GCN Circular 22029
Subject
GRB 171020A: NOT optical afterglow detection
Date
2017-10-21T00:19:15Z (7 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@dark-cosmology.dk>
D. Malesani (DARK/NBI), M. Stone (Turku Univ.), K. Karhunen (Turku
Univ.), A. de Ugarte Postigo (IAA/CSIC and DARK/NBI), and D. Xu
(NAOC/CAS), report on behalf of a larger collaboration:
We observed the field of GRB 171020A (Page et al., GCN 22028) with the
Nordic Optical Telescope equipped with the AlFOSC imager and
spectrograph. Observations were carried out in the r and z filters,
starting on 2017 Oct 20.979 UT (22.9 min after the trigger).
Within the XRT error circle, we detect an uncatalogued source at
coordinates (J2000):
RA = 02:36:59.62
Dec = +15:12:16.0
By comparison with nearby stars from the Pan-STARRS catalog, we measure
r = 20.98 +- 0.03 AB. As this object is not visible in the deeper,
archival Pan-STARRS images, and given the coincidence with the X-ray
counterpart, we suggest this object to be the optical afterglow of GRB
171020A.