Properties of Galactic Be Supergiants. VI.

We confirm earlier findings that it is a binary system. The orbital parameters were derived using cross-correlation of the spectra in a range of 4460-4632{AA}, which contains over 30 absorption lines.

The orbit was found to be circular with a period of 137.4{+/-}0.1days, radial velocity semiamplitude K1=5.0{+/-}0.8km/s, systemic radial velocity {gamma}=26.4{+/-}2.0km/s, and mass function f(m)=(1.81_-0.76_^+0.97^)x10^-3^M{sun}. The object may have evolved from a pair with initial masses of ~6.0M{odot} and ~3.6M{sun} with an initial orbital period of ~5days. Based on the fundamental parameters of the A-supergiant (luminosity log L/L{sun}=4.1{+/-}0.1 and effective temperature Teff=8500{+/-}500K) and evolutionary tracks of mass-transferring binaries, we found current masses of the gainer M2=8.8{+/-}0.5M{sun} and donor M1=0.75{+/-}0.25M{sun}.