[vsnet-grb-info 20453] GRB 180325A: Swift/UVOT Detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22549
SUBJECT: GRB 180325A: Swift/UVOT Detection
DATE:    18/03/26 17:07:59 GMT
FROM:    Frank Marshall at Swift/UVOT  <marshall at milkyway.gsfc.nasa.gov>

F. E. Marshall (NASA/GSFC) and E. Troja (NASA/GSFC/UMCP)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 180325A
82 s after the BAT trigger (Troja et al., GCN Circ. 22532).
A fading source consistent with the enhanced XRT position
(Osborne et al. GCN Circ. 22539)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  10:29:42.59 = 157.42744 (deg.)
    Dec (J2000) = +24:27:48.6  =  24.46349 (deg.)
with an estimated uncertainty of 0.44 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

white               82          232          147         18.48 +/- 0.05
white             5039         5239          197         20.75 +/- 0.23
v                 5450         5650          197        >18.8
b                 4834         6385          309        >20.1
u                  295         6265          353        >20.0
w1                5860         6060          197        >20.1
m2                5654         5854          197        >19.4
w2                5245        12343          980        >20.9

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).