Contribution to the search of binaries among Am stars*
II. HD 81976 and HD 98880, double-lined spectroscopic binaries
UMR 5572 d'Astrophysique, Observatoire Midi-Pyrénées -Centre National de la Recherche Scientifique, 14 avenue Édouard Belin, 31400 Toulouse, France
Corresponding author: J.-M. Carquillat, email@example.com
Accepted: 15 January 2001
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: days, HJD, , , km s-1, km s-1, km s-1, Gm, Gm, , , and 2) for HD 98880: days, HJD (ascending node), , km s-1, km s-1, km s-1, Gm, Gm, , . The first of these two systems, HD 81976, is formed by two quasi-identical stars, and the Hipparcos data (MV, ) 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 and we propose a simple model based upon Strömgren photometric indices and the HR theoretical diagram of Schaller et al (1992) in addition to orbital parameters and Hipparcos data: K, , , , . The components do not rotate synchronously contrary to HD 81976. Both binaries appear to be detached systems without possibility of eclipses.
Key words: stars: individual: HD 81976, HD 98880 / binaries: spectroscopic / stars: fundamental parameters
© ESO, 2001