TITLE: GCN CIRCULAR NUMBER: 36497 SUBJECT: GRB 240502C: Zeiss-1000 at Koshka observations of GOTO24bao optical counterpart candidate DATE: 24/05/16 16:13:56 GMT FROM: Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru> A. Volnova (IKI), A. Novichonok (Petrozavodsk State University, KIAM), A. Pozanenko (IKI), S. Belkin (IKI), N. Pankov (HSE) report on behalf of GRB IKI FuN: We observed GOTO24bao (Gompertz et al., GCN 36380; Belkin et al., GCN 36395), a possible optical counterpart of the GRB 240502C (Fermi GBM Team, GCN 36376) with the Zeiss-1000 telescope of Koshka observatory in R-filter on 2024-05-05/06. The preliminary photometry of stacked images in all epochs is as follows Date UT start t-T0 Exp. Filter OT Err. UL (3sigma) (mid, days) (s) 2024-05-03 20:58:29 0.99542 15x120 R 19.02 0.06 21.1 2024-05-05 18:58:54 2.89875 8x300 R 18.73 0.04 21.3 2024-05-06 20:48:24 3.97479 8x300 R 18.98 0.04 21.8 Ref. stars USNO-B1.0 RA DEC R2 09:57:18.15288 +62:02:45.8412 17.46 09:56:49.99872 +62:01:39.1620 14.74 09:57:14.13480 +61:59:47.1624 16.44 The magnitude of the (possible OT + host) on May 5 is somewhat but significant) brighter than in adjacent epochs, indicating the presence of variability of the OT. Till now we cannot confirm the association of the candidate GOTO24bao with an GRB 240502C afterglow. View this GCN Circular online at https://gcn.nasa.gov/circulars/36497. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...