arXivDaily arXiv每日学术速递 周一至周五更新
arXiv周末暂无论文更新,休息一下吧,周末愉快~~
arXiv 2501.03082astro-ph.HE
收藏

GRB 240825A 瞬时辐射中的双峰谱

A two-hump spectrum in the prompt emission of GRB 240825A

Hai-Ming Zhang, Zi-Qi Wang, Cui-Yuan Dai, Yi-Yun Huang, Ruo-Yu Liu, En-Wei Liang, Xiang-Yu Wang

AI总结:

本文报道在 GRB 240825A 中探测到带约 50 MeV 谱拐折的额外硬分量,折断幂律拟合优于指数截止模型,表明其为内禀峰值而非伽马射线对产生不透明度所致,并讨论了其辐射机制及 GeV 能段从瞬时辐射到余辉的转变。

摘要:

在费米大视场望远镜(Fermi LAT)探测到的若干伽马射线暴(GRB)中,除了典型的亚 MeV Band 分量之外,还出现了一个延伸至 GeV 能段的额外硬谱分量。此前仅在一个事例(即 GRB 090926A)中,在该额外硬分量的高能端识别出了谱拐折特征,但光子计数不足以在截止模型和折断幂律模型之间区分该谱拐折。在本工作中,我们报告在 GRB 240825A 中探测到一个显示出谱拐折的额外硬分量。我们发现,对于第二个辐射脉冲的时间分辨谱,折断幂律模型比带指数截止的单一幂律模型能更好地拟合该额外分量的谱数据,拐折能量约为 50 MeV。这一谱特征不利于将伽马射线对产生不透明度作为谱拐折的起源,而是指向该额外分量存在一个内禀峰值。额外硬分量峰值与 Band 分量峰值之间的低比值对额外分量的同步自康普顿起源提出了挑战。本文讨论了其他可能情形,例如光球辐射的逆康普顿散射。此外,我们在 GRB 240825A 中发现了 GeV 能段从瞬时辐射到余辉辐射的清晰转变,表现为时间上的陡降和独特的谱演化。

英文摘要:

An extra hard spectral component that extends to GeV energies, in additional to the typical sub- MeV Band component, appears in several gamma-ray burst (GRBs) detected by Fermi Large Area Telescopes (LAT). Only in one case (i.e., GRB 090926A), a spectral break feature at the high energy end is identified in the extra hard component, but the photon counts are not enough to distinguish between the cutoff model and the broken power law model for the spectral break. In this work, we report the detection of an extra hard component showing the spectral break in GRB 240825A. We find that a broken power-law model fits the spectral data of the extra component better than a single power-law with an exponential cutoff in the time resolved spectrum for the second emission pulse, with a break at about 50 MeV. This spectral feature disfavors the gamma-ray opacity to pair creation as the origin of the spectral break, but points to an intrinsic peak for the extra component. The low ratio between the peak of the extra hard component and that of the Band component challenges the synchrotron self-Compton origin for the extra component. Alternative scenarios, such as the inverse Compton scattering of the photosphere emission, are discussed. In addition, we find a clear transition from the prompt emission to afterglow emission at GeV energies in GRB 240825A, manifested by a temporal steep decay and an unique spectral evolution.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑