Research & Reports

Current Projects

The projects explored within WCAPP are varied. Below, we list the astrophysical problems, the suspected problem with atomic processes, and how to answer those problems.

Solar Opacity (SNL)

Problem: The solar convection zone boundary measured by helioseismology is discrepant with the standard solar model. This discrepancy can be resolved with a 14% increase in the Rosseland Mean Opacity.

Hypothesis: Opacity is incorrectly modeled.

Method: Heat a sample of iron to solar interior conditions to measure opacity in absorption (see Bailey et al. 2015).

White Dwarf Spectral Line-Broadening (UT)

Problem: Spectroscopic method of determining white dwarf masses is discrepant with gravitational redshift and orbital determination of mass.

Hypothesis: Spectral Line Broadening is inaccurate.

Method: Heat samples of hydrogen and helium gasses to white dwarf atmospheric conditions and measure emission and absorption spectra and compare to models (see Montgomery et al. 2015.

A telescope image of a black object emitting blue light

Efficiency of RAD (SNL)

Problem: Is Resonant Auger Destruction (RAD) the explanation for missing iron lines in accretion disks?

Hypothesis: RAD is not 100% efficient in destroying emission lines

Method: Heat sample of silicon in high-radiation environment, measure spectrum in emission and absorption to measure relative strengths of spectral lines and how they are affected by RAD (see Loisel et al. 2017).

A telescope image of a bright object surrounded by brown disks

Heating in Accretion Disks (UNR)

Problem: Accretion disk models rely on untested atomic kinetics models.

Hypothesis: The current models (XSTAR, CLOUDY) are not accurately capturing atomic kinetics properly.

Method: Heat neon to accretion disk conditions and compare charge-states and line strengths with the predictions of astrophysical codes (Mancini et al. 2017).

Publications

2025

Overview of oxygen opacity experiments at the National Ignition Facility and investigation of potential systematic errors. Mayes, D. C., Hobbs, B. A., Heeter, R. F., Perry, T. S., Johns, H. M., Opachich, Y. P., Hoheberger, M., Bradley, P. A., Dutra, E. C., Fontes, C. J., Gallardo-Diaz, E., Montgomery, M. H., Robey, H. F., Wallace, M. S. and Winget, D. E., High Energy Density Physics, vol. 55, id.101177, 2025.
Increased Lya Opacity in White Dwarf Photosphere from Transient H- Resonances. Gomez, T. A., Zammit, Mark C., White, Jackson R., Stambulchik, Evgeny, Hubeny, Ivan, Bray, Igor, Fontes, Christopher J., Montgomery, Michael H., Dunlap, Bart H., and Winget, D. W., The Astrophysical Journal, vol. 986, no. 1, id.52, 24 pp., 2025.
Pseudoatom Molecular Dynamics Plasma Microfields. White, J. R., Fontes, C. J., Zammit, M. Z., Gomez, T. A., and Starrett, C. E., High Energy Density Physics, vol. 54, id. 101173, 2025.

2024

Experimental methods to test photoionized plasma models in emission. Cho, P. B., Loisel, G. P., Bailey, J. E., Dunham, G. S., Mayes, D. C., Nagayama, T., and Fontes, C. J., Physics of Plasma, vol. 31, no. 12, id.122902, 9 pp., 2024.
Modeling Competing Line-broadening Mechanisms in Neutron Star Atmospheres: Interference between Motional Stark and Ion Broadening. Gomez, Thomas A., Zammit, Mark C., Bray, Igor, Fontes, Christopher J., White, Jackson R., and Johnson, Harold, The Astrophysical Journal, vol. 977, no. 1, pp. 11, 2024.
Development of Improved Higher-Order Correction for the NIF Opacity Spectrometer. Hobbs, B. A., Mayes, D. C., Heeter, R. F., Bradley, P. A., Dutra, E. C., Fontes, C. J., Gallardo-Diaz, E., Hohenberger, M., Johns, H. M., Opachich, Y. P., Robey, H. F., Stoupin, S., Wallace, M. S., Webster, L. G., Montgomery, M. H., Perry, T. S., and Winget, D. E., High Energy Density Physics/Review of Scientific Instruments, vol. 95, (8): 083535, 2024.
Hunting for Polluted White Dwarfs and Other Treasures with Gaia XP Spectra and Unsupervised Machine Learning. Kao, Malia, Hawkins, Keith, Rogers, Laura K., Bonsor, Amy, Dunlap, Bart H., Sanders, Jason L., Montgomery, M. H., and Winget, D. E., The Astrophysical Journal, vol. 970, no. 2., 2024.
Development of spatially and temporally resolved electron density measurements for the assessment of radiation hydrodynamics simulations of laboratory X-ray photoionized plasmas. Jaar, G. S., Swanson, K. J., Mancini, R. C., Astanovitskiy, A. L., and Mayes, D. C., High Energy Density Physics, vol. 51, id. 101095, 2024.
Impact of penetrating collisions of plasma ions on spectral line shapes. Gomez, Thomas A., Stambulchik, Evgeny, and White, Jackson. Physical Review A, vol. 109, id.052804, 2024.
A Quantum Mechanical Treatment of Electron Broadening in Strong Magnetic Fields. II. Large Enhancements due to Exchange Interactions. Gomez, Thomas A., Zammit, Mark C., Bray, Igor, Fontes, Christopher J., and White, Jackson R., The Astrophysical Journal, vol. 963, no. 1, id 62, 2024.
Fluid Mixing during Phase Separation in Crystallizing White Dwarfs. Montgomery, M. H. and Dunlap, B. H., The Astrophysical Journal, vol. 961, no. 2, id. 197, 2024.
Correction to: Asteroseismological analysis of the polluted ZZ Ceti star G 29 - 38 with TESS. Uzundag, Murat, De Gerónimo, Francisco C., Córsico, Alejandro H., Silvotti, Roberto, Bradley, Paul A., Montgomery, Michael H., Catelan, Márcio, Toloza, Odette, Bell, Keaton J., Kepler, S. O., Althaus, Leandro G., Kleinman, Scot J., Kilic, Mukremin, Mullally, Susan E., Gänsicke, Boris T., Bąkowska, Karolina, Barber, Sam, and Nitta, Atsuko, Monthly Notices of the Royal Astronomical Society, vol 527, no. 2, 2024.

2023

High-precision room temperature Fe opacity measurements at 1000-2000eV photon energies. Kao, Malia L., Loisel, Guillaume P., Bailey, James E., Lake, Patrick W., Gard, Paul D., Rochau, Gregory A., Burns, George R., Wampler, William R., Huang, Haibo, and Weir, Michael N., High Energy Density Physics, vol. 49, 101064, 2023.
Asteroseismological analysis of the polluted ZZ Ceti star G 29 - 38 with TESS. Uzundag, M., De Gerónimo, F. C., Córsico, A. H., Silvotti, R., Bradley, P. A., Montgomery, M. H., Catelan, M., Toloza, O., Bell, K. J., Kepler, S. O., Althaus, L. G., Kleinman, S. J., Kilic, M., Mullally, S. E., Gänsicke, B. T., Bąkowska, K., Barber, S., Nitta, A. Monthly Notices of the Royal Astronomical Society, vol. 526, no. 2, pp. 2846-2862, 2023.
Chemical cartography with LAMOST and Gaia reveal azimuthal and spiral structure in the Galactic disc. Hawkins, K. A., Monthly Notices of the Royal Astronomical Society, vol. 525, no. 3, pp. 3318-3329, Nov. 2023.
A Quantum-mechanical Treatment of Electron Broadening in Strong Magnetic Fields. Gomez, Thomas A., Zammit, Mark C., Fontes, Christopher J., and White, Jackson R., ApJ, vol. 951, no. 2, 2023.

2022

Measuring He I Stark Line Shapes in the Laboratory to Examine Differences in Photometric and Spectroscopic DB White Dwarf Masses. Schaeuble, M.-A., Nagayama, T., Bailey, J. E., Gigosos, M. A., Florido, R., Blouin, S., Gomez, T. A., Dunlap, B., Montgomery, M. H., and Winget, D. E., ApJ, vol. 940, no. 2, 2022.
Quadratic Zeeman effect in hydrogen at 2–3 MG magnetic fields. Ivanov, V. V., Mancini, R. C., Huerta, N. A., Swanson, K. J., Winget, D. E., Montgomery, M. H., Golovkin, I. E., Hariharan, H. K. and Berbel, Z. S., Physical Review E, vol. 106, no. 4, id 045206, 2022.
Kepler and TESS Observations of PG 1159-035. Oliveira da Rosa, Gabriela, Kepler, S. O., Córsico, Alejandro H., Costa, J. E. S., Hermes, J. J., Kawaler, S. D., Bell, Keaton J., Montgomery, M. H., Provencal, J. L., Winget, D. E., Handler, G., Dunlap, Bart, Clemens, J. C., and Uzundag, Murat. ApJ, vol. 936, no. 2, 2022.
Simulation of Stark Broadened Hydrogen Balmer Line Shapes for DA White Dwarf Synthetic Spectra. Cho, P., Gomez, T. A., Montgomery, M. H., Dunlap, B. H., Fitz Axen, M., Hobbs, B., Hubeny, I., and Winget, D. E., ApJ, vol. 927, no. 1, 2022.
The Pulsating Helium-atmosphere White Dwarfs. I. New DBVs from the Sloan Digital Sky Survey. Vanderbosch, Z. P., Hermes, J. J., Winget, D. E., Montgomery, M., H., Bell, K. J., Nitta, A., and Kepler, S. O., ApJ, vol. 927, no. 2, 2022.
Hydrogen Line Shape Uncertainties in White Dwarf Model Atmospheres. Montgomery, M. H., Dunlap, B. H., Cho, P. B., and Gomez, T. A., 2022.

2021

All-Order Full-Coulomb Quantum Spectral Line-Shape Calculations. Gomez, T. A., Nagayama, T., Cho, P., Zammit, M. C., Fontes, C. J., Kilcrease, D. P., Bray, I., Hubeny, I., Dunlap, B., Montgomery, M. H., and Winget, D. E., Physical Review Letters, vol. 127, no. 23, id. 235001, 2021.
Observation of ionization trends in a laboratory photoionized plasma experiment at Z. Mayes, D. C., Mancini, R. C., Lockard, T. E., Hall, I. M., Bailey, J. E., Loisel, G. P., Nagayama, T., Rochau, G. A., and Liedahl, D. A., Phys Rev E, vol. 104, no. 3, p. 035202, 2021.
I Spy Transits and Pulsations: Empirical Variability in White Dwarfs Using Gaia and the Zwicky Transient Facility. Guidry, J. A., Vanderbosch, Z. P., Hermes, J. J., Barlow, B. N., Lopez, I. D., Boudreaux, T. M., Corcoran, K. A., Dunlap, B. H., Bell, K. J., Montgomery, M. H., Heintz, T. M., Winget, D. E., Winget, K. I., and Kuehne, J. W., ApJ, vol. 912, no. 2, id.125, 24 pp., 2021.
Experimental methods for laboratory measurements of helium spectral line broadening in white dwarf photospheres. Schaeuble, M.-A., Nagayama, T., Bailey, J. E., Dunlap, B. H., and Patel, S., Physics of Plasmas, vol. 28, no. 6, article id.062902, 2021.
The Pulsating White Dwarf G117-B15A: Still the Most Stable Optical Clock Known. Kepler, S. O., Winget, D. E., Vanderbosch, Z. P., Castanheira, B. G., Hermes, J. J., Bell, K. J., Mullally, F., Romero, A. D., Montgomery, M. H., DeGennaro, S., Winget, K. I., Chandler, D., Jeffery, E. J., Fritzen, J. K., Williams, K. A., Chote, P., and Zola, S., ApJ, vol. 906, no. 1, id. 7, 10 pp., 2021.

2020 & prior

Illuminating White Dwarf Spectra through Laboratory Experiments at Cosmic Conditions. Winget, D. E., Montgomery, M. H., Dunlap, B. H., Cho, P. B., Schaeuble, M.-A., and Gomez, T. A., High Energy Density Physics, vol. 37, id. 100853, 2020.
WD1032 + 011, an inflated brown dwarf in an old eclipsing binary with a white dwarf. Casewell, S. L., Belardi, C., Parsons, S. G., Littlefair, S. P., Braker, I. P., Hermes, J. J., Debes, J., Vanderbosch, Z., Burleigh, M. R., Gänsicke, B. T., Dhillon, V. S., Marsh, T. R., Winget, D. E., and Winget, K. I., Monthly Notices of the Royal Astronomical Society, vol. 497, no. 3, pp. 3571-3580, 2020.
A White Dwarf with Transiting Circumstellar Material Far outside the Roche Limit. Vanderbosch, Z., Hermes, J. J., Dennihy, E., Dunlap, B. H., Izquierdo, P., Tremblay, P.-E., Cho, P. B., Gänsicke, B. T., Toloza, O., Bell, K. J., Montgomery, M. H., and Winget, D. E., ApJ, vol. 897, no. 2, id. 171, 2020.
X-ray heating and electron temperature of laboratory photoionized plasmas. Mancini, R. C., Lockard, T. E., Mayes, D. C., Hall, I. M., Loisel, G. P., Bailey, J. E., Rochau, G. A., Abdallah Jr., J., Golovkin, I. E., and Liedahl, D., Phys Rev E, vol. 101, no. 5, p. 051201, 2020.
Limits on Mode Coherence in Pulsating DA White Dwarfs Due to a Nonstatic Convection Zone. Montgomery, M. H., Hermes, J. J., Winget, D. E., Dunlap, B. H., and Bell, K. J., ApJ, vol. 890, no. 1, id.11, 10 pp., 2020.
Hb and Hy Absorption-line Profile Inconsistencies in Laboratory Experiments Performed at White Dwarf Photosphere Conditions. Schaeuble, M.-A., Nagayama, T., Bailey, J. E., Gomez, T. A., Montgomery, M. H., and Winget, D. E., ApJ, vol. 885, no. 1, id. 86, 12 pp., 2019.
Density-matrix correlations in the relaxation theory of electron broadening. Gomez, T. A., Nagayama, T., Kilcrease, D. P., Montgomery, M. H., and Winget, D. E., 2018, Phys. Rev. A, vol. 98, no. 1, id. 01250, 2018.
WDEC: A Code for Modeling White Dwarf Structure and Pulsations. Bischoff-Kim, A. and Montgomery, M. H., ApJ, vol. 155, no. 5, id. 187, 8 pp., 2018.
Matrix Methods for Solving Hartree-Fock Equations in Atomic Structure Calculations and Line Broadening. Gomez, T. A., Nagayama, T., Fontes, C., Kilcrease, D. P., Hansen, S., Montgomery, M. H., and Winget, D. E., Atoms, vol. 6, no. 2, p. 22., 2018.
Effect of higher-order multipole moments on the Stark line shape. Gomez, T. A., Nagayama, T., Kilcrease, D. P., Montgomery, M. H., and Winget, D. E., Phys. Rev. A, vol. 94, no. 2, id. 022501, 2016.
Laboratory Measurements of White Dwarf Photospheric Spectral Lines: H-beta. Falcon, R. E., Rochau, G. A., Bailey, J. E., Gomez, T. A., Montgomery, M. H., Winget, D. E., and Nagayama, T., ApJ, vol. 806, no. 2, id. 214, 11 pp., 2015.
An experimental platform for creating white dwarf photospheres in the laboratory: Preliminary results. Montgomery, M. H., Falcon, R. E., Rochau, G. A., Bailey, J. E., Gomez, T. A., Carlson, A. L., Bliss, D. E., Nagayama, T., Stein, M., and Winget, D. E., High Energy Density Physics, vol. 17, pp.168-174, 2015.
An experimental platform for creating white dwarf photospheres in the laboratory. Falcon, R. E., Rochau, G. A., Bailey, J. E., Ellis, J. L., Carlson, A. L., Gomez, T. A., Montgomery, M. H., Winget, D. E., Chen, E. Y., Gomez, M. R., and Nash, T. J., High Energy Density Physics, vol. 9, no. 1, pp. 82-90, 2013.
A Gravitational Redshift Determination of the Mean Mass of White Dwarfs: DBA and DB Stars. Falcon, R. E., Winget, D. E., Montgomery, M. H., and Williams, K. A., ApJ, vol. 757, no. 2, id. 116, 9 pp., 2012.
A Gravitational Redshift Determination of the Mean Mass of White Dwarfs. DA Stars. Falcon, R. E., Winget, D. E., Montgomery, M. H., and Williams, K. A., ApJ, vol. 712, no. 1, pp. 585-595, 2010.

Reports

National Nuclear Security Administration (NNSA)

Research Performance Progress Reports (RPPR) are management reports which provide information on project status, and are submitted to NNSA 90 days after end of each budget period.

Year 6 - RPPR 2024

Year 5 - RPPR 2023 (Exempt, No Reporting)