HST and ground-based eclipse observations of V2051 Ophiuchi: binary parameters |
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| Authors: | Raymundo Baptista M S Catalán Keith Horne & D Zilli |
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| Institution: | Departamento de Física, Universidade Federal de Santa Catarina, Campus Trindade, 88040-900 Florianópolis —SC, Brazil,;Department of Physics, Keele University, Keele, Staffordshire ST5 5BG,;School of Physics &38;Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS |
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| Abstract: | We report on high-speed eclipse photometry of the dwarf nova V2051 Oph while it was in a low brightness state, at B ? 16.2 mag. In comparison with the average IUE spectra, the ultraviolet continuum and emission lines appear reduced by factors of, respectively, ? 4 and ? 5. Flickering activity is mostly suppressed and the light curve shows the eclipse of a compact white dwarf at the disc centre which contributes ? 60 per cent of the total light at 3900–4300 ?. We use measurements of contact phases in the eclipse light curve to derive the binary geometry and to estimate masses and relevant dimensions. We find a mass ratio of q = 0.19 ± 0.03 and an inclination of i = 83 ± 2°. The masses of the component stars are M 1 = 0.78 ± 0.06 M⊙ and M 2 = 0.15 ± 0.03 M⊙. Our photometric model predicts K 1 = 83 ± 12 km s?1 and K 2 = 436 ± 11 km s?1. The predicted value of K1 is in accordance with the velocity amplitude obtained from the emission lines after a correction for asymmetric line emission in the disc is made. The secondary of V2051 Oph is significantly more massive than the secondaries of the other ultrashort period dwarf novae. V2051 Oph is probably a relatively young system, with a secondary star that has not had enough time to evolve out of thermal equilibrium. |
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| Keywords: | eclipses binaries: close stars: individual: V2051 Oph novae cataclysmic variables ultraviolet: stars |
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