Alert Notice 835: V404 Cyg time series observations needed now for multiwavelength campaign

October 13, 2023

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Prof. Tom Maccarone (Texas Tech University) requests AAVSO observers' assistance in monitoring the quiescent black hole X-ray binary V404 Cyg in support of multiwavelength observations scheduled for 2023 October 15-16 with several instruments, including: James Webb Space Telescope, XMM-Newton, Chandra X-ray Observatory, ALMA (Atacama Large Millimeter/submillimeter Array), VLA (the Very Large Array), and GranTeCan (Gran Telescopio Canarias).

JWST will observe V404 Cyg on 2023 Oct. 15 19:30 UT - Oct. 16 00:56 UT

CCD observations (V, B, R, I) are requested (V and I prioritized) beginning immediately and continuing through October 18-19. Other filters will also be useful, but CV/CR are not requested. A signal-to-noise ratio of 20 or better is needed (uncertainty of +/-0.05 mag or less).

Re the cadence of time-series and duration of observations, Prof. Maccarone writes: "In the past, flaring at the 10-30% level has been seen on timescales of ~hours, so...good measurements with time resolution of about 15 minutes [throughout the entire requested period]...would be incredibly helpful to put the observations into the longer term context." It will be particularly important to cover the interval from a few hours before the JWST observations to a few hours after they end.

Prof. Maccarone reports that V404 Cyg has a quiescent magnitude of 16.6 R. VSX gives its range as 11.2 - 18.8 V (this range includes major outbursts of V404 Cyg; the system, now in quiescence, is expected to be around minimum). The most recent observations in the AAVSO International Database show it  <14.1 visual magnitude on 2023 Oct. 11.7514 UT (W. Kriebel, Schierling/Walkenstetten, Germany) and <15.4 visual on Oct 8.8028 UT (P. Dubovsky, Kolonica, Slovakia).

Please note that the coordinated observations were originally scheduled for October 14-15 but were revised.

Coordinates (J2000):  R.A. 20 24 03.82    Dec. +33 52 02.1   (from VSX entry for V404 Cyg)

Charts with comparison stars for V404 Cyg may be created using the AAVSO Variable Star Plotter (VSP).

Please report observations to the AAVSO International Database using the name V404 CYG.

This Alert Notice was compiled by Elizabeth O. Waagen using information provided by Prof. Maccarone.


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