[vsnet-grb-info 28515] GRB 210807A: Swift/UVOT Detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30618
SUBJECT: GRB 210807A: Swift/UVOT Detection
DATE:    21/08/08 21:07:25 GMT
FROM:    Sam LaPorte at PSU  <sjl5346 at psu.edu>

 GRB 210807A: Swift/UVOT Detection

S. J. LaPorte (PSU) and A. Y. Lien (GSFC/UMBC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210807A
210 s after the BAT trigger (Lien et al., GCN Circ. 30600).
A source consistent with the XRT position
(Lien et al. GCN Circ. 30600)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  05:06:43.89 =  76.68289 (deg.)
    Dec (J2000) = +58:14:59.2  =  58.24979 (deg.)
with an estimated uncertainty of 0.43 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

b                        489            683            38        >17.84
u                        639            659            19        >17.04
v                        390            583            39
16.58+-0.25
uvw1                 440            633             38        >17.12
uvw2                 539            721             26        >17.08
white                 234            383           147
16.93+-0.04
white                 234            708           184          17.19+-0.05

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.409 in the direction of the burst
(Schlegel et al. 1998).