A spectroscopic study of the secondary star of BM Ori: Preliminary results

Two CCD spectra of the star BM Ori were obtained with the echelle spectrogr aph of the 6-m telescope. In one of the spectra, a large proportion of line s are distorted by emission. The emission component is blueshifted by 50 km s(-1), suggesting hot-gas outflow from the atmosphere. The equivalent-widt h ratio of measured lines in the spectra outside and during eclipse is cons istent with the assumption that similar to2/3 of the primary star's area is obscured during eclipse, as follows from light curves. Measured line equiv alent widths were used to estimate atmospheric parameters of the secondary star, T-eff = 7300 K, log g = 5.2, and microturbulence xi (t) = 6 km s(-1). and to determine its chemical composition. The C, Na, Al, Si, S, Ca, Fe, N i, and Zn abundances are solar, within the error limits. Li, Sc, Ti, V, Cr, Mn, Co, and Y are overabundant, while Mg, Cu, and Ba are under-abundant. I n general, the secondary is similar in chemical composition to the star V10 16 Ori. Based on the secondary's mass determined by solving the radial-velo city curve and on log g estimated spectroscopically from iron ionization eq uilibrium, we calculated its photospheric radius, R-2 = 0.5R(circle dot). H owever, the spectroscopic log g = 5.2 disagrees with log g = 3.5 calculated from the luminosity and effective temperature and with log g = 3.0 calcula ted from light and radial-velocity curves. If the secondary's photospheric radius is indeed small; this argues for the hypothesis that the eclipsing b ody is a dust envelope. The radial velocities measured from the two spectra are systematically higher than those calculated from the radial-velocity c urve by +34 and +24 km s(-1) It is likely that the secondary's atmosphere o ccasionally shrinks. (C) 2001 MAIK "Nauka/Interperiodica".