We present JK ^ { \prime } infrared images of the X-ray transient KS 1731–260 , obtained in 1997 and in 1998 with IRAC2b at the ESO/MPI 2.2-m telescope at La Silla .
Using as a reference the recent Chandra position , we confirm the identification of the X-ray source with the previously proposed counterpart ( Wijnands et al .
2001b ) , for which we measure J = 17.32 \pm 0.2 and K ^ { \prime } = 16.36 \pm 0.18 .
The source was entering a low X-ray state at the epoch of our observations , and the accretion disk was still dominating the infrared flux .
Indeed , when compared with the only published magnitudes in the J -band ( Orosz et al .
2001 ) , obtained with the source in quiescence , our photometry confirms the fading of the counterpart during the decay of the RXTE/ASM lightcurve .