TITLE:   GCN CIRCULAR
NUMBER:  35611
SUBJECT: GRB 240122A: BOOTES-2/TELMA optical upper limit and 1.5m OSN detection
DATE:    24/01/23 19:50:44 GMT
FROM:    Youdong HU at IAA-CSIC <huyoudong072@hotmail.com>

Y.-D. Hu, F. Aceituno, E. Fernandez-Garcia, A. J. Castro-Tirado, M.D. Caballero-Garcia, R. Sanchez-Ramirez, I. Perez-Garcia, S.-Y. Wu, S. Guziy  (IAA-CSIC), C. Perez del Pulgar, A. Castellon, I. Carrasco, A. Reina (Univ. de Malaga), R. Fernandez-Munoz (IHSM/UMA-CSIC) and M. Jelinek (ASU-CAS), on behalf of a larger collaboration, report:

Following the detection of GRB 240122A by MAXI/GSC (Negoro et al., GCNC 35593), we triggered the 0.6m BOOTES-2/TELMA robotic telescope at IHSM La Mayora (UMA-CSIC) in Algarrobo Costa (Malaga, Spain), and pointing to the burst position on Jan. 22 at 19:45 UT (i.e. ~9.3 hrs after trigger). In the co-added image (14 x 60 s, clear filter, affected by the bright moonlight), the optical afterglow reported by GOTO (Kumar et al. GCNC 35596), GTC (Thoene et al. GCNC 35598) and VLT (Saccardi et al. GCNC 35599) is not detected down to 17.6 mag, which is consistent with the limit reported by LT (GCNC 35597).

Later on, we triggered the 1.5m telescope at Observatorio de Sierra Nevada (OSN) near Granada, Spain, starting on Jan. 22 at 23:46 UT (i.e. 13.3 hrs after trigger) in BVRI bands. The afterglow is clearly detected with I~20.1+-0.1 mag in the co-added image (7 x 90 s), and consistent with the enhanced XRT/Swift position (Ambrosi et al. GCNC 35600). Further imaging is ongoing.

We thank the staff at both IHSM/UMA-CSIC La Mayora and OSN for their excellent support.