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تسجيل مستخدم جديدDetection of gamma-ray emission from globular clusters M 15, NGC 6397, NGC 5904, NGC 6218 and NGC 6139 with Fermi-LAT
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In the third Fermi catalogue (3FGL) there are sixteen gamma-ray globular clusters. After analyzing the recent released Pass 8 data of Fermi Large Area Telescope (LAT), we report the discovery of significant gamma-ray emission from M 15 and NGC 6397, confirm that NGC 5904 is a gamma-ray emitter and find evidence of gamma-ray emission from NGC 6218 and NGC 6139. Inter- estingly, in the globular clusters M 15, NGC 6397 and NGC 5904, millisecond pulsars (MSPs) have been found in radio or X-rays, which are strongly in support of the MSP origin of the gamma-ray emission. However, due to the relative low luminosity of the gamma-ray emission we do not find any evidence for the gamma-ray pulsation or flux variability of these sources.
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Convergent lines of evidence suggest that globular clusters host multiple stellar populations. It appears that they experience at least two episodes of star formation whereby a fraction of first-generation stars contribute astrated ejecta to form the
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