espfilt reads an event file from either MOS or pn, calculates the light curve in both the FOV and the corner data and, from those, determines which time periods are contaminated with soft proton flares. Two different methods can be applied.
The histogram method is an implementation of the method proposed in Kuntz & Snowden (2008). This method builds a histogram of the count rate from a binned and/or smoothed light curve. In the presence of short proton flares, the peak of that histogram represents the quiescent rate, while the flared intervals form a tail to higher values. The algorithm fits the peak of the histogram with a gaussian and sets as “flared” all intervals further than a user defined number of from the peak.
The ratio method is an implementation of the method proposed in De Luca & Molendi (2004). This method looks at the ratio of the count rate in an annulus just inside the FOV to that in the corners. Intervals for which that ratio exceeds some user determined value are considered “flared”.
For both methods espfilt forms a GTI file which is then used to remove the flared intervals.
It should be noted that for a MOS exposure, the histogram method will run in 10 seconds, while the ratio method may require 5 minutes.
20ptThe current location should be the working directory.
20pteventfile – The name of the input event file.
20ptwithoot – If true then, for pn apply GTI to OOT event file as well.
20ptootfile – Input OOT event file.
20ptelow – The minimum spectral channel for the light curve. For the histogram method this should be 2500; for the ratio method it should be 8000.
20ptehigh – The maximum spectral channel for the light curve. For the histogram method this should be 8500; for the ratio method it should be 12000.
20ptkeepinterfiles – If true then intermediate files are kept.
20ptmethod – Eiither histogram, the default, or ratio.
For the histogram method:
20ptwithsmoothing – If yes the light curve is smoothed by smooth seconds. The default is no.
20ptsmooth – The number of seconds by which to smooth the light curve if withsmooothing is true. The default is 60.
20ptrangescale – The width of the region over which the Gaussian is fit to the histogram. The default is 6, which is good for the MOS. We recommend 15 for the pn.
20ptallowsigma – The range of to be accepted as being “flare-free”.
For the ratio method:
20ptwithbinning – If yes the light curve is binned by binning seconds. The default is no.
20ptbinsize – The number of seconds by which to bin the light curve if withbinning is true. The default is 60. For the ratio method:
20ptratio - The threshold ratio of FOV/corner over which the interval is considered to be flared.
20ptlimits - A two element parameter setting the values over which to form the histogram. This should probably not be tampered with unless you really know what you are doing.
20ptx-corevc.fits The filtered event list for the corner data.
20ptx-corimc.fits The diagnostic image of corner data after filtering.
20ptx-corlc.fits The light curve for the corner data.
20ptx-allevc.fits The filtered event list for all the data.
20ptx-allevc-oot.fits The filtered event list for all the data if withoot=Y
20ptx-fovimc.fits The diagnostic image of FOV data after filtering.
20ptx-fovlc.fits The light curve for the FOV data.
20ptx-gti.fits The GTI file containing the intervals without soft proton flares.
20ptx-hist.qdp The graphical output of the light curve.
If keepinterfiles is true, the following are also produced:
20ptx-corev.fits The unfiltered event list for the corner data.
20ptx-corim.fits The diagnostic image of corner data before filtering.
20ptx-fovim.fits The diagnostic image of FOV data before filtering.
20ptx-gti.txt The ASCII version of the GTI file.
20ptespfilt eventfile=mos2S002.fits method=histogram elow=2500 ehigh=8500 withsmoothing=yes smooth=51 rangescale=6.0 allowsigma=3.0 keepinterfiles=false
20ptespfilt eventfile=pnS003.fits method=histogram elow=2500 ehigh=8500 withsmoothing=yes smooth=51 rangescale=15.0 allowsigma=3 withoot=Y ootfile=pnS003-oot.fits keepinterfiles=false