PHL 1445: an eclipsing cataclysmic variable with a substellar donor near the period minimum

We present high-speed, three-colour photometry of the eclipsing dwarf nova PHL 1445, which, with an orbital period of 76.3 min, lies just below the period minimum of ∼82 min for cataclysmic variable stars (CVs). Averaging four eclipses reveals resolved eclipses of the white dwarf and bright spot. We...

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Published in:Monthly notices of the Royal Astronomical Society 2015-07, Vol.451 (1), p.114-125
Main Authors: McAllister, M. J., Littlefair, S. P., Baraffe, I., Dhillon, V. S., Marsh, T. R., Bento, J., Bochinski, J., Bours, M. C. P., Breedt, E., Copperwheat, C. M., Hardy, L. K., Kerry, P., Parsons, S. G., Rostron, J. W., Sahman, D. I., Savoury, C. D. J., Tunnicliffe, R. L.
Format: Article
Language:English
Subjects:
Astronomy
Brown dwarf stars
Brown dwarfs
Cataclysmic variables
Eclipses
Evolutionary
Light curve
Mass ratios
Photometry
Stars & galaxies
Temperature
White dwarf stars
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Summary:We present high-speed, three-colour photometry of the eclipsing dwarf nova PHL 1445, which, with an orbital period of 76.3 min, lies just below the period minimum of ∼82 min for cataclysmic variable stars (CVs). Averaging four eclipses reveals resolved eclipses of the white dwarf and bright spot. We determined the system parameters by fitting a parametrized eclipse model to the averaged light curve. We obtain a mass ratio of q = 0.087 ± 0.006 and inclination i = 85 $_{.}^{\circ}$ 2 ± 0 $_{.}^{\circ}$ 9. The primary and donor masses were found to be M w = 0.73 ± 0.03 M⊙ and M d = 0.064 ± 0.005 M⊙, respectively. Through multicolour photometry a temperature of the white dwarf of T w = 13 200 ± 700 K and a distance of 220 ± 50 pc were determined. The evolutionary state of PHL 1445 is uncertain. We are able to rule out a significantly evolved donor, but not one that is slightly evolved. Formation with a brown dwarf donor is plausible, though the brown dwarf would need to be no older than 600 Myr at the start of mass transfer, requiring an extremely low mass ratio (q = 0.025) progenitor system. PHL 1445 joins SDSS 1433 as a sub-period minimum CV with a substellar donor. The existence of two such systems raises an alternative possibility that current estimates for the intrinsic scatter and/or position of the period minimum may be in error.
ISSN:0035-8711
1365-2966
DOI:10.1093/mnras/stv956