Volume 536, December 2011
|Number of page(s)||4|
|Published online||06 December 2011|
Letter to the Editor
Post common envelope binaries from SDSS
XIII. Mass dependencies of the orbital period distribution
Departamento de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
2 Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Santiago, Chile
3 Department of Physics, University of Warwick, Coventry, CV4 7AL, UK
4 Université de Strasbourg, CNRS, UMR 7550, Observatoire Astronomique de Strasbourg, 11 rue de l’Université, 67000 Strasbourg, France
5 Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK
6 Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
7 Instituto de Astrofísica de Canarias, Vía Láctea, s/n, La Laguna, 38205 Tenerife, Spain
8 Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
9 European Southern Observatory, Alonso de Cordova 3107, Santiago, Chile
Received: 1 August 2011
Accepted: 8 November 2011
Context. 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.
Aims. 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.
Methods. We performed standard statistical tests to compare the orbital period distributions and to determine the confidence levels of possible relations.
Results. 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.
Conclusions. 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.
Key words: binaries: close / stars: low-mass / white dwarfs
© ESO, 2011
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