View source for Nustar

====== NuSTAR data extraction ======

'''Preparation:''' This step unpacks the data of both FPM to the specified 'prepdir'. The example observation is of Mrk 335.

<pre>
#!/bin/csh
   
set revolution = '6'
set obsid = '60001041005'
set datadir = /data/X-ray/NuSTAR/data/$revolution/$obsid
set prepdir = /userdata/data/$user/whereever/you/want

nuprepare --datadir=$datadir --prepdir=$prepdir --all
</pre>

'''Spectrum and Lightcurve Extraction:'''
Now you can take a look at the raw images in prepdir/reprocessed/nu-obsid-A-or-B-01_cl.evt using ''ds9''. Create a region by clicking at the source and choose a circular region between 50 and 120<nowiki>''</nowiki> radius centered on the source. You can save the coordinates under Region->Save Regions... as .reg-file use the default coordinate system.<br />
Choose and save another region for the background spectrum that does not contain any sources and make it as large as possible. Be careful that it is still within NuSTAR's FOV.<br />
Now we can extract the spectrum using nuextract:

<pre>

#!/bin/csh
   
set revolution = '6'
set obsid = '60001041005'
set prepdir = /userdata/data/$user/whereever/you/want

set name = extraction_a
set bkg = $prepdir/reprocessed/fpma_bkg.reg
set src = $prepdir/reprocessed/fpma_src.reg

nuextract --prepdir=$prepdir --name=$name --srcreg=$src --bkgreg=$bkg --fpm='A'

set name = extraction_b
set bkg = $prepdir/reprocessed/fpmb_bkg.reg
set src = $prepdir/reprocessed/fpmb_src.reg

nuextract --prepdir=$prepdir --name=$name --srcreg=$src --bkgreg=$bkg --fpm='B'

</pre>

For time- or energy-limited extractions take a look at:
 nuextract --help

===== Version information =====

In order to find out the version of the NuSTARDAS and CALDB your data were extracted with, you can use the following commands:

  fdump <fits_file_of_interest> page=no | grep -i nustardas
  fdump <fits_file_of_interest> page=no | grep -i caldb


===== Known Issues =====

* Very long file and directory names can cause crashes in nuextract. The path $name has to be a relative path, otherwise nuextract crashes.
* When using a GTI file during extractions, be careful if a keyword not found error occurs. fkeypar adds a keyword to the first extension per default. If you need the keyword in the primary header, this has to be explicitly set when calling fkeypar.

===== Bright sources =====

* For sources with count-rates exceeding ~100 counts per second it is advised to use the the additional nuprepare flag --statusexpr="(STATUS==b0000xxx00xxxx000)&&(SHIELD==0)". 
* If you dont do this you might find a large (up to 30%) off-set in the normalization between the FPMs. 
* For timing analysis of the power spectrum the SHIELD==0 term should be removed as this does introduce energy dependent timing features. 
* Check the NuSTAR FAQ on bright sources for more information: https://heasarc.gsfc.nasa.gov/docs/nustar/nustar_faq.html#bright. 




[[Category:Data Extraction]]