Jul 12 – 23, 2021
Europe/Berlin timezone

BlaVar: A numerical study of long-term multi-wavelength blazar variability

Jul 15, 2021, 12:00 PM
1h 30m


Talk GAD | Gamma Ray Direct Discussion


Markos Polkas (National and Kapodistrian University of Athens)


Blazars are characterized by flux variability that is frequency-dependent and manifests in a variety of timescales. Decade-long monitoring of blazars at optical and infrared (OIR) wavelengths with the Small and Moderate Aperture Research Telescope System (SMARTS) in Chile and in gamma-rays with the Fermi Large Area Telescope (LAT) has enabled the systematic study of their multi-wavelength long-term variability. These studies pinpoint that besides extreme short-term variability (minutes to hours), a source can exhibit correlated and uncorrelated inter-band flux variability between different observation periods and/or on different timescales (days to years).

In this work, we investigate from a theoretical perspective the long-term variability properties of blazar emission. To do so, we impose variations on the main parameters of the one-zone leptonic model (injection luminosity of relativistic electrons, strength of magnetic field, Doppler factor, and external photon field luminosity) motivated by the Fermi-LAT full-mission light curves of blazars. Using as case studies two bright and well-monitored blazars from the SMARTS sample (PKS2155-304 and 3C273), we compute 10 year-long OIR, X-ray, and gamma-ray model light curves for different varying parameters. We compare the findings of our theoretical investigation with multi-wavelength observations using various measures of variability. While no single-varying parameter simulation can explain all multi-wavelength variability properties, our results motivate future time-dependent studies with coupling between two or more physical parameters to describe the multi-wavelength long-term blazar variability.


AGN: gamma-rays : multiwavelength: variability: radiative-transfer

Subcategory Theoretical Results

Primary author

Markos Polkas (National and Kapodistrian University of Athens)


Maria Petropoulou Petropoulou (Princeton University) Dr Georgios Vasilopoulos (Yale University) Prof. Apostolos Mastichiadis (National and Kapodistrian University of Athens) Prof. Megan Urry (Yale University) Prof. Paolo Coppi (Yale University) Prof. Charles Bailyn (Yale University)

Presentation materials