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OIR activity in V4641 Sgr

ATel #542; M. Buxton, C. Bailyn, D. Maitra (Yale University)
on 30 Jun 2005; 15:31 UT
Credential Certification: Michelle Buxton (buxton@astro.yale.edu)

Subjects: Infra-Red, Optical, Binary, Black Hole, Transient

We have obtained V- and H-band images of V4641 Sgr using the ANDICAM instrument on the SMARTS 1.3m telescope at CTIO. Images taken on UT 2005 June 26.3 show that V4641 had significantly increased in brightness with respect to average quiescent magnitudes. The H-band magnitude for this time was 11.6 and V-H = 1.63. Data taken on UT 2005 June 29.2 and 30.3 indicate that V4641 Sgr has returned to average quiescent magnitude levels in both V- (~ 13.7 mag) and H-band (~ 12.6 mag) with V-H = 1.1. We will continue to monitor this object at optical and infrared wavelengths on a daily basis (weather permitting).