TITLE:   GCN CIRCULAR
NUMBER:  20300
SUBJECT: GRB 161219B: LCO Sutherland observations
DATE:    16/12/20 08:31:43 GMT
FROM:    Cristiano Guidorzi at Ferrara U,Italy  <guidorzi@fe.infn.it>

C. Guidorzi (U. Ferrara), S. Kobayashi, I.A. Steele (LJMU), A. Gomboc 
(U. Nova Gorica), C.G. Mundell (U. Bath) on behalf of a large 
collaboration report:

We observed Swift GRB 161219B (D'Ai et al. GCN 20296) on December 19, 
from 20:43 to 20:56 UT (1.9-2.1 hours since the GRB) with 1-m LCO 
telescope units in Sutherland with SDSS r and i filters. Within the 
enhanced enhanced XRT error circle (Beardmore et al. GCN 20297) we 
clearly detect the optical counterpart reported by UVOT (D'Ai et al.) 
with the following values:

Mid Time      Exposure       Filter       Magnitude
(hours)           (s)
-------------------------------------------------------
1.93              120         SDSS-R      17.38 +- 0.02
1.93              120         SDSS-I      16.72 +- 0.02
-------------------------------------------------------

as calibrated against nearby USNOB-1 source RA(J2000)=06:06:52.743, 
DEC(J2000)=-26:46:29.49 using nominal R2=15.12 mag, I=14.37 mag.
We however point out that the source is positionally coincident with a 
USNOB-1 source: 06:06:51.366, -26:47:29.80, which has nominal R2=20.14 
mag. This likely corresponds to the extended galaxy mentioned by 
Kruehler et al (GCN 20299) in Pan-STARRS data.