HD 89345: a bright oscillating star hosting a transiting warm Saturn-sized planet observed by K2

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DOI

  • V. Van Eylen, Leiden Univ, Leiden University, Leiden Observ
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  • F. Dai, Princeton Univ, Princeton University, Dept Astrophys Sci
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  • S. Mathur, Instituto de Astrofísica de Canarias
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  • D. Gandolfi, Univ Torino, Dipartmento Fis
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  • S. Albrecht
  • M. Fridlund, Chalmers Univ Technol, Onsala Space Observ, Dept Space Earth & Environm
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  • R. A. Garcia, Univ Paris Diderot, CEA, University of Paris Diderot - Paris VII, Centre National de la Recherche Scientifique (CNRS), PRES University Sorbonne Paris Cite, Lab AIM, CEA DSM CNRS, IRFU SAp,Ctr Saclay
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  • E. Guenther, Thüringer Landessternwarte Tautenburg
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  • M. Hjorth
  • A. B. Justesen
  • J. Livingston, Univ Tokyo, University of Tokyo, Grad Sch Sci, Dept Astron, Bunkyo Ku
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  • M. N. Lund
  • F. P. Prerez Hernandez, Instituto de Astrofísica de Canarias
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  • J. Prieto-Arranz, Instituto de Astrofísica de Canarias
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  • C. Regulo, Instituto de Astrofísica de Canarias
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  • L. Bugnet, Univ Paris Diderot, CEA, University of Paris Diderot - Paris VII, Centre National de la Recherche Scientifique (CNRS), PRES University Sorbonne Paris Cite, Lab AIM, CEA DSM CNRS, IRFU SAp,Ctr Saclay
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  • M. E. Everett, Natl Opt Astron Observ
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  • T. Hirano, Tokyo Inst Technol, Tokyo Institute of Technology, Dept Earth & Planetary Sci, Meguro Ku
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  • D. Nespral, Instituto de Astrofísica de Canarias
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  • G. Nowak, Instituto de Astrofísica de Canarias
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  • E. Palle, Instituto de Astrofísica de Canarias
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  • V. Silva Aguirre
  • T. Trifonov, Max Planck Inst Astron, Max Planck Society
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  • J. N. Winn, Princeton Univ, Princeton University, Dept Astrophys Sci
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  • O. Barragan, Univ Torino, Dipartmento Fis
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  • P. G. Beck, Instituto de Astrofísica de Canarias
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  • W. J. Chaplin, Univ Birmingham, University of Birmingham, Sch Phys & Astron
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  • W. D. Cochran, Univ Texas Austin, University of Texas Austin, McDonald Observ
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  • S. Csizmadia, German Aerosp Ctr, Inst Planetary Res
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  • H. Deeg, Instituto de Astrofísica de Canarias
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  • M. Endl, Univ Texas Austin, University of Texas Austin, McDonald Observ
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  • P. Heeren, Heidelberg Univ, Ruprecht Karl University Heidelberg, ZAH, Landessternwarte
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  • S. Grziwa, Univ Cologne, University of Cologne, Rhein Inst Umweltforsch, Abt Planetenforsch
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  • A. P. Hatzes, Thüringer Landessternwarte Tautenburg
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  • D. Hidalgo, Instituto de Astrofísica de Canarias
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  • J. Korth, Univ Cologne, University of Cologne, Rhein Inst Umweltforsch, Abt Planetenforsch
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  • S. Mathis, Univ Paris Diderot, CEA, University of Paris Diderot - Paris VII, Centre National de la Recherche Scientifique (CNRS), PRES University Sorbonne Paris Cite, Lab AIM, CEA DSM CNRS, IRFU SAp,Ctr Saclay
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  • P. Montanes Rodriguez, Instituto de Astrofísica de Canarias
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  • N. Narita, Natl Inst Nat Sci, National Institutes of Natural Sciences (NINS) - Japan, Astrobiol Ctr
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  • M. Patzold, Univ Cologne, University of Cologne, Rhein Inst Umweltforsch, Abt Planetenforsch
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  • C. M. Persson, Chalmers Univ Technol, Onsala Space Observ, Dept Space Earth & Environm
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  • F. Rodler, European Southern Observ
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  • A. M. S. Smith, German Aerosp Ctr, Inst Planetary Res

We report the discovery and characterization of HD 89345b (K2-234b; EPIC 248777106b), a Saturn-sized planet orbiting a slightly evolved star. HD 89345 is a bright star (V = 9.3 mag) observed by the K2 mission with 1 min time sampling. It exhibits solar-like oscillations. We conducted asteroseismology to determine the parameters of the star, finding themass and radius to be 1.12(-0.01)(+0.04) and 1.657(-0.004)(+0.020)R(circle dot), respectively. The star appears to have recently left the main sequence, based on the inferred age, 9.4(-1.3)(+0.4)Gyr, and the non-detection of mixed modes. The star hosts a 'warm Saturn' (P = 11.8 d, R-p = 6.86 +/- 0.14 R-circle plus). Radial-velocity follow-up observations performed with the FIbre-fed Echelle Spectrograph, HARPS, and HARPS-N spectrographs show that the planet has a mass of 35.7 +/- 3.3 M-circle plus. The data also show that the planet's orbit is eccentric (e approximate to 0.2). An investigation of the rotational splitting of the oscillation frequencies of the star yields no conclusive evidence on the stellar inclination angle. We further obtained Rossiter-McLaughlin observations, which result in a broad posterior of the stellar obliquity. The planet seems to confirm to the same patterns that have been observed for other sub-Saturns regarding planet mass and multiplicity, orbital eccentricity, and stellar metallicity.

Original languageEnglish
JournalMonthly Notices of the Royal Astronomical Society
Volume478
Issue4
Pages (from-to)4866-4880
Number of pages15
ISSN0035-8711
DOIs
Publication statusPublished - Aug 2018

    Research areas

  • asteroseismology, planets and satellites: composition, planets and satellites: formation, planets and satellites: fundamental parameters, COOL DWARF STARS, SUN-LIKE STAR, TIDAL DISSIPATION, GIANT PLANETS, BALMER LINES, LIGHT CURVES, P-MODES, KEPLER, ROTATION, ASTEROSEISMOLOGY

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