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Title: Helium at white dwarf photospheric conditions: preliminary laboratory results.

Abstract

Abstract not provided.

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1392749
Report Number(s):
SAND2016-8921C
647285
DOE Contract Number:
AC04-94AL85000
Resource Type:
Conference
Resource Relation:
Conference: Proposed for presentation at the European White Dwarf Workshop held July 25-29, 2016 in Coventry, United Kingdom.
Country of Publication:
United States
Language:
English

Citation Formats

Schaeuble, Marc-Andre, Falcon, Ross Edward, Gomez, Thomas, Winget, Donald E, Montgomery, Michael Houston, and Bailey, James E. Helium at white dwarf photospheric conditions: preliminary laboratory results.. United States: N. p., 2016. Web.
Schaeuble, Marc-Andre, Falcon, Ross Edward, Gomez, Thomas, Winget, Donald E, Montgomery, Michael Houston, & Bailey, James E. Helium at white dwarf photospheric conditions: preliminary laboratory results.. United States.
Schaeuble, Marc-Andre, Falcon, Ross Edward, Gomez, Thomas, Winget, Donald E, Montgomery, Michael Houston, and Bailey, James E. 2016. "Helium at white dwarf photospheric conditions: preliminary laboratory results.". United States. doi:. https://www.osti.gov/servlets/purl/1392749.
@article{osti_1392749,
title = {Helium at white dwarf photospheric conditions: preliminary laboratory results.},
author = {Schaeuble, Marc-Andre and Falcon, Ross Edward and Gomez, Thomas and Winget, Donald E and Montgomery, Michael Houston and Bailey, James E.},
abstractNote = {Abstract not provided.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2016,
month = 9
}

Conference:
Other availability
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  • Abstract not provided.
  • Cited by 2
  • We spectroscopically measure multiple hydrogen Balmer line profiles from laboratory plasmas to investigate the theoretical line profiles used in white dwarf (WD) atmosphere models. X-ray radiation produced at the Z Pulsed Power Facility at Sandia National Laboratories initiates plasma formation in a hydrogen-filled gas cell, replicating WD photospheric conditions. We also present time-resolved measurements of Hβ and fit this line using different theoretical line profiles to diagnose electron density, n e, and n = 2 level population, n 2. Aided by synthetic tests, we characterize the validity of our diagnostic method for this experimental platform. During a single experiment, wemore » infer a continuous range of electron densities increasing from n e ~ 4 to ~30 × 10 16 cm -3 throughout a 120-ns evolution of our plasma. Also, we observe n 2 to be initially elevated with respect to local thermodynamic equilibrium (LTE); it then equilibrates within ~55 ns to become consistent with LTE. This also supports our electron-temperature determination of T e ~ 1.3 eV (~15,000 K) after this time. At n e≲ 10 17 cm -3, we find that computer-simulation-based line-profile calculations provide better fits (lower reduced χ 2) than the line profiles currently used in the WD astronomy community. The inferred conditions, however, are in good quantitative agreement. Lastly, this work establishes an experimental foundation for the future investigation of relative shapes and strengths between different hydrogen Balmer lines.« less
  • We spectroscopically measure multiple hydrogen Balmer line profiles from laboratory plasmas to investigate the theoretical line profiles used in white dwarf (WD) atmosphere models. X-ray radiation produced at the Z Pulsed Power Facility at Sandia National Laboratories initiates plasma formation in a hydrogen-filled gas cell, replicating WD photospheric conditions. Here we present time-resolved measurements of Hβ and fit this line using different theoretical line profiles to diagnose electron density, n{sub e}, and n = 2 level population, n{sub 2}. Aided by synthetic tests, we characterize the validity of our diagnostic method for this experimental platform. During a single experiment, wemore » infer a continuous range of electron densities increasing from n{sub e} ∼ 4 to ∼30 × 10{sup 16} cm{sup −3} throughout a 120-ns evolution of our plasma. Also, we observe n{sub 2} to be initially elevated with respect to local thermodynamic equilibrium (LTE); it then equilibrates within ∼55 ns to become consistent with LTE. This supports our electron-temperature determination of T{sub e} ∼ 1.3 eV (∼15,000 K) after this time. At n{sub e} ≳ 10{sup 17} cm{sup −3}, we find that computer-simulation-based line-profile calculations provide better fits (lower reduced χ{sup 2}) than the line profiles currently used in the WD astronomy community. The inferred conditions, however, are in good quantitative agreement. This work establishes an experimental foundation for the future investigation of relative shapes and strengths between different hydrogen Balmer lines.« less
  • In order to see if there could be agreement between results of stellar evolution theory and those of nonradial pulsation theory, calculations of white dwarf models have been made for hydrogen surface masses of 10/sup -4/ solar masses. Earlier results indicated that surface masses greater than 10/sup -8/ solar masses would not allow nonradial pulsations, even though all the driving and damping is in surface layers only 10/sup -12/ of the mass thick. It is shown that the surface mass of hydrogen in the pulsating white dwarfs (ZZ Ceti variables) can be any value as long as it is thickmore » enough to contain the surface convection zone. 10 refs., 6 figs.« less