ИСТИНА

We present the results of optical photometry of the X-ray transient XTE J2123-058. CCD R-band images, have been obtained since 2 Jul until 29 Sep 1998. Following the behaviour of the XTE/ASM lightcurve, the system decline optically from the begining of August at approximately 0.1 mag/day. Despite the drop in luminosity, we observe a dramatic increase in orbital modulation. Full cycles were recorded during the outburst, showing an almost sinusoidal modulation consistent with X-ray heating of the companion star, and narrow dips superposed at phases 0 and 0.5 which could be asociated to mutual eclipses between the companion star and accretion disc. We also noted on 26 Aug the sistem has reached quiescence, showing an average magnitude of R=21.5, which is consistent with the pre-outburst photographic magnitude estimated. Our last data suggest the presence of ellipsoidal modulation from the companion star.