Hydrogen and Metal Abundances in the Cool Helium-Rich White Dwarf ROSS640

Details Hydrogen and Metal Abundances in the Cool Helium-Rich White Dwarf ROSS640 Hydrogen and Metal Abundances in the Cool Helium-Rich White Dwarf ROSS640

Jul 1996

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996hst..prop.6450k&link_type=abstract

HST Proposal ID #6450

Computer Science

Hst Proposal Id #6450 Hot Stars

Scientific paper

The metal traces found in a few cool helium-rich white dwarfs(spectral type DZ) cannot be primordial, but must have beenaccreted from the interstellar matter, since their lifetimesin the atmospheres is limited to about a million years(diffusion timescales). We want to obtain high S/N UV spectraof Ross640, which is one of the brightest DZ, and only one oftwo objects at low Teff showing both metals and H.Abundances will be determined with model atmosphere techniquesand compared with the predictions of the two-phase accretionscenario proposed by the Montreal group. This is the mostadvanced explanation today; however, comparisons betweenobservation and theory are currently severely limited by thelack of reliable and accurate abundance determinations inthese faint objects. HST observations of the second objectwith similar characteristics (L745-46A), which have recentlybeen analyzed by us, demonstrate the huge progress that can bemade with FOS now.

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