AAVSO Special Notice #404
July 10, 2015
V380 Oph in low state
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.
AAVSO Alert Notice 522