User defined GTI for SPI analysis

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How to define a user GTI for SPI analysis

last update of this page: 28.02.2003

Here I describe how to create a good time interval, which is then used by the SPI analysis software. Using this, you can in- or exclude certain time periods in your analysis. This is particular interesting for short events, like GRBs.
  • create an empty GTI structure:
    dal_create obj_name="usergti.fits" template="GNRL-USER-GTI.tpl"
  • Fill some keywords (ftools command; you can of course also set the keywords by hand using e.g. fv):

    fparkey value=0.0 fitsfile=usergti.fits\[1] keyword=TSTART
    fparkey value=10000.0 fitsfile=usergti.fits\[1] keyword=TSTOP
    fparkey value=GOOD fitsfile=usergti.fits\[1] keyword=GTI_TYPE

    TSTART and TSTOP define the start and end validity of your selection, not the selection itself.
    The GTI_TYPE can be 'GOOD' (use the time specified in the user GTI file) or 'BAD' (exclude the time specified in the user GTI file)

  • open the fits file (e.g. with fv):
    fv usergti.fits
  • click on 'Table'
  • click on 'Edit'
  • select 'Insert' and then 'row'
  • insert as many rows as you want to have good time intervals
  • fill in the row either the UTC or the IJD or the OBT columns corresponding to your good/bad time you want to define. It is only necessary to fill ONE time format.
  • 'Save' the fits file
  • Now you can use the 'usergti.fits' file in your analysis; when you run spi_science_analysis, set the following parameters to activate your personal GTI (this example assumes that you defined the GTIs in UTC) :

    spi_gti_creation_use_gtis,s,ql,"DATA_GAPS USER",,,"Input GTI names of all SPI GTIs (ATTITUDE DATA_GAPS USER)" spi_gti_creation_usergtiname,s,ql,"usergti.fits[GNRL-USER-GTI]",,,"User defined GTI table" spi_gti_creation_usergtiformat,s,ql,"UTC",IJD|UTC|OBT,,"Time format used from user defined GTI table (IJD, UTC, OBT)"

In case of questions and comments: contact me.