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arXiv · 0812.2510

Post Common Envelope Binaries from SDSS. V: Four eclipsing white dwarf main sequence binaries

S. Pyrzas·B. T. Gänsicke·T. R. Marsh·A. Aungwerojwit·A. Rebassa-Mansergas·P. Rodríguez-Gil·J. Southworth·M. R. Schreiber·A. Nebot Gomez-Moran·D. Koester
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Abstract

We identify SDSS011009.09+132616.1, SDSS030308.35+005444.1, SDSS143547.87+373338.5 and SDSS154846.00+405728.8 as four eclipsing white dwarf plus main sequence (WDMS) binaries from the Sloan Digital Sky Survey, and report on follow-up observations of these systems. Orbital periods and ephemerides have been established from multi-season photometry. SDSS1435+3733, with Porb=3h has the shortest orbital period of all known eclipsing WDMS binaries. Time-resolved spectroscopic observations have been obtained and the radial velocities of the secondary stars in all four systems were measured. A spectral decomposition/fitting technique was then employed to determine the white dwarf effective temperatures and surface gravities, as well as the spectral types of the companion stars. We used a light curve modeling code to further constrain the masses and radii of the components in all systems. All three DA white dwarfs have masses of Mwd~0.4-0.6Msun, in line with the expectations from close binary evolution. The DC white dwarf in SDSS0303+0054 has a mass of Mwd>0.85Msun, making it unusually massive for a post-common envelope system. Our new additions raise the number of known eclipsing WDMS binaries to fourteen, and we find that the average white dwarf mass in this sample is =0.57+/-0.16Msun, only slightly lower than the average mass of single white dwarfs. The majority of all eclipsing WDMS binaries contain low-mass (<0.6Msun) secondary stars, and will eventually provide valuable observational input for the calibration of the mass-radius relations of low-mass main sequence stars and of white dwarfs.

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S. Pyrzas, B. T. Gänsicke, T. R. Marsh, A. Aungwerojwit, A. Rebassa-Mansergas, P. Rodríguez-Gil, J. Southworth, M. R. Schreiber, A. Nebot Gomez-Moran, D. Koester. 2008-12-15. Post Common Envelope Binaries from SDSS. V: Four eclipsing white dwarf main sequence binaries. https://doi.org/10.1111/j.1365-2966.2008.14378.x

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