Post common envelope binaries from SDSS. VIII, Evidence for disrupted magnetic braking
Schreiber, Matthias R., Gaensicke, B. T. (Boris T.), Rebassa-Mansergas, A., Gomez-Moran, A. Nebot, Southworth, J. (John), Schwope, A. D. (Axel D.), Müller, M., Papadaki, C., Pyrzas, S., Rabitz, A., Rodríguez-Gil, P., Schmidtobreick, Linda, Schwarz, R. (Robert), Tappert, Claus, Toloza, O., Vogel, J. and Zorotovic, M.. (2010) Post common envelope binaries from SDSS. VIII, Evidence for disrupted magnetic braking. Astronomy & Astrophysics, Vol.513 (No.L7). ISSN 0004-6361
WRAP_Gansicke_10_post_common_aa13990-10.pdf - Requires a PDF viewer such as GSview, Xpdf or Adobe Acrobat Reader
Official URL: http://dx.doi.org/10.1051/0004-6361/201013990
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 M and steeply drops towards higher mass secondary stars in the range of Msec = 0.25−0.4 M.
Conclusions. The decrease of the number of PCEBs at the fully convective boundary strongly suggests that the evolutionary timescales 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.
|Item Type:||Journal Article|
|Subjects:||Q Science > QB Astronomy|
|Divisions:||Faculty of Science > Physics|
|Library of Congress Subject Headings (LCSH):||Double stars, Low mass stars, Angular momentum, Cosmic magnetic fields|
|Journal or Publication Title:||Astronomy & Astrophysics|
|Official Date:||April 2010|
|Number of Pages:||4|
|Access rights to Published version:||Open Access|
|Funder:||Fondo Nacional de Desarrollo Científico y Tecnológico (Chile) (FONDECYT), European Southern Observatory (ESO), Deutsche Forschungsanstalt für Luft- und Raumfahrt (DLR)|
|Grant number:||1061199 (FONDECYT), 32080023 (ESO), FKZ 50OR0404 (DLR)|
Abazajian, K. N., Adelman-McCarthy, J. K., Agüeros, M. A., et al. 2009, ApJS,
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