TITLE:   GCN CIRCULAR
NUMBER:  35003
SUBJECT: GRB 231111A: Leavitt Observatory optical observations
DATE:    23/11/12 17:16:00 GMT
FROM:    leavittob@gmail.com

L. Moretti  and E. Pavoni (Leavitt Observatory), 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 imaged the field of GRB 231111A (Lipunov et al., GCN 34980; Melandri  et al., GCN 34981; Jiang et al., GCN 34982; Lipunov et al., GCN 34983; Kumar et al., GCN 34984; Osborne et al., GCN 34991; Wen-Long Zhang et al., GCN 34993; Pankov et al., GCN 34994; Osborne et al., GCN 34995; Ruocco, GCN 34997; Li et al., GCN 35001) with the telescope of Leavitt Observatory, Italy. Member of: 

UAI/SSV - Unione Astrofili Italiani/sezione stelle variabili, GRB section.
ATA - Associazione Tuscolana di Astronomia.

The observations started 189 minutes after the BAT trigger, at 17:26:49 UT on 2023/11/11, with our RC telescope D=250 mm F/D=8.

Weather conditions were medium, with light and variable cloud cover. 

We co-added 15 images of 120 sec each, acquired from 17:26:49 to 18:20:58 UT. All images are R (Cousins) filtered, calibrated with master dark and master flat.

We confirm a fading afterglow in the error box of the astrometrically corrected position measured by Swift-XRT (GCN 34991), at the following coordinates +/- 2 arcsec:

RA(J2000.0)  =  19h 20m 45.25s
DEC(J2000.0) = +52d 26' 09.9''

The result of our photometry is:

-------------------------------------------------------------------------
JD_UTC at mid-exposure       mag            Err              Flt   
-------------------------------------------------------------------------
2460260.2464583                      20.1            +/- 0.2            R    
    

Magnitudes were estimated with the Gaia DR3 catalogue (*) and are not corrected for galactic dust extinction.

The message may be cited.

(*) https://gea.esac.esa.int/archive/documentation/GEDR3/Data_processing/chap_cu5pho/cu5pho_sec_photSystem/cu5pho_ssec_photRelations.html