A contribution to the solution of the Algol paradox

The near infrared sensitivity of the Utrecht Stellar Photometer is advantageous in getting more information about secondaries of Algols. In this thesis, the evolution of these semidetached binary stars is studied. First, the Utrecht Photometric System (UPS) is tested on the, in principle, straightforward detached binary system YZ Cas, and UPS light curves of the Algol TV Cas are presented and interpreted. This partially eclipsing system (primary eclipse is an occultation) shows the typical Algol characteristics: the secondary fills its Roche Lobe and the period is variable. Next, IUE observations are used to determine some photospheric parameters of TV Cas and YZ Cas. TV Cas has a normal metal abundance and did not show evidence for mass motions at the time of observation. The known metal richness of YZ Cas was quantitatively estimated on the basis of line strengths. Being at this stage evolutionary model calculations are tested on YZ Cas. This system can be regarded as consisting of two single stars. Finally, the first quantitative deduction of the initial parameters of an Algol is presented: TV Cas consisted originally of a 3.0 plus a 2.4 solar masses component. (Auth.)