Time Series Analysis Using TS11

Time series analysis allows you to search for periodic variability. Periodic variability means that the varying brightness of the star repeats with a good degree of precision. It's important to remember that not all variable stars are strictly periodic, even though they may vary in brightness. Cataclysmic variables vary in brightness and are usually said to have a "period" even though there can be great differences in time between their outbursts.

The program TS11, provided by the AAVSO, will allow you to make basic time series analysis of your variable-star data, and usually assist you in determining a period for some variable stars. In most cases, pulsating stars are the best candidates for getting the best results from this program

The most important thing to remember when using TS11 is that the data must be in columns, usually with the first column being the Julian date. The second column must be separated by one space; not a tab, or other such delimiter. The second column is usually the magnitude estimate. An example of a data file ready for TS11 is indicated next:

3456.123 6.5

3456.124 6.6

3456.125 6.7

3456.126 6.8

There is one space, and one space only, between the JD and the estimate. Because TS11 is a DOS program, the file name must be kept to eight characters or less. Be careful when you name your file, especially when you have many files containing data for the same star.

When you download your copy of TS11 from the AAVSO Web site, one of the files will be the instructions. Spend a couple of hours analyzing different data sets so that you

268 Observing become familiar with the capabilities, and limitations, of this program.

Appendix C

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