{
  "id": "2501.07654",
  "version": "v1",
  "published": "2025-01-13T19:30:33.000Z",
  "updated": "2025-01-13T19:30:33.000Z",
  "title": "Numerical and Physical Challenges to Nebular Spectroscopy in Thermonuclear Supernovae",
  "authors": [
    "P. Hoeflich",
    "E. Fereidouni",
    "A. Fisher",
    "T. Mera",
    "C. Ashall",
    "P. Brown",
    "E. Baron",
    "J. DerKacy",
    "T. Diamond",
    "M. Shabandeh",
    "M. Stritzinger"
  ],
  "comment": "10 Pages, 5 figures submitted Dec. 2024, revised Jan. 3, accepted Jan. 6th (Journal of Physics, Conference Series, in press)",
  "categories": [
    "astro-ph.SR",
    "astro-ph.HE",
    "physics.space-ph"
  ],
  "abstract": "Thermodynamical explosions of White Dwarfs (WD)are one of the keys to high precision cosmology. Nebular spectra, namely mid-infrared (MIR) with JWST are an effective tool to probe for the multi-dimensional imprints of the explosion physics of WDs and their progenitor systems but also pose a challenge for simulations. What we observe as SNe Ia are low-energy photons, namely light curves, and spectra detected some days to years after the explosion. The light is emitted from a rapidly expanding envelope consisting of a low-density and low-temperature plasma with atomic population numbers far from thermodynamical equilibrium. SNe Ia are powered radioactive decays which produce hard X- and gamma-rays and MeV leptons which are converted within the ejecta to low-energy photons. We find that the optical and IR nebular spectra depend sensitively on the proper treatment of the physical conversion of high to low energies. The low-energy photons produced by forbidden line transitions originate from a mostly optically thin envelope. However, the UV is optically thick because of a quasi-continuum formed by allowed lines and bound-free transitions even several years after the explosion. We find that stimulated recombination limits the over-ionization of high ions with populations governed by the far UV. The requirements to simulate nebular spectra are well beyond both classical stellar atmospheres and nebulae. Using our full non-LTE HYDrodynamical RAdiation code (HYDRA) as a test-bed, the sensitivity on the physics on synthetic spectra are demonstrated using observations as a benchmark. At some examples, we establish the power of high-precision nebular spectroscopy as quantitative tool. Centrally ignited, off-center delayed-detonation near Chandrasekhar-mass models can reproduce line-ratios and line profiles of Branch-normal and underluminous SNe Ia observed with JWST.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2025-01-13T19:30:33.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "nebular spectroscopy",
      "thermonuclear supernovae",
      "physical challenges",
      "low-energy photons",
      "nebular spectra"
    ],
    "tags": [
      "conference paper"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 10,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}