GCN Circular 40251

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

Following the Swift BAT detection (GCN 40224

), we observed the transient field in J and H filters with PRIME ~12 hours after the initial Swift detection.

At the position of the optical counterpart reported by Swift UVOT (GCN 40244

), we detect an uncatalogued source in both J and H band. Using nearby VISTA Hemispherical Survey (VHS) for preliminary calibration we derive the following magnitudes and limits, not corrected for Galactic extinction:

Filter	Mag(AB)
J	18.8 +/- 0.06
H	19.2 +/- 0.05

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.