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Register a new userDetermination of Size of the Emitting Region in Eclipsing Cataclysmic Variable Stars
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The dependencies of the phase of eclipse of the white dwarfs centre and the durations of the ascending and descending branches of the light curve on the binary systems parameters were computed using the spherically-symmetric approximation and the more accurate model of the elliptical projection onto the celestial sphere of the companion (red dwarf) that fills its Roche lobe. The parameters of eclipses in the classical eclipsing polar OTJ 071126+440405 = CSS 081231:071126+440405 were estimated.
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We discuss a method for determination of the size of the emitting region close to the compact star in a binary system with eclipses by a secondary, which fills its Roche lobe. The often used approach is to model the Roche lobe by a sphere with the effective radius corresponding to the volume of the Roche lobe. This approach leads to a 4-6% overestimate of the radius, if taking into account the angular dimensions of the Roche lobe seen form the compact star. Andronov (1992) had shown that the projection of the Roche lobe onto the celestial sphere is close to an ellipse and had tabulated these dimensions as a function of the mass ratio. Also he published the coefficients of the approximation similar to that of the Eggleton (1983) for the sphere corresponding to the same volume. We compare results obtained for the circle+circle, ellipse+circle and ellipse+point approximations of the projections of the red dwarf and a white dwarf, respectively. Results are applied to the recently discovered eclipsing polar CSS 081231:071126+440405.
We conducted a spectroscopic and photometric study of SDSS J075653.11+085831. X-ray observations were also attempted. We determined the orbital period of this binary system to be 3.29 hr. It is a deep eclipsing system, whose spectra shows mostly single-peaked Balmer emission lines and a rather intense He II line. There is also the presence of faint (often double-peaked) He I emission lines as well as several absorption lines, Mg I being the most prominent. All of these features point towards the affiliation of this object with the growing number of SW~Sex-type objects. We developed a phenomenological model of an SW~Sex system to reproduce the observed photometric and spectral features.
We present the results of an analysis of data covering 1.5 years of the dwarf nova V447 Lyr. We detect eclipses of the accretion disk by the mass donating secondary star every 3.74 hrs which is the binary orbital period. V447 Lyr is therefore the first dwarf nova in the Kepler field to show eclipses. We also detect five long outbursts and six short outbursts showing V447 Lyr is a U Gem type dwarf nova. We show that the orbital phase of the mid-eclipse occurs earlier during outbursts compared to quiescence and that the width of the eclipse is greater during outburst. This suggests that the bright spot is more prominent during quiescence and that the disk is larger during outburst than quiescence. This is consistent with an expansion of the outer disk radius due to the presence of high viscosity material associated with the outburst, followed by a contraction in quiescence due to the accretion of low angular momentum material. We note that the long outbursts appear to be triggered by a short outburst, which is also observed in the super-outbursts of SU UMa dwarf novae as observed using Kepler.
We report the discovery of a new eclipsing polar, CRTS J035010.7+323230 (hereafter CRTS J0350+3232). We identified this cataclysmic variable (CV) candidate as a possible polar from its multi-year Catalina Real-Time Transient Survey (CRTS) optical light curve. Photometric monitoring of 22 eclipses in 2015 and 2017 was performed with the 2.1-m Otto Struve Telescope at McDonald Observatory. We derive an unambiguous high-precision ephemeris. Strong evidence that CRTS J0350+3232 is a polar comes from optical spectroscopy obtained over a complete orbital cycle using the Apache Point Observatory 3.5-m telescope. High velocity Balmer and He II $lambda$4686{AA} emission line equivalent width ratios, structures, and variations are typical of polars and are modulated at the same period, 2.37-hrs (142.3-min), as the eclipse to within uncertainties. The spectral energy distribution and luminosity is found to be comparable to that of AM Herculis. Pre-eclipse dips in the light curve show evidence for stream accretion. We derive the following tentative binary and stellar parameters assuming a helium composition white dwarf and a companion mass of 0.2 M$_{odot}$: inclination i = 74.68$^{o}$ ${pm}$ 0.03$^{o}$, semi-major axis a = 0.942 ${pm}$ 0.024 R$_{odot}$, and masses and radii of the white dwarf and companion respectively: M$_{1}$ = 0.948 $^{+0.006}_{-0.012}$ M$_{odot}$, R$_{1}$ = 0.00830 $^{+0.00012}_{-0.00006}$ R$_{odot}$, R$_{2}$ = 0.249 ${pm}$ 0.002 R$_{odot}$. As a relatively bright (V $sim$ 17-19 mag), eclipsing, period-gap polar, CRTS J0350+3232 will remain an important laboratory for the study of accretion and angular momentum evolution in polars.
We report on the discovery of J0644+3344, a bright deeply eclipsing cataclysmic variable (CV) binary. Spectral signatures of both binary components and an accretion disk can be seen at optical wavelengths. The optical spectrum shows broad H I, He I, and He II accretion disk emission lines with deep narrow absorption components from H I, He I, Mg II and Ca II. The absorption lines are seen throughout the orbital period, disappearing only during primary eclipse. These absorption lines are either the the result of an optically-thick inner accretion disk or from the photosphere of the primary star. Radial velocity measurements show that the H I, He I, and Mg II absorption lines phase with the the primary star, while weak absorption features in the continuum phase with the secondary star. Radial velocity solutions give a 150+/-4 km/s semi-amplitude for the primary star and 192.8+/-5.6 km/s for the secondary. The individual stellar masses are 0.63-0.69 Mdot for the primary and 0.49-0.54 Mdot for the secondary. The bright eclipsing nature of this binary has helped provide masses for both components with an accuracy rarely achieved for CVs. This binary most closely resembles a nova-like UX UMa or SW Sex type of CV. J0644+3344, however, has a longer orbital period than most UX UMa or SW Sex stars. Assuming an evolution toward shorter orbital periods, J0644+3344 is therefore likely to be a young interacting binary. The secondary star is consistent with the size and spectral type of a K8 star, but has an M0 mass.
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