New spectroscopic observations of the B[e]/K binary system MWC 623

The B(e)/K binary system MWC 623 was reinvestigated using new spectroscopic observations. The absorption lines of the K and the B star do not exhibit any signicant radial velocity variations over a time interval of 14 years. The spectral classication using a recent echelle spectrum yielded spectral types of K2II-Ib and B4III. The luminosity class of the K star gives an estimate of the distance towards MWC 623 of 2:4 +1:4 0:9 kpc. This is consistent with the kinematic distance of 2:0 +0:6 0:3 kpc. The masses derived from the locations of the binary components in the H{R diagram are 7 1:5 M and 7:5 2:5 M for the B and K star, respectively, i.e. the mass ratio is close to 1. Both stars are coeval with an age of 50 +10 20 Myr as shown by the comparison with isochrones. The high luminosity of the K star excludes a pre-main sequence evolutionary phase as explanation for the strong Li i6708 absorption line observed in the late-type component. Rather, the high lithium abundance is a consequence of the young age. Likewise, the B(e) star is a slightly evolved object starting it post-main sequence evolution.