TITLE:   GCN CIRCULAR
NUMBER:  42501
SUBJECT: GRB251026B: PRIME H-band upper limit
DATE:    25/10/28 10:04:28 GMT
FROM:    Massine El Kabir <m.elkabir@campus.unimib.it>

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

Following the detection of a candidate optical counterpart (Belkin et al., GCN 42470), we observed the field of GOTO GOTO25jgl/AT2025absf in the H filter with PRIME.  Observations started ~ 2 d after the initial Fermi trigger (Dafčíková et al., GCN 42455). 

At the GOTO position (Belkin et al., GCN 42470), no obvious counterpart is detected on the top of the bright nearby galaxy. Due to the bright galaxy background, it is hard to assess the presence of a faint transient source without a template. Using GALFIT, we modelled the galaxy with a single Sersic profile and, after subtraction, derive a 3-sigma upper limit of H > 19 AB mag

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.