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Pure-helium 3D model atmospheres of white dwarfs
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
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2018 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 481, no 2, p. 1522-1537Article in journal (Refereed) Published
Abstract [en]

We present the first grid of 3D simulations for the pure-helium atmospheres of DB white dwarfs. The simulations were computed with the co(5) BOLD radiation-hydrodynamics code and cover effective temperatures and surface gravities between 12 000 K less than or similar to T-eff less than or similar to 34 000 K and 7.5 <= log g (cgs units) <= 9.0, respectively. In this introductory work, synthetic spectra calculated from the 3D simulations are compared to appropriate 1 D model spectra under a differential approach. This results in the derivation of 3D corrections for the spectroscopically derived atmospheric parameters of DB stars with respect to the 1D ML2/alpha = 1.25 mixing-length parametrization. No significant T-eff corrections are found for the V777 Her instability strip region, and therefore no 3D revision is expected for the empirical blue and red edges of the strip. However, large log g corrections are found in the range 12 000 K < T-eff < 23 000 K for all log g values covered by the 3D grid. These corrections indicate that 1D model atmospheres overpredict log g, reminiscent of the results found from 3D simulations of pure-hydrogen white dwarfs. The next step will be to compute 3D simulations with mixed helium and hydrogen atmospheres to comprehend the full implications for the stellar parameters of DB and DBA white dwarfs.

Place, publisher, year, edition, pages
EDP Sciences, 2018. Vol. 481, no 2, p. 1522-1537
Keywords [en]
convection, hydrodynamics, techniques: spectroscopic, stars: atmospheres, white dwarfs
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:uu:diva-354340DOI: 10.1093/mnras/sty2383ISI: 000449764000008OAI: oai:DiVA.org:uu-354340DiVA, id: diva2:1228161
Funder
EU, Horizon 2020, 677706 - WD3DGerman Research Foundation (DFG), Sonderforschungsbereich SFB 881Available from: 2018-06-27 Created: 2018-06-27 Last updated: 2019-01-22Bibliographically approved

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Freytag, Bernd

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