Search for Close-in Planets around Evolved Stars with Phase-curve variations and Radial Velocity Measurements

Teruyuki Hirano, Bun'Ei Sato, Kento Masuda, Othman Michel Benomar, Yoichi Takeda, Masashi Omiya, Hiroki Harakawa

Research output: Contribution to journalArticle

Abstract

Tidal interactions are a key process to understand the evolution history of close-in exoplanets. But tidals still have a large uncertainty in their prediction for the damping timescales of stellar obliquity and semi-major axis. We have worked on a search for transiting giant planets around evolved stars, for which few close-in planets were discovered. It has been reported that evolved stars lack close-in planets, which is often attributed to the tidal evolution and/or engulfment of close-in planets by the hosts. Meanwhile, Kepler has detected a certain fraction of transiting planet candidates around evolved stars. Confirming the planetary nature for these candidates is especially important since the comparison between the occurrence rates of close-in planets around main sequence stars and evolved stars provides a unique opportunity to discuss the final stage of close-in planets. With the aim of confirming KOI planet candidates around evolved stars, we measured precision radial velocities (RVs) for evolved stars with transiting planet candidates using Subaru/HDS. We also developed a new code which simultaneously models and fits the observed RVs and phase-curve variations in the Kepler data (e.g., transits, stellar ellipsoidal variations, and planet emission/reflected light). As a result of applying the global fit to KOI giants/subgiants, we confirmed two giant planets around evolved stars (Kepler-91 and KOI-1894), as well as revealed that KOI-977 is more likely a false positive.

Original languageEnglish (US)
Pages (from-to)63-64
Number of pages2
JournalProceedings of the International Astronomical Union
Volume11
Issue numberA29A
DOIs
StatePublished - 2015

Keywords

  • KOI-1894
  • KOI-2133
  • planets and satellites: individual (KOI-977

ASJC Scopus subject areas

  • Medicine (miscellaneous)
  • Astronomy and Astrophysics
  • Nutrition and Dietetics
  • Public Health, Environmental and Occupational Health
  • Space and Planetary Science

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