Evidence for a companion to BM Gem, a silicate carbon star
Hideyuki Izumiura, Kunio Noguchi, Wako Aoki, Satoshi Honda, Hiroyasu, Ando, Masahide Takada-Hidai, Eiji Kambe, Satoshi Kawanomoto, Kozo Sadakane,, Bun'ei Sato, Akito Tajitsu, Wataru Tanaka, Ki'ichi Okita, Etsuji Watanabe,, and Michitoshi Yoshida

TL;DR
This paper presents evidence that BM Gem, a silicate carbon star, has a low-mass companion causing high-velocity outflows and ionized regions, indicating a binary system with a possible dwarf or white dwarf companion.
Contribution
The study provides the first spectroscopic evidence for a companion in BM Gem, revealing high-velocity outflows and accretion processes in a silicate carbon star.
Findings
Detection of Balmer and Paschen continuum emission and P Cygni profiles.
High outflow velocity of at least 400 km/s, the highest in a carbon star.
Evidence supporting a binary system with a low-mass, low-luminosity companion.
Abstract
Balmer and Paschen continuum emission as well as Balmer series lines of P Cygni-type profile from H_gamma through H_23 are revealed in the violet spectra of BM Gem, a carbon star associated with an oxygen-rich circumstellar shell (`silicate carbon star') observed with the high dispersion spectrograph (HDS) on the Subaru telescope. The blue-shifted absorption in the Balmer lines indicates the presence of an outflow, the line of sight velocity of which is at least 400 km s^-1, which is the highest outflow velocity observed to date in a carbon star. We argue that the observed unusual features in BM Gem are strong evidence for the presence of a companion, which should form an accretion disk that gives rise to both an ionized gas region and a high velocity, variable outflow. The estimated luminosity of ~0.2 (0.03-0.6) L_sun for the ionized gas can be maintained by a mass accretion rate to a…
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Taxonomy
TopicsStellar, planetary, and galactic studies · Astrophysics and Star Formation Studies · Astronomy and Astrophysical Research
