Radio detection of an elusive millisecond pulsar in the Globular Cluster NGC 6397

Lei Zhang; Alessandro Ridolfi; Harsha Blumer; Paulo Freire; Richard N. Manchester; Maura McLaughlin; Kyle Kremer; Andrew D. Cameron; Zhiyu Zhang; Jan Behrend; Marta Burgay; Sarah Buchner; David J. Champion; Weiwei Chen; Shi Dai; Yi Feng; Xiaoting Fu; Meng Guo; George Hobbs; Evan F. Keane; Michael Kramer; Lina Levin; Xiangdong Li; Mengmeng Ni; Jingshan Pan; Prajwal V. Padmanabh; Andrea Possenti; Scott M. Ransom; Chao-Wei Tsai; Vivek Venkatraman Krishnan; Pei Wang; Jie Zhang; Qijun Zhi; Yongkun Zhang; Di Li

doi:10.3847/2041-8213/ac81c3

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arXiv · 2207.07880

Radio detection of an elusive millisecond pulsar in the Globular Cluster NGC 6397

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Abstract

We report the discovery of a new 5.78 ms-period millisecond pulsar (MSP), PSR J1740-5340B (NGC 6397B), in an eclipsing binary system discovered with the Parkes radio telescope (now also known as Murriyang), Australia, and confirmed with the MeerKAT radio telescope in South Africa. The measured orbital period, 1.97 days, is the longest among all eclipsing binaries in globular clusters (GCs) and consistent with that of the coincident X-ray source U18, previously suggested to be a 'hidden MSP'. Our XMM-Newton observations during NGC 6397B's radio quiescent epochs detected no X-ray flares. NGC 6397B is either a transitional MSP or an eclipsing binary in its initial stage of mass transfer after the companion star left the main sequence. The discovery of NGC 6397B potentially reveals a subgroup of extremely faint and heavily obscured binary pulsars, thus providing a plausible explanation to the apparent dearth of binary neutron stars in core-collapsed GCs as well as a critical constraint on the evolution of GCs.

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Lei Zhang, Alessandro Ridolfi, Harsha Blumer, Paulo Freire, Richard N. Manchester, Maura McLaughlin, Kyle Kremer, Andrew D. Cameron, Zhiyu Zhang, Jan Behrend, Marta Burgay, Sarah Buchner, David J. Champion, Weiwei Chen, Shi Dai, Yi Feng, Xiaoting Fu, Meng Guo, George Hobbs, Evan F. Keane, Michael Kramer, Lina Levin, Xiangdong Li, Mengmeng Ni, Jingshan Pan, Prajwal V. Padmanabh, Andrea Possenti, Scott M. Ransom, Chao-Wei Tsai, Vivek Venkatraman Krishnan, Pei Wang, Jie Zhang, Qijun Zhi, Yongkun Zhang, Di Li. 2022-07-16. Radio detection of an elusive millisecond pulsar in the Globular Cluster NGC 6397. https://doi.org/10.3847/2041-8213%2Fac81c3

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