TITLE:   GCN CIRCULAR
NUMBER:  35394
SUBJECT: GRB 231216A: Osservatorio Astronomico Nastro Verde upper limit
DATE:    23/12/17 20:06:20 GMT
FROM:    Nello Ruocco at Osservatorio Nastro Verde - Sorrento (Naples) - Italy - MPC Code C82 <osservatorionastroverde@gmail.com>

Nello Ruocco at Osservatorio Nastro Verde - Sorrento (Naples) - Italy
in a large collaboration with:
M.G. Dainotti (National Astronomical Observatory of Japan), 
Y. Niino (Tokyo University, Institute of Astronomy), 
K. Kalinowski (Aarhus University, Department of Physics and Astronomy),
B. De Simone (Universita' degli Studi Di Salerno)
report: 

We image the field of GRB 231216A detected by Swift Burst Alert Telescope (BAT)(trigger 1202749)
with telescope of Nastro Verde Observatory - Sorrento (Naples), Italy. Member of: 
AAVSO - American Association of Variable Star Observers.
UAI/SSV - Unione Astrofili Italiani/sezione stelle variabili.
AstroCampania Associazione

The observations started at 20:15 UT of  2023/12/16, after 1,40 hours after the GRB trigger, with principal telescope  SC 0.35 f/10 with focal reduced + CCD Sbig ST10 XME
I took 20 image of 60 sec each. All images are unfiltered, calibrated with masterdark and masterflat,stacked with Tycho Tracker software
We have not detected any clearly visible sources, up to 19.5th magnitude  in a sky with light clouds and gusts of wind.
Start T0+                End T0+        Rlim
20:15:25 UT            20:36:38 UT      19.5

We did not found any optical counterpart in the error box of the XRTcandidate.
T. Sbarrato et al. GCN 35378



Magnitudes were estimated with the Gaia DR2 cat. and 
are not corrected for galactic dust extinction.



The message may be cited.