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arXiv 2108.01028astro-ph.HE
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3C 279宽线区边缘的成对级联形成3C 279的Gamma-Ray谱

Pair Cascades at the Edge of the Broad-Line Region Shaping the Gamma-Ray Spectrum of 3C 279

Christoph Wendel, Amit Shukla, Karl Mannheim

摘要:

耀变体3C 279发射出的伽马射线通量在时间尺度上是可变的,其时间尺度短至光穿过其中心黑洞的事件视界的时间。通常的报道是,光谱能量分布(SED)没有显示出对衰减的迹象,由于伽马射线与周围的紫外光子的相互作用,得出的结论是,伽马射线必须起源于宽线区域(BLR)以外的射流中的子结构。我们解决的光谱签名印记的原子发射线的γ射线光谱产生的逆康普顿对级联的光子场的BLR。利用MJD 58129 - 58150的费米大面阵望远镜数据,高精度地测定了3C 279的γ射线自相关谱,并模拟了三种不同注入项下的对级联谱。得到了与观测数据的满意拟合。所获得的SED显示的特征印记对生产原子发射线光子由于光学厚辐射传输,但缺乏进一步的指数衰减预期,如果发射区域将深埋在BLR。3C 279的SED与没有指数外部对吸收的逆康普顿对级联光谱一致。我们的研究结果支持了3C 279的伽马射线发射起源于BLR边缘的观点。

英文摘要:

The blazar 3C 279 emits a flux of gamma-rays that is variable on timescales as short as the light-crossing time across the event horizon of its central black hole. It is commonly reported that the spectral energy distribution (SED) does not show signs of pair attenuation due to interactions of the gamma rays with ambient ultraviolet photons, concluding that the gamma rays must originate from substructures in the jet outside of the broad-line region (BLR). We address the spectral signature imprinted by atomic emission lines on the gamma-ray spectrum produced by an inverse-Compton pair cascade in the photon field of the BLR. We determine with high precision the gamma-ray SED of 3C 279 using Fermi Large Area Telescope data from MJD 58129 - 58150 and simulate the pair cascade spectrum for three different injection terms. Satisfactory fits to the observational data are obtained. The obtained SED shows features imprinted by pair production on atomic emission line photons due to optically thick radiation transport, but lacking further exponential attenuation expected if the emission region would lie buried deep within the BLR. The SED of 3C 279 is consistent with an inverse-Compton pair cascade spectrum without exponential external pair absorption. Our findings support the view that the gamma-ray emission in 3C 279 originates from the edge of the BLR.

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