The β Cephei variable in the eclipsing binary HD 92024. I. Determination of the orbit

HD 92024 is a member of the open cluster NGC 3293; it is the only eclipsing binary system with a beta Cephei component known in the southern hemisphere. This paper presents the first spectroscopic analysis of the single-lined binary and provides an orbital analysis based on recent high-resolution spectroscopy and photometry. A procedure to derive orbital elements with minimal influence of the pulsational line-profile variations on the radial velocities is applied, and we find the stellar masses to be 15.0 super(+) sub(-) super(3) sub(4) super(.) sub(.) super(0) sub(0) M sub( theta ) and 3.0 plus or minus 0.5 M sub( theta ) respectively, and radii of 8.4 plus or minus 0.8 R sub(,) 2.1 plus or minus 0.4 R sub(.) The temperatures are 25 500 plus or minus 500 K and 12 500 plus or minus 1000 K. The surface gravity values of log g = 3.77 plus or minus 0.08 and 4.27 plus or minus 0.18 indicate that the binary consists of an evolved early B-type primary and a late-B main sequence companion. The resulting distance 2.8 plus or minus 0.3 kpc and systemic velocity -16 km s super(-1) confirm cluster membership. Theoretical stellar models indicate an age of 10-13 Myr, somewhat higher than the literature value for the brightest members of NGC 3293.