Open AccessHST and ground‐based eclipse observations of V2051 Ophiuchi: binary parameters
Author(s) -
Baptista Raymundo,
Catalán M. S.,
Horne Keith,
Zilli D.
Publication year - 1998
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.1998.01887.x
Subject(s) - physics , light curve , astrophysics , white dwarf , photometry (optics) , astronomy , brightness , dwarf nova , eclipse , mass ratio , binary star , stars , emission spectrum , spectral line , radial velocity
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 Å. 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 K 1 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.