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Radio Imaging of V404 Cyg

Journal Article · · AIP Conference Proceedings
DOI:https://doi.org/10.1063/1.2945093· OSTI ID:21143325
; ; ;  [1]
  1. National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States)
V404 Cyg is a black hole binary which has remained in the low/hard, quiescent X-ray state for several years, while still being quite variable at all wavelengths on timescales of hours. The optical and X-ray variability are highly correlated, and interpreted in terms of rapid changes in the irradiation of the accretion disk. Here we present the results of simultaneous radio observations with arcsecond (Very Large Array) and milliarcsecond (Very Long Baseline Array) angular resolution. While the low-resolution data show V404 Cyg varying on timescales of roughly an hour between 0 and 1 mJy, the high-resolution data yield no detections, with a typical rms noise of 0.125 mJy/beam in an hour. The combined result implies that the source must be larger than {approx}1 mas, corresponding to 4(d/4 kpc) AU. The steady emission has a much lower surface brightness than previously imaged outflows in other X-ray binaries, while the non-detection of the flare emission may be due to a high outflow speed (> or approx. 0.6(d/4 kpc)c). Either the radio size is broadened enormously by interstellar scattering, or the bulk of the radio emission is widely distributed.
OSTI ID:
21143325
Journal Information:
AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 1010; ISSN APCPCS; ISSN 0094-243X
Country of Publication:
United States
Language:
English