TITLE:   GCN CIRCULAR
NUMBER:  29128
SUBJECT: GRB 201221D: Lowell Discovery Telescope afterglow observations
DATE:    20/12/22 12:59:55 GMT
FROM:    Simone Dichiara at UMCP/NASA/GSFC  <dichiara@umd.edu>

S.Dichiara (UMD, NASA-GSFC), E. Troja (UMD, NASA-GSFC), S.B. Cenko
(NASA-GSFC),  B. O'Connor (GWU, UMD), P. Gatkine (Caltech), J.M. Durbak
(UMD), A. Kutyrev (UMD, NASA-GSFC), S. Veilleux (UMD), report on behalf
of a larger
collaboration:

We observed the short GRB 201221D (Page et al., GCN 29112) using the
Large Monolithic Imager (LMI) on the 4.3m Lowell Discovery Telescope
(LDT) at Happy Jack, AZ. Observations started on December 22, at 09:13:28
UT (about 10.11 hours after the Swift trigger)
with SDSS r, i and z filters. Observations were taken at an airmass of
about 1.3 and seeing of about 0.8".

At the position of the optical candidate counterpart (Malesani et al.,
GCN 29117) we detect a source in all bands with r~23.9 AB mag and i~23.7
AB mag. This is fainter than the value reported by Malesani et al.
(r~23.1 at 1 hr) and may suggest that the source faded between the two
epochs. However, we note that at the same position a weak source is
visible in archival Pan-STARRS images, which we suggest as the putative
GRB host galaxy.
Our observations could be dominated by the galaxy's contribution, and
further observations to determine variability are planned.

We thank the staff of the Lowell Discovery Telescope for assistance with
these observations.