TITLE:   GCN CIRCULAR
NUMBER:  38618
SUBJECT: EP241217a: REM optical/NIR upper limits
DATE:    24/12/18 13:50:59 GMT
FROM:    Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>

R. Brivio, M. Ferro, P. D’Avanzo (INAF-OAB), D. B. Malesani (DAWN/NBI and Radboud Univ.), S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team:
We observed the field of EP241217a (Zhou et al., GCN 38586), also detected by Swift-XRT (Williams et al., GCN 38596) 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, J, H, K bands, starting on 2024 December 18 at 00:45:27 UT (i.e. 19.1 hours after the EP-WXT trigger), and lasting for about 1 hour.

From preliminary photometry we do not detect any counterpart in the optical and NIR images at the position of the optical afterglow (Levan et al., GCN 38587; Izzo & Malesani, GCN 38588; Fan et al. GCN 38592; Mohan et al., GCN 38612; Zhu et al., GCN 38613; Bochenek & Perle, GCN 38615) down to the following 3sigma magnitude upper limits:

r > 20.8 (AB; calibrated against the Pan-STARRS catalogue)
at a mid-time of t - t0 = 19.6 hr after the trigger,

H > 16.6 (Vega; calibrated against the 2MASS catalogue) 
at a mid-time of t - t0 = 19.5 hr after the trigger.