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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
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Official URL: https://doi.org/10.1051/0004-6361/201732380
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 | |||||||||
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| Subjects: | Q Science > QB Astronomy Q Science > QD Chemistry |
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| Divisions: | Faculty of 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: |
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| 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 | |||||||||
| Grant number: | , | |||||||||
| RIOXX Funder/Project Grant: |
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