Temporal and spectral study of PKS B1222 + 216 flares in 2014

Chatterjee, A.; Roy, Abhradeep; Sarkar, Arkadipta; Chitnis, V. R.

doi:10.1093/mnras/stab2747

Cited by 3 publications

(2 citation statements)

References 44 publications

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“…The observed results points to a scenario where the blazar output is dominated by the inverse Compton scattering of the external radiation, and the jet dissipation occurs at a distance of a few hundreds of Schwarzschild radius from the central black hole, as supported by the canonical jet model (Ghisellini & Tavecchio 2009;Sikora et al 2009). Our result suggests that the γ-ray emitting region lies in the BLR/torus regions in the FSRQ PKS 1222+216, in agreement with former studies on the source during its active and quiescent states (e.g., Tavecchio et al 2011;Ackermann et al 2014;Chatterjee et al 2021). This is also consistent with some recent studies of other FSRQs (e.g., Paliya 2015;Shukla & Mannheim 2020).…”

Section: Summary and Discussionsupporting

confidence: 90%

Long-term Optical and γ-Ray Variability of the Blazar PKS 1222+216

Ezhikode

Shukla

Dewangan

et al. 2022

ApJ

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The γ-ray emission from flat-spectrum radio quasars (FSRQs) is thought to be dominated by the inverse Compton scattering of the external sources of photon fields, e.g., accretion disk, broad-line region (BLR), and torus. FSRQs show strong optical emission lines and hence can be a useful probe of the variability in BLR output, which is the reprocessed disk emission. We study the connection between the optical continuum, Hγ line, and γ-ray emissions from the FSRQ PKS 1222+216, using long-term (∼2011–2018) optical spectroscopic data from Steward Observatory and γ-ray observations from Fermi Large Area Telescope (LAT). We measured the continuum (F C,opt) and Hγ (F Hγ ) fluxes by performing a systematic analysis of the 6029–6452 Å optical spectra. We observed stronger variability in F C,opt than F Hγ , an inverse correlation between the Hγ equivalent width and F C,opt, and a redder-when-brighter trend. Using discrete cross-correlation analysis, we found a positive correlation (DCF ∼ 0.5) between the F γ‐ray>100 MeV and F C,opt (6024–6092 Å) light curves with a time lag consistent with zero at the 2σ level. We found no correlation between the F γ‐ray>100 MeV and F Hγ light curves, probably dismissing the disk contribution to the optical and γ-ray variability. The observed strong variability in the Fermi-LAT flux and F γ‐ray>100 MeV − F C,opt correlation could be due to the changes in the particle acceleration at various epochs. We derived the optical-to-γ-ray spectral energy distributions during the γ-ray flaring and quiescent epochs that show a dominant disk component with no variability. Our study suggests that the γ-ray emission zone is likely located at the edge of the BLR or in the radiation field of the torus.

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Section: Summary and Discussionsupporting

confidence: 90%

Long-term Optical and γ-Ray Variability of the Blazar PKS 1222+216

Ezhikode

Shukla

Dewangan

et al. 2022

ApJ

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“…Such highly energized electrons are responsible for the observed abrupt rise seen in the multi-wavelength light curves for both cases. A similar remarkable rise in the X-ray light curve has previously been seen in FSRQ PKS 1222+216 (Chatterjee et al 2021). Very short lived X-ray flares have also been observed in PKS 2005−489 (Zhu et al 2018), where the variability timescale is found to be <30 s. Furthermore, Markowitz et al (2022) also found modest X-ray flares in Mkn 421 that last for less than a day.…”

Section: Implications Of Shocks On the Emission Signaturessupporting

confidence: 69%

A numerical study on the role of instabilities on multi-wavelength emission signatures of blazar jets

Acharya

Vaidya

Dihingia

et al. 2023

A&A

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Context. Blazars, a class of active galaxies whose jets are relativistic and collimated flows of plasma directed along the line of sight, are prone to a slew of magnetohydrodynamic (MHD) instabilities. These jets show characteristic multi-wavelength and multi-timescale variabilities. Aims. We aim to study the interplay of radiation and particle acceleration processes in regulating the multi-band emission and variability signatures from blazars. In particular, the goal is to decipher the impact of shocks arising due to MHD instabilities in driving the long-term variable emission signatures from blazars. Methods. To this end, we performed relativistic MHD (RMHD) simulations of a representative section of a blazar jet. The jet was evolved using a hybrid Eulerian-Lagrangian framework to account for radiative losses due to synchrotron process as well as particle acceleration due to shocks. Additionally, we incorporated and validated radiative losses taking into consideration the external Compton (EC) process that is relevant for blazars. We further compared the effects of different radiation mechanisms through numerical simulation of 2D slab jet as a validation test. Finally, we carried out a parametric study to quantify the effect of magnetic fields and external radiation field characteristics by performing 3D simulations of a plasma column. The synthetic light curves and spectral energy distribution (SEDs) were analyzed to qualitatively understand the impact of instability driven shocks. Results. We observed that shocks produced with the evolution of instabilities give rise to flaring signatures in the high-energy band. The impact of such shocks is also evident from the instantaneous flattening of the synchrotron component of the SEDs. At later stages, we observed the transition in X-ray emission from the synchrotron process to that dominated by EC. The inclusion of the EC process also gives rise to γ-ray emission and shows signatures of mild Compton dominance that is typically seen in low-synchrotron peaked blazars.

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The exploration of the soft X-ray excess in FSRQ 4C+21.35 during the 2014 X-ray flare

Zhao,

Yin,

et al. 2023

Monthly Notices of the Royal Astronomical Society

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We report the soft X-ray excess feature and an opposite tendency between the optical/UV and X-ray bands during the flare that occurred in 2014 in flat-spectrum radio quasar (FSRQ) 4C+21.35 with the observations by Swift-XRT and Swift-UVOT. These unusual phenomena are rarely reported in FSRQs. The flare was covered from the optical to the X-ray while no prominent activity in the γ-ray was observed, which could be an indication of weaker jet activity during the flare. We carry out the spectral energy distribution ranging from the optical to X-ray based on four models which are the warm corona model (Model-1), the relativistic reflection model (Model-2), the corona with the jet model (Model-3), and the relativistic reflection with the jet model (Model-4). We find some extreme variation of the parameters in Model-2 and Model-4 and they are unable to explain the correlations between the optical/UV and X-ray bands. Model-1 and Model-3 can obtain reasonable parameters and provide an explanation for the observed opposite tendency between the optical/UV and X-ray bands. However, considering the weak jet activity during the X-ray flare, Model-1 is much preferred for describing the soft X-ray excess, hard X-ray emission, as well as the opposite tendency between the optical/UV and X-rays. Based on Model-1, it is suggested that the flare in 2014 is probably due to the variation of the geometry of the corona, which is expected to be more strictly tested with further observations in the future.

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Temporal and spectral study of PKS B1222 + 216 flares in 2014

Cited by 3 publications

References 44 publications

Long-term Optical and γ-Ray Variability of the Blazar PKS 1222+216

Long-term Optical and γ-Ray Variability of the Blazar PKS 1222+216

A numerical study on the role of instabilities on multi-wavelength emission signatures of blazar jets

The exploration of the soft X-ray excess in FSRQ 4C+21.35 during the 2014 X-ray flare

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