The periodic orbits in circular restricted 3-body problem are calculated by different numerical as well as analytical methods. The efficiency of both kinds are compared in this contribution. The improvement of analytical methods can be achieved by an artificial splitting of perturbation term. The analytical approximations are thus sufficiently accurate even for large values of mass ratio μ. The use of these approximations as a zero-order approximation In numerical codes for search for periodic orbits improves their efficiency also.
FOTEL 4 is a FORTRAN code for separate or simultaneous solving of light curves, radial-velocity curves, visual (interferometric) measurements and eclipse timing of binary and/or triple stellar systems. The underlying physical assumptions, numerical methods and practical use of the code are described in this document.
The code KOREL for Fourier disentangling (i.e. simultaneous decomposition of component spectra and solution of orbital elements) and lime-photometry of binary and multiple stars is described together with auxiliary codes PREKOR, KORNOR etc.
Models of stellar atmospheres are based on assumption of their plane-parallel or spherical symmetry. Violation of this assumption by tides and rotation in close binaries leads to incompatibility of hydrostatic and radiative equilibria. Improvement of model atmospheres in this respect is desirable for simulation of light curves and line profile changes. Moreover, atmospheres of
contact components of interacting binaries determine initiai conditions of dynamics of gaseous streams and in this way influence the behaviour of the binary system.