Radial velocity observations and physical activities of the contact binary system SW lacertae

Abstract

Abstract We present our 1984 radial velocity observations of the W UNa system SW Lac. These give a new spectroscopic mass ratio qsp = 1.255 ±0.011. A joint solution of the velocity and light curves give the following revised absolute parameters: M 1 = 0.78 M⊚, M 2 = 0.96M⊚, R 1 = 0.91R⊚ , and R 2 = 1.00 R⊚ . Based on our new results, together with a detailed review of the period changes, probable mass transfer, mass loss, spot activity and other physical properties of SW Lac are discussed.