Astronomy and Astrophysics – Astronomy
Scientific paper
May 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001astl...27..328v&link_type=abstract
Astronomy Letters, vol. 27, p. 328-337 (2001)
Astronomy and Astrophysics
Astronomy
1
Variable And Peculiar Stars, Properties And Classification
Scientific paper
Two CCD spectra of the star BM Ori were obtained with the echelle spectrograph of the 6-m telescope. In one of the spectra, a large proportion of lines are distorted by emission. The emission component is blueshifted by 50 km/s, suggesting hot-gas outflow from the atmosphere. The equivalent-width ratio of measured lines in the spectra outside and during eclipse is consistent with the assumption that ~2/3 of the primary star's area is obscured during eclipse, as follows from light curves. Measured line equivalent 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, and to determine its chemical composition. The C, Na, Al, Si, S, Ca, Fe, Ni, 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 underabundant. In general, the secondary is similar in chemical composition to the star V1016 Ori. Based on the secondary's mass determined by solving the radial-velocity curve and on log g estimated spectroscopically from iron ionization equilibrium, we calculated its photospheric radius, R_2 = 0.5 R_solar. However, 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 calculated from light and radial-velocity curves. If the secondary's photospheric radius is indeed small, this argues for the hypothesis that the eclipsing body is a dust envelope. The radial velocities measured from the two spectra are systematically higher than those calculated from the radial-velocity curve by +34 and +24 km/s. It is likely that the secondary's atmosphere occasionally shrinks.
Klochkova Valentina G.
Vitrichenko Eh. A.
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