TITLE:   GCN CIRCULAR
NUMBER:  23747
SUBJECT: GRB 190114C: Continued UKIRT JHK observation
DATE:    19/01/17 14:35:59 GMT
FROM:    Myungshin Im at Seoul Nat U  <mim@astro.snu.ac.kr>

Myungshin Im, Gregory S. H. Paek, Changsu Choi (CEOU/SNU), on behalf of a
larger collaboration

We observed again the afterglow of GRB 190114C (Gropp et al., GCN 23688;
Tyurina et al., GCN 23690, de Ugarte Postigo et al., GCN 23692, Lipunov et
al. GCN 23693, Selsing et al. GCN 23695, Izzo et al. GCN 23699, Bolmer et
al. GCN 23702, Castro-Tirado et al. GCN 23708, Kann et al. GCN 23710, Im et
al. GCN 23717, 23741; Siegel et al. GCN 23725, Mazaeva et al. GCN 23727,
D'Avanzo et al. GCN 23729, Peak et al. GCN 23731, Kim et al. GCN 23732,
Kumar et al. GCN 23733, Mazaeva et al. GCN 23741, 23746, Kumar et al. GCN
23742) with the United Kingdom Infrared Telescope (UKIRT). The observation
started at 2019-01-17 05:06 UT or about 2.33 days after the initial alert.

Preliminary magnitudes are derived from quick-look data, using nearby 2MASS
stars as photometry references. The afterglow faded by about 0.5 magnitude
in all of the JHK bands with the J-band magnitude given below.

Filter Date UT-start Vega_Mag (AB mag)
J    2019-01-16 05:47:58.042    18.0 +/- 0.1   (19.2 AB)

The result implies that the current fading of NIR afterglow (0.5 mag/day)
is slower  than what we reported in a previous circular (1.2 mag/day) based
on earlier data (Im et al. GCN 23740).

Further observations are planned.
We thank the staffs at UKIRT for carrying out the observation.