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Published July 1, 2007 | Published + Submitted
Journal Article Open

Periodic bursts of coherent radio emission from an ultracool dwarf


We report the detection of periodic (p = 1.96 hr) bursts of extremely bright, 100% circularly polarized, coherent radio emission from the M9 dwarf TVLM 513-46546. Simultaneous photometric monitoring observations have established this periodicity to be the rotation period of the dwarf. These bursts, which were not present in previous observations of this target, confirm that ultracool dwarfs can generate persistent levels of broadband, coherent radio emission, associated with the presence of kG magnetic fields in a large-scale, stable configuration. Compact sources located at the magnetic polar regions produce highly beamed emission generated by the electron cyclotron maser instability, the same mechanism known to generate planetary coherent radio emission in our solar system. The narrow beams of radiation pass our line of sight as the dwarf rotates, producing the associated periodic bursts. The resulting radio light curves are analogous to the periodic light curves associated with pulsar radio emission highlighting TVLM 513-46546 as the prototype of a new class of transient radio source.

Additional Information

© 2007 American Astronomical Society. Received 2007 February 20; accepted 2007 May 14; published 2007 June 15. We gratefully acknowledge the support of the HEA funded Cosmogrid project, the Irish Research Council for Science, Engineering, and Technology (IRCSET), and Enterprise Ireland. A. G. is supported by Science Foundation Ireland (grant 07/RFP/PHYF553). Armagh Observatory is grant-aided by the N. Ireland Department of Culture, Arts, and Leisure. We would like to thank Ray Butler, James Mc Donald, and Evan Keane for assistance with certain aspects of this manuscript and the referee Manuel Güdel, whose extensive comments significantly improved this manuscript.

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Published - 1538-4357_663_1_L25.pdf

Submitted - 0705.2054v1.pdf


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