High-contrast Imaging of Intermediate-mass Giants with Long-term Radial Velocity Trends
Abstract
A radial velocity (RV) survey for intermediate-mass giants has been in operation for over a decade at Okayama Astrophysical Observatory (OAO). The OAO survey has revealed that some giants show long-term linear RV accelerations (RV trends), indicating the presence of outer companions. Direct-imaging observations can help clarify what objects generate these RV trends. We present the results of high-contrast imaging observations of six intermediate-mass giants with long-term RV trends using the Subaru Telescope and HiCIAO camera. We detected co-moving companions to γ Hya B ({0.61}-0.14+0.12{M}⊙ ), HD 5608 B (0.10+/- 0.01{M}⊙ ), and HD 109272 B (0.28+/- 0.06{M}⊙ ). For the remaining targets (ι Dra, 18 Del, and HD 14067), we exclude companions more massive than 30-60 M Jup at projected separations of 1″-7″. We examine whether these directly imaged companions or unidentified long-period companions can account for the RV trends observed around the six giants. We find that the Kozai mechanism can explain the high eccentricity of the inner planets ι Dra b, HD 5608 b, and HD 14067 b.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2016
- DOI:
- arXiv:
- arXiv:1603.02017
- Bibcode:
- 2016ApJ...825..127R
- Keywords:
-
- binaries: general;
- methods: observational;
- planetary systems;
- techniques: high angular resolution;
- techniques: radial velocities;
- Astrophysics - Earth and Planetary Astrophysics;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 33 pases, 9 figures, accepted to ApJ