Flaring and Time-Dependent Modeling of Blazars

• Applicant: Professor Dr. Stefan Wagner
• Subject Area: Astrophysics and Astronomy
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 443220636

One of the key characteristics of blazars is their strongly variable emission. Their flux varies by up to orders of magnitude throughout the entire electromagnetic spectrum and down to time scales of minutes. The Gamma-ray band is of particular interest as it often dominates the total energy output of blazars. Features imprinted in the light curves are likely related to changes in the underlying particle distributions and allow us to probe different physical mechanisms. In this project, we will study multiwavelength (MWL) variability properties of blazars with a focus on the Gamma-ray band and the connection to radio frequencies. We will explore the constraints on the phenomenological models of acceleration and substructure in blazars. The analysis and interpretation of Blazar short-term variability opens an unlimited discovery space challenging our theoretical understanding of the black-hole-jet phenomenon. We specifically address the precision diagnosis of the fastest gamma-ray variability observed across a wide energy band up to very high energies (VHE, > 100 GeV) and the response of millimeter-band emission (characteristic for the parsec-scale jet base) in collaboration with Project 10 to test models of jet substructures and radiation mechanisms by applying novel methods. The constraints derived from the data are further explored with a time-dependent one-zone radiation code. We will study the specific requirements of the particle distributions to fulfill the MWL behavior from the data. Explicit modeling of the observed flares will test existing models of particle acceleration and source parameter evolutions, exploiting techniques developed by us. In collaboration with Project 10, we will also study the Doppler factor inconsistency, where fast MWL variability usually requires high Doppler factors, whereas radio observations suggest much lower ones. We will test the influence of geometrical effects, which may explain this inconsistency.

• DFG Programme: Research Units
• Subproject of: FOR 5195: Relativistic Jets in Active Galaxies
• Co-Investigators: Professor Dr. Matthias Kadler; Dr. Michael Zacharias