Observational Constraints on the Origin of Metals in Cool DA-type White Dwarfs

R. Chary, B. Zuckerman, E. E. Becklin

We present ISOCAM 7 micron and 15 micron observations of 12 nearby white dwarfs, 6 of which have been found to have metals such as Ca, Mg and Fe in their photospheres. Our purpose…