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VLA radio observations of AR Scorpii

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Stanway, Elizabeth R., Marsh, Tom, Chote, Paul, Gänsicke, B. T. (Boris T.), Steeghs, D. and Wheatley, Peter J. (2018) VLA radio observations of AR Scorpii. Astronomy and Astrophysics, 611 . 66. doi:10.1051/0004-6361/201732380 ISSN 0004-6361.

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Official URL: https://doi.org/10.1051/0004-6361/201732380

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Abstract

Aims

AR Scorpii is unique amongst known white dwarf binaries in showing powerful pulsations extending to radio frequencies. Here we aim to investigate the multi-frequency radio emission of AR Sco in detail, in order to constrain its origin and emission mechanisms. Methods. We present interferometric radio frequency imaging of AR Sco at 1.5, 5 and 9 GHz, analysing the total flux and polarization behaviour of this source at high time resolution (10, 3 and 3 s), across a full 3.6 hr orbital period in each band.

Results

We find strong modulation of the radio flux on the orbital period and the orbital sideband of the white dwarf’s spin period (also known as the "beat" period). This indicates that, like the optical flux, the radio flux arises predominantly from on or near the inner surface of the M-dwarf companion star. The beat-phase pulsations of AR Sco decrease in strength with decreasing frequency. They are strongest at 9 GHz and at an orbital phase ∼0.5. Unlike the optical emission from this source, radio emission from AR Sco shows weak linear polarization but very strong circular polarization, reaching ∼30% at an orbital phase ∼0.8. We infer the probable existence of a non-relativistic cyclotron emission component, which dominates at low radio frequencies. Given the required magnetic fields, this also likely arises from on or near the M-dwarf.

Item Type: Journal Article
Subjects: Q Science > QB Astronomy
Q Science > QD Chemistry
Divisions: Faculty of Science, Engineering and Medicine > Science > Physics
Library of Congress Subject Headings (LCSH): White dwarf stars, Radio waves--Polarization
Journal or Publication Title: Astronomy and Astrophysics
Publisher: EDP Sciences
ISSN: 0004-6361
Official Date: 1 March 2018
Dates:
DateEvent
1 March 2018Published
27 March 2018Available
22 January 2018Accepted
Volume: 611
Article Number: 66
DOI: 10.1051/0004-6361/201732380
Status: Peer Reviewed
Publication Status: Published
Access rights to Published version: Restricted or Subscription Access
Date of first compliant deposit: 2 February 2018
Date of first compliant Open Access: 16 April 2018
Grant number: ,
RIOXX Funder/Project Grant:
Project/Grant IDRIOXX Funder NameFunder ID
ST/P000495/1Science and Technology Facilities Councilhttp://dx.doi.org/10.13039/501100000271
320964 (WDTracer)H2020 European Research Councilhttp://dx.doi.org/10.13039/100010663
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