TITLE:   GCN CIRCULAR
NUMBER:  39705
SUBJECT: GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
DATE:    25/03/13 18:41:30 GMT
FROM:    O. Guiffreda at UMD <oriogui@umd.edu>

O. Guiffreda (UMD), J. Durbak (UMD), E. Troja (U Rome), A. S. Kutyrev (NASA/GSFC), S. B. Cenko (NASA/GSFC)

Following up the initial PRIME detection (GCN 39670), the transient field was observed a second time ~3.5 days after the initial Fermi GBM trigger (GCN 39635).

At the position of the optical counterpart AT2025dws (Stein et al., GCN 39639), we no longer detect any uncatalogued sources in either J-band or H-band. Using nearby VISTA Hemispherical Survey (VHS) stars for preliminary calibration we derive limiting magnitudes of J <21.0 AB mag and H <20.9 AB mag, not corrected for galactic extinction. 

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.