STUDIES OF EARLY-TYPE VARIABLE-STARS .12. SPECTROSCOPIC ORBIT AND ABSOLUTE PARAMETERS OF AT PEGASI

A new spectroscopic orbit is presented for the Algol system AT Peg (HD 210892, P=1.146 days, alpha(2000.0)=22h13.4m, delta = +8-degrees-25.5', A4V+G). We find: m(p) sin3 i = 2.04 +/- 0.06 M., m, sin3 i = 0.96 +/- 0.025 M., (a(p) + a(s)) sin i = 4.62 +/- 0.06 x 10(6)km, m(p)/m(s) = 2.115 +/- 0.04. This is the first direct measure of the mass ratio for this system. The new mass ratio is used to solve the single colour light curve of Cristaldi & Walter (1963). We find the following absolute parameters: m(p) = 2.22 +/- 0.065 M., m(s) = 1.05 +/- 0.025 M., [R(p)] = 1.86 +/- 0.025 R., [R(s)] = 2.15 +/- 0.03 R, [T(p)] = 8400 +/- 100K, [T(s)] = 4900 +/- 200K. The spectral type of the primary was established from a spectrum of the primary reconstructed from the spectroscopic data set using tomography. AT Peg is slightly reddened (E(B-V)=0.03 +/- 0.03) at a distance of 360 +/- 20 parsecs.