J/MNRAS/467/L31 SS Cyg rapid radio flaring in 2016 (Mooley+, 2017)
Rapid radio flaring during an anomalous outburst of SS Cyg.
Mooley K.P., Miller-jones J.C.A., Fender R.P., Sivakoff G.R., Rumsey C.,
Perrott Y., Titterington D., Grainge K., Russell T.D., Carey S.H.,
Hickish J., Razavi-ghods N., Scaife A., Scott P., Waagen E.O.
<Mon. Not. R. Astron. Soc., 467, L31-35 (2017)>
=2017MNRAS.467L..31M 2017MNRAS.467L..31M (SIMBAD/NED BibCode)
ADC_Keywords: Novae ; Radio continuum ; X-ray sources
Keywords: stars: dwarf novae - radio continuum: stars - X-rays: stars
Abstract:
The connection between accretion and jet production in accreting white
dwarf binary systems, especially dwarf novae, is not well understood.
Radio wavelengths provide key insights into the mechanisms responsible
for accelerating electrons, including jets and outflows. Here, we
present densely sampled radio coverage, obtained with the Arcminute
MicroKelvin Imager Large Array, of the dwarf nova SS Cyg during its
2016 February anomalous outburst. The outburst displayed a slower rise
(3d/mag) in the optical than typical ones and lasted for more than
three weeks. Rapid radio flaring on time-scales <1h was seen
throughout the outburst. The most intriguing behaviour in the radio
was towards the end of the outburst where a fast, luminous ('giant'),
flare peaking at ∼20mJy and lasting for 15min was observed.
This is the first time that such a flare has been observed in SS Cyg
and insufficient coverage could explain its non-detection in previous
outbursts. These data, together with past radio observations, are
consistent with synchrotron emission from plasma ejection events as
being the origin of the radio flares. However, the production of the
giant flare during the declining accretion rate phase remains
unexplained within the standard accretion-jet framework and appears to
be markedly different to similar patterns of behaviour in X-ray
binaries.
Description:
We requested close monitoring of SS Cyg and immediate submission of
observations to the American Association of Variable Star Observers
(AAVSO; Special Notice #412, Alert Notice 536) in order to catch the
rise phase of the outburst and obtain a well-sampled optical light
curve.
We monitored the AAVSO light curve, and once the optical light curve
reached 11.5mag in the pre-validated V band (on 2016 February 11), we
triggered the Arcminute MicroKelvin Imager Large Array (AMI-LA)
radio telescope. Observations were made with the new digital
correlator having 4096 channels across a 5GHz bandwidth between 13
and 18GHz. SS Cyg was monitored for about 10h every day throughout
the ∼3 weeks of outburst. The phase calibrator, J2153+4322, was
observed every 12min for about 1.5min. The log of AMI-LA
observations is given in Table 1 .
Objects:
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RA (2000) DE Designation(s)
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21 42 42.80 +43 35 09.9 SS Cyg = BD+42 4189a
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 36 53 15.5GHz AMI-LA measurements of the SS Cyg
table2.dat 36 61 15.5GHz finely sampled measurements of the
"giant" flare
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Byte-by-byte Description of file: table1.dat table2.dat
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Bytes Format Units Label Explanations
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1- 11 F11.5 d MJD Observation date
13- 17 F5.1 min Dur Duration
19- 23 I5 uJy S15.5GHz Flux density at 15.5GHz (1)
25- 27 I3 uJy e_S15.5GHz rms uncertainty on S15.5GHz
29- 32 F4.1 --- alpha ? Spectral slope between 16.8GHZ and 14.2GHz (2)
34- 36 F3.1 --- e_alpha ? rms uncertainty on alpha
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Note (1): S15.5GHz is the peak pixel values at the location of SS Cyg.
Flux density values that are <2σ are to be considered as non-detections.
Note (2): In table1, the spectral index values have large uncertainties except
in the cases of flare peaks, and only those values are noted here.
In table2, Only the spectral index values having uncertainties less than
two are noted here.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 15-Nov-2019