White dwarf stars with carbon atmospheres

  title={White dwarf stars with carbon atmospheres},
  author={P. Dufour and James William Liebert and Gilles Fontaine and Natalie Behara},
White dwarfs represent the endpoint of stellar evolution for stars with initial masses between approximately 0.07 and 8–10, where is the mass of the Sun (more massive stars end their life as either black holes or neutron stars). The theory of stellar evolution predicts that the majority of white dwarfs have a core made of carbon and oxygen, which itself is surrounded by a helium layer and, for ∼80 per cent of known white dwarfs, by an additional hydrogen layer. All white dwarfs therefore have… 
Two White Dwarfs with Oxygen-Rich Atmospheres
The detection of two white dwarfs with large photospheric oxygen abundances are reported, implying that they are bare oxygen-neon cores and that they may have descended from the most massive progenitors that avoid core collapse.
Stars with Unusual Compositions: Carbon and Oxygen in Cool White Dwarfs
White dwarfs represent the end products of the evolution of all stars on the main sequence that had initial masses below ∼8M⊙. After some important mass-loss episodes in the red giant phases,
Might carbon-atmosphere white dwarfs harbour a new type of pulsating star?
Aims. In the light of the recent and unexpected discovery of a new type of white dwarfs, those with carbon-dominated atmospheres, we examine the asteroseismological potential of such stars. The
Evolutionary and pulsational properties of white dwarf stars
White dwarf stars are the final evolutionary stage of the vast majority of stars, including our Sun. Since the coolest white dwarfs are very old objects, the present population of white dwarfs
Latest generation white dwarf cooling models : theory and applications
White dwarfs are the most common stellar evolutionary end-point. Moreover, they can be considered as reliable cosmic clocks to infer the age of a wide variety of stellar populations, including
We present full evolutionary calculations appropriate for the study of hot hydrogen-deficient DO white dwarfs, PG 1159 stars, and DB white dwarfs. White dwarf sequences are computed for a wide range
Central stars of planetary nebulae: The white dwarf connection
  • K. Werner
  • Physics
    Proceedings of the International Astronomical Union
  • 2011
Abstract 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
On the Spectral Evolution of Helium-atmosphere White Dwarfs Showing Traces of Hydrogen
We present a detailed spectroscopic analysis of 115 helium-line (DB) and 28 cool, He-rich hydrogen-line (DA) white dwarfs based on atmosphere fits to optical spectroscopy and photometry. We find that
Atmospheric parameters and carbon abundance for hot DB white dwarfs
Atmospheric parameters for hot DB (helium atmosphere) white dwarfs near effective temperatures of 25000K are extremely difficult to determine from optical spectroscopy. This is particularly
A New Generation of Cool White Dwarf Atmosphere Models. IV. Revisiting the Spectral Evolution of Cool White Dwarfs
As a result of competing physical mechanisms, the atmospheric composition of white dwarfs changes throughout their evolution, a process known as spectral evolution. Because of the ambiguity of their


SDSS White Dwarfs with Spectra Showing Atomic Oxygen and/or Carbon Lines
We discuss 18 white dwarfs, one of which (G227-5) was previously known, whose SDSS spectra show lines of neutral and/or singly ionized carbon. At least two and perhaps four show lines of neutral or
A determination of the local density of white dwarf stars
The most recent version of the Catalog of Spectroscopically Identified White Dwarfs lists 2249 white dwarf stars. Among these stars are 109 white dwarfs that have either reliable trigonometric
On the frequency of planetary nebula nuclei powered by helium burning and on the frequency of white dwarfs with hydrogen-deficient atmospheres
The evolutionary behavior of a model central star of a planetary nebula is examined as a function of the phase in its nuclear burning cycle when its progenitor leaves the asymptotic giant branch for
The Elemental Abundances in Bare Planetary Nebula Central Stars and the Shell Burning in AGB Stars
We review the observed properties of extremely hot, hydrogen‐deficient post–asymptotic giant branch (AGB) stars of spectral type [WC] and PG1159. Their H deficiency is probably caused by a (very)
An atmospheric analysis of the carbon-rich white dwarf G35 - 26
The first detailed atmospheric analysis of the DQ white dwarf G35 - 26 is presented. The analysis is based on published spectra and on helium-rich, homogeneous, blanketed LTE models containing
Detailed Spectroscopic and Photometric Analysis of DQ White Dwarfs
We present an analysis of spectroscopic and photometric observations of cool DQ white dwarfs based on improved model atmosphere calculations. In particular, we revise the atmospheric parameters of
New DQ white dwarfs in the Sloan Digital Sky Survey DR4: confirmation of two sequences
Context. DQ white dwarfs show atomic or molecular carbon features in their spectra. The atmosphere consists of helium and the carbon is believed to be dredged-up to the surface by the deepening
On the formation of hydrogen-deficient post-AGB stars
We present an evolutionary sequence of a low mass star from the Asymptotic Giant Branch (AGB) through its post-AGB stage, during which its surface chemical composition changes from hydrogen-rich to
On the Evolution of Stars that Form Electron-Degenerate Cores Processed by Carbon Burning. III. The Inward Propagation of a Carbon-Burning Flame and Other Properties of a 9 M☉ Model Star
A 9 M☉ stellar model of Population I composition is evolved from the hydrogen-burning main sequence to the thermally pulsing “super” asymptotic giant branch stage, where it has an electron-degenerate
On the Evolution of Stars that Form Electron-degenerate Cores Processed by Carbon Burning. V. Shell Convection Sustained by Helium Burning, Transient Neon Burning, Dredge-out, Urca Cooling, and Other Properties of an 11 M? Population I Model Star
A stellar model of mass 11 M☉ and Population I composition is evolved from the hydrogen-burning main sequence through the core carbon-burning phase. In contrast with 9, 10, and 10.5 M☉ models studied