GCN Circular 22454

GRB 180224A: Swift/UVOT Detection

S. J. LaPorte (PSU) and A. Y. Lien (GSFC/UMBC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 180224A
85 s after the BAT trigger (Lien et al., GCN Circ. 22442
Not found
 
 
).
A fading source consistent with the XRT position
(Evans et al. GCN Circ. 22443
Not found
 
 
) also detected by (Lipunov et al. GCN Circ.
22444
Not found
 
 
; Watson et al. GCN Circ. 22446
Not found
 
 
; Pozanenko et al. GCN Circ. 22448
Not found
 
 
)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  13:30:44.10 = 202.68377 (deg.)
    Dec (J2000) = +38:04:44.5  =  38.07902 (deg.)
with an estimated uncertainty of 0.46 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               61          211          294         18.9 +/- 0.07
white              553         5337          287         20.7 +/- 0.33
v                  603         1397           97        >18.4
b                  552         1348           78        >19.5
u                  273         5063          500        >20.3
w1                 652         1446           97        >18.7
m2                 824          844           19        >18.2
w2                 751          771           19        >17.6

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.01 in the direction of the burst
(Schlegel et al. 1998).