Periods and classifications of RR Lyrae in M15

Of these RR Lyrae stars, two were previously reported but without a determination of the period. In addition, we identify five Type II Cepheid variable stars for which we report three novel period determinations, and a further 34 stars with uncertain classifications and periods.

We discuss the development and subsequent application to our data of a new PYTHON package, Period-determination and Identification Pipeline Suite (PIPS), based on a new adaptive free-form fitting technique to detect the periods of variable stars with a clear treatment of uncertainties.