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Authors: Williams, P. K. G.
Casewell, Sarah L.
Stark, C. R.
Littlefair, S. P.
Helling, C.
Berger, E.
First Published: 9-Dec-2015
Publisher: IOP Publishing LTD
Citation: Astrophysical Journal, 2015, 815 (1), 64
Abstract: The well-studied M9 dwarf TVLM 513–46546 is a rapid rotator (${P}_{\mathrm{rot}}\sim 2$ hr) hosting a stable, dipolar magnetic field of ~3 kG surface strength. Here we report its detection with ALMA at 95 GHz at a mean flux density of 56 ± 12 μJy, making it the first ultracool dwarf detected in the millimeter band, excluding young, disk-bearing objects. We also report flux density measurements from unpublished archival VLA data and new optical monitoring data from the Liverpool Telescope. The ALMA data are consistent with a power-law radio spectrum that extends continuously between centimeter and millimeter wavelengths. We argue that the emission is due to the synchrotron process, excluding thermal, free–free, and electron cyclotron maser emission as possible sources. During the interval of the ALMA observation that phases with the maximum of the object's optical variability, the flux density is higher at a ~1.8σ significance level. These early results show how ALMA opens a new window for studying the magnetic activity of ultracool dwarfs, particularly shedding light on the particle acceleration mechanism operating in their immediate surroundings.
DOI Link: 10.1088/0004-637X/815/1/64
ISSN: 0004-637X
eISSN: 1538-4357
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright © 2015. The American Astronomical Society. All rights reserved. Deposited with reference to the publisher’s archiving policy available on the SHERPA/RoMEO website.
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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