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.