PKS0745-19 seq=00051650001

The outputs of the SDC pipeline consists of the Level 1 data and does not include currently the clean event files. The screening criteria are currently being worked out by the instrument team to optimize the outputs. Here are described the steps to create the clean event files and extract spectra for sources in the field.

• Make sure you have the latest XRT CALDB version installed
• Create a directory for the outputs

     mkdir pks074519
  

• Run xrtpipeline using the following command

   
  xrtpipeline  gtiexpr="SAA==0&&Vod1>=29.8&&Vod1<=30.25&&Vod2>=29.30&&Vod2<=29.80&&
   Vrd1>=16.40&&Vrd1<=16.80&&Vrd2>=16.45&&Vrd2<=16.90&&Vsub>=-0.1&&Vsub<=0.1&&  
   Vbackjun>=-0.1&&Vbackjun<=0.1&&BaseLin1>=0.1&&BaseLin1<=0.4&&BaseLin2>=-0.1&&
   BaseLin2<=0.1"
  

  You will be prompted for :
  • - the RA and DEC (enter POINT which is the default)
  • - the directory path where the data downloaded from the SDC are located in your disk
  • - the stem of the input FITS file
  • - output directory
  This is shown below.

  ===========================================================
                  Running SWIFT XRT pipeline
   Task: xrtpipeline Version: 0.7.5 Release Date: 2004-12-17
  ============================================================
  Source RA position (POINT to use optical axis direction) (degrees or hh mm ss.s) [POINT] : 
  Source DEC position (POINT to use optical axis direction) (degrees or dd mm ss.s) [POINT] : 
  Target Archive Directory Path [00100585001] : 00051650001
  Stem for FITS input files [i.e. sw00000000000] [st00100585001] : sw00051650001
  Directory for outputs [GRB041223] : pks074519
  

• In the output directory you will find several files. The observation was done using the XRT in PC mode. The clean event file list during the pointing part of the observation is name with sw{root}po_cl.evt where root contains the sequence number and the XRT mode
• Use XSELECT to create an image and plot the image. The field actually includes 2 identified stars in Simbad as shown in figure.
  
  
• With the image display up create a source and background region for PKS0745-19. Use a radius of 45 arcsec for source and background region.
• Set the region filter in XSELECT and extract and save the spectrum
• To increase the signal use group the spectrum using the FTOOL "groppha"
• Take from CALDB the appropriate response matrix, e.g. swxpc0to12_20010101v006.rmf
• Calculate an arf using the tool "xrtmkarf"
• With rmf, arf, source and background files start-up XSPEC for the spectral analysis The spectrum as shown in figure is well described by the following model.
  
  The exposure is very short 2639.6 sec and the iron line is not required in the fitting

  Model:  ( powerlaw<1> + mekal<2> )wabs<3>
  Model Fit Model Component  Parameter  Unit     Value
  par   par comp
  1    1    1   powerlaw   PhoIndex            1.96488     +/-  0.263203
  2    2    1   powerlaw   norm               7.581451E-03 +/-  0.186366E-02
  3    4    2   mekal      kT       keV        6.79744     +/-   2.15519
  4    5    2   mekal      nH       cm-3       1.00000     frozen
  5    6    2   mekal      Abundanc            1.00000     frozen
  6    7    2   mekal      Redshift           0.102800     frozen
  7    8    2   mekal      Switch              1.00000     frozen
  8    9    2   mekal      norm               1.989246E-02 +/-  0.639439E-02
  9    3    3   wabs       nH       10^22     0.501647     +/-  0.454076E-01
  
  ---------------------------------------------------------------------------
  
  ---------------------------------------------------------------------------
   Chi-Squared =      153.1687     using   117 PHA bins.
   Reduced chi-squared =      1.367578     for    112 degrees of freedom
   Null hypothesis probability = 5.955E-03
  

• Following the same procedure for the two Simbad sources. The CCDM star is a multiple star system, and the other is a pulsating variable. The CCDM has X-ray emission
  

  but the variable star is very piled-up within these data and it appears that the emission is all optical light.