TITLE:   GCN CIRCULAR
NUMBER:  16157
SUBJECT: GRB 140423A: Further Observations with Swift/UVOT
DATE:    14/04/23 21:12:24 GMT
FROM:    Margaret Chester at PSU  <chester@swift.psu.edu>

M. M. Chester (PSU), E. Sonbas (NASA/GSFC/Adiyaman Univ.), and 
F. E. Marshall (NASA/GSFC) report on behalf of the Swift/UVOT team:

Further analysis confirms UVOT's detection of the afterglow of GRB 140423A
(Sonbas et al., GCN Circ. 16142) reported by Elenin et al. (GCN Circ. 16143).

The UVOT position based on the initial exposure is:
   RA  (J2000) =  13:09:08.54 = 197.28558 (deg.)
   Dec (J2000) = +49:50:29.4  =  49.84150 (deg.)
with an estimated uncertainty of 0.48 arc sec. (radius, 90% confidence).
This position is consistent with the enhanced XRT position reported by 
Beardmore et al. (GCN Circ. 16155).

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             2947         3097          147         19.80 +/- 0.09
v                 3104         3303          197         19.33 +/- 0.19
b                 3924         4123          197         19.96 +/- 0.16
u                 3719         5353          393        >21.3
w1                3513         5148          393        >21.7
m2                4743         4943          197        >20.7
w2                4334        11161          808        >22.1

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.01 in the direction of the burst
(Schlegel et al. 1998).