X-ray and Optical Activity in V4641 Sgr (=SAX 1819.3-2525)
ATel #171; C. Bailyn, D. Maitra, M. Buxton, L. Jeanty (Yale), D. Gonzalez (CTIO)
on 6 Aug 2003; 22:55 UT
Credential Certification: Dipankar Maitra (maitra@astro.yale.edu)
Subjects: Infra-Red, Optical, X-ray, Black Hole, Transient
Referred to by ATel #: 172, 175
V4641 Sgr is now active in X-rays, and activity continues in optical/IR bands. A ~1 kilosecond
dwell with the RXTE/PCA taken August 5 2003 starting at UT 01:18 shows flux varying from 20 to
35 mCrabs. On August 6 between UT 08:43 - 09:31 the source was in a highly active flaring state, with flares of up to 100 mCrabs erupting on timescale of 10-30 seconds. Observations on August 6 from
UT 10:23 - 11:13 did not show large flares, but rather a state similar to that observed in the
August 5 dwell. Similar activity was also seen in optical/IR observations by the SMARTS consortium, using the 1.3m telescope at CTIO with the ANDICAM instrument. On August 6 the source brightened in the
V band from magnitude 12.4 to 10.9 between UT 00:00 and UT 05:15. The source became somewhat bluer during this rise: over the same period the K band brightened by only 1.1 magnitudes. Flares and dips of several tenths of a magnitude were observed on timescales of <3 minutes.
