GCN Circular 42191
Subject
GRB251007A: Swift/UVOT Detection
Event
Date
2025-10-10T17:40:49Z (25 days ago)
From
Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>
Via
Web form
M. H. Siegel (PSU) and E/ Ambrosi (INAF-IASFPA) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 251007A 79 s after the BAT trigger (Ambrosi et al., GCN Circ. 42146). A fading source consistent with the XRT position (Beardmore et al., GCN Circ. 42161) and the previously reported optical source (Wu et al., GCN Circ. 42154; Malesani et al., GCN Circ. 42158, Hu et al. GCN Circ 42174) is detected in the initial UVOT exposures.
The preliminary UVOT position is:
RA (J2000) = 08:32:42.39 = 128.17664 (deg.)
Dec (J2000) = +21:48:46.3 = 21.81285 (deg.)
with an estimated uncertainty of 0.45 arc sec. (radius, 90% confidence).
Preliminary detections 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
white 80 229 146 18.42+/-0.08
white 17739 18156 406 >20.41
v 11939 39105 2335 >20.09
b 16827 17734 885 >20.39
u 291 418 124 19.11+/-0.36
uvm2 27913 39155 906 >20.29
uvw2 23059 34819 1506 >20.58
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.039 in the direction of the burst
(Schlegel et al. 1998).