[vsnet-grb-info 20469] GRB 180329B: Swift/UVOT Detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22565
SUBJECT: GRB 180329B: Swift/UVOT Detection
DATE:    18/03/30 11:38:14 GMT
FROM:    Sam Emery at MSSL-UCL  <samuel.emery.15 at ucl.ac.uk>

S.W.K. Emery (UCL-MSSL) and J. L. Racusin (NASA/GSFC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 180329B
113 s after the BAT trigger (Racusin et al., GCN Circ. 22558).
A fading source consistent with the XRT position
(Beardmore et al. GCN Circ. 22559) also detected by the
NOT (Perley et al. GCN Circ. 22562) and RATIR (Watson et al. GCN Circ. 22564)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  05:31:36.91 =  82.90381 (deg.)
    Dec (J2000) = -23:41:25.8  = -23.69051 (deg.)
with an estimated uncertainty of 0.43 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              113          263          147         17.69 +/- 0.04
white              550         6892          599         17.64 +/- 0.03
v                  601         5867          274         17.25 +/- 0.07
b                  526         6687          452         17.94 +/- 0.05
u                  271         6482          697         17.00 +/- 0.04
u                16039        39219         1961         18.74 +/- 0.07
w1                 650         6277          452         18.72 +/- 0.14
m2                 626         6073          274        >19.8
w2                 577         7017          390        >20.2

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.04 in the direction of the burst
(Schlegel et al. 1998).