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A Runaway Red Supergiant in M31

Evans, Kate Anne and Massey, Philip (2015) A Runaway Red Supergiant in M31. Astronomical Journal, 150 (5). Art. No. 149. ISSN 1538-3881.

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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^(−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_V = −5.7, logL/L_☉ = 4.76, an effective temperature of 3700 K, and an inferred mass of 12–15M_⊙. The star may be a high-mass analog of the hypervelocity stars, given that its peculiar space velocity is probably 400–450 km s^(−1), comparable to the escape speed from M31's disk.

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Additional Information:© 2015 The American Astronomical Society. Received 2015 August 19; accepted 2015 September 22; published 2015 October 14. We are grateful to the Steward Observatory Time Allocation Committee for their generous allocation of observing time on the MMT, and to Perry Berlind, Mike Calkins, and Marc Lacasse for their excellent support of Hectospec. Nelson Caldwell kindly provided the calibration files for flux calibrating our data, as well as managing the difficult task of queue scheduling our program. Kathryn Neugent helped take some of these observations as part of another project, and also provided very useful scientific suggestions on this project. Emily Levesque and Joe Llama provided useful help with some of the coding for fitting the MARCS models. An anonymous referee kindly made useful suggestions which improved this paper. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation (NSF). K.A.E.'s work was supported through the NSF's Research Experiences for Undergraduates program through Northern Arizona University and Lowell Observatory (AST-1461200) and P.M.'s were partially supported by the NSF through AST-1008020 and through Lowell Observatory. A grant from the Mt. Cuba Astronomical Foundation for computing facilities is gratefully acknowledged. Facility: MMT (Hectospec) - .
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Cuba Astronomical FoundationUNSPECIFIED
Subject Keywords:galaxies: individual (M31) ; galaxies: stellar content; Local Group; supergiants
Issue or Number:5
Record Number:CaltechAUTHORS:20160111-085514321
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Official Citation:Kate Anne Evans and Philip Massey 2015 The Astronomical Journal 150 149
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:63530
Deposited By: Ruth Sustaita
Deposited On:12 Jan 2016 23:50
Last Modified:03 Oct 2019 09:29

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