人马座A*中磁彭罗斯过程产生的加速质子
Accelerated protons produced by magnetic Penrose process in Sgr A*
AI总结：
本研究提出Sgr A*的辐射低效吸积流产生的中子经磁彭罗斯过程加速为高能质子，计算其地球伽马射线和质子通量，解释部分甚高能观测结果，并明确模型适用的黑洞质量上限。
摘要：
从旋转黑洞提取能量的典型机制是Blandford-Znajek过程和彭罗斯过程。彭罗斯过程需要一种在常见天体物理环境中难以出现的特殊条件。然而，磁彭罗斯过程（magnetic Penrose process，MPP）不需要这种特殊条件，并且能够产生超高能宇宙线。当中子在旋转黑洞附近衰变时，所产生质子的MPP效率达到最高。人马座A*（Sagittarius A*，Sgr A*）中的超大质量黑洞很可能存在辐射低效吸积流，其温度足够高，可通过核反应产生中子，这些中子随后可通过MPP被加速到高能。我们计算了来自Sgr A*的加速质子的产生率，以估算这些加速质子在地球产生的伽马射线通量，以及从Sgr A*传输到地球的加速质子自身的通量。我们发现，这些甚高能伽马射线（$E_γ\boldmath{\raisebox{0.5em}{$\textstyle>$}\raisebox{-0.3em}{$\textstyle\backsim$}}10\textrm{ TeV}$）在约100 TeV能量下，占HESS J1745-290及中心分子区伽马射线通量的很大一部分。当无量纲自旋参数$a_{*}=0.5$且黑洞附近的磁场强度$B_{0}=100\textrm{ G}$时，加速质子通量约为KASCADE实验在约1 PeV处测得的宇宙线质子通量的1.6-4.1%。由于中子需要从吸积流传输到加速区，而中子的衰变时间有限，我们的加速模型仅能在质量不超过约$10^8 M_\textrm{☉}$的黑洞周围运行。
英文摘要：
Typical mechanisms to extract energies from a rotating black hole are the Blandford-Znajek process and the Penrose process. The Penrose process requires a special condition that is difficult to occur in common astrophysical situations. However, the magnetic Penrose process (MPP) does not require such a special condition, and can produce ultra-high energy cosmic rays. When neutrons decay near a rotating black hole, the MPP efficiency of the produced proton is maximized. The supermassive black hole in Sagittarius A* (Sgr A*) is likely to have a radiatively inefficient accretion flow that is hot enough to produce neutrons by nuclear reactions, which can be subsequently accelerated to high-energy by the MPP. We calculate the production rate of accelerated protons from the Sgr A* to estimated the gamma-ray flux at Earth produced by these accelerated protons and the flux of the accelerated protons themselves transported from Sgr A* to Earth. We find that these very high-energy gamma rays ($E_γ\gtrsim10\,\mathrm{TeV}$) amount to a significant fraction of the flux of the gamma-ray from the HESS J1745-290 and the central molecular zone around $100\,\mathrm{TeV}$. The accelerated proton flux, when the dimensionless spin parameter $a_{*}=0.5$ and the magnetic field strength in the vicinity of the black hole $B_{0}=100\,\mathrm{G}$, is about $1.6-4.1\%$ of the cosmic ray proton flux from KASCADE experiment at about $1\,\mathrm{PeV}$. Due to the finite decay time of neutrons which need to be transported from the accretion flow to the acceleration zone, our acceleration model can operate only around black holes with mass not much greater than $\sim10^8\,M_\odot$.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
