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arXiv · 1704.01182

PTF1 J085713+331843, a new post common-envelope binary in the orbital period gap of cataclysmic variables

J. van Roestel·P. J. Groot·D. Levitan·T. A. Prince·S. Bloemen·T. R. Marsh·V. S. Dhillon·D. Shupe·R. Laher
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Abstract

We report the discovery and analysis of PTF1 J085713+331843, a new eclipsing post common-envelope detached white-dwarf red-dwarf binary with a 2.5h orbital period discovered by the Palomar Transient Factory. ULTRACAM multicolour photometry over multiple orbital periods reveals a light curve with a deep flat-bottomed primary eclipse and a strong reflection effect. Phase-resolved spectroscopy shows broad Balmer absorption lines from the DA white dwarf and phase-dependent Balmer emission lines originating on the irradiated side of the red dwarf. The temperature of the DA white dwarf is $T_\mathrm{WD} = 25700 \pm 400\,$K and the spectral type of the red dwarf is M3-5. A combined modelling of the light curve and the radial velocity variations results in a white dwarf mass of $M_\mathrm{WD} = 0.61^{+0.18}_{-0.17}\, \mathrm{M_{\odot}}$ and radius of $R_\mathrm{WD} = 0.0175^{+0.0012}_{-0.0011}\, \mathrm{R_{\odot}}$, and a red dwarf mass and radius of $M_\mathrm{RD} = 0.19^{+0.10}_{-0.08}\, \mathrm{M_{\odot}}$ and $R_\mathrm{RD} = 0.24^{+0.04}_{-0.04}\, \mathrm{R_{\odot}}$. The system is either a detached cataclysmic variable or has emerged like from the common envelope phase at nearly its current orbital period. In $\sim70\,$Myr, this system will become a cataclysmic variable in the period gap.

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J. van Roestel, P. J. Groot, D. Levitan, T. A. Prince, S. Bloemen, T. R. Marsh, V. S. Dhillon, D. Shupe, R. Laher. 2017-04-04. PTF1 J085713+331843, a new post common-envelope binary in the orbital period gap of cataclysmic variables. https://doi.org/10.1093/mnras%2Fstx625

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