Multidisciplinary studies of pulsar data and applications to Pulsar Timinig Arrays

Pulsars are fast-rotating, highly-magnetized neutron stars, visible at radio wavelenghts as pulsating obje ts thanks to two beams of emission that are fo ussed on the magneti poles and o-rotate with the star, the rotational axis of whi h is not aligned with the magneti one. The rotational stability and the possibility of measuring the time-of-arrival of the "pulses" of emission with an extreme pre ision allows to onstrain the physi al parameters of these sour es, and to undertake a wide number of studies. In this PhD Thesis, we exploit this hara teristi to explore several aspe ts of pulsar physi s, mainly related with the "Pulsar Timing Array" experiments. The first aspe t is pulsar polarization. Pulsars are among the most polarized obje ts of the radio sky ever known, however, the origin of pulsar polarization and of the "modes" of polarization that hara terize pulsar emission is still obs ure. Here we present a lassi polarimetri study of long-period pulsars dis overed during the High Time Resolution Universe survey and a new approa h to lassify the ombination of the polarized mode, along with a first appli ation to the data. The se ond aspe t dire tly on erns the Pulsar Timing Array experiments, whose main goal is a dire t dete tion of gravitational waves using pulsars. So far, no dete tion has been laimed. However, given the in reasing sensitivity of these experiments, it is extremely important to develop solid sanity he ks on the data to state if a future dete tion is genuine or not. We present here a study about false dete tion indu ed by orrelated signals in Pulsar Timing Array experiments, along with a sample of possible routines to mitigate these effe ts. The third aspe t is the long term de adal stability of millise ond pulsar template profiles in flux, that is one of the hypothesis of the pro edures to obtain extreme pre isions in measuring the pulsar parameters. We study 10 millise ond pulsars using the longest and most uniform data set in the world. We also present the surprising result that one of the sour es in our sample seems to present a sistemati profile variation along the years overed by the data set.