Minimum on the light curve of the classical symbiotic star AS 338 in 1999

We present our UBVRI photometry and spectroscopy of AS 338 performed in 199 9-2000. Another eclipse of the hot component in this symbiotic binary syste m, the deepest one ever observed, occurred in September 1999. The U brightn ess declined by similar to2"', the H beta flux decreased by a factor of sim ilar to2.3, and the [O III] lambda 5007 flux did not change. The hot compon ent is eclipsed at orbital phases phi = 0.045-0.057. The U-B color index be gins to appreciably fluctuate during an eclipse of the hot component and it s circumstellar envelope. About 100 days after a strong outburst of 1995, t he mean UBV brightness of AS 338 declined linearly in the ensuing five year s at the same rate in all bands (DeltaU/Deltat approximate to 10(-3) mag/da y). The brightness of the outer, uneclipsed parts of the circumstellar enve lope also decreased, which is attributable to a reduction in the luminosity of the hot component against the rise in its temperature. The appearance o f He II lines has not yet been recorded, though the optical brightness of A S 338 has already dropped by similar to2"' after the outburst. (C) 2001 MAI K "Nauka/Interperiodica".