EDP Sciences
Free access
Volume 389, Number 1, July I 2002
Page(s) L11 - L14
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20020650

A&A 389, L11-L14 (2002)
DOI: 10.1051/0004-6361:20020650


The infrared counterpart of the X-ray burster KS 1731-260

R. P. Mignani1, S. Chaty2, I. F. Mirabel3, 4 and S. Mereghetti5

1  ESO, Karl Schwarzschild Str. 2, 85748 Garching bei München, Germany
2  The Open University, Department of Physics and Astronomy Walton Hall, Milton Keynes, MK7 6AA, UK
3  Service d'Astrophysique / CEA, CE-Saclay, 91191 Gif-sur-Yvette, France
4  Instituto de Astronomía y Física del Espacio/CONICET. cc5, 1428 Bs As, Argentina
5  Istituto di Astrofisica Spaziale e Fisica Cosmica CNR, Sezione di Milano "G.Occhialini", via Bassini 15, 20133 Milano, Italy

(Received 8 March 2002 / Accepted 26 April 2002 )

We present JK' 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 $K' = 16.36 \pm 0.18$. 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.

Key words: X-ray binaries, KS 1731-260

Offprint request: R. P. Mignani, rmignani@eso.org

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