Parameters for the Eclipsing B - star Binary HD 42401

I present results from an optical spectroscopic investigation of the binary system HD 42401 (V1388 Ori; B2.5 IV-V + B3 V). A combined analysis of V−band photometry and radial velocities indicates that the system has an orbital period of 2.18706 ± 0.00005 days and an inclination of 75.5 ± 0.2 degrees. This solution yields masses and radii of M1 = 7.42 ± 0.08 M⊙ and R1 = 5.60 ± 0.04 R⊙ for the primary and M2 = 5.16 ± 0.03 M⊙ and R2 = 3.76 ± 0.03 R⊙ for the secondary. Based on the position of the two stars plotted on a theoretical H-R diagram, I find that the age of the system is & 25 Myr and that both stars appear overluminous for their masses compared to single star evolutionary tracks. A fit of the spectral energy distribution based on photometry from the literature yields a distance to HD 42401 of 832 ± 89 parsecs. Subject headings: binaries: spectroscopic – stars: early-type – stars: fundamental parameters – stars: individual (HD 42401)