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GCN Circular 28177

GRB 200729A: Swift/UVOT Upper Limits
2020-07-30T12:41:58Z (4 years ago)
Samantha Oates at MSSL <>
S. R. Oates (U.Birmingham) and P. A. Evans (U. Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 200729A
145 s after the BAT trigger (Evans et al., GCN Circ. 28165).
No optical afterglow is detected above the flux of NGC 4242, consistent with the XRT position
(Osborne et al. GCN Circ. 28168), in the initial UVOT exposures. For all filters, we
have attempted to subtract off the light of NGC 4242 by measuring the flux
at a position offset from the XRT position, but of a similar brightness.

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

white_FC           145          295          147         >20.0
u_FC               303          553          246         >18.9
white              145          1874         431         >20.0
v                  633          1749         136         >17.6
b                  559          1849         136         >18.7
u                  303          1824         362         >18.9
w1                 682          1799          97         >18.2
m2                 658          1428          39         >17.8
w2                1359          1725          58         >17.8

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.01 in the direction of the burst
(Schlegel et al. 1998).
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