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R Coronae Borealis Stars in M31 from the Palomar Transient Factory

Tang, Sumin and Cao, Yi and Bildsten, Lars and Nugent, Peter and Bellm, Eric and Kulkarni, Shrinivas R. and Laher, Russ and Levitan, David and Masci, Frank and Ofek, Eran O. and Prince, Thomas A. and Sesar, Branimir and Surace, Jason (2013) R Coronae Borealis Stars in M31 from the Palomar Transient Factory. Astrophysical Journal Letters, 767 (2). Art. No. L23. ISSN 2041-8205.

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We report the discovery of R Coronae Borealis (RCB) stars in the Andromeda galaxy (M31) using the Palomar Transient Factory (PTF). RCB stars are rare hydrogen-deficient, carbon-rich supergiant variables, most likely the merger products of two white dwarfs. These new RCBs, including two confirmed ones and two candidates, are the first to be found beyond the Milky Way and the Magellanic Clouds. All of M31 RCBs showed >1.5 mag irregular declines over timescales of weeks to months. Due to the limiting magnitude of our data (R ≈ 21-22 mag), these RCB stars have R ≈ 19.5-20.5 mag at maximum light, corresponding to M_R = –4 to –5, making them some of the most luminous RCBs known. Spectra of two objects show that they are warm RCBs, similar to the Milky Way RCBs RY Sgr and V854 Cen. We consider these results, derived from a pilot study of M31 variables, as an important proof-of-concept for the study of rare bright variables in nearby galaxies with the PTF or other synoptic surveys.

Item Type:Article
Related URLs:
URLURL TypeDescription
Tang, Sumin0000-0002-6225-8918
Cao, Yi0000-0002-8036-8491
Nugent, Peter0000-0002-3389-0586
Bellm, Eric0000-0001-8018-5348
Kulkarni, Shrinivas R.0000-0001-5390-8563
Laher, Russ0000-0003-2451-5482
Masci, Frank0000-0002-8532-9395
Ofek, Eran O.0000-0002-6786-8774
Prince, Thomas A.0000-0002-8850-3627
Sesar, Branimir0000-0002-0834-3978
Surace, Jason0000-0001-7291-0087
Additional Information:© 2013 American Astronomical Society. Received 2013 March 7; accepted 2013 March 15; published 2013 April 1. We thank Geoff Clayton for pointing out the similarities between PTF-M31-RCB-1 (2) and RY Sgr (V854 Cen), providing spectra of RY Sgr and V854 Cen, and many helpful discussions. We thank the anonymous referee for comments that have helped to improve this Letter. We thank Sagi Ben-Ami and Dong Xu for reducing two candidate spectra, and Adam Miller for helpful discussion. This work was supported by the National Science Foundation under grants PHY 11-25915 and AST 11-09174. E.O.O. is incumbent of the Arye Dissentshik career development chair and is grateful to support by a grant from the Israeli Ministry of Science. Facilities: PO:1.2m (PTF), Hale (DBSP), Keck:II (DEIMOS)
Group:Palomar Transient Factory, Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
NSFPHY 11-25915
NSFAST 11-09174
Ministry of Science (Israel)UNSPECIFIED
Subject Keywords:galaxies: individual (M31); stars: AGB and post-AGB; stars: carbon; stars: variables: general; supergiants
Issue or Number:2
Record Number:CaltechAUTHORS:20130516-133502401
Persistent URL:
Official Citation:R Coronae Borealis Stars in M31 from the Palomar Transient Factory Sumin Tang et al. 2013 ApJ 767 L23
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:38545
Deposited By: Jason Perez
Deposited On:16 May 2013 21:00
Last Modified:22 Nov 2019 17:40

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