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Exploring Ultra-Relativistic Outflows

Objective

Relativistic outflows appear in a wide variety of astrophysical sources, from Galactic micro-quasars to cosmological gamma-ray bursts (GRBs) and active galactic nuclei (AGN). In most cases the relativistic outflow is thought to arise from accretion onto a black hole, while neutron-stars are also known to produce relativistic outflows (either in the form of a steady wind or an impulsive ejection of plasmoids). Such relativistic outflow sources are thought to accelerate the highest energy cosmic rays, and are expected to be important sources of high-energy neutrinos and gravitational waves for upcoming detectors. Furthermore, they can probe strong field gravity, large densities and magnetic fields, and may have a strong effect on their environment. Thus, a good understanding of their physics can have many important implications. I plan to study several different aspects of ultra-relativistic outflows, which may help shed light on their underlying physics: (i) the acceleration of an impulsive highly-magnetized relativistic outflow, its interaction with the external medium, as well as the energy dissipation and emission mechanism within the outflow. These have been investigated so far mainly in quasi-steady state long-lived sources, and the differences for impulsive short-lived outflows is of great importance, and particularly relevant for GRBs; (ii) time dependent opacity effects in impulsive relativistic sources – they lead to different observed properties compared to quasi-steady state sources, and probes the emission site and the Lorentz factor of the outflow, and thus its composition (which is very poorly constrained); this is relevant to the prompt gamma-ray emission in GRBs, as well as to flares in Blazars, micro-quasars and GRBs; (iii) The stability properties of relativistic shocks – these develop is relativistic outflow sources and may effect their observed properties, but have not been investigated in much detail so far, as their Newtonian counterparts.

Call for proposal

FP7-PEOPLE-2007-4-3-IRG
See other projects for this call

Coordinator

THE UNIVERSITY OF HERTFORDSHIRE HIGHER EDUCATION CORPORATION
Address
College Lane
AL10 9AB Hatfield
United Kingdom
Activity type
Higher or Secondary Education Establishments
EU contribution
€ 100 000
Administrative Contact
James Hough (Prof.)