The novalike/VY Scl variable V380 Oph is in its low state and is undergoing a deep fading, according to observations by Adolfo Darriba Martinez on 2015 July 4 and 5 reported via VSNET, CBA, and to the AAVSO International Database.
Dr. Joseph Patterson (Columbia University) writes: "[T]his seems to be a *fresh* fading - so in theory, it's now a bare white dwarf and an orbiting M dwarf. If the WD is hot (it should be), then the reflection effect off the M dwarf should produce a sinusoidal signal at Porb. So the amplitude of the signal furnishes a bolometer for the WD. It's an experiment we rarely get to do, because the accretion disk normally *shadows* the secondary from (most) WD light. So it's a great target for time-series photometry."
V380 Oph ranges from V~14.7 in its high state to as faint as V=19.3-19.4 in its low state. During this fading, AAVSO observers L. Cook (COO, Concord, CA) and G. Myers (MGW, Hillsborough, CA) have reported it as faint as CV=19.468 and CV=19.325, respectively.
The most recent observations reported to the AAVSO show it varying between CV = 18.694(100) and 18.993(109) on 2015 July 9.94917- 10.05814 UT (DAM, A. Darriba Martinez, Madrid, Spain).
CCD observers are requested to carry out time-series observations of V380 Oph. Due to the faintness of the target, unfiltered observations may be required, and are acceptable. Please clearly identify the comparison stars and magnitudes used for calibration.
Coordinates: RA 17 50 13.64 Dec. +06 05 29.4 (2000.0)
Finder charts with a sequence for V380 Oph may be created using the AAVSO Variable Star Plotter (VSP, http://www.aavso.org/vsp). A photometry table of the sequence is also available via VSP.
Please report your observations of V380 Oph to the AAVSO International Database via WebObs using the name "V380 OPH".
This AAVSO Special Notice was prepared by Elizabeth O. Waagen.
The dramatic outburst of the black hole X-ray transient LMXB V404 Cyg continues. It was detected 2015 June 16.1688 UT at 16.18 CV +/-0.035 by E. Muyllaert (MUY, Oostende, Belgium); the first satellite 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 community across the spectrum from X-ray to radio wavelengths, and by the amateur community in all bands available to it. Large- and small-scale variations have been seen occurring at timescales ranging from seconds to hours, with changes of 2-3 magnitudes seen over the course of a few hours. Most recently Swift has detected 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 observations of V404 Cyg with the Hubble Space Telescope have been scheduled for 2015 July 10, 11, and 12 according to the schedule below:
FUV: 10 Jul 2015 12:12:19 - 19:23:20 UTC NUV: 11 Jul 2015 13:37:07 - 16:08:55 UTC FUV: 12 Jul 2015 11:56:15 - 19:08:08 UTC
The HST observations were scheduled for the satellite's earliest availability, and the timing is best for ground-based locations from the western US and eastern Asia.
Regardless of location, all observers are requested to continue to observe V404 Cyg. Time-series observations are requested during as much of the HST observation intervals as possible, in as many bands as possible. A high cadence is recommended in order to detect the very short-period variations that have been seen.
Observations in the AAVSO International Database show that 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), and I=14.469 on July 1.0501 (Martin), but it has been as bright as V=10.868 (June 26.4959, J. Foster (FJQ), Los Angeles, CA) and I=9.102 (June 26.4854 (J. Jones (JJI), Aurora, CA) and could brighten again. To date, 59 AAVSO observers worldwide have contributed 63,478 V, B, R, I, CV, CR, and visual observations of 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 a photometry table may be created using the AAVSO Variable Star Plotter (VSP, http:// www.aavso.org/vsp).
Please report observations to the AAVSO International Database using the name V404 CYG. Be sure to include error values and comparison star information.
This AAVSO Alert Notice was compiled by Elizabeth O. Waagen.