The optical polarization variability of the blazar PKS 2155 304
type: CreativeWork
description: Blazars are some of the most energetic and variable objects in the universe. Blazar emission has been detected across the electromagnetic spectrum and exhibits variability on a wide range of timescales, from minutes to years. The observed emission is Doppler boosted and dominated by non-thermal radiation driven by the magnetic field of a relativistic jet. PKS 2155–304 is an archetypal blazar, located in the southern hemisphere. The source is bright and highly variable, displaying both active and quiescent states. In this thesis I make use of optical polarization and multiwavelength observations across roughly 5.5 years to probe the source variability on short (intra-day to daily), intermediate (days to months) and long timescales (months to years). The polarization, as a direct observable of the jet's magnetic field, can help gain insight into the physical processes that underlie the observed emission, while contemporaneous multiwavelength observations can assist in distinguishing between dierent emission models. I investigated the short term variability of PKS 2155–304 by using optical polarization measurements recorded over a 3 day period during a period of enhanced gamma-ray activity. The observations revealed, for the first time, evidence of quasiperiodic oscillations in the optical polarization of a blazar. A periodogram analysis of the polarized flux revealed the existence of two periodic components at ≥ 13 minutes and ≥ 30 minutes. The oscillations can be explained by turbulence behind a relativistic shock traversing a jet containing quasi-helical structures in magnetic field or electron density. To study the intermediate timescale brightness variations of the source I analysed its optical polarization and BVRJ multiband light curves during a prominent optical flare in 2010. The flare evolved over roughly 4 months with a flux doubling time of ≥ 11 days. A comparison of the polarization angle and photometric flux revealed the existence of two distinct states a…
abstract: Blazars are some of the most energetic and variable objects in the universe. Blazar emission has been detected across the electromagnetic spectrum and exhibits variability on a wide range of timescales, from minutes to years. The observed emission is Doppler boosted and dominated by non-thermal radiation driven by the magnetic field of a relativistic jet. PKS 2155–304 is an archetypal blazar, located in the southern hemisphere. The source is bright and highly variable, displaying both active and quiescent states. In this thesis I make use of optical polarization and multiwavelength observations across roughly 5.5 years to probe the source variability on short (intra-day to daily), intermediate (days to months) and long timescales (months to years). The polarization, as a direct observable of the jet's magnetic field, can help gain insight into the physical processes that underlie the observed emission, while contemporaneous multiwavelength observations can assist in distinguishing between dierent emission models. I investigated the short term variability of PKS 2155–304 by using optical polarization measurements recorded over a 3 day period during a period of enhanced gamma-ray activity. The observations revealed, for the first time, evidence of quasiperiodic oscillations in the optical polarization of a blazar. A periodogram analysis of the polarized flux revealed the existence of two periodic components at ≥ 13 minutes and ≥ 30 minutes. The oscillations can be explained by turbulence behind a relativistic shock traversing a jet containing quasi-helical structures in magnetic field or electron density. To study the intermediate timescale brightness variations of the source I analysed its optical polarization and BVRJ multiband light curves during a prominent optical flare in 2010. The flare evolved over roughly 4 months with a flux doubling time of ≥ 11 days. A comparison of the polarization angle and photometric flux revealed the existence of two distinct states a…
author: Peceur, Nicolette
keywords: Astronomy
date published: 2024
date modified: 2026-07-22T22:23:39Z
provider: University of Cape Town
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Department of Astronomy

PropertyValue
property ID: Handle
value: http://hdl.handle.net/11427/40361