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GCN Circular 20823

Subject
GRB 170306A: Swift/UVOT Upper Limits
Date
2017-03-06T18:52:02Z (7 years ago)
From
Sam Emery at MSSL-UCL <samuel.emery.15@ucl.ac.uk>
S.W.K. Emery (UCL-MSSL) and C. B. Markwardt (NASA/GSFC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 170306A
140 s after the BAT trigger (Markwardt et al., GCN Circ. 20819).
No optical afterglow consistent with the XRT position
(Markwardt et al., GCN Circ. 20819)
and the optical positions
(Guidorzi et al., GCN Circ. 20820; Schady et al., GCN Circ. 20822)
is detected in the initial UVOT exposures.
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           140          290          147         >20.0
u_FC               299          548          246         >18.9
white              140          771          186         >20.4
v                  629          821           39         >18.1
b                  554          747           39         >18.6
u                  299          722          265         >19.0
w1                 678          870           39         >18.1
m2                 653          846           39         >19.0
w2                 604          796           39         >18.1

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.41 in the direction of the burst
(Schlegel et al. 1998).
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