TITLE: GCN CIRCULAR NUMBER: 45245 SUBJECT: EP260727a: 1.5m OSN optical counterpart detection DATE: 26/07/28 19:45:10 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct@iaa.es> S. Guziy, J. Rodrigo, E. Fernandez-Garcia, A. J. Castro-Tirado, S.-Y. Wu, I. Perez-Garcia, M.D. Caballero-Garcia and M. Gritsevich (IAA-CSIC), G. Garcia-Segura (UNAM) and Y.-D. Hu (GXI), on behalf of a larger collaboration, report: Following the detection of EP260727a by Einstein Probe (Hu et al. GCN 45235), we triggered the 1.5m telescope at Sierra Nevada Observatory (OSN) in Granada (Spain) starting on July 27, 23:51 UT (~3.24 h post trigger) in the Ic-band. The optical counterpart in the r-band proposed by He et al. (GCNC 45234) and also detected in z-band by Eyles-Ferris (GCNC 45239), and Adami et al. (GCNC 45243), is recorded in our images as well. We measure Ic=21.76+-0.26 on a 12x300s coadded image (July 28, 00:16 UT, mid exposure time). The additional candidate reported by Adami et al. (GCGC 45243) is not detected on our images (taken ~1 h earlier) down to Ic=21.9 limiting magnitude. Further optical monitoring is ongoing. We thank the staff at OSN for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/45245. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...