HD-125273, A DOUBLE-LINED SPECTROSCOPIC B INARY

We present an observing program undertaken at Observatoire de Haute-Pr ovence, for the search and study of spectroscopic binaries among Am st ars. HD 125273 was recognized as an Am star some time ago (Olsen 1980; Abt 1984); observations, carried out with the CORAVEL spectrovelocime ter, show that this star is a double-lined spectroscopic binary; its o rbital elements are as follows: P = 7.482664 days; T = 2448665.660 JD; omega(1) = 355.3 degrees; e = 0.071; K-1 = 49.82 km/s; K-2 = 51.15 km /s; V-0 = -17.42 km/s; a(1 )sini = 5.113 Gm; a(2) sini = 5.311 Gm; M-1 sin(3)i = 0.412M.; M-2 sin(3)i = 0.396 M.. Stromgren photometry of th e star (Olsen 1983) permits us to estimate the following mean physical parameters for the components of the binary: T-eff = 7500 K; log g = 3.70; M-upsilon = 1.24; M = 2.1 M.; R = 3.2 R., and to specify the evo lutionary status of the system. Assuming the above mass for the compon ents, we found i similar to 35 degrees and a similar to 26 R.. This sy stem is thus a detached one without possibility of eclipses. It is lik ely that the two components are Am stars of very close characteristics . The upsilon sini values, determined from the correlation dips given by CORAVEL, are near 11 km/s for both components. We retain for this b inary the hypothesis of rotation-revolution synchronism, because it le ads to a value of the radius of the stars in agreement both with the a bove value and the results of a previous study by Kitamura & Kondo (19 78) of similar, but eclipsing, systems. The ratio of the correlation d ip areas indicates a magnitude difference am, Delta m(upsilon) similar to 0.2 mag. As expected in detached systems of main sequence stars, s uch as Am's, HD 125273 obeys the mass-luminosity law.