TITLE: GCN CIRCULAR NUMBER: 41680 SUBJECT: EP250903a: LCO candidate counterpart discovery DATE: 25/09/03 18:47:51 GMT FROM: Andrew Levan at Radboud University <a.levan@astro.ru.nl> A. J. Levan (Radboud and Warwick), J. A. Quirola-Vasquez (Radboud), D. B. Malesani (DAWN/NBI and Radboud), G. Corcoran (UCD), A. Martin-Carrillo (UCD), R. A. J. Eyles-Ferris (Leicester), P. G. Jonker (Radbound), F. E. Bauer (SSI and UTA), and J. Chacón (PUC) report on behalf of a larger collaboration: We observed the location of EP250903a (Zhao et al. GCN 41674) with the Sinistro instrument mounted on the 1-m telescopes at the LCO Siding Springs Observatory. 3 x 300 s exposures were obtained in the SDSS r filter at a start time of 14:44:15 UT on 2025-09-03 (~41 minutes post trigger). Within the WXT and FXT error circles we locate a new source in our stacked r-band image with r~21 mag (AB) calibrated against nearby SkyMapper stars and not corrected by Galactic extinction, at a location of RA(J2000): 22:36:27.75 DEC(J2000): -49:51:25.6 The error is about 0.5” in each coordinate. We note the transient is offset ~1” from a Legacy survey object with magnitude r= 21.49 mag which has a photometric redshift of 0.24 +/- 0.11. In the legacy images the source appears to extend underneath the new source. Thus, our photometry likely includes some contribution from the host galaxy. View this GCN Circular online at https://gcn.nasa.gov/circulars/41680. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...