J/ApJ/906/10 Radio flares of Cygnus X-3 (Egron+, 2021)
Investigating the Mini and Giant Radio Flare Episodes of Cygnus X-3.
Egron E., Pellizzoni A., Righini S., Giroletti M., Koljonen K.,
Pottschmidt K., Trushkin S., Lobina J., Pilia M., Wilms J., Corbel S.,
Grinberg V., Loru S., Trois A., Rodriguez J., Lahteenmaki A., Tornikoski M.,
Enestam S., Jarvela E.
<Astrophys. J., 906, 10 (2021)>
=2021ApJ...906...10E 2021ApJ...906...10E
ADC_Keywords: QSOs; Radio sources; Spectra, radio; Spectra, millimetric/submm
Keywords: High mass x-ray binary stars ; Radio jets
Abstract:
The microquasar Cygnus X-3 underwent a giant radio flare in 2017
April, reaching a maximum flux of ∼16.5Jy at 8.5GHz. We present
results from a long monitoring campaign carried out with Medicina at
8.5, 18.6, and 24.1GHz, parallel to the Metsahovi radio telescope at
37GHz, from 2017 April 4 to 11. We observe a spectral steepening from
α=0.2 to 0.5 (with Sν∝ν-α) within 6hr of
the epoch of the flare's peak maximum, and rapid changes in the
spectral slope in the following days during brief enhanced emission
episodes while the general trend of the radio flux density indicated
the decay of the giant flare. We further study the radio orbital
modulation of CygX-3 emission associated with the 2017 giant flare and
with six mini-flares observed in 1983, 1985, 1994, 1995, 2002, and
2016. The enhanced emission episodes observed during the decline of
the giant flare at 8.5GHz coincide with the orbital phase φ∼0.5
(orbital inferior conjunction). On the other hand, the light curves of
the mini-flares observed at 15-22GHz peak at φ∼0, except for the
2016 light curve, which is shifted 0.5w.r.t. the other ones. We
attribute the apparent phase shift to the variable location of the
emitting region along the bent jet. This might be explained by the
different accretion states of the flaring episodes (the 2016
mini-flare occurred in the hypersoft X-ray state).
Description:
Following the detection of the start of the flare in Cyg X-3 by the
RATAN, we triggered a Target-of-Opportunity program with the Medicina
radio telescope, 32m, in order to follow the evolution of the radio
emission during the whole duration of the giant flare. The frequency
agility offered by Medicina (i.e., the change of the observing
receiver/frequency requiring at most a few minutes), allowed us to
carry out observations at 8.5, 18.6, and 24.1GHz (typically 30 minutes
each) from 2017 April 4 to 11. We performed on-the-fly cross-scans in
RA and DEC directions, setting a bandwidth of 680MHz. Scans were
performed along a length of 0.6deg, at a velocity of 2.4's at 8.5GHz.
We selected a bandwidth of 1200MHz, scans of 0.2deg in length and a
scan velocity of 0.8's in the K band (18.6 and 24.1GHz).
Objects:
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RA (2000) DE Designation(s)
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20 32 25.78 +40 57 27.9 Cygnus X-3 = V* V1521 Cyg
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig1a.dat 26 150 Medicina radio telescope at 8.5GHz
fig1b.dat 26 112 Medicina radio telescope at 18.6GHz
fig1c.dat 26 121 Medicina radio telescope at 24.1GHz
fig1d.dat 26 33 Metsahovi radio observatory at 37GHz
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See also:
J/A+AS/132/305 : Extragal. radio sources at 22, 37 & 87GHz (Terasranta+ 1998)
J/MNRAS/406/307 : Radio variations of Cygnus X-3 (Koljonen+, 2010)
J/A+A/551/A32 : Catching the radio flare in CTA 102 (Fromm+, 2013)
J/MNRAS/467/L31 : SS Cyg rapid radio flaring in 2016 (Mooley+, 2017)
http://www.med.ira.inaf.it/ : Medicina Radio Astronomical Station webpage
Byte-by-byte Description of file: fig1[abcd].dat
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Bytes Format Units Label Explanations
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1- 11 F11.5 d MJD Modified Julian Date of observation, JD-2400000.5
13- 19 F7.4 Jy Flux Flux
21- 26 F6.4 Jy e_Flux Flux uncertainty
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 16-May-2022