[vsnet-grb-info 28253] GRB 210702A: preliminary Swift/UVOT photometry

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30356
SUBJECT: GRB 210702A: preliminary Swift/UVOT photometry
DATE:    21/07/02 23:31:49 GMT
FROM:    Paul Kuin at MSSL  <npkuin at gmail.com>

N. P. M. Kuin (UCL-MSSL) 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 210702A
104 s after the BAT trigger (Lien et al., GCN Circ. 30351).
A source consistent with the XRT position
(Lien et al. GCN Circ. 30351)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  11:14:18.70 = 168.57793 (deg.)
    Dec (J2000) = -36:44:50.0  = -36.74723 (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              104          254          147         15.70 +/- 0.02
b                 3516         3716          197         15.46 +/- 0.03
u                  316          361           44         11.37 +/- 0.05

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.121 in the direction of the burst
(Schlegel et al. 1998).