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arXiv 1006.3897astro-ph.HE
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伽马射线暴高能辐射的局域吸收

Local absorption of high-energy emission from gamma-ray bursts

Rudy C. Gilmore, Enrico Ramirez-Ruiz

摘要:

由伽马射线暴(GRB)发射的高能光子与低能光子相互作用,产生有效光学深度。在这封信中,我们估计的不透明度所造成的光子场位于不同的距离长伽玛射线暴网站:的大质量恒星的祖先,恒星形成的分子云包含伽玛射线暴,和总光子场的宿主星系的双星伴星。前两个光子场被发现是透明的最合理的假设这些系统。在银河系辐射场的情况下,我们已经进行了几次数值模拟,以计算预期的不透明度为不同的视线几何形状通过宿主星系,并包括一个完整的会计产生的红外辐射的吸收和再辐射的星光尘埃。GeV伽马射线的光学深度,由于直接星光是小于所有宿主星系的统一。在较高能量($>$ 10 TeV)下,由于尘埃再辐射的中红外至远红外银河系内光子数量迅速增加,可能会发生光谱截止。因此,河外背景光中的光子仍然是费米LAT正在进行的伽马射线暴观测和地基伽马射线望远镜未来潜在探测的光子-光子不透明度的唯一相关来源。

英文摘要:

High-energy photons emitted from gamma-ray bursts (GRBs) are subject to pair-production interactions with lower energy photons, leading to an effective optical depth. In this Letter, we estimate the opacity resulting from photon fields located at various distances from long GRB sites: that of the binary companion to the massive stellar progenitor, that of the star-forming molecular cloud containing the GRB, and the total photon field of the host galaxy. The first two photon fields are found to be transparent for most reasonable sets of assumptions about these systems. In the case of galactic radiation fields, we have performed several numerical simulations to calculate the expected opacities for different line-of-sight geometries through the host galaxy, and include a full accounting of the infrared radiation produced by the absorption and re-radiation of starlight by dust. The optical depth for GeV gamma-rays, due to direct starlight is less than unity for all host galaxies. At higher energies, $>$10 TeV, a spectral cutoff can occur due to the rapidly increasing number of mid- to far-IR intra-galactic photons reradiated by dust. Photons in the extragalactic background light therefore remain the only relevant source of photon-photon opacity for ongoing GRB observations with Fermi LAT, and potential future detections with ground-based gamma-ray telescopes.

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