Phase resolved spectral fitting

How to perform spectral fitting on data from a given phase range of an orbital period.

1. Use a sorting routine to create a 2-d, time x PH_channel binned dataset. e.g. XSORT.

2. Exposure correct the file to convert it into counts/second e.g. for the XRT.

     ICL> XRTCORR
     XRTCORR version 1.4-6
     INP - Input dataset name /@MID_SPEC/ > TIMPH
     OUT - Output dataset name /@TIMPHC/ >
     RTNAME - Rootname for calibration files /'[HIS.2142]X2142'/ >
     Warning: insufficient event rate data to calculate dead time correction
              for 19 timebins
     Correction for these bins has been set to 1.0
     Warning: bad eventrate data for 9 timebins
     Correction for these bins has been set to 1.0
     Mean dead time correction : 1.001657
     Mean vignetting correction : 58.66176
     Mean scattering correction : 1.007486
   

3. Fold the data at the known orbital period.

     ICL> FOLDBIN
     FOLDBIN Version 1.2-2
     INP - Enter name of input file /@TIMPHC/ >
     Data is 2 dimensional
     OUT - Enter name of output file > TIMPHCFOLD
     TIME UNITS are seconds
     PERIOD - Enter period for folding > 4128.1
     EPOCH - Enter epoch of phase zero /6775.0817013889/ > 6774.002
     BINS - Enter number of phase bins /8/ > 5
     WEIGHT - Are weighted means required? /NO/ >
     ** VARB is zero - CHISQ may not be correct in output file **
   

4. Having converted the time axis into 5 phase bins, we now want to extract the central 20 % of the orbit.

     ICL> BINSUBSET
     BINSUBSET Version 1.2-0
     INP - Input dataset /@TIMPHC/ > TIMPHCFOLD
     OUT - Output dataset > MIDSPEC
     The axes present are:
      1 Phase
      2 Corrected PHA channel
     AXES - Axis numbers to select on > 1
     The range for axis 1 is 0.1 to 0.9
     AXIS1 - Axis 1 ranges to subset /'0.1:0.9'/ > 0.4:0.6
   

5. We now have a single spectrum to perform spectral fitting on. Create a detector response structure for this datafile. e.g. for the ROSAT-XRT use XRTRESP.

     ICL> XRTRESP
     XRTRESP Version 1.3-4
     INP - Name of source file /@MIDSPEC/ >
     RESPFILE - Name of instrument response matrix file /@X2142_DRPM/ >
   

6. Set up a model for the spectral fit

     ICL> SMODEL
     SMODEL Version 1.0-1
     Input model file :- DISK$SCRATCH:[ASTERIX88]MOD.SDF;1
    
     A composite model can be synthesised using + - * ( ) and
     any of the following primitive models:
    
     AG     galactic interstellar absorption             multiplicative
     AB     intrinsic absorption                         multiplicative
     BR     thermal bremsstrahlung (cosmic)              additive
     PL     power law                                    additive
     BB     black body                                   additive
     WN     Wien                                         additive
     BH     hydrogen bremsstrahlung                      additive
     BP     pseudo-bremsstrahlung                        additive
     PC     cutoff power law                             additive
     CS     Chapline-Stevens Comptonised brems.          additive
     ST     Sunyaev-Titarchuk Comptonisation             additive
     RZ     Raymond-Smith plasma (metals combined)       additive
     LG     Gaussian line                                additive
     LL     Lorentzian line                              additive
    
    SPEC - Model specification > BR*AG
    
                         COMPONENT  1
                        **************
   Name: thermal bremsstrahlung (cosmic)          Keyword: BR
    PARAMETER  1 - em10                       (1e60cm**-3/(10kpc)**2)
                   value,min,max =   1.0000       1.00000E-04    10.000
   VALS - New values /'unchanged'/ >
    PARAMETER  2 - temperature                (keV)
                   value,min,max =   5.0000       0.10000        20.000
   VALS - New values /'unchanged'/ >
    
                         COMPONENT  2
                        **************
   Name: galactic interstellar absorption         Keyword: AG
    PARAMETER  1 - hydrogen column density    (1.0E21 /cm**2)
                   value,min,max =   1.0000       0.00000E+00    20.000
   VALS - New values /'unchanged'/ > 0.28
   

   g) Freeze the hydrogen column density and perform the fit.

     ICL> FREEZE 3
          * hydrogen column density frozen
    
     ICL> SFIT
     SFIT Version 1.4-1
     ...
   

7. Having finished processing the data - review the history of the final file.

     ICL> hist midspec
     HIST Version 1.8-1
    
     History of  : /datan5/asterix/midspec.sdf
                   SPEC
     Created     : 9-AUG-91 14:25:16
     Update mode : NORMAL
     Contains    : 5 records
    
     Record 1:
    
       Creator: XSORT Version 1.3-5
       Date:    9-AUG-91 14:25:17
    
     Record 2:
    
       Creator: XRTCORR version 1.4-6
       Date:    9-AUG-91 15:31:44
       Text:    Input dataset  1:
                   DISK$SCRATCH:[ASTERIX88]TIMPH.SDF;1
    
     Record 3:
    
       Creator: FOLDBIN Version 1.2-2
       Date:    9-AUG-91 15:36:49
       Text:    Input file :
                   DISK$SCRATCH:[ASTERIX88]TIMPHC.SDF;3
                Folded output file :
                   DISK$SCRATCH:[ASTERIX88]TIMPHCFOLD.SDF;2
                The data has been folded into a period of 4128.1 seconds
                The epoch of phase zero was 6774.002
    
     Record 4:
    
       Creator: BINSUBSET Version 1.2-0
       Date:    9-AUG-91 15:39:14
       Text:    Input dataset  1:
                  DISK$SCRATCH:[ASTERIX88]TIMPHCFOLD.SDF;2
    
     Record 5:
    
       Creator: XRTRESP Version 1.3-4
       Date:    9-AUG-91 15:42:23
       Text:    Set up detector response structure in datafile