Abstract
Several long-period radio transients have recently been discovered, with strongly polarized coherent radio pulses appearing on timescales between tens to thousands of seconds1,2. In some cases, the radio pulses have been interpreted as coming from rotating neutron stars with extremely strong magnetic fields, known as magnetars; the origin of other, occasionally periodic and less-well-sampled radio transients is still debated3. Coherent periodic radio emission is usually explained by rotating dipolar magnetic fields and pair-production mechanisms, but such models do not easily predict radio emission from such slowly rotating neutron stars and maintain it for extended times. On the other hand, highly magnetic isolated white dwarfs would be expected to have long spin periodicities, but periodic coherent radio emission has not yet been directly detected from these sources. Here we report observations of a long-period (21 min) radio transient, which we have labelled GPM J1839–10. The pulses vary in brightness by two orders of magnitude, last between 30 and 300 s and have quasiperiodic substructure. The observations prompted a search of radio archives and we found that the source has been repeating since at least 1988. The archival data enabled constraint of the period derivative to <3.6 × 10−13 s s−1, which is at the very limit of any classical theoretical model that predicts dipolar radio emission from an isolated neutron star.
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Data availability
Data that support this paper are available at the following public repository: https://github.com/nhurleywalker/GPMTransient. Further data products can be supplied by the authors on request; raw data can be obtained from the observatory archives through their data portals (see Methods).
Code availability
Code that supports this paper is available at the following public repository: https://github.com/nhurleywalker/GPMTransient.
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Acknowledgements
This scientific work uses data obtained from Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio-astronomy Observatory. We acknowledge the Wajarri Yamaji people as the Traditional Owners and native title holders of the observatory site. The ASKAP, the ATCA and Parkes/Murriyang are part of the Australia Telescope National Facility (https://ror.org/05qajvd42), which is managed by CSIRO. Operation of ASKAP is financed by the Australian Government, with support from the National Collaborative Research Infrastructure Strategy. ASKAP uses the resources of the Pawsey Supercomputing Centre. Establishment of ASKAP, the Murchison Radio-astronomy Observatory and the Pawsey Supercomputing Centre are initiatives of the Australian Government, with support from the Government of Western Australia and the Science and Industry Endowment Fund. We acknowledge the Gomeroi people as the Traditional Owners of the ATCA observatory site and the Wiradjuri people as the Traditional Owners of the Parkes observatory site. Support for the operation of the MWA is provided by the Australian Government (NCRIS), under a contract to Curtin University administered by Astronomy Australia Limited. The authors would like to thank the South African Radio Astronomy Observatory for the approval of the MeerKAT DDT request. 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). These observations used the FBFUSE and APSUSE computing clusters for data acquisition, storage and analysis. These clusters were financed and installed by the Max-Planck-Institut für Radioastronomie (MPIfR) and the Max-Planck-Gesellschaft. Breakthrough Listen is managed by the Breakthrough Initiatives, sponsored by the Breakthrough Prize Foundation. The GMRT is run by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This project was supported by resources and expertise provided by CSIRO IMT Scientific Computing. Basic research in radio astronomy at the U.S. Naval Research Laboratory is supported by 6.1 base funding. Construction and installation of VLITE was supported by the NRL Sustainment Restoration and Maintenance fund. This research is based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly financed by ESA Member States and NASA. We thank N. Schartel for approving our DDT request and the XMM-Newton Science Operations Centre for carrying out the observation. This research is also based on observations made with the GTC, installed at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias (IAC) on the island of La Palma, under DDT (code GTC03-22BDDT). The EMIR project is led by the IAC with the participation of the Laboratoire d’Astrophysique - Observatoire Midi-Pyrenees (France), Universidad Complutense de Madrid and the Laboratoire d’Astrophysique - Observatoire de Marselle (France). We acknowledge the GTC Director, A. Cabrera, for accepting our DDT request, and thank him, N. García and T. Muñoz-Darias for the useful insights on EMIR data analysis. We would like to thank V. Morello for valuable input on the timing results, A. Harding, R. Turolla and J. Pons for discussion about pulsar magnetospheres, C. Pardo, M. Ronchi, V. Graber and A. Ibrahim for useful discussions on death lines and M. Sokolowski and C. Trott for commenting on the manuscript as part of the MWA Collaboration review. N.H.-W. is the recipient of an Australian Research Council (ARC) Future Fellowship (project number FT190100231). N.R. is supported by the European Research Council (ERC) through the Consolidator Grant ‘MAGNESIA’ under grant agreement no. 817661. F.C.Z. is supported by a Ramon y Cajal Fellowship (grant agreement RYC2021-030888-I). N.R. and F.C.Z. are partially supported by the programme Unidad de Excelencia María de Maeztu CEX2020-001058-M. G.E.A. is the recipient of an ARC Discovery Early Career Researcher Award (project number DE180100346). M.C. acknowledges support of an ARC Discovery Early Career Research Award (project number DE220100819) funded by the Australian Government and the ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013. D.d.M. acknowledges financial support from the Italian Space Agency (ASI) and National Institute for Astrophysics (INAF). B.S. acknowledges funding from the ERC under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 694745). K.M.R. acknowledges support from the Vici research programme ‘ARGO’ with project number 639.043.815, financed by the Dutch Research Council (NWO).
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Contributions
N.H.-W. led the radio proposals, calibrated and processed the MWA and MeerKAT continuum observations, made the initial detection of the source, determined its position and flux density in the MWA, MeerKAT, ASKAP, Parkes, and ATCA data, performed the timing error analysis and prepared the manuscript, with contributions from all co-authors. N.R. led the XMM and GTC proposals and preliminary analysis and contributed theoretical interpretation. S.J.M. performed the de-dispersive and barycentric corrections and integrated the radio flux density spectrum. B.W.M. performed the timing analysis. E.L. performed the ASKAP data reduction, MWA polarization analysis and, jointly with I.H., the MeerKAT polarization analysis. S.D.H. and S.G. performed the GMRT and VLA pre-2016 archival searches. Y.P.M., K.M.R. and E.D.B. analysed the MeerKAT PTUSE and APSUSE data, determining the DM and RM. T.E.C. and S.G. performed the VLITE archive search and imaging. F.C.Z. contributed to the XMM and GTC proposals, performed the XMM analysis and wrote the corresponding text and, with N.R., D.d.M. and M.D., analysed the GTC data. D.C.P. and N.D.R.B. conducted the Parkes observing and analysis. C.H. helped develop the filtering and transient source-finding that enabled the detection of the source, with supervision and further code contributions by N.H.-W., T.J.G. and J.S.M. G.E.A. and T.J.G. performed the ATCA observations and analysis. A.B. contributed archival X-ray and optical searches. M.C., K.M.R. and B.S. assisted with the planning, analysis and interpretation of the high-time-resolution MeerKAT data. A.W. performed the MWA observing.
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Extended data figures and tables
Extended Data Fig. 1 3σ upper limits on the persistent X-ray luminosity at the position of GPM J1839–10 as a function of the assumed spectral shape.
The shaded region is for distances in the 3–8-kpc range.
Extended Data Fig. 2 Simultaneous radio (ASKAP) and X-ray (XMM-Newton) observations of two bright radio pulses detected on 14 September 2022.
The dotted line is the 3σ upper limit on the net count rate derived considering the whole observation (see Methods).
Extended Data Fig. 3 GTC EMIR image of the field around GPM J1839–10 in the Ks band.
The black circle represents the source positional error of 0.15″.
Extended Data Fig. 4 The explored search space in f and \(\mathop{{\boldsymbol{f}}}\limits^{{\boldsymbol{.}}}\) for the pulses recorded from GPM J1839–10.
Contours show the confidence intervals derived from the timing analysis (see Methods). The reduced χ2 values are shown in greyscale. The central marker shows the best-fit f = 0.000758612(7) Hz and \(\mathop{f}\limits^{^\circ }=5\times 1{0}^{-20}\). The arrow markers show limits on \(\mathop{f}\limits^{.}\); the 1σ limit is shown as an upper limit on \(\mathop{P}\limits^{.}\) in Fig. 4.
Extended Data Fig. 5 The RM synthesis results of two bursts in the first two pulses detected by MeerKAT, at 19:12:33 and 19:35:43 UTC 20 July 2022.
The vertical shaded area represents the measured errors of the RMs. The RM estimations derived by the plot in two periods are −531.83 ± 0.14 and −532.2 ± 2.2 rad m−2, respectively.
Extended Data Fig. 6 The polarization profile of a 30-ms burst observed with MeerKAT PTUSE. The RM is −531 rad m−2.
The top panel shows the measurements of the PA at different pulse phases. The middle panel shows the total, linearly polarized and circularly polarized flux densities as a function of time, represented by the black, red and blue lines, respectively. The bottom panel shows the dynamic spectrum of the burst. The start time of the plot is 19:35:43.228133 UTC 20 July 2022. The apparent steep spectrum is not intrinsic to the source but because of the misalignment of the coherent beam.
Extended Data Fig. 7 Dynamic spectrum of the 19:12:33 20 July 2022 pulse detected with the APSUSE instrument on MeerKAT.
The time resolution is 3.9 ms and the frequency resolution is 8.5 MHz. Strong interference signals have been removed in the 950-MHz band and at the band edges below 577 MHz and above 1,065 MHz. The data are shown before de-dispersion (a) and after de-dispersion (b).
Extended Data Fig. 8 Autocorrelation (lag) analysis of three high-S/N pulses observed with the MWA (left and right panels) and MeerKAT (middle panel).
The top row shows the de-dispersed, frequency-integrated light curves as a function of time from the start of each observation, shown in the panel titles. The light curves have been normalized for readability; observational parameters, peak flux densities and fluences for these pulses are reported in Supplementary Table 1. The bottom row shows the autocorrelations over the range of timescales well sampled by each light curve. To indicate the range of observed behaviours, some of the lag peaks are marked with vertical grey lines.
Supplementary information
Individual pulse statistics
For pulses split across several observations, only a single (dedispersed, barycentred) time of arrival is given, which is used in the timing analysis. Peak flux densities are the maxima observed in a given light curve. Fluences are calculated by multiplying the light curve by the sample time; for faint pulses in which the light curves are dominated by noise, only flux densities >3σ are used. Flux densities and fluences are also shown scaled to a common frequency of 1 GHz using equation (1) in Methods.
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Hurley-Walker, N., Rea, N., McSweeney, S.J. et al. A long-period radio transient active for three decades. Nature 619, 487–490 (2023). https://doi.org/10.1038/s41586-023-06202-5
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DOI: https://doi.org/10.1038/s41586-023-06202-5
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