8/26 Lunch Talk: Dr. Markus Böttcher: Polarization in relativistic jets

in Seminars
August 25th, 2014



Polarization as a diagnostic of the emission processes in relativistic jets

Dr. Markus Böttcher
North-West University, Potchefstroom, South Africa

CAS 500
12:00 pm
August 26, 2014

Astrophysical sources exhibiting relativistic jets, such as active galactic nuclei (AGN) and gamma-ray bursts (GRBs) are strong emitters of radiation across the electromagnetic spectrum, from radio to gamma-rays. In spite of intensive, co-ordinated observing efforts over the past several decades, the nature of the radiating particles, the location of the gamma-ray emissino region, and the mechanism leading to the emission of high-energy radiation, are still uncertain. As a new strategy to break the degeneracy of different models proposed for the origin of gamma-rays from relativistic jets, many observatories are now including measurements of optical polarization into multi-wavelength studies of relativistic jet sources, and a new generation of X-ray polarimeters is currently being developed. These studies have, in several instances, revealed large rotations of the position angle of the optical polarization, correlated with gamma-ray flaring activity in blazars, a highly beamed class of jet-dominated AGN. In this talk, I will summarize recent theoretical predictions of the high-energy (X-ray and gamma-ray) polarization from different blazar models, discuss the implications of high-energy polarization on gamma-gamma absorption of high-energy gamma-rays within the emission region, and present a new theoretical interpretation of the optical polarization-angle swings associated with gamma-ray flares in blazars.