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 �� 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.