AIM
To get familiar with some common timing analysis tools, such as power density spectra, autocorrelation functions and epoch folding. Simulate and investigate the appearence of a few different types of signals and study the influence of noise. Find, download and analyse archive data from RXTE all sky monitor, ASM. ASM is continously scanning the sky in soft X-rays. Each day most bright X-ray sources are measured a few times. These data are available online and can therefore be downloaded and analysed.

Background
Fourier transform, autocorrelation function, epoch folding, detrending, Monte Carlo simulation, chi square, error estimation.

Linux
If you are new to Linux/Unix take a look at this command summary. For an online unix course.

To start the DES7 program.
Open a second terminal window and cd to DES7 in both windows. Run the program in one and idl in the other by typing in window 1 and 2 respectively:
1.     des7
2.     idl
        desdraw
 
Before the lab you should take a look at the online des7 manual.

1. Run simulations and compute power density spectra
  In each case do the following sequence 34. Simulation, 3. Detrend 4. 16. Power spectrum
  Compute one power spectrum without detrending first. How and why does the power spectrum differ?

- Poisson noise
- Coherent oscillation (sinusoid)
   Try a few different amplitude - noise level combinations and two different data lengths. 
 - Amplitude modulated sinusoid
 - A few cases with different parameter settings of either a quasi-periodic oscillation
    (2nd order autogressive process) or shot noise.

2. Epoch folding
-  Simulate a sinusoid in channel2 (x2) (in simulation store errors, internal) and make an epoch folding analysis. (Option 24, then 31. DES-Folding in the submenue, but remember to set folding period [Note: Period not frequency])
   Plot chi-square and pulse profile (In "40. View ...."). Rerun with Monte-Carlo simulation option set to at
    least 10 to estimate errors for the period and amplitude obtained from the analysis.
    (Note: Disregard the messages written during execution (for testing purposes only).
     Compare with a period determination from a power density spectrum. 

3. Period analysis of RXTE/ASM data 
     Go to the ASM lightcurve page.
    Click on "data downloads" in the left column.
     Select a source and possibly a start and stop time. (You may e.g. select an accreting X-ray pulsar)
    Make sure the "No Header" option is set.
    Click on the button "Retrive Entire Light Curve Files via HTTP links"
    In the file list window that opens, click on the file you want to download with the right mouse button and select "Save link target as".
    Now use the tools above to analyse the periods that can study from these observations in your particular source.