Modeling the Multiwavelength Linear Polarization in GRB Afterglows

  Gal Birenbaum  
Tel Aviv University

Following the gamma-ray prompt emission of a Gamma-Ray Burst (GRB), a multiwavelength afterglow arises. The afterglow emission has been well modelled by a decelerating relativistic blast wave plunging into the ambient medium and accelerating particles in it, which emit Synchrotron radiation. A linear polarization degree of a few percent has been measured in some GRB afterglows in the optical band, and recently a sub-percent detection was also made in the radio. These measurements can offer a wealth of information regarding the afterglow geometry and the critical GRB parameters (explosion energy, the fraction of energy converted into shock magnetic field, etc.), which we must decipher correctly. We model the time evolution of the afterglow emission numerically, map it on the plane of the sky and calculate the observed polarization signature. We account for relativistic effects as well as how the Synchrotron spectrum changes in time. In this talk I will present our model and demonstrate its ability to generate multiwavelength polarization curves.