TITLE: GCN CIRCULAR NUMBER: 37584 SUBJECT: EP240913A/GRB 240913C: AbAO optical upper limit DATE: 24/09/21 10:33:25 GMT FROM: Alexei Pozanenko at IKI, Moscow <grb.alex@gmail.com> S. Belkin (HSE, IKI), R. Ya. Inasaridze (AbAO), A. Pozanenko (IKI), N. Pankov (HSE, IKI) report on behalf of GRB-IKI-FuN: We observed the field of EP240913A/GRB 240913C (Li et al., GCN 37492; Yin et al., GCN 37493; Dasgupta et al., GCN 37505; Bissaldi et al., GCN 37509; Pawar et al., GCN 37510) using the 70-cm AS-32 telescope at the Abastumani Observatory (AbAO) in the R-filter, starting on 2024-09-14 at 23:44:17 (UT). We did not detect the optical counterpart in the stacked image within the Swift-XRT error circle (Jiang et al., GCN 37497), consistent with reports from Asquini et al., GCN 37499; Zhu et al., GCNs 37500, 37501; Zheng et al., GCN 37511; Schneider et al., GCN 37515; Lipunov et al., GCN 37521. Preliminary photometry is as follows: Date UT Start t-T0 (days) Filter Exposure (s) OT Err UL (3σ) 2024-09-14 23:44:17 1.53211 R 113×60 n/d n/d 22.2 The magnitudes were calibrated using nearby USNO-B1.0 stars: RA: 01:06:52.7994912, DEC: +16:43:24.121128, R2: 15.96 RA: 01:07:11.4427176, DEC: +16:49:54.951564, R2: 17.09 View this GCN Circular online at https://gcn.nasa.gov/circulars/37584. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...