Hot DA white dwarf model atmosphere calculations

Including improved Ni PI cross-sections

S. P. Preval, M. A. Barstow, N. R. Badnell, Ivan - Hubeny, J. B. Holberg

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

To calculate realistic models of objects with Ni in their atmospheres, accurate atomic data for the relevant ionization stages need to be included in model atmosphere calculations. In the context of white dwarf stars, we investigate the effect of changing the Ni IV-VI bound-bound and bound-free atomic data on model atmosphere calculations. Models including photoionization cross-section (PICS) calculated with AUTOSTRUCTURE show significant flux attenuation of up to ~80 per cent shortward of 180Å in the extreme ultraviolet (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 these atomic data to test for potential changes to measured metal abundances of the hot DA white dwarf G191-B2B. Models including AUTOSTRUCTURE PICS were found to change the abundances of N and O by as much as ~22 per cent compared to models using hydrogenic PICS, but heavier species were relatively unaffected. Models including AUTOSTRUCTURE PICS caused the abundances of N/O IV and V to diverge. This is because the increased opacity in the AUTOSTRUCTURE PICS model causes these charge states to form higher in the atmosphere, more so for N/O V.Models using an extended line list caused significant changes to the Ni IV-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 AUTOSTRUCTURE PICS for Ni.

Original languageEnglish (US)
Pages (from-to)269-280
Number of pages12
JournalMonthly Notices of the Royal Astronomical Society
Volume465
Issue number1
DOIs
StatePublished - 2017

Fingerprint

cross section
atmospheres
photoionization
atmosphere
cross sections
lists
calculation
white dwarf stars
causes
permutations
opacity
ionization
attenuation
continuums
metal
metals

Keywords

  • Atomic data
  • Opacity
  • White dwarfs

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Hot DA white dwarf model atmosphere calculations : Including improved Ni PI cross-sections. / Preval, S. P.; Barstow, M. A.; Badnell, N. R.; Hubeny, Ivan -; Holberg, J. B.

In: Monthly Notices of the Royal Astronomical Society, Vol. 465, No. 1, 2017, p. 269-280.

Research output: Contribution to journalArticle

Preval, S. P. ; Barstow, M. A. ; Badnell, N. R. ; Hubeny, Ivan - ; Holberg, J. B. / Hot DA white dwarf model atmosphere calculations : Including improved Ni PI cross-sections. In: Monthly Notices of the Royal Astronomical Society. 2017 ; Vol. 465, No. 1. pp. 269-280.
@article{2207c4c0b81b412ca938a5335a950010,
title = "Hot DA white dwarf model atmosphere calculations: Including improved Ni PI cross-sections",
abstract = "To calculate realistic models of objects with Ni in their atmospheres, accurate atomic data for the relevant ionization stages need to be included in model atmosphere calculations. In the context of white dwarf stars, we investigate the effect of changing the Ni IV-VI bound-bound and bound-free atomic data on model atmosphere calculations. Models including photoionization cross-section (PICS) calculated with AUTOSTRUCTURE show significant flux attenuation of up to ~80 per cent shortward of 180{\AA} in the extreme ultraviolet (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 these atomic data to test for potential changes to measured metal abundances of the hot DA white dwarf G191-B2B. Models including AUTOSTRUCTURE PICS were found to change the abundances of N and O by as much as ~22 per cent compared to models using hydrogenic PICS, but heavier species were relatively unaffected. Models including AUTOSTRUCTURE PICS caused the abundances of N/O IV and V to diverge. This is because the increased opacity in the AUTOSTRUCTURE PICS model causes these charge states to form higher in the atmosphere, more so for N/O V.Models using an extended line list caused significant changes to the Ni IV-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 AUTOSTRUCTURE PICS for Ni.",
keywords = "Atomic data, Opacity, White dwarfs",
author = "Preval, {S. P.} and Barstow, {M. A.} and Badnell, {N. R.} and Hubeny, {Ivan -} and Holberg, {J. B.}",
year = "2017",
doi = "10.1093/mnras/stw2800",
language = "English (US)",
volume = "465",
pages = "269--280",
journal = "Monthly Notices of the Royal Astronomical Society",
issn = "0035-8711",
publisher = "Oxford University Press",
number = "1",

}

TY - JOUR

T1 - Hot DA white dwarf model atmosphere calculations

T2 - Including improved Ni PI cross-sections

AU - Preval, S. P.

AU - Barstow, M. A.

AU - Badnell, N. R.

AU - Hubeny, Ivan -

AU - Holberg, J. B.

PY - 2017

Y1 - 2017

N2 - To calculate realistic models of objects with Ni in their atmospheres, accurate atomic data for the relevant ionization stages need to be included in model atmosphere calculations. In the context of white dwarf stars, we investigate the effect of changing the Ni IV-VI bound-bound and bound-free atomic data on model atmosphere calculations. Models including photoionization cross-section (PICS) calculated with AUTOSTRUCTURE show significant flux attenuation of up to ~80 per cent shortward of 180Å in the extreme ultraviolet (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 these atomic data to test for potential changes to measured metal abundances of the hot DA white dwarf G191-B2B. Models including AUTOSTRUCTURE PICS were found to change the abundances of N and O by as much as ~22 per cent compared to models using hydrogenic PICS, but heavier species were relatively unaffected. Models including AUTOSTRUCTURE PICS caused the abundances of N/O IV and V to diverge. This is because the increased opacity in the AUTOSTRUCTURE PICS model causes these charge states to form higher in the atmosphere, more so for N/O V.Models using an extended line list caused significant changes to the Ni IV-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 AUTOSTRUCTURE PICS for Ni.

AB - To calculate realistic models of objects with Ni in their atmospheres, accurate atomic data for the relevant ionization stages need to be included in model atmosphere calculations. In the context of white dwarf stars, we investigate the effect of changing the Ni IV-VI bound-bound and bound-free atomic data on model atmosphere calculations. Models including photoionization cross-section (PICS) calculated with AUTOSTRUCTURE show significant flux attenuation of up to ~80 per cent shortward of 180Å in the extreme ultraviolet (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 these atomic data to test for potential changes to measured metal abundances of the hot DA white dwarf G191-B2B. Models including AUTOSTRUCTURE PICS were found to change the abundances of N and O by as much as ~22 per cent compared to models using hydrogenic PICS, but heavier species were relatively unaffected. Models including AUTOSTRUCTURE PICS caused the abundances of N/O IV and V to diverge. This is because the increased opacity in the AUTOSTRUCTURE PICS model causes these charge states to form higher in the atmosphere, more so for N/O V.Models using an extended line list caused significant changes to the Ni IV-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 AUTOSTRUCTURE PICS for Ni.

KW - Atomic data

KW - Opacity

KW - White dwarfs

UR - http://www.scopus.com/inward/record.url?scp=85014749199&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85014749199&partnerID=8YFLogxK

U2 - 10.1093/mnras/stw2800

DO - 10.1093/mnras/stw2800

M3 - Article

VL - 465

SP - 269

EP - 280

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 1

ER -