Optical observations of V4641Sgr
ATel #297; M. Revnivtsev (IKI, MPA), I. Khamitov(TUG), R. Burenin(IKI),M. Pavlinsky(IKI),R. Sunyaev (IKI, MPA), Z. Aslan(TUG), I. Bikmaev(KSU),N. Sakhibullin(KSU)
on 6 Jul 2004; 11:45 UT
Credential Certification: M. Revnivtsev (mikej@mpa-garching.mpg.de)
Subjects: Optical, Request for Observations, Black Hole
Referred to by ATel #: 303
The X-ray binary system V4641 Sgr (=SAX J1819.3-2525) was observed in
Rc band with the 1.5-m Russian-Turkish telescope RTT150 at TUBITAK
National Observatory (Turkey) during the period 18:57-21:57 UT, July 5, 2004.
The Rc magnitude of the source averaged over all observations was
m_Rc~13.5, that is slightly higher than that in its quiescent state at
this orbital phase. We obtained a lightcurve with time resolution 13.5 sec.
Along with stable trend, likely caused by the orbital variations of the system
brightness there was detected chaotic variability at time scales
~1000 sec. Power spectrum of such variations can be described by a power
law with the slope -1.5 in the frequency band 10^-4-3x10^-3 Hz
(http://db.rsdc.rssi.ru/V4641Sgr/2004/ps.pdf)
V4641 Sgr at this stage obviously lacks the violent variability
that it demonstrated in Aug. 2003 (see ATEL #174)
Historical phase light curve of V4641 Sgr with overplotted July 5, 2004
observations http://db.rsdc.rssi.ru/V4641Sgr/2004/20040705_0.jpg
Lightcurve of V4641Sgr on July 5, 2004
