Radio Detection of an Elusive Millisecond Pulsar in the Globular Cluster NGC 6397

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

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) in 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 for the apparent dearth of binary neutron stars in core-collapsed GCs as well as a critical constraint on the evolution of GCs.

Additional Information

© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2022 June 16; revised 2022 July 14; accepted 2022 July 15; published 2022 July 28. This work is supported by the National Nature Science Foundation of China (NSFC) under grant Nos. 11988101, 11725313, 12103069, U2031121, U1731238, U2031117, 12041305, 12173016, 12041301, and 12121003. L.Z. is supported by ACAMAR Postdoctoral Fellowship and especially thanks Matthew Bailes and Ryan Shannon at the Swinburne University of Technology for their constructive feedback on this work. K.K. is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-2001751. Y.F. is supported by the National Key R&D Program of China No. 2017YFA0402600, and by the Key Research Project of Zhejiang Lab No. 2021PE0AC03. X.F. and Z.Y.Z acknowledge the science research grants from the China Manned Space Project with Nos. CMS-CSST-2021-A08, CMS-CSST-2021-A07, the Program for Innovative Talents Entrepreneur in Jiangsu, the China Postdoctoral Science Foundation No. 2020M670023, and the National Key R&D Program of China No. 2019YFA0405500. P.W. acknowledges support from the Youth Innovation Promotion Association CAS (id. 2021055), CAS Project for Young Scientists in Basic Research (grant YSBR-006), and the Cultivation Project for FAST Scientific Payoff and Research Achievement of CAMS-CAS. Q.J.Z. is supported by the Guizhou Provincial Science and Technology Foundation (Nos. [2016]4008, [2017]5726-37, [2018]5769-02), the Foundation of Guizhou Provincial Education Department (No. KY (2020) 003). A.R., M.K, J.B., D.J.C., P.F., P.V.P., V.V.K and W.C. acknowledge continuing valuable support from the Max-Planck Society. A.R. and M.B. gratefully acknowledge financial support by the research grant "iPeska" (P.I. Andrea Possenti) funded under the INAF national call Prin-SKA/CTA approved with the Presidential Decree 70/2016. This work is partly supported by the Pilot Project for Integrated Innovation of Science, Education and Industry of Qilu University of Technology (Shandong Academy of Sciences) under grant 2020KJC-ZD02, and the Aoshan Science and Technology Innovation Project under Grant 2018ASKJ01. Parts of this research were conducted by the Australian Research Council Centre of Excellence for Gravitational Wave Discovery (OzGrav), through project number CE170100004. The MeerKAT telescope is operated by the South African Radio Astronomy Observatory, which is a facility of the National Research Foundation, an agency of the Department of Science and Innovation. TRAPUM observations used the FBFUSE and APSUSE computing clusters for data acquisition, storage, and analysis. These clusters were funded and installed by the Max-Planck-Institut für Radioastronomie and the Max-Planck-Gesellschaft We also thank the Parkes team for their great effort to install and commission the UWL receiver system.

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