BVRCIC PHOTOMETRY OF V743 SAGITTARII - AN ACTIVE, VERY SHORT-PERIOD, TOTAL ECLIPSING W-URSAE-MAJORIS SYSTEM

A complete photometric analysis of BVRI photometry for the very short period W Ursae Majoris binary V743 Sagittarii is presented. Four epoch s of minimum light were determined fi om observations made during two primary and two secondary eclipses. Corrected values of four previous timings are also given. The period study yielded an improved ephemeris . However, a large (similar to 60,000 orbit) gap in the data precluded any definitive period analysis at this time. Standard magnitudes are reported. The light curves reveal that V743 Sgr is a G8-K0 spectral ty pe W-type W UMa system with a 22 minute time of constant light in the primary minimum. The light curves have a prominent asymmetry occurring in the maximum at phase 0.25. It is 6% higher than the maximum at pha se 0.75 in V magnitude. Our simultaneous light-curve solution yielded a component temperature difference of similar to 350 K, a mass ratio o f similar to 0.31, and a fill-out of similar to 10%. A large polar coo l star spot was calculated. Apparently, the system has rapidly changin g spot activity. This is indicated by a comparison of our previously p ublished 1989 curves with the present 1991 curves, which show a shallo wer primary eclipse and a reversal in the sense of the asymmetry in th e maxima (phase 0.75 higher).