Data Analysis #1
Note that problems on home work #2 include printing out a ds9 image
including your source and background regions, a plot of your fitted
spectrum, and the results of your fitting.
Each group has an account (xray1, 2, or 3) which is set up to use the
tsch shell.
Setup to run ciao, the Chandra data
analysis package
- add the following line to your .cshrc file
alias ciao "source /usr/local/ciao/bin/ciao.csh"
- then either "source .csrhc" or logout and log back in
- type "ciao" and you should get a message that CAIO 3.3 is configured
FYI: ciao resides in /usr/local/ciao. Your data analysis will
also use CALDB = calibration data base, which resides in
/usr/local/CALDB.
Create a data area on the scratch disk
- use the following commands, substitute xray1, xray2 or xray3 for xrayn
cd /scratch
mkdir xrayn
Get the data set
- open a web browser on phobos and go to http://asc.harvard.edu/
- click on "Web ChaSeR Chandra Archive Search and Retrieval Interface"
- type "3c273" as the target name and search for observations
- put a check mark by ObsID 459, click "Add to Retrieval List"
- click "Retrieve Products"
- wait a bit
- click on the ftp link where your data will be available
- download the data file "package..." to your data directory
/scratch/xray1
- if you get bored waiting, or the transfer fails, you can copy the
data file from /scratch/kaaret/package_2268_060831180750.tar
- once the data is downloaded, move to /scratch/xrayn
- untar the data using "tar xvf package..."
- this makes a subdirectory 459 with files and directories below that
- unzip everything in all the subdirectories of 459
Extract ACIS Spectra and create
Response Files
- Follow the thread "Using psextract to Extract ACIS Spectra and
Response Files for Pointlike Sources" which can be found at
http://asc.harvard.edu/ciao/threads/psextract/
- Start by setting the observation-specific bad pixel files:
- move to /scratch/xrayn/459/primary and then do the following
commands:
punlearn ardlib
pset ardlib AXAF_ACIS5_BADPIX_FILE =
/scratch/xrayn/459/primary/acisf00459_000N002_bpix1.fits
pset ardlib AXAF_ACIS6_BADPIX_FILE =
/scratch/xrayn/459/primary/acisf00459_000N002_bpix1.fits
pset ardlib AXAF_ACIS7_BADPIX_FILE =
/scratch/xrayn/459/primary/acisf00459_000N002_bpix1.fits
pset ardlib AXAF_ACIS8_BADPIX_FILE =
/scratch/xrayn/459/primary/acisf00459_000N002_bpix1.fits
pset ardlib AXAF_ACIS9_BADPIX_FILE =
/scratch/xrayn/459/primary/acisf00459_000N002_bpix1.fits
- For now, don't worry about reprocessing your data.
- Note that psextract is a script which runs 9 different ciao tools.
Read over the documentation on each tool (click on the tool name under
the "Run psextract" entry) so that you understand its function.
Also, run psextract with verbose=2 in order to see the steps as they
are executed.
- For now, don't worry about creating an RMF with mkacisrmf.
- Be sure to print out your ds9 image showing your source and region
files.
Fit the spectrum
- Fit the spectrum, following the "Introduction to Fitting PHA Spectra"
thread at http://asc.harvard.edu/sherpa/threads/pha_intro/
- Using the absorbed power-law model is fine.
- Be sure to print out a plot of your spectrum along with your best
fit. Also, record the best fit parameters and the quality of the
fit.