Complete fading of the recent 1.4 GHz radio flare in Cygnus X-3 observed with the Nasu radio telescope array

ATel #17758; K. Tsubono (Univ. Tokyo), K. Asuma (Kawaguchi-Kita High School), K. Niinuma (Yamaguchi Univ.), K. Takefuji (JAXA) and T. Daishido (Waseda Univ.)
on 19 Apr 2026; 01:18 UT
Credential Certification: Kimio Tsubono (tsubono@phys.s.u-tokyo.ac.jp)

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Following our report of the recent 1.4 GHz radio flare from Cygnus X-3 (ATel #17746), we continued daily monitoring observations with the Nasu radio telescope array.

After reaching a peak flux density of 5.4 ± 0.03 Jy on 2026 April 8 (UT), the radio emission showed a steady monotonic decline without any further rebrightening. The flux density decreased to 0.4 Jy by April 15 (UT), and in subsequent observations on April 16 and 17 (UT), the source was no longer detected above the 5-sigma detection threshold of approximately 200 mJy.

The flare has therefore completed its decay phase within about 9 days after the peak, indicating that this event evolved as a relatively short-lived radio flare at 1.4 GHz rather than developing into a major prolonged outburst.

The updated light curve is available here.

The Nasu telescope array is a spatial fast Fourier transform (FFT) interferometer consisting of eight linearly aligned antennas with 20 m spherical dishes. This type of interferometer was developed to survey transient radio sources, providing an angular resolution comparable to that of a 160 m dish and a field of view equivalent to that of a 20 m dish.

Nasu telescope array HP:
https://nasu-radio-telescope.jp