TITLE: GCN CIRCULAR NUMBER: 30221 SUBJECT: GRB210610B: SARA-KP 0.9m Optical Afterglow Detection DATE: 21/06/12 06:40:48 GMT FROM: Samalka Anandagoda at Clemson University S. Anandagoda, K. Pellegrin, and D. Hartmann report: We observed the field of GRB 210610B detected by Swift BAT (K. L. Page et al., GCN #30170), BALROG (B. Biltzinger et al., GCN #30171), GIT (H. Kumar et al., GCN #30174), V. Rumyantsev et al., V. Lipunov et al., Hu et al., Romanov, Fynbo et al.,Moskvitin et al. and Becerra et al. using the SARA 0.9m optical telescope located at Kitt Peak, AZ, USA, equipped with the Alta-E6-1105 camera. Observation started at 04:40:42 UTC on 2021-06-12 and ended at 05:43:44 UTC on 2021-06-12. We obtained a series of 150s exposure frames in the Bessell R filter. We detect the optical afterglow of GRB 210610B at the enhanced Swift-XRT position (Osborne et al. GCN 30189). The estimated magnitude of the GRB afterglow was 20.35 found by stacking 20 images of 150s each in the Bessell R band filter. T_start-T0 (hrs) T_end-T0 (hrs) Start Date (UTC) Filter Magnitude (mag) ---------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------- 32:34 33:37 2021-06-12T04:40:42 R 20.35 Photometry is done based on the PanSTARRS catalog. The Southeastern Association for Research in Astronomy (SARA) consortium operates three telescopes: the 0.9-m SARA-KP at Kitt Peak in Arizona, and the 0.6-m SARA-CT at Cerro Tololo in Chile, and the 1.0-m SARA-RM (formerly the JKT) telescope at Roque de los Muchachos Observatory in the Canary Islands. For more information see: Keel et al. (2016): https://iopscience.iop.org/article/10.1088/1538-3873/129/971/015002 ---------------------------------------------------------------------------------------