The white dwarf companion to PSR B0820+02

We report new spectroscopic and photometric observations of the white dwarf companion to the pulsar PSR B0820+02. The white dwarf is a normal DA white dwarf with an effective temperature of 15000 K and a mass of 0.6 M_\odot. The mass and orbital period of this system confirm recent simulations of the evolution of a neutron star - main sequence binary with mass exchange and thus implicitely theoretical predictions of the dependence of the red giant radius on the He-core mass. The cooling age of the white dwarf is larger than the spin-down age of the pulsar, unless a braking index of 2.2 is assumed. Based on observations obtained at the Paranal Observatory of the European Southern Observatory for program 64.H-0203