August 11-15, 2014


Detection of arsenic in the atmospheres of dying stars

Pierre Chayer (Space Telescope Science Institute)

Jean Dupuis (Canadian Space Agency), Jeff W. Kruk (NASA Goddard Space Flight Center)

We report the detection of faint As V lines observed in the Far Ultraviolet Spectroscopic Explorer (FUSE) spectra of three hot DA white dwarfs: G191-B2B, WD0621-376, and WD2211-495. The stars have effective temperatures ranging from 56,000 K to 66,000 K and are among the most metal-rich white dwarfs known. We measure arsenic abundances relative to hydrogen that are two to four times the solar abundance. The arsenic abundances in the atmosphere of these DA white dwarfs are lower than those observed in helium-rich white dwarfs (DO) with slightly cooler temperatures. These observations suggest that He-rich white dwarfs show higher abundances of s-process elements in their atmospheres than H-rich white dwarfs do. This may be because the former, stripped of their outer envelopes, expose deep enriched layers, and/or because more s-process elements were produced at earlier stages in the stars' evolution. In either case, we must take into consideration how diffusion mechanisms by which such heavy elements are supported near the surface of these high gravity stars may affect the superficial abundances.

Mode of presentation: oral