TITLE:   GCN CIRCULAR
NUMBER:  23911
SUBJECT: GRB 190219A: NOT optical afterglow candidate
DATE:    19/02/20 11:16:15 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

D. Xu (NAOC), K.E. Heintz (Univ. of Iceland), D.B. Malesani 
(DAWN/NBI/DTU and DARK/NBI), Z.P. Zhu (NAOC), P. Galindo (NOT), J. Viuho 
(NOT), report on behalf of a larger collaboration:

We observed the field of GRB 190219A (Beardmore et al., GCN 23902) using 
the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC 
camera. Observations started at 01:13:50 UT on 2019-02-20, i.e., 5.58 hr 
after the burst, and we obtained 6x300 s Sloan r-band and 10x200 s 
z-band frames. The weather conditions of the night were bad, with thick 
clouds (which accounts for the large delay of our observations).

Among our data, the z-band images are deeper, and a source is detected 
in the stacked observations, at coordinates (J2000):

R.A. (J2000) = 12:38:30.32
Dec. (J2000) = +76:36:46.62

with a radius uncertainty of ~ 0.2 arcsec, within the enhanced Swift-XRT 
error circle (Beardmore et al., GCN 23907). We measure m(z) = 22.8 ¡À 0.4 
AB at 6.32 hr post-burst, calibrated against nearby Pan-STARRS stars. 
The source is not detected in the stacked r-band image, down to a 
limiting magnitude of m(r) > 22.5 AB. We note that the detected 
magnitude is fainter than the Pan-STARRS survey limit, and as we lack 
temporal information we cannot comment on variability. We propose this 
object as a candidate counterpart for GRB 191202A, but further 
observations are required to establish variability.