Gamma ray bursts – neutrino cooled accretion flow

We model the structure and evolution of the torus accreting onto Kerr black hole in the central engine of a gamma ray burst.

The movie below (left) shows the ratio of the gas to magnetic pressure (color scale) in the plasma. White lines mark the magnetic field configuration.  The parameters of the system, such as the black hole mass and mass of the accreting matter, determine the physical conditions there  (the density and temperature of the gas). The poloidal structure of the magnetic field, adopted initially, evolves in time during our computations.. The toroidal field component emerges, and the open magnetic field lines form in a narrow region close to the poles of a rotating black hole. Its rotational energy can be extracted from such an engine via the magnetic field, and is transferred to the poloidal jets. These streams of a rarefied, magnetized plasma, are ejected along the rotation axis. At some distance, the kinetic energy of a jet  acquires the velocity close to the speed of light. The kinetic energy is dissipated and converted to the electromagnetic radiation – gamma rays.

Movie on the right, shows the evolution of the neutrino emissivity in the plasma accreting onto black hole in the GRB central engine.  Because the matter is extremely dense and hot, the nuclear reactions are ignited there, such as the electron-positron capture on nucleons, or electron positron pair annihilation. These reactions lead to the formation of neutrino-antineutrino pairs. The power of emitted radiation exceeds by many orders of magnitude the photon luminosity of the source, as the plasma is very opaque and photons are completely trapped. The neutrinos transport the energy dissipated in the accreting matter.  (Simulations with the code HARM-2D, supplemented with the microphysics and nuclear equation of state of dense matter. Author: Agnieszka Janiuk).


by with no comments yet.

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>