The Arduous Journey to Black-Hole Formation in Potential Gamma-Ray Burst Progenitors

Abstract

We present a quantitative study on the properties at death of fast-rotating massive stars evolved at low-metallicity, objects that are proposed as likely progenitors of long-duration gamma-ray bursts (LGRBs). We perform 1D+rotation stellar-collapse simulations on the progenitor models of Woosley & Heger (2006) and critically assess their potential for the formation of a black hole and a Keplerian disk (namely a collapsar) or a proto-magnetar. We note that theoretical uncertainties in the treatment of magnetic fields and the approximate handling of rotation compromises the accuracy of stellar-evolution models. We find that only the fastest rotating progenitors achieve sufficient compactness for black-hole formation while the bulk of models possess a core density structure typical of garden-variety core-collapse supernova (SN) progenitors evolved without rotation and at solar metallicity. Of the models that do have sufficient compactness for black-hole formation, most of them also retain a large amount of angular momentum in the core, making them prone to a magneto-rotational explosion, therefore preferentially leaving behind a proto-magnetar. A large progenitor angular-momentum budget is often the sole criterion invoked in the community today to assess the suitability for producing a collapsar. This simplification ignores equally important considerations such as the core compactness, which conditions black-hole formation, the core angular momentum, which may foster a magneto-rotational explosion preventing black-hole formation, or the metallicity and the residual envelope mass which must be compatible with inferences from observed LGRB/SNe. Our study suggests that black-hole formation is non trivial, that there is room for accommodating both collapsars and proto-magnetars as LGRB progenitors, although proto-magnetars seem much more easily produced by current stellar-evolutionary models.

10 emulateapj pages, 3 figures, 1 table, matches published version

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Cited by in corpus (7)

• The Landscape of the Neutrino Mechanism of Core-Collapse Supernovae: Neutron Star and Black Hole Mass Functions, Explosion Energies and Nickel Yields
• Binary population synthesis models for core-collapse gamma-ray burst progenitors
• Magnetorotational core collapse of possible GRB progenitors. IV. A wider range of progenitors
• Multiple stellar populations and their evolution in globular clusters: A nucleosynthesis perspective
• Evolution and Nucleosynthesis of Very Massive Stars
• Neutrino Echos following Black Hole Formation in Core-Collapse Supernovae
• A universal scaling law of black hole activity including gamma-ray bursts