The Bordeaux meridian observations of asteroids . First determination of the mass of ( 11 ) Parthenope ?

The asteroid observations made with the automatic meridian circle at Bordeaux observatory from 1985 to 1994, and which have recently become available, are presented. The residuals of these observations obtained using the orbital elements published in the “Ephemerides of Minor Planets for 1996” are analysed. An anomaly for the asteroid (17) Thetis was found, indicating a current close encounter between this asteroid and (4) Vesta. Such an encounter will allow very interesting determinations of the mass of Vesta to be made in the future. Lastly, our determination of the mass of (11) Parthenope is discussed, which was based on its perturbations on the orbit of Thetis. The result obtained, (2.58 ± 0.10) 10−12 M , appears significant.