TITLE: GCN CIRCULAR NUMBER: 37016 SUBJECT: EP240801a: optical observations at CrAO and AbAO DATE: 24/08/02 15:06:19 GMT FROM: Alexei Pozanenko at IKI, Moscow <grb.alex@gmail.com> N. Pankov (HSE, IKI), A. Pozanenko (IKI), V. Rumyantsev (CrAO),R. Ya. Inasaridze (AbAO) report on behalf of GRB-IKI-FuN: We observed the field of EP240801a (Zhou et al, GCN 36997) with ZTSh 2.6 m telescope of CrAO, and AS-32 0.7 m telescope of AbAO. The observations were carried out in moderate conditions with seeing of about 2.0 arcsec. We took a series of images in the R-filter, starting on 2024-08-01 20:28 (UT) at CrAO (i.e. 11 hours after the EP trigger). We clearly detect the optical counterpart (Fu et al, GCN 36998; Li et al, GCN 36999; Zheng et al, GCN 37000; Aryan et al, GCN 37002; An et al, GCN 37004; Pérez-Fournon et al, GCN 37007; Malesani et al, GCN 37008; Zhu et al, GCN 37010; Moskvitin & Spiridonova, GCN 37012; Quirola-Vásquez et al, GCN 37013; Moretti et al., GCN 37014; Turpin et al., GCN 37015) in images from CrAO, while obtaining upper limit at AbAO. Preliminary photometry is given below: Date UT start t-T0 Exp. Filter OT Err. UL(3 sigma) Scope (mid, days) (s) 2024-08-01 20:28:07 0.50492 15x120 R 21.3 0.1 23.7 ZTSh 2024-08-01 20:32:01 0.50970 44x60 R n/d n/d 21.0 AS-32 The magnitudes were calibrated using nearby stars from USNO-B1.0 catalog (R2 mags) and are not corrected for the Galactic extinction A(R) = 0.237 mag (S&F 2011) towards the EP source. The obtained results are consistent with observations published earlier. View this GCN Circular online at https://gcn.nasa.gov/circulars/37016. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...