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Cygnus X-1 radio observations

ATel #3535; G. G.Pooley (Cavendish Laboratory, Cambridge, UK)
on 9 Aug 2011; 11:16 UT
Credential Certification: Guy Pooley (ggp1@cam.ac.uk)

Subjects: Radio, X-ray, Binary, Black Hole, Star

Referred to by ATel #: 3546, 3616

Radio monitoring of Cygnus X-1 at 15 GHz with the AMI Large Array in Cambridge, UK shows a falling flux density, consistent with the possible hard-to-soft state transition reported by Negoro et al (Atel #3534). The most recent observation (2011 Aug 09, 00h56m to 01h34m UT, MJD 55782.05) shows a mean flux density of 7.7 mJy, decreasing over the observation. The radio flux density, together with the MAXI low-energy and Swift BAT light curve for the last 6 weeks, are shown in http://www.mrao.cam.ac.uk/~guy/cx1/2011-jul-aug.ps and the previous soft-state light curves in http://www.mrao.cam.ac.uk/~guy/cx1/2010-2011.ps