Detection of the secondary of Algol

Abstract

We have detected the Na D lines of the secondary of Algol (ß Persei). The velocity curve obtained from 10 measurements of the velocity of the secondary has a semiamplitude of 201 ± 6 km s-1. A mass ratio, twa/twb, of 4.6 + 0.1 and masses wa, wb, and of 3.7 ± 0.3, 0.81 ± 0.05, and 1.7 ± 0.2 w 0 , respectively, are derived. The results are in agreement with indirect determinations of the masses. The secondary fills its Roche lobe.