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Date: Thu, 07 Aug 2003 22:59:43 +0200
From: Rashid Sunyaev <sunyaev@MPA-Garching.MPG.DE>
Subject: Rapid optical variability of V4641 Sgr (=SAX J1819.3-2525)
Rapid optical variability of V4641 Sgr (=SAX J1819.3-2525)
ATEL # 174; I.Khamitov, Z.Aslan (TUG), K.Yakut (EgeU),
I.Bikmaev, R.Gumerov, N.Sakhibullin (KSU), R.Sunyaev,
M.Revnivtsev (IKI, MPA), M. Pavlinsky (IKI)
on 7 Aug 2003; 20:11 UT
Distributed as an Instant Email Notice (Request for Observations)
Password Certification: M. Revnivtsev (mikej@mpa-garching.mpg.de)
Subjects: Optical, Request for Observations, Binaries, Black Holes,
Transients
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
Bakyrlytepe during the period 19:01-22:16 UT, Aug. 6, 2003.
The Rc magnitude of the source averaged over all observations
was m_Rc~11.7. Time resolution of the photometric data is 9.7 sec.
The observed light curve demonstrates strong aperiodic variability
at all time scales, from tens of seconds to hours. Several spikes
weer observed with duration of the order of a minute and amplitudes
up to 1 magnitude. Power spectrum of the optical flux variations
could be described by a power law with the slope -1.8 in the
frequency band 1e-4 - 0.04 Hz.
Lightcurve of V4641 Sgr is given at ATEL.caltech.edu
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