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

Ezhikode, Savithri H.; Shukla, Amit; Dewangan, G. C.; Pawar, Pramod; Agarwal, Sushmita; Mathew, Blesson; R., Akhil Krishna

doi:10.3847/1538-4357/ac9627

Cited by 4 publications

(3 citation statements)

References 59 publications

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“…Low-activity periods are typically associated with the outer parsec-scale regions of the jet or result from combined emissions along the entire jet length in the absence of a dominant emission zone. High-activity periods are primarily linked to emission originating from energetic particles within the inner jet at parsec scales from black hole (Ezhikode et al 2022). Additionally, high Compton dominance in the source (q ∼ 30; Abhir et al 2021) indicates that accelerated high-energy electrons in the jet scatter a fraction of soft photons, emitting γrays.…”

Section: Discussionmentioning

confidence: 99%

Imprint of “Local Opacity” Effect in Gamma-Ray Spectrum of Blazar Jet

Agarwal,

Shukla,

Mannheim

et al. 2024

ApJL

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Relativistic jets from accreting supermassive black holes at cosmological distances can be powerful emitters of γ-rays. However, the precise mechanisms and locations responsible for the dissipation of energy within these jets, leading to observable γ-ray radiation, remain elusive. We detect evidence for an intrinsic absorption feature in the γ-ray spectrum at energies exceeding 10 GeV, presumably due to the photon–photon pair production of γ-rays with low-ionization lines at the outer edge of broad-line region (BLR), during the high-flux state of the flat-spectrum radio quasar PKS 1424−418. The feature can be discriminated from the turnover at higher energies resulting from γ-ray absorption in the extragalactic background light. It is absent in the low-flux states, supporting the interpretation that powerful dissipation events within or at the edge of the BLR evolve into fainter γ-ray emitting zones outside the BLR, possibly associated with the moving very long baseline interferometry radio knots. The inferred location of the γ-ray emission zone is consistent with the observed variability timescale of the brightest flare, provided that the flare is attributed to external Compton scattering with BLR photons.

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Section: Discussionmentioning

confidence: 99%

Imprint of “Local Opacity” Effect in Gamma-Ray Spectrum of Blazar Jet

Agarwal,

Shukla,

Mannheim

et al. 2024

ApJL

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“…Cross-correlation plots for pairs of GeV and MeV band light curves, for a lag of ±60 days, are depicted in Figure 2. A bootstrap method is then applied to obtain the confidence limits of the correlation (e.g., Ezhikode et al 2022) between MeV and GeV band light curves. This involves simulating 50,000 random subsets of the original light-curve pairs, with each subset containing 80% of the original data points.…”

Section: Light Curve Correlation Analysismentioning

confidence: 99%

Probing the Gamma-Ray Emission Region of Five TeV Flat Spectrum Radio Quasars

Xiao,

Cao,

Xue

et al. 2024

Res. Astron. Astrophys.

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The location of $\gamma$-ray emission of blazars remains a contested topic, inspiring the development of numerous investigative techniques to address this issue.In this work, we analyzed \textit{Fermi} $\gamma$-ray lightcurves in the GeV and MeV bands, employing the discrete cross-correlation function (DCF) method to discern time lags between the two bands.For 4C +21.35, Ton 599, B2 1420+32, and PKS 1510-089, we identified a time lag spanning several days, while for PKS 1441+25, the time lag was not statistically found.The results imply that the soft photons necessary for inverse Compton scattering predominantly originate from the dusty torus (DT) in the first four sources, whereas for PKS 1441+25, they seem to be sourced mainly from the BLR.Further analysis of the opacity ($\tau_{\gamma \gamma}$) and the GeV spectra study supports the conclusion that the location of the dissipation region must be beyond the BLR to avoid significant absorption. Notably, for PKS 1441+25, the emission region is also posited to lie outside yet proximate to the BLR.The parameters of describing the emission region were obtained by fitting broadband spectral energy distribution (SED) with contemporaneous observation data.Our findings suggest that for the five TeV FSRQs, during TeV flaring events, the jet appears to maintain an equilibrium between the energy density of the magnetic field and that of the particles for all investigated sources, with the exceptions of 4C +21.35 and PKS 1441+25.In terms of the overall jet power, particle energy is the dominant contributor, and the observed blazar radiation cannot be solely attributed to the magnetic field, except in the case of 4C +21.35. Consequently, magnetic reconnection is unlikely to be the primary mechanism behind particle acceleration in these systems.

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“…Ikejiri et al 2011;Itoh et al 2016, Roy et al 2023, andreferences therein). FSRQs show strong optical emission lines and can be a useful probe of the variability in BLR output, which mightly come from the disk emission (Ezhikode et al 2022).…”

Section: Introductionmentioning

confidence: 99%

Multimessenger Studies of One Subclass of Active Galactic Nucleus: Blazar

Yuan¹

2023

Preprint

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In this article, we introduce some multi-messenger studies of blazars. Main contents contain the following parts, 1. the subclasses of blazars and the observational characteristics, 2. emission variabilities from the multi-messenger observations, 3. the physical origin for the multi-messenger studies. Based on mid-IR observations collected from the $WISE$ database, we collect two sources (BZQ J1700+6830 and BZQ J1842+6809) to analyze the mid-IR variabilities. \\ (1) For BZQ J1700+6830, the period is $P\approx$ 42 hr at the four bands ($W1$, $W2$, $W3$, $W4$); for BZQ J1842+6809, the period is $P\approx$ 123 hr at the two bands ($W1$, $W2$). \\ (2) Using the periodicities, we calculate that the central black hole mass ($BH$) should be $M = (5.44\sim33.0)\times10^8M_{\odot}$ for BZQ J1700+6830 and $M = (1.13\sim6.88)\times10^9M_{\odot}$ for BZQ J1842+6809.\\ (3) For the two sources, during the flaring stage, we find anti-clockwise variation trends based on the time-based relations built by the spectral indices ($\alpha$) and flux densities ($F$).\\ (4) We calculate the Doppler factor ($\delta$) when the sources are in the dimming or brightening stages, and find that with the frequency increasing, the Doppler factor become stronger.

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

Cited by 4 publications

References 59 publications

Imprint of “Local Opacity” Effect in Gamma-Ray Spectrum of Blazar Jet

Imprint of “Local Opacity” Effect in Gamma-Ray Spectrum of Blazar Jet

Probing the Gamma-Ray Emission Region of Five TeV Flat Spectrum Radio Quasars

Multimessenger Studies of One Subclass of Active Galactic Nucleus: Blazar

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