*Astron. Astrophys. 327, 173-182 (1997)*
## 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*
with the gravitational constant *G*. The relative distance
*f* of the inner Lagrangian point from the
white dwarf only depends on the mass ratio *q* (Warner, 1976;
Plavec, 1964)
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
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