Inverse Compton signatures of gamma-ray burst afterglows
Inverse Compton signatures of gamma-ray burst afterglows
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DOI：
10.1093/mnras/staa1583
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发表时间：
2019-10
影响因子：
4.8
通讯作者：
Hao Zhang;I. Christie;M. Petropoulou;J. M. Rueda-Becerril;D. Giannios
中科院分区：
文献类型：
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作者：
Hao Zhang;I. Christie;M. Petropoulou;J. M. Rueda-Becerril;D. Giannios
伽玛射线暴的余辉发射被认为是由相对论性冲击波驱动到环暴介质中产生的。虽然从射电到X射线频率的余辉辐射被认为是由相对论性的非热电子在冲击波加速下发出的同步辐射所产生的，但在高能（He; 10 GeV）下的辐射来源仍然不确定。主要大气伽马成像切伦科夫望远镜（MAGIC）最近探测到GRB 190114 C的亚TeV辐射，引发了关于甚高能量（VHE; 10300 GeV）辐射的进一步争论。在这里，我们探讨逆康普顿的情况下，作为候选人的HE和VHE排放，考虑两个来源的种子光子散射：同步光子从冲击波（同步自康普顿或SSC）和各向同性光子场外部的冲击波（外部康普顿）。对于每种情况，我们计算的多波长余辉光谱和光变曲线。我们发现，SSC将占主导地位的粒子冷却和GeV的排放，除非一个密集的环境红外光子场，典型的恒星形成区域，是存在的。此外，考虑到河外背景光衰减，我们讨论了VHE余辉的探测能力，现有的和未来的伽马射线仪器的广泛的模型参数。通过对GRB 190114 C的研究，发现其在费米大面积望远镜（LAT）波段的余辉辐射是同步辐射为主的。最新的费米-LAT测量（即t = 104 s）和MAGIC观测也为假定的外部红外光子场的能量密度设定了上限（即${\lesssim} 3\times 10^{-9}\，{\rm erg\，cm^{-3}}$），使得逆康普顿在亚TeV能量中占主导地位。
The afterglow emission from gamma-ray bursts (GRBs) is believed to originate from a relativistic blast wave driven into the circumburst medium. Although the afterglow emission from radio up to X-ray frequencies is thought to originate from synchrotron radiation emitted by relativistic, non-thermal electrons accelerated by the blast wave, the origin of the emission at high energies (HE; ≳GeV) remains uncertain. The recent detection of sub-TeV emission from GRB 190114C by the Major Atmospheric Gamma Imaging Cherenkov Telescopes (MAGIC) raises further debate on what powers the very high energy (VHE; ≳300 GeV) emission. Here, we explore the inverse Compton scenario as a candidate for the HE and VHE emissions, considering two sources of seed photons for scattering: synchrotron photons from the blast wave (synchrotron self-Compton or SSC) and isotropic photon fields external to the blast wave (external Compton). For each case, we compute the multiwavelength afterglow spectra and light curves. We find that SSC will dominate particle cooling and the GeV emission, unless a dense ambient infrared photon field, typical of star-forming regions, is present. Additionally, considering the extragalactic background light attenuation, we discuss the detectability of VHE afterglows by existing and future gamma-ray instruments for a wide range of model parameters. Studying GRB 190114C, we find that its afterglow emission in the Fermi-Large Area Telescope (LAT) band is synchrotron dominated. The late-time Fermi-LAT measurement (i.e. t ∼ 104 s), and the MAGIC observation also set an upper limit on the energy density of a putative external infrared photon field (i.e. ${\lesssim} 3\times 10^{-9}\, {\rm erg\, cm^{-3}}$), making the inverse Compton dominant in the sub-TeV energies.