TITLE:   GCN CIRCULAR
NUMBER:  29207
SUBJECT: GRB 201227A: GRAWITA VST-ESO PARANAL observations
DATE:    20/12/30 18:38:24 GMT
FROM:    Paolo D'Avanzo at INAF-OAB  <pda.davanzo@gmail.com>

L. Izzo (DARK/NBI), P. D'Avanzo (INAF-OAB), E. Brocato (INAF-OAA/INAF-OAR) report on behalf of GRAWITA:

We observed the field of the short GRB 201227A (Fermi/GBM trigger 630774852; Ursi et al., GCN Circ. 29179; 
Svinkin et al., GCN Circ. 29182; Xiao et al., GCN Circ. 29187; Svinkin et al., GCN Circ. 29196; Lesage et al., 
GCN Circ. 29206) with the VLT Survey Telescope (VST) equipped with OmegaCAM (1 square degree FOV; 
Proposal ID ESO 0106.D-0343(A)). 
We obtained one epoch of observations with the r filter on 2020-12-28 between 07:10:07 UT and 07:32:12 UT 
(i.e. between 15.93 and 16.30 hours after the burst t0). 

The observations cover 2 square degrees enclosing ~ 100% of the IPN localization box (Svinkin et al., GCN Circ. 29182). 
Each one square degree pointing is the coaddition of five dithered exposures for a total exposure time of 300 seconds per 
pointing. 

From a preliminary analysis, we find no clear optical counterpart of GRB 201227A inside the IPN error box down to a 3sigma 
limiting magnitude of r ~ 22 (AB, calibrated against the SkyMapper survey). 

In particular, we do not find optical countepart candidates at the position of the four Swift/XRT sources reported by D'Elia et al. 
(GCN Circ. 29202) nor at the position of the only galaxy listed in the GLADE catalogue found inside the IPN error box (galaxy 
coordinates (J2000): RA, Dec = 168.85910, -73.94917, redshift z = 0.1379; Dalya et al., 2018, MNRAS, 479, 2347). 

Further analysis is in progress. 


We acknowledge excellent support from the ESO observing staff at Paranal, in particular Bin Yang.