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Published September 1, 2017 | Submitted + Published
Journal Article Open

A Panchromatic View of Brown Dwarf Aurorae


Stellar coronal activity has been shown to persist into the low-mass star regime, down to late M-dwarf spectral types. However, there is now an accumulation of evidence suggesting that at the end of the main sequence, there is a transition in the nature of the magnetic activity from chromospheric and coronal to planet-like and auroral, from local impulsive heating via flares and MHD wave dissipation to energy dissipation from strong large-scale magnetospheric current systems. We examine this transition and the prevalence of auroral activity in brown dwarfs through a compilation of multiwavelength surveys of magnetic activity, including radio, X-ray, and optical. We compile the results of those surveys and place their conclusions in the context of auroral emission as a consequence of large-scale magnetospheric current systems that accelerate energetic electron beams and drive the particles to impact the cool atmospheric gas. We explore the different manifestations of auroral phenomena, like Hα, in brown dwarf atmospheres and define their distinguishing characteristics. We conclude that large-amplitude photometric variability in the near-infrared is most likely a consequence of clouds in brown dwarf atmospheres, but that auroral activity may be responsible for long-lived stable surface features. We report a connection between auroral Hα emission and quiescent radio emission in electron cyclotron maser instability pulsing brown dwarfs, suggesting a potential underlying physical connection between quiescent and auroral emissions. We also discuss the electrodynamic engines powering brown dwarf aurorae and the possible role of satellites around these systems both to power the aurorae and seed the magnetosphere with plasma.

Additional Information

© 2017 The American Astronomical Society. Received 2017 January 22; revised 2017 July 28; accepted 2017 August 8; published 2017 September 1. J.S.P. was supported by a grant from the National Science Foundation Graduate Research Fellowship under grant No. (DGE-11444469). J.S.P. would like to thank Jackie Villadsen for useful discussions in the development of the arguments presented in this article. The authors would also like to thank the anonymous referee for a thorough reading of this manuscript and for providing critical feedback that greatly strengthened this work. This research has benefited from the M-, L-, T-, and Y-dwarf compendium housed at DwarfArchives.org. This research has benefited from the Ultracool RIZzo Spectral Library maintained by Jonathan Gagné and Kelle Cruz. This researched has benefited from the Database of Ultracool Parallaxes maintained by Trent Dupuy. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation.

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Published - Pineda_2017_ApJ_846_75.pdf

Submitted - 1708.02942.pdf


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August 19, 2023
October 17, 2023