Up: The early type contact
The Wilson & Devinney (1971) method was applied in solving the present
light curves of V382 Cygni. This method has been described by many
authors. For our solutions, the revised version of the program
(Wilson 1992) was used. The method assumes the star surfaces to be
equipotentials and computes the light curves as a function
of the following parameters: the orbital inclination i, surface potentials
, flux-weighted average surface temperatures
,
mass ratio
, unnormalized monochromatic luminosities
, linear limb-darkening coefficients
, gravity
darkening exponents
, and bolometric albedos
.
Throughout this paper, the subscripts h and c refer to the
primary (hotter) and secondary (cooler) component, respectively.
For the solution of the present light curves, first the independent
sets of B and V observations made at two observatories were combined
after normalization to form single B and V light curves. The observational points
in each B and V light curves were then combined into normal points and weighted directly
according to the number of individual observations including
in a point. The temperature of the primary component was taken from
Morton & Adams (1968) as equal to 36100 K,
corresponding to the O6.5 spectral class given by
Pearce (1952).
This temperature is in accord with the discussion in
Hilditch et al. (1996)
and in Harries et al. (1997).
The linear limb darkening coefficients were taken from
Wade & Rucinski (1985), the gravity darkening exponents and the
bolometric albedos were set to be equal to 1.0 for
radiative atmospheres. These parameters were kept constant
during the iterations.
![\begin{figure}
\includegraphics[width=8cm,clip]{fig2.eps}\vspace*{2mm}
\end{figure}](/articles/aas/full/1999/02/ds7633/Timg33.gif) |
Figure 2:
The behavior as a function
of the mass ratio q |
The spectroscopic mass ratio of the system was given by
Pearce (1952) as
.
Popper & Hill (1991)
and Harries et al. (1997) obtained slightly different values for
the mass ratio as 0.70 and 0.74, respectively.
Therefore, we decided to apply a q-search procedure for
determining the photometric mass ratio of the system. For this, the B and V
light curves were solved simultaneously by choosing i,
,
,
as adjustable parameters.
The analysis was made with contact configuration (i.e. MODE 3).
The weighted sum of the squared residuals
for the corresponding mass ratios are shown in Fig. 2. As can
be seen from the figure, the lowest value of
around q=0.68 supports the spectroscopic mass ratio (q=0.702)
given by Popper & Hill (1991), which was used subsequently as
a starting input parameter in the solutions. The convergent
simultaneous solutions of the B and V light curves were obtained
with the free parameters by iterating until the corrections
on the parameters became smaller than the corresponding probable
errors. Because of the larger scatter in the U observations, the U
light curve has not been included in the analysis. The results of
the present analysis are given in Table 2. The theoretical light
curves calculated with the final elements obtained from simultaneous
solution of the combined B and V light curves are shown in Fig. 3 and 4
among four observational light curves (two in B, and two in V) from
two observatories. As seen from the figures, the agreements
between theoretical and observational light curves are very good. The
over contact configuration of V382 Cygni calculated with the
Roche model is shown in Fig. 5. The degree of overcontact is 22%.
![\begin{figure}
\includegraphics[width=8.8cm]{7633f3.eps}
\vspace*{1mm}\vspace*{2.5mm}
\end{figure}](/articles/aas/full/1999/02/ds7633/Timg40.gif) |
Figure 3:
EUO light curves of V382 Cygni. The upper panel shows
the theoretical B and V light curves (solid lines) formed
by Wilson-Devinney model among the observations obtained
at EUO, while the bottom panel shows the differences
between the observations and theoretical fits |
Table 2:
The results obtained by the method of Wilson-Devinney
 |
The absolute elements of the system were also obtained by
combining our photometric results and the spectroscopic elements
given by Harries et al. (1997). The results are given in Table 3.
Table 3:
The absolute elements of V382 Cygni
 |
![\begin{figure}
\includegraphics[width=8.8cm]{7633f4.eps}\vspace*{-5mm}
\end{figure}](/articles/aas/full/1999/02/ds7633/Timg43.gif) |
Figure 4:
AUO light curves of V382 Cygni. The upper panel shows
the theoretical B and V light curves (solid lines) formed
by Wilson-Devinney model among the observations obtained
at AUO, while the bottom panel shows the differences
between the observations and theoretical fits |
![\begin{figure}
\includegraphics[width=8.5cm,clip]{fig5.eps} \end{figure}](/articles/aas/full/1999/02/ds7633/Timg44.gif) |
Figure 5:
The Roche configuration of V382 Cygni for q=0.677 |
Up: The early type contact
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