GCN Circular 20988
Subject
GRB 170405A: NOT optical observations
Date
2017-04-06T01:22:36Z (7 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@dark-cosmology.dk>
Daniele Malesani (DARK/NBI), K. E. Heintz (DARK/NBI and Univ. Iceland),
and Tapio Pursimo (NOT) report on behalf of a larger collaboration:
We observed the optical afterglow of GRB 170405A (Troja et al., GCN
20984; Hui & Meegan, GCN 20986; Vianello & Kocevski, GCN 20987) with the
Nordic Optical Telescope (NOT) equipped with the ALFOSC imager.
Observations were carried out in the SDSS griz filters, with a
sub-optimal PSF (1.6-2.0").
Inspection of the r-band image (with mean time Apr 6.01 UT, that is 5.47
hr after the trigger) clearly shows the optical afterglow first
localized by UVOT (Troja et al., GCN 20984), which has now faded to r =
21.05 +- 0.08 AB, calibrated against nearby stars from the Pan-STARRS
catalog. In our images, the afterglow coordinates are perfectly
consistent with the UVOT values:
RA(J2000) = 14:39:18.72
Dec(J2000) = -25:14:35.3
We also note the presence of a nearby object approximately 2.3" W of the
afterglow, also visible in the Pan-STARRS archival images (with a
Pan-STARRS magnitude r = 21.82 +- 0.19 AB). Its relation to the GRB is
not clear, but its proximity may affect the afterglow photometry.