2006ApJ...640..854M -
Astrophys. J., 640, 854-877 (2006/April-1)
Nebular spectra of SN 1998bw revisited: detailed study by one- and two-dimensional models.
MAEDA K., NOMOTO K., MAZZALI P.A. and DENG J.
Abstract (from CDS):
Refined one- and two-dimensional models for the nebular spectra of the hyperenergetic Type Ic supernova (SN) 1998bw, associated with the gamma-ray burst GRB 980425, from 125 to 376 days after B-band maximum are presented. One-dimensional, spherically symmetric spectrum synthesis calculations show that reproducing features in the observed spectra, i.e., the sharply peaked [O I] λ6300 doublet and Mg I] λ4570 emission and the broad [Fe II] blend around 5200 Å, requires the existence of a high-density O-rich core expanding at low velocities (≲8000 km/s) and of Fe-rich material moving faster than the O-rich material. Synthetic spectra at late phases from aspherical (bipolar) explosion models are also computed with a two-dimensional spectrum synthesis code. The above features are naturally explained by the aspherical model if the explosion is viewed from a direction close to the axis of symmetry (∼30°), since the aspherical model yields a high-density O-rich region confined along the equatorial axis. By examining a large parameter space (in energy and mass), our best model gives the following physical quantities: the kinetic energy E51≡EK/1051 ergs ≳8-12 and the main-sequence mass of the progenitor star Mms≳30-35 M☉. The temporal spectral evolution of SN 1998bw also indicates mixing among Fe-, O-, and C-rich regions, and highly clumpy structure.
Abstract Copyright:
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Journal keyword(s):
Gamma Rays: Bursts - Line: Profiles - Nuclear Reactions, Nucleosynthesis, Abundances - Stars: Supernovae: Individual: Alphanumeric: SN 1998bw
Simbad objects:
7
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