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Radio observations of outburst from V404 Cyg at 1.4GHz: a fast decay appeared in the nine days light curve

ATel #7733; K. Tsubono, T. Aoki, K. Asuma, T. Daishido, S. Kida, H. Nakajima (Waseda Univ.), K. Niinuma (Yamaguchi Univ.), and K. Takefuji (NICT)
on 30 Jun 2015; 10:44 UT
Credential Certification: Kimio Tsubono (tsubono.kimio@aoni.waseda.jp)

Subjects: Radio, Binary, Black Hole, Transient

Referred to by ATel #: 7737, 7738, 7740, 7763, 7959

As we reported in ATel #7701, we have been observing the sky region around V404 Cyg since May 18. We observe radio sources using Waseda University Nasu radio telescope array with drift-scan mode. Here we report on the observed nine days light curve of V404 Cyg and a recent fast decay appeared in it.

The light curve can be available here.

Until June 20 17:29 UT we could not observe any detectable signal (brighter than 20 mJy) at the position of V404 Cyg. On June 21 17:25 UT, however, we found a significant peak of 313 +/- 30 mJy at that point. Then, the observed flux was decreasing to 105 +/- 30 mJy on June 23 17:17 UT. However, the flux bounced at that point, and was increasing to 364 +/- 30 mJy on June 26 17:05 UT. On June 27 17:01 UT, we recognized a fast decay of the intensity (ATel #7729, #7731 ). After this fast decay the flux seems to be slow decay variables, which might be similar to the characteristics of the radio decay curve appeared in 1989 outburst of V404 Cyg (Han et al. ApJ, 1992).
We will continue this observation run for a while.