Iron in Hot DA White Dwarfs

Abstract

We present a study of the iron abundance pattern in hot hydrogen-rich (DA) white dwarfs. The study is based on new and archival far ultraviolet spectroscopy of a sample of white dwarfs in the temperature range 30,000 K < T_eff < 64,000 K. The spectra obtained with the Far Ultraviolet Spectroscopic Explorer along with spectra obtained with the Hubble Space Telescope Imaging Spectrograph and the International Ultraviolet Explorer sample FeIII to FeVI absorption lines enabling a detailed iron abundance analysis over a wider range of effective temperatures than previously afforded. The measurements reveal abundance variations in excess of two orders of magnitude between the highest and the lowest temperatures probed, but also show considerable variations (over one order of magnitude) between objects with similar temperatures and surface gravities. Such variations in cooler objects may be imputed to accretion from unseen companions or so-called circumstellar debris although the effect of residual mass-loss and selective radiation pressure in the hottest objects in the sample remain dominant.

Accepted for publication in ApJ

References in corpus (6)

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• Far-UV sensitivity of the Cosmic Origins Spectrograph
• The spectral evolution of white dwarfs: where do we stand?
• Orbital Parameters and Chemical Composition of Four White Dwarfs in Post-Common Envelope Binaries
• A Comparative Study of Optical and Ultraviolet Effective Temperatures for DA White Dwarfs from the IUE Archive
• The origin of circumstellar features in the spectra of hot DA white dwarfs
• A comprehensive near and far ultraviolet spectroscopic study of the hot DA white dwarf G191-B2B
• Multi-wavelength observations of the EUV variable metal-rich white dwarf GD 394
• A photospheric metal line profile analysis of hot DA white dwarfs with circumstellar material