Abstract
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 lambda lambda 8183.27, 8194.81 absorption doublet were performed for nine of these systems and provided measurements of six orbital periods in the range P-orb = 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 P-orb 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, K-sec. So far, we have published nine SDSS PCEBs orbital periods, all of them P-orb 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.
Highlights
Most of the stellar sources are formed as parts of binary or multiple systems
The total sample of post common envelope binary (PCEB) contains only six systems with orbital periods larger than one day (∼15% of the entire sample). This suggests that the number of PCEBs decreases for Porb > 1 day, implying that the γ algorithm in its present form might not be an adequate description of the CE phase, and that the common envelope efficiency in the energy equation used in the α prescription is perhaps smaller than assumed previously
We have presented a study of 11 PCEB previously identified candidates, and measured the orbital periods of six and one of them from their Na I doublet radial velocity variations and its differential photometry, respectively
Summary
Most of the stellar sources are formed as parts of binary or multiple systems. the study of binary star evolution represents an important part of studying stellar evolution. The scenario outlined above is thought to be a fundamental formation channel for a wide range of astronomical objects such as low-mass X-ray binaries, double degenerate white dwarfs, neutron star binaries, cataclysmic variables and super-soft X-ray sources. Some of these objects will eventually end their lives as type Ia supernovae and short gamma-ray bursts, which are of great importance for cosmological studies. PCEBs consisting of a white dwarf and a main sequence star are a very well-suited class of objects to provide the required innovative observational input since they are numerous, well understood in terms of their stellar components, they are bright and accessible with 2–8 metre telescopes, and their study is not complicated by mass transfer. We present follow-up observations of 11 PCEB candidates identified in Rebassa-Mansergas et al (2007) and provide accurate values of the orbital periods as well as estimates of their stellar parameters and orbital inclinations for seven of these systems
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