Journal Article

Post-common envelope binaries from SDSS – III. Seven new orbital periods

A. Rebassa-Mansergas, B. T. Gänsicke, M. R. Schreiber, J. Southworth, A. D. Schwope, A. Nebot Gomez-Moran, A. Aungwerojwit, P. Rodríguez-Gil, V. Karamanavis, M. Krumpe, E. Tremou, R. Schwarz, A. Staude and J. Vogel

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 390, issue 4, pages 1635-1646
Published in print November 2008 | ISSN: 0035-8711
Published online October 2008 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.13850.x
Post-common envelope binaries from SDSS – III. Seven new orbital periods

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We present follow-up spectroscopy and photometry of 11 post-common envelope binary (PCEB) candidates identified from multiple Sloan Digital Sky Survey (SDSS) spectroscopy in an earlier paper. Radial velocity measurements using the Na i λλ8183.27, 8194.81 absorption doublet were performed for nine of these systems and provided measurements of six orbital periods in the range Porb= 2.7– 17.4 h. Three PCEB candidates did not show significant radial velocity variations in the follow-up data, and we discuss the implications for the use of SDSS spectroscopy alone to identify PCEBs. Differential photometry confirmed one of our spectroscopic orbital periods and provided one additional Porb measurement. Binary parameters are estimated for the seven objects for which we have measured the orbital period and the radial velocity amplitude of the low-mass companion star, Ksec. So far, we have published nine SDSS PCEBs orbital periods, all of them Porb < 1 d. We perform Monte Carlo simulations and show that 3σ SDSS radial velocity variations should still be detectable for systems in the orbital period range of Porb∼ 1– 10 d. Consequently, our results suggest that the number of PCEBs decreases considerably for Porb > 1 d, and that during the CE phase the orbital energy of the binary star is may be less efficiently used to expel the envelope than frequently assumed.

Keywords: stars: AGB and post-AGB; binaries: close; binaries: spectroscopic; stars: evolution; stars: low-mass, brown dwarfs; white dwarfs

Journal Article.  8775 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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