GCN Circular 42839
Subject
EP251124b: NOT r- and z-band optical upper limits
Event
Date
2025-11-26T00:24:55Z (2 days ago)
From
Agnes van Hoof at Radboud University <agnes.vanhoof@ru.nl>
Via
Web form
A. P. C. van Hoof (Radboud), G. Corcoran (UCD), J. N. D. van Dalen, A. Martin-Carrillo (UCD), D. Xu (NAOC), S.Q. Jiang (NAO, CAS), T. Pursimo (NOT, Aarhus University), J.P.U. Fynbo (DAWN/NBI), P. G. Jonker (Radboud) report on behalf of a larger collaboration:
We observed the field of the fast X-ray transient EP251124b (Feng et al., GCN 42834) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations were obtained in the r (3x300 s) and z (5x200 s) bands, starting on 2025-11-25 at 22:19:58.38 UTC (1.2 days after the WXT trigger).
No new source is detected within the EP/WXT uncertainty region (Feng et al., GCN 42834). From the stacked images we obtain the following 3-sigma upper limits:
r > 24.4
z > 23.2
These upper limits are in AB magnitudes and were calibrated using nearby stars from the Pan-STARRS catalog and are not corrected for Galactic extinction.
We also performed image subtraction in r band using a reference image from the Legacy Survey. No new source is revealed compared to the reference. However, we note that there are artefacts across the field.