A pair of giant planets around the evolved intermediate-mass star HD 47366: Multiple circular orbits or a mutually retrograde configuration

Journal Article · Mon Feb 29 23:00:00 EST 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/819/1/59· OSTI ID:22886974

Sato, Bun’ei ^[1]; Wang, Liang; Liu, Yu-Juan; Zhao, Gang; Song, Nan; He, Wei; Zhao, Fei ^[2]; Omiya, Masashi; Harakawa, Hiroki; Noguchi, Kunio; Ando, Hiroyasu; Okada, Norio; Takeda, Yoichi ^[3]; Nagasawa, Makiko ^[4]; Wittenmyer, Robert A. ^[5]; Butler, Paul ^[6]; Kambe, Eiji; Izumiura, Hideyuki ^[7]; Yoshida, Michitoshi ^[8]; Itoh, Yoichi ^[9] ; others, and

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1. Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551 (Japan)
2. Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)
3. National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)
4. Department of Physics, Kurume University School of Medicine, 67 Asahi-machi, Kurume-city, Fukuoka 830-0011 (Japan)
5. School of Physics, University of New South Wales, Sydney 2052 (Australia)
6. Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road, NW, Washington, DC 20015-1305 (United States)
7. Okayama Astrophysical Observatory, National Astronomical Observatory of Japan, Kamogata, Okayama 719-0232 (Japan)
8. Hiroshima Astrophysical Science Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan)
9. Nishi-Harima Astronomical Observatory, Center for Astronomy, University of Hyogo, 407-2, Nishigaichi, Sayo, Hyogo 679-5313 (Japan)

We report the detection of a double planetary system around the evolved intermediate-mass star HD 47366 from precise radial-velocity measurements at the Okayama Astrophysical Observatory, Xinglong Station, and Australian Astronomical Observatory. The star is a K1 giant with a mass of 1.81 ± 0.13 M{sub ⊙}, a radius of 7.30 ± 0.33 R{sub ⊙}, and solar metallicity. The planetary system is composed of two giant planets with minimum masses of 1.75{sub −0.17}{sup +0.20} M{sub J} and 1.86{sub −0.15}{sup +0.16} M{sub J}, orbital periods of 363.3{sub −2.4}{sup +2.5} days and 684.7{sub −4.9}{sup +5.0} days, and eccentricities of 0.089{sub −0.060}{sup +0.079} and 0.278{sub −0.094}{sup +0.067}, respectively, which are derived by a double Keplerian orbital fit to the radial-velocity data. The system adds to the population of multi-giant-planet systems with relatively small orbital separations, which are preferentially found around evolved intermediate-mass stars. Dynamical stability analysis for the system revealed, however, that the best-fit orbits are unstable in the case of a prograde configuration. The system could be stable if the planets were in 2:1 mean-motion resonance, but this is less likely, considering the observed period ratio and eccentricity. A present possible scenario for the system is that both of the planets have nearly circular orbits, namely the eccentricity of the outer planet is less than ∼0.15, which is just within 1.4σ of the best-fit value, or the planets are in a mutually retrograde configuration with a mutual orbital inclination larger than 160°.

• OSTI ID: 22886974
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 819; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTROPHYSICS
DETECTION
INCLINATION
MASS
METALLICITY
ORBITS
PLANETS
RADIAL VELOCITY
RESONANCE
STARS