J/A+A/611/A66 AR Sco VLA radio observations (Stanway+, 2018)
VLA radio observations of AR Scorpii.
Stanway E.R., Marsh T.R., Chote P., Gaensicke B.T., Steeghs D.,
Wheatley P.J.
<Astron. Astrophys. 611, A66 (2018)>
=2018A&A...611A..66S 2018A&A...611A..66S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, white dwarf ; Stars, variable ; Polarization
Keywords: white dwarfs - stars: variables: general -
stars: individual: AR Scorpii - polarization
Abstract:
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.
We present interferometric radio frequency imaging of AR Sco at 1.5, 5
and 9GHz, analysing the total flux and polarization behaviour of this
source at high time resolution (10, 3 and 3s), across a full 3.6h
orbital period in each band.
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
9GHz 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.
Description:
Time series VLA radio observations were undertaken of the highly
variable white dwarf binary AR Scorpii. These were analysed for
periodicity, spectral behaviour and other characteristics. Here we
present time series data in the Stokes I parameter at three
frequencies. These were centred at 1.5GHz (1GHz bandwidth), 5GHz (2GHz
bandwidth) and 9GHz (2GHz bandwidth). The AR Sco binary is
unresolved at these frequencies. In the case of the 1.5GHz data,
fluxes have been deconvolved with those of a neighbouring object.
Objects:
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RA (2000) DE Designation(s)
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16 21 47.29 -22 53 10.4 AR Sco = V* AR Sco
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 34 1608 1.5GHz time series data
table2.dat 34 3861 5GHz time series data
table3.dat 34 3717 9GHz time series data
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Byte-by-byte Description of file: table1.dat table2.dat table3.dat
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Bytes Format Units Label Explanations
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1- 16 F16.10 d RJD Reduced Julian Date (JD-2400000)
18- 24 F7.4 mJy Flux Stokes I flux
29- 34 F6.4 mJy e_Flux Uncertainty on Stokes I flux
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Acknowledgements:
Elisabeth Stanway, e.r.stanway(at)warwick.ac.uk
(End) Patricia Vannier [CDS] 02-Feb-2018