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The magnetosphere of the ultracool dwarf DENIS 1048-3956

Ravi, Vikram; Hallinan, Gregg; Hobbs, G; Champion, David J.

Description

Ultracool dwarfs, the least-massive contributors to the stellar mass function, exhibit striking magnetic properties that are inconsistent with trends for more massive stars. Here, we present the widest-band radio observations to date of an ultracool dwarf, DENIS-PJ104814.9-395604, in four 2GHz bandwidths between wavelengths of 1cm and 10cm. These data were obtained with the Australia Telescope Compact Array using the new Compact Array Broadband Backend instrument. We detected a stable...[Show more]

dc.contributor.authorRavi, Vikram
dc.contributor.authorHallinan, Gregg
dc.contributor.authorHobbs, G
dc.contributor.authorChampion, David J.
dc.date.accessioned2015-12-10T22:32:45Z
dc.identifier.issn2041-8205
dc.identifier.urihttp://hdl.handle.net/1885/55904
dc.description.abstractUltracool dwarfs, the least-massive contributors to the stellar mass function, exhibit striking magnetic properties that are inconsistent with trends for more massive stars. Here, we present the widest-band radio observations to date of an ultracool dwarf, DENIS-PJ104814.9-395604, in four 2GHz bandwidths between wavelengths of 1cm and 10cm. These data were obtained with the Australia Telescope Compact Array using the new Compact Array Broadband Backend instrument. We detected a stable negatively sloped power-law spectrum in total intensity, with spectral index α = 1.71 ± 0.09. Circular polarization fractions between 0.25 and 0.4 were found at the low-frequency end of our detection band. We interpret these results as indicative of gyrosynchrotron emission. We suggest that the radio emission originates from beyond the corotation radius, RC , of the star. Adopting this model, we find RC between 1.2 R * and 2.9 R *, and a non-thermal electron density and magnetic field strength between 105 and 107.2cm-3 and between 70 and 260G, respectively, at RC . The model accounts for the violation of the Güdel-Benz relation between X-ray and radio luminosities of low-mass stars by DENIS-PJ104814.9-395604.
dc.publisherInstitute of Physics Publishing Ltd.
dc.sourceAstrophysical Journal Letters
dc.subjectKeywords: radio continuum: stars; stars: individual (DENIS-P J104814.9-395604); stars: low-mass; stars: magnetic field
dc.titleThe magnetosphere of the ultracool dwarf DENIS 1048-3956
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume735
dc.date.issued2011
local.identifier.absfor020110 - Stellar Astronomy and Planetary Systems
local.identifier.ariespublicationf5625xPUB344
local.type.statusPublished Version
local.contributor.affiliationRavi, Vikram, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationHallinan, Gregg, National Radio Astronomy Observatory
local.contributor.affiliationHobbs, G, CSIRO, Australia Telescope National Facility
local.contributor.affiliationChampion, David J., Max-Planck-Institut für Radioastronomie
local.description.embargo2037-12-31
local.bibliographicCitation.issue1
local.identifier.doi10.1088/2041-8205/735/1/L2
dc.date.updated2016-02-24T09:10:56Z
local.identifier.scopusID2-s2.0-79960907517
CollectionsANU Research Publications

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