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2020A&A...642A..33D - Astronomy and Astrophysics, volume 642A, 33-33 (2020/10-1)

Radiative-transfer modeling of nebular-phase type II supernovae. Dependencies on progenitor and explosion properties.


Abstract (from CDS):

Nebular phase spectra of core-collapse supernovae (SNe) provide critical and unique information on the progenitor massive star and its explosion. We present a set of one-dimensional steady-state non-local thermodynamic equilibrium radiative transfer calculations of typeII SNe at 300 d after explosion. Guided by the results obtained from a large set of stellar evolution simulations, we craft ejecta models for typeII SNe from the explosion of a 12, 15, 20, and 25M star. The ejecta density structure and kinetic energy, the 56Ni mass, and the level of chemical mixing are parametrized. Our model spectra are sensitive to the adopted line Doppler width, a phenomenon we associate with the overlap of FeII and OI lines with Lyα and Lyβ. Our spectra show a strong sensitivity to 56Ni mixing since it determines where decay power is absorbed. Even at 300 d after explosion, the H-rich layers reprocess the radiation from the inner metal rich layers.In a given progenitor model, variations in 56Ni mass and distribution impact the ejecta ionization, which can modulate the strength of all lines. Such ionization shifts can quench CaII line emission.In our set of models, the [OI] λλ 6300, 6364 doublet strength is the most robust signature of progenitor mass. However, we emphasize that convective shell merging in the progenitor massive star interior can pollute the O-rich shell with Ca, which would weaken the OI doublet flux in the resulting nebular SNII spectrum. This process may occur in nature, with a greater occurrence in higher mass progenitors, and this may explain in part the preponderance of progenitor masses below 17M that are inferred from nebular spectra.

Abstract Copyright: © L. Dessart and D. J. Hillier 2020

Journal keyword(s): radiative transfer - line: formation - supernovae: general

Simbad objects: 7

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