Properties of galactic B[e] supergiants: III. MWC 300

We present the results of optical and near-IR spectroscopic and mid-IR imaging observations of the emission-line star MWC 300. Its properties and evolutionary state are still under debate (a B[e] supergiant or a Herbig Be star). For the first time we detected radial velocity variations of the photospheric lines and found a correlation between them and those of the He I lambda 5876 Ae line. Most of the pure emission lines had stable positions for nearly 20 years. New estimates of the object's luminosity (log L/L direct product = 5.1 plus or minus 0.1), distance (D = 1.8 plus or minus 0.2 kpc), and systemic velocity (+26 plus or minus 2 km s super(-1)) were derived. We found that both the circumstellar extinction in the disk-like dusty envelope and the interstellar extinction play a significant role in the attenuation of the stellar brightness. Our 2D modeling of the observed spectral energy distribution in the wavelength range from 0.3 mu m to 1.3 mm suggests that the star is viewed through a gaseous-and-dusty flared disk with an opening angle of 30 degree , an inclination angle of 10 degree , an equatorial optical depth tau sub(V) = 3.0, and a total mass of 0.08 M direct product . We argue that MWC 300 is most likely a binary system, because of the similarities of its observed parameters with those of recognized B[e] binaries.