A photometric and spectroscopic study of the Herbig Ae/Be star XY Per

The UBVR photometry of XY Per in 1985-1998 is presented. At this epoch, XY Per exhibited variability with an amplitude of approximate to 1(m) in V! The photometric variability of XY Per can be divided into three components: (1) smooth year-to-year variations in mean brightness; (2) quasi-periodic variations with a characteristic time scale of 20-40 days and an amplitude of 0.(m)3; and (3) Algol-like minima with a duration of 15-20 days and an amplitude of 0.(m)6. The CLEAN algorithm is used to refine the quasi-period of light variations in the interval 1988-1995, P = 22.(d)7252. The observed variability is assumed to be produced by two mechanisms: circumstellar absorption and nonstationary accretion. An ultraviolet excess was observed in the stellar radiation during the local minimum of 1991, which was associated with an eclipse of the star by a circumstellar formation. The probable reason why it emerged is that part of the eclipsing circumstellar formation fell into the accretion zone. A high-resolution spectrum in the wavelength range 3600-6700 Angstrom contains both photospheric lines and circumstellar shell lines. The shell line profiles suggest mass accretion onto the star at a velocity of 90-140 km s(-1) Of the Palmer lines, only Ha is in emission. Its equivalent width is E(W-lambda) = -0.8 Angstrom. The strongest Fe II lines, as well as Mg II 4481.33 Angstrom and He I 5875.65 Angstrom,, have an emission component at the line center. The presence of emission components in lines with different excitation potentials suggests the presence of a hot gas shell around the star, which is heated very nonuniformly. (C) 2000 MAIK "Nauka/interperiodica ".