Flare-less long Gamma-ray Bursts and the properties of their massive star progenitors

Abstract

While there is mounting evidence that long Gamma-Ray Bursts (GRBs) are associated with the collapse of massive stars, the detailed structure of their pre-supernova stage is still debatable. Particularly uncertain is the degree of mixing among shells of different composition, and hence the role of magnetic torques and convection in transporting angular momentum. Here we show that early-time afterglow observations with the Swift satellite place constraints on the allowed GRB pre-supernova models. In particular, they argue against pre-supernova models in which different elemental shells are unmixed. These types of models would produce energy injections into the GRB engine on timescales between several hundreds of seconds to a few hours. Flaring activity has {\em not} been observed in a large fraction of well-monitored long GRBs. Therefore, if the progenitors of long GRBs have common properties, then the lack of flares indicates that the massive stars which produce GRBs are mostly well mixed, as expected in low-metallicity, rapidly rotating massive stars.

Accepted to ApJLetters

References in corpus (11)

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Cited by in corpus (9)

• Can Gamma-Ray Burst Jets Break Out the First Stars?
• The fate of fallback matter around newly born compact objects
• No flares from Gamma-Ray Burst afterglow blast waves encountering sudden circumburst density change
• Critical angular momentum distributions in collapsars: quiescent periods from accretion state transitions in long gamma-ray bursts
• Supernovae Powered by Collapsar Accretion in Gamma-Ray Burst Sources
• Simulations of Accretion Powered Supernovae in the Progenitors of Gamma Ray Bursts
• Characterizing the time variability in magnetized neutrino--cooled accretion disks: signatures of the gamma-ray burst central engine
• The influence of fallback discs on the spectral and timing properties of neutron stars
• Inner Engine Shutdown from Transitions in the Angular Momentum Distribution in Collapsars