Enhanced Radio Activity in the Quiescent State of the X-ray Transient V404 Cyg (=GS2023+338)
ATel #54; R. M. Hjellming, M. P. Rupen (NRAO), A. J. Mioduszewski (U. Sydney), R. Narayan (Harvard Univ.)
on 29 Feb 2000; 17:36 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: R.M. Hjellming (rhjellmi@nrao.edu)
Subjects: Radio, X-ray, Request for Observations, Binary, Black Hole, Transient
Referred to by ATel #: 56
The quiescent state of the X-ray transient and 14 solar mass black hole binary,
V404 Cyg (=GS2023+338), since it ended the long decay that accompanied its initial
discovery event at X-ray, optical, and radio wavelengths (Han and Hjellming, Ap.J.,
400, 304, 1992), has been associated with a 0.4 mJy radio source and,
most of the time, a 7 microJy X-ray source at 2-12 keV (1 ASM count/sec = 24 microJy)
in the RXTE ASM daily averages.
Starting in early 1999 VLA observations of the V404 Cyg radio source showed
fluctuations ranging from 0.1 to 0.8 mJy on time scales of days, and on 2000 Feb 28 it reached
1.5 mJy - the highest radio flux level since the end of the initial discovery event ten
years earlier. During the most recent, and most extreme, radio fluctuations, the RXTE ASM
has been showing increases to the 20-34 microJy level, and the 1.5 mJy radio measurement
was preceded by a month-long X-ray "event" reaching up to 34 microJy. Because of the
possibility that this activity may be preliminary to a change of state, judicious
multiwavelength observations are suggested.
