TITLE:   GCN CIRCULAR
NUMBER:  23695
SUBJECT: GRB 190114C: NOT optical counterpart and redshift
DATE:    19/01/14 22:45:48 GMT
FROM:    Jonatan Selsing at DARK/NBI  <jselsing@dark-cosmology.dk>

J. Selsing (DAWN/NBI and DAWN/DTU), J.P.U. Fynbo (DAWN/NBI and
DAWN/DTU), K.E. Heintz (Univ. of Iceland), D. Watson (DAWN/NBI and
DAWN/DTU), and S. Dyrbye (NOT), report on behalf of a larger
collaboration:

We observed the optical 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) with the 2.5-m Nordic Optical Telescope (NOT)
equipped with the Alfosc instument. We have carried out a series of 300s
griz observations, starting at 21:26:28 UT, January 14th - 29 minutes
after the BAT trigger. The optical counterpart is very clearly detected.

We have calibrated the photometric zeropoint against the Pan-STARRS
catalog and derive the following magnitudes for the afterglow:

g = 17.72 +- 0.11 AB mag 
r = 16.90 +- 0.04 AB mag 
i = 16.40 +- 0.02 AB mag 
z = 16.25 +- 0.12 AB mag

We immediately followed up with spectroscopic observations using the
Alfosc instrument, in which the afterglow is very clearly detected. From
the detection of strong absorption lines from Ca H & K along with Na ID
in the afterglow spectrum, we derive a redshift of z = 0.42, which we
suggest is the redshift of the GRB.

[GCN OPS NOTE(15jan19): Per author's request, Dyrbye was moved from the
last paragraph to the author list.]