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 Interam erican Observatory (Chile). A period study shows that the one previous ly known from photographic data (0.d32885) must be corrected to 0.d393 67. The analysis for all minima, including our photoelectric data, ind icates a variable period that is decreasing at a rate of d ln P/dt = - 6.40(+/-0.22) x 10(-7) yr-1. The period change, interpreted as conserv ative transfer of matter, gives d ln M/dt = 8.19 x 10(-8) yr-1 from th e primary to the secondary component. The differential light curves sh ow LT Pav to be a W UMa system with a flat secondary minimum correspon ding to a total eclipse of 30 minutes duration and therefore belonging to the A-type subclass. Absolute UBV photometry and an estimate of th e reddening E(B - V) = 0.m04 permits to assign a composite spectrum F8 -type to the system. A preliminary estimate of the mass-ratio (q almos t-equal-to 0.34) and the degree of overcontact (f almost-equal-to 0.3 - 0.4) shows LT Pav to be a well behaved A-type system with a suggesti on of a moderate evolved stage of evolution.