TITLE: GCN CIRCULAR NUMBER: 44994 SUBJECT: EP260618a: OHP/T193 optical observations DATE: 26/06/19 11:05:46 GMT FROM: Christophe Adami at LAM <christophe.adami@lam.fr> P. Amram (LAM/Pytheas/AMU), C. Adami (LAM/Pytheas/AMU), D. Russeil (LAM/Pytheas/AMU) report on behalf of a larger collaboration: We observed the field of EP260618a (Yang et al., GCN44978; see also Fermi GBM Team , GCN44973 and Jiang et al., GCN44991) using the T193cm telescope at Observatoire de Haute-Provence (France) with the MISTRAL spectro-imager. We obtained 2x10 minutes of exposure in the r-band starting at 2026-06-18T21:12:40 UT (12.63 hr after the Yang et al. trigger). In the stacked images, the optical counterpart detected by Becerra et al. (GCN44988) and Malesani et al. (GCN44990) is visible with preliminary magnitude of: r = 21.86 +/- 0.09 mag in good agreement with their measurements. The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the STDWeb/STDPipe tools (Karpov 2025), is in the AB system, and is not corrected for Galactic extinction. We acknowledge the excellent support from Observatoire de Haute-Provence and in particular Stephane Favard. We acknowledge the excellent support of J. Schmitt and J.C. Brunel in the recent MISTRAL upgrade. View this GCN Circular online at https://gcn.nasa.gov/circulars/44994. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...