Speaker
Description
Blazars, a subclass of active galactic nuclei with relativistic jets aligned close to the line of sight, exhibit strong, rapidly variable emission across the electromagnetic spectrum due to Doppler boosting. Their double-peaked spectral energy distributions (SEDs) are attributed to synchrotron emission at lower frequencies and inverse Compton scattering at higher frequencies, providing key insights into particle acceleration, jet dynamics, and accretion physics around supermassive black holes. Despite decades of study, fundamental questions remain about the composition of the relativistic plasma, jet acceleration mechanisms, and the validity of the blazar sequence, motivating deeper analysis of stochastic variability properties.We characterise long-term optical flux variations in a sample of ten well-observed blazars using light curves spanning up to 130 years.
We focus on temporal variability in the optical band, performing power spectral density (PSD) analysis to search for breaks from red noise to white noise at low frequencies. Using artificial light curves generated via the Timmer–König and Emmanoulopoulos methods, we test and compare three descriptive models: simple power-law noise, broken power-law PSDs, and the Ornstein–Uhlenbeck (OU) process, which naturally produces low‑frequency flattening.
We will relate our findings on PSD slope and break frequency with other observables, notably the accretion disk luminosity and the Doppler factors of the jets.