GRB 231111A: Leavitt Observatory optical observations

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