Bibcode
Larionov, V. M.; Villata, M.; Raiteri, C. M.; Jorstad, S. G.; Marscher, A. P.; Agudo, I.; Smith, P. S.; Acosta-Pulido, J. A.; Arévalo, M. J.; Arkharov, A. A.; Bachev, R.; Blinov, D. A.; Borisov, G.; Borman, G. A.; Bozhilov, V.; Bueno, A.; Carnerero, M. I.; Carosati, D.; Casadio, C.; Chen, W. P.; Clemens, D. P.; Di Paola, A.; Ehgamberdiev, Sh. A.; Gómez, J. L.; González-Morales, P. A.; Griñón-Marín, A.; Grishina, T. S.; Hagen-Thorn, V. A.; Ibryamov, S.; Itoh, R.; Joshi, M.; Kopatskaya, E. N.; Koptelova, E.; Lázaro, C.; Larionova, E. G.; Larionova, L. V.; Manilla-Robles, A.; Metodieva, Y.; Milanova, Yu. V.; Mirzaqulov, D. O.; Molina, S. N.; Morozova, D. A.; Nazarov, S. V.; Ovcharov, E.; Peneva, S.; Ros, J. A.; Sadun, A. C.; Savchenko, S. S.; Semkov, E.; Sergeev, S. G.; Strigachev, A.; Troitskaya, Yu. V.; Troitsky, I. S.
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 461, Issue 3, p.3047-3056
Advertised on:
9
2016
Citations
50
Refereed citations
46
Description
After several years of quiescence, the blazar CTA 102 underwent an
exceptional outburst in 2012 September-October. The flare was tracked
from γ-ray to near-infrared (NIR) frequencies, including Fermi and
Swift data as well as photometric and polarimetric data from several
observatories. An intensive Glast-Agile support programme of the Whole
Earth Blazar Telescope (GASP-WEBT) collaboration campaign in optical and
NIR bands, with an addition of previously unpublished archival data and
extension through fall 2015, allows comparison of this outburst with the
previous activity period of this blazar in 2004-2005. We find remarkable
similarity between the optical and γ-ray behaviour of CTA 102
during the outburst, with a time lag between the two light curves of
≈1 h, indicative of cospatiality of the optical and γ-ray
emission regions. The relation between the γ-ray and optical
fluxes is consistent with the synchrotron self-Compton (SSC) mechanism,
with a quadratic dependence of the SSC γ-ray flux on the
synchrotron optical flux evident in the post-outburst stage. However,
the γ-ray/optical relationship is linear during the outburst; we
attribute this to changes in the Doppler factor. A strong
harder-when-brighter spectral dependence is seen both the in γ-ray
and optical non-thermal emission. This hardening can be explained by
convexity of the UV-NIR spectrum that moves to higher frequencies owing
to an increased Doppler shift as the viewing angle decreases during the
outburst stage. The overall pattern of Stokes parameter variations
agrees with a model of a radiating blob or shock wave that moves along a
helical path down the jet.