Rapid rise of 1.4 GHz radio emission from Cygnus X-3 detected with the Nasu telescope array

ATel #17746; K. Tsubono (Univ. Tokyo), K. Asuma (Kawaguchi-Kita High School), K. Niinuma (Yamaguchi Univ.), K. Takefuji (JAXA) and T. Daishido (Waseda Univ.)
on 10 Apr 2026; 03:54 UT
Credential Certification: Kimio Tsubono (tsubono@phys.s.u-tokyo.ac.jp)

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Following the report of a new radio outburst of Cygnus X-3 at frequencies above 4 GHz by the RATAN-600 team (ATel #17741), we carried out monitoring observations with the Nasu radio telescope array at 1.4 GHz.

No significant emission was detected in the preceding observations on April 3–5 (UT), with a typical detection limit of ~200 mJy. We detected the onset of a radio flare at 1.4 GHz on 2026 April 6 (UT), when the flux density reached 0.7 ± 0.03 Jy.

The flux density then increased rapidly to 5.3 ± 0.03 Jy on April 7 (UT), and remained at a comparable level (5.4 ± 0.03 Jy) on April 8 (UT).

The rapid rise of the 1.4 GHz emission following the higher-frequency detection reported by RATAN-600 suggests a frequency-dependent evolution of the radio flare, consistent with synchrotron self-absorption effects in an expanding plasma. Such behavior is commonly observed during major radio outbursts of Cygnus X-3 and indicates that the present activity may develop into a strong radio flare.

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