English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

Recent stellar evolutionary calculations of low-metallicity massivefast-rotating main-sequence stars yield iron cores at collapse endowed withhigh angular momentum. It is thought that high angular momentum and black holeformation are critical ingredients of the collapsar model of long-softgamma-ray bursts (GRBs). Here, we present 2D multi-group,flux-limited-diffusion MHD simulations of the collapse, bounce, and immediatepost-bounce phases of a 35-Msun collapsar-candidate model of Woosley & Heger.We find that, provided the magneto-rotational instability (MRI) operates in thedifferentially-rotating surface layers of the millisecond-period neutron star,a magnetically-driven explosion ensues during the proto-neutron star phase, inthe form of a baryon-loaded non-relativistic jet, and that a black hole,central to the collapsar model, does not form. Paradoxically, and although muchuncertainty surrounds stellar mass loss, angular momentum transport, magneticfields, and the MRI, current models of chemically homogeneous evolution at lowmetallicity yield massive stars with iron cores that may have too much angularmomentum to avoid a magnetically-driven, hypernova-like, explosion in theimmediate post-bounce phase. We surmise that fast rotation in the iron core mayinhibit, rather than enable, collapsar formation, which requires a largeangular momentum not in the core but above it. Variations in the angularmomentum distribution of massive stars at core collapse might explain both thediversity of Type Ic supernovae/hypernovae and their possible association witha GRB. A corollary might be that, rather than the progenitor mass, the angularmomentum distribution, through its effect on magnetic field amplification,distinguishes these outcomes.

The Proto-neutron Star Phase of the Collapsar Model and the Route to Long-soft Gamma-ray Bursts and Hypernovae