TITLE:   GCN CIRCULAR
NUMBER:  35803
SUBJECT: Transient EPW20240219aa: REM optical/NIR upper limits
DATE:    24/02/26 19:27:31 GMT
FROM:    Matteo Ferro <matteo.ferro@inaf.it>

M. Ferro, R. Brivio, Y.-D. Hu, P. D’Avanzo, S. Covino, D. Fugazza (INAF-OAB) on behalf of the REM team, report:

We observed the field of the transient EPW20240219aa (Zhang et al., ATel 16463; Zhang et al., ATel 16472;  Zhang et al., GCN 35773) with the REM 60cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, H bands, starting on 2024 February 25 at 00:16:54 UT (i.e. 5.75 days after the event), and lasting for about 20 minutes. 
We find no clear afterglow candidate within the Einstein Probe error circle, nor at the positions of the radio sources reported by Ho et al. (GCN 35788), down to the following 3sigma magnitude upper limits:

H > 17.3 (Vega; calibrated against the 2MASS catalogue)

r > 19.9  (AB; calibrated against the Pan-STARRS catalogue)

at the common mid-time of t - t0 = 5.75 days after the EP trigger.

We report a detection of VLA sources #6 and #7 in the co-added REM H-band image with magnitudes H ~ 16.7 and H ~ 16.5, respectively (AB). We note however that both sources are reported in the UKIDSS survey with similar magnitudes.