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 1999-2000. Another eclipse of the hot component in this symbiotic binary system, the deepest one ever observed, occurred in September 1999. The U brightness declined by 2 mag, the H_beta flux decreased by a factor of 2.3, and the [O III] lambda 5007 flux did not change. The hot component is eclipsed at orbital phases phi = 0.045-0.057. The U-B color index begins to appreciably fluctuate during an eclipse of the hot component and its circumstellar envelope. About 100 days after a strong outburst of 1995, the mean UBV brightness of AS 338 declined linearly in the ensuing five years at the same rate in all bands (Delta U / Delta t = 10^{-3} mag/day). The brightness of the outer, uneclipsed parts of the circumstellar envelope also decreased, which is attributable to a reduction in the luminosity of the hot component against the rise in its temperature. The appearance of He II lines has not yet been recorded, though the optical brightness of AS 338 has already dropped by 2 mag after the outburst.