[vsnet-grb-info 12657] GRB 121128A: Swift/UVOT Detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  14017
SUBJECT: GRB 121128A: Swift/UVOT Detection
DATE:    12/11/28 22:58:50 GMT
FROM:    Samantha Oates at MSSL  <sro at mssl.ucl.ac.uk>

S. R. Oates (MSSL-UCL) reports on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 121128A
85 s after the BAT trigger (Oates et al., GCN Circ. 14007). A source consistent 
with the XRT position (Osborne et al., GCN Circ. 14015) is detected in the initial 
white, v, b and u exposures only. The non-detection in the UV filters is consistent 
with the redshift of z=2.2 reported by Gemini North (Tanvir et al., GCN Circ. 14009)

The preliminary UVOT position is:
 RA  (J2000) =  20:02:24.00 = 300.60000 (deg.)
 Dec (J2000) = +54:17:59.1  =  54.29974 (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               85          235          147         16.19 +/- 0.03
v                  629          649           19         17.00 +/- 0.23
b                  554          573           20         17.51 +/- 0.17
u                  298          547          246         17.33 +/- 0.06
w1                 679         2173          175        >19.6
m2                 654         2496          214        >19.6
w2                 605         2447          214        >20.0

The magnitudes in the table are not corrected for the significant Galactic extinction
due to the reddening of E(B-V) = 0.31 in the direction of the burst
(Schlegel et al. 1998).