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2000MNRAS.316..529B - Mon. Not. R. Astron. Soc., 316, 529-539 (2000/August-2)
Eclipse studies of the dwarf nova EX Draconis.
BAPTISTA R., CATALAN M.S. and COSTA L.
Abstract (from CDS):
New eclipse timings were measured from the light curves taken in quiescence and a revised ephemeris was derived. The residuals with respect to the linear ephemeris are well described by a sinusoid of amplitude 1.2min and period ≃4yr and are possibly related to a solar-like magnetic activity cycle in the secondary star. Eclipse phases of the compact central source and of the bright spot were used to derive the geometry of the binary. By constraining the gas stream trajectory to pass through the observed position of the bright spot, we find q=0.72±0.06 and {formmu1} degrees. The binary parameters were estimated by combining the measured mass ratio with the assumption that the secondary star obeys an empirical main-sequence mass-radius relation. We find M1=0.75±0.15M☉ and M2=0.54±0.10M☉. The results indicate that the white dwarf at disc centre is surrounded by an extended and variable atmosphere or boundary layer of at least three times its radius and a temperature of T≃28000K. The fluxes at mid-eclipse yield an upper limit to the contribution of the secondary star and lead to a lower limit photometric parallax distance of D=290±80pc. The fluxes of the secondary star are well-matched by those of a M0±2 main-sequence star.
Abstract Copyright: 2000, Royal Astronomical Society
Journal keyword(s): accretion, accretion discs - binaries: close - binaries: eclipsing - stars: individual: EX Dra - novae, cataclysmic variables 10.1046/j.1365-8711.2000.03523.x
Simbad objects: 4
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