GCN Circular 30425
Subject
GRB 210708A: Swift/UVOT Upper Limits
Event
Date
2021-07-08T20:24:24Z (4 years ago)
From
Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>
M. H. Siegel (PSU) and B. Sbarufatti (PSU)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 210708A
121 s after the BAT trigger (Sbarufatti et al., GCN Circ. 30413).
No optical afterglow consistent with the XRT position
(Sbarufatti et al. GCN Circ. 30413) is detected in the initial UVOT exposures.
We note that the XRT position is close to the bright star HD 100708,
the brightness of which may obscure a faint afterglow.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
u_FC 121 370 246 >19.4
v 427 4406 236 >19.6
b 377 5077 108 >19.3
u 121 5021 481 >19.4
w1 476 4816 236 >18.9
m2 452 4611 236 >19.4
w2 403 4201 236 >19.5
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.160 in the direction of the burst
(Schlegel et al. 1998).