TITLE:   GCN CIRCULAR
NUMBER:  39436
SUBJECT: EP250223a: NOT optical afterglow candidate
DATE:    25/02/23 21:46:49 GMT
FROM:    Andrew Levan at Radboud University <a.levan@astro.ru.nl>

Benjamin N. Hauptmann (NOT and DTU Space), Yfke Bethlehem (Kapteyn Astronomical Institute, Groningen, and ING), Andrew J. Levan (Radboud and Warwick), Daniele B. Malesani (DAWN/NBI and Radboud), Antonio Martin-Carrillo (UCD), Franz E. Bauer (PUC), Peter G. Jonker (Radboud) and Dong Xu (NAOC), report on behalf of a larger collaboration:

We observed the location of EP250223a (Lian et al. GCN 39429) with the Nordic Optical Telescope (NOT). Observations in the r-band began at 20:36 UT, approximately 5.53 hr after the trigger time. In the first 300 s exposure we clearly detect a new point source, not visible in archival DSS and Pan-STARRS imaging of this field, at a location of 

RA(J2000) = 06:33:05.723
DEC(J2000) = -22:26:40.32

These coordinates are within the FXT X-ray uncertainty region, making this source the likely afterglow of EP250223a.

The source has an AB magnitude r = 19.7, calibrated against nearby Pan-STARRS objects. Further observations are in progress.