Multi-dimensional NLTE radiative transfer for a double detonation Type Ia explosion model in the photospheric phase
8 affiliations
- 1School of Mathematics and Physics, Queen’s University Belfast , University Road, Belfast BT7 1NN ,
- 2School of Physics, Trinity College Dublin , The University of Dublin, Dublin 2 ,
- 3Oregon State University Department of Physics, , 301 Weniger Hall, Corvallis, OR 97331-6507 ,
- 4Max-Planck-Institut für Astrophysik , Karl-Schwarzschild-Str. 1, D-85748, Garching ,
- 5Heidelberger Institut für Theoretische Studien , Schloss-Wolfsbrunnenweg 35, D-69118, Heidelberg ,
- 6Zentrum für Astronomie der Universität Heidelberg, Institut für Theoretische Astrophysik , Philosophenweg 12, D-69120 Heidelberg ,
- 7Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut, Mönchhofstr , 12–14, 69120 Heidelberg ,
- 8Research School of Astronomy and Astrophysics, Australian National University , Canberra ACT 2611 ,
Abstract
Previous radiative transfer calculations have shown that both multi-dimensionality and NLTE (non local thermodynamic equilibrium) effects impact the synthetic observables predicted for Type Ia supernova explosion models. Here we carry out a 2D NLTE radiative transfer simulation in the photospheric phase for a double detonation model with a 1 M⊙ carbon–oxygen core and 0.02 M⊙ helium shell. The predicted observables demonstrate that departures from both spherical symmetry and local thermodynamic equilibrium are significant on scales relevant to comparisons with observations. The NLTE treatment leads to a bluer spectral energy distribution, more slowly declining optical-band light curves, changes to the near-infrared light curve shapes, and differences in the evolution of key spectral features. Although substantial viewing-angle variation is predicted for the model, the scale of the variation is not significantly impacted by NLTE effects up to peak. However, after peak, our 2D NLTE simulation retains a strong viewing-angle dependence in its spectra whereas our simulation of the same ejecta model using an approximate NLTE treatment predicts significantly reduced spectroscopic viewing-angle variation. The NLTE treatment leads to improved agreement with normal Type Ia supernovae, primarily due to the increased ionisation state of the simulation, although the absence of a secondary near-infrared maximum suggests that the ejecta remain over-ionised relative to observations after peak. Despite the improved agreement, many viewing angles still show excessive line blanketing, suggesting that the 0.02 M⊙ helium-shell mass of the current model is too large to reproduce normal Type Ia supernovae over the majority of lines of sight.
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BibTeX
@article{callan2026multidimensional,
title = {{Multi-dimensional NLTE radiative transfer for a double detonation Type Ia explosion model in the photospheric phase}},
author = {F P Callan and L J Shingles and S A Sim and C E Collins and J M Pollin and R Pakmor and S Gronow and F K Röpke and A Holas and I R Seitenzahl},
journal = {Monthly Notices of the Royal Astronomical Society},
year = {2026},
month = oct,
doi = {10.1093/mnras/stag2038},
url = {https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stag2038/8997909},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Multi-dimensional NLTE radiative transfer for a double detonation Type Ia explosion model in the photospheric phase
AU - F P Callan
AU - L J Shingles
AU - S A Sim
AU - C E Collins
AU - J M Pollin
AU - R Pakmor
AU - S Gronow
AU - F K Röpke
AU - A Holas
AU - I R Seitenzahl
PY - 2026
DA - 2026/10/24
JO - Monthly Notices of the Royal Astronomical Society
DO - 10.1093/mnras/stag2038
UR - https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stag2038/8997909
AB - Previous radiative transfer calculations have shown that both multi-dimensionality and NLTE (non local thermodynamic equilibrium) effects impact the synthetic observables predicted for Type Ia supernova explosion models. Here we carry out a 2D NLTE radiative transfer simulation in the photospheric phase for a double detonation model with a 1 M⊙ carbon–oxygen core and 0.02 M⊙ helium shell. The predicted observables demonstrate that departures from both spherical symmetry and local thermodynamic equilibrium are significant on scales relevant to comparisons with observations. The NLTE treatment leads to a bluer spectral energy distribution, more slowly declining optical-band light curves, changes to the near-infrared light curve shapes, and differences in the evolution of key spectral features. Although substantial viewing-angle variation is predicted for the model, the scale of the variation is not significantly impacted by NLTE effects up to peak. However, after peak, our 2D NLTE simulation retains a strong viewing-angle dependence in its spectra whereas our simulation of the same ejecta model using an approximate NLTE treatment predicts significantly reduced spectroscopic viewing-angle variation. The NLTE treatment leads to improved agreement with normal Type Ia supernovae, primarily due to the increased ionisation state of the simulation, although the absence of a secondary near-infrared maximum suggests that the ejecta remain over-ionised relative to observations after peak. Despite the improved agreement, many viewing angles still show excessive line blanketing, suggesting that the 0.02 M⊙ helium-shell mass of the current model is too large to reproduce normal Type Ia supernovae over the majority of lines of sight.
SN - 0035-8711
SN - 1365-2966
ER -