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

Published online by Cambridge University Press:  27 October 2016

Teruyuki Hirano
Affiliation:
Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan email: hirano@geo.titech.ac.jp
Bun'ei Sato
Affiliation:
Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan email: hirano@geo.titech.ac.jp
Kento Masuda
Affiliation:
The University of Tokyo
Othman Michel Benomar
Affiliation:
The University of Tokyo
Yoichi Takeda
Affiliation:
National Astronomical Observatory
Masashi Omiya
Affiliation:
National Astronomical Observatory
Hiroki Harakawa
Affiliation:
National Astronomical Observatory
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Abstract

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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.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2016 

References

Hirano, T., Masuda, K., Sato, B., Benomar, O., Takeda, Y., Omiya, M., Harakawa, H., & Kobayashi, A. 2015, ApJ, 799, 9 Google Scholar
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