Astronomy & Astrophysics Seminar: Afterglow linear polarization signatures from shallow GRB jets

Zoom: https://tau-ac-il.zoom.us/j/87230679135?pwd=Y1duRlArUkJwSnhaaXVscUU0azY3Zz09

Abstract:

When gamma-ray bursts (GRBs) occur inside thick ejecta or deep within a star, the newly created jet must drill its way out of the confining medium to break out of it. During its advancement, the jet will develop a structure that encodes the processes it has undergone while propagating, which we have no way of measuring. Recent theoretical, simulation-based, studies have shown that GRB jets erupting from a star possess substantial energy in their mildly relativistic wings and that structures differ depending on the media the jet broke out from. Therefore, gaining insight into the jet structure offers valuable information about its pre-breakout experiences.

In this talk, I propose probing the jet structure by modeling the observable quantities of the afterglow and focusing on the imprint it leaves on the linear polarization signal of the system. The temporal evolution of the polarization signature is highly sensitive to the emission region geometry, and when modelled carefully with analytical and numerical methods, can give robust observational features of jets with varying structures. The numerical model is then applied to suggested structures for the jet of GRB 221009A and the resulting polarization curves are compared to the upper limits placed on the afterglow.
 

Seminar Organizer: Dr. Jonathan Stern