TITLE:   GCN CIRCULAR
NUMBER:  36059
SUBJECT: EP240408a: GROND detection of a candidate counterpart
DATE:    24/04/10 09:18:25 GMT
FROM:    Arne Rau at MPE <arau@mpe.mpg.de>

Arne Rau (MPE):

We observed the position of EP240408a (Hu et al., #GCN 36053; #36057) with the Gamma-ray Burst Optical Near-ir Detector (GROND, Greiner et al. 2008) starting on April 10, 2024, 04:14:09 UTC. A faint source is detected in the Swift/XRT error circle located at  RA = 10:35:24.30 Dec = -35:44:47.9 with an uncertainty of 0.2” in both coordinates.

The source is detected in the J and H bands at the following AB magnitudes:

J= 19.9 +/- 0.3
H= 20.5 +/- 0.5

The photometric uncertainties are dominated by a very bright point source ~20 arcsec from the optical/NIR counterpart.

We note that the source is also visible in the z-band data of the Legacy Survey DR10 (https://www.legacysurvey.org/).

We thank the 2.2m staff member, Angela Hempel, for the rapid execution of the observation.