GCN Circular 33192

A. S. Moskvitin, O. I. Spiridonova and O. A. Maslennikova (SAO RAS),
report on behalf of the GRB follow-up team.

We observed the field of the GRB 230116D (Sonbas et al. GCN #33176)
with the SAO RAS 1-m telescope Zeiss-1000 + CCD-photometer in Rc band
on January 16/17 (21:55:22--00:36:40 UT) and 17/18 (21:42:43--23:31:38).

During the first night the optical afterglow (Zhu et al., GCN #33177;
Nazarov et al., GCN #33178; Moskvitin et al. GCNs #33179, #33187;
Swain et al., GCN #33182; Belkin et al., GCNs #33189, #33190, #33191)
was clearly detected in individual frames and shows complex behaviour.

t-T0, h    R_mag  +/- err     exp, s
0.844      19.967 +/- 0.070   300
0.948      19.888 +/- 0.068   300
1.045      19.874 +/- 0.066   300
1.138      19.818 +/- 0.063   300
1.233      19.674 +/- 0.057   300
1.332      19.595 +/- 0.051   300
1.432      19.701 +/- 0.055   300
1.526      19.668 +/- 0.056   300
1.623      19.779 +/- 0.062   300
1.717      19.764 +/- 0.063   300
1.820      19.728 +/- 0.058   300
1.924      19.626 +/- 0.055   300
2.022      19.539 +/- 0.052   300
2.130      19.709 +/- 0.064   300
2.226      19.798 +/- 0.070   300
2.346      19.870 +/- 0.078   300
2.444      19.976 +/- 0.083   300
2.644      20.021 +/- 0.086   300
2.835      20.065 +/- 0.066   2 x 300
3.041      20.032 +/- 0.063   2 x 300
3.241      20.138 +/- 0.062   2 x 300
3.441      20.223 +/- 0.075   2 x 300

We also obtained 17 x 300 images in Rc band during the second night.
The OT is detected in the stacked frame with the brightness of
R = 22.9 +/- 0.2 (t-T0 = 25.541h = 1.064d) which is in agreement with
upper limit reported by Strausbaugh & Cucchiara (GCN #33188).
Preliminary photometry is based on R2 magnitudes of nearby USNO-B1 stars.