Extract Coadded and Grouped Nth-Order Source & Background Spectra and ARFs

[CIAO 3.4 Science Threads]

Overview

Last Update: 1 Dec 2006 - reviewed for CIAO 3.4: no changes

Synopsis:

add_grating_orders is a script which lets the user add up positive and negative diffraction orders of a given grating spectrum, and their associated ARFs. The output spectrum can be grouped if desired.

Purpose:

To generate and group a coadded positive and negative order grating spectrum (for both source and background) and the associated ARF.

Read this thread if:

you are working with ACIS/HETG, ACIS/LETG, or HRC/LETG observational data and would like to add the grating orders.

Related Links:

Analysis Guide for Chandra High Resolution Spectroscopy: an in-depth discussion of grating analysis.

Proceed to the HTML or hardcopy (PDF: A4 | letter) version of the thread.

Get Started
Downloading add_grating_orders
Run add_grating_orders
Summary
Parameter files:
- add_grating_orders
History

Get Started

Sample ObsID used: 459 (HETG/ACIS-S, 3C 273)

File types needed: pha2

This thread assumes that you have created positive and negative grating ARFs for your dataset. This process is illustrated in the threads for building ACIS/HETG, ACIS/LETG, HRC-S/LETG, or HRC-I/LETG ARFs.

The data to be combined must have been taken with the same instrumental configuration:

ACIS-HETG-HEG
ACIS-HETG-MEG
ACIS-LETG-LEG
HRC-LETG-LEG

Downloading add_grating_orders

The most recent version of add_grating_orders is 2.2 (22 May 2001):

unix% grep version_ `which add_grating_orders`
version_str="2.2"
version_date="22 May 2001"

Please check that you are using the most recent version before continuing. If you do not have the script installed or need to update to a newer version, please refer to the Scripts page.

Run add_grating_orders

The script executes the following tools in order:

dmtype2split: to split the PHA2 spectrum into two temporary positive and negative order spectra with PHA1-like format.
dmtcalc: to rename columns in the two temporary PHA1 files, and to build two temporary single-order ARFs with renamed columns.
dmpaste: to merge the two temporary PHA1 spectra and ARFs. gspec
dmtcalc: to add together positive and negative spectra and ARFs.
dmcopy: to build a final coadded spectrum (with a PHA1-like format) and a coadded ARF.
dmgroup: to group the coadded positive and negative order spectrum (if needed).

In this example, we build coadded 1st-order source and background MEG spectra and a 1st-order ARF. Then the source spectrum is grouped by a factor of 10 (to learn more about the several options for gtype, see ahelp dmgroup. Note that the ``ADAPTIVE'' grouping may take a long time on large PHA files):

unix% punlearn add_grating_orders
unix% pset add_grating_orders pha2=acisf00459N002_pha2.fits
unix% pset add_grating_orders order=1
unix% pset add_grating_orders garm=MEG
unix% pset add_grating_orders garfm=acisf00459MEG_-1_garf.fits
unix% pset add_grating_orders garfp=acisf00459MEG_1_garf.fits
unix% pset add_grating_orders gtype=BIN
unix% pset add_grating_orders gspec=10
unix% pset add_grating_orders root=459
unix% add_grating_orders
Input PHA2 spectrum (acisf00459N002_pha2.fits): 
Order of the grating spectra to extract and add together (1): 
Grating Arm (HEG, MEG or LEG) (MEG): 
Negative order grating ARF (acisf00459MEG_-1_garf.fits): 
Positive order grating ARF (acisf00459MEG_1_garf.fits): 
Root name for output files (459): 

Input pha2 file is: acisf00459N002_pha2.fits
Using MEG grating ARF order 1: acisf00459MEG_-1_garf.fits
Using MEG grating ARF order 1: acisf00459MEG_1_garf.fits
The root filename for the output file is: 459


The coadded, grouped output spectrum is named 459_MEG_1_BIN10.pha
The coadded Effective Area is named 459_MEG_1.arf

The content of the parameter file may be checked using plist add_grating_orders.

Summary

The thread is now complete. The coadded 1st-order spectra are contained in the PHA1-like file named 459_MEG_1_BIN10.pha; the coadded +/- 1st order ARF is named 459_MEG_1.arf.

To fit this data in Sherpa:

sherpa> data 459_MEG_1_BIN10.pha
sherpa> rsp[arfname](,459_MEG_1.arf,)
sherpa> instrument = arfname

See the Fitting PHA Data with Multi-Component Source Models thread for more information.


Parameters for /home/username/cxcds_param/add_grating_orders.par


          pha2 = acisf00459N002_pha2.fits Input PHA2 spectrum
         order = 1                Order of the grating spectra to extract and add together
          garm = MEG              Grating Arm (HEG, MEG or LEG)
         garfm = acisf00459MEG_-1_garf.fits Negative order grating ARF
         garfp = acisf00459MEG_1_garf.fits Positive order grating ARF
          root = 459              Root name for output files
        (gtype = BIN)             Spectrum grouping type
        (gspec = 10)              Spectrum grouping specs (NONE,10,etc)
      (clobber = no)              Clobber existing output files?
      (verbose = 0)               Debug Level(0-5)
         (mode = ql)

History

14 Dec 2004	updated for CIAO 3.2: created Downloading add_grating_orders section
06 Dec 2005	reviewed for CIAO 3.3: no changes
01 Dec 2006	reviewed for CIAO 3.4: no changes