TITLE:   GCN CIRCULAR
NUMBER:  35613
SUBJECT: GRB 240122A: Swift/UVOT Upper Limits
DATE:    24/01/23 22:57:57 GMT
FROM:    Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>

M. H. Siegel (PSU) and and V. D’Elia (SSDC & INAF-OAR) report on behalf of the
Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 240122A
from 29.5 ks to 35.6 ks after the MAXI trigger (Negoro et al., GCN Circ. 35593).
No optical afterglow consistent with either the optical (Kumar et al., GCN
Circ. 35596) or X-ray (Ambrosi et al., GCN Circ. 3600) position is detected in the initial
UVOT exposures. The lack of detection in the u-band would be consistent with the
redshift of 3.162 given by Saccardi et al. (GCN Circ. 35599).

Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial exposures of
the candidate afterglow field are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

u                35166       35655          481         >20.4

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.064 in the direction of the burst
(Schlegel et al. 1998).