PulsarX: A new pulsar searching package

Abstract

Context. Pulsar surveys with modern radio telescopes are becoming increasingly computationally demanding. This is particularly true for wide field-of-view pulsar surveys with radio interferometers and those conducted in real or quasi-real time. These demands result in data analysis bottlenecks that can limit the parameter space covered by the surveys and diminish their scientific return. Aims. In this paper we address the computational challenge of ‘candidate folding’ in pulsar searching, presenting a novel, efficient approach designed to optimise the simultaneous folding of large numbers of pulsar candidates. We provide a complete folding pipeline appropriate for large-scale pulsar surveys that includes radio frequency interference mitigation, de-dispersion, folding, and parameter optimisation. Methods. By leveraging the fast discrete dispersion measure transform (FDMT) algorithm, we have developed an optimised and cache-friendly implementation that we term the pruned FDMT (pFDMT). This implementation is specifically designed for candidate folding scenarios where the candidates are broadly distributed in dispersion measure space. The pFDMT approach efficiently reuses intermediate processing results and prunes the unused computation paths, resulting in a significant reduction in arithmetic operations. In addition, we propose a novel folding algorithm based on the Tikhonov-regularised least squares method that can improve the time resolution of the pulsar profile. Results. We present the performance of its real-world application as an integral part of two major pulsar search projects conducted with the MeerKAT telescope: the MPIfR-MeerKAT Galactic Plane Survey (MMGPS) and the Transients and Pulsars with MeerKAT (TRAPUM) project. In our processing of approximately 500 candidates, the theoretical number of de-dispersion operations can be reduced by a factor of around 50 when compared to brute-force de-dispersion, which scales with the number of candidates.

The MPIfR-MeerKAT Galactic Plane Survey

“…J1208−5936 was discovered on 30 May 2021 in an observation from May 6th as a topocentric 28.706-ms signal in the FFT with signal-to-noise ratio S /N = 15.1, a line-of-sight acceleration of −8.86 m s −2 , DM = 344.2 pc cm −3 and a PulsarX 5 (Men et al 2023) fold of S /N ≈ 19. Upon discovery, we performed a first 20 min-long follow-up observation at the same position on 4 June 2021.…”

“…We folded each observation into archives with the dspsr 9 , where cycles of the pulsar are stacked every 8 or 10 seconds. We then cleaned these archives with the clfd 10 radio-frequency interference (RFI) excision software (Morello et al 2019). These resulting data allow for accurate tracking of the evolution or drift of the pulse over time, leading to measurements of the barycentric period (P bary ) at each observing epoch (t obs ) with the PSRCHIVE/pdmp 11 software (Hotan et al 2004), but also with the timing software TEMPO2 12 (Hobbs et al 2006;Edwards et al 2006) for observations with large line-of-sight acceleration or jerk.…”

“…Subsequently and with dspsr, all PTUSE data were folded into 1024-bin, fourchannel archives, and APSUSE data (when PTUSE data were not available) were folded into 512-bin, four-channel archives, with sub-integration times of at most 10 min in length in both cases. These files had been excised of RFI a priori at full time and frequency resolution using first the clfd 16 software (Morello et al 2019) and then manually with PSRCHIVE/paz upon inspection of the remaining RFI. Finally, pat was used with the Fourier Phase Gradient algorithm (Taylor 1992) to generate 384 frequency-resolved ToAs.…”

“…We restricted our FFA search to periods above 100 ms, on the basis that shorter periods would have easily been detected by the presto FFT search. We used the riptide 25 software (Morello et al 2019) to perform a non-accelerated FFA search on the de-modulated time series and fold the resulting candidates. For that we implemented the following steps with our presto wrapper pipelines demodulate-search 26 .…”