TITLE:   GCN CIRCULAR
NUMBER:  21217
SUBJECT: GRB 170607A: NOT optical afterglow detection
DATE:    17/06/08 08:39:04 GMT
FROM:    Kasper Elm Heintz at Univ. of Iceland and DARK/NBI  <heintz@dark-cosmology.dk>

K.E. Heintz (Univ. of Iceland and DARK/NBI), A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), and J. Claesen (NOT) report on behalf of a larger collaboration, 

We have observed the field of GRB 170607A (D���Ai et al., GCN 21214) with the 2.5m Nordic Optical Telescope at La Palma, Spain. The observations consisted of 3x180s in the Sloan g-, r- and i-bands and were carried out at a mid-time of 04:23:59 UT (i.e. 5.03 hr after the burst). The bright afterglow is well detected in all the individual frames. From the reduced and combined images we measure magnitudes of:

g(AB) = 18.57 +/- 0.08 mag
r(AB) = 18.36 +/- 0.06 mag
i(AB) = 18.22 +/- 0.05 mag

calibrated against nearby SDSS field stars.

We also note the presence of a galaxy at a photometric redshift of 0.632 in the SDSS images, close to the location of the burst, which we identify as a host galaxy candidate.