TITLE:   GCN CIRCULAR
NUMBER:  29955
SUBJECT: GRB 210506A: TNG NIR upper limits
DATE:    21/05/07 00:15:10 GMT
FROM:    Paolo D'Avanzo at INAF-OAB  <pda.davanzo@gmail.com>

P. D'Avanzo (INAF-OAB), V. D'Elia (ASI-SSDC), D. Malesani (DTU Space), E. Palazzi, A. Rossi (INAF-OAS), 
G. Andreuzzi, D. Carosati (INAF-TNG) on behalf of the CIBO collaboration report:

We observed the field of the short GRB 210506A (Tohuvavohu & DeLaunay, GCN Circ. 29947) with the Italian 3.6m TNG 
telescope equipped with NICS in imaging mode. A series of images were obtained with the J filter on 2021-05-06 from 
21:15:04 UT to 21:55:59 UT (i.e. at a mid time of about 20.9 hours after the burst). 

Our observations (with a field of view of 4.2' x 4.2') were centered at the position of the XRT source #3 
(see: https://www.swift.ac.uk/ToO_GRBs/00021430/ and Evans, GCN Circ. 29949). 

No obvious source is found within the position of source XRT #3 down to a 3-sigma limiting magnitude of J > 20.6 
(Vega, calibrated against the 2MASS catalogue). 
Unfortunately an image artefact, possibly due to bad sky subtraction, prevented us to visually investigate a portion 
(~ 5%) of the XRT error circle for source #3.