Post common envelope binaries from the SDSS

Schwope, A. D.; Gómez‐Morán, A. Nebot; Schreiber, M. R.; Gänsicke, B. T.

doi:10.1051/0004-6361/200911699

Cited by 50 publications

(59 citation statements)

References 36 publications

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“…Important in this respect, SDSS has not only provided a deep sample of CVs, but also the first-ever large homogeneous population of detached white-dwarf/main-sequence (WDMS) binaries (e.g., Silvestri et al 2007;Rebassa-Mansergas et al 2010) of which a considerable fraction, ∼30%, are PCEBs (Rebassa-Mansergas et al 2007, 2010Schreiber et al 2008;Nebot Gómez-Morán et al 2009Pyrzas et al 2009;Schwope et al 2009). Those PCEBs that will evolve into semidetached binaries undergoing stable mass transfer on timescales shorter than the age of the Galaxy are representative of the progenitors of the current-day CV population.…”

Section: Introductionmentioning

confidence: 99%

Post common envelope binaries from SDSS

Zorotovic

Schreiber

Gänsicke

2011

A&A

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Context. We have known for a long time that many of the measured white dwarf (WD) masses in cataclysmic variables (CVs) significantly exceed the mean mass of single WDs. This was thought to be related to observational biases, but recent high-precision measurements of WD masses in a great number of CVs are challenging this interpretation. A crucial question in this context is whether the high WD masses seen among CVs are already imprinted in the mass distribution of their progenitors, i.e. among detached postcommon-envelope binaries (PCEBs) that consist of a WD and a main-sequence star. Aims. We review the measured WD masses of CVs, determine the WD-mass distribution of an extensive sample of PCEBs that are representative for the progenitors of the current CV population (pre-CVs) and compare both distributions. Methods. We calculate the CV formation time of the PCEBs in our sample by determining the post common-envelope (CE) and the main-sequence evolution of the binary systems and define a pre-CV to be a PCEB that evolves into a semi-detached configuration with stable mass transfer within less than the age of the Galaxy. Possible observational biases affecting the WD-mass distribution for the pre-CV and the CV samples are discussed. Results. The mean WD mass among CVs is M wd = 0.83 ± 0.23 M , much larger than that found for pre-CVs, M wd = 0.67 ± 0.21 M . Selection effects cannot explain the high WD masses observed in CVs. We also note that compared to the predictions of binary-population models, the observed fraction of He-core WDs is small both among CVs (≤10%) and pre-CVs (≤17 ± 8%). Conclusions. We suggest two possible explanations for the high WD masses among CVs, both of which imply substantial revisions to the standard model of CV evolution: either most CVs have formed above the orbital-period gap (which requires a high WD mass to initiate stable mass transfer or a previous phase of thermal-timescale mass transfer), or the mass of the WDs in CVs grows through accretion (which strongly disagrees with the predictions of classical nova models). Both options may imply that CVs contribute to the single-degenerate progenitors of type Ia supernovae. The number of He-core WDs in CVs (≤10%) is roughly consistent with the number of He-core WDs in pre-CVs (≤17 ± 8%). This indicates a low value of the CE efficiency.

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Section: Introductionmentioning

confidence: 99%

Post common envelope binaries from SDSS

Zorotovic

Schreiber

Gänsicke

2011

A&A

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300

336

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“…We have initiated an intensive follow-up study of the SDSS WDMS binaries, with the ultimate aim to substantially improve our understanding of compact binary evolution. First results on individual systems and small subsets of this sample have been published Rebassa-Mansergas et al 2008;Nebot Gómez-Morán et al 2009;Pyrzas et al 2009;Schwope et al 2009), as well as several studies that analyse the total sample in the context of close binary evolution Zorotovic et al 2010;Rebassa-Mansergas et al 2011b). Here we present one of the fundamental results of this project: the orbital period distribution of 79 SDSS WDMS binaries, which we discuss in the context of current theories of compact binary evolution.…”

Section: Introductionmentioning

confidence: 99%

Post common envelope binaries from SDSS

Gómez‐Morán

Gänsicke

Schreiber

et al. 2011

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131

113

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Context. The complexity of the common-envelope phase and of magnetic stellar wind braking currently limits our understanding of close binary evolution. Because of their intrinsically simple structure, observational population studies of white dwarf plus main sequence (WDMS) binaries can potentially test theoretical models and constrain their parameters. Aims. The Sloan Digital Sky Survey (SDSS) has provided a large and homogeneously selected sample of WDMS binaries, which we characterise in terms of orbital and stellar parameters. Methods. We have obtained radial velocity information for 385 WDMS binaries from follow-up spectroscopy and for an additional 861 systems from the SDSS subspectra. Radial velocity variations identify 191 of these WDMS binaries as post common-envelope binaries (PCEBs). Orbital periods of 58 PCEBs were subsequently measured, predominantly from time-resolved spectroscopy, bringing the total number of SDSS PCEBs with orbital parameters to 79. Observational biases inherent to this PCEB sample were evaluated through extensive Monte Carlo simulations. Results. We find that 21-24% of all SDSS WDMS binaries have undergone common-envelope evolution, which is in good agreement with published binary population models and high-resolution HST imaging of WDMS binaries unresolved from the ground. The bias-corrected orbital period distribution of PCEBs ranges from 1.9 h to 4.3 d and approximately follows a normal distribution in log(P orb ), peaking at ∼10.3 h. There is no observational evidence for a significant population of PCEBs with periods in the range of days to weeks. Conclusions. The large and homogeneous sample of SDSS WDMS binaries provides the means to test fundamental predictions of binary population models, hence to observationally constrain the evolution of all close compact binaries.

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“…A more detailed disquisition of the evolutionary status of the pre-polars as a class can be found e.g. in Schmidt et al (2007) or Schwope et al (2009). The sample is still rather small and due to the intrinsic faintness of pre-polars not all properties can be determined for every system.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…The three systems which are never observed in X-rays (SDSS1031, SDSS1059 and SDSS1206) are unlikely to provide sufficient X-ray flux due to their large distance. Nevertheless the cyclotron properties imply a low plasma temperature of ∼1 keV (Schmidt et al 2007;Schwope et al 2009). …”

Section: Summary and Discussionmentioning

confidence: 99%

“…They are now regarded as pre-polars, i.e. as the progenitors of polars, with the secondary not yet in Roche-lobe contact that are accreting from the stellar wind of the secondary (Schmidt et al 2005;Webbink & Wickramasinghe 2005;Schwope et al 2009). Reimers & Hagen (2000) performed follow-up observations of HS0922+1333 with CAFOS at the 2.2 m telescope at Calar Alto Observatory.…”

Section: Introductionmentioning

confidence: 99%

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XMM-Newtonobservations of the pre-polar HS0922+1333

Vogel

Schwope

Schwarz

2011

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We report on XMM-Newton and accompanying phase-resolved optical observations of HS0922+1333, one out of nine pre-polars. It shows X-ray and UV variability correlated with the visibility of the main accretion spot. The spectral X-ray properties reveal a low temperature thermal plasma of ∼1 keV with F X more than one order of magnitude below the cyclotron flux. The UV data indicate a cool white dwarf with T WD < 8000 K. We refine the ephemeris and determine a distance of 140 ± 50 pc. The derived location of the accretion spots yield a magnetic field axis laying nearly in the orbital plane. Optical spectroscopy uncovers a highly active secondary.

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Post common envelope binaries from the SDSS

Cited by 50 publications

References 36 publications

Post common envelope binaries from SDSS

Post common envelope binaries from SDSS

Post common envelope binaries from SDSS

XMM-Newtonobservations of the pre-polar HS0922+1333

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