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SMARTS optical re-brightening of GX 339-4

ATel #7977; T. Dincer, C. Bailyn, E. MacPherson (Yale University), E. Kalemci (Sabanci University)
on 1 Sep 2015; 20:49 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Tolga Dincer (tolga.dincer@yale.edu)

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

Referred to by ATel #: 10797

The Swift/XRT observation taken on 27 Aug 2015 showed that the black hole transient GX 339-4 was transitioning back to the hard state after stayed in the soft or soft-intermediate state since January 2015 (ATel #7962). We report the start of a re-brightening in the optical light curves of GX 339-4. Observations are made daily (as the weather permits) with the SMARTS 1.3m telescope at CTIO using the ANDICAM instrument. The source was declining in the optical light curves for the past two months and entered to a steeper declining phase around 21 Aug 2015 (MJD 57255). However, observations of the source between 29 Aug and 02 Sept 2015 (MJD 57263 and MJD 57267) show an increase of d_I=0.3mag and d_V=0.4mag in brightness indicating a start of the re-brightening. Such a re-brightening is often associated with the formation of compact jets and observed when the X-ray spectrum of the source reaches its hardest (Kalemci et al. 2013 ApJ, 779, 95). The SMARTS optical and infrared observations will continue during its current hard state. We encourage further multiwavelength observations. The recent I and V band light curves of the source can be found at http://www.astro.yale.edu/smarts/xrb/plots/GX339-4_2015r.jpg

SMARTS Optical/IR Observations of X-ray Binaries