1 Introduction

The error box of the BATSE gamma-ray burst GRB 970616 (Connaughton et al. 1997) was scanned by RXTE four hours after the event (Marshall et al. 1997). Observations revealed a previously unknown X-ray source inside the error box whose position was consistent with the one provided later on by the Interplanetary Network (IPN), yielding a combined RXTE/IPN trapezoidal error box (Hurley et al. 1997). Four days later, the ASCA satellite observed the RXTE/IPN error box and detected four X-ray sources. One of them, A#1 according to the nomenclature of Murakami et al. (1997), was suggested as the X-ray counterpart to GRB 970616. Two candidates were initially proposed by Galama et al. (1997) and Udalski (1997), but other observers (Pahre et al. 1997; Dey et al. 1997; Wheeler et al. 1997; Castro-Tirado et al. 1997) failed to confirm these. Observations performed by ROSAT during June 23-25 revealed eleven faint X-ray sources, lying three of them within the RXTE/IPN error box. One of the three sources, R#2, following Greiner et al. (1997), was consistent with the ASCA variable source A#1, showing a flux five times lower than the one measured by ASCA. The 3$\sigma$ upper limit to the unabsorbed ROSAT flux of the source A#4, implies a factor of seven lower than the previously measured by ASCA. The fading observed during the ASCA observation could suggest that A#1 is the X-ray counterpart to the GRB. However, the presence of another decaying X-ray source inside the RXTE/IPN error box keeps open the association with the GRB. A massive cluster of galaxies $2^{\prime}$ away from the RXTE/IPN error box is reported by Benítez et al. (1999). Figure 1 shows the locations of the cluster and of the candidates proposed by Galama et al. (1997) and Udalski (1997).