TITLE:   GCN CIRCULAR
NUMBER:  22536
SUBJECT: GRB 180325A: prompt REM optical/NIR detection
DATE:    18/03/25 03:50:18 GMT
FROM:    Paolo D'Avanzo at INAF-OAB  <paolo.davanzo@brera.inaf.it>

P. D'Avanzo, A. Melandri, S. Covino, D. Fugazza (INAF/OAB) report on behalf of the REM team:

We observed the field of the GRB 180325A (Troja et al., GCN 22532) with the 60-cm robotic telescope REM located at the La Silla Observatory (Chile).  
The observations started on 25-03-2018 at 01:53:52 UT, 50s after the burst, and were carried in the g, r, i, z, J, H and K bands.

A preliminary analysis shows that the optical counterpart (Troja et al., GCN 22532; Guidorzi et al. GCN 22534; Heintz et al. GCN 22535) is well detected 
and at a mid time of 123 seconds after the burst it was:

r = 17.2 +/- 0.2 (AB)
H = 12.7 +/- 0.1 (Vega)

Magnitudes are calibrated against the SDSS (optical) and 2MASS (NIR) catalogues.