Michael Geffert

The Mass Distribution of the Milky Way Deduced from Globular Cluster Dynamics

We present here a new analytical Galactic potential. We used the constraint of galactic globular cluster dynamics compared to their spatial distribution. This was done with the help of the globular clusters’ proper motions. The result for the clusters dynamics show a better agreement between orbital parameters and statistical distribution of the studied globular clusters than in previous published potentials. The globular cluster dynamics constrain the mass distribution on a large scale, until 40 kpc from the centre. In this model, the total mass for the Milky Way is 7.9 1011 M⊙.

DIVISION I / COMMISSION 8 / WORKING GROUP ASTROGRAPHIC CATALOGUE AND CARTE DU CIEL PLATES

PRESIDENT Beatrice Bucciarelli PAST PRESIDENT Alain Fresnau MEMBERS Carlos Abad, Robert W. Argyle, James Biggs, Noah Brosch, George V. Coyne, Emmanuael Davoust, Jean-Pierre M. De Cuyper, Edwin L. van Dessel, Christine Ducourant, Ivan H. Bustos Fierro, Michael Geffert, Elena V. Glushkova, Michael J. Irwin, Dayton L. Jones, Kari A. Lumme, J. L. Muiños, Michael Odenkirchen, Rosa B. Orellana, Thierry Pauwels, Theodore J. Rafferty, M. Sanchez, Jörg Sanner, Milcho K. Tsvetkov, Alan E. Vaughan

Photometric Monitoring of the Lensed QSO 0957+561

We present our first results of a photometric monitoring project of the twin quasar 0957+561. This project aims mainly at the improvement of the determination of the time delay ΔT(A,B) for this gravitational lens, since the “time delay controversy on QSO 0957+561 (is) not yet decided” (Pelt et al. 1994). In addition, the quite large field of the CCD used allows also a long-term astrometric and photometric study of stars and galaxies in the field within a radius of about 10 arcminutes around the lens.