Timing Analysis

This section will demonstrate some basic timing analysis of EPIC image-mode data using the Xronos analysis package. For this exercise, the central source from the observation of G21.5-09 (Obs ID 0122700101) is used. These examples assume that the source's lightcurve has been made as in § 7.3.2, but with timebinsize set to 1 and makeratecolumn set to no; the name of this file assumed to be source_ltcrv.fits.

For the aficionado, the task barycen can be used for the barycentric correction of the source event arrival times.

The Xronos tools can be access through the Hera GUI by clicking on XRONOS in the Available Tools panel.

Figure 7.8: Light curve for the source analyzed as in § 7.3.2.

Figure 7.9: Power spectrum density for the source analyzed as in § 7.4.

To make a binned lightcurve with the Xronos GUI:

1)

Call lcurve from the Available Tools panel.

2)

Enter the Series 1 filename, in this case source_ltcrv.fits. Set ``Name of the window file'' to '-' (no quotes), ``Newbin Time or negative rebinning'' to 500, and the ``Number of Newbins/Interval'' to 430. Enter the name of the output file; for this example we will call it lightcurve_binned.fits. Next to ``Do you want to plot your results?'', select ``No''.

3)

Click ``Run''.

The output can be viewed with fv by right-clicking on the filename and selecting the ``Edit/Display File'' option. Output is shown in Figure 7.8.

To make a binned lightcurve with Xronos in the Command Window:

lcurve nser=1 cfile1='source_ltcrv.fits' window=- dtnb=500 nbint=450
$$ outfile='lightcurve_binned.fits' plot=no

where

nser - number of time series
cfile1 - filename first series
window - name of window file (if a subset of the time series is required)
dtnb - bin size (time)
nbint - number of bins per interval
outfile - output file name (FITS format light curve)
plot - plot flag

The output can be viewed with fv by right-clicking on the filename and selecting the ``Edit/Display File'' option. Output is shown in Figure 7.8.

To calculate power spectrum density with the Xronos GUI:

1)

Call powspec from the Available Tools panel.

2)

Enter the Series 1 filename, in this case source_ltcrv.fits. Set ``Name of the window file'' to '-' (no quotes); next to ``Newbin Time or negative rebinning'', enter 100; for the number of newbins/interval, enter 300; for the number of intervals/frame, enter INDEF. Next to ``Rebin results?'', enter 5; next to ``Do you want to plot your results?'', select ``No''. Enter the name of the output file, in this case, power.fits.

3)

Click ``Run''.

The output can be viewed with fv by right-clicking on the filename and selecting the ``Edit/Display File'' option. Output is shown in Figure 7.9.

To calculate power spectrum density with Xronos in the Command Window, type:

powspec cfile1='source_ltcrv.fits' window=- dtnb=100.0 nbint=300
$$ nintfm=INDEF rebin=5 plot=no outfile='power.fits'

where

cfile1 - filename first series
window - name of window file (if a subset of the time series is required)
dtnb - bin size (time)
nbint - number of bins per interval
nintfm - number of intervals in each power spectrum
rebin - rebin factor for power spectrum (0 for no rebinning)
plot - plot flag
outfile - output file name (FITS format power spectrum)

The output can be viewed with fv by right-clicking on the filename and selecting the ``Edit/Display File'' option. Output is shown in Figure 7.9.

To search for periodicities in the time series with the Xronos GUI:

1)

Call efsearch from the Available Tools panel.

2)

Enter the Series 1 filename, in this case source_ltcrv.fits. Set ``Name of the window file'' to '-' (no quotes); next to ``Epoch'', enter INDEF. Set ``Period'' to 20, ``Phasebins/period'' to 10, ``Number of Newbins/Interval'' to INDEF, ``Number of periods to search'' to 100, and ``Resolution for period search'' to INDEF. Next to ``Do you want to plot your results?'', select ``No''. Enter the name of the output file, in this case, efsearch.fits.

3)

Click ``Run''.

To search for periodicities in the time series with Xronos in the Command Window, type:

efsearch cfile1=source_ltcrv.fits window=- sepoch=INDEF dper=20 nphase=10
$$ nbint=INDEF nper=100 dres=INDEF plot=no outfile=autocor.fits

where

cfile1 - filename first series
window - name of window file (if a subset of the time series is required)
sepoch - value for epoch used for phase zero when folding the time series
dper - value for the period used in the folding
nphase - number of phases per period
nbint - number of bins per interval
nper - number of sampled periods during search
dres - sampling resolution of search
plot - plot flag
outfile - output file name (FITS format)

To calculate the autocorrelation for a time series with the Xronos GUI:

1)

Call autocor from the Available Tools panel.

2)

Enter the Series 1 filename, in this case source_ltcrv.fits. Set ``Name of the window file'' to '-' (no quotes). Set ``Newbin Time or negative rebinning'' to 24, ``Number of Newbins/Interval'' to 2048; ``Number of Intervals/Frame'' to INDEF; and ``Rebin results?'' to 0. Next to ``Do you want to plot your results?'', select ``No''. Enter the name of the output file, in this case, autocor.fits.

3)

Click ``Run''.

To calculate the autocorrelation for a time series with Xronos in the Command Window, type:

autocor cfile1=source_ltcrv.fits window=- dtnb=24.0 nbint=2048 nintfm=INDEF
$$ rebin=0 plot=no outfile=auto.fits

where

cfile1 - filename first series
window - name of window file (if a subset of the time series is required)
dtnb - bin size (time)
nbint - number of bins per interval
nintfm - number of intervals to be summed in each autocorrelation function
rebin - rebin factor for autocorrelation function (0 for no rebinning)
plot - plot flag
outfile - output file name (FITS format autocorrelation spectrum)

To calculate statistical quantities for a time series with the Xronos GUI:

1)

Call lcstats from the Available Tools panel.

2)

Enter the Series 1 filename, in this case source_ltcrv.fits. Set ``Name of the window file'' to '-' (no quotes). Set ``Newbin Time or negative rebinning'' to 6, and ``Number of Newbins/Interval'' to 8192.

3)

Click ``Run''.

The statistics will be printed in the Command Window.

To calculate statistical quantities for a time series with Xronos in the Command Window, type:

write the output to an ASCII file fname. (Leave off the $>$ fname to write the results to the screen.)

lcstats cfile1=source_ltcrv.fits window=- dtnb=6.0 nbint=8192

where

cfile1 - filename first series
window - name of window file
dtnb - integration time (binning)
nbint - number of bins
fname - output file name