TITLE:   GCN CIRCULAR
NUMBER:  35633
SUBJECT: GRB240122A: PRIME near infrared detection
DATE:    24/01/25 20:05:40 GMT
FROM:    Joe Durbak at UMD <gcn.joedurbak@gmail.com>


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


Following the MAXI/GSC detection (Negoro et al. GCN 35593), GOTO optical candidate GOTO24eu/AT2024apy (Kumar et al. GCN 35596), and the Swift afterglow detection (Ambrosi et al. GCN 35600), we observed the transient field using J and H filters with PRIME ~1.5 days after MAXI/GSC detection.


At the position of the optical counterpart detected by GOTO, we detect an uncatalogued source in both J and H bands. Using nearby 2MASS stars for preliminary calibration we derive the following magnitudes, not corrected for Galactic extinction:  


Filter | Mag(AB)        | SNR | Seeing | Total exposure time (s) 

-------|----------------|-----|--------|-------------------------

J      | 21.02 +/- 0.20 | 6.3 | 1.373” | 1802

H      | 20.90 +/- 0.21 | 6.1 | 1.480” | 1544



PRIME is a 1.8m telescope with 1.56 square degree FOV (0.5 arcsec/pixel) located in Sutherland, South Africa.


Further observations are planned.


We thank the Osaka University observers at PRIME and the staff at SAAO for their support with these observations.