Exploring the Origin of Multiwavelength Emission from High-Redshift Blazar B3 1343 + 451
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EXPLORING THE ORIGIN OF MULTIWAVELENGTH EMISSION FROM HIGH-REDSHIFT BLAZAR B3 1343 + 451
N. Sahakyan1,2, G. Harutyunyan1, D. Israelyan1, and M. Khachatryan1
B3 1343 + 451 is a distant ( z 2.534 ) and bright flat-spectrum radio quasar observed in the J -ray band. The results from the multiwavelength observations of B3 1343 + 451 with Fermi-LAT and Swift are reported. In the J -ray band, strong flares were observed on 05 December 2011 and on 13 December 2009 when the flux increased up to (8.78 r 0.83) 10 -7 photon cm -2 s -1 . The hardest photon index * 1.73 r 0.24 has been observed on MJD 58089 which is not common for flat-spectrum radio quasars. The analysis of Swift XRT data shows that in 2014 the X-ray flux of the source increased ~2 times as compared to 2009, but in both periods the X-ray emission is characterized by a hard photon index of *X - ray
1.2 1.3 . During the J -ray flares, the shortest flux halving timescale was ~2.34 days, implying the
emission had been produced in a very compact region, R d G ct /(1 z ) 3.43 1016 cm (when G 20 ). The spectral energy distribution of B3 1343 + 451 is modeled during the quiescent and flaring periods assuming a compact emitting region outside the BLR. It is found that the flares can be explained by only changing the bulk Lorentz factor of the emitting region without significant modification of the emitting electron parameters and luminosity of the jet. Keywords: B3 1343 + 451: J -rays: X-rays: Blazars
1 2
ICRANet Armenia Marshall Baghramian Avenue 24a, 0019 Yerevan, Armenia, e-mail: [email protected] ICRANet Piazza della Republica 10, 65122 Pescara, Italy
Published in Astrofizika, Vol. 63, No. 3, pp. 375-390 (August 2020). Original article submitted June 24, 2020. 334
0571-7256/19/6303-0334 ©2020 Springer Science+Business Media, LLC
1. Introduction
Blazars are radio-loud active galactic nuclei (AGNs) the relativistic jets of which are inclined toward the observer, i.e. have a small angle (several degrees) to the line of sight [1]. Due to this small inclination angle and relativistic motion, the intensity of these sources is significantly boosted in the observer frame and is dominated by the non-thermal emission produced inside the jet [2]. Blazars are observed throughout the electromagnetic spectrum, from radio to High Energy (HE) J -rays, exhibiting a double-peaked structure. The first peak is believed to be produced from the synchrotron emission of electrons within the jet while the nature of the second component is debatable. Within well-known leptonic scenarios, this component is attributed to inverse Compton (IC) scattering of low-energy photons. The origin of the photon field mostly depends on the type of the blazars: for BL Lacs which have weak or no emission lines the synchrotron photons can serve as targets for IC scattering [3-5], while the SEDs of Flat Spectrum Radio Quasars (FSRQs) with stronger and quasar-like emission lines are better explained when the photons external to the jet are considered [6,7]. Alternatively, in hadronic scen
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