Radiative-transfer models for explosions from rotating and non-rotating single WC stars: Implications for SN 1998bw and LGRB/SNe

Luc Dessart, D. John Hillier, Sung Chul Yoon, Roni Waldman, Eli Livne

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29 Scopus citations

Abstract

Using 1D, non-local thermodynamic equilibrium and time-dependent radiative transfer simulations, we study the ejecta properties required to match the early- and late-time photometric and spectroscopic properties of supernovae (SNe) associated with long-duration γ-ray bursts (LGRBs). Matching the short rise time, narrow light curve peak and extremely broad spectral lines of SN 1998bw requires a model with 3 Mejecta but a high explosion energy of a few 1052 erg and 0.5 M of 56Ni. The relatively high luminosity, presence of narrow spectral lines of intermediate mass elements, and low ionisation at the nebular stage, however, are matched with a more standard C-rich Wolf-Rayet (WR) star explosion, an ejecta of 10 M, an explosion energy 1051 erg, and only 0.1 M of 56Ni. As the two models are mutually exclusive, the breaking of spherical symmetry is essential to match the early- and late-time photometric and spectroscopic properties of SN 1998bw. This conclusion confirms the notion that the ejecta of SN 1998bw is highly aspherical on large scales. More generally, with asphericity, the energetics and 56Ni masses of LGRB/SNe are reduced and their ejecta masses are increased, favouring a massive fast-rotating Wolf-Rayet star progenitor. Contrary to persisting claims in favour of the proto-magnetar model for LGRB/SNe, such progenitor/ejecta properties are compatible with collapsar formation. Ejecta properties of LGRB/SNe inferred from 1D radiative-transfer modelling are fundamentally flawed.

Original languageEnglish
Article numberA51
JournalAstronomy and Astrophysics
Volume603
DOIs
StatePublished - 1 Jul 2017

Bibliographical note

Publisher Copyright:
© ESO, 2017.

Keywords

  • Hydrodynamics
  • Radiative transfer
  • Supernovae: general

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