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    马普核物理研究所、都柏林高等研究所Felix Aharonian教授的点评

    发布时间:2021-05-24
       Felix Aharonian(德国)

      国际著名粒子天体物理学家,马普核物理研究所、都柏林高等研究所教授 

    [video:Felix Aharonian专家点评]

      Over the last two decades, we have seen two revolutions in gamma-ray astronomy: (i) in GeV energy band thanks to the Fermi gamma-ray satellite mission and (ii) at TeV energies after the exploitation of the full potential of the so-called Imaging Atmospheric Cherenkov technique.  

      These days we are witnessing a new revolution, this time in the UHE, above 100 TeV, band. One can predict with confidence that for the next ten years (at least), LHAASO will dominate in the field and play the major role in the upcoming developments. This is for future.  

      For the results presented in the published Nature article - we claim the first unbiased and unambiguous discovery of both electron and proton PeVatrons. These are perfectly designed by Nature Cosmic Ray Factories - incredibly efficient machines accelerating particles at a rate close to the absolute theoretical margin determined by the classical electrodynamics and magnetohydrodynamics. At least one source from the published list - Crab Nebula - operates as an Electron PeVatron, and at least one source - Cygnus Cocoon - is powered by a Proton PeVatron. The gamma-ray spectra of both objects continue to and beyond 1 PeV.  

      Cygnus Cocoon has direct relation to the century-old mystery of the origin of Galactic Cosmic Rays. The famous Cygnus OB stellar cluster inside this diffuse gamma-ray structure is the most likely accelerator supplying Cygnus Cocoon with multi-PeV protons. On the other hand, we do not see in the LHAASO list sources that could be firmly identified with SNRs. This still does not exclude but shakes the standard paradigm which assumes that SNRs are the main contributors to the Galactic Cosmic Rays up to the so-called knee around 1 PeV. On the other hand, the LHAASO results provide a hint that clusters of young, very-massive stars should be considered a serious alternative or addition to SNRs. Moreover, using the chess language, I would say that in the PeVatron competition “young stars versus dead stars”, the score is 1:0 in favour of young stars.  

      Finally, let me conclude with a statement that the results reported in the Nature article reveal only the tip of the iceberg. In the coming years, we anticipate breakthrough discoveries by LHAASO that could dramatically change the current concepts about the most energetic and extreme phenomena in the non-thermal Universe. 

      在过去的二十年多中,伽马射线天文学经历了两次革新:其一在GeV能量段由Fermi-LAT伽马射线卫星所带来,其二在TeV能量段藉由对成像大气切伦科夫望远镜潜力的最大化利用而产生。如今,我们正在见证另一场发生在超高能量段(100TeV之上)的革新。人们可以信心十足地预测,在未来至少十年的时间里,LHAASO将在伽马射线天文学领域鳌头独占,并在该领域未来的发展中发挥主要作用。 

      LHAASO团队在《自然》杂志上发表的这篇最新论文里,首次报导了对PeV电子加速源与PeV质子加速源客观且明确的探测。这些完美的宇宙线工厂诞生于宇宙的鬼斧神工。它们加速粒子的效率惊人,直逼由经典电动力学与磁流体力学决定的绝对理论上限。在发布的加速源列表中,可以确认其中至少有一个天体——蟹状星云——作为PeV电子加速器在运行,也至少有一个天体——天鹅座茧——PeV质子加速器供能。这两个天体的伽马射线能谱都延续到了1 PeV之上。 

        

      天鹅座茧与银河宇宙线起源这个物理学界的世纪谜题有着直接关联。位于这团弥散伽马射线结构体中心的天鹅座OB星团是最有可能的PeV宇宙线质子加速器。另一方面,超新星遗迹却未明确见于LHAASO发布的源表之中。这动摇了——尽管仍能未排除——超新星遗迹作为银河系中能量上至所谓膝区的PeV宇宙线的主要加速源的标准范式。同时,LHAASO也带来了年轻大质量恒星团作为超新星遗迹的替代或补充的新线索。若以国际象棋的术语来说,在这场年轻恒星对死亡恒星的较量中,年轻恒星正以10领先。 

        

      作为总结,我想说这篇《自然》上的论文揭开的仅仅是冰山一角。我们期待在未来几年,LHAASO的突破性发现可能会使得我们目前对非热宇宙中那些最活跃最极端现象的观念发生极大的改变。   

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