Hot DA white dwarf model atmosphere calculations : including improved Ni PI cross sections

Preval, S. P. and Barstow, M. A. and Badnell, N. R. and Hubeny, I. and Holberg, J. B. (2017) Hot DA white dwarf model atmosphere calculations : including improved Ni PI cross sections. Monthly Notices of the Royal Astronomical Society, 465 (1). pp. 269-280. ISSN 0035-8711 (https://doi.org/10.1093/mnras/stw2800)

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Abstract

To calculate realistic models of objects with Ni in their atmospheres, accurate atomic data for the relevant ionization stages needs to be included in model atmosphere calculations. In the context of white dwarf stars, we investigate the effect of changing the Ni {\sc iv}-{\sc vi} bound-bound and bound-free atomic data has on model atmosphere calculations. Models including PICS calculated with {\sc autostructure} show significant flux attenuation of up to $\sim 80$\% shortward of 180\AA\, in the EUV region compared to a model using hydrogenic PICS. Comparatively, models including a larger set of Ni transitions left the EUV, UV, and optical continua unaffected. We use models calculated with permutations of this atomic data to test for potential changes to measured metal abundances of the hot DA white dwarf G191-B2B. Models including {\sc autostructure} PICS were found to change the abundances of N and O by as much as $\sim 22$\% compared to models using hydrogenic PICS, but heavier species were relatively unaffected. Models including {\sc autostructure} PICS caused the abundances of N/O {\sc iv} and {\sc v} to diverge. This is because the increased opacity in the {\sc autostructure} PICS model causes these charge states to form higher in the atmosphere, moreso for N/O {\sc v}. Models using an extended line list caused significant changes to the Ni {\sc iv}-{\sc v} abundances. While both PICS and an extended line list cause changes in both synthetic spectra and measured abundances, the biggest changes are caused by using {\sc autostructure} PICS for Ni.

ORCID iDs

Preval, S. P. ORCID logoORCID: https://orcid.org/0000-0001-8552-0766, Barstow, M. A., Badnell, N. R. ORCID logoORCID: https://orcid.org/0000-0001-7418-7996, Hubeny, I. and Holberg, J. B.;
  • Item type:Article
    ID code:58374
    Dates:
    Date
    Event
    11 February 2017
    Published
    2 November 2016
    Published Online
    28 October 2016
    Accepted
    Notes:This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record Preval, S. P., Barstow, M. A., Badnell, N. R., Hubeny, I., & Holberg, J. B. (2016). Hot DA white dwarf model atmosphere calculations: including improved Ni PI cross sections. Monthly Notices of the Royal Astronomical Society is available online at: https://mnras.oxfordjournals.org/ .
    Subjects:Science > Astronomy
    Department:Faculty of Science > Physics
    Depositing user: Pure Administrator
    Date deposited:31 Oct 2016 15:48
    Last modified:11 Nov 2024 11:33
    Related URLs:
    URI:https://strathprints.strath.ac.uk/id/eprint/58374
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