Blazars are bright from radio wavelengths to gamma-ray energies. Precise modeling of their
multi-wavelength emission allows to constrain their physical properties. However, the
emission of blazars is known to be variable on various timescales. Therefore, for a meaningful
interpretation of these properties, observations need to be at least quasi-simultaneous. Such
observations have been triggered by INTEGRAL on the blazar 3C 279, which exhibited the brightest
flare ever at high energies in June 2015. The analyses of these multifrequency observations (see
data in picture) pose new challenges to the jet physics.
The ~5 billion light-years distant blazar 3C 279 was caught in its brightest flare ever at high
energies by INTEGRAL/IBIS/ISGRI, thanks to its large field of view. The multi-frequency campaign
around this event covers 10 orders of magnitude in energies, involving observations by Fermi/LAT
at gamma-rays, by INTEGRAL/IBIS at hard X-rays, by Swift at X-rays and UV, and by SMARTS in
optical to near-IR wavelengths. This wide coverage allows for a detailed study of the source by
using two complementary radiation transfer models: a so-called leptonic model and a lepto-hadronic
model. These two models, shown in the picture as a gray solid line and as a white dashed line,
respectively, can equally well represent the data. Yet, the derived parameters of these models
challenge the physical conditions in the jet. In fact, for the leptonic model equipartition
between the energy densities cannot be achieved, while the lepto-hadronic model suffers from an
extreme jet power.
Reference:
"3C 279 in Outburst in 2015 June: A Broadband SED Study Based on the INTEGRAL Detection”,
Eugenio Bottacini, Markus Böttcher, Elena Pian & Werner Collmar,
ApJ, 832, 17 (http://adsabs.harvard.edu/abs/2016ApJ...832...17B)
Credits:
Artist's rendering in lower right corner: ESO/M. Kornmesser
