OGIP Memo OGIP/94-010
ROSAT data analysis using xselect and ftools

Version: 1.1.1
(2011 Feb 14)

ROSAT Guest Observer Facility
Office of Guest Investigator Programs
Laboratory of High Energy Astrophysics
NASA Goddard Space Flight Center
MD 20771
edited by T.J.Turner


Contributors to the ROSAT software detailed here include Banashree Seifert, Rehana Yusaf, Ian George, Larry Brown, Bruce O'Neel, Jim Ingham, Alan Smale, Lorella Angelini, Bruce O'Neel, S.Snowden, K. Arnaud, T.J.Turner, Mike Corcoran.


Version Release Date Comments
1.1 1996 Apr 2 Original Version
1.1.1 2011 Feb 14 updated Region Selection (Sec 3.1.2); removed out of date discription of SAOImage DS9; other minor updates


1  Introduction
    1.1  ROSAT File formats
    1.2  U.S. Sequence Naming Conventions
    1.3  Coverting Old style German events files to RDF
Reading the data into Xselect
Image Analysis
    3.1  Making an Image from the Events file
        3.1.1  Image subselections
        3.1.2  Region selection
Timing Analysis
    4.1  Light Curve Extraction
    4.2  Simple Time filtering
    4.3  Barycentric correction
Spectral Analysis
    5.1  Extracting a Spectrum
        5.1.1  Spectral filters
Preparing for XSPEC, XRONOS and XIMAGE
    6.1  Prior to XSPEC
        6.1.1  Off-Axis Spectra
        6.1.2  Grouping or Rebinning the Spectral Data
    6.2  Reading the Data into XSPEC
    6.3  Reading the events files or time series into XRONOS
    6.4  Reading the events files or images in XIMAGE
7  More Advanced Analysis
    7.1  Screening/Rescreening the Data
        7.1.1  Saving screened events
    7.2  Exposure Correcting an image - pcexpmap and hriexpmap
    7.3  Comparing the radial profile data to the psf
        7.3.1  extrpsf
        7.3.2  calcrpsf
    7.4  Performing mathematical operations on PHA files
    7.5  Creating particle background spectra
Quick Summary
    8.1  Useful xselect commands
    8.2  ROSAT ftools
    8.3  Other FTOOLS for ROSAT Analysis
An Example Xselect Session

Chapter 1

As the ROSAT data have been distributed as FITS files, one can easily and quickly analyze ROSAT data using the xselect analysis system developed for ASCA.
xselect is a command-line interface to ftools. Its major role is to allow easy manipulation of the data (storing intermediate data products internally during use). It allows quick and easy extraction of images, light curves and spectra from the events files, with easy application of filters, data screening and other selection criteria, and easy viewing of intermediate data products (images, light curves and spectra). At present, xselect runs under SunOS-4, DEC/Ultrix, DEC/OSF and VAX/VMS. xselect runs optimally with 24 MB of memory.
The ftools which you almost always need in your analysis are spawned from xselect. There are also a number of ftools which you may need, depending on your particular analysis requirements, these can be run at the system level.
This document outlines the analysis of ROSAT data using the ftools and xselect software. It assumes that the session is running on a terminal capable of supporting X-windows.
Please note that the xselect program is still evolving very fast so some things illustrated below will change in future releases. If you have suggestions for ROSAT-related improvements or spot bugs then please send them to turner@lheavx.gsfc.nasa.gov.
This document assumes that ftools and xselect are available standalone on your system. If they are not, you need to install them before you begin. Both ftools and xselect can be downloaded as part of the HEASARC's HEASoft package To obtain the software, installation guide and full Users Manual for these tools please see the HEASoft Download page. For help with download and installation please contact use the HEASARC Feedback form to contact the ftools e-mail help facility.
This document does not cover all of the sophisticated functionality provided by ftools/xselect, but covers some of the basics steps you are likely to need during your ROSAT data analysis. Please see the xselect Users Guide available on the xselect home page or online help for a detailed description of the more advanced features of the software.

1.1   ROSAT File formats

As ROSAT data processing software has been upgraded during the course of the mission, the file formats and the sequence-naming conventions have evolved. Data exist in three formats at the current time.
Because both MPE and the USRSDC have adopted RDF, the format of the ROSAT data products are now independent of where the data were processed; thus users of ROSAT data processed at MPE will easily be able to interpret and use ROSAT datasets processed in the US, and vice-versa. Eventually the ROSAT data archive will be overwritten such that all data are in the same Rationalized Data Format -RDF). In addition, RDF is being adopted by numerous other missions (EINSTEIN, ASCA and XTE) which means that software which can interpret and analyze ROSAT data should be able to interpret and analyze data from these and other missions.
The files distributed on the RDF data tape adhere to the FITS standard as described in the NASA/OSSA Office of Standards and Technology (NOST) draft 100-0.3b, "Implementation of the Flexible Image Transport System (FITS)," dated November 6, 1991. The ROSAT files use FITS primary images and FITS IMAGE extensions and ASCII and BINARY table extensions, although most data (apart from images) are stored in BINARY table (BINTABLE) extensions.
Detailed descriptions of each of the Rev0 and RDF files can be found in the Data Products Guide.

1.2  U.S. Sequence Naming Conventions

A key difference between early Rev0 format data and later Rev0 format data pertains to the way separate observation intervals (called "OBIs") are combined. Initially, all available OBIs were used to produce a single set of data products, later, OBIs which were part of the same sequence but which occurred in different öbserving seasons" (i.e.,  6 months apart) were processed and distributed separately.
All data processed by the U.S. RSDC using SASS versions 3_0 through 5_9 (Rev0) used file names of the form:

where:         r                - stands for ROSAT

               <detector-code>  - code for detector/filter:
                                        h - HRI
                                        p - PSPC
                                        f - Filtered PSPC.

               <ROR>           - 6-digit Rosat Observation Request number

              <extensions>     - additional characters specifying "type"
                                  of data.

In later Rev0 data, observations conducted over different öbserving seasons" (i.e., over gaps of several months) were no longer combined to form a single data set. Additional observations, known as ädd-ons", were processed separately. The sequence-naming convention became:
                r<detector-code><ROR><add-on number><extensions>
where the two additional digits added after the ROR number are:
                <add-on number> - 00 indicates the first segment,
                                - 01 indicates the second segment,
                                - 02 indicates the third segment,
                                    and so on.

An additional identifier has been inserted into the RDF file names to indicate both "split" Rev0 sequences and "mispointed" observations (those for which the telescope was not pointed at the intended target). The RDF FITS file names have the form:
where obs-code has replaced add-on number:
  <obs-code> =

1.3  Coverting Old style German events files to RDF

xselect can handle both the old style US FITS files (hereafter called US Rev0), and the new RDF FITS format files. In the Rev0 case the events for sequence "rp700105" for example are in the file rp700105.fits or rp70010500.fits, depending on what version of SASS was used for the data processing. In the RDF case the events are in a file with a name like rp700105n00_bas.fits or rh110267n00_bas.fits, the "basic" file.
Old format German events files must be converted to RDF format prior to starting xselect. To do this run
Enter file name: wp700559_events.tfits
Infile is wp700559_events.tfits
ONTIME :    2393.0000000000
Number of rows in STDGTI table:   2
Number of rows in STDEVT table:   28845
New file wp700559.fits written

Old German format archive images can also be converted to RDF FITS format, the converted image can then be displayed via SAOImage DS91.
        Name of German ROSAT image FITS file[ ] wp700559_image1.ifits

This creates a FITS image of name wp700559_im1.fits which can be displayed using SAOImage DS9 at the system level, i.e.
        ds9 wp700559_im1.fits

Chapter 2
Reading the data into Xselect

starts up xselect. First thing you'll see is:
            ** xselect V1.3 **
            > Enter session name >[xsel] session1
The xselect program was originally written for the analysis of ASCA data but use of FITS formats for the ROSAT data files has made it relatively easy to adapt the xselect software to handle ROSAT data.
Session names are used as the first letters of temporary files so that you can run multiple sessions of xselect from the same directory so long as you give each session a different name. You can save the xselect session (you will be asked if you wish to save the session upon exiting it) and later start it up again and continue from where you left off: in the above example, if you had saved an xselect session called 'session1' before, then it will ask you if you wanted to restore the saved session.
It should be stressed that images, light curves, spectra and events files extracted are temporary files and will be lost when you exit from xselect unless you have saved each (using ßave spectrum", ßave curve" etc) or unless you save the xselect session.
xselect initially comes up with the mission set to ASCA, this and other xselect defaults will change when you read in the events file, and xselect reads the header.
             xselect> read events
> Enter the Event file dir >[] ./
> Enter Event file list >[] rp100000n00_bas.fits
(the data need not be in the current working directory and you can reset the default data directory using 'set datadir' /whatever/dir at any time)
xselect will display the new defaults and a summary of the datafile you have read in, the following shows an example of reading an RDF events file:
             xselect> read events

Got new mission: ROSAT and new instrument: PSPCC
> Reset the mission and instrument? >[yes]
 This is ROSAT

 Notes:  xselect set up for      ROSAT
 Keywords for time and pha are  TIME       PI
 Units of time are              SECONDS
 Keywords for images are          X          Y

Setting: IMAGE binning    =   15
         WMAP binning     =   15
         Energy Column    =  PI
         Energy rebinning =    1
         WMAP keywords = DETX       DETY

Getting Min and Max for Energy Column...
Got min and max for PI:     1    500

Number of files read in:   1

******************** Observation Catalogue ********************

Data Directory is: /testdata/
HK Directory is: /testdata/

      1 PSPCC    XRT/PSPC 11/04/94 .310590 .188E+04 110590 .188E+04 

If you are reading in a US Rev0 format dataset then you will see a slightly different output, the differences are in the PI range and in the names of the keywords containing the information shown in the Observation Catalogue.

Getting Min and Max for Energy Column...
Got min and max for PI:     0    255

Number of files read in:   1

******************** Observation Catalogue ********************

Data Directory is: /testdata/
HK Directory is: /testdata/

      1 PSPC     07/10/93 .208E+03 .693E+02 US701424 .962E+04

In some cases xselect cannot fit the information into the formated observation catalog display, and a field of wild cards (*) may result. If this occurs you can allow an unformated display (which may wrap around to 2 lines) by using
             xselect> read events filename tdisp=no
Notes & Warnings:

Chapter 3
Image Analysis

3.1  Making an Image from the Events file

You may wish to start your analysis by looking at the ROSAT image, and while 'standard' images are provided with the archival dataset you will probably wish to make your own spatial binning and energy band selections.
             xselect> extract image
             xselect> saoimage
you will now have extracted a full-band image with the default spatial binning and displayed it in an SAOImage DS9 window.
You can save this image by :
             xselect> save image sourceimage.fits

3.1.1  Image subselections

Image can be extracted under pha, time, spatial or housekeeping filters, pha is loosely used to mean pha or pi and so
             xselect> extract image phalcut=12 phahcut=200
extracts an image using PI channels 12 to 200 etc.
             xselect> filter time file xsel_cursor_gti.xsl
             xselect> extract image
extracts an image using only the good times previously saved in the file xsel_cursor_gti.xsl (see Chapter 4 for details of how to make such a time filter file).
As the raw sky image has 0.5 arcsec pixels, and the binning factor is 15, for example the default image is created as 1024 x 1024 for the PSPC.
To change the resolution of the image you must reset the spatial binning
             xselect> set XYBINSIZE 8 (4 arcsec bins)
Care is necessary when switching the xybinsize and using regions defined in SAOImage DS9. xselect will assume that the regions that it is using for any extraction were defined on an image binned up by the factor given by the current xybinsize so if you create a region then change the xybinsize you will not get correct results.
To extract a sub-image at high resolution one can reset xysize. Images are constrained to be square and so xysize requires the dimension, in output pixels, of the side of the output image. Each output pixel is of the size determined by xybinsize. For example, if you are working with the sky image (i.e. Coordinates for the image are X Y) xybinsize is set to a factor of 8, so each output pixel will be 8x0.5 = 4 arcsec. Setting xysize to 1000 will yield an image 1000x1000 4 arcsec pixels, or 66.7 arcmin on each side.
As the limit of xysize is 1200, you may wish to recenter your output image, in order to get high resolution information about sources at the edge of the field-of-view. To do this, set xycenter in raw pixels. For the ROSAT PSPC the center pixel in raw 0.5 arcsec sky pixels is 7680 7680.

xsel:ROSAT-PSPC > set xycenter 6530 6240

Remember to SET XYSIZE, or the extractor will ignore the centering

xsel:ROSAT-PSPC > set xysize 800
xsel:ROSAT-PSPC > extract image
 Extractor 1.0q
 XPI 2.1t
 Doing file: /testdirectory/rp700105.fits
 Getting FITS WCS Keywords

show st100% completed
    Total      Good    Bad: Region      Time     Phase       PHA
   124810    109163          14930         0         0       717
   Grand Total      Good   Bad:  Region      Time     Phase       PHA
        124810    109163          14930         0         0       717
 Total Counts for image :   109163
 Total Time for image :     9625.0000000000
 Total Counts/Time for image :     11.341610389610

To make an image in detector coordinates
             xselect> set image detector
and then proceed as before. Both PSPC and HRI datasets are oversampled to 0.5 arcsec pixels in the sky image (raw images sizes are thus 15360 and 8192 respectively). In detector cordinates they are 0.934 and 0.600 arcsec per pixel, for the PSPC and HRI, respectively.

3.1.2  Region selection

Once the desired image is displayed in the SAOImage DS9 window you can select a subregion of interest. Subregions can either be included or excluded, contiguous or non-contiguous. For information on defining regions using SAOImage DS9, see the SAOImage DS9 Documentation, available at http://hea-www.harvard.edu/RD/ds9/. The current version of xselect  uses cfitsio filtering and supports all the regions described in the "Spatial Region Filtering" section of the HEADAS help file. If you've defined a subregion in SAOImage DS9 and saved it to the ASCII file mysource.reg then to tell xselect to use your region file :
             xselect> filter region mysource.reg
You can add other region files simply by repeating this command, but remember to use the reset button to clear old saved cursors. To remove a region file that you don't want to use :
             xselect> filter region "-mysource.reg"
and to clear all the regions in filter :
             xselect> clear region all
Assuming that you have set the region filter to be mysource.reg you can now remake the image using photons only from the mysource.reg area :
             xselect> extract image
             xselect> SAOImage DS9
Region files are simple ascii format files and can be edited (with care). An example of a region file from SAOImage DS9 is

# /test_data/xsel_image.xsl
# Tue Sep  30 17:18:03 1994
# shape x, y, [x dimension, y dimension], [angle]

For detailed image analysis the extracted image, or the events file, must be read into ximage, which is described briefly in Chapter 6.

Chapter 4
Timing Analysis

4.1  Light Curve Extraction

As for images, light curves can be extracted for the whole field, or filtered through a region descriptor and /or additional housekeeping filters and phalcut and phahcut specifications. The time bin that will be used is "binsize", the current default can be seen in the ßhow status" summary and it can be reset using e.g. ßet binsize 1000" for 1000 second bins. You can specify a minimum limit for partial bins, as a fraction of "binsize". For example
             xselect> extract curve exposure=0.2
will include partial bins of 200 seconds exposure or greater, while binsize is set at 1000 seconds.
             xselect> set device /xw       (/xterm will also work)
             xselect> plot curve
will plot the temporary light curve file. The x-axis is seconds since the beginning of the observation and the start time in spacecraft clock seconds is written at the top of the plot.
You will be left with the "PLT > " prompt. At this point you can use standard PLT commands, ( i.e. those used in the QDP plotting software- which some users may be familiar with). Useful commands include
                PLT> r x 1.234e5 2.468e5
                PLT> r y -0.1 5.
which reset the x and y axes to zoom into some interesting part of the lightcurve.
In some cases the user will wish to define a region of interest and extract the events from that region without binning the data. The extracted and saved mini-events file has the highest time resolution possible for those data, and can be read by XRONOS. This is the preferred method when doing complicated timing analysis since it avoids the danger of introducing spurious binning effects.

4.2  Simple Time filtering

To define time intervals for inclusion/exclusion having already extracted the light curve
             xselect> filter time cursor
plots the light curve in cursor time selection mode; the user will see
  - click to include a time region
c - to cancel cursor selection
e - makes the selection excluded
l - puts cursor on the left
r - puts cursor on the right
x - to exit cursor selection
p - to return to PLT prompt
  - click outside the plot to cancel a selection

Enter QUIT at PLT prompt to continue

and after exiting from PLT > a file of the time selections will be already added to the filters (type 'show status' to see that this is so).
To enter times by hand use 'filter time' MJD,SCC,UT which allow you to enter timing filters by HAND in MJD, Spacecraft Clock time, or UT. To use times from a (previously saved) file 'filter time' FILE. The associated 'save' commands are now grouped into 'save time cursor', and 'save time hand'. The associated clear commands are grouped under 'clear time'. Once you have saved (say) cursor times to a file, you can use those time selections again in the current or in future sessions by the command 'filter time file' thus
             xselect> filter time file gti1.xsl
will apply the times saved in the file gti1.xsl, while
             xselect> clear time file gti1.xsl
will clear that filter.
You can check your work by creating a lightcurve using just the selected time intervals :
             xselect> extract curve
             xselect> plot curve

4.3  Barycentric correction

For detailed timing analysis you will wish to apply a barycentric correction to events of interest.
The correction programs work directly on FITS files and are called are  bct (Barycenter Correction Table: corrects the times in the orbit table at the barycenter) and  abc (Apply Baycentric Correction: applies the correction to the arrival time of the photons in the events list at the barycenter). Invoking a script, rosbary, the two tasks can be run in sequence.
The most likely application is that users will extract a mini-events file for the photons of interest and then correct this before entering XRONOS.
This task computes the barycentric correction on the times contained in the orbit file. The times in the orbit file are sampled every 60 seconds. This task takes as input:
This program makes use of the JPL DE200 ephemeris given as a FITS binary table (Standish,M.,1982 Astr. Ap.,114,297).
This task corrects the arrival times of the photons, in the EVENT extension and the times in the GTI extension, for the SSC-UTC relation and uses the correction table created from  bct to correct the arrival time at the barycenter. The Barycentric correction is computed by a linear interpolation between the corrected orbit times (output from  bct). If a photon falls outside of the orbit interval a warning is issued together with the photon time. This task takes as input:
 bct needs to be run before  abc.
This script runs  bct and  abc in sequence The input paramters are:
orbit filename (FITS ext SPORB or EPHEM) (input file)
output correction table filename
RA hh mm ss.s or degrees in 2000 equinox
DEC dd mm ss.s or degrees in 2000 equinox
event filename (FITS EXTNAME EVENTS or STDEVT) (input file)
output corrected event filename
rosbary (and bct and abc) will work on the Rev0 US files, the RDF format files and will handle the German orbit files. However, users need to convert the German events files to RDF format before running these tasks.
For detailed timing analysis the time series or events file can be read in xronos, which is brielfy described in Chapter 6.

Chapter 5
Spectral Analysis

5.1  Extracting a Spectrum

When all desired filters are in place, then you are ready to extract a spectrum. This spectrum should be created from the PI column in the event file (the keyword for pha should be set to PI, if this is not the case, 'set phaname PI') the option for the data to be regrouped is offered when the spectrum is saved (grppha will allow you to reset the grouping at a later stage, so answering yes to the grouping is not going to constrain your spectral analysis).
             xselect> extract spectrum
             xselect> save spectrum source.sp
When using a RDF PSPC dataset you will see that the temporary spectral file made by xselect is 500 channels, and can be examined using 'plot spectrum'. As noted in section 3.1, when you save an RDF spectrum it is truncated to 256 channels which can be fit in xspec.
When extracting an HRI spectrum, you will extract the full 16 channels spectrum, and you will be offered a default rebinning down to a single channel, on saving this spectrum. It is recommended that this rebinning be used, if the user wishes to fit the HRI data using the standard single channel HRI matrix (seee section 6.1 for details on response matrices available from legacy).
The saved spectrum can be read into xspec directly. You will see that the spectral file contains a small map image in the primary array, showing where on the detector the events in the PHA or PI file originated. This weighted map is known as the WMAP, and is used by pcarf for generating an accurate ancilliary file which is used in conjunction with the photon redistribution matrix in the spectral fitting process.

5.1.1  Spectral filters

A variety of filtering commands are available as qualifiers for a spectral extraction. These are
             xselect> filter time
For example using
             xselect> filter time file good_times.xsl
allows a spectrum to be extracted using the 'good time intervals' previously defined and saved to a file. The command
             xselect> filter region
is almost always required in analysis of imaging data, to define the region for which your spectrum is being extracted. Region files can be defined using an SAOImage DS9 display of the field of interest, as detailed in Chapter 3. For example
             xselect> filter region binary_bgd.reg
will use the region file binary_bgd.reg as a spatial filter for subsequent extracted spectra.
             xselect> filter phase
allows a phase to be defined, and thus good time intervals are calculated and used as a time filter for the extracted spectrum. Similarly,
             xselect> filter intensity
allows the user to extract a spectrum over a user-defined count rate
xsel:ROSAT-PSPC > filter intensity
> Enter ranges for intensity filtering (i.e. .01-.02,1-5) >[] 10-15
Making GTI to implement intensity selection with Boolean expression:
 * RATE>=  0.1000E+02&&RATE<=  0.1500E+02

These filters can be cleared in the usual way, e.g.
             xselect> clear time good_times.xsl
Extracted spectra can be model-fit in xspec, or manipulated (e.g. to make ratios of high versus low state spectra ) using mathpha (Chapter 7).

Chapter 6
Preparing for XSPEC, XRONOS and XIMAGE

Together, xspec, xronos and ximage are known as the xanadu software. These programs allow the detailed spectral, timing and spatial analysis of your data (in FITS format). A very brief introduction follows.
The xanadu software and installation guide can be found on the anonymous ftp area of legacy.gsfc.nasa.gov under the /software/xanadu/ directory. For help finding or installing xspec, xronos or ximage software or manuals please email xanprob@athena.gsfc.nasa.gov.

6.1  Prior to XSPEC

There are just a few considerations prior to reading your FITS spectrum into xspec. If your source was observed on-axis, you may wish to use the standard on-axis response matrices which are already convolved with the on-axis mirror effective area and the PSPC gas transmission and window functions.

The ROSAT PSPC response matrices

The anonymous ftp /caldb/data/rosat/pspc/cpf/matrices/ directory tree on the legacy.gsfc.nasa.gov machine contains various response matrices (and related products) for the ROSAT PSPCs.
256 PI channel detector redistribution matrices
The following matrices are 2-dimensional arrays (energy vs channel) containing the probabilities that a photon of a given incident energy which enters the detector will give rise to an event in a given PI channel. As such they are VALID FOR ALL REGIONS of the detector, but also require an appropriately constructed Äncillary Response File" (ARF) to enable spectral analysis to be performed in xspec. (ARFs can be constructed using pcarf, as detailed above)
        - valid for PSPCB data taken BEFORE 1991 Oct 14
        - valid for PSPCB data taken AFTER 1991 Oct 14
        - valid for ALL PSPCC data (detector destroyed on 1991 Jan 25)

On-axis 256 PI channel response matrices (including the on-axis effective areas)
The following matrices are 2-dimensional arrays (energy vs channel) containing the above detector redistribution (probability) matrices BUT MULTIPLIED by the XRT effective area, window transmission etc appropriate for ON-AXIS sources.
        - valid for PSPCB data taken BEFORE 1991 Oct 14
          (formerly known as pspcb_92mar11.rmf)
        - valid for PSPCB data taken AFTER 1991 Oct 14
          (formerly known as pspcb_93jan12.rmf)
        - valid for ALL PSPCC data (detector destroyed on 1991 Jan 25)
          (formerly known as pspcc_92mar11.rmf)

Compressed, 34 channel matrices are also available in the same area, for use with the archival spectra stored in the RDF _src.fits files.

The ROSAT HRI response matrix

The HRI matrix can be found under /caldb/data/rosat/hri/cpf/hri_90dec01.rmf

6.1.1  Off-Axis Spectra

If your source was observed off-axis then you must make an ancilliary response file (ARF) for your spectrum and you should use grppha to group and set bad channel flags for the source spectral data (if you did not allow to the deafult grouping to be set when you saved the spectrum from xselect).
This program generates a Ancillary Response File (ARF) for the ROSAT PSPC instrument. The ARF consists of a simple 1-d list of the corrections required to be applied to the input detector response matrix during the spectral analysis of input PHA dataset. The ARF contains the weighted effective area, PSPC gas transmission, window and filter (where applicable) information, and is used in xspec in conjunction with the photon redistribution *only* matrix (in the past we have used matrices which held the convolved area and photon redistribution information).
** PCARF 2.0.0
Name of input PHA file[] target.sp
Name of input RMF file[/caldb/data/rosat/pspc/cpf/matrices/pspcb_gain2_256.rmf]
Name of output ARF file[target.arf]
Name of input SPECRESP or EFFAREA file[/caldb/data/rosat/pspc/cpf/pspcb_v2.

** PCARF 2.0.0   Finished

Notes & Warnings:

6.1.2  Grouping or Rebinning the Spectral Data

The raw 256 channels oversamples the PSPC spectral resolution many times so you may want to group up the FITS spectrum before analyzing it within xspec. This can be done using the grppha ftool. grppha sets a data grouping rather than actually binning the data. This means that the grouping can be changed as many times as required, while the original counts and error information remain available. In fact the data must not be rebinned using rbnpha or the resultant spectra will fail to match the dimension of the response matrices you will be using (xspec internally handles the binning of the response matrix to match the data grouping produced using grppha). xselect spawns the grppha ftool as you ßave spectrum", it offers a reasonable setting for the bad channels, and a reasonable grouping, but you may wish to set your own grouping (note even if you allow xselect to set an initial grouping, you can reset this later using the 'reset group' command in grppha, so its a good idea to use the xselect default for the first quick-look)
            grppha target.sp target_group.sp
grppha will first give you a summary of the keyword values set in your file. You may wish to change these in order to set defaults for the response matrix, ARF , background spectrum etc.
             GRPPHA (): chkey ancrfile new_target.arf
             GRPPHA (): chkey backfile target_bgd.sp
set default arf and background files for the spectral file.
Note Do not group up the background spectrum, xspec will handle the area rescaling and data grouping using the header information in both spectral files. xspec also automatically bins up the response matrix to have the same number of channels as the spectrum.
             GRPPHA (): bad 1-8, 200-256
             GRPPHA (): group 9-199 10
             GRPPHA (): exit
The target_group.sp file will now give 19 channels when read into xspec.
If ARF, RESP and BACKFILE are not set in the source spectrum file header, then one can read them in at the xspec prompt.
In the case of the HRI spectra, the energy resolution is negligable and the response matrix for the HRI is a single channel matrix, while the data have 16 raw channels. In this case one should use rbnpha to bin up the 16 raw channels into the 1 resultant channel for which the HRI response matrix is calibrated. xselect offers this as a default upon saving HRI spectra, but you can run the task standalone
             RBNPHA ():
Please enter PHA filename[agn.pha]
Please enter output filename[] agn_bin.pha
Please enter Resultant number of Channels[10] 1
Please enter Compression mode[linear]
 Main RBNPHA Ver 1.0.9
 RBNPHA ver 1.0.9 completed

6.2  Reading the Data into XSPEC

Having prepared the spectrum, and any arf file if required, invoke xspec by typing its name
               XSPEC 9.00 16:25:16 14-Mar-96

  Plot device not set, use "cpd" to set it

  Type "help" or "?" for further information
 XSPEC> data agn.pha
  Net count rate (cts/cm^2/s) for file   1  0.2669    +/-  7.7344E-03
 XSPEC> ignore bad
 XSPEC> cpd /xw

the data are read in and the plot device is set. If you put the information as to where to find the response matrix, the background spectrum and (if in use ) the arf file in the primary spectrum file header, then you are now ready to define and fit a model spectrum to the data. If you did not define these things, then you can do so within xspec
 XSPEC> resp /cpf/matrices/pspcb_gain2_256.rmf
 XSPEC> arf agn.arf
 XSPEC> back background.pha
  Net count rate (cts/cm^2/s) for file   1  0.2441    +/-  8.2032E-03
( 92.6% total)

You are now ready for model definition and spectral fitting. For more details about xspec see the xspec users guide, available from legacy under /software/xanadu/xandis/manuals/xspec_7/

6.3  Reading the events files or time series into XRONOS

xronos can read the FITS binned light curves and the photon time files written by xselect.  xronos can be used for detailed analysis of time series and photons events files, it contains routines to calulate power spectra, hardness ratios, cross correlation functions etc. The xronos tasks lc1, lc2 and lc3 are used to plot light curves in 1 to 3 bands (respectively). The user can set the number of output bins, and the data window. The tasks efs and psd allow data folding and fft calculation, while acf, acs, ccf and ccs allow auto-correlation and cross- correlation analysis and sta and tss allow a statistical analysis of the dataset.
A detailed description of xronos is beyond the scope of this guide, but further information can be found in the  xronos users guide available from legacy under /software/xanadu/xandis/timing/xronos/help/
In this simple example, a time series is read into the lc1 program, which allows binning and plotting of a light curve (which can be made up of several files) as follows:
% xronos

Welcome to Xronos         

                       Type "help" for information

[1]xronos> lc1
> Program lc1         18-OCT-1994 11:48:13         Xronos vers. 4.02 Jul 94

Enter up to  50 input filenames and options for series 1 (or rtn)
lc1> Ser. 1 filename   1 +options[.rbf]=> test.curve

Selected FITS extensions: 1 - RATE TABLE;

Source ....... NGC 0000  Start Time (d) ....   601 16:22:03.000
FITS Extension  1 - `RATE` Stop Time (d) ...   605 02:38:43.000
No. of Rows ...         18        Bin Time (s) ......    200.0
Right Ascension                   Internal time sys.. Literal
Declination .....                 Experiment ........ ROSAT    PSPC
Filter ........ none
Corrections applied: Vignetting-No ; Deadtime-No ; Bkgd-No ; Clock-No

Selected Columns: 1-Time;   2-Y-axis;  3-Y-error;

File contains binned data.

 lc1> Ser. 1 filename   2 +options[.rbf]=>
 lc1> Window Options ?          {y/n}[n]=>

   0 Time,    0 Phase,    0 Intensity,    2 Exposure Windows

 Expected Start ...  601.68197916667  (days)  16:22: 3:0  (h:m:s:ms)
 Expected Stop ....  605.11021990741  (days)   2:38:43:0  (h:m:s:ms)
 Minimum Newbin Time    200.00000      (s)
 Maximum Newbin No..             1482
 Default Newbin Time  579.194 s (to have 1 Intv. of512 Newbins)

 lc1> Enter Newbin Time (s) or neg.rebinning
      of Min. Newbin Time [   579.2    ]=>

 Newbin Time ......     579.194     (s)
 Maximum Newbin No.     512    (or 1 Intvs. of 512 Newbins)

 lc1> No. of Newbins/Intv.  (max: 65536)
      {value or neg.pow.of 2}[      512]=>

 Maximum of  1 Intvs. with  512 Newbins of 579.194 s

 lc1> Order of polynomial trend removal
 lc1> Time axis units
        {0=s from start,1=s,2=h,3=d} [3]=>
 lc1> Enter output filename
      [xronos.qlc1                     ]=>
 lc1> Plot options ?            {n/y}[n]=>

Intv 1   Start  601 16:25:12
     Ser.1 Avg  13.01  Chisq  3608. Var  12.83  Newbs. 9
     Min  8.973    Max  20.08  expVar 0.3804E-01  Bins 18
             Light curve ready !
 Frme    1  Written to output file : xronos.qlc1

 To plot  vs. Time (days), please enter
 PGPLOT file/type: /xterm

Thus a light curve was rebinned to 512 output bins, plotted in an xterm window and saved to xronos.qlc1, ready for further analysis.

6.4  Reading the events files or images in XIMAGE

The FITS image output from XSELECT can be read straight into XIMAGE using the command :
             XIMAGE> read/fits goodimage.fits
The events file requires some rebinning in order to read in the entire field-of-view
             XIMAGE> read/fits/rebin=30 events.fits
             XIMAGE> cpd /xw
             XIMAGE> disp
sets the plot device to xwindows and displays the data.
If you don't have an X device then you could use the contour option:
             XIMAGE> smooth[/sigma=3]
smooths the image with a Gaussian of sigma 3 bins. Then make a contour plot :
             XIMAGE> contour[/first=2/no_of=10]
The optional qualifers make 10 linearly-spaced contours but this does not plot the lowest contour.
             XIMAGE> contour/overlay
will overlay the contour on a previously displayed image.
There are many other useful things that ximage can do, e.g.

         slice/x - make a slice in the x direction (use the left, 
                   middle and right mouse buttons to select, erase 
                   and choose a y region to do the slice accumulation)

background/box=n - measure the background in a box of size n pixels

          detect - source detection (use /back=n, to vary the background 
                   box size)
             cct - change the color table

          circle - defines a circular region (can write to file)

            grid - draw a coordinate grid

ra_dec_to_pixel  - mark the image and return pixel for given RA and DEC

         psf/cur - measure the point spread function

        saoimage - spawn \texttt{SAOImage Ds9} to display the image

      write/fits - write the current image as a FITS file

Notes & Warnings:
For further information regarding XIMAGE please see the XIMAGE users guide, available from legacy.gsfc.nasa.gov anonymous ftp account under /software/xanadu/xandis/image/ximage/doc/

Chapter 7
More Advanced Analysis

7.1  Screening/Rescreening the Data

xselect includes a facility to select times based on the values of some auxiliary quantities ie those not associated with each event. Examples could be angle between the pointing direction and the Earth's limb, some housekeeping parameter, or the total counting rate. This information must reside in a FITS file whose first extension is a BINTABLE with time column called TIME. For ROSAT, the housekeeping information is stored in the seq_anc.fits (the ancilliary file), the seq_anc.fits file does not, however, store all the information in the most useful way for xselect screening and users need to run PCFILT for PSPC data, or HRIFILT for HRI data.
Using PCFILT as an example (HRIFILT is very similar):
The FTOOL PCFILT can be run prior to starting an xselect session (or spawned from within xselect). PCFILT will resample the housekeeping data and calculate many useful parameters from the raw information contained in seq_anc.fits, making the ROSAT equivalent of the ASCA makefilter file.
The output (makefilter) file should have a .rmkf extension for xselect to pick it up automatically when it is required.
        Please enter Ancillary filename[] rp700111_anc.fits
        Please enter output filename[] rp700111.rmkf
        Main PCFILT Ver 1.0.0
        PCFILT ver 1.0.0 completed

The data is actually filtered within xselect as follows
             xselect> select mkf
> Boolean expression for filter file selection > []
at this prompt give a selection expression. This expression can be in either Fortran or C syntax. For instance, if you wanted all times when OBI_NUM exceeded 1 then the expression would be "OBI_NUM .gt. 1". xselect will then calculate and store all time ranges for which this is true. These time ranges will be used for any extractions performed by xselect.
After running ßelect mkf", a ßhow status" command will show the filter; any data product extracted while this is in place will be filtered accordingly.
The makefilter file can be used to screen down the ßtandard events", ie those already screened by SASS, or to rescreen the total set of events. In the latter case, you first need to make a file of the total events, by summing the SASS selected events, and the rejected events, and generating a set of good time intervals which are applicable to this total dataset.
If you wish to bypass the SASS data screening, and do your own screening from the master set of events, you can do this for an RDF dataset by combining the rejected and good events, and calculating the full set of time intervals associated with these data
mk_allevt 0.2.0:  Type 'mk_allevt -h' for instructions.
File: "" is illegal for output
You have the following likely looking file groups:
1       rh110267n00
2       rh701446n00
3       rh701447n00
4       rp110590n00
5       rp110231n00
Type corresponding number to select a set of files.
Or type a specific file or pathname.
Output (abas) Filename: 5

will combine the RDF rejected and good events into a single events extension in a new file (by default this will be named rp110231n00_abas.fits in this example). This new file can be analyzed in xselect as normal.

7.1.1  Saving screened events

If you have screened your events file, then you may wish to save the screened events for later analysis, first you must extract the events under all desired filters
             xselect> extract events
             xselect> save events good.events
After the second command you will be asked whether you want to read this data back in. If you answer yes then xselect uses the file which you just created rather than the original data files.

7.2  Exposure Correcting an image - pcexpmap and hriexpmap

Creates an exposure map for user specified time period and energy range for any US Rev0 or RDF format ROSAT datasets
EXAMPLE - To exposure correct a PSPC image:
To use pcexpmap the detector maps created from the ROSAT All-Sky Survey data are required. These may be obtained from the /caldb/data/rosat/pspc/cpf/detmaps/ directory on legacy.gsfc.nasa.gov. The detector maps are available in a number of energy bands, and the filenames contain the PI channel ranges used, where channel 11 is ~ 0.11 keV, channel 200 is ~ 2 keV etc. The detector maps currently available have the following rootnames (one map each for PSPCB and PSPCC):

The output from pcexpmap is a 512x512 FITS image of the whole PSPC field of view (with pixels 14.94733 arcsec per side; representing a blocking factor of 16 over the raw [0.9341875 arcsec] pixelsize) of the effective exposure time (in seconds) at that position. The effects of vignetting (for a spectrum equal to the mean spectrum of the X-ray background in the PSPC band) and spatial variations in the efficiency of the detector are included (via the detector maps), along with detector deadtime effects (applied by pcexpmap).
The program follows the suggestions of Snowden et al. (1992, ApJ, 393 819) and Plucinsky et al. (1993, ApJ, 418, 519) to exclude regions of the PSPC near the edges of the PSPC which are strongly affected by the particle background, the "bright line" regions. These regions are set to have zero exposure time.
In brief, the attitude and GTI files are used to construct a matrix of the time the instrument spent at each pointing position (X,Y relative to the nominal pointing position defined by the optical axis) and roll angle. (The X,Y are in units of 14.94733 arcsec for historical reasons, the ROLL steps are in units of 0.2076 degrees.) The event-rates file is then used to calculate the live-time fraction at each of these positions. Finally the output exposure map is constructed by moving the detector map to each off-axis position, rotated to each roll angle, and adding the detector map with the appropriate weighting factor to the exposure map under construction.
In the following example, the user removes afterpulse events, creates and image and exposure map, and corrects the image using  farith.
        Name of FITS file and [ext][] rp100000n00_bas.fits[2]
        Name of output FITS file[burst.out]
        Maximum time between events in seconds[0.003]
        Whether to keep first event in burst[yes]

Within xselect, extract an image
             xselect> set xybinsize 30
to match the resolution of the detector maps
             xselect> extract image phalcut=52 phahcut=90
extract our image in the ~ 0.52 - 0.9 keV band
             xselect> save image image_52_90.fits
        Enter Event rate filename[]rp100000n00_anc.fits 
        Enter Attitude filename[] rp100000n00_anc.fits
        Enter GTI filename[] rp100000n00_bas.fits
        Enter Detector map file[] det_52_90_b.fits
        Enter output filename[] expmap_52_90.fits
        Enter Instrument/Detector name[PSPCB]
         MAIN : PCEXPMAP Ver 2.0.1
         ... Number of unique detector positions         378
         ... Number of entries when Detector ON         9634
         ... Number of entries when Detector OFF           0 (A1LL c/rate<10)
         ... Total ONTIME        9634.00000 s
         ... Total LIVETIME      9314.57227 s
         ... Average MV c/rate    111.51972 count/s
         PCEXPMAP Ver 2.0.1 completed

       Name of Ist FITS file and [ext#][] image_52_90.fits
       Name of 2nd FITS file and [ext#][]expmap_52_90.fits 
       Name of OUTFIL FITS file[] corrected_52_90.fits
       Name of operation[Enter Operation ADD,SUB,DIV,MUL(or +,-,/,*)]/

Please see the online help files for pcexpmap and hriexpmap for more details.
Notes & Warnings:

7.3  Comparing the radial profile data to the psf

First the radil profile should be extracted from the events file using extrpsf

7.3.1  extrpsf

This caltools package task extracts a Radial Point-Spread Function (RPSF) dataset from an event file. An RPSF dataset consists of the number of counts per unit area as a function of radius (using series of concentric annulus). This is calculated using the X & Y (ie RA & dec) columns in the event file centered on a point defined by the user (in either RA & dec or pixel coordinates) for a user-defined number of annuli and outer-radius. If desired, the user can also specify the radius (within the outer radius) beyond which will be used to estimate the number of counts per unit area corresponding to the background. The user can also specify any of several prescriptions to be used to calculate the statistical errors associated with the RPSF data. The output psf file is FITS format, and can be directly compared to the theoretical psf model for the hri or pspc data as described below.
Notes & Warnings:
Then the data should be compared to the model, using the script calcrpsf

7.3.2  calcrpsf

This routine is a multi-task wrapper for Radial Point Spread Function (RPSF) which allows several common steps to be performed by a single script. This task interfaces with radial profiles produced using either extrpsf or pros (after conversion of the pros files to FITS format via STWFITS and ST2RPSF).
calcrpsf spawns:
The user is prompted as to which of these tasks are desired, the ftool rpsf2eef is also available, which converts a radial PSF (RPSF) dataset to a radial encircled energy function (REEF) dataset. The REEF file can be converted to qdp using rpsfqdp, in the same way the RPSF file can.
        ** CALCRPSF 1.3.0
        Input filename[temp] radial_profile.fits
        Output filename[calcrpsf.out]
        Run st2rspf ?[no]
        Run rbnrpsf ?[yes]
        Generate a theoretical RPSF dataset ?[no] yes
        Run rpsfqdp ?[no] yes
        Please enter Telescope name[ROSAT]
        Please enter Instrument name[PSPCB]
        Please enter Minimum PI channel for image[] 12
        Please enter Maximum PI channel for image[] 200
        Please enter background count rate (ct/pixel)[] 5e-4
Please enter PHA filename :[] NONE
Please enter Off Axis histogram filename :[%] NONE
Please enter RMF filename :[/caldb/data/rosat/pspc/cpf/matrices/pspcb_gain2_256.
Please enter off_axis angle (arcmin) :[0.5]
 ** pcrpsf 3.0.1
 ** pcrpsf 3.0.1 completed successfully

 *** spawning RPSFQDP to convert RPSF dataset to QDP:
rpsfqdp chatter=5 datafile="rpsfpred.tmp" outfile=xxx.calcrpsf
 ** rpsfqdp 3.0.1
 ** rpsfqdp 3.0.1 completed successfully

** CALCRPSF 1.3.1   Finished

The resulting file can now be plotted with QDP (if you skip rpsfqdp then the resulting file can be plotted using fplot).
Notes & Warnings:

7.4  Performing mathematical operations on PHA files

The ftool  mathpha can be used to perform mathematical operations on PHA files. The calculation can optionally be carried out units of COUNTS or RATE, the user is advised to carefully read the help which is available before using this task.
        ** MATHPHA 3.0.3
        Expression to be evaluated[] spectrum1.pha / spectrum2.pha
        Units algebraic expression to be performed in (C,R,F or ?)[C] ?

        ... This parameter indicates the physical units in 
        which the algebraic expression is to be evaluated, 
        and the units in which the output file will be written. 
        The allowed values are C (ie COUNTS), or R (ie RATE), 
        implying that the algebra will be performed in COUNTS 
        or COUNTS PER SECOND space respectively. The algebra 
        will be in this space irrespective of whether the input 
        files contain data stored in counts or in counts per 
        second (ie, if units=C, input PHA histograms stored in 
        counts per sec will be converted to counts prior to any 
        mathematical operations being performed). Similarly, this 
        flag gives the implied units of any numerical constants
        within the input expression. A third option value is also 
        allowed, units=F (ie FILE) whereby the algebra is performed 
        in which ever units most of the files are stored in (COUNTS 
        in the event of a tie).

        Units algebraic expression to be performed in (C,R,F or ?)[?] C
        O/p PHA filename[] spectral.ratio
        Exposure time flag/value ({value},{file},CALC,NULL or ?)[] ?

          This parameter controls the value written as the exposure time in the
          output file. The allowed values are:

             {a numerical value}
        - where the entered value (assuming it can be parsed as a real), is
        written to the output dataset. The value will be assumed to be in
        units of seconds. At the current time, numerals of the form  1E04
        or 1E-04 are NOT supported.
    {an input filename}
        - whereby the exposure time read from the specified input file is
        written to the output dataset
        - where the exposure time is calculated from the input expression
        by substituting each filename with its exposure time, and performing
        the specified calculation.
        - where an exposure of 1 second is written to the output dataset

        Exposure time flag/value ({value},{file},CALC,NULL or ?)[] NULL
        Number of comment strings to be added (up to 4)[1]
        Comment 1[] This is a ratio of spectrum1.pha/spectrum2.pha
        ...... processing file: spectrum1.pha
        ...... processing file: spectrum2.pha
        ... performing algebra in units of COUNTS
        ** FILOP 2.0.0   WARNING:
        ... Poissonian errors with N<20 assumed  for:
        ...... channels     1.-    7.
        ...... channels   201.-  201.
        ...... channels   205.-  208.
        ...... channels   210.-  213.
        ...... channels   216.-  256.
        ** FILOP 2.0.0   WARNING:
        ... Divide-by-zero encountered for:
        ...... channels     1.-    7.
        ...... channels   252.-  252.
        ...... channels   256.-  208.
        ... These channels have been set bad, and  value DIVZERO inserted
        ... written the PHA data Extension
        ** MATHPHA 3.0.3   Finished

This made a ratio of two spectra, the user can plot the output file using FPLOT (use FSTRUCT and FLCOL to examine the file first, so you know what column names to give to FPLOT).

7.5  Creating particle background spectra

Particle background spectra are required for use in background subtraction of extended sources, or in any case where the background must be estimated using a significantly different part of the PSPC detector than the region where the source data were taken. The sky X-rays have a different radial dependance than the particle background, so simply correcting the background spectrum for the different vignetting effect is inadequate
pcparpha generates a 256-channel PHA spectrum of the particle background in the ROSAT PSPC from the parameterization of Plucinsky etal (1993 ApJ 418, 519)
        ** PCPARPHA 2.0.1
        O/p PHA filename[particle_spectrum.pha]
        EVR filename[rp100000.evr]              
        GTI filename[rp100000.fits]                        (the events file)
        WMAP/Off-axis histogram filename[target.pha]
        No. pixels in source region (or '%' or '?')[%] ?
         ... This parameter is the number of pixels for which the
             particle background spectrum is to be calculated.
             This information should also be in the Off-axis histogram
             dataset. Enter "%" to use the stored values or enter
             an integer to override the stored values. In the
             latter case, you will be prompted for the pixel size next.
        No. pixels in source region (or '%' or '?')[?] %
        .... No. theta bins to process:           20
        ... No. EVR events to process:          323
                                         theta      weight (%)
        ...... finished theta bin   1 (1.5000    ,  0.000000)
        ... written the PHA data Extension
        ** PCPARPHA 2.0.1   Finished

Chapter 8
Quick Summary

8.1  Useful xselect commands

      clear - Clear input files, filters, selections, or everything
        cpd - Equivalent to set device
       exit - Exit from xselect
    extract - Extract image, spectrum or (light) curve from data
       help - Obtain help on commands and syntax
     filter - Set filters to be applied to the next extraction
       plot - Plot spectrum, light curve, image, HK parameter(mkf), or other
       quit - Exit from xselect
read events - Read in the events data
       save - Save current session, product FITS file, spectrum, light 
              curve, image
 select mkf - Apply Boolean expressions for data selection, for creating 
              GTI intervals from HK or filter files, and for filtering the
              observation catalogue.
        set - Sets the mission, instrument and plot device, and the
              column names, and binsizes for extract.
       show - Show data files, obscat, parameters, selections, or status
       stop - Exit from xselect

8.2  ROSAT ftools

        abc - Apply Barycentric Corrections to ROSAT event data.
        bct - Produce a Barycenter Correction Table from ROSAT orbit data
     extpha - [P] Extracts source spectrum files from PSPC _src files
 fixrev0pha - Changes  the  CDELT1 and CDELT2 keywords in a ROSAT PHA file
   gevt2rdf - Converts a German _events dataset to RDF _bas format
     hiback - [P] Creates _qsrc file from _src file
  hriaspcor - Use Morse's method to correct  aspect errors
  hriexpmap - Creates exposure map for given ROSAT HRI observational dataset
    hrifilt - Creates a ROSAT HRI makefilter file
    hrirpsf - Calculates theoretical HRI PSF
     img2us - Converts from German Image file format to US RFITS format
     mkqsrc - Adds extra fields for quality screening to ROSAT source file
  mk_allevt - [P] Combines standard \& rejected events tables of an RDF file
      pcarf - Generates a ROSAT PSPC ARF for an input PHA file
     pcecor - Corrects PI channel in Events file
   pcexpmap - Creates exposure map for ROSAT PSPC observation
     pcfilt - Creates a ROSAT PSPC makefilter file
   pcparpha - Generates a background PHA  spectrum  for ROSAT PSPC
    pcpicor - [P] Corrects PI channel in Events file
  pcsasscor - Corrects PI channel in PSPC events file
     pcrpsf - Calculates a theoretical radial PSF for the ROSAT PSPC
     pctcor - Corrects PI channel in Events file
     pcecor - Applies energy dependant correction to PI channel in Events file
    rosbary - [P] Perform barycentric correction for ROSAT. (Runs abc \& bct)
    src2pha - Creates a PHA file from specified extensions in an RDF src file

        [P] Perl script.  You must have Perl installed to use this tool.

8.3  Other FTOOLS for ROSAT Analysis

Some FTOOLs used in ROSAT analysis are applicable to data from other missions, and so reside in a more general FTOOLS package:
     calcrpsf - Calculates a radial point spread function
    caldbinfo - Checks whether a local  CALDB  is  correctly  installed
                for a user
      rbnrpsf - Rebins a radial point spread function
     rpsf2eef - Converts  a  radial  PSF  (RPSF)  dataset  to  a  radial
                encircled energy function (REEF) dataset.
      rpsfqdp - Converts OGIP format radial profile file to ASCII QDP
      st2rpsf - Reads STWFITS file and writes an OGIP RPSF file
      stw2pha - Converts stw PHA file to OGIP FITS format
          bkg - Subtract a background from a binned light curve
      extrpsf - ExtractS radial PSF (RPSF) dataset from an event file.
       grppha - Manipulates OGIP standard PHA FITS file
      mathpha - Performs mathematical operations on PHA files
       rbnpha - Compresses  a  PHA dataset
        burst - Remove bursts of events from time ordered event list
       farith - Perform arithmetic on 2 FITS images
        fdump - Dump contents of a FITS table to an ASCII file
        fhelp - Display help pages for an FTOOL task
    fkeyprint - Display keyword(s) in FITS header(s)
        flcol - List column information in a FITS table extension
        fplot - Plot columns in a FITS file using QDP/PLT package
   fstatistic - Calculate mean, standard deviation, min, and max for a column
      fstruct - List a description of the structure of a FITS file
        plist - List parameters from task parameter files
         pset - Set one or more parameters in task parameter file
     punlearn - Get a copy of the system parameter file (reset task pars)
       sky2xy - Transform from sky to pixel coordinates using WCS keywords
       xy2sky - Transform from pixel to sky coordinates using WCS keywords

Chapter 9
An Example Xselect Session

comments in italics

            ** xselect V1.1a **
            > Enter session name >[xsel] session1
session1:ASCA > read events
> Enter the Event file dir >[./]
> Enter Event file list >[] rp700000.fits            
Got new mission: ROSAT and new instrument: PSPC
> Reset the mission and instrument? >[yes]
 This is ROSAT

 Notes: xselect set up for      ROSAT
 Keywords for time and pha are  TIME       PI
 Units of time are              s
 Keywords for images are          X          Y

Setting: IMAGE binning    =   15
         WMAP binning     =   15
         Energy Column    =  PI
         Energy rebinning =    1
         WMAP keywords = DX         DY

Getting Min and Max for Energy Column...
Got min and max for PI:     0    255

Number of files read in:   1

******************** Observation Catalogue ********************

Data Directory is: /disk/user/agn/
HK Directory is: /disk/user/agn/

      1 PSPC     07/11/93 .218E+03 .623E+02 US700000 .952E+04

session1:ROSAT-PSPC > extract image
  Extractor 1.0q
 XPI 2.1t
 Doing file: /disk/user/agn/rp700000.fits
 Getting FITS WCS Keywords

100% completed
    Total      Good    Bad: Region      Time     Phase       PHA
   124810    123847              0         0         0       963
   Grand Total      Good   Bad:  Region      Time     Phase       PHA
        124810    123847              0         0         0       963
 Total Counts for image :   123847
 Total Time for image :     9625.0000000000
 Total Counts/Time for image :     12.867220779221
session1:ROSAT-PSPC > saoimage

define regions and save to a file, as detailed in section 3.1.2

session1:ROSAT-PSPC > filter region target.reg
session1:ROSAT-PSPC > set binsize 200             
session1:ROSAT-PSPC > extract curve exp=0.1   

(200 s time bins set)
(minimum partial bin 20s)
 Extractor 1.0q
 XPI 2.1t
 Doing file: /disk/user/agn/rp700000.fits
100% completed
    Total      Good    Bad: Region      Time     Phase       PHA
   124810    123847              0         0         0       963
   Grand Total      Good   Bad:  Region      Time     Phase       PHA
        124810    123847              0         0         0       963
 Total Counts for Fits Light Curve :   123847
 Total Time for Fits Light Curve :     9625.0000000000
 Total Counts/Time for Fits Light Curve :     12.867220779221
session1:ROSAT-PSPC > plot curve

Note: cursor timing selection is now done with the command

(the light curve has a few bad points which i wish to exclude)
session1:ROSAT-PSPC > filter time cursor
  - click to include a time region
c - to cancel cursor selection
e - makes the selection excluded
l - puts cursor on the left
r - puts cursor on the right
x - to exit cursor selection
p - to return to PLT prompt
  - click outside the plot to cancel a selection

Enter QUIT at PLT prompt to continue

(2 clicks define a time for inclusion and these are written to session1_cursor_gti001.xsl save these times to a file so you can use them again in a future session)
session1:ROSAT-PSPC > save time cursor
> Give output file name >[] good.times

session1:ROSAT-PSPC > extract spectrum
 Extractor 1.0q
 XPI 2.1t
 Doing file: /disk/user/agn/rp700000.fits
 Getting FITS WCS Keywords

100% completed
    Total      Good    Bad: Region      Time     Phase       PHA
   124810     17847              0    106781         0       182
   Grand Total      Good   Bad:  Region      Time     Phase       PHA
        124810     17847              0    106781         0       182
 Total Counts for spectrum :   17847
 Total Time for spectrum :     1401.5493164062
 Total Counts/Time for spectrum :     12.733765263260
session1:ROSAT-PSPC > save spectrum
> Give output file name >[high_state]
The data will be grouped using the following:

Bad 1-11, 212-256&group 12-211 10&show group&show quality&exit

> Group ( or rebin ) the spectra before outputting? >[yes]

(if the spectrum you are saving is a background spectrum then do not group the data)
 Channel Grouping (Channel-Channel) :
    1 -  11  are single channels
   12 - 211  are grouped by a factor   10

 Bad Channels (Channel - Channel)
    1 -  11  have quality 5
  212 - 256  have quality 5

Wrote spectrum to high_state.pha

session1:ROSAT-PSPC > exit
Do you wish to save this session?> no


1SAOImage DS9 development has been made possible by funding from the Chandra X-ray Science Center (NAS8-03060) and the High Energy Astrophysics Science Archive Center (NCC5-568).

File translated from TEX by TTH, version 3.85.
On 15 Feb 2011, 14:05.