The First Light from Stellar Explosions: Shock Breakout and Early Interaction

A stellar explosion launches a radiation-mediated shock that propagates through the star and breaks out when the optical depth ahead of it becomes too low to sustain the shock. The photons released during shock breakout constitute the first electromagnetic signal from a cosmic explosion and carry unique information about the medium from which the shock emerges, including its geometry, radius, composition, and density profile. Following breakout, if the circumstellar material is sufficiently dense, the interaction continues to generate detectable radiation, providing a probe of mass loss shortly before the explosion.

In this talk, I will discuss the distinctive properties of radiation-mediated shocks and describe the resulting breakout emission and interaction signals in a variety of cosmic explosions. I will highlight some of the things that observations of shock breakout and early interaction have taught us so far, and some of what we expect to learn during the coming decade.

Biography: Prof. Ehud Nakar works on a range of topics in theoretical and numerical high energy astrophysics and in particular the physical processes that are active in sources of high energy radiation, cosmic-rays, neutrinos and gravitational waves. Among the astrophysical phenomena that are being explored are neutron-star mergers, gamma-ray bursts, supernovae and soft gamma-repeaters. Physical processes that are studied include collisionless and radiation-mediated shocks, shock breakouts, particle acceleration, relativistic hydrodynamics and radiative transfer. The study combines high-performance computing numerical simulations and analytic work. (From University website)