TITLE:   GCN CIRCULAR
NUMBER:  15780
SUBJECT: GRB 140129B: Swift/UVOT Detection
DATE:    14/01/30 19:11:46 GMT
FROM:    Craig Swenson at PSU/Swift  <cswenson@astro.psu.edu>

C. A. Swenson (PSU) and M. G. Bernardini (INAF-OAB) report on behalf
of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 140129B
356 s after the BAT trigger (Bernardini et al., GCN Circ. 15765).
A source consistent with the XRT position (Goad et al. GCN Circ. 15770)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
     RA  (J2000) =  21:47:01.66 = 326.75691 (deg.)
     Dec (J2000) = +26:12:23.0  =  26.20638 (deg.)
with an estimated uncertainty of 0.50 arc sec. (radius, 90% confidence).

Preliminary detections 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              356          506          147         17.05 ± 0.03
v                  663         5031           72         18.04 ± 0.20
b                  588          608           20         17.90 ± 0.20
u                  562          582           20         17.24 ± 0.17
w1                 538          732           39         17.27 ± 0.16
m2                 513         1089           58         17.57 ± 0.19
w2                 638         1039           58         17.99 ± 0.19

The clear detection in all UVOT filters indicate this burst is at a redshift
of z < ~1.5.

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.09 in the direction of the burst
(Schlegel et al. 1998).