TITLE: GCN CIRCULAR NUMBER: 35439 SUBJECT: GRB 231230A: NOT optical upper limits DATE: 23/12/30 09:03:02 GMT FROM: Zipei Zhu at NAOC <zpzhu@nao.cas.cn> Z. Zhu, D. Xu (NAOC) report on behalf a larger collaboration: We observed the position of GRB 231230A (Moss et al., GCN 35436) using the Nordic Optical Telescope equipped with the ALFOSC images. Observations were carried out with the SDSS r and z filters, with an exposure time of 3x300 s and 5x200 s respectively. No new objects were dectected in our stacked image within or around the enhanced XRT position (Evans et al., GCN 35437), down to magnitudes r > 23.4 @ T-mid = 4.02 hr and z > 22.7 @ T-mid = 4.32 hr, calibrated with the nearby Pan-STARRS field. View this GCN Circular online at https://gcn.nasa.gov/circulars/35439. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...