V404 Cyg HST multiwavelength observations scheduled
AAVSO Alert Notice 522July 1, 2015V404 Cyg HST multiwavelength observations scheduled
The dramatic outburst of the black hole X-ray transientLMXB V404 Cyg continues. It was detected 2015 June 16.1688 UT at 16.18 CV +/-0.035 by E. Muyllaert (MUY, Oostende, Belgium); thefirstsatellite detection was by Swift on June 16.77197 UT(Barthelmy et al., GCN Circular 17929, http://gcn.gsfc.nasa.gov/gcn3/17929.gcn3).It was announced in AAVSO Alert Notice 520 (http://www.aavso.org/aavso-alert-notice-520).
V404 Cyg has been observed by the professional communityacross the spectrum from X-ray to radio wavelengths, and by the amateurcommunity in all bands available to it. Large- and small-scale variations havebeen seen occurring at timescales ranging from seconds to hours, with changesof 2-3 magnitudes seen over the course of a few hours. Most recently Swift hasdetected a dust halo around V404 Cyg (Beardmore et al., ATel #7736, http://www.astronomerstelegram.org/?read=7736).
C. Knigge (University of Southampton) et al. announce(ATel #7735,http://www.astronomerstelegram.org/?read=7735)that Far-ultraviolet(FUV) and near-ultraviolet (NUV) spectroscopic observationsof V404 Cyg with the Hubble Space Telescope have been scheduled for 2015 July10, 11, and 12 according to the schedule below:
FUV: 10 Jul 2015 12:12:19 - 19:23:20 UTCNUV: 11 Jul 2015 13:37:07 - 16:08:55 UTCFUV: 12 Jul 2015 11:56:15 - 19:08:08 UTC
The HST observations were scheduled for the satellite'searliest availability, and the timing is best for ground-based locations fromthe western US and eastern Asia.
Regardless of location, all observers are requested tocontinue to observe V404 Cyg. Time-series observations are requested during asmuch of the HST observation intervals as possible, in as many bands aspossible. A high cadence is recommended in order to detect the veryshort-period variations that have been seen.
Observations in the AAVSO International Database showthat most recently V404 Cyg was V magnitude 17.352 (June 30.9727 UT, I. Miller (MIW), Swansea, UK), R=15.795 on July 1.0486(MJOD, J. L. Martin, Madrid, Spain), andI=14.469 on July 1.0501 (Martin), but it hasbeen as bright as V=10.868 (June 26.4959, J. Foster (FJQ), Los Angeles, CA) andI=9.102 (June 26.4854 (J. Jones (JJI), Aurora,CA) and could brighten again. To date, 59 AAVSO observersworldwide have contributed 63,478 V, B, R, I, CV, CR, and visual observationsof this outburst of V404 Cyg.
Coordinates: 20 24 03.83 +33 52 02.2(J2000.0)
Charts for V404 Cyg with a comparison star sequence and aphotometry table may be created using the AAVSO Variable Star Plotter (VSP,http:// www.aavso.org/vsp).
Please report observations to the AAVSO InternationalDatabase using the name V404 CYG. Be sure to include error values andcomparison star information.
This AAVSO Alert Notice was compiled by Elizabeth O.Waagen.
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