THE ABSOLUTE PARAMETERS OF THE ALGOL-TYPE BINARY STAR AF GEMINORUM

We present a spectroscopic orbit for both components of the Algol-type eclipsing binary star AF Gem based on radial velocity measurements fr om 17 CCD spectra using the cross-correlation technique. We find: (a(1 )+a(2)) sin i = 8.03 +/- 0.11R., m(1) sin(3) i = 3.36 +/- 0.11M., m(2) sin(3) i 1.15 +/- 0.04M., m(1)/m(2) = 2.92 +/- 0.07. This is the firs t direct measurement of the mass ratio for this system. The radial vel ocity measurements for the cool component vary peculiarly and this is tentatively explained as a combination of chromospheric activity and n on-synchronous rotation. We also present new solutions to the UBV ligh t curves of Chambliss (1982) using our new spectroscopic orbit to fix the mass ratio and to derive absolute parameters for both components. These absolute parameters have been used to apply corrections for non- Keplerian effects to the spectroscopic orbit. The absolute parameters of the system are found to be: M(1) = 3.37 +/- 0.11M., M(2) = 1.155 +/ - 0.04M., R(1) = 2.61 +/- 0.06R., R(2) = 2.32 +/- 0.04R., log(L(1)/L.) = 1.78 +/- 0.09, log(L(2)/L.) = 0.75 +/- 0.03. A comparison of AF Gem with the non-conservative case B evolution models of De Greve (1993) suggests that the system evolved from an initial mass ratio nearer to 0.6 than 0.9, and that perhaps more angular momentum has been lost tha n has been assumed in the models.