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A radio pulsar with an 8.5-second period that challenges emission models

Abstract

Radio pulsars are rotating neutron stars that emit beams of radiowaves from regions above their magnetic poles. Popular theories1,2,3,4 of the emission mechanism require continuous electron–positron pair production, with the potential responsible for accelerating the particles being inversely related to the spin period. Pair production will stop when the potential drops below a threshold, so the models predict that radio emission will cease when the period exceeds a value that depends on the magnetic field strength and configuration. Here we show that the pulsar J2144−3933, previously thought to have a period of 2.84 s, actually has a period of 8.51 s, which is by far the longest of any known radio pulsar. Moreover, under the usual model assumptions5, based on the neutron-star equations of state, this slowly rotating pulsar should not be emitting a radio beam. Therefore either the model assumptions are wrong, or current theories of radio emission must be revised.

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Figure 1: Pulse profile for PSR J2144−3933 at 436 MHz when folded with the correct period of 851 s.
Figure 2: Distribution of known pulsars (excluding globular cluster pulsars) on the PBs plane, where P is the pulsar period and Bs is the surface magnetic dipole field strength.

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Acknowledgements

M.D.Y. thanks R. Burman for comments on this manuscript, and R. Burman and B.Kenny for advice. M.D.Y. also thanks the University of Western Australia for partial financial support. The Parkes radio telescope is part of the Australia Telescope, which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO.

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Correspondence to M. D. Young.

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Young, M., Manchester, R. & Johnston, S. A radio pulsar with an 8.5-second period that challenges emission models. Nature 400, 848–849 (1999). https://doi.org/10.1038/23650

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