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Flare at OIR wavelengths in GX 339-4

ATEL # 1109; Michelle Buxton (Columbia University) and Charles Bailyn (Yale University)
on 14 Jun 2007; 18:39 UT
Password Certification: Michelle Buxton (

Subjects: Infra-Red, Optical, Binaries, Black Holes, Transients

We have continued our observations of GX 339-4 with the SMARTS 1.3m and ANDICAM instrument since the source transitioned into the hard state around MJD 54233 (13th May 2007, ATEL #1074). The optical and infrared (OIR) fluxes reached a minimum at MJD 54239, and then began to rise. Since that time the brightness of the source has increased as follows:

Filter Mag at MJD 54239 Mag at MJD 54260 Delta (mag)
V 17.6 17.0 0.6
I 16.7 15.8 0.9
J 15.5 14.0 1.5
H 15.0 13.3 1.7

The large increase in the infrared implies that this is likely an IR-dominated flare, like that seen for example in 4U1543-47 (Buxton & Bailyn 2004 ApJ 615, 880). The latest observations suggest that the OIR fluxes may now have peaked. Observations in other wavelengths, especially infrared and radio, are strongly encouraged.

A plot of our lightcurves can be found at the URL provided below.

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R. E. Rutledge , Editor
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