Simulation of Stark-broadened Hydrogen Balmer-line Shapes for da White Dwarf Synthetic Spectra

P. B. Cho, T. A. Gomez, M. H. Montgomery, B. H. Dunlap, M. Fitz Axen, B. Hobbs, I. Hubeny, D. E. Winget

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

White dwarfs (WDs) are useful across a wide range of astrophysical contexts. The appropriate interpretation of their spectra relies on the accuracy of WD atmosphere models. One essential ingredient of atmosphere models is the theory used for the broadening of spectral lines. To date, the models have relied on Vidal et al., known as the unified theory of line broadening (VCS). There have since been advancements in the theory; however, the calculations used in model atmosphere codes have only received minor updates. Meanwhile, advances in instrumentation and data have uncovered indications of inaccuracies: spectroscopic temperatures are roughly 10% higher and spectroscopic masses are roughly 0.1 M higher than their photometric counterparts. The evidence suggests that VCS-based treatments of line profiles may be at least partly responsible. Gomez et al. developed a simulation-based line-profile code Xenomorph using an improved theoretical treatment that can be used to inform questions around the discrepancy. However, the code required revisions to sufficiently decrease noise for use in model spectra and to make it computationally tractable and physically realistic. In particular, we investigate three additional physical effects that are not captured in the VCS calculations: ion dynamics, higher-order multipole expansion, and an expanded basis set. We also implement a simulation-based approach to occupation probability. The present study limits the scope to the first three hydrogen Balmer transitions (Hα, Hβ, and Hγ). We find that screening effects and occupation probability have the largest effects on the line shapes and will likely have important consequences in stellar synthetic spectra.

Original languageEnglish
Article number70
JournalAstrophysical Journal
Volume927
Issue number1
DOIs
StatePublished - Mar 1 2022
Externally publishedYes

Funding

P.B.C., M.H.M., B.H.D., B.A.H., and D.E.W. acknowledge support from the Wootton Center for Astrophysical Plasma Properties under the United States Department of Energy cooperative agreement number DE-NA0003843, from the United States Department of Energy under grant DE-SC0010623, and from the National Science Foundation under grant No. AST 1707419. P.B.C. acknowledges support from the DOE NNSA LRGF under the United States Department of Energy cooperative agreement DE-NA0003960. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the US Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525. This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the US Department of Energy or the United States Government.

FundersFunder number
DOE NNSA LRGFDE-NA0003960
Wootton Center for Astrophysical Plasma Properties
National Science FoundationAST 1707419
National Science Foundation
U.S. Department of EnergyDE-SC0010623, DE-NA0003843
U.S. Department of Energy
National Nuclear Security AdministrationDE-NA-0003525
National Nuclear Security Administration

    Fingerprint

    Dive into the research topics of 'Simulation of Stark-broadened Hydrogen Balmer-line Shapes for da White Dwarf Synthetic Spectra'. Together they form a unique fingerprint.

    Cite this