[vsnet-grb-info 16794] GRB 150724B: Swift/UVOT Detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18075
SUBJECT: GRB 150724B: Swift/UVOT Detection
DATE:    15/07/27 17:25:04 GMT
FROM:    Paul Kuin at MSSL  <npkuin at gmail.com>

N.P.M. Kuin(MSSL/UCL) reports on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150724B
88.6ks after the LAT trigger (Bissaldi et al., GCN Circ. 18065),
which was also observed at high energy by Fermi-GBM (Veres et al.,
GCN Circ 18066) and Konus-Wind (Golenetskii et al. GCN Circ. 18074).
Five UVOT exposures were obtained of which the first two show a
weak detection at the XRT position (Osborne et al., GCN Circ. 18069).

Preliminary magnitudes and 3-sigma upper limits using the UVOT
photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373)
are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white            88619      88799          178        19.64+-0.12
white            88802      90608         1765        20.99+-0.14
white            90614      90748           60        >19.53
white            94379      94558          176        >20.82
white            94562      96236         1648        >22.01

The brightness is consistent with the RATIR observation at 147ks
in r and i (Butler et al, GCN 18072).

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.06 in the direction of the burst
(Schlegel et al. 1998).