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GCN Circular 18122

Subject
GRB 150811A: Swift/UVOT Detection
Date
2015-08-11T08:02:52Z (9 years ago)
From
Paul Kuin at MSSL <npkuin@gmail.com>
Paul Kuin (MSSL/UCL) and P. A. Evans (U Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150811A
147 s after the BAT trigger (Evans et al., GCN Circ. 18119). A source
consistent with the XRT position and the optical transient reported
by Butler et al.(GCN Circ. 18120) and Zheng et al. (GCN Circ. 18121)
is detected in the promptly available UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  19:25:21.4
    Dec (J2000) = -15:25:31.1
with an estimated uncertainty of 0.6 arc sec. (radius, 90% confidence).

The transient source is at a distance of 4.6 arcsec of a weak nearby
source.

Preliminary detections for the White and U finding charts 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           147          297          147         20.43 +/- 0.23
u_FC               306          549          241         18.24 +/- 0.11

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.17 in the direction of the burst
(Schlegel et al. 1998).
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