Astronomy and Astrophysics – Astronomy
Scientific paper
Oct 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aipc.1279..430t&link_type=abstract
DECIPHERING THE ANCIENT UNIVERSE WITH GAMMA-RAY BURSTS. AIP Conference Proceedings, Volume 1279, pp. 430-432 (2010).
Astronomy and Astrophysics
Astronomy
Gamma-Ray Sources (Astronomical), Accretion Disks, Magnetohydrodynamics, Gamma-Ray Sources, Gamma-Ray Bursts, Infall, Accretion, And Accretion Disks, Magnetohydrodynamics And Plasmas
Scientific paper
We develop a numerical scheme and code for estimating the energy and momentum transfer via neutrino pair annihilation, bearing in mind the application to the collapsar models of gamma-ray bursts (GRBs). To calculate the neutrino flux illuminated from the accretion disk, we perform a ray-tracing calculation in the framework of special relativity. Using hydrodynamical data in our collapsar simulation, we estimate the annihilation rates in a post-processing manner. We show that the neutrino energy deposition and momentum transfers are strongest near the inner edge of the accretion disk. The beaming effects of special relativity are found to change the annihilation rates by several factors in the polar funnel region. After the accretion disk settles into a stationary state (typically later than 9 s from the onset of gravitational collapse), we find that the neutrino-heating timescale in the vicinity of the polar funnel (~80 km) can become shorter than the hydrodynamical timescale, indicating that the neutrino-heated outflows can be launched there. We point out that the momentum transfer can play an important role as the energy deposition for the efficient acceleration of neutrino-driven outflows. Our results suggest that the neutrino pair annihilation has a potential importance equal to the conventional magnetohydrodynamic mechanism for igniting the GRB fireballs.
Harikae Seiji
Kotake Kei
Takiwaki Tomoya
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