On the Origin and Evolution of Curvature of the Spectral Energy Distribution of Fermi Bright Blazars

Anjum, Muhammad S.; Chen, Liang; Gu, Minfeng

doi:10.3847/1538-4357/ab99a1

Cited by 12 publications

(9 citation statements)

References 77 publications

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“…As a result, the rapid 𝛾-ray flares can be explained by the energetic and accelerated electrons (Γ 𝑒 = 2.25 ± .0.15) inside the highly magnetized (𝐵 = 4.14 G) and compact (𝑅 = 9 × 10 15 cm) emitting region. These values are similar to the estimated values obtained from previous studies of 4C 28.02 and other blazars (Zhang et al 2014;Zheng et al 2017;Anjum et al 2020).…”

Section: Discussionsupporting

confidence: 91%

Multi-wavelength observations of the Blazar 4C +28.07

Zargaryan,

Mackey,

Barnouin

et al. 2021

Preprint

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The active galactic nucleus 4C +28.07 is a flat spectrum radio quasar, one of the brightest at 𝛾-ray energies. We study its multi-wavelength emission by analysing ∼ 12.3 years of Fermi-LAT data in the 𝛾-ray band and Swift-XRT/UVOT available data in X-ray and Optical-to-Ultraviolet bands. In the 𝛾-ray band, five flaring periods have been detected, during which the flux dramatically increases by several times (>5) compared with its average quiescent phase. Quasi-simultaneously with the flaring times, the X-ray and UVOT data detected by Swift-XRT/UVOT have also been analysed. In one of the brightest flare periods (Flare 5; observed on Oct 12, 2018) the 𝛾-ray flux reached (6.7 ± 0.81) × 10 −6 photon cm −2 s −1 (∼ 31× higher than the mean flux over 12.3 years) with detection significance of 𝜎 = 6.1. The apparent 𝛾-ray luminosity of this flaring corresponds to 3.6 × 10 49 erg/s (for a distance of 8.38 Gpc), one of the highest 𝛾-ray luminosities observed for blazars. The Bayesian-block analysis approach for Flare 5 has an estimated ∼ 2 hours time block, which can be considered the average 𝛾-ray variability time. The variability time constrains the 𝛾-ray emitting region size to ≤ 9 × 10 14 cm, which is close to the black hole radius. The spectral energy distributions (SEDs) in the 𝛾-ray band for the ∼ 12.3 years of data show an early cut-off at ∼ 14 GeV; beyond ∼ 60 GeV, however, the spectrum hardens and is detected up to ∼ 316 GeV. Similar spectral behaviour is also noticeable for the SEDs of flares, which can be linked to the photon absorption by the emitting region's internal and external narrow-band radiation fields. The SEDs are modelled and explained in the leptonic scenario. In the quiescent period, the 𝛾-ray emission was described by the Synchrotron-Self-Compton scenario, while the external photons contributions from the Disk and the broad-line region were required to explain the short-term flaring 𝛾-ray emission. Considering the significance of the obtained results from 4C +28.07, we compared the parameters with 3C 279 and M87, to motivate further studies.

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Section: Discussionsupporting

confidence: 91%

Multi-wavelength observations of the Blazar 4C +28.07

Zargaryan,

Mackey,

Barnouin

et al. 2021

Preprint

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“…Other researches also found anti-correlations between b and ν p (Tramacere et al 2007(Tramacere et al , 2009(Tramacere et al , 2011. Recently, Anjum et al (2020) found that BL Lacs show an anti-correlation between r of a log-parabolic EED and its peak energy γ p , which is a signature of stochastic acceleration. Particle acceleration mechanisms can produce the log-parabolic EED (see e.g., Kardashev 1962;Massaro et al 2004aMassaro et al , 2006Tramacere et al 2011;Chen 2014).…”

Section: Discussionmentioning

confidence: 90%

“…Particle acceleration mechanisms can produce the log-parabolic EED (see e.g., Kardashev 1962;Massaro et al 2004aMassaro et al , 2006Tramacere et al 2011;Chen 2014). The intrinsic curvature r in the EED arises due to the combined effect of particle acceleration and radiative cooling (e.g., Anjum et al 2020). The anti-correlation between b and ν p might originate from that between r and γ p .…”

Section: Discussionmentioning

confidence: 99%

Spectroscopic Monitoring of Blazar S5 0716+714: Brightness-Dependent Spectral Behavior

Feng,

Yang,

Yang

et al. 2020

Preprint

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In this paper, we report the new results of spectroscopic observations of γ-ray blazar S5 0716+714 from 2019 September to 2020 March with the 2.4 m optical telescope at Lijiang Observatory of Yunnan Observatories. The median cadence of observations is ∼ 1 day. During the second observation period (Epoch2), the observational data reveal an extremely bright state and a bluer-when-brighter (BWB) chromatism. The BWB trend of Epoch2 differs significantly from that of the first observation period (Epoch1). A significantly brightness-dependent BWB chromatism emerges in the total data of Epoch1 and Epoch2. The BWB trend becomes weaker towards the brighter states, and likely becomes saturated at the highest state. Based on a log-parabolic function, a power-law of synchrotron peak flux and frequency ν p , and a power-law of the curvature of synchrotron spectrum and its ν p , simulation well reproduces the brightness-dependent BWB trend of S5 0716+714. The BWB trend is seemingly controlled by the shift of ν p with respect to the observational window, and effectively may be dominated by the variations of electron average energy and magnetic field in emitting region.

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“…In addition, in Figure 1, the SED fitting result (total emission) using the log-parabolic electron spectrum is indicated by the long-dashed-dashed (blue) line, which exhibits a strong curvature in the Fermi GeV -ray band. In terms of intuitive phenomenology, the curvature-type radiation particle distribution may be more inclined to produce a curvature-type radiation photon spectrum (see Massaro et al 2004aMassaro et al ,b, 2006Anjum et al 2020); the broken-type radiation particle distribution may be more inclined to produce a broken-type radiation photon spectrum. Here, the curvature spectrum cannot effectively produce the -ray spectrum break (see Figure 1).…”

Section: −Ray Origin Of 3c 4543mentioning

confidence: 99%

On the origin of GeV spectral break for Fermi blazars: 3C 454.3

Kang,

Zheng,

et al. 2021

Preprint

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The GeV break in spectra of the blazar 3C 454.3 is a special observation feature that has been discovered by the Fermi-LAT. The origin of the GeV break in the spectra is still under debate. In order to explore the possible source of GeV spectral break in 3C 454.3, a one-zone homogeneous leptonic jet model, as well as the McFit technique are utilized for fitting the quasi-simultaneous multi-waveband spectral energy distribution (SED) of 3C 454.3. The outside border of the broad-line region (BLR) and inner dust torus are chosen to contribute radiation in the model as external, seed photons to the external-Compton process, considering the observed -ray radiation. The combination of two components, namely the Compton-scattered BLR and dust torus radiation, assuming a broken power-law distribution of emitted particles, provides a proper fitting to the multi-waveband SED of 3C 454.3 detected 2008 Aug 3 -Sept 2 and explains the GeV spectral break. We propose that the spectral break of 3C 454.3 may originate from an inherent break in the energy distribution of the emitted particles and the Klein-Nishina effect. A comparison is performed between the energy density of the 'external' photon field for the whole BLR BLR achieved via model fitting and that constrained from the BLR data. The distance from the position of the -ray radiation area of 3C 454.3 to the central black hole could be constrained at ∼ 0.78pc (∼ 4.00 BLR , the size of the BLR).

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On the Origin and Evolution of Curvature of the Spectral Energy Distribution of Fermi Bright Blazars

Cited by 12 publications

References 77 publications

Multi-wavelength observations of the Blazar 4C +28.07

Multi-wavelength observations of the Blazar 4C +28.07

Spectroscopic Monitoring of Blazar S5 0716+714: Brightness-Dependent Spectral Behavior

On the origin of GeV spectral break for Fermi blazars: 3C 454.3

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