Contribution à l'étude de la binarité des étoiles de type Am

I. HD 125273, binaire spectroscopique à raies doubles HD 125273, a double-lined spectroscopic binary

Laboratoire d'Astrophysique (UMR 5572), Observatoire Midi-Pyrénées, 14 avenue Edouard Belin, 31400 Toulouse, France

Received: 25 March 1997
Accepted: 17 December 1997

Abstract

We present an observing program undertaken at Observatoire de Haute-Provence, for the search and study of spectroscopic binaries among Am stars. HD 125273 was recognized as an Am star some time ago (Olsen 1980; Abt 1984); observations, carried out with the CORAVEL spectrovelocimeter, show that this star is a double-lined spectroscopic binary; its orbital elements are as follows: days; JD; ; ;  km/s;   km/s;  km/s;  Gm;  Gm; . Strömgren photometry of the star (Olsen 1983) permits us to estimate the following mean physical parameters for the components of the binary:  K; log ; M_v = 1.24; , and to specify the evolutionary status of the system. Assuming the above mass for the components, we found and . This system is thus a detached one without possibility of eclipses. It is likely that the two components are Am stars of very close characteristics. The values, determined from the correlation dips given by CORAVEL, are near 11 km/s for both components. We retain for this binary the hypothesis of rotation-revolution synchronism, because it leads to a value of the radius of the stars in agreement both with the above value and the results of a previous study by Kitamura & Kondo (1978) of similar, but eclipsing, systems. The ratio of the correlation dip areas indicates a magnitude difference  mag. As expected in detached systems of main sequence stars, such as Am's, HD 125273 obeys the mass-luminosity law.