The emission of interpulses by a 6.45-h-period coherent radio transient

Creators: Lee, Y. W. J.^{1, 2, 3}; Caleb, M.^{1, 2}; Murphy, Tara^{1, 2}; Lenc, E.³; Kaplan, D. L.⁴; Ferrario, L.⁵; Wadiasingh, Z.^{6, 7, 8}; Anumarlapudi, A.⁴; Hurley-Walker, N.⁹; Karambelkar, V.¹⁰; Ocker, S. K.^{10, 11}; McSweeney, S.⁹; Qiu, H.¹²; Rajwade, K. M.¹³; Zic, A.³; Bannister, K. W.³; Bhat, N. D. R.⁹; Deller, A.^{2, 14}; Dobie, D.^{1, 2}; Driessen, L. N.¹; Gendreau, K.⁷; Glowacki, M.⁹; Gupta, V.³; Jahns-Schindler, J. N.¹⁴; Jaini, A.¹⁴; James, C. W.⁹; Kasliwal, M. M.¹⁰; Lower, M. E.³; Shannon, R. M.^{2, 14}; Uttarkar, P. A.¹⁴; Wang, Y.¹⁴; Wang, Z.⁹

1. University of Sydney
2. ARC Centre of Excellence for Gravitational Wave Discovery
3. Australia Telescope National Facility
4. University of Wisconsin–Milwaukee
5. Australian National University
6. University of Maryland, College Park
7. Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD, USA
8. Goddard Space Flight Center
9. International Centre for Radio Astronomy Research
10. California Institute of Technology
11. Carnegie Science Observatories, Pasadena, CA, USA
12. Square Kilometre Array Organisation
13. University of Oxford
14. Swinburne University of Technology

Abstract

Long-period radio transients are a new class of astronomical objects characterized by prolonged periods ranging from 18 min to 54 min. They exhibit highly polarized, coherent, beamed radio emission lasting only 10–100 s. The intrinsic nature of these objects is subject to speculation, with highly magnetized white dwarfs and neutron stars being the prevailing candidates. Here we present ASKAP J183950.5−075635.0, boasting the longest known period of this class at 6.45 h. It exhibits emission characteristics of an ordered dipolar magnetic field, with pulsar-like bright main pulses and weaker interpulses offset by about half a period that are indicative of an oblique or orthogonal rotator. This phenomenon, observed in a long-period radio transient, confirms that the radio emission originates from both magnetic poles and that the observed period corresponds to the rotation period. The spectroscopic and polarimetric properties of ASKAP J183950.5−075635.0 are consistent with a neutron star origin, and this object is a crucial piece of evidence in our understanding of long-period radio sources and their links to neutron stars.

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Acknowledgement

We acknowledge M. Bailes and L. Spitler as co-principal investigators (co-PIs) of the CRACO LIEF grant LE210100107. We thank M. Bailes for supporting the PTUSE backend machine used in the MeerKAT observation. We also thank Z. Arzoumanian and the NICER team for their assistance in conducting X-ray observations. We are grateful to the ASKAP engineering and operations team for their assistance in supporting the observations. This scientific work uses data obtained from Inyarrimanha Ilgari Bundara/the Murchison Radio-astronomy Observatory. We acknowledge the Wajarri Yamaji People as the Traditional Owners and native title holders of the Observatory site. CSIRO’s ASKAP radio telescope is part of the Australia Telescope National Facility (https://ror.org/05qajvd42). Operation of ASKAP is funded by the Australian Government with support from the National Collaborative Research Infrastructure Strategy. ASKAP uses the resources of the Pawsey Supercomputing Research Centre. Establishment of ASKAP, Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio-astronomy Observatory and the Pawsey Supercomputing Research Centre are initiatives of the Australian Government, with support from the Government of Western Australia and the Science and Industry Endowment Fund. This manuscript makes use of data from MeerKAT (Project ID: DDT-20240209-JL-01) and ATCA (Project ID: C3363). We thank SARAO for the approval of the MeerKAT DDT request and the science operations and CAM/CBF and operator teams for their time and effort invested in the observations. 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 (DSI). This scientific work uses data obtained from telescopes within the Australia Telescope National Facility (https://ror.org/05qajvd42), which is funded by the Australian Government for operation as a National Facility managed by CSIRO. PTUSE was developed with support from the Australian SKA Office and Swinburne University of Technology. This work made use of the NASA Astrophysics Data System. T.M., Y.W.J.L., J.N.J.S., A.D. and R.M.S. acknowledge funding from the Australian Research Council Discovery Project DP 220102305. M.C. acknowledges support of an Australian Research Council Discovery Early Career Research Award (project no. DE220100819) funded by the Australian Government. D.L.K. is supported by NSF grant no. AST-1816492. Z.W. acknowledges support by NASA under award no. 80GSFC21M0002. Parts of this research were conducted by the Australian Research Council Centre of Excellence for Gravitational Wave Discovery (OzGrav), project no. CE230100016. R.M.S. and N.H.W. acknowledge support through Australian Research Council Future Fellowships FT190100155 and FT190100231, respectively. M.G. and C.W.J. acknowledge support through the Australian Research Council’s Discovery Projects funding scheme (DP210102103). The development of the CRACO system has been supported through Australian Research Council Linkage Infrastructure Equipment and Facilities grant no. LE210100107.

Contributions

Y.W.J.L. and M.C. drafted the manuscript with suggestions from co-authors and were the PIs of the MeerKAT data. Y.W.J.L. reduced and analysed the MeerKAT imaging data and the ATCA data, analysed the ASKAP data and performed astrometry on the source. M.C. reduced the MeerKAT PTUSE data with Y.W.J.L. E.L. calibrated and reduced the ASKAP data. D.L.K. and S.M. conducted pulsar timing on the source. D.L.K. performed the Pan-STARRS and VPHAS+ archive search. T.M., L.F., Z.W. and N.H.W. contributed to discussions about the nature and emission mechanism of the source. A.A. performed the ASKAP and VLA archival searches and analyses. N.H.W. reduced the MWA data and analysed the spectral index. V.K. and M.M.K. performed the WIRC observation and calibrated the data. S.O. performed the FourStar camera observation and calibrated the data. H.Q. performed the Swift observation and analysed the data. K.M.R. and K.G. performed the NICER observation and analysed the data. A.Z. and M.E.L. analysed the rotation measure of the source. K.W.B., A.D., C.J. and R.M.S. were the PIs of CRACO. M.G., V.G., J.N.J.S., A.J., Y.W.J.L., P.U., Y.W. and Z.W. were the builders of CRACO. T.M. was the PI of the ATCA project no. C3363. T.M. and D.L.K. were the PIs of VAST, and D.D. and L.D. were the project scientists of VAST. The PIs and builders of VAST and CRACO coordinated the initial investigation of ASKAP J1839−0756.

Data Availability

The data that support the findings of this study are available via Zenodo at https://doi.org/10.5281/zenodo.14043008 (ref. ⁹¹). All the ASKAP data are publicly available at CASDA (https://research.csiro.au/casda/). The MeerKAT data used in this study are available via the SARAO archive (https://archive.sarao.ac.za) under project ID DDT-20240209-JL-01. The ATCA data used in this study are available via the Australia Telescope Online Archive (https://atoa.atnf.csiro.au/) under project ID C3363.

Code Availability

The timing was performed using TEMPO2 (ref. ⁹²) and PINT⁷. Specific Python scripts used in the data analysis are available on request from Y.W.J.L. and M.C.

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