The GMRT High Resolution Southern Sky Survey for pulsars and transients -- III: searching for long period pulsars

TL;DR

This study compares the sensitivity of Fast Folding Algorithm (FFA) and FFT searches for long period pulsars, demonstrating FFA's superior performance in real telescope noise conditions and leading to new pulsar discoveries.

Contribution

It presents a new FFA-based search pipeline for the GHRSS survey, improving detection of long period pulsars and reporting two new pulsar discoveries.

Findings

FFA outperforms FFT in detecting long period pulsars in real noise conditions.

Re-detected 43 known pulsars with higher signal-to-noise ratios using FFA.

Discovered two new pulsars, including a long period one with a short duty cycle.

Abstract

Searching for periodic non-accelerated signals in presence of ideal white noise using the fully phase-coherent Fast Folding Algorithm (FFA) is theoretically established as a more sensitive search method than the Fast Fourier Transform (FFT) search with incoherent harmonic summing. In this paper, we present a comparison of the performance of an FFA search implementation using RIPTIDE and an FFT search implementation using PRESTO, over a range of signal parameters with white noise and with real telescope noise from the GHRSS survey with the uGMRT. We find that FFA search with appropriate de-reddening of time series, performs better than FFT search with spectral whitening for long period pulsars in real GHRSS noise conditions. We describe an FFA search pipeline implemented for the GHRSS survey looking for pulsars over a period range of 0.1 s to 100 s and up to dispersion measure of 500 pc cm$^{-3}$. We processed GHRSS survey data covering $\sim$ 1500 degree$^2$ of the sky with this pipeline. We re-detected 43 known pulsars with better signal-to-noise in the FFA search than in the FFT search. We also report discovery of two new pulsars including a long period pulsar having a short duty-cycle with this FFA search pipeline. The population of long period pulsars with periods of several seconds or higher can help to constrain the pulsar death-line.