Cepheid Variables

Cepheid Variables is a experiment in 2nd year lab at the University of Manchester where students use a program called 'GAIA' to analyse data from the Hubble Space Telescope.

Initial Data
First it is required that students collect all the data using the GAIA software as shown by a lab demonstrator, this is a fairly simple affair. However since there are many cepheid variable stars that each need graphs, a script has been written that formats each graph exactly as required. The student must input the data into a .csv file, which is then loaded into the program, and upon being prompted for the number star which is being graphed, a fully labelled graph is produced.

The student must input the equation into the script for dealing with fractional errors and understand it.

http://tinyurl.com/pm3t47z

Period (or Epoch) Folding
It is then required that the period of the cepheid variable stars be found using the numerical method of 'period folding'. This involves folding the graph over on itself with different periods and seeing how well they fit together. From this inspection the period can be deduced. The program for doing so is linked below. Since the equation for period folding is given by the demonstrator, it has been left in the script, however for the purposes of the interview you should be able to understand this.

The program has scope for improvement, whereby the fit of the fold is analysed by the program itself.

http://tinyurl.com/qj8jztl

Period Luminosity Relation & Distance
