R Coronae Borealis stars in M31 from the Palomar Transient Factory

Sumin Tang, Yi Cao, Lars Bildsten, Peter Nugent, Eric Bellm, Shrinivas R. Kulkarni, Russ Laher, David Levitan, Frank Masci, Eran O. Ofek, Thomas A. Prince, Branimir Sesar, Jason Surace

Research output: Contribution to journalArticlepeer-review


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 MR = -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.

Original languageEnglish
Article numberL23
JournalAstrophysical Journal Letters
Issue number2
StatePublished - 20 Apr 2013

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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