2001A&A...369..908C

We present the results of the observations of two Am stars of eighth magnitude, the double-lined spectroscopic binaries HD 81976 and HD 98880, carried out with the CORAVEL instrument at the Observatoire de Haute-Provence in order to determine their orbital elements. We found 1) for HD 81976: P=5.655750 days, T=2449785.941 HJD, ω=341.4°, e=0.061, K₁=61.68km/s, K₂=63.84km/s, V₀=19.85km/s, a₁sin(i)=4.788Gm, a₂sin(i)=4.956Gm, M₁sin³(i)=0.5875M_☉, M₂sin³(i)=0.5676M_☉, and 2) for HD 98880: P=14.20783 days, T₀=2448682.883 HJD (ascending node), e=0., K₁=42.47km/s, K₂=49.16km/s, V₀=2.40km/s, a₁sin(i)=8.298Gm, a₂sin(i)=9.604Gm, M₁sin³(i)=0.6091M_☉, M₂sin³(i)=0.5262M_☉. The first of these two systems, HD 81976, is formed by two quasi-identical stars, and the Hipparcos data (M_V, B-V) are consistent with late A stars in effective temperature; it is likely that the components rotate synchronised with the orbital motion. A third body may be present in this system since (i) the orbit has a significant eccentricity despite its short period and (ii) the systemic velocity V₀ shows a possible drift. For the second system, HD 98880, we give Δm_B=1.25 and we propose a simple model based upon Stroemgren photometric indices and the HR theoretical diagram of Schaller et al (1992A&AS...96..269S) in addition to orbital parameters and Hipparcos data: T_eff=7000K, log₁₀g=4.0, M₁=1.9M_☉, M₂=1.6M_☉, log₁₀(age)=9.12. The components do not rotate synchronously contrary to HD 81976. Both binaries appear to be detached systems without possibility of eclipses.