DIFFERENTIAL CORRECTIONS ANALYSIS OF THE UBV OBSERVATIONS OF LT PAVONIS

The first photoelectric analysis of the W UMa system LT Pav, based on U, B and V light curves, is presented. The light curves are modeled us ing the Wilson-Devinney approach. Single passband and multi passband s olutions made with normal points against those obtained using individu al observations are compared. Solutions were performed keeping the gra vity darkening exponent fixed, and the effects of letting it vary with the rest of the main adjustable parameters from a ''conservative'' co nverged solution, or from the beginning of the solution are investigat ed. The main results are that iterations should be continued until all adjustable parameters stabilize, and that a solution can be found sta rting with normal points and switching afterwards to individual observ ations without lost of accuracy and reaching convergence in a few iter ations. Two final solutions are found. One is characterized mainly by a high g and a low degree of overcontact, the other by the opposite. T he primary (more massive) component is in a moderate stage of evolutio n based in its mean density and color. Preliminary absolute dimensions are derived. The radius of the primary exceeds that of a normal MS st ar of the same effective temperature by 17% if the temperature correct ion due to luminosity transfer is considered, and by 30% if the correc tion is not taken into account. LT Pav would be a W UMa system with th e most massive primary known to date, if the absolute dimensions can b e confirmed.