A giant radio flare of a microquasar Cygnus X-3: simultaneous observation of 22 and 43 GHz by Ulsan station of KVN

ATel #3259; Soon-Wook Kim (Korea Astronomy and Space Science Institute), Jeong-Sook Kim (Korea Astronomy and Space Science Institute/Kyunghee University), Jeewon Lee (Korea Astronomy and Space Science Institute/Kyunghee University)
on 6 Apr 2011; 13:21 UT
Credential Certification: Soon-Wook Kim (xrnovae@empal.com)

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Galactic microquasar Cygnus X-3 has been in its new giant radio flare since 2011 March. Following a report of a rapid rise of radio fluxes within two days from 27 mJy at 15.7 GHz on 2011 March 21 by AMI Large Array to 5-12 Jy at 6-30 GHz on March 22-23 by RATAN-600 radio telescope and OVRO 40-m Telescope (ATel # 3233), we have carried out Target-of-Opportunity observations by the Ulsan station of Korean VLBI Network (KVN). Three 21-m telescopes of KVN, located in Seoul, Ulsan and Jeju Island in Korea, have facilities of a simultaneous observation at 22 and 43 GHz. The daily averaged flux densities measured at the Ulsan station of KVN for 2011 March 25 (MJD 55645.13), 26 (MJD 55646.14), 27 (MJD 55647.13), 28 (MJD 55648.15), 29 (MJD 55649.11), 30 (MJD 55650.23), 31 (MJD 55651.18) and April 1 (MJD 55652.15) are 10.312 +/- 0.049, 7.851 +/- 0.036, 6.981 +/- 0.062, 5.514 +/- 0.039, 2.465 +/- 0.036, 1.236 +/- 0.028, 0.824 +/- 0.022 and 0.741 +/- 0.027 Jy at 22 GHz, and 6.191 +/- 0.047, 4.793 +/- 0.035, 4.424 +/- 0.047, 3.208 +/- 0.046, 1.216 +/- 0.041, 0.601 +/- 0.056, 0.393 +/- 0.030 and 0.435 +/- 0.037 Jy at 43 GHz, respectively, according to a preliminary analysis. On April 2 (MJD 55653.16), the measured flux density at 22 GHz is 0.527 +/- 0.036 Jy. On April 3 (MJD 55654.19), the weather condition was partly cloudy and a very rough estimation of flux density at 22 GHz is about 300 mJy. Since March 29, as it decayed more slowly, the daily fluxes have rapidly varied with time scales of hours or less. Observations at all wavelengths are encouraged.