4. Determination of system parameters
In this section, the masses and , the radii and , the inclination i, the distance a of the two stars, the distance f of the inner Lagrangian point from the white dwarf, and the radius d of the disk in quiescence are calculated. First, the applied formulas are explained, then the parameters are calculated and discussed.
4.1. Functional context
The mass ratio can be described by the radial velocities
For the calculation of the inclination i we applied the LFIT code (Wolf et al, 1995), keeping the q -value calculated above. This code decomposes eclipse light curves by fitting an N-component light curve model to the observational data. In this case, the model light curve is subdivided into 4 components: The white dwarf, assumed to be a spherical object with radius ; the secondary depending on the mass ratio q and the inclination i, assuming Roche-geometry; the accretion disk, represented by the disk radius d and a radial intensity distribution; and last, the hot spot.
Furthermore, Kepler's third law combined with an empirical equation of Paczynski (1971)
yields a mass-radius relation of the secondary as a function of the orbital period P
For the white dwarf, the mass-radius relation of Nauenberg (1972) is applied
4.2. Calculation of the parameters
The parameters and their corresponding errors are calculated by a Monte-Carlo simulation. For this, 10 000 Gauss-distributed starting-values of and , and the orbital inclination i derived by the LFIT code are simulated. The error of the period is neglected. Assuming Roche geometry, the starting-values are taken and the following parameters are calculated together with their standard deviations:
- Mass ratio - Inclination - Distance f in units of a: - Distance - Mass - Mass - Radius - Radius - Relative mean radius of the disk in quiescence
© European Southern Observatory (ESO) 1997
Online publication: April 8, 1998