GCN Circular 39199
Subject
GRB 250207A: Swift/UVOT Detection
Date
2025-02-07T10:42:24Z (3 days ago)
From
Paul Kuin at MSSL <npkuin@gmail.com>
Via
email
Paul Kuin (MSSL/UCL) and M. Ferro (INAF-OAB) report on behalf of
the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 250207A
113 s after the BAT trigger (Ferro et al., GCN Circ. 39182). The source
was
also reported by Angulo et al. GCN Circ. 39186.
The preliminary UVOT position is:
RA (J2000) = 01:04:21.39 = 16.08912 (deg.)
Dec (J2000) = -12:09:52.5 = -12.16459 (deg.)
with an estimated uncertainty of 0.42 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 113 263 147 15.00 +/- 0.02
v 655 674 19 16.89 +/- 0.20
b 581 600 19 16.56 +/- 0.09
u 326 575 246 15.65 +/- 0.03
uvm2 679 699 19 > 17.3 (3 sigma UL)
uvw2 630 650 19 > 17.6 (3 sigma UL)
The lack of detection in the UVM2 band may indicate a redshift greater
than 1.3.
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.027 in the direction of the burst
(Schlegel et al. 1998).