Usage of the predefined Bad Time Intervals

Read this to know how to make proper selection of the science windows that should be used in your analysis.

Different things could happen to the instrument during a particular science window. To inform the user on any unusual things that he should be aware of, the list of time intervals which had some anomalies (bad time intervals) has been created and is kept in the latest$REP_BASE_PROD/ic/ibis/lim/isgr_gnrl_bti_*.fits file.

In this list you find the following 7 categories:

• IBIS_CONFIGURATION - is to flag the change of configuration. Its time interval is short, just the duration of the switch of parameters. Column COMMENTS gives changes on the 4 main parameters (given in file instr_settings.txt), by order of importance:
  • rise-time selection
  • VETO configuration
  • low threshold adjustment
  • COMPTON window
  It is recommended not to use in your analysis any science window with such a problem.

• ISGRI_RISE_TIME - indicates that on-board cut on rise-time is too low, so we don't have arf and rmf for this case.

• BELT_CROSSING - indicates that belts are seen in VETO or ISGRI count-rates.

• SOLAR_FLARE - indicates periods where a strong solar affected part of the data.

• VETO_PROBLEM - contains periods when VETO had a strange behaviour with a count-rate much lower (or higher) than expected. If it is lower, then less ISGRI events were killed, and hence science count-rate is higher. Thus, user can analyze these data but must not rely on the flux (dead-time can be wrong). Also 2 cases of "voltage breakdown" are added to this category.

• IBIS_BOOT - indicates that IBIS has been restarted from OFF state unexpectedly.

• MISCELLANEOUS - For the moment there are cases where we have problems with the time values, and all others are related to the drop of PICsIT counters.

For the most conservative data analysis use the following value of the SCW1_GTI_BTI_Names parameter:

 SCW1_GTI_BTI_Names="IBIS_CONFIGURATION ISGRI_RISE_TIME BELT_CROSSING SOLAR_FLARE VETO_PROBLEM IBIS_BOOT MISCELLANEOUS"