Gamma-ray burst afterglows from jet simulation to light curve

Gamma-ray bursts (GRB) are brief intense flashes of gamma-rays that are produced when a relativistic jet is launched after the collapse of a massive star or after a neutron star-neutron star merger or neutron star-black hole merger. As the relativistic jet slows down in the circumburst environment, non-thermal afterglow radiation is emitted at progressively longer wavelengths, from X-rays all the way down to radio. Although this broad picture is analytically reasonably well understood, many questions remain that require a detailed numerical approach to both jet dynamics and synchrotron radiation production within a relativistically evolving jet. In this presentation I will describe how we combine a synchrotron linear radiative transfer code with large scale parallel numerical jet simulations in order to answer specific questions about GRB afterglows. Examples of such questions are: How does late time activity at the source ('engine') lead to variability in the observed light curve (and what is the role of synchrotron self-absorption)? and What will the afterglow image look like if we could spatially resolve it (and the observer is not positioned exactly on the jet axis)?