[vsnet-grb-info 4090] Corrections for Swift/UVOT Exposure Times for GRBs 061110B and 061121

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  5899
SUBJECT: Corrections for Swift/UVOT Exposure Times for GRBs 061110B and 061121
DATE:    06/12/05 20:02:54 GMT
FROM:    Frank Marshall at GSFC  <marshall at milkyway.gsfc.nasa.gov>

F.E. Marshall (NASA/GSFC) reports on behalf of the Swift/UVOT team:

The exposure times for UVOT were reported incorrectly for GRB 061110B
in GCN Circ. 5803 and for GRB 061121 in GCN Circ. 5823 because of a
configuration problem in the instrument. The actual exposure times are close
to the nominal values of 100 s and 400 s (Page et al., GCN Report
15.1) respectively.

We caution users of UVOT data that data in the archives for exposures
taken between November 10 and November 22, 2006, have an incorrect value
for the frame time. As a consequence, the standard UVOT analysis tools
do not calculate dead time and anti-coincidence losses properly.
Additional details, including the proper technique for analyzing
these data, are available on the following web page:

  http://heasarc.gsfc.nasa.gov/docs/swift/uvot_frame.html.