Mapping the radio coronae of cool stars and brown dwarfs

Gregg Hallinan, Gerry Doyle, Antoaneta Antonova, Stephen Bourke, Moira Jardine, J. F. Donati, Julien Morin, Aaron Golden

Research output: Contribution to journalConference articlepeer-review

1 Scopus citations


The pulsing radio emission detected from ultracool dwarfs can be used as a powerful diagnostic of magnetic field strengths and topologies at and below the substellar boundary. Studies thus far have confirmed magnetic field strengths of 3 kG for two late M dwarfs and 1.7 kG for an L3.5 dwarf, the latter being the first confirmation of kG magnetic fields for an L dwarf. Ongoing long term monitoring of the radio pulses will also investigate the stability of the associated largescale magnetic fields over timescales > 1 year. We also present the preliminary results of a lengthy radio monitoring campaign of the rapidly rotating M4 star V374 Peg, with the resulting light curves phased with magnetic maps previously obtained through Zeeman Doppler Imaging. The radio emission from V374 Peg is strongly modulated by the large scale dipolar magnetic field, with two clear peaks in the radio light curve per period of rotation, occurring when the dipolar field lies in the plane of the sky. These results provide strong evidence that the electron cyclotron maser instability plays a pivotal role in the production of quiescent radio emission from V374 Peg, representing a significant departure from the accepted model of gyrosynchrotron emission as the dominant source of quiescent radio emission from active M dwarfs.

Original languageEnglish (US)
Pages (from-to)146-151
Number of pages6
JournalAIP Conference Proceedings
StatePublished - 2009
Externally publishedYes
Event15th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun - St. Andrews, United Kingdom
Duration: Jul 21 2008Jul 25 2008


  • Activity
  • Brown dwarfs
  • Low-mass
  • Magnetic fields
  • Nonthermal
  • Radiation mechanisms
  • Radio continuum

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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