[vsnet-grb-info 23879] GRB 191004B: Swift/UVOT Detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25978
SUBJECT: GRB 191004B: Swift/UVOT Detection
DATE:    19/10/07 20:45:09 GMT
FROM:    Sam LaPorte at PSU  <sjl5346 at psu.edu>

GRB 191004B: Swift/UVOT Detection

S. J. LaPorte (PSU) and S. B. Cenko (GSFC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 191004B
69 s after the BAT trigger (Cenko et al., GCN Circ. 25947).
A fading source consistent with the XRT position
(Beardmore et al. GCN Circ. 25951)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  03:16:49.10 =  49.20459 (deg.)
    Dec (J2000) = -39:38:03.9  = -39.63441 (deg.)
with an estimated uncertainty of 0.43 arc sec. (radius, 90% confidence),
consistent with the positions reported by LCO (Strausbaugh et al. GCN Circ.
25949),
NOT (Heintz et al. GCN Circ. 25954), VLT/X-Shooter (D'Elia et al. GCN Circ.
25956),
COATLI (Watson et al. GCN Circ. 25958), and GROND (Schady et al. GCN Circ.
25960).

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

b                    38697         38997          295           >20.42
uvm2             44827         45727          885           >20.25
u                       294              387            91           >19.04

v                    43916         44822          885           >20.07
uvw1             45734         46281          538            >19.96
uvw2             39915         40544          618            >20.09
white                   82             232          147
18.01+-0.05
white             39003         39909          885              20.51+-0.13



The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).