Isotropic Long Gamma-Ray Bursts From Unbinding Neutron Stars: The Teranova Model

Long gamma-ray bursts (GRBs), the most luminous explosions in the Universe, are generally explained with the highly anisotropic jetted-collapsar-seen-head-on model. We argue that this model has suffered critical experimental setbacks, in particular: non-periodical light curves, quasi-absence of off-axis collapsars, frequent absence of associated supernovae (SNe), weird exclusivity of type 1c/1b SNe, unexplainable ultra-long GRBs, not to mention severe internal inconsistencies. To overcome these issues, we call for a paradigm change. We suggest modelling long GRBs as isotropic explosions powered by unbinding neutron stars (NSts). We argue that such tremendous explosions (“teranovae”) may occur during collisions between high-velocity (HV) magnetars and blue supergiant stars. Such collisions have indeed much more chances to occur in high-density blue galaxies ‒ where indeed most bursts are observed. A HV-NSt punching into a supergiant enters “Hyper-Eddington mode”, accretes 5-10 M⊙ or more in a short time, reaches extreme temperatures and unbinds within the host star. The detonation blows away the supergiant’s external layers, creating the H&He stripped core necessary for the ensuing 1c-SN. When the core is smashed into pieces, or left behind the optically thick ejecta, we witness a SN-lacking long GRB. We show that this model fits nicely to most observational data.