Mass and density of asteroids (4) Vesta and (11) Parthenope

As mentioned in a previous paper (Viateau & Rapaport 1997), the orbit of as teroid (17) Thetis is strongly perturbed by two large minor planets, (4) Ve sta and (11) Parthenope. These strong gravitational perturbations enabled u s to determine both the mass of Vesta and the! mass of Parthenope. We also independently derived the mass of Vesta from observations of (197) Arete. T he weighted mean of the two results gives the value (1.306 +/- 0.016) 10(-1 0) M circle dot (solar mass) for the mass of Vesta. and its derived mean de nsity is (3.3 +/- 0.5) g/cm(3) For (II) Parthenope, the values (2.56 +/- 0. 07) 10(-12) M circle dot and (2.3 +/- 0.2) g/cm(3) were obtained, respectiv ely for its mass and its mean density.