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arXiv 1002.1563astro-ph.HE
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Cyg X-3发射sub-TeV Gamma-ray的可能性

On the possibility of sub-TeV Gamma-ray emission from Cyg X-3

W. Bednarek

摘要:

紧凑X射线双星系统Cyg X-3最近被AGILE和{ \it Fermi}卫星发现为GeV γ射线源。它在GeV伽马射线中的发射特征与其他在TeV伽马射线中也观察到的伽马射线双星(LS 5039和LSI +61 303)相似。现在的问题是,天鹅座X-3是否也能被切伦科夫望远镜在TeV伽马射线中探测到。在这里,我们详细讨论了这个问题的基础上,各向异性逆康普顿(IC)的e-p对级联模型成功地应用于TeV的伽玛射线双星。我们计算的伽玛射线光变曲线和伽玛射线光谱预期的级联过程中发生的天鹅座X-3的二元系统。结果表明,在相对论电子注入源的轨道参数合理的情况下,GeV能区的γ射线光变曲线与Fermi观测到的γ射线光变曲线是一致的。此外,我们表明,在这样一个模型中,亚TeV的伽马射线发射(100 GeV以上)预计将低于目前切伦科夫望远镜的灵敏度,假设电子在天鹅座X-3 TeV的能量加速。下一阶段切伦科夫望远镜(MAGIC II,HESS II)的能量阈值应该在20-30 GeV范围内,以便有机会探测到来自天鹅座X-3的信号。否则,要探测到能量在几十GeV以上的伽马射线,需要一台灵敏度为蟹状单位的0.1%的望远镜。我们的结论是,地面望远镜对天鹅座X-3的亚TeV伽马射线的探测可能要等待切伦科夫望远镜阵列(CTA)的建设。

英文摘要:

The compact X-ray binary system Cyg X-3 has been recently discovered as a source of GeV gamma-rays by the AGILE and the {\it Fermi} satellites. It shows emission features in the GeV gamma-rays similar to other gamma-ray binaries which were also observed in the TeV gamma-rays (LS 5039 and LSI +61 303). The question appears whether Cyg X-3 can be also detected in the TeV gamma-rays by the Cherenkov telescopes. Here we discuss this problem in detail based on the anisotropic inverse Compton (IC) e-p pair cascade model successfully applied to TeV gamma-ray binaries. We calculate the gamma-ray light curves and gamma-ray spectra expected from the cascade process occurring inside the Cyg X-3 binary system. It is found that the gamma-ray light curves at GeV energies can be consistent with the gamma-ray light curve observed by the Fermi for reasonable parameters of the orbit of the injection source of relativistic electrons. Moreover, we show that in such a model the sub-TeV gamma-ray emission (above 100 GeV) is expected to be below sensitivities of the present Cherenkov telescopes assuming that electrons are accelerated in Cyg X-3 to TeV energies. The next stage Cherenkov telescopes (MAGIC II, HESS II) should have the energy threshold in the range 20-30 GeV, in order to have a chance to detect the signal from Cyg X-3. Otherwise, the positive detection of gamma-rays at energies above a few tens of GeV requires a telescope with the sensitivity of ~0.1% of Crab Units. We conclude that detection of sub-TeV gamma-rays from Cyg X-3 by on-ground telescopes has to probably wait for construction of the Cherenkov Telescope Array (CTA).

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