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arXiv · 1810.10651

A gamma-ray periodic modulation in Globular Cluster 47 Tucanae

Peng-Fei Zhang·Jia-Neng Zhou·Da-Hai Yan·Jing-Zhi Yan·Yi-Zhong Fan·Jun Fang·Li Zhang
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Abstract

The Globular Cluster 47 Tucanae was firstly detected in gamma-rays by the Large Area Telescope (LAT) onboard the \emph{Fermi} Gamma-ray Space Telescope, and the gamma-ray emission has been widely attributed to the millisecond pulsars. In this work, we analyze the Fermi-LAT pass 8 data ranging from 2008 August to 2017 May and report the detection of a modulation with a period of $18.416\pm0.008$ hours at a significance level of $\sim 4.8\sigma$. This is the first time to detect a significant modulation with a period much longer than that of millisecond pulsars in gamma-rays from Globular Clusters. The periodic modulation signal appears in the {\it Swift}-BAT data as well. The phase-folded Chandra X-ray light curve of a point source may have provided an additional clue.

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Peng-Fei Zhang, Jia-Neng Zhou, Da-Hai Yan, Jing-Zhi Yan, Yi-Zhong Fan, Jun Fang, Li Zhang. 2018-10-24. A gamma-ray periodic modulation in Globular Cluster 47 Tucanae. https://doi.org/10.3847/2041-8213%2Fabc7bb

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