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Mikkel Nørup Lund

THE K2-ESPRINT PROJECT. V. A SHORT-PERIOD GIANT PLANET ORBITING A SUBGIANT STAR

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  • Vincent Van Eylen
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  • Simon Albrecht
  • Davide Gandolfi, Heidelberg Univ, Ruprecht Karl University Heidelberg, Zentrum Astron, Landessternwarte Konigstuhl
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  • Fei Dai, MIT, Massachusetts Institute of Technology (MIT), Kavli Inst Astrophys & Space Res
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  • Joshua N. Winn, MIT, Massachusetts Institute of Technology (MIT), Kavli Inst Astrophys & Space Res
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  • Teriyuki Hirano, Tokyo Inst Technol, Tokyo Institute of Technology, Dept Earth & Planetary Sci, Meguro Ku
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  • Norio Narita, Natl Inst Nat Sci, National Institutes of Natural Sciences (NINS) - Japan, Astrobiol Ctr
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  • Hans Bruntt
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  • Jorge Prieto-Arranz, ULL, Universidad de la Laguna, Dept Astrofis
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  • Victor J. S. Bejar, ULL, Universidad de la Laguna, Dept Astrofis
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  • Grzegorz Nowak, ULL, Universidad de la Laguna, Dept Astrofis
  • ,
  • Mikkel N. Lund
  • Enric Palle, ULL, Universidad de la Laguna, Dept Astrofis
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  • Ignasi Ribas, CSIC IEEC, Autonomous University of Barcelona, Consejo Superior de Investigaciones Cientificas (CSIC), Inst Ciencies Espai
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  • Roberto Sanchis-Ojeda, Univ Calif Berkeley, University of California Berkeley, University of California System, Dept Astron
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  • Liang Yu, MIT, Massachusetts Institute of Technology (MIT), Kavli Inst Astrophys & Space Res
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  • Pamela Arriagada, Carnegie Inst Sci, Carnegie Institution for Science, Dept Terr Magnetism
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  • R. Paul Butler, Carnegie Inst Sci, Carnegie Institution for Science, Dept Terr Magnetism
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  • Jeffrey D. Crane, Observ Carnegie Inst Washington, Carnegie Institution for Science
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  • Rasmus Handberg
  • Hans Deeg, ULL, Universidad de la Laguna, Dept Astrofis
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  • Jens Jessen-Hansen
  • John A. Johnson, Harvard Smithsonian Ctr Astrophys, Harvard University, Smithsonian Institution
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  • David Nespral, ULL, Universidad de la Laguna, Dept Astrofis
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  • Leslie Rogers, CALTECH, California Institute of Technology, Div Geol & Planetary Sci
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  • Tsuguru Ryu, Natl Inst Nat Sci, National Institutes of Natural Sciences (NINS) - Japan, Astrobiol Ctr
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  • Stephen Shectman, Observ Carnegie Inst Washington, Carnegie Institution for Science
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  • Tushar Shrotriya
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  • Ditte Slumstrup
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  • Yoichi Takeda, Natl Astron Observ Japan, National Astronomical Observatory of Japan, National Institutes of Natural Sciences (NINS) - Japan, Okayama Astrophys Observ
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  • Johanna Teske, Observ Carnegie Inst Washington, Carnegie Institution for Science
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  • Ian Thompson, Observ Carnegie Inst Washington, Carnegie Institution for Science
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  • Andrew Vanderburg, Harvard Smithsonian Ctr Astrophys, Harvard University, Smithsonian Institution
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  • Robert Wittenmyer, Univ Southern Queensland, Computat Engn & Sci Res Ctr

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(-0.42)(+0.48) R-circle dot and 1.53(-0.13)(+0.13) M-circle dot, respectively, and a very close-in transiting planet, with a/R-* = 3.4. Radial velocity (RV) follow-up using the HARPS, FIES, and PFS instruments leads to a planetary mass of 50.3(-9.4)(+9.7) M-circle plus. In combination with a radius measurement of 8.3 +/- 1.1, this results in a mean planetary density of 0.50(-0.17)(+0.29) g cm(-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.

OriginalsprogEngelsk
Artikelnummer143
TidsskriftAstronomical Journal
Vol/bind152
Nummer5
Antal sider11
ISSN0004-6256
DOI
StatusUdgivet - nov. 2016

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