Related papers: The distribution of metals in hot DA white dwarfs
The relatively high abundance of carbon in the hot DO white dwarf RE0503-289 indicates that it is a descendant of a PG1159 star. This is corroborated by the recent detection of the extremely high abundances of trans-Fe elements which stem…
PG0948+534 is currently one of the hottest DA white dwarf stars, and is also one of the most mysterious. Attempts to model the sharp, deep absorption features of this star have been unsuccessful. In these proceedings we describe our…
We present the first evidence for the direct detection of nickel in the photosphere of the hot DO white dwarf REJ0503$-$289. While this element has been seen previously in the atmospheres of hot H-rich white dwarfs, this is one of the first…
We present a series of systematic abundance measurements for a group of hot DA white dwarfs in the temperature range 20,000-75,000K, based on far-UV spectroscopy with STIS on HST, IUE and FUSE. Using our latest heavy element blanketed…
A study of high ion metal absorption features present in the spectra of hot DA white dwarfs is presented. An analysis of three DAs is performed, where previous studies came to conflicting conclusions as to the stars' nitrogen…
Some hot DA stars exhibit circumstellar absorption in the metal resonance lines in their spectra. In many cases, these circumstellar features are unresolved from those originating in the photosphere. To better understand the effect this…
The accretion of planetary debris into the atmospheres of white dwarfs leads to the presence of metal lines in their spectra. Cool metal-rich white dwarfs, which left the main-sequence many Gyr ago, allow the study of the remnants of the…
We present a phenomenological study of highly ionised, non-photospheric absorption features in high spectral resolution vacuum ultraviolet spectra of 23 hot DA white dwarfs. Prior to this study, four of the survey objects (Feige 24, REJ…
About a dozen hot white dwarfs with effective temperatures Teff = 65,000-120,000 K exhibit unusual absorption features in their optical spectra. These objects were tentatively identified as Rydberg lines of ultra-high excited metals in…
Using newly obtained high-resolution data ($R\sim{1\times{10}^{5}}$) from the \textit{Hubble Space Telescope}, and archival UV data from the \textit{Far Ultraviolet Spectroscopic Explorer} we have conducted a detailed UV survey of the three…
There is a striking paucity of hydrogen-rich (DA) white dwarfs (WDs) relative to their hydrogen-deficient (non-DA) counterparts at the very hot end of the WD cooling sequence. The three hottest known DAs (surface gravity log g $\geq$ 7.0)…
In the line-of-sight toward the DO-type white dwarf RX J0503.9-2854, the density of the interstellar medium (ISM) is very low, and thus the contamination of the stellar spectrum almost negligible. This allows us to identify many metal lines…
Intermediate resolution spectroscopy of the white dwarf SDSSJ104341.53+085558.2 contains double-peaked emission lines of CaII8498,8542,8662 and identifies this object to be the second single white dwarf to be surrounded by a gaseous disc of…
Some hot DA white dwarfs have circumstellar high ion absorption features in their spectra, in addition to those originating in the photosphere. In many cases, the line profiles of these absorbing components are unresolved. Given the…
Two peculiar stars showing an apparent extremely broadened and strong NaI D absorption have been discovered in surveys for cool white dwarfs by Oppenheimer et al. (2001) and Harris et al. (SDSS, 2003). We discuss the nature of these objects…
The metal abundances in the atmospheres of hot white dwarfs (WDs) entering the cooling sequence are determined by the preceding Asymptotic Giant Branch (AGB) evolutionary phase and, subsequently, by the onset of gravitational settling and…
We report the first discovery of argon in hot evolved stars and white dwarfs. We have identified the ArVII 1063.55A line in some of the hottest known (Teff=95000-110000 K) central stars of planetary nebulae and (pre-) white dwarfs of…
We report early FUSE observations of the very hot DA white dwarfs PG1342+444 and REJ0558-371. Detection of photospheric absorption lines allows us to estimate the abundances of C, O, Si, P, S and Fe, the first measurements reported for DA…
We have identified two moderately hot (~18000-22000K) white dwarfs, SDSSJ1228+1040 and SDSSJ1043+0855, which exhibit double-peaked emission lines in the CaII 8600A triplet. These line profiles are unambiguous signatures of gaseous discs…
This paper is focused on the transition phase between central stars and white dwarfs, i.e. objects in the effective temperature range 100,000 - 200,000 K. We confine our review to hydrogen-deficient stars because the common H-rich objects…