Fitted XMM-Newton Time Correlation Files


Generation of new fitted Time Correlation Files (TCX) for all XMM-Newton observations: Do I need to care about it?

Improved TCX files are being generated for all the ODFs in the XMM-Newton Science Archive (see also issues #89 and #109 of the XMM-Newton Newsletter). They reduce the scatter of absolute timing measurements in individual observations from 100 to less than 70 micro-seconds (1-sigma). Users are also referred to the EPIC Status of Calibration document (Sect. 8) for further details.

In case of need for such a high precision absolute timing analysis, please, find below instructions on how to make sure that you have access to the new fitted TCX files.

How do I know if my ODF needs a new "fitted" TCX

All ODFs from observations performed in revolution 1915 and above have the new fitted TCX files included.

Information about the range of earlier revolutions for which new fitted TCX files have been generated is available here.
Revolutions for which the fit of the TCX failed and that will need to be inspected individually again at the end of the exercise are marked as well.

In addition, another table lists all ODFs, before revolution 1915, that already have the new fitted TCX file added and that are available (proprietary rights permitting) in the XSA.

All ODFs generated with a new fitted TCX have the following FITS keyword in the TCX file header:

TCXVER=1.4 (or higher)

My ODF does not contain a new fitted TCX. How do I get and use the new TCX nevertheless?

If your ODF is included in the above list of ODFs with new TCX added, then you probably still have an old version. Please check for a new one in the XMM-Newton Science Archive (XSA).

If your ODF is not included in the above list, this may be because of different reasons, namely:

  • The new fitted TCX file has been generated but has not yet been included into the ODF.
    Please, follow the steps here below to 'manually add' the new TCX file:
    • Check the revolution to which your ODF belongs.
    • Check if the new fitted TCX file is generated, as per this table.
    • Download the corresponding TCX file.
    • Rename it to the corresponding ODF TCX constituent (in the directory where the ODF is already exploded):
      • Downloadable TCX files are named: RTX_RRRR.FIT
      • As ODF TCX constituents they have to be re-named to: RRRR_Obsidnumbr_SCX0000TCX.FIT
    • Process your ODF as usually (starting e.g. according to the SAS Start-up Thread).
  • No new fitted TCX file for its revolution has been generated by the SOC yet. The case is under study and the TCX should be generated soon. Contact the SOC (see below) if you need further information. Please remember to mention the Observation Id of the ODF.

Note that if your ODF does not contain a TCX constituent you can still process it with SAS, but the time correlation used will not be the fitted one.

In case of any doubts or further questions, please, do not hesitate to contact the SOC via the XMM-Newton HelpDesk.