ASTR 506 Chandra assignment

I have set up the most recent version of the CIAO software on satie.astro.ubc.ca (this is a linux box). I have made a directory in /satieA/astr_506 which is world-writeable; go ahead and make yourself a working directory underneath this one. Note that if you are proud of the results you achieve here, you should copy them to a safe area for posterity, because I will wipe this directory once the course is over! You are welcome to copy the data onto your own machine and install the software yourself, but you can also just work on satie.

Part I (20 marks)
The major part of the assignment is to characterize and fit a spectrum to the May 2006 observation of the low-mass X-ray binary system GX 17+2, published in Cackett et al. ApJ 690, 1847 (2009). The data tarball is in /astro/satieA/astr_506/chandra_gx17+2.tar . You can either copy and untar this into your working area, then delete your copy of the tarfile, or else make softlinks to the files from your working area. You will need the files from both the primary and secondary directories.

The Chandra website has a whole lot of helpful information including "threads" which describe typical analysis procedures. Start by looking at the threads top page to get familiar with the basic concepts.

The GX 17+2 observation in question (PI Miller) was taken with the HETG (High-Energy Transmission Grating) and the ACIS-S. So you'll want to look at the grating spectroscopy page under HETG/ACIS-S for information on how to proceed. Note that this dataset was re-reduced in April 2008, so you don't need to recalibrate or "destreak" or re-obtain the spectra; you can start with ACIS-S Grating RMFs (check the Analysis Guide link for a discussion of machine responses) and work from there. Plan on processing only the HEG data, not the MEG data. You will need to make 6 RMFs (why?). The next step is making ARFs using fullgarf. You will also need to run this 6 times for the HEG spectra -- make sure you match up the correct rmf for each grating order. You may get warning messages; decide based on the documentation whether you need to worry about them. Add together the positive and negative first-order spectra with add_grating_orders. You can "group" (bin down) the spectra during this script, too.

Once you have created the response files, you will want to fit the data using Sherpa. This is a long-winded web page, but it tells you most of what you need to know. Also useful is this page. Some useful hints:

• "Notice" only the energies between 3 and 9 keV.
• Cackett et al. model the source as a combined blackbody, disk-blackbody and gaussian line, all multiplied by the absorption of the ISM. The models can be found at this page -- use the xs (XSPEC) models to match what Cackett et al did. Use their published parameters as starting points for your fits. You may want to try freezing different parameters to see what they do to the fit. Do not expect to replicate their results exactly; they fit RXTE data along with the Chandra data, and anyway the Chandra data are now calibrated differently.
• Make sure you have sensible starting values for all your parameters including the amplitude of the blackbody, or the fit will come out wrong!

Part II (5 marks) -- mostly because this is fun:
Use HEASARC to find and download some Chandra imaging data (your choice of object!) and follow the instructions in