THE K2-ESPRINT PROJECT. V. A SHORT-PERIOD GIANT PLANET ORBITING A SUBGIANT STAR
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Eylen-2016-THE K2-ESPRINT PROJECT. V. A SHORT-.pdf
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1.4 MB
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Checksum (MD5)
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Author(s)
Van Eylen, Vincent
Albrecht, Simon
Gandolf, Davide
Hirano, Teriyuki
Narita, Norio
Bruntt, Hans
Prieto-Arranz, Jorge
Béjar, Víctor J. S.
Nowak, Grzegorz
Lund, Mikkel N.
Date Issued
October 2016
Journal
Astronomical Journal
Publisher
IOP Publishing
Citation
Van Eylen, Vincent, Simon Albrecht, Davide Gandolfi, Fei Dai, Joshua N. Winn, Teriyuki Hirano, Norio Narita, et al. “THE K2-ESPRINT PROJECT. V. A SHORT-PERIOD GIANT PLANET ORBITING A SUBGIANT STAR.” The Astronomical Journal 152, no. 5 (October 26, 2016): 143. © 2016 The American Astronomical Society
Version
Final published version
Abstract
We report on the discovery and characterization of the transiting planet K2-39b (EPIC 206247743b). With an orbital period of 4.6 days, it is the shortest-period planet orbiting a subgiant star known to date. Such planets are rare, with only a handful of known cases. The reason for this is poorly understood but may reflect differences in planet occurrence around the relatively high-mass stars that have been surveyed, or may be the result of tidal destruction of such planets. K2-39 (EPIC 206247743) is an evolved star with a spectroscopically derived stellar radius and mass of 3.88 [subscript -0.42] [superscript +0.48] R [subscript ⊙] and 1.53[subscript-0.12] [superscript +0.13] M[subscript ⊙], respectively, and a very close-in transiting planet, with a/R [subscript asterisk]= 3.4 Radial velocity (RV) follow-up using the HARPS, FIES, and PFS instruments leads to a planetary mass of 50.3 [subscript -9.4] [superscript +9.7] M [subscript ⊙]. In combination with a radius measurement of 8.3 ± 1.1 R [subscript oplus], this results in a mean planetary density of 0.50 [subscript -0.17] [superscript +0.29] g cm [superscript -3]. We furthermore discover a long-term RV trend, which may be caused by a long-period planet or stellar companion. Because K2-39b has a short orbital period, its existence makes it seem unlikely that tidal destruction is wholly responsible for the differences in planet populations around subgiant and main-sequence stars. Future monitoring of the transits of this system may enable the detection of period decay and constrain the tidal dissipation rates of subgiant stars.
MIT Department
Massachusetts Institute of Technology. Department of Physics
MIT Kavli Institute for Astrophysics and Space Research
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DOI of Published Version
https://doi.org/10.3847/0004-6256/152/5/143
