The B Supergiant Components of the Double‐lined Binary HD 1383

We present new results from a study of high quality, red spectra of themassive binary star system HD 1383 (B0.5 Ib + B0.5 Ib). We determined radialvelocities and revised orbital elements (P = 20.28184 +/- 0.0002 d) and madeDoppler tomographic reconstructions of the component spectra. A comparison ofthese with model spectra from non-LTE, line blanketed atmospheres indicatesthat both stars have almost identical masses (M_2/M_1 = 1.020 +/- 0.014),temperatures (T_eff = 28000 +/- 1000 K), gravities (log g = 3.25 +/- 0.25), andprojected rotational velocities (V sin i < 30 km/s). We investigate a number ofconstraints on the radii and masses of the stars based upon the absence ofeclipses, surface gravity, stellar wind terminal velocity, and probablelocation in the Perseus spiral arm of the Galaxy, and these indicate a range inprobable radius and mass of R/R_sun = 14 - 20 and M/M_sun = 16 - 35,respectively. These values are consistent with model evolutionary masses forsingle stars of this temperature and gravity. Both stars are much smaller thantheir respective Roche radii, so the system is probably in a pre-contact stageof evolution. A fit of the system's spectral energy distribution yields areddening of E(B-V)=0.55 +/- 0.05 and a ratio of total-to-selective extinctionof R=2.97 +/- 0.15. We find no evidence of H-alpha emission from collidingstellar winds, which is probably the consequence of the low gas densities inthe colliding winds zone.Comment: Accepted for publication in ApJ: 20 pages, 5 figure