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V380 Oph in low state
The novalike/VY Scl variable V380 Oph is in its low stateand is undergoing a deep fading, according to observations by Adolfo DarribaMartinez on 2015 July 4 and 5 reported via VSNET, CBA, and to the AAVSOInternational 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 thereflection effect off the M dwarf should produce a sinusoidal signal atPorb. So the amplitude of the signalfurnishes a bolometer for the WD. It'san experiment we rarely get to do, because the accretion disk normally*shadows* the secondary from (most) WD light. So it's a great target fortime-series photometry."
V380 Oph ranges from V~14.7 in its high state to as faintas V=19.3-19.4 in its low state. During this fading, AAVSOobservers L. Cook (COO, Concord, CA) and G. Myers (MGW, Hillsborough, CA) havereported it as faint as CV=19.468 and CV=19.325, respectively. The most recent observations reported to the AAVSO show itvarying 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-seriesobservations of V380 Oph. Due to thefaintness of the target, unfiltered observations may be required, and areacceptable. Please clearly identify thecomparison stars and magnitudes used for calibration.
Coordinates: RA 1750 13.64 Dec. +06 05 29.4 (2000.0)
Finder charts with a sequence for V380 Oph may be createdusing 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 AAVSOInternational Database via WebObs using the name "V380 OPH".
This AAVSO Special Notice was prepared by Elizabeth O.Waagen.
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發表於 2015-7-16 08:48:49