Long-duration, spectrally soft gamma-ray bursts (GRBs) are associated with Type Ic core collapse (CC) supernovae (SNe), and thus arise from the death ofmassive stars. In the collapsar model, the jet launched by the central engine must bore its way out of the progenitor star before it can produce a GRB. Most of these jets do not break out, and are instead 'choked' inside the star, as the central engine activity time, te, is not long enough. Modelling the long-soft GRB duration distribution assuming a power-law distribution for their central engine activity times, ∝t e -α for te > tb, we find a steep distribution (α ~ 4) and a typical GRB jet breakout time of tb ~ 60s in the star's frame. The latter suggests the presence of a low-density, extended envelope surrounding the progenitor star, similar to that previously inferred for low-luminosity GRBs. Extrapolating the range of validity of this power law below what is directly observable, to te < tb, by only a factor of ~4-5 produces enough events to account for all Type Ib/c SNe. Such extrapolation is necessary to avoid fine-tuning the distribution of central engine activity times with the breakout time, which are presumably unrelated. We speculate that central engines launching relativistic jets may operate in all Type Ib/c SNe. In this case, the existence of a common central engine would imply that (i) the jet may significantly contribute to the energy of the SN; (ii) various observational signatures, like the asphericity of the explosion, could be directly related to jet's interaction with the star.
Bibliographical noteFunding Information:
ES is grateful to Yuri Lyubarsky for insightful discussions. The authors also thank Dovi Poznanski and John Magorrian for useful comments. ES and JGacknowledge support from the Israeli Science Foundation under Grant No. 719/14. OB is thankful for the support of the I-Core center of excellence of the CHE-ISF. MCS acknowledges support from the Deutsche Forschungsgemeinschaft in the Collaborative Research Center (SFB 881) 'TheMilkyWay System' (subprojects B1, B2 and B8) and in the Priority Program SPP 1573 'Physics of the InterstellarMedium' (grant numbers KL 1358/18.1, KL 1358/19.2). MCS furthermore thanks the European Research Council for funding in the ERC Advanced Grant STARLIGHT (project number 339177).
© 2018 The Author(s).
- Gamma-ray burst: general
- Supernovae: general