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The inverted radio spectrum of the flare in V 404 Cyg

ATel #7667; S. A. Trushkin, N. A. Nizhelskij, P. G. Tybulev (SAO RAS, Russia)
on 19 Jun 2015; 09:12 UT
Credential Certification: Sergei Trushkin (satr@sao.ru)

Subjects: Radio, Millimeter, Sub-Millimeter, Infra-Red, Optical, X-ray, Request for Observations, Binary, Black Hole, Transient

Referred to by ATel #: 7671, 7674, 7677, 7681, 7686, 7701, 7702, 7708, 7716, 7720, 7721, 7722, 7734, 7740, 7959

We carried out the alert observation of the low mass X-ray binary V 404 Cyg (GS2023+338) with the RATAN-600 radio telescope after detection of the renewed multi-band (X-ray, optical, radio) flaring activity (GCN #17929 ATel #7646, #7647, #7650, #7655, #7658, #7659, #7660, #7661, #7662, #7663). We have detected the radio source with fluxes: 76+-4, 108+-5, 129+-6 and 210+-25 mJy 4.6, 8.2, 11.2, and 21.7 GHz respectively. Time of the measurement is 22:51UT 18 June 2015 (MJD57191.952). The spectrum is very well fitted by the power law: S_nu[mJy] = 27.5 nu^+0.65 [GHz], i.e. the radio emission is inverted (optically thick) synchrotron radiation probably from a compact jet. Indeed such spectra we have measured from other X-ray binaries and flaring microquasars, for example GRS 1915+105. We will continue the radio observations.

The RATAN-600 radio spectrum of V404 Cyg