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arXiv 2007.04627astro-ph.HE
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SNR G39 .2-0.3强子宇宙射线加速器

SNR G39.2-0.3, an Hadronic Cosmic Rays Accelerator

Emma de Ona Wilhelmi, Iurii Sushch, Robert Brose, Enrique Mestre, Yang Su, Roberta Zanin

摘要:

最近用伽马射线卫星获得的结果已经证实超新星遗迹是GeV强子宇宙射线的加速器。在这样的过程中,在SNR冲击中加速的CR与周围气体云中的粒子相互作用。特别是,核心坍缩SNR爆炸的丰富介质提供了一个大的目标密度来增强强子伽马射线。SNR G39.2-0.3是红外波段中最亮的SNR之一,其广泛的多波长覆盖范围允许对其从无线电到高能量的辐射进行详细建模。我们重新分析了该地区的费米-LAT数据,并将其与MWISP调查的新无线电观测结果进行了比较。从无线电到GeV能量的光谱能量分布的建模有利于伽马射线发射的强子起源,并将SNR磁场约束为至少~100 μ G。尽管有很大的磁场,目前质子的加速度似乎被限制在~10 GeV,这表明由于CO观测所追踪到的致密壁,围绕残骸的冲击波速度急剧减慢。对伽马射线谱形状的进一步研究表明,一个动力学上古老的遗迹遭受了严重的CR逃逸和加速效率的降低。伽马射线谱的低能峰也表明,加速粒子的成分可能被重核富集,这肯定是核心塌陷SNR所预期的。另外,压缩的预先存在的银河系宇宙射线的贡献进行了讨论,这是,然而,发现不太可能是伽马射线生产的主导过程。

英文摘要:

Recent results obtained with gamma-ray satellites have established supernova remnants as accelerators of GeV hadronic cosmic rays. In such processes, CRs accelerated in SNR shocks interact with particles from gas clouds in their surrounding. In particular, the rich medium in which core-collapse SNRs explode provides a large target density to boost hadronic gamma-rays. SNR G39.2-0.3 is one of the brightest SNR in infrared wavelengths, and its broad multiwavelength coverage allows detailed modelling of its radiation from radio to high energies. We reanalyzed the Fermi-LAT data on this region and compare it with new radio observations from the MWISP survey. The modelling of the spectral energy distribution from radio to GeV energies favors a hadronic origin of the gamma-ray emission and constrains the SNR magnetic field to be at least ~100 uG. Despite the large magnetic field, the present acceleration of protons seems to be limited to ~10 GeV, which points to a drastic slow down of the shock velocity due to the dense wall traced by the CO observations, surrounding the remnant. Further investigation of the gamma-ray spectral shape points to a dynamically old remnant subjected to severe escape of CRs and a decrease of acceleration efficiency. The low-energy peak of the gamma-ray spectrum also suggests that that the composition of accelerated particles might be enriched by heavy nuclei which is certainly expected for a core-collapse SNR. Alternatively, the contribution of the compressed pre-existing Galactic cosmic rays is discussed, which is, however, found to not likely be the dominant process for gamma-ray production.

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