The Astrophysical Journal · 1992 · 142 citations · 0 references
Natural SciencesAstronomyPhysicsAstrophysicsNuclear PhysicsPlasma PhysicsNucleosynthesisSolar Ultraviolet EmissionActive Galactic Nuclei ContributionActive Galactic Nuclei Ultraviolet EmissionEquation Of State Of Supernova MatterGas IonizationType Ia Supernovae
Gamma‑ray deposition and nonthermal excitation are particularly relevant for Type Ia supernovae. The study aims to compute γ‑ray deposition and nonthermal excitation in supernovae, providing ionization, excitation, and heating rates for various composition zones and applying these results to hydrogen ionization and Hα line formation. The authors solve the Spencer‑Fano equation to obtain γ‑ray deposition, derive analytical expressions for ionization, excitation, and heating rates across composition zones, and compute the fraction of energy reemitted as UV photons above 3.4 eV. The model reproduces SN 1987A observations, showing that UV photon absorption in the Balmer continuum dominates excitation before ~500 days, while direct nonthermal excitation from the ground state dominates afterward. Publication: The Astrophysical Journal, May 1992, DOI 10.1086/171311.
view Abstract Citations (118) References (73) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Gamma-Ray Deposition and Nonthermal Excitation in Supernovae Kozma, Cecilia ; Fransson, Claes Abstract We calculate the γ-ray deposition in supernovae by solving the Spencer-Fano equation. Ionization, excitation, and heating rates are presented for the different chemical composition zones of a core collapse supernova, as well as for a solar composition applicable to for example, active galactic nuclei. We also discuss the thermalization in pure helium, oxygen, and iron plasmas. The latter is of particular interest for Type Ia supernovae. Convenient analytical expressions are given to facilitate the use of these results for the calculation of the physical conditions and emission from supernovae. We also discuss the spectral characteristics of the emission following nonthermal excitation and ionization in the supernova. In particular, we calculate the fraction of the absorbed γ-ray energy which is reemitted as UV photons with energy above 3.4 eV, the n = 2 threshold of hydrogen. We apply these results to the ionization of hydrogen and the formation of the Hα line. Good qualitative and quantitative agreement between the model and observations of SN 1987A are found. In particular, we find that absorption of UV photons in the Balmer continuum dominates the excitation before ~500 days, while direct nonthermal excitation from the ground state dominates thereafter. We also discuss how the wing of the Hα line can be used as a probe of the density in the envelope. Publication: The Astrophysical Journal Pub Date: May 1992 DOI: 10.1086/171311 Bibcode: 1992ApJ...390..602K Keywords: Gamma Rays; Stellar Composition; Stellar Cores; Supernova 1987a; Supernovae; Thermalization (Energy Absorption); Chemical Composition; Electron Energy; Gas Ionization; Gravitational Collapse; Astrophysics; ATOMIC PROCESSES; GAMMA RAYS: THEORY; STARS: INDIVIDUAL ALPHANUMERIC: SN 1987A; STARS: SUPERNOVAE: GENERAL full text sources ADS | data products SIMBAD (1) NED (1)