White dwarfs in open clusters. VIII. NGC 2516: a test for the mass-radius and initial-final mass relations.
We present new observations of white dwarfs in the open cluster NGC 2516, which are of much higher quality than those used in an earlier study of 1982. These data confirm the cluster membership of a fourth object (NGC 2516-3), which had remained open in 1982. Atmospheric parameters are derived from a comparison with a grid of model atmospheres. From the white dwarf cooling times, the cluster age, and evolutionary lifetimes of main sequence and red giant stars we derive the masses of the white dwarf progenitors. These masses are in the range 5.4 to 7.0Msun_ and confirm the result of our extensive study of white dwarfs in open clusters: the limiting (upper) mass for a main sequence star that ends as a white dwarf is close to 8Msun_. When the cluster membership is confirmed, the cluster distance provides a distance estimate with an error of only 2.3%, much more accurate than typical parallaxes. Using the radii for the white dwarfs and the surface gravity, masses can be obtained without using the mass-radius relation. This is used as a test of this relation at the high-mass end, where very few field white dwarfs are found.
Astronomy and Astrophysics
- Pub Date:
- September 1996
- OPEN CLUSTERS AND ASSOCIATIONS: NGC 2516;
- STARS: WHITE DWARFS