Modelling of the broad band emission of the AGN PG 1553+113
School
Università degli Studi di Padova
External url: https://thesis.unipd.it/handle/20.500.12608/51840
Abstract:
The BL Lac PG 1553+113 is known for its high variability and exhibits periodic behavior with a 2.2-year cycle, showing a significant 3-sigma significance in its Fermi gamma emission. This periodicity is characterized by a simultaneous flaring state at all energy levels. This thesis focuses on reporting the 2019 flare of PG 1553+113, analyzing multiwavelength data, and modeling the emission from this source. Methods. Data from multiple instruments, ranging from radio to gamma-rays, were analyzed with a specific emphasis on the highest energies, such as the MAGIC telescopes. Subsequently, the emission of PG 1553+113 was divided into a flaring state (April 2019) and enhanced state (June-August 2019) and then modeled using the agnpy software. Results and findings. During this project, multiple models were applied to analyze this source. Initially, a one-zone Synchrotron-Self Compton (SSC) model was utilized; however, evidence from correlation studies and the emission shape suggested a preference for a two-zone SSC model. The new model exhibits a good agreement with the dataset, and its application to PG 1553+113 represents a novel contribution in this work. The project's results reveal a discrepancy between the two states, which can be attributed to variations in the electron number density and magnetic field of the respective zones.