[Okc-wp4] EO meeting tomorrow

[Francesco Taddia]

Dear all,

tomorrow at 13:00 (usual room) 
we will have Damien presenting his paper: http://arxiv.org/abs/1410.2730 <http://arxiv.org/abs/1410.2730>.
Here the abstract:

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Poynting flux dominated jets challenged by their photospheric emission.   D. Bégué and A. Pe'er
One of the key open question in the study of jets in general, and jets in gamma-ray bursts (GRBs) in particular, is the magnetization of the outflow. Here we consider the
photospheric emission of Poynting flux dominated outflows, when the dynamics is mediated by magnetic reconnection. We show that thermal three-particle processes, responsible for
the thermalization of the plasma, become inefficient at a radius r_sup \sim 10^9.5 cm, far below the photosphere, at \sim 10^11.5 cm. Conservation of the total photon number
above r_sup combined with Compton scattering below the photosphere enforces kinetic equilibrium between electrons and photons. This, in turn, leads to an increase in the
observed photon temperature, which reaches >8 MeV (observed energy) when decoupling the plasma at the photosphere. This result is weakly dependent on the free model parameters.
We show that in this case, the expected thermal luminosity is a few \% of the total luminosity, and could therefore be detected. The predicted peak energy is more than an order
of magnitude higher than the observed peak energy of most GRBs, which puts strong constraints on the magnetization of these outflows.
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Francesco Taddia
Postdoctoral Researcher
Department of Astronomy
Stockholm University, Sweden
ftadd at astro.su.se <mailto:ftadd at astro.su.se>







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