[vsnet-grb-info 6685] Swift trigger 325707: Swift/UVOT Upper Limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8287
SUBJECT: Swift trigger 325707: Swift/UVOT Upper Limits
DATE:    08/09/24 12:53:00 GMT
FROM:    Patricia Schady at MSSL/Swift  <ps at mssl.ucl.ac.uk>

P. Schady (MSSL-UCL) and S. Immler (CRESST/GSFC/UMD) report on behalf of 
the Swift/UVOT team:

The Swift/UVOT observed the field of the GRB candidate, BAT trigger number 
325707 (Immler et al., GCN Circ. 8285), with settled exposures starting 
78s after the trigger. We do not find any new source in the UVOT 
observations inside the BAT error circle (Immler et al., GCN Circ. 8285) 
or anywhere in the UVOT field of view. We note that the field is very 
crowded, and no observations were made in the white band filter due to the 
presence of a bright star in the field of view.

The 5-sigma upper limits in the UVOT photometric system (Poole et al. 
2008, MNRAS, 383, 627) for detecting a source in the first v finding chart 
exposure and subsequent co-added exposures from the first orbit of 
observations are:

Filter  T_start T_stop  Exp     Mag (5-sigma UL)
         (s)     (s)     (s)
================================================
v (fc)   78      478    393.4   > 18.4
v        599     759    40.1    > 18.4
b        558     848    28.8    > 17.6
u        533     833    58.5	> 17.9
uvw1     509     808    58.4	> 17.5
uvm2     484     783    58.4    > 17.3
uvw2     574     734    58.4	> 17.7

The values quoted above are not corrected for the expected Galactic 
extinction corresponding to a reddening of E(B-V) = 0.39 mag in the 
direction of the burst (Schlegel et al. 1998).