TITLE: GCN CIRCULAR NUMBER: 13835 SUBJECT: Swift Trigger 535026: Optical decay confirmation with IAC80 and BOOTES-2/TELMA. DATE: 12/10/02 00:35:53 GMT FROM: Javier Gorosabel at IAA-CSIC J.C. Tello (IAA-CSIC), R. Gimeno (IAC), J. Gorosabel (IAA-CSIC), M. Jelinek (IAA-CSIC), R. Sanchez-Ramirez (IAA-CSIC), A.J. Castro-Tirado (IAA-CSIC), report on behalf of a larger collaboration: "We observed the field of Swift trigger 535026 (D'Elia et al. GCN 13831) with the 82cm IAC80 telescope at the Observatorio del Teide, Tenerife, Spain. The observations were carried out in the I-band on 19:38--21:32 UT (starting 1.25 hours post burst) with a total exposure time of 18x240s. An optical source placed at RA(J2000)=18:24:07.88 DEC(J2000)=-05:39:55.0 (+/-0.9") shows a clear decay from I~19 to I~20 (Vega), against the USNO B1.0 catalogue. The coordinates of this source are consistent with the XRT error circle (GCN 13831) and the possible optical counterpart reported by Andreev et al. (GCN Circ. 13833). The object is also detected with the BOOTES-2/TELMA telescope at I~19.7 (Vega) at 20:49--21:52 UT Oct. 1."