If makeflaregti=Y, for all merged files (*MIEVLI*),
an additional call to evselect
(Fig 1) produces
a light curve of single events from CCDs in Imaging mode flagged with
REJECTED_BY_GATTI (with actual energy above 14 keV),
with time bins defined by flaretimebin (if that time bin is too
small to give reasonable statistics per bin, it will be increased
automatically).
This is aimed at finding efficiently periods of flaring activity when
the focal plane is illuminated by low-energy protons.
Those are mostly singles and are not cut-off by the mirror efficiency
above 10 keV (contrary to astronomical sources).
The result is divided by the area of the external CCDs
within the field of view, and expressed in cts/ks/arcmin
.
A fractional exposure column FRACEXP accounts
for incomplete time bins.
If globalflare=Y (default), timeseries are built for all MOS event lists in the current directory, then summed together (the ERROR columns are summed quadratically) to build a single global timeseries. This allows to apply the same GTI to both MOS instruments, and to improve the statistics in the timeseries.
This light curve is sent to tabgtigen
which selects all intervals
when the number of cts/ks/arcmin is lower than
flaremaxrate,
and produces a Good Time Intervals file.
This file is filtered to avoid intervals only one flaretimebin
long, which are usually negative fluctuations during a moderately
strong flare.
This file is NOT applied to the events list,
unless applyflaregti=Y.
The quiet level is around 0.8 cts/ks/arcmin.
The default value of flaremaxrate is conservative (to avoid
rejecting too many intervals) and should be all right in most situations.
The default value of flaretimebin is such that it covers an integer
number of frames (20). It should not be chosen too small if
TIME is not randomised (no 'T' option in randomize).
If applyflaregti=Y, the resulting Good Time Intervals are applied only if they total more than 10% of the exposure time. Otherwise the events list is left unscreened. This applies in particular to the bad pixels detection (Sect. 3.4).