Clues on high-energy emission mechanism from blazar 3C 454.3 during 2015 August flare

Shah, Zahir; Sahayanathan, S.; Mankuzhiyil, N.; Kushwaha, Pankaj; Misra, Ranjeev; Iqbal, Naseer

doi:10.1093/mnras/stx1194

Cited by 35 publications

(29 citation statements)

References 54 publications

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“…Temperatures in this range are found in the outer regions of the torus. For instance, previous studies performed in 3C 454.3 and NGC 1068 (Jaffe et al 2004;Shah et al 2017) have derived a temperature of the order 300-600 K at a distance of ∼3.5 pc from the SMBH. Therefore, the distance that we obtain from our analysis can also be considered as a lower limit for the outer radius of the dusty torus.…”

Section: Location Of the Gamma-ray Emissionmentioning

confidence: 99%

Localizing the γ-ray emitting region in the blazar TXS 2013+370

Traianou

Krichbaum

Boccardi

et al. 2020

A&A

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Aims. The γ-ray production mechanism and its localization in blazars are still a matter of debate. The main goal of this paper is to constrain the location of the high-energy emission in the blazar TXS 2013+370 and to study the physical and geometrical properties of the inner jet region on sub-pc scales. Methods. TXS 2013+370 was monitored during 2002-2013 with VLBI at 15, 22, 43, and 86 GHz, which allowed us to image the jet base with an angular resolution of ≥ 0.4 pc. By employing CLEAN imaging and Gaussian model-fitting, we performed a thorough kinematic analysis at multiple frequencies, which provided estimates of the jet speed, orientation, and component ejection times. Additionally, we studied the jet expansion profile and used the information on the jet geometry to estimate the location of the jet apex. VLBI data were combined with single-dish measurements to search for correlated activity between the radio, mm, and γ-ray emission. For this purpose, we employed a cross-correlation analysis, supported by several significance tests. Results. The high-resolution VLBI imaging revealed the existence of a spatially bent jet, described by co-existing moving emission features and stationary features. New jet features, labeled as A1, N, and N1, are observed to emerge from the core, accompanied by flaring activity in radio/mm-bands and γ rays. The analysis of the transverse jet width profile constrains the location of the mm core to lie ≤2 pc downstream of the jet apex, and also reveals the existence of a transition from parabolic to conical jet expansion at a distance of ∼54 pc from the core, corresponding to ∼1.5 × 10 6 Schwarzschild radii. The cross-correlation analysis of the broad-band variability reveals a strong correlation between the radio-mm and γ-ray data, with the 1 mm emission lagging ∼ 49 days behind the γ rays. Based on this, we infer that the high energy emission is produced at a distance of the order of ∼1 pc from the jet apex, suggesting that the seed photon fields for the external Compton mechanism originate either in the dusty torus or in the broad-line region.

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Section: Location Of the Gamma-ray Emissionmentioning

confidence: 99%

Localizing the γ-ray emitting region in the blazar TXS 2013+370

Traianou

Krichbaum

Boccardi

et al. 2020

A&A

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“…The best fit results suggest that there is no significant variation in the bulk Lorentz factor Γ during different flux states. However, it can be noted that the obtained Γ values are lesser compared to the typical value as observed in other FSRQs (Shah et al 2017(Shah et al , 2019. Since the source parameters obtained through the spectral fit depend on the equipartition condition and other frozen quantities, relaxing these assumptions can result in larger Γ.…”

Section: Summary and Discussionmentioning

confidence: 73%

Temporal and spectral study of PKS 0208-512 during 2019-20 flare

Khatoon,

Prince,

Shah

et al. 2021

Preprint

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We present the temporal and spectral study of blazar PKS 0208-512, using recent flaring activity from November 2019 to March 2020, as detected by Fermi-LAT, Swift-XRT/UVOT observatories. The source was in a low γ-ray flux state for a decade and started flaring in November 2019, which continues until March 2020. During the activity state, 2-days binned γ-ray lightcurve shows multiple-peaks indicating sub-flares. To understand the possible physical mechanisms behind flux enhancement, a detailed temporal and spectral study has been carried out by dividing the activity into several flux-states. Timing analysis of lightcurves suggests that peaks of sub-flares have rise and decay time in days-order with flux-doubling time ∼ 2-days. The 2-days binned γ-ray lightcurve shows double-lognormal flux distribution. The broadband spectral energy distribution for three selected flux states can be well fitted under synchrotron, synchrotron-self-Compton (SSC) and external-Compton (EC) emission mechanisms. We obtained the physical parameters of the source and their confidence intervals through χ 2 -statistics. Our spectral study suggests that during quiescent-state, gamma-ray spectrum can be well explained by considering the EC-scattering of IR-photons from the dusty-torus. However, gamma-ray spectra corresponding to flares demand additional target photons from broad-line-region (BLR) along with the IR. These suggest that during flares, the emission-region is close to the edge of BLR, while for quiescent-state the emission-region is away from the BLR. The best-fit results suggest that, marginal increase in the magnetic-field can result in the flux enhancement. This is possibly associated with the efficiency of particle acceleration during flaring-states as compared to quiescent-state.

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“…For BLLs broadband SEDs, we have taken LBL phase of OJ 287, IBL S5 0716+714 (from Chandra et al 2015), and HBL PKS 2155-304 (from Gaur et al 2017, epoch 2012. For FSRQ, we have selected a quiescent and a flaring phase of 3C 454.3 from Shah et al (2017). In our conical jet model for a given γ-ray flare time scale (t var ) the emission region size L can be estimated as,…”

Section: Sed Comparison and Discussionmentioning

confidence: 99%

“…The other crucial factor is the number density of the soft photons which, in general, follow a monotonic declining trend with some powerlaw form or steeper from NIR to GeV/TeV energies. For example, when the electron energy distribution has single powerlaw distribution with index p, the synchrotron photon density is proportional to ν −(p−1)/2 (e.g., Shah et al 2017), so for p=2 the synchrotron photon density at 10 14 Hz (or, ≥ 10 14 Hz) is almost 10 times smaller than that at 10 12 Hz (or, ≥ 10 12 Hz). As a result, photons of frequency 10 26 Hz will see 10 times smaller photon density for pair production in comparison to the 10 28 Hz photons.…”

Section: The Pair Productionmentioning

confidence: 99%

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Blazars SED in Conical Plasma Flow : a Monte Carlo study

Kumar,

Kushwaha

2021

Preprint

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Blazars host the most powerful persistent relativistic conical jet-a highly collimated anisotropic flow of material/plasma. Motivated by this, we explore the blazar's broadband spectral energy distribution (SED) in an anisotropic flow of plasma which emits via synchrotron and inverse Compton (IC) mechanism. The flow is conical with two velocity components: a highly relativistic flow component along the jet axis and a random perpendicular component with average random Lorentz factor γ ran << than the average component along the jet axis γ . Assuming a broken power-law electron population, we calculated the broadband SED using synchrotron and IC processes assuming a cylindrical (of radius R and length L) emission region. For the IC process, we used Monte Carlo approach. We found that such anisotropic flow can reproduce blazars broadband emission as well as general short and high amplitude variability, indicating that spectral and temporal variability are not sufficient to distinguish among existing models. We demonstrate this by reproducing SEDs of FSRQ 3C 454.3 and three BL Lacs objects OJ 287, S5 0716+714, PKS 2155-304. Our formalism and set-up also allow us to investigate the effect of the geometry and dimension of emission region on observed broadband spectra. We found that the SEDs of low synchrotron peak (LSP) blazar can be explained by considering only SSC (synchrotron self-Compton) if R/L (< 0.01), broadly mimicking a spine-sheath geometry. In general, the degeneracy between non-thermal particle number density and length of the emission region (L) allow us to reproduce any variability in terms of particle number density.

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Clues on high-energy emission mechanism from blazar 3C 454.3 during 2015 August flare

Cited by 35 publications

References 54 publications

Localizing the γ-ray emitting region in the blazar TXS 2013+370

Localizing the γ-ray emitting region in the blazar TXS 2013+370

Temporal and spectral study of PKS 0208-512 during 2019-20 flare

Blazars SED in Conical Plasma Flow : a Monte Carlo study

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