TITLE: GCN CIRCULAR NUMBER: 41388 SUBJECT: GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit DATE: 25/08/15 10:13:58 GMT FROM: Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, Messina, Italy <giovannicalapai@tiscali.it> Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, (Messina) Italy Member of: GRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani. Report: We imaged the field of GRB 250813B detected by SVOM/ECLAIRs telescope (Xie et al. GCN 41352 - 41354), with the 11 inches Schmidt-Cassegrain (Celestron 11) telescope F/D=6,3. The observations were started at 2025-08-14 00:02 UT (approximately 1.19 hours after burst) stacking a set of unfiltered CCD image. The observations were carried out with partially clear skies and Moon (illumination: 74%, distance: 42°). We co-added 93 exposures of 60 sec each. Start T0+ End T0+ CR lim 1.19 hour 4.44 hour 20.1 We did not found any optical counterpart in the error box of the XRTcandidate (Page et al. GCN 41359). Magnitudes were estimated with the PanSTARRS cat. and are not corrected for galactic dust extinction. Our observations are consistent with other already reported Jelinek et al. (GCN 41355), Gill et al. (GCN 41356), Corcoran et al. (GCN 41370). The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/41388. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...