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Optical observations of V404 Cyg

ATel #7688; K. Wiersema (Leicester)
on 22 Jun 2015; 15:19 UT
Credential Certification: Klaas Wiersema (kw113@star.le.ac.uk)

Subjects: Optical

Referred to by ATel #: 7708, 7718, 7721, 7722, 7725, 7734, 7740, 7959

The black hole X-ray binary V404 Cyg is currently in outburst (GCN #17929), and fast optical variations in u, g, r, and V have been reported (ATel #7677, #7681, #7686). We observed this source using the University of Leicester 0.5m telescope, using 3 second exposures (with total deadtime between exposures of 2 seconds) in I band. Useful observations were obtained between 00:12 - 01:00 UT on 21 June 2015, after which clouds caused the signal to noise to drop too much. We used a bright star at RA, Dec = 306.00126, 33.77704 (brighter than the XRB) as reference star. In agreement with previous reports, the resulting lightcurve shows variability on all timescales (we are not sensitive to the shortest timescale variations reported by ATel #7677). A preliminary calibration shows a featureless (apart from features introduced by deadtime effects) rednoise power spectrum.

Plot of part of the I band lightcurve.