Broadband γ-Ray Spectrum of Supernova Remnant Cassiopeia A

The Astrophysical Journal Letters Pub Date : 2025-03-20 DOI:10.3847/2041-8213/adb97c

Zhen Cao, F. Aharonian, Y. X. Bai, Y. W. Bao, D. Bastieri, X. J. Bi, Y. J. Bi, W. Bian, A. V. Bukevich, C. M. Cai, W. Y. Cao, Zhe Cao, J. Chang, J. F. Chang, A. M. Chen, E. S. Chen, H. X. Chen, Liang Chen, Long Chen, M. J. Chen, M. L. Chen, Q. H. Chen, S. Chen, S. H. Chen, S. Z. Chen, T. L. Chen, X. B. Chen, X. J. Chen, Y. Chen, N. Cheng, Y. D. Cheng, M. C. Chu, M. Y. Cui, S. W. Cui, X. H. Cui, Y. D. Cui, B. Z. Dai, H. L. Dai, Z. G. Dai, Danzengluobu, Y. X. Diao, X. Q. Dong, K. K. Duan, J. H. Fan, Y. Z. Fan, J. Fang, J. H. Fang, K. Fang, C. F. Feng, H. Feng, L. Feng, S. H. Feng, X. T. Feng, Y. Feng, Y. L. Feng, S. Gabici, B. Gao, C. D. Gao, Q. Gao, W. Gao, W. K. Gao, M. M. Ge, T. T. Ge, L. S. Geng, G. Giacinti, G. H. Gong, Q. B. Gou, M. H. Gu, F. L. Guo, J. Guo, X. L. Guo, Y. Q. Guo, Y. Y. Guo, Y. A. Han, O. A. Hannuksela, M. Hasan, H. H. He, H. N. He, J. Y. He, X. Y. He, Y. He, S. Hern ndez-Cadena, Y. K. Hor, B. W. Hou, C. Hou, X. Hou, H. B. Hu, S. C. Hu, C. Huang, D. H. Hua..

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Abstract

The core-collapse supernova remnant (SNR) Cassiopeia A (Cas A) is one of the brightest galactic radio sources with an angular radius of . Although no extension of this source has been detected in the γ-ray band, using more than 1000 days of LHAASO data above ∼0.8 TeV, we find that its spectrum is significantly softer than those obtained with Imaging Air Cherenkov Telescopes (IACTs), and its flux near ∼1 TeV is about 2 times higher. In combination with analyses of more than 16 yr of Fermi-LAT data covering 0.1 GeV–1 TeV, we find that the spectrum above 30 GeV deviates significantly from a single power law and is best described by a smoothly broken power law with a spectral index of 1.90 ± 0.15stat (3.41 ± 0.19stat) below (above) a break energy of 0.63 ± 0.21stat TeV. Given differences in the angular resolution of LHAASO-WCDA and IACTs, TeV γ-ray emission detected with LHAASO may have a significant contribution from regions surrounding the SNR illuminated by particles accelerated earlier, which, however, are treated as background by IACTs. Detailed modeling can be used to constrain the acceleration processes of TeV particles in the early stage of SNR evolution.

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仙后座A超新星遗迹的宽带γ射线谱

核心坍缩超新星遗迹仙后座A （Cassiopeia A, Cas A）是最亮的星系射电源之一，角半径为。虽然在γ射线波段没有检测到该源的扩展，但使用超过1000天的LHAASO数据在~ 0.8 TeV以上，我们发现它的光谱比用成像空气切伦科夫望远镜（IACTs）获得的光谱要软得多，并且它在~ 1 TeV附近的通量大约高2倍。结合对超过16年覆盖0.1 GeV - 1 TeV的Fermi-LAT数据的分析，我们发现30 GeV以上的光谱明显偏离单一幂律，最好用平滑破能幂律来描述，其光谱指数为1.90±0.15stat(3.41±0.19stat)，低于（高于）0.63±0.21stat TeV的破能。考虑到LHAASO- wcda和IACTs的角度分辨率差异，LHAASO探测到的TeV γ射线发射可能有很大的贡献来自于信噪比周围被加速粒子照射的区域，而这些区域被IACTs作为背景处理。详细的模型可以用来约束TeV粒子在信噪比演化早期的加速过程。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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The Astrophysical Journal Letters

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