Astronomy & Astrophysics Seminar: Numerical Simulations of Photospheric Emission in Gamma-ray Bursts

Abstract:

Long duration gamma-ray bursts (GRBs), the brightest events in the Universe, are believed to originate in an ultra-relativistic jet breaking out from a massive stellar envelope. Despite decades of study, there is still no consensus on their emission mechanism. One unresolved question is the origin of the tight correlation between the spectral peak energy Ep and peak luminosity Lp discovered in observations. This “Yonetoku relation” is the tightest correlation found in the properties of the prompt phase of GRB emission, providing the best diagnostic for the radiation mechanism.

In this study, we explore this issue by performing present 3D hydrodynamical simulations, and post-process radiation transfer calculations, of photospheric emission from a relativistic jet. Our simulations reproduce the Yonetoku relation as a natural consequence of viewing angle. It is shown that, although jet dynamics depend sensitively on the jet power, the Ep-Lp correlation holds regardless. This result strongly suggests that photospheric emission is the dominant component in the prompt phase of GRBs. In this talk, I will also mention about the other observed correlation found in GRBs and the expected polarization in the emission.

Seminar Organizer: Dr. Omer Bromberg