A Common Proper Motion Stellar Companion to HAT-P-7
astro-ph.EP
/ Authors
Norio Narita, Yasuhiro H. Takahashi, Masayuki Kuzuhara, Teruyuki Hirano, Takuya Suenaga, Ryo Kandori, Tomoyuki Kudo, Bun'ei Sato, Ryuji Suzuki, Shigeru Ida
and 44 more authors
Makiko Nagasawa, Lyu Abe, Wolfgang Brandner, Timothy D. Brandt, Joseph Carson, Sebastian E. Egner, Markus Feldt, Miwa Goto, Carol A. Grady, Olivier Guyon, Jun Hashimoto, Yutaka Hayano, Masahiko Hayashi, Saeko S. Hayashi, Thomas Henning, Klaus W. Hodapp, Miki Ishii, Masanori Iye, Markus Janson, Gillian R. Knapp, Nobuhiko Kusakabe, Jungmi Kwon, Taro Matsuo
/ Abstract
We report that HAT-P-7 has a common proper motion stellar companion. The companion is located at $\sim3.9$ arcsec to the east and estimated as an M5.5V dwarf based on its colors. We also confirm the presence of the third companion, which was first reported by Winn et al. (2009), based on long-term radial velocity measurements. We revisit the migration mechanism of HAT-P-7b given the presence of those companions, and propose sequential Kozai migration as a likely scenario in this system. This scenario may explain the reason for an outlier in the discussion of the spin-orbit alignment timescale for HAT-P-7b by Albrecht et al. (2012).