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

Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany

Received: 10 April 2001
Accepted: 30 May 2001

Abstract

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 significant radial velocity variations over a time interval of 14 years. The spectral classification 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 kpc. This is consistent with the kinematic distance of kpc. The masses derived from the locations of the binary components in the H-R diagram are and for the B and K star, respectively, i.e. the mass ratio is close to 1. Both stars are coeval with an age of 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 i λ6708 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.