B3 1343 + 451 is a distant ( z = 2.534 ) and bright flat-spectrum radio quasar observed in the γ -ray band. The results from the multiwavelength observations of B3 1343 + 451 with Fermi-LAT and Swift are reported. In the γ -ray band, strong flares were observed on 05 December 2011 and on 13 December 2009 when the flux increased up to (8.78 ± 0.83)·10-7 photon cm-2 s-1. The hardest photon index Γ = 1.73 ± 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 ΓX-ray = 1.2–1.3. During the γ -ray flares, the shortest flux halving timescale was ~2.34 days, implying the emission had been produced in a very compact region, R ≤ δ ct /(1 + z) = 3.43·1016 cm (when δ = 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.

中文翻译：

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探索高红移耀变体 B3 1343 + 451 多波长发射的起源

B3 1343 + 451 是一个遥远的（z = 2.534）和明亮的平谱射电类星体，在γ射线波段观测到。报告了使用 Fermi-LAT 和 Swift 对 B3 1343 + 451 进行多波长观测的结果。在 γ 射线波段，在 2011 年 12 月 5 日和 2009 年 12 月 13 日观测到强耀斑，通量增加到 (8.78 ± 0.83)·10-7 光子 cm-2 s-1。在 MJD 58089 上观察到最硬的光子指数 Γ = 1.73 ± 0.24，这在平谱射电类星体中并不常见。对 Swift XRT 数据的分析表明，2014 年源的 X 射线通量比 2009 年增加了约 2 倍，但在这两个时期，X 射线发射的特征在于硬光子指数 ΓX-ray = 1.2– 1.3. 在γ射线耀斑期间，最短的通量减半时间尺度为~2.34天，这意味着发射是在一个非常紧凑的区域产生的，R ≤ δ ct /(1 + z) = 3.43·1016 cm（当 δ = 20 时）。B3 1343 + 451 的光谱能量分布是在静止和燃烧期间模拟的，假设 BLR 外有一个紧凑的发射区域。发现可以通过仅改变发射区的体积洛伦兹因子而不显着修改发射电子参数和射流的光度来解释耀斑。