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GCN Circular 17531

Subject
GRB 150301B: Swift/UVOT Observations
Date
2015-03-02T14:28:45Z (9 years ago)
From
Margaret Chester at PSU <chester@swift.psu.edu>
M. M. Chester (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 150301B
86 s after the BAT trigger (Lien et al., GCN Circ. 17515).  A fading 
source consistent with the XRT position (Evans et al. GCN Circ. 17520) 
and the optical transient reported by Buckley et al. (GCN Circ. 17518)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
   RA  (J2000) =  05:56:39.89 =  89.16622 (deg.)
   Dec (J2000) = -57:58:10.4  = -57.96955 (deg.)
with an estimated uncertainty of 0.42 arc sec. (radius, 90% confidence).

Preliminary detections and 3-sigma upper limits for the White finding 
chart and subsequent exposures 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_FC            86          236          147         16.2 +/- 0.1
white             3986         4121          133        >20.2
v                 5833         6033          197        >19.7
b                 3782         3982          197        >19.6
u                  298          543          241         17.1 +/- 0.1
w1                6243        10068          579        >19.9
m2                6038         6237          197        >19.8
w2                5628        16054          963        >21.6

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.08 in the direction of the burst
(Schlegel et al. 1998).
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