TITLE:   GCN CIRCULAR
NUMBER:  21123
SUBJECT: GRB 170519A: Watcher optical observations
DATE:    17/05/20 18:31:58 GMT
FROM:    Antonio Martin-Carrillo at UCD,Space Science Group  <antonio.martin-carrillo@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 170519A (Ukwatta, et al., GCN 21106 using the 40cm UCD Watcher telescope at Boyden Observatory in South Africa.

Observations started on May 19th at 16:30 UT (T0+11.5h) and consisted of a series of 20s exposures in SDSS r’ filter for a total monitoring time of 3 hours. Based on combined images with mid-time at 17:00 UT, we derive a preliminary magnitude of r’=19.3 +/- 0.3 (AB system).

Magnitudes were calibrated using 2 nearby APASS stars. No correction for Galactic extinction in the direction of the GRB has been applied.