Abstract
The radio-emitting neutron star population encompasses objects with spin periods ranging from milliseconds to tens of seconds. As they age and spin more slowly, their radio emission is expected to cease. We present the discovery of an ultra-long-period radio-emitting neutron star, PSR J0901-4046, with spin properties distinct from the known spin- and magnetic-decay-powered neutron stars. With a spin period of 75.88 s, a characteristic age of 5.3 Myr and a narrow pulse duty cycle, it is uncertain how its radio emission is generated and challenges our current understanding of how these systems evolve. The radio emission has unique spectro-temporal properties, such as quasi-periodicity and partial nulling, that provide important clues to the emission mechanism. Detecting similar sources is observationally challenging, which implies a larger undetected population. Our discovery establishes the existence of ultra-long-period neutron stars, suggesting a possible connection to the evolution of highly magnetized neutron stars, ultra-long-period magnetars and fast radio bursts.
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Data availability
The data that support the findings of this study are available at https://github.com/manishacaleb/MKT-J0901-4046.
Code availability
All code necessary for analyses of the data are available on GitHub (https://github.com/IanHeywood/oxkat) and Zenodo (https://doi.org/10.5281/zenodo.1212487).
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Acknowledgements
This manuscript makes use of MeerKAT (Project ID: DDT-20210125-MC-01) and Parkes (Project ID: PX071) data. M.C. thanks South African Radio Astronomy Observatory (SARAO) for the approval of the MeerKAT DDT request and the science operations, Control and Monitoring/Central BeamFormer (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. The Parkes Radio Telescope (Murriyang) is managed by CSIRO. We acknowledge the Wiradjuri people as the traditional owners of the Parkes observatory site. M.C. thanks the Australia Telescope National Facility (ATNF) for scheduling observations with the Parkes radio telescope. The SALT observations were obtained under the SALT Large Science Programme on transients (2018-2-LSP-001; PI: D.B.), which is also supported by Poland under grant no. MNiSW DIR/WK/2016/07. M.C., B.W.S., K.R., M.M., V.M., S.S., F.J., M.S., L.N.D and M.C.B. acknowledge funding from the European Research Council under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 694745). M.C. acknowledges support of an Australian Research Council Discovery Early Career Research Award (project number DE220100819) funded by the Australian Government and the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions, through project number CE170100013. K.R. acknowledges support from the Vici research programme ‘ARGO’ with project number 639.043.815, financed by the Dutch Research Council. J.v.d.E. is supported by a Lee Hysan Junior Research Fellowship awarded by St. Hilda’s College, Oxford. D.B. and P. Woudt acknowledge research support from the National Research Foundation.
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M.C. and B.W.S. drafted the manuscript with suggestions from co-authors. M.C. is the PI of the MeerKAT DDT and Parkes data. B.W.S. is the PI of the MeerTRAP data and R.F. and P.Woudt are the PIs of the ThunderKAT data. M.C. reduced and analysed the radio time domain data for quasi-periodicity and M.C. and M.K. interpreted it. I.H. calibrated, imaged and performed astrometry on the data to localize the source. B.W.S., V.M. and F.J. undertook the timing analyses. E.B. and K.R. designed and built the complex channelized data capture system. K.R. and P. Weltevrede performed the polarization analyses. M.M. carried out the pulse-width analyses using the wavelet transform method. E.B. and W.C. built and designed the beamformer used by MeerTRAP. J.v.d.E. and S.E.M. performed the Swift analysis. D.B., J.B. and P.Woudt obtained and analysed data from the SALT and South African Astronomical Observatory 1-m telescopes. F.J. and M.S. undertook analysis of the extant data. S.B. assisted in planning and scheduling the MeerKAT observations. S.S., F.J., M.S., R.F., L.N.D. and M.C.B contributed to discussions about the nature of the source.
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Extended data
Extended Data Fig. 1 Timing residuals of PSR J0901 − 4046.
The residuals from the best fit timing model given in Table 1. The orange data points are determined from the original MeerTRAP detection images, the first red diamond corresponds to a single pulse and the remaining red diamonds are determined from each of the half hour long follow-up observations with MeerKAT. The error bars are 1-σ. We used the L-band MeerKAT data for the timing analysis. The light coloured data points are from the Parkes UWL observations.
Extended Data Fig. 2 Examples of quasi-periodic pulses.
The top two rows show pulse profiles and their corresponding ACFs at 306.24μs resolution, respectively. The value the of quasi-period is indicated by the black vertical lines. The bottom two rows show the off-pulse regions and their corresponding ACFs.
Extended Data Fig. 3 Example of a pulse exhibiting more than one quasi-period.
Some quasi-periodic pulses as shown here, exhibit multiple quasi-periods within a single rotation.
Extended Data Fig. 4 Estimates of the quasi-period across all epochs.
The (orange) circles are the measured quasi-periods for each single pulse. The most commonly observed average quasi-period is 75.82 ms with the minimum period being 9.57 ms. The lags are arranged in lag length and not in time order.
Extended Data Fig. 5 Radio light-curves of PSR J0901 − 4046.
A regular series of pulsed emission detected in the L-band snapshot imaging for six observing epochs. Please refer to the Snapshot Imaging section of the Methods for details.
Extended Data Fig. 6 Polarization profiles of PSR J0901 − 4046 at 1.3 GHz and 700 MHz.
Top Panel: Time series of two single pulses of PSR J0901 − 4046 at 1284 MHz. Bottom Panel: Two different single pulse time series at 737 MHz. For both panels, the total intensity is represented by the black solid line, the red solid line denotes the linear polarization while the blue solid line denotes circular polarization. The polarization position angle is not absolutely calibrated at 737 MHz.
Extended Data Fig. 7 MeerKAT image of the PSR J0901 − 4046 region at 1.28 GHz.
The left hand panel shows the image with the pulsed emission included, and the right hand panel shows the same field following the removal of the integration times containing pulses. No persistent radio source is associated with PSR J0901 − 4046 to a 3σ limit of 18 μJy beam−1. The diffuse shell-like structure that surrounds PSR J0901 − 4046 is partially visible, possibly the supernova remnant from the event that formed the neutron star.
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Caleb, M., Heywood, I., Rajwade, K. et al. Discovery of a radio-emitting neutron star with an ultra-long spin period of 76 s. Nat Astron 6, 828–836 (2022). https://doi.org/10.1038/s41550-022-01688-x
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DOI: https://doi.org/10.1038/s41550-022-01688-x
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