Abstract One of the central mysteries of white dwarf studies has been the nature and abundance of trace elements in the atmospheres of these stars. It had been thought that the dominant trace element in otherwise pure hydrogen DA white dwarf atmospheres was helium. However, some spectroscopic and theoretical evidence suggested that, at least in some stars, heavier elements may be important. Prior to the launch of ROSAT the questions regarding the atmospheric composition of DA white dwarfs in general remained unresolved. The ROSAT mission has provided EUV and X-ray data for a large sample of DA white dwarfs with which we can study their photospheric composition and structure through the effect of trace opacity sources on the emergent fluxes. Contrary to expectations little (if any) helium is found and the main sources of opacity appear to be trace heavy elements. Support for these conclusions is found in recent EUV and far-UV spectra of several stars. However, photometric data do not allow us to determine the abundance of the individual elements and observations with the EUVE spectrometers will be essential for detailed composition measurements.


    Access

    Check access

    Check availability in my library

    Order at Subito €


    Export, share and cite



    Title :

    Photospheric composition and structure in white dwarfs


    Contributors:

    Published in:

    Publication date :

    1993-01-01


    Size :

    8 pages




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English



    Photospheric Composition and Structure in White Dwarfs

    Barstow, M.A. | Online Contents | 1993


    Photospheric Composition and Structure in White Dwarfs

    Barstow, M. A. / COSPAR | British Library Conference Proceedings | 1993


    White dwarfs

    Barstow, M.A. | Elsevier | 1991


    White Dwarfs Observed by Hipparcos

    Vauclair, G. / Schmidt, H. / Koester, D. et al. | British Library Online Contents | 1997


    Photospheric Abundances

    Grevesse, N. et al. | British Library Online Contents | 1992