[vsnet-grb-info 19228] GRB 170318A: Swift/UVOT Upper Limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  20914
SUBJECT: GRB 170318A: Swift/UVOT Upper Limits
DATE:    17/03/18 21:27:48 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld at ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) and B. Sbarufatti (INAF-OAB/PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 170318A
117 s after the BAT trigger (Sbarufatti et al., GCN Circ. 20904).
No optical afterglow consistent with the XRT position (Evans et al. GCN 
Circ. 20907) 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           117          266          147         >20.4
u_FC               329          552          220         >19.6
white              117         6605          363         >20.8
v                 2222         2241           19         >17.0
b                 2147         6400          216         >19.8
u                  329         6195          417         >20.1
w1                5790         5990          197         >19.4
m2                5585         5784          197         >19.3
w2                2197        11766          560         >20.4

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.97 in the direction of the 
burst (Schlegel et al. 1998).