TITLE:   GCN CIRCULAR
NUMBER:  41015
SUBJECT: GRB 250706B: Swift/UVOT Detection
DATE:    25/07/07 18:35:19 GMT
FROM:    Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>

M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 250706B 12.5 ks after the SVOM/ECLAIRs trigger (Palmerio et al., GCN Circ. 40989). A source consistent with the XRT position (Ferro et al., GCN Circ. 40996) and the optical transient (Zhu et al., GCN Circ. 40991; Palmerio et al., GCN Circ. 40992; Romanov, GCN Circ. 40995) is detected in the UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  02:44:53.43 =  41.23097 (deg.)
    Dec (J2000) = -50:03:40.2  = -50.06116 (deg.)
with an estimated uncertainty of 0.42 arc sec. (radius, 90% confidence).

Preliminary detections and 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: 

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

u                12471        18805         2023      16.49+/-0.03

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.026 in the direction of the burst
(Schlegel et al. 1998).