The Fermi Bubble as a source of cosmic rays in the energy range >10 15eV

Please use this identifier to cite or link to this item: https://ir.lib.ncu.edu.tw/handle/987654321/100699

Title:	The Fermi Bubble as a source of cosmic rays in the energy range >10 15eV
Authors:	葉永烜;Cheng, K.-S.;Chernyshov, D. O.;Dogiel, V. A.;Ko, C.-M.;Wang, Y.;Ip, W.-H.
Contributors:	理學院天文研究所
Keywords:	ACCELERATION;ASTROPHYSICS, COSMOLOGY AND ASTRONOMY;BLACK HOLES;COSMIC RADIATION;GALAXIES;GAMMA RADIATION;HOT PLASMA;SHOCK WAVES;STARS;STOCHASTIC PROCESSES;SUPERNOVA REMNANTS;TELESCOPES
Date:	2012-02-20
Issue Date:	2026-04-21 14:11:00 (UTC+8)
Publisher:	IOP Publishing Ltd.;United States
Abstract:	摘要： The Fermi Large Area Telescope has recently discovered two giant gamma-ray bubbles that extend north and south of the Galactic center with diameters and heights of the order of H {approx} 10 kpc. We suggest that the periodic star capture processes by the Galactic supermassive black hole Sgr A*, with a capture rate of {tau}{sup -1}{sub cap} {approx} 3 Multiplication-Sign 10{sup -5} yr{sup -1} and an energy release of W {approx} 3 Multiplication-Sign 10{sup 52} erg per capture, can result in hot plasma injecting into the Galactic halo at a wind velocity of u {approx} 10{sup 8} cm s{sup -1}. The periodic injection of hot plasma can produce a series of shocks. Energetic protons in the bubble are re-accelerated when they interact with these shocks. We show that for energy larger than E > 10{sup 15} eV, the acceleration process can be better described by the stochastic second-order Fermi acceleration. We propose that hadronic cosmic rays (CRs) within the 'knee' of the observed CR spectrum are produced by Galactic supernova remnants distributed in the Galactic disk. Re-acceleration of these particles in the Fermi Bubble produces CRs beyond the knee. With a mean CR diffusion coefficient in this energy range in the bubble D{sub B} {approx} 3 Multiplication-Sign 10{sup 30} cm{sup 2} s{sup -1}, we can reproduce the spectral index of the spectrum beyond the knee and within it. The conversion efficiency from shock energy of the bubble into CR energy is about 10%. This model provides a natural explanation of the observed CR flux, spectral indices, and matching of spectra at the knee. 出版者： United States 出版日期： 2012-02-20 出處： The Astrophysical journal, 2012-02, Vol.746 (2) 資源來源： Institute of Physics Journals 識別號： ISSN: 0004-637X 識別號： EISSN: 1538-4357 識別號： DOI: 10.1088/0004-637X/746/2/116
Appears in Collections:	[Graduate Institute of Astronomy] journal & Dissertation

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