RGS spectrum of HR1099
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I observe a shift in time between OM and other light curves.

The timing in the time series produced by omfchain (files P*TIMESR*) is expressed in seconds elapsed from a reference epoch given by the FITS keyword MJDREF. For data processed with SAS v6.0 or earlier, this reference time is not correct.


SAS v6.0: MJDREF = 5.08140007312960E+04
Correct value: MJDREF = 5.08140000000000E+04

The difference is 63.1839744 seconds.

Therefore, users processing Fast Mode OM data with SAS v6.0 or earlier must correct manually the reference time keyword if they want to compute an absolute time scale. The relative timing is, however, correct.

This bug will be fixed in the next public SAS version (6.1).

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Updated on: June 18, 2009