Non-detection of Cygnus X-3 following recent radio rebrightening with the Nasu radio telescope array at 1.4 GHz

ATel #17814; K. Tsubono (Univ. Tokyo), K. Asuma (Kawaguchi-Kita High School), K. Niinuma (Yamaguchi Univ.), K. Takefuji (JAXA) and T. Daishido (Waseda Univ.)
on 26 May 2026; 04:44 UT
Credential Certification: Kimio Tsubono (tsubono@phys.s.u-tokyo.ac.jp)

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We report the apparent fading of the recent radio rebrightening activity from Cygnus X-3 observed with the Nasu radio telescope array at 1.4 GHz, following our previous reports (ATel #17746, #17758). The previous evolution of the radio activity, including the first burst and subsequent rebrightening, was reported in ATel #17758.

After the second, relatively modest radio brightening event detected approximately 10 days after the initial burst activity, the radio flux gradually declined. Subsequent observations with the Nasu telescope array on 2026 May 22, 23, and 24 UT yielded no significant detection of Cygnus X-3 above the approximate detection limit of 200 mJy at 1.4 GHz, suggesting that the recent rebrightening episode has faded below our sensitivity threshold. The updated 1.4 GHz light curve obtained with the Nasu telescope array, including the latest non-detection period, is shown here.

Continued monitoring will be carried out to search for renewed radio activity from this source.

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