¹Jodrell Bank Observatory, University of Manchester, Macclesfield, Cheshire SK11 9DL, UK. ²Australia Telescope National Facility - CSIRO, PO Box 76, Epping, New South Wales 1710, Australia. ³Astronomy Department and NAIC, Cornell University, Ithaca, New York 14853, USA. ⁴Columbia Astrophysics Laboratory, Columbia University, 550 West 120th Street, New York, New York 10027, USA. ⁵INAF - Osservatorio Astronomico di Cagliari, Loc. Poggio dei Pini, Strada 54, 09012 Capoterra, Italy. ⁶Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, British Columbia V6T 1Z1, Canada. ⁷Dipartimento di Fisica, Universita di Cagliari, Strada Provinciale Monserrato-Sestu, km 0.700, 09042 Monserrato, Italy.

doi:10.1038/nature04440

Received 25 August; accepted 15 November 2005.

Supplementary Information is linked to the online version of the paper at www.nature.com/nature.

Author Information Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests. Correspondence and requests for materials should be addressed to M.A.McL. ([email protected]).

Nature 439(7078):p 817-820, February 16, 2006.

The radio sky is relatively unexplored for transient signals, although the potential of radio-transient searches is high. This was demonstrated recently by the discovery of a previously unknown type of source, varying on timescales of minutes to hours. Here we report a search for radio sources that vary on much shorter timescales. We found eleven objects characterized by single, dispersed bursts having durations between 2 and 30 ms. The average time intervals between bursts range from 4 min to 3 h with radio emission typically detectable for <1 s per day. From an analysis of the burst arrival times, we have identified periodicities in the range 0.4-7 s for ten of the eleven sources, suggesting origins in rotating neutron stars. Despite the small number of sources detected at present, their ephemeral nature implies a total Galactic population significantly exceeding that of the regularly pulsing radio pulsars. Five of the ten sources have periods >4 s, and the rate of change of the pulse period has been measured for three of them; for one source, we have inferred a high magnetic field strength of 5 × 10¹³G. This suggests that the new population is related to other classes of isolated neutron stars observed at X-ray and γ-ray wavelengths.

Transient radio bursts from rotating neutron stars