[vsnet-grb-info 28379] GRB 210722A: Swift/UVOT Detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30482
SUBJECT: GRB 210722A: Swift/UVOT Detection
DATE:    21/07/23 13:46:11 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18 at psu.edu>

M. H. Siegel (PSU) and P. D'Avanzo (INAF-OAB)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210722A
94 s after the BAT trigger (D'Avanzo et al., GCN Circ. 30475).
A source consistent with the XRT position is detected in the initial UVOT exposures.

The preliminary UVOT position is:
  RA  (J2000) =  01:48:07.28 =  27.03033 (deg.)
  Dec (J2000) = -06:20:49.7  =  -6.34713 (deg.)
with an estimated uncertainty of 0.42 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               94          244          147         14.31 +/- 0.02
v                  637          656           19         14.52 +/- 0.06
b                  563          583           20         14.65 +/- 0.04
u                  308          557          246         13.68 +/- 0.02
w1                 686          705           20         14.08 +/- 0.06
w2                4908         4971           62         17.08 +/- 0.14

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.027 in the direction of the burst
(Schlegel et al. 1998).