TITLE:   GCN CIRCULAR
NUMBER:  35124
SUBJECT: GRB 231117A: OHP/T120 optical observations
DATE:    23/11/19 14:45:16 GMT
FROM:    Benjamin Schneider at MIT <bschn@mit.edu>

B. Schneider (MIT), C. Adami (LAM/Pytheas/AMU), D. Turpin (CEA Paris-Saclay), S. Basa (Pytheas/OHP/LAM), Jean Balcaen (Pytheas/OHP), E. Le Floc'h, F. Schüssler (CEA Paris-Saclay), report on behalf of a larger collaboration:

We observed the field of the short GRB 231117A (Laha et al., GCN 35071; Navaneeth et al. GCN 35072; Cattaneo et al., GCN 35075; Svinkin et al., GCN 35079; Cheung et al., GCN 35081) and its afterglow candidate (Yang et al. GCN 35083; Rastinejad et al., GCN 35087; Gompertz et al., GCN 35088; Kumar et al., GCN 35089; Ahumada et al., GCN 35093; ​​Rhodes et al., GCN 35097; Andreoni et al., GCN 35099; Kilpatrick et al., GCN 35102) using the T120cm telescope at Observatoire de Haute-Provence (France). A total of 11 exposures of 900 seconds were obtained in the r band at 19:52:31.680 UT on 2023-11-17, ~16.82h after the trigger.

In the combined frame, we measured a flux excess at the position of SDSS J220933.34+133119.5 compared to archive values. After subtracting the SDSS J220933.34+133119.5 galaxy using the Legacy Survey image, we clearly detect a source consistent with the afterglow candidate reported by Yang et al., GCN 35083.

The preliminary magnitude derived for that source is

r = 21.0 ± 0.1 mag (AB)

The photometric calibration was performed using nearby stars from the PanSTARRS catalog and magnitudes are not corrected for Galactic extinction.

We acknowledge the Observatoire de Haute Provence staff for their excellent support.