GCN Circular 23665

M. Blazek, D. A. Kann (both HETH/IAA-CSIC), A. de Ugarte Postigo 
(HETH/IAA-CSIC and DARK/NBI), L. Izzo, and K. Bensch (all HETH/IAA-CSIC) 
report:

We observed the optical afterglow of GRB 190106A (e.g., Yurkov et al., 
GCN #23614), detected by Swift (Sonbas et al., GCN #23615), with with 
the T150 telescope of the Sierra Nevada Observatory (OSN). We obtained 
18 x 300 s images in the Ic band from 5.02 to 6.47 hours after the GRB. 
The afterglow is well-detected in each single image. We find it decays 
between the beginning and end of our observing run.

Days	Ic mag	error

0.2091	18.54	0.05
0.2696	18.73	0.06

Magnitudes are given in the AB system. They were measured vs. four SDSS 
comparison stars, using the transformation equations of Lupton (2005), 
and transformed back into AB mags.