Year: 2010
Type: article
Abstract: Context. The standard prescription of angular momentum loss in compact binaries assumes magnetic braking to be very efficient as long as the secondary star has a radiative core, but to be negligible if the secondary star is fully convective. This prescription has been developed to explain the orbital period gap observed in the orbital period distribution of cataclysmic variables but has so far not been independently tested. Because the evolutionary time-scale of post common envelope binaries (PCEBs) crucially depends on the rate of angular momentum loss, a fundamental prediction of the disrupted magnetic braking theory is that the relative number of PCEBs should dramatically decrease for companion-star masses exceeding the mass that corresponds to the fully-convective boundary. Aims. We present the results of a large survey of PCEBs among white dwarf/main sequence (WDMS) binaries that allows us to determine the fraction of PCEBs as a function of secondary star mass and therewith to ultimately test the disrupted magnetic braking hypothesis. Methods. We obtained multiple spectroscopic observations spread over at least two nights for 670 WDMS binaries. Systems showing at least 3σ radial velocity variations are considered to be strong PCEB candidates. Taking into account observational selection effects we compare our results with the predictions of binary population simulations.Results. Among the 670 WDMS binaries we find 205 strong PCEB candidates. The fraction of PCEBs among WDMS binaries peaks around Msec ~ 0.25 and steeply drops towards higher mass secondary stars in the range of Msec = 0.25–0.4 . Conclusions. The decrease of the number of PCEBs at the fully convective boundary strongly suggests that the evolutionary time scales of PCEBs containing fully convective secondaries are significantly longer than those of PCEBs with secondaries containing a radiative core. This is consistent with significantly reduced magnetic wind braking of fully convective stars as predicted by the disrupted magnetic braking scenario.
Source: Astronomy and Astrophysics
Institutions: University of Valparaíso, University of Warwick, Leibniz Institute for Astrophysics Potsdam, Keele University, National Observatory of Athens, Isaac Newton Group, Universidad de La Laguna, Instituto de Astrofísica de Canarias, European Southern Observatory, Pontificia Universidad Católica de Chile
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
Funders: National Science Foundation, U.S. Department of Energy, National Aeronautics and Space Administration, Alfred P. Sloan Foundation, Princeton University, Ohio State University, California Institute of Technology, University of Washington, Johns Hopkins University, University of Pittsburgh, Case Western Reserve University, Drexel University, Universität Basel, University of Portsmouth, New Mexico State University, Deutsche Forschungsgemeinschaft, Chinese Academy of Sciences, Ministerio de Ciencia, Tecnología e Innovación Productiva, Max-Planck-Gesellschaft, Ministério da Ciência e Tecnologia, Instituto de Astrofísica de Andalucía, Max-Planck-Institut für Astronomie, Instituto de Astrofísica de Canarias, Science and Technology Facilities Council, Comisión Nacional de Investigación Científica y Tecnológica, U.S. Naval Observatory, Fermilab, Los Alamos National Laboratory
OpenAlex ID: W1970347135