TITLE: GCN CIRCULAR NUMBER: 40624 SUBJECT: GRB 250601A: PRIME J band upper limit. DATE: 25/06/03 22:03:13 GMT FROM: N. Passaleva at Sapienza University of Rome <niccolo.passaleva@uniroma1.it> N. Passaleva (U Rome), O. Guiffreda (UMD), J. Durbak (UMD), M. Elkabir (U Rome), E. Troja (U Rome), A. S. Kutyrev (NASA/GSFC), S. B. Cenko (NASA/GSFC) Following the Fermi Gamma-ray Burst Monitor (GBM) detection (GCN 40596), and the Swift/BAT-GUANO arcminute localization of same event, we observed the transient field in J filter with PRIME ~23.5 hours after the initial Fermi detection. Using nearby VISTA Hemispherical Survey (VHS) we do not detect any uncatalogued source down to J>20.3 AB (3-sigma) at the position of the candidates reported by Swift/XRT (Page et al. GCN 40604, Salvaggio et al., GCN 40606) and EP/FXT (Liu et al., GCN 40607). PRIME is a 1.8m telescope with 1.56 square degree FOV (0.5 arcsec/pixel) located in Sutherland, South Africa at the South African Astronomical Observatory (SAAO) (Kutyrev et al. 2023, Yama et al. 2023, Durbak et al. 2024). We thank the Osaka University observers at PRIME and the staff at SAAO for their support with these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/40624. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...