High-Contrast Imaging of Intermediate-Mass Giants with Long-Term Radial Velocity Trends

Tsuguru Ryu , Bun'ei Sato , Masayuki Kuzuhara , Norio Narita , Yasuhiro H. Takahashi , Taichi Uyama , Tomoyuki Kudo , Nobuhiko Kusakabe

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Jun Hashimoto Masashi Omiya Hiroki Harakawa Lyu Abe Hiroyasu Ando Wolfgang Brandner Timothy D. Brandt Joseph C. Carson Thayne Currie Sebastian Egner Markus Feldt Miwa Goto Carol A. Grady Olivier Guyon Yutaka Hayano Masahiko Hayashi Saeko S. Hayashi Krzysztof G. He{\l}miniak Thomas Henning Klaus W. Hodapp Shigeru Ida Miki Ishii Yoichi Itoh Masanori Iye Hideyuki Izumiura Markus Janson Eiji Kambe Ryo Kandori Gillian R. Knapp Eiichiro Kokubo Jungmi Kwon Taro Matsuo Satoshi Mayama Michael W. McElwain Kyle Mede Shoken Miyama Jun-ichi Morino Amaya Moro-Martin Tetsuo Nishimura Tae-Soo Pyo Eugene Serabyn Takuya Suenaga Hiroshi Suto Ryuji Suzuki Michihiro Takami Naruhisa Takato Yoichi Takeda Hiroshi Terada Christian Thalmann Edwin L. Turner Makoto Watanabe John Wisniewski Toru Yamada Michitoshi Yoshida Hideki Takami Tomonori Usuda Motohide Tamura

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classification 🌌 astro-ph.EP astro-ph.SR

keywords companionsgiantstrendsimagingintermediate-masslong-termodothigh-contrast

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A radial velocity (RV) survey for intermediate-mass giants has been operated 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 or six intermediate-mass giants with long-term RV trends using the Subaru Telescope and HiCIAO camera. We detected co-moving companions to $\gamma$ Hya B ($0.61^{+0.12}_{-0.14} M_\odot$), HD 5608 B ($0.10 \pm 0.01 M_\odot$), and HD 109272 B ($0.28 \pm 0.06 M_\odot$). For the remaining targets($\iota$ Dra, 18 Del, and HD 14067) we exclude companions more massive than 30-60 $M_\mathrm{Jup}$ at projected separations of 1arcsec-7arcsec. 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 $\iota$ Dra b, HD 5608 b, and HD 14067 b.

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High-Contrast Imaging of Intermediate-Mass Giants with Long-Term Radial Velocity Trends

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