Quantitative exploration of the similarity of gamma-ray pulsar light curves

Abstract

We introduce and apply a methodology based on dynamic time warping (DTW) to compare the whole set of gamma-ray light curves reported in the Third Fermi-Large Area Telescope Pulsar Catalogue. Our method allows us to quantitatively measure the degree of global similarity between two light curves beyond comparing indicators such as how many peaks there are, which is their separation, width, and height. Once the morphology of the light curve is showcased via background subtraction, min-max scaler normalization, and rotations are considered to take into account that phase 0 is arbitrary, the level of detail with which light curves of different pulsars appear is revealed. In many cases their similarity is striking and occurs disregarding any other timing, physical, or spectral property. In particular, some MSPs and young pulsars share detailed light curve morphology.