Spectral and photometric observations of fast irregular variables

The results of observations on the irregular variable BN Ori are presented. They include photoelectric UBV brightness measurements covering the period 1966-1975, spectroscopic observations of Hsub(α) and Hsub(β) line profiles conducted with 20 Adeg/mm dispersion during 1971-1975 and photoelectric scans in the 3000-6000A deg spectral range carried out on January 10-11, 1972. UBV observations showed that the star has practically constant brightness. From photoelectric spectrum scans this star has been classified as F2. The absolute energy distribution in 3000-6000A range obtained from the observations is in good agreement with the distribution for F2V standard star in 4000-6000A range for Asub(v) = 0.sup(m).70, however, there is some excess of radiation in the ultraviolet 3000 - 3500A range. A variable Hsub(α) - emission has been discovered in the spectrum of BN Ori. It is suggested, that both UV - excess and Hsub(α)-emission are due to hydrogen recombination radiation with self- absorption in the line, however, the contribution of free-free radiation to IR excess is small. The observed IR excess is conditioned mainly by the thermal re-radiation of circumstellar dust envelope with temperature of about 1500 deg