[vsnet-grb-info 19777] GRB 170903A: Swift/UVOT Upper Limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  21806
SUBJECT: GRB 170903A: Swift/UVOT Upper Limits
DATE:    17/09/04 11:02:08 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld at ucl.ac.uk>

A. A. Breeveld (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 170903A 
3484 s after the BAT trigger (Markwardt et al., GCN Circ. 21793).
No optical afterglow consistent with the XRT position (Goad et al. GCN 
Circ. 21797) 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          3484         3634          147         >20.7
white             3484         4865          344         >21.6
v                 3640         5275          393         >19.7
b                 4460         4660          197         >20.5
u                 4255         4455          197         >21.0
w1                4050         9664          362         >20.7
m2                3845         5482          393         >20.4
w2                4871         5071          197         >21.8

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.02 in the direction of the 
burst (Schlegel et al. 1998).