[vsnet-grb-info 13730] GRB 130725B: Swift/UVOT Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15045
SUBJECT: GRB 130725B: Swift/UVOT Observations
DATE:    13/07/26 17:50:43 GMT
FROM:    Frank Marshall at GSFC  <femarsha at khamseen.gsfc.nasa.gov>

S. R. Oates (UCL-MSSL) and C. A. Swenson (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 130725B
72 s after the BAT trigger (Swenson et al. GCN Circ. 15029;
Swenson GCN Circ. 15044).

A source consistent with the enhanced XRT position (Sbarufatti and Swenson GCN Circ. 15040)
is detected in the initial UVOT exposures in all filters except for uvm2 and uvw2.
The non-detection in these filters suggests a redshift ~<2.

The preliminary UVOT position is:
   RA  (J2000) =  14:16:57.76 = 214.24068 (deg.)
   Dec (J2000) = -11:07:41.8  = -11.12827 (deg.)
with an estimated uncertainty of 0.50 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               72          221          147         16.67 +/- 0.03
v                  614         6315          252         19.16 +/- 0.27
b                  540          559           19         18.20 +/- 0.28
u                  284          534          246         17.35 +/- 0.06
w1                 663         6725          236         20.01 +/- 0.36
m2                6320        16621         1003        >21.1
w2                4265         4465          197        >20.1

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.061 in the direction of the burst
(Schlegel et al. 1998).