Transient astronomical sources are typically powered by compact objects and usually signify highly explosive or dynamic events1. Although high-time-resolution observations are often possible in radio astronomy2, they are usually limited to quite narrow fields of view. The dynamic radio sky is therefore poorly sampled, in contrast to the situation in the X-ray and γ-ray bands in which wide-field instruments routinely detect transient sources3. Here we report a transient radio source, GCRT J1745–3009, which was detected during a moderately wide-field monitoring programme of the Galactic Centre region4,5 at 0.33 GHz. The characteristics of its bursts are unlike those known for any other class of radio transient. If located in or near the Galactic Centre, its brightness temperature (∼1016 K) and the implied energy density within GCRT J1745–3009 vastly exceed those observed in most other classes of radio astronomical sources6, and are consistent with coherent emission processes7 that are rarely observed. We conclude that it represents a hitherto unknown class of transient radio sources, the first of possibly many new classes that may be discovered by emerging wide-field radio telescopes8.
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S.D.H. thanks J. Neureuther and M. Lazarova for their assistance in the Galactic Centre transient monitoring programme. We thank D. Chakrabarty, G. Denn, C. Dermer, W. Erickson, R. Remillard, K. Weiler and K. Wood for discussions. The Very Large Array (VLA) is operated by the National Radio Astronomy Observatory (NRAO), which is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities. Basic research in radio astronomy is supported at Sweet Briar College by funding from the Jeffress Memorial Trust and Research Corporation. Basic research in radio and X-ray astronomy at the NRL is supported by the Office of Naval Research.
The authors declare that they have no competing financial interests.
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