XIS time assignment is calibrated referring to the HXD PIN data, whose absolute time assignment was calibrated with the Crab observations. Calibration status of the XIS time assignment is described below. The description applies to HEAsoft 6.3 (suzakuversion 27Jun2007_V5.0) or later except for the timing mode, which applies to HEAsoft 6.3.1 (suzakuversion 24Jul2007_V6.0) or later.
1. Normal mode data with a window (but no burst) option
XIS has time resolution of 2 sec (1/4 window) or
1 sec (1/8 window) when the window option is applied.
Its time assignment was verified to be correct referring
to the HXD PIN data within the accuracy of the XIS time
resolution.
2. Normal mode without options
Because the time assignment of XIS is consistently
implemented with and without the window option,
we consider that the time assignment of XIS
without the options is also consistent with HXD PIN.
Direct comparison of the XIS time assignment with HXD PIN
is not yet done for the normal mode data without
options because of lack of the appropriate data.
3. Normal mode with a burst option
Artificial dead time is introduced with the burst
option every 8 sec (or 2 sec with 1/4 window option,
1 sec with 1/8 window option). Ver 2.0 software is
designed to handle the dead time and the subsequent
shift of the center of the exposure time correctly.
However, the implementation is not verified yet
with real data.
4. Timing mode
Usage of the timing mode is strongly discouraged,
and its calibration remains at a primitive stage.
Implementation of the software was checked with the
Her X-1 data, from which the pulsation (1.24 sec)
was detected at a consistent period with HXD PIN.
However, absolute time assignment is not calibrated
yet, including whether its full time resolution of
7.8 ms is really achieved.