Dense Optical and Near-Infrared Monitoring of Cta 102 During High State in 2012 With Oister: Detection of Intra-Night “Orphan Polarized Flux Flare”

Itoh, R.; Fukazawa, Yasushi; Tanaka, Yasuyuki; Abe, Yoshitaka; Akitaya, Hiroshi; Arai, Akira; Hayashi, Masahiko; Hori, T.; Isogai, M.; Izumiura, Hideyuki; Kawabata, Koji S.; Kawai, N.; Kuroda, D.; Miyanoshita, Ryo; Moritani, Yuki; Morokuma, Tomoki; Nagayama, Takahiro; Nakamoto, Jumpei; Nakata, Chikako; Oasa, Yumiko; Ohshima, Tomohito; Ohsugi, T.; Okumura, Shin-ichiro; Saito, Yoshihiko; Yu, Shenghua; Sasada, Mahito; Sekiguchi, K.; Takagi, Y.; Takahashi, Jun; Takahashi, Yukihiro; Takaki, K.; Uemura, Makoto; Ueno, Issei; Urakawa, Seitaro; Watanabe, Makoto; Yamanaka, Masahito; Yonekura, Yoshinori; Yoshida, Michitoshi

doi:10.1088/2041-8205/768/2/l24

Cited by 18 publications

(15 citation statements)

References 30 publications

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“…However, in such a scenario, a correlation between the flux and PD changes are expected, because of a compression of the jet plasma with initially tangled (by assumption) jet magnetic field at the shock front. Several observations for individual blazars on a night-to-night basis presented in the literature conforms to this model, possibly with some minor modifications or additions (e.g., Hagen-Thorn et al 2008;Itoh et al 2013;Covino et al 2015;Bhatta et al 2016).…”

Section: Discussionsupporting

confidence: 59%

“…A highly polarized (PD∼50%) microflare was observed for the blazar S5 0716+714 during the Whole Earth Blazar Telescope campaign carried out in 2014 (Bhatta et al 2015). An orphan flare in polarized flux density was observed for the blazar CTA 102 (Itoh et al 2013). Intense variability in total flux density, polarized flux density, and χ was noted for BL Lacertae while the blazar PKS 1424+240 remained steady during the study by Covino et al (2015).…”

Section: Introductionmentioning

confidence: 89%

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Multiband optical flux density and polarization microvariability study of optically bright blazars

Pasierb

Goyal

Ostrowski

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We present the results of flux density, spectral index, and polarization intra-night monitoring studies of a sample of eight optically bright blazars, carried out by employing several small to moderate aperture (0.4 m to 1.5 m diameter) telescopes fitted with CCDs and polarimeters located in Europe, India, and Japan. The duty cycle of flux variability for the targets is found to be ∼ 45 percent, similar to that reported in earlier studies. The computed two-point spectral indices are found to be between 0.65 to 1.87 for our sample, comprised of low-and intermediate frequency peaked blazars, with one exception; they are also found to be statistically variable for about half the instances where 'confirmed' variability is detected in flux density. In the analysis of the spectral evolution of the targets on hourly timescale, a counter-clockwise loop (soft-lagging) is noted in the flux-spectral index plane on two occasions, and in one case a clear spectral flattening with the decreasing flux is observed. In our data set, we also observe a variety of flux-polarization degree variability patterns, including instances with a relatively straightforward anti-correlation, correlation, or counterclockwise looping. These changes are typically reflected in the flux-polarization angle plane: the anti-correlation between the flux and polarization degree is accompanied by an anti-correlation between the polarization angle and flux, while the counterclockwise flux-PD looping behaviour is accompanied by a clockwise looping in the flux-polarization angle representation. We discuss our findings in the framework of the internal shock scenario for blazar sources.

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Section: Discussionsupporting

confidence: 59%

Section: Introductionmentioning

confidence: 89%

Multiband optical flux density and polarization microvariability study of optically bright blazars

Pasierb

Goyal

Ostrowski

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…We use polarimetric data collected at St. Petersburg University (Crimea and St. Petersburg), Lowell (Perkins), Steward, and Calar Alto observatories, supplementing these with data from the Kanata telescope (Itoh et al 2013). Instrumental polarization was derived from measurements of stars located near the object under the assumption that their radiation is intrinsically unpolarized.…”

Section: Optical Polarimetrymentioning

confidence: 99%

Exceptional outburst of the blazar CTA 102 in 2012: the GASP–WEBT campaign and its extension

Larionov

Villata

Raiteri

et al. 2016

Mon. Not. R. Astron. Soc.

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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.

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“…Statistical analyses of the flux variations -in particular, the power-law power spectra (Chatterjee et al 2008(Chatterjee et al , 2009(Chatterjee et al , 2012Abdo et al 2011) -imply that the variations are governed by noise processes with higher amplitudes on longer time-scales. Furthermore, the linear polarization of blazars ranges from a few to tens of percent and tends to be highly variable in both degree and position angle (e.g., D'Arcangelo et al 2007;Marscher et al 2010;Itoh et al 2013). Although the range of degree of polarization and the tendency for the position angle to be similar to or nearly transverse to the jet axis (e.g., Jorstad et al 2007) can be explained with a helical magnetic field (Lyutikov et al 2005;Pushkarev et al 2005), the rapid variations in polarization are not naturally reproduced in a model in which the field is either 100% globally ordered or completely chaotic on small scales.…”

Section: Introductionmentioning

confidence: 99%

Turbulent, Extreme Multi-Zone Model for Simulating Flux and Polarization Variability in Blazars

Marscher

2013

ApJ

486

513

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The author presents a model for variability of the flux and polarization of blazars in which turbulent plasma flowing at a relativistic speed down a jet crosses a standing conical shock. The shock compresses the plasma and accelerates electrons to energies up to γ max 10 4 times their rest-mass energy, with the value of γ max determined by the direction of the magnetic field relative to the shock front. The turbulence is approximated in a computer code as many cells, each with a uniform magnetic field whose direction is selected randomly. The density of high-energy electrons in the plasma changes randomly with time in a manner consistent with the power spectral density of flux variations derived from observations of blazars. The variations in flux and polarization are therefore caused by continuous noise processes rather than by singular events such as explosive injection of energy at the base of the jet. Sample simulations illustrate the behavior of flux and linear polarization versus time that such a model produces. The variations in γ-ray flux generated by the code are often, but not always, correlated with those at lower frequencies, and many of the flares are sharply peaked. The mean degree of polarization of synchrotron radiation is higher and its time-scale of variability shorter toward higher frequencies, while the polarization electric vector sometimes randomly executes apparent rotations. The slope of the spectral energy distribution exhibits sharper breaks than can arise solely from energy losses. All of these results correspond to properties observed in blazars.

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Dense Optical and Near-Infrared Monitoring of Cta 102 During High State in 2012 With Oister: Detection of Intra-Night “Orphan Polarized Flux Flare”

Cited by 18 publications

References 30 publications

Multiband optical flux density and polarization microvariability study of optically bright blazars

Multiband optical flux density and polarization microvariability study of optically bright blazars

Exceptional outburst of the blazar CTA 102 in 2012: the GASP–WEBT campaign and its extension

Turbulent, Extreme Multi-Zone Model for Simulating Flux and Polarization Variability in Blazars

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