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Electron-beam-induced Radio Emission from Ultracool Dwarfs

Yu, S. and Doyle, J. G. and Kuznetsov, A. and Hallinan, G. and Antonova, A. and MacKinnon, A. L. and Golden, A. (2012) Electron-beam-induced Radio Emission from Ultracool Dwarfs. Astrophysical Journal, 752 (1). Art. No. 60. ISSN 0004-637X. https://resolver.caltech.edu/CaltechAUTHORS:20120717-083657470

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Abstract

We present the numerical simulations for an electron-beam-driven and loss-cone-driven electron-cyclotron maser (ECM) with different plasma parameters and different magnetic field strengths for a relatively small region and short timescale in an attempt to interpret the recent discovered intense radio emission from ultracool dwarfs. We find that a large amount of electromagnetic (EM) field energy can be effectively released from the beam-driven ECM, which rapidly heats the surrounding plasma. A rapidly developed high-energy tail of electrons in velocity space (resulting from the heating process of the ECM) may produce the radio continuum depending on the initial strength of the external magnetic field and the electron beam current. Both significant linear polarization and circular polarization of EM waves can be obtained from the simulations. The spectral energy distributions of the simulated radio waves show that harmonics may appear from 10 to 70ν_(pe) (ν_(pe) is the electron plasma frequency) in the non-relativistic case and from 10 to 600ν_(pe) in the relativistic case, which makes it difficult to find the fundamental cyclotron frequency in the observed radio frequencies. A wide frequency band should therefore be covered by future radio observations.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1088/0004-637X/752/1/60DOIArticle
http://iopscience.iop.org/0004-637X/752/1/60/PublisherArticle
https://arxiv.org/abs/1204.2261arXivDiscussion Paper
Additional Information:© 2012 American Astronomical Society. Received 2011 December 14; accepted 2012 April 4; published 2012 May 25. Research at the Armagh Observatory is grant-aided by the N. Ireland Department of Culture, Arts, and Leisure. We also thank the Leverhulme Trust for their support of this project. A.A. gratefully acknowledges the support of the Bulgarian National Science Fund (Grant No. DDVU02/40−2010). A.L.M. thanks STFC for support through a Rolling Grant. S.Y. thanks the 9th international space simulation school for the tutorial courses and Professor Y. Omura for discussions. S.Y. also thanks Dr. J. McDonald in NUI,Galway for discussions.We thank the referee for his/her helpful and constructive comments.
Funders:
Funding AgencyGrant Number
Department of Culture, Arts, and Leisure (Northern Ireland)UNSPECIFIED
Leverhulme TrustUNSPECIFIED
Bulgarian National Science FundDDVU02/40-2010
Science and Technology Facilities Council (STFC)UNSPECIFIED
Subject Keywords: brown dwarfs; magnetic fields; masers; polarization; radio continuum: stars; stars: low-mass
Issue or Number:1
Record Number:CaltechAUTHORS:20120717-083657470
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20120717-083657470
Official Citation:Electron-beam-induced Radio Emission from Ultracool Dwarfs S. Yu et al. 2012 ApJ 752 60
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:32493
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:17 Jul 2012 16:03
Last Modified:03 Oct 2019 04:01

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