Active galactic nuclei (AGN) are supermassive black holes at the centers of galaxies that are accreting material. These AGN emit jets of charged particles that move at speeds close to that of light, transporting huge amounts of energy away from the central black hole region and radiating across the electromagnetic spectrum. Blazars are extreme examples of AGN in which the collimated jets are coincidentally aligned towards us. Blazar jets have two peak emission wavelengths, one that spans the range from the radio to the X-ray, the result of charged particle acceleration, and one at extremely short wavelength, high energy gamma ray bands usually (and somewhat controversially) attributed to the charged particles scattering infrared “seed” photons from a variety of other sources. All these bands manifest strong and unpredictable variability. Simultaneous, long-term observations across multiple bands therefore, by modeling the relative timing of flares and other variable emission, offer a valuable way to investigate the numerous possible physical mechanisms at work.
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Source: Phys.org