CaltechAUTHORS
  A Caltech Library Service

Confirmation of the Electron Cyclotron Maser Instability as the Dominant Source of Radio Emission from Very Low Mass Stars and Brown Dwarfs

Hallinan, G. and Antonova, A. and Doyle, J. G. and Bourke, S. and Lane, C. and Golden, A. (2008) Confirmation of the Electron Cyclotron Maser Instability as the Dominant Source of Radio Emission from Very Low Mass Stars and Brown Dwarfs. Astrophysical Journal, 684 (1). pp. 644-653. ISSN 0004-637X. https://resolver.caltech.edu/CaltechAUTHORS:20140205-111510833

[img]
Preview
PDF - Submitted Version
See Usage Policy.

460Kb
[img]
Preview
PDF - Published Version
See Usage Policy.

362Kb

Use this Persistent URL to link to this item: https://resolver.caltech.edu/CaltechAUTHORS:20140205-111510833

Abstract

We report on radio observations of the M8.5 dwarf LSR J1835+3259 and the L3.5 dwarf 2MASS J00361617+1821104, which provide the strongest evidence to date that the electron cyclotron maser instability is the dominant mechanism producing radio emission in the magnetospheres of ultracool dwarfs. As has previously been reported for the M9 dwarf TVLM 513–46546, periodic pulses of 100% circularly polarized, coherent radio emission are detected from both dwarfs with periods of 2.84 ± 0.01 and 3.08 ± 0.05 hr, respectively, for LSR J1835+3259 and 2MASS J00361617+1821104. Importantly, periodic unpolarized radio emission is also detected from 2MASS J00361617+1821104, and brightness temperature limitations rule out gyrosynchrotron radiation as a source of this radio emission. The unpolarized emission from this and other ultracool dwarfs is also attributed to electron cyclotron maser emission, which has become depolarized on traversing the ultracool dwarf magnetosphere, possibly due to propagations effects such as scattering. Based on available v sin i data in the literature and rotation periods derived from the periodic radio data for the three confirmed sources of electron cyclotron maser emission, TVLM 513–46546, LSR J1835+3259, and 2MASS J00361617+1821104, we determine that the rotation axes of all three dwarfs are close to perpendicular to our line of sight. This suggests a possible geometrical selection effect due to the inherent directivity of electron cyclotron maser emission, that may account for the previously reported relationship between radio activity and v sin i observed for ultracool dwarfs. We also determine the radius of the dwarf LSR J1835+3259 to be ≥0.117 ± 0.012 R_☉. The implied size of the radius, together with the bolometric luminosity of the dwarf, suggests that either LSR J1835 is a young- or intermediate-age brown dwarf, or that current theoretical models underestimate the radii of ultracool dwarfs.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://arxiv.org/abs/0805.4010arXivDiscussion Paper
http://dx.doi.org/10.1086/590360DOIArticle
http://iopscience.iop.org/0004-637X/684/1/644/PublisherArticle
ORCID:
AuthorORCID
Hallinan, G.0000-0002-7083-4049
Golden, A.0000-0002-8599-2031
Additional Information:© 2008 The American Astronomical Society. Received 2008 January 30; accepted 2008 May 23. G. H. and A. G. gratefully acknowledge the support of Science Foundation Ireland (grant No. 07/RFP/PHYF553). Armagh Observatory is grant aided by the Northern Ireland Department of Culture, Arts and Leisure. We thank the referee, Manuel Güdel, for his careful reading of the manuscript and his helpful suggestions for improving the manuscript.
Funders:
Funding AgencyGrant Number
Science Foundation Ireland07/RFP/PHYF553
Northern Ireland Department of Culture, Arts and Leisure (DCAL)UNSPECIFIED
Subject Keywords:pulsars: general; radiation mechanisms: nonthermal; radio continuum: stars; stars: activity; stars: low-mass, brown dwarfs; stars: magnetic fields
Issue or Number:1
Record Number:CaltechAUTHORS:20140205-111510833
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20140205-111510833
Official Citation:Hallinan, G., Antonova, A., Doyle, J. G., Bourke, S., Lane, C., & Golden, A. (2008). Confirmation of the Electron Cyclotron Maser Instability as the Dominant Source of Radio Emission from Very Low Mass Stars and Brown Dwarfs. The Astrophysical Journal, 684(1), 644.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:43671
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:05 Feb 2014 19:52
Last Modified:09 Mar 2020 13:18

Repository Staff Only: item control page