The A-Type W UMa System LT Pav: Period Study and UBV Light Curves

The first photoelectric light and color curves of the eclipsing binary LT Pav were determined from observations made at Cerro Tololo Interamerican Observatory (Chile). A period study shows that the one previously known from photographic data (0.32885 d) must be corrected to 0.39367d. The analysis for all minima, including our photoelectric data, indicates a variable period that is decreasing at a rate of d(ln P)/dt=-6.40(pm0.22) times 10^{-7} yr^{-1}. The period change, interpreted as conservative transfer of matter, gives d(ln M)/dt=8.19 times 10^{-8} yr^{-1} from the primary to the secondary component. The differential light curves show LT Pav to be a W UMa system with a flat secondary minimum corresponding to a total eclipse of 30 minutes duration and therefore belonging to the A-type subclass. Absolute UBV photometry and an estimate of the reddening E(B-V)=0.04 mag permits to assign a composite spectrum F8-type to the system. A preliminary estimate of the mass-ratio (q approx 0.34) and the degree of overcontact (f approx 0.3-0.4) shows LT Pav to be a well behaved A-type system with a suggestion of a moderate evolved stage of evolution.