Radial velocities of the semi-detached Algol W UMi

In this study, we aim to determine a unique set of binary parameters for the Algol system W UMi and to examine its evolutionary status. New high-resolution time-series spectroscopic observations were carried out during 14 nights from 2008 April to 2011 March, and a total of 37 spectra were obtained using the Bohyunsan Optical Echelle Spectrograph.

We measured the radial velocities (RVs) for both components, and the effective temperature of the primary star was found to be T_eff,1_=9310+/-90K by a comparison of the observed spectra and the Kurucz models. The physical parameters of W UMi were derived by an analysis of our RV data together with the multi-band light curves of Devinney et al. The individual masses, radii, and luminosities of both components are M1=3.68+/-0.10M_{sun}_ and M2=1.47+/-0.04M_{sun}_, R1=3.88+/-0.03R_{sun}_ and R2=3.13+/-0.03R_{sun}_, and L1=102+/-1L_{sun}_ and L2=7.3+/-0.1L_{sun}_, respectively.