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Astrophysics and Space Science

, Volume 240, Issue 2, pp 317–329 | Cite as

A model of light-curve synthesizing for dwarf novae and the analysis of the OY Car observations by application of the inverse-problem method

  • Gojko Djurašević
Article

Abstract

The paper contains a model synthesizing the light curves of novae and novae-like stars, as well as of active close binaries (CB) in the phase of an intensive matter exchange between the components with accretion onto a white dwarf. The model considers the radial and azimuthal temperature distributions in the disk enabling a successful interpretation of asymmetrically deformed light curves characteristic for these systems. The analysis of the observed light curves is performed by using the inverse-problem method (Djurašević, 1992b) adapted to this model. In the particular case the parameters for the dwarf-novaOY Car are estimated on the basis of the U and B observations (Woodet al., 1989).

The synthetic light curves obtained through the inverse-problem solving, as a whole, fit the observations well which indicates that it is possible to estimate the system parameters on the basis of the model proposed here.

The obtained results indicate a complex hot-spot structure approximated in the model with two components—a central part and a surrounding spot larger in size. The central hot-spot part (temperature about 10000 K is surrounded asymmetrically by the larger spot lower in temperature (about 7000 K). The radiation of the central hot spot is ‘beamed’ forward by about 20°. The angular size of the hot-spot central part is about 5°, the centre longitude is 322°, whereas for the surrounding spot the size is about 33° and the longitude of the centre about 300°.

For the mass ratio of the componentsq=0.102 one finds for the orbit inclination about 83°.8. The analysis shows that the disk radius is about 51% of the corresponding Roche lobe radius.

Based on the U and B light curves the quiescent disk-edge temperature is estimated to about 5500 K (U), i.e. 4400 K (B). The disk-radial-temperature profile is much flatter than in the steady-state-approximation case. Beginning from the edge towards the disk centre the temperature slowly increases attaining about 7200 K (U), i.e. 5700 K (B) near the white dwarf. The differences in the solutions for the U and B light curves can be due to deviations in the disk radiation from the black-body approximation assumed in the present model. Expressed in the units of the distance between the component centres [D=1] the disk size is estimated to about 0.304 [D=1], its thickness to 0.014 [D=1], and the white-dwarf radius to about 0.02 [D=1]. The white-dwarf temperature is about 15000 K.

The obtained results are in a relatively good agreement with the system parameters estimated earlier (Woodet al., 1989). This indicates that the proposed model of the system and the corresponding inverse-problem method briefly presented here are fully applicable to the analysis of active CB light curves in this evolutionary phase. Though the model given here includes a number of approximations, it enables an independent procedure in the observational-material analysis based on the light-curve synthesis and on the application of the inverse-problem method. Results obtained by applying such an independent method can also serve as a reasonable way in testing the solutions obtained by utilising the earlier approaches.

Keywords

Light Curf Observation Well White Dwarf Orbit Inclination Close Binary 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

  1. Djurašević, G.: 1992a,Astrophys. Space Science 196, 267.Google Scholar
  2. Djurašević, G.: 1992b,Astrophys. Space Science 197, 17.Google Scholar
  3. Verbunt, F.: 1982,Space Sci. Rev. 32, 379.Google Scholar
  4. Wood, J. H., Horne, K., Berriman, G. and Wade, R. A.: 1989,Astrophys. J. 341, 974.Google Scholar

Copyright information

© Kluwer Academic Publishers 1996

Authors and Affiliations

  • Gojko Djurašević
    • 1
  1. 1.Astronomical ObservatoryBelgradeYugoslavia

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