[vsnet-grb-info 16764] GRB 150720: Swift/UVOT Upper Limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18045
SUBJECT: GRB 150720: Swift/UVOT Upper Limits
DATE:    15/07/22 16:14:07 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <siegel at swift.psu.edu>

M. H. Siegel (PSU) and E. Sonbas (NASA/GSFC/Adiyaman Univ.)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150720
142 s after the BAT trigger (Sonbas et al., GCN Circ. 18037).
No optical afterglow consistent with the XRT position (Beardmore et al.,
GCN Circ. 18040)  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)         142          292          147         >20.5
u (fc)             301          551          246         >20.4
white              142         1551          392         >21.2
v                  631         1601          117         >19.3
b                  557         1527           97         >19.6
u                  301         1502          324         >20.2
w1                 680         1478           97         >19.3
m2                 655         1623          114         >19.8
w2                 606         1577          117         >19.6

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.68 in the direction of the burst
(Schlegel et al. 1998).