TITLE:   GCN CIRCULAR
NUMBER:  23699
SUBJECT: GRB 190114C: OASDG optical observations
DATE:    19/01/15 01:01:57 GMT
FROM:    Luca Izzo at IAA-CSIC  <luca.izzo@gmail.com>

L. Izzo (HETH/IAA-CSIC), A. Noschese, L. D’Avino and M. Mollica (AC-OASDG) report:

We observed the field of GRB 190114C (Gropp et al. GCN 23688) with the 0.5m telescope of the Osservatorio Astronomico S. Di Giacomo located in Agerola, Italy ( https://goo.gl/Dqvqhf ). Observations were carried out under bad weather conditions and with the GRB position initially at 15 degrees above the horizon.

We obtained a series of 180 s images in the Rc filter, starting at 21:29:23 UT, ~ 0.54 hrs after the GRB detection. The GRB is clearly detected in the first image at the position of the observed optical counterpart (Tyurina et al. GCN 23690, Lipunov et al. GCN 23693, Selsing et al GCN 23695), but it is rapidly fading in the following images. We have stacked our set of images in groups of two images each, measuring the following magnitudes (AB):

Time   Rc          dRc
(hrs)   (mag)     (mag)

0.54   16.86      0.07
0.65   17.06      0.07
0.74   17.21      0.08
0.86   17.27      0.08
0.97   17.47      0.09
1.07   17.69      0.10

The calibration was performed using nearby stars in the Pan-STARRS PS1 catalog and using transformation equations to Rc magnitudes.