Details

Autor(en) / Beteiligte

• Raiteri, C M
• Villata, M
• Carnerero, M I
• Savchenko, S S
• Kurtanidze, S O
• Vlasyuk, V V
• Marchini, A
• Matsumoto, K
• Lorey, C
• Joner, M D
• Gazeas, K
• Carosati, D
• Mirzaqulov, D O
• Acosta Pulido, J A
• Agudo, I
• Bachev, R
• Benítez, E
• Borman, G A
• Calcidese, P
• Chen, W P
• Damljanovic, G
• Ehgamberdiev, S A
• Elsässer, D
• Feige, M
• Frasca, A
• Gaur, H
• Grishina, T S
• Gupta, A C
• Hiriart, D
• Holland, M
• Horst, B
• Ibryamov, S
• Ivanidze, R Z
• Jensen, J
• Jithesh, V
• Jovanovic, M D
• Kiehlmann, S
• Kimeridze, G N
• Kishore, S
• Kopatskaya, E N
• Kurtanidze, O M
• Larionova, E G
• Lin, H C
• Mannheim, K
• Marinelli, C
• Moreira Reyes, J
• Morozova, D A
• Nikolashvili, M G
• Reinhart, D
• Romanov, F D
• Semkov, E
• Seufert, J
• Shishkina, E V
• Sigua, L A
• Skalidis, R
• Spiridonova, O I
• Stojanovic, M
• Strigachev, A
• Troitskaya, Y V
• Troitskiy, I S
• Tsai, A
• Vasilyev, A A
• Vince, O
• Vrontaki, K
• Wani, K
• Watts, D
• Zhovtan, A V

Titel

Extreme photometric and polarimetric variability of blazar S4 0954+65 at its maximum optical and γ-ray brightness levels

Ist Teil von

• Monthly notices of the Royal Astronomical Society, 2023-10, Vol.526 (3), p.4502-4513

Ort / Verlag

Oxford University Press

Erscheinungsjahr

2023

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• ABSTRACT In 2022 the BL Lac object S4 0954+65 underwent a major variability phase, reaching its historical maximum brightness in the optical and γ-ray bands. We present optical photometric and polarimetric data acquired by the Whole Earth Blazar Telescope (WEBT) Collaboration from 2022 April 6 to July 6. Many episodes of unprecedented fast variability were detected, implying an upper limit to the size of the emitting region as low as $10^{-4}$ parsec. The WEBT data show rapid variability in both the degree and angle of polarization. We analyse different models to explain the polarization behaviour in the framework of a twisting jet model, which assumes that the long-term trend of the flux is produced by variations in the emitting region viewing angle. All the models can reproduce the average trend of the polarization degree, and can account for its general anticorrelation with the flux, but the dispersion of the data requires the presence of intrinsic mechanisms, such as turbulence, shocks, or magnetic reconnection. The WEBT optical data are compared to γ-ray data from the Fermi satellite. These are analysed with both fixed and adaptive binning procedures. We show that the strong correlation between optical and γ-ray data without measurable delay assumes different slopes in faint and high brightness states, and this is compatible with a scenario where in faint states we mainly see the imprint of the geometrical effects, while in bright states the synchrotron self-Compton process dominates.