D. A. Kann, L. Izzo (both HETH/IAA-CSIC), and A. Sota (IAA/CSIC) report
on behalf of HETH:
We observed the field of GRB 180705A (Stamatikos et al., GCN #22902)
with the 1.5-m OSN telescope in Granada, Spain.
We obtained 20 x 300 s images in the Ic band centered at 0.262416 days
(6.3 hrs) after the GRB.
At the XRT position of the GRB (Goad et al., GCN #22906), there is a
possible faint source, formally detected at Ic (Vega) = 23.6 +/- 0.2
mag. We note, however, that the background of the image is structured
because of the proximity of the bright star HD 123921 (V ~ 9 mag),
therefore the detection may be spurious. The formal 3 sigma upper limit
is Ic > 24 mag, also possibly overestimated.
Even if the source we detect is not real, any afterglow of this GRB is
clearly very faint, in agreement with other non-detection reports
(Lipunov et al., GCN #22904, Watson et al., GCN #22911, Breeveld et al.,
GCN #22912, Mazaeva et al., GCN #22913, Bikmaev et al., GCN #22929).
The field was calibrated against SDSS secondary standard stars using the
transformation of Lupton (2005).