M. Zorotovic, M. R. Schreiber, B. T. Gänsicke, A. Rebassa-Mansergas, A. Nebot Gómez-Morán, J. Southworth, A. D. Schwope, S. Pyrzas, P. Rodríguez-Gil, L. Schmidtobreick, R. Schwarz, C. Tappert, O. Toloza, N. Vogt
Post-common-envelope binaries (PCEBs) consisting of a white dwarf (WD) and a
main-sequence secondary star are ideal systems to constrain models of
common-envelope (CE) evolution. Until very recently, observed samples of PCEBs
have been too small to fully explore this potential, however the recently
identified large and relatively homogenous sample of PCEBs from the Sloan
Digital Sky Survey (SDSS) has significantly changed this situation. We here
analyze the orbital period distributions of PCEBs containing He- and C/O-core
WDs separately and investigate whether the orbital period of PCEBs is related
to the masses of their stellar components. We performed standard statistical
tests to compare the orbital period distributions and to determine the
confidence levels of possible relations. The orbital periods of PCEBs
containing He-core WDs are significantly shorter than those of PCEBs containing
C/O-core WDs. While the He-core PCEB orbital period distribution has a median
value of Porb ~ 0.28 d, the median orbital period for PCEBs containing C/O-core
WDs is Porb ~ 0.57 d. We also find that systems containing more massive
secondaries have longer post-CE orbital periods, in contradiction to recent
predictions. Our observational results provide new constraints on theories of
CE evolution. However we suggest future binary population models to take
selection effects into account that still affect the current observed PCEB
sample.
View original:
http://arxiv.org/abs/1111.2512
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