Astrophysics and Space Science

, Volume 311, Issue 1–3, pp 185–190 | Cite as

Vertical structure of hyper-accreting disks and consequences for gamma-ray burst outflows

  • Elena M. Rossi
  • Philip J. Armitage
  • Tiziana Di Matteo
Original Article

Abstract

We discuss the physics of the power source for gamma-ray bursts (GRBs). There is a great variety of stellar systems proposed as progenitors of long and short GRBs, but any current model for the engine ultimately involves the formation of a hyper-accreting disk around a newly-formed black hole of a few solar masses. The study of such disks can shed light onto the burst composition and energy content. We present preliminary results from disk vertical structure calculations. These include neutrino transport, a height-dependent determination of the nuclear composition, and a simplified treatment of turbulent mixing. We find that vertical mixing is rapid enough to largely erase compositional gradients, and as a consequence the upper layers of the disk reflect the neutron-rich composition of the midplane close to the black hole. We review the implications of this for the nuclear composition of outflows in GRBs. Our models suggest an increasing role for pairs in the upper regions of the disk, and we speculate that a pair-driven wind could be a significant source of cooling.

Keywords

Accretion, accretion disks Neutrinos Nuclear reactions, nucleosynthesis, abundances Gamma rays: bursts 

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Copyright information

© Springer Science+Business Media B.V. 2007

Authors and Affiliations

  • Elena M. Rossi
    • 1
  • Philip J. Armitage
    • 1
    • 2
  • Tiziana Di Matteo
    • 3
  1. 1.JILAUniversity of ColoradoBoulderUSA
  2. 2.Department of Astrophysical and Planetary SciencesUniversity of ColoradoBoulderUSA
  3. 3.Department of PhysicsCarnegie-Mellon UniversityPittsburghUSA

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