STUDIES OF EARLY-TYPE VARIABLE-STARS .14. SPECTROSCOPIC ORBIT AND ABSOLUTE PARAMETERS OF HU TAURI

We present a new spectroscopic orbit for the Algol-type eclipsing bina ry system HU Tau (HD 29365, P=2.0563 days alpha(2000.0) = 04h 38m 15.8 0s, delta = +20 degrees 41'05.3 '', V=5.87 - 6.8, B8V + G2). We find: m(1) sin(3) i = 4.17 +/- 0.09M., m(2) sin(3) i = 1.07 +/- 0.025M., (a( p) + a(s)) sin i = 11.8 +/- 01R., m(1)/m(2) = 3.90 +/- 0.07. The spect roscopic orbit includes corrections for non-Keplerian effects derived from the solutions of the BV light curves of Ito (1988). We have been able to derive much improved absolute parameters for this system as fo llows: M(1) = 4.43 +/- 0.09M., M(2) = 1.14 +/- 0.03M., R(1) = 2.57 +/- 0.03R., R(2) = 4.21 +/- 0.03R., log(L(1)/L.) = 2.09 +/- 0.15,log(L(2) /L.) = 0.92 +/- 0.05. Comparison of HU Tau with non-conservative case B evolution models of De Greve (1993) suggests that the system evolved from an initial mass ratio less than or similar to 0.5. However, the orbital period of HU Tau is more than 3 days shorter than any of the m odel systems, and the observed secondary luminosity of order 10 times less than a model star of the same mass during the slow mass transfer phase.