Astron. Astrophys. 364, L66-L69 (2000)

Letter to the Editor

The white dwarf companion to PSR B0820+02 ^*

D. Koester ¹ and D. Reimers <sup>2

1</sup> Institut für Theoretische Physik und Astrophysik, Universität Kiel, 24098 Kiel, Germany (koester@astrophysik.uni-kiel.de)
² Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany (dreimers@hs.uni-hamburg.de)

Received 27 July 2000 / Accepted 7 September 2000

Abstract

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 . 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.

Key words: stars: pulsars: individual: PSR B0820+02 stars: white dwarfs

* Based on observations obtained at the Paranal Observatory of the European Southern Observatory for program 64.H-0203

Send offprint requests to: D. Koester

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Contents

• 1. Introduction
• 2. Observing the white dwarf companions
• 3. Discussion and conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: December 15, 2000
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