HST spectroscopy of chemically peculiar hot subdwarfs: PG 0909+276 and UVO0512–08

Abstract

High-resolution ultraviolet spectroscopy of two chemically peculiar hot subdwarfs, PG 0909+276 and UVO0512-08, has been obtained using the Hubble Space Telescope. Chemical abundances in the stars’ atmospheres were measured from previous optical spectra and from the new ultraviolet observations. Iron-group metals, including cobalt, copper and zinc, are highly enriched relative to typical subdwarf B (sdB) stars. Lead is also enriched, but with an abundance similar to other sdB stars. The surface chemistry of these two stars is quite distinct from both hydrogen-rich normal sdB stars and also from the intermediate helium-rich sdB stars which show heavy-element superabundances. A full explanation for exotic chemistries in hot subdwarfs remains elusive.

Keywords

• stars: abundances - stars
• fundamental parameters - stars
• chemically peculiar - stars
• individual ( pg 0909+276) - stars
• individual (uvo0512-08) - stars
• subdwarfs