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The shortest period detached white dwarf + main-sequence binary

  1. S. G. Parsons1,*,
  2. T. R. Marsh1,
  3. B. T. Gänsicke1,
  4. V. S. Dhillon2,
  5. C. M. Copperwheat1,
  6. S. P. Littlefair2,
  7. S. Pyrzas1,
  8. A. J. Drake3,
  9. D. Koester4,
  10. M. R. Schreiber5,
  11. A. Rebassa-Mansergas5

Article first published online: 29 SEP 2011

DOI: 10.1111/j.1365-2966.2011.19691.x

Issue

Monthly Notices of the Royal Astronomical Society

Monthly Notices of the Royal Astronomical Society

Volume 419, Issue 1, pages 304–313, January 2012

Additional Information

How to Cite

Parsons, S. G., Marsh, T. R., Gänsicke, B. T., Dhillon, V. S., Copperwheat, C. M., Littlefair, S. P., Pyrzas, S., Drake, A. J., Koester, D., Schreiber, M. R. and Rebassa-Mansergas, A. (2012), The shortest period detached white dwarf + main-sequence binary. Monthly Notices of the Royal Astronomical Society, 419: 304–313. doi: 10.1111/j.1365-2966.2011.19691.x

Author Information

  1. 1

    Department of Physics, University of Warwick, Coventry CV4 7AL

  2. 2

    Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH

  3. 3

    California Institute of Technology, 1200 E. California Blvd, CA 91225, USA

  4. 4

    Institut für Theoretische Physik und Astrophysik, Universität Kiel, D-24098 Kiel, Germany

  5. 5

    Departmento de Física y Astronomía, Universidad de Valparaíso, Avenida Gran Bretana 1111, Valparaíso, Chile

* E-mail: steven.parsons@warwick.ac.uk

Publication History

  1. Issue published online: 13 DEC 2011
  2. Article first published online: 29 SEP 2011
  3. Accepted 2011 August 24. Received 2011 August 15; in original form 2011 June 24

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Keywords:

  • binaries: eclipsing;
  • stars: fundamental parameters;
  • stars: individual: CSS 03170;
  • stars: low-mass;
  • white dwarfs

ABSTRACT

We present high-speed ULTRACAM and SOFI photometry and X-shooter spectroscopy of the recently discovered 94-min orbital period eclipsing white dwarf/main-sequence binary SDSS J085746.18+034255.3 (CSS 03170) and use these observations to measure the system parameters. We detect a shallow secondary eclipse and hence are able to determine an orbital inclination of i = 85bsl000645 ± 0bsl000642. The white dwarf has a mass of 0.51 ± 0.05 M⊙ and a radius of 0.0247 ± 0.0008 R⊙. With a temperature of 35 300 ± 400 K the white dwarf is highly overinflated if it has a carbon–oxygen core; however, if it has a helium core then its mass and radius are consistent with evolutionary models. Therefore, the white dwarf in SDSS J085746.18+034255.3 is most likely a helium core white dwarf with a mass close to the upper limit expected from evolution. The main-sequence star is an M8 dwarf with a mass of 0.09 ± 0.01 M⊙ and a radius of 0.110 ± 0.004 R⊙ placing it close to the hydrogen burning limit. The system emerged from a common envelope ∼20 million years ago and will reach a semidetached configuration in ∼400 million years, becoming a cataclysmic variable with a period of 66 min, below the period minimum.

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