RGS spectrum of HR1099
Home Watchouts Software requirements Installation Download Documentation Calibration Help

Artifacts in XMM-Newton time series analysis?

Care needs to be taken when adding or subtracting XMM-Newton light curves to ensure that the start and stop times of the two time series are simultaneous. By default, evselect starts a time series at the time when the first event is found in the extraction region. This leads to source and background time series generally having different start / end times. In addition, time series extracted from the different cameras on board XMM-Newton will be non-synchronous by default.

This non-synchronicity of time series can cause artifacts to be introduced when they are added or subtracted by programs such as the ftool "lcmath" (see Barnard et al. 2006, A&A submitted, astro-ph/0610035).

To avoid this problem we recommend that when time series are extracted by evselect the limits of the series are explicitely set on the command line, e.g.

evselect table=M2EVL.ds:EVENTS timemin=151160560 timemax=151162600 withtimeranges=yes withrateset=yes rateset=m2_lc.ds timecolumn=TIME timebinsize=10
In this case the same 'timemin' and 'timemax' values should be used for all of the time series which are later going to be combined.

Pages maintained by SAS librarian.
Any question about SAS should be addressed to the XMM-Newton help desk.

Updated on: February 19, 2007