
  2. California Institute of Technology, Pasadena, CA 91125 (United States)
  3. Institute for Astronomy, University of Hawai'i, Honolulu, HI 96822 (United States)
  4. NASA Exoplanet Science Institute/Caltech, Pasadena, CA 91125 (United States)
  5. NASA Ames Research Center, Moffett Field, CA 94035 (United States)
  6. Southern Connecticut State University, New Haven, CT 06515 (United States)
  7. National Optical Astronomy Observatory, Tucson, AZ 85719 (United States)
Publication Date:
OSTI Identifier:
22131018
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 773; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ALBEDO; DWARF STARS; ECLIPSE; MASS; PHOTOMETRY; PHYSICAL PROPERTIES; PLANETS; ROTATION; SPECTRA; TEMPERATURE RANGE 0273-0400 K