Discovery of the spectroscopic binary nature of three bright southern Cepheids

L. Szabados, R. I. Anderson, A. Derekas, L. L. Kiss, T. Szalai, P. Székely, J. L. Christiansen

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5 Citations (Scopus)


We present an analysis of spectroscopic radial velocity and photometric data of three bright Galactic Cepheids: LR Trianguli Australis (LR TrA), RZ Velorum (RZ Vel) and BG Velorum (BG Vel). Based on new radial velocity data, these Cepheids have been found to be members of spectroscopic binary systems. The ratio of the peak-to-peak radial velocity amplitude to photometric amplitude indicates the presence of a companion for LR TrA and BG Vel. IUE spectra indicate that the companions of RZ Vel and BG Vel cannot be hot stars. The analysis of all available photometric data revealed that the pulsation period of RZ Vel and BG Vel varies monotonically, due to stellar evolution. Moreover, the longest period Cepheid in this sample, RZ Vel, shows period fluctuations superimposed on the monotonic period increase. The lighttime effect interpretation of the observed pattern needs long-term photometric monitoring of this Cepheid. The pulsation period of LR TrA has remained constant since the discovery of its brightness variation. Using statistical data, it is also shown that a large number of spectroscopic binaries still remain to be discovered among bright classical Cepheids.

Original languageEnglish
Pages (from-to)870-877
Number of pages8
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
Publication statusPublished - Sep 1 2013


  • Binaries: spectroscopic
  • Stars: variables: cepheids

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Szabados, L., Anderson, R. I., Derekas, A., Kiss, L. L., Szalai, T., Székely, P., & Christiansen, J. L. (2013). Discovery of the spectroscopic binary nature of three bright southern Cepheids. Monthly Notices of the Royal Astronomical Society, 434(1), 870-877.