[vsnet-grb-info 18854] GRB 161219B: Watcher optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  20305
SUBJECT: GRB 161219B: Watcher optical observations
DATE:    16/12/20 14:15:30 GMT
FROM:    Antonio Martin-Carrillo at UCD,Space Science Group  <antonio.martin-carrillo at ucd.ie>

A. Martin-Carrillo (UCD), D. Murphy (UCD), L. Hanlon (UCD), H. J. van Heerden (UFS), B. van Soelen (UFS) and P. J. Meintjes (UFS)

We observed the field of GRB 161219B (D'Ai et al, GCN 20296) using the 40cm UCD Watcher telescope at Boyden Observatory in South Africa.

Due to bad weather, observations were delayed until December 20th at 00:30 UT (T0+5.67h) and were taken under poor seeing. Based on combined images in SDSS r’ filter, at a mid-time of 00:45 UT we derive a preliminary magnitude of r'=18.06 (AB system). This value is in agreement with the magnitude reported by Kruehler et al (GCN 20299) at 01:42 UT, one hour after our reported mid-time. In fact, our data shows no indication of fading between 00:30 UT to 02:00 UT when our observations stopped, indicating an optical plateau. 

Magnitudes were calibrated using several nearby APASS stars. No correction for Galactic extinction in the direction of the GRB has been applied.