A runaway red supergiant in M31

Journal Article · Sun Nov 01 04:00:00 EST 2015 · The Astronomical Journal (Online)

DOI:https://doi.org/10.1088/0004-6256/150/5/149· OSTI ID:22890185

Evans, Kate Anne; Massey, Philip ^[1]

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1. Lowell Observatory, 1400 W Mars Hill Road, Flagstaff, AZ 86001 (United States)

A significant percentage of OB stars are runaways, so we can expect a similar percentage of their evolved descendants to also be runaways. However, recognizing such stars presents its own set of challenges, as these older, more evolved stars will have drifted farther from their birthplace, and thus their velocities might not be obviously peculiar. Several Galactic red supergiants (RSGs) have been described as likely runaways based on the existence of bow shocks, including Betelgeuse. Here we announce the discovery of a runaway RSG in M31 based on a 300 km s{sup −1} discrepancy with M31's kinematics. The star is found about 21′ (4.6 kpc) from the plane of the disk, but this separation is consistent with its velocity and likely age (∼10 Myr). The star, J004330.06+405258.4, is an M2 I, with M{sub V} = −5.7, logL/L{sub ⊙} = 4.76, an effective temperature of 3700 K, and an inferred mass of 12–15M{sub ⊙}. The star may be a high-mass analog of the hypervelocity stars, given that its peculiar space velocity is probably 400–450 km s{sup −1}, comparable to the escape speed from M31's disk.

• OSTI ID: 22890185
• Journal Information: The Astronomical Journal (Online), Journal Name: The Astronomical Journal (Online) Journal Issue: 5 Vol. 150; ISSN 1538-3881
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
COMPARATIVE EVALUATIONS
GALAXIES
MASS
SHOCK WAVES
SPACE
SUPERGIANT STARS