Multiband Observations of the Quasar PKS 2326–502 during Active and Quiescent Gamma-Ray States in 2010–2012

Dutka, M.; Carpenter, B.; Ojha, R.; Finke, J.; D’Ammando, F.; Kadler, M.; Edwards, P. G.; Stevens, J.; Torresi, E.; Grandi, P.; Nesci, R.; Krauß, F.; Müller, C.; Wilms, J.; Gehrels, N.

doi:10.3847/1538-4357/835/2/182

Cited by 12 publications

(10 citation statements)

References 43 publications

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“…Such a large value is consistent with the apparent speed of jet components seen with radio Very Long Baseline Interferometry (VLBI), which can be as high as β app = 78 (Jorstad et al 2017). In previous modeling efforts, it was found that varying only the electron distribution was necessary to reproduce several states from FSRQs (e.g., D'Ammando et al 2013;Ackermann et al 2014;Buson et al 2014) although this is not always the case (e.g., Dutka et al 2013Dutka et al , 2017. For the SEDs of PKS 0346−27, we attempted to model all states varying only the electron distribution.…”

Section: Sed Modelingsupporting

confidence: 62%

“…We then varied the size of the emitting region and the magnetic field to model the states. Therefore, based on the classification of Dutka et al (2013Dutka et al ( , 2017, all of the modeled flares from PKS 0346−27 are type 2 flares 7 .…”

Section: Sed Modelingmentioning

confidence: 99%

“…Dutka et al (2013Dutka et al ( , 2017 classified flares into type 1, which can be modeled by changing the electron distribution only, and type 2, which require changes in other parameters such as the magnetic field strength or emission region size…”

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confidence: 99%

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The large gamma-ray flare of the flat-spectrum radio quasar PKS 0346−27

Angioni

Nesci²,

Finke³

et al. 2019

A&A

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Aims. In this paper, we characterize the first γ-ray flaring episode of the FSRQ PKS 0346−27 (z = 0.991), as revealed by Fermi-LAT monitoring data, and the concurrent multi-wavelength variability observed from radio through X-rays. Methods. We study the long and short term flux and spectral variability from PKS 0346−27 by producing γ-ray light curves with different time binning. We complement the Fermi-LAT data with multi-wavelength observations from ALMA (radio mm-band), REM (NIR) and Swift (optical-UV, X-rays). This quasi-simultaneous multi-wavelength coverage allowed us to construct time-resolved spectral energy distributions (SEDs) of PKS 0346−27, and compare the broadband spectral properties of the source between different activity states using a one-zone leptonic emission model. Results. PKS 0346−27 entered an elevated γ-ray activity state starting from the beginning of 2018. The high-state continued throughout the year, displaying the highest fluxes in May 2018. We find evidence of short-time scale variability down to ∼ 1.5 hours, which constrains the γ-ray emission region to be compact. The extended flaring period was characterized by a persistently harder spectrum with respect to the quiescent state, indicating changes in the broadband spectral properties of the source. This was confirmed by the multi-wavelength observations, which show a shift in the position of the two SED peaks by ∼ 2 orders of magnitude in energy and peak flux value. As a result, during the high state the non-thermal jet emission completely outshines the thermal contribution from the dust torus and accretion disk. The broadband SED of PKS 0346−27 transitions from a typical Low-Synchrotron-Peaked (LSP) to the Intermediate-Synchrotron-Peaked (ISP) class, a behavior previously observed in other flaring γ-ray sources. Our one-zone leptonic emission model of the high-state SEDs constrains the γ-ray emission region to have a lower magnetic field, larger radius, and higher maximum electron Lorentz factors with respect to the quiescent SED. Finally, we note that the bright and hard γ-ray spectrum observed during the peak of flaring activity in May 2018 implies that PKS 0346−27 could be a promising target for future ground-based Cherenkov observatories such as the Cherenkov Telescope Array (CTA). The CTA could detect such a flare in the low-energy tail of its energy range during a high state such as the one observed in May 2018.

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Section: Sed Modelingsupporting

confidence: 62%

Section: Sed Modelingmentioning

confidence: 99%

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The large gamma-ray flare of the flat-spectrum radio quasar PKS 0346−27

Angioni

Nesci²,

Finke³

et al. 2019

A&A

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“…At fixed time binning, when long time intervals are used, a possible fast flux variation will be smoothed out, while using short bins might result in many upper limits during the low-activity periods. In the adaptive binning approach, the time bin widths are adjusted to produce bins with constant flux uncertainty above the optimal energy (E 0 ) and this appraoch is proved to be a powerful method to search for γ-ray flux variation (e.g., Rani et al 2013b;Sahakyan et al 2018;Baghmanyan et al 2017;Gasparyan et al 2018;Dutka et al 2017;Zargaryan et al 2017). E 0 depends on the flux and photon index of each source and can be computed following Lott et al (2012).…”

Section: γ-Ray Variabilitymentioning

confidence: 99%

Multiwavelength Study of High-Redshift Blazars

Sahakyan,

Israyelyan,

Harutyunyan

et al. 2020

Preprint

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High-redshift blazars are among the most powerful objects in the Universe. The spectral and temporal properties of thirty-three distant blazars (z > 2.5) detected in the high energy γ-ray band are investigated by analyzing the Fermi-LAT and Swift UVOT/ XRT data. The considered sources have soft time averaged γ-ray spectra (Γ γ ≥ 2.2) whereas those that have been observed in the X-ray band have hard X-ray spectra (Γ X = 1.01 − 1.86). The γ-ray flux of high-redshift blazars ranges from 4.84 × 10 −10 to 1.50 × 10 −7 photon cm −2 s −1 and the luminosity is within (0.10 − 5.54) × 10 48 erg s −1 which during the γ-ray flares increases up to (0.1 − 1) × 10 50 erg s −1 . In the X-ray band, only the emission of PKS 0438-43, B2 0743+25 and TXS 0222+185 is found to vary in different Swift XRT observations whereas in the γ-ray band, the emission is variable for fourteen sources: the flux of B3 1343+451 and PKS 0537-286 changes in sub-day scales, that of PKS 0347-211 and PKS 0451-28 in day scales, while the γ-ray variability of the others is in week or month scales. The properties of distant blazar jets are derived by modeling the multiwavelength spectral energy distributions within a one-zone leptonic scenario assuming that the X-ray and γ-ray emissions are produced from inverse Compton scattering of synchrotron and dusty torus photons. From the fitting, the emission region size is found to be ≤ 0.05 pc and the magnetic field and the Doppler factor are correspondingly within 0.10 − 1.74 G and 10.0 − 27.4. By modeling the optical-UV excess, we found that the central black hole masses and accretion disk luminosities are within L d ≃ (1.09 − 10.94) × 10 46 erg s −1 and (1.69 − 5.35) × 10 9 M ⊙ , respectively.

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“…The multiwavelength "snapshots" of blazar activity, i.e., the SEDs, can provide important clues to the emission processes and the physical parameters related to them within the relativistic jet, at least within a particular model set. This is usually attempted through solving the kinetic equation of the population of electrons injected with a certain energy distribution and evolving under radiative and adiabatic energy losses in, and escaping from, a single emission zone (Chiaberge & Ghisellini 1999;Lindfors et al 2005;Sikora et al 2009;Abdo et al 2011a,b;Paliya et al 2015;Hayashida et al 2015;Aleksić et al 2015;Saito et al 2015;Dutka et al 2017;Hu et al 2021). Such modeling efforts usually include an additional accretion disk component to fully describe the SED, although this component is more often necessary in the case of FSRQs (e.g., Castignani et al 2013; Sbar- Panel (a) gives the 7-day integration bin γ-ray fluxes from the Fermi-LAT satellite (0.1-300 GeV).…”

Section: Introductionmentioning

confidence: 99%