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arXiv · 1302.0610

Search for pulsed gamma-ray emission from globular cluster M28

J. H. K. Wu·C. Y. Hui·E. M. H. Wu·A. K. H. Kong·R. H. H. Huang·P. H. T. Tam·J. Takata·K. S. Cheng
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Abstract

Using the data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope, we have searched for the gamma-ray pulsations from the direction of globular cluster M28 (NGC 6626). We report the discovery of a signal with the frequency consistent with that of the energetic millisecond pulsar (MSP) PSR B1821-24 in M28. A weighted H-test test statisic (TS) of 28.8 is attained which corresponds to a chance probability of ~1e-5 (4.3-sigma detection). With a phase-resolved analysis, the pulsed component is found to contribute ~25% of the total observed gamma-ray emission from the cluster. On the other hand, the unpulsed level provides a constraint for the underlying MSP population and the fundamental plane relations for the scenario of inverse Compton scattering. Follow-up timing observations in radio/X-ray are encouraged for further investigating this periodic signal candidate.

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J. H. K. Wu, C. Y. Hui, E. M. H. Wu, A. K. H. Kong, R. H. H. Huang, P. H. T. Tam, J. Takata, K. S. Cheng. 2013-02-04. Search for pulsed gamma-ray emission from globular cluster M28. https://doi.org/10.1088/2041-8205%2F765%2F2%2Fl47

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