Search For Pulsations Research Articles

The Green Bank North Celestial Cap Survey. IX. Timing Follow-up for 128 Pulsars

The Green Bank North Celestial Cap survey is one of the largest and most sensitive searches for pulsars and transient radio objects. Observations for the survey have finished; priorities have shifted toward long-term monitoring of its discoveries. In this study, we have developed a pipeline to handle large data sets of archival observations and connect them to recent, high-cadence observations taken using the Canadian Hydrogen Intensity Mapping Experiment telescope. This pipeline handles data for 128 pulsars and has produced measurements of spin, positional, and orbital parameters that connect data over observation gaps as large as 2000 days. We have also measured glitches in the timing residuals for five of the pulsars included and proper motion for 19 sources (13 new). We include updates to orbital parameters for 19 pulsars, including nine previously unpublished binaries. For two of these binaries, we provide updated measurements of post-Keplerian binary parameters, which result in much more precise estimates of the total masses of both systems. For PSR J0509+3801, the much improved measurement of the Einstein delay yields much improved mass measurements for the pulsar and its companion, 1.399(6) M ⊙ and 1.412(6) M ⊙, respectively. For this system, we have also obtained a measurement of the orbital decay due to the emission of gravitational waves, ṖB=−1.37(7)×10−12 , which is in agreement with the rate predicted by general relativity for these masses.

Non-detection of Radio Pulsations in the High-mass X-Ray Binary V0332+53 During Quiescence

Following recent discoveries of ultra-long-period radio-loud neutron stars located beyond death line models in the pulsar period-period derivative diagram, we performed a radio pulsation search in the high-mass X-ray binary V0332+53 during quiescence. Although the period and magnetic field of the neutron star in this binary make it the most promising high-mass X-ray binary to explore for this purpose, the GBT observations do not reveal radio pulsations. Here, We present the duty-cycle-dependent flux density limits on the presence of any pulsations and briefly discuss its possible origins: the intrinsic absence or faintness of pulsations, the presence of low-level residual accretion, or eclipses and/or pulse scattering due to the presence of a massive binary companion.

Pushchino multibeams pulsar search – IV. Detection of new pulsars at declinations −9° < δ < +55°

ABSTRACT The search for pulsars in monitoring data obtained at the radio telescope Large Phased Array (LPA) at a frequency of 111 MHz was carried out. Daily round-the-clock observations were carried out for about 3000 d. The duration of the observation session for each direction in the sky was 3.5 min d−1. The search for pulsars was carried out using power spectra. To search for weak pulsars, power spectra were summed up. The expected increase in sensitivity was 35–40 times compared to observations in one session. In a blind search, 330 pulsars with regular radiation were detected, with periods (P) from 0.0333 to 3.7455 s and dispersion measures (DMs) up to 249 pc cm−3. 39 pulsars turned out to be new. Average profiles were obtained for six pulsars. The DMs for seven pulsars previously detected on the LPA have been clarified.

Discovery of radio eclipses from 4FGL J1646.5−4406: a new candidate redback pulsar binary

ABSTRACT Large widefield surveys make possible the serendipitous discovery of rare subclasses of pulsars. One such class are ‘spider’-type pulsar binaries, comprised of a pulsar in a compact orbit with a low-mass (sub)stellar companion. In a search for circularly polarized radio sources in Australian Square Kilometre Array Pathfinder (ASKAP) Pilot Survey observations, we discovered highly variable and circularly polarized emission from a radio source within the error region of the γ-ray source 4FGL J1646.5−4406. The variability is consistent with the eclipse of a compact, steep-spectrum source behind ablated material from a companion in an ∼5.3 h binary orbit. Based on the eclipse properties and spatial coincidence with 4FGL J1646.5−4406, we argue that the source is likely a recycled pulsar in a ‘redback’ binary system. Using properties of the eclipses from ASKAP and Murchison Widefield Array observations, we provide broad constraints on the properties of the eclipse medium. We identified a potential optical/infrared counterpart in archival data consistent with a variable low-mass star. Using the Parkes radio telescope ‘Murriyang’ and the Meer Karoo Array Telescope (MeerKAT) , we searched extensively for radio pulsations but yielded no viable detections of pulsed emission. We suggest that the non-detection of pulses is due to scattering in the intra-binary material, but scattering from the interstellar medium can also plausibly explain the pulse non-detections if the interstellar dispersion measure exceeds ∼600 pc cm−3. Orbital constraints derived from optical observations of the counterpart would be highly valuable for future γ-ray pulsation searches, which may confirm the source nature as a pulsar.

NGC 2403 XMM4: evidence for a super-Eddington neutron star with a possible transient pulsation

ABSTRACT We present a study of the X-ray source NGC 2403 XMM4 (4XMM J073702.2+653934) based on 20 yr of archival observations with XMM–Newton, Chandra, Swift, and NuSTAR. Although it has previously been classified as an ultraluminous X-ray source (ULX), we show that its luminosity rarely, if ever, passes the $10^{39} \rm \, erg \, s^{-1}$ threshold luminosity for a ULX. It does, however, behave very similarly to ULXs, with its 0.3–10 keV spectra well described by two thermal components, the softer of which behaves consistently with the expectations for an advection-dominated disc (L ∝ T1.49±0.85), and we find tentative evidence for an extra spectral component above 10 keV. We also find moderately significant evidence for an absorption feature in one spectrum that could originate in an outflowing wind, although a cyclotron resonance scattering feature is also a possibility. Most intriguingly, we find a possible transient pulsation at ∼3.32 Hz in a short segment of one observation using an accelerated pulsation search. This evidence suggests that NGC 2403 XMM4 is displaying many of the hallmarks of super-Eddington accretion at luminosities in the range $5 \!-\! 10 \times 10^{38} \rm \, erg \, s^{-1}$ that, when considered alongside the putative pulsation, points to the presence of a neutron star as the accreting object this system.

A Search for Radio Pulsars in Supernova Remnants Using FAST with One Pulsar Discovered

We report the results of a search for radio pulsars in five supernova remnants (SNRs) with the FAST telescope. The observations were made using the 19-beam receiver in “snapshot” mode. The integration time for each pointing was 10 min. We discovered a new pulsar, PSR J1845–0306, which has a spin period of 983.6 ms and a dispersion measure of 444.6 ± 2.0 cm−3⋅pc, in observations of SNR G29.6+0.1. To judge the association between the pulsar and the SNR, further verification is needed. We also re-detected some known pulsars in the data from SNRs G29.6+0.1 and G29.7–0.3. No pulsars were detected in the observations of the other three SNRs.

Properties of PSR J1023+0038 Based on Kepler, TESS, and FAST

The pulsar system PSR J1023+0038 is a very interesting binary with radio millisecond pulsar and low-mass X-ray binary transitions, which depend on the stellar accretion process. We have used Kepler light curves with 1 minute cadence and TESS light curves with 2 minute cadence to study the flare properties of PSR J1023+0038. We detected 516 flare events in the K2 data and 84 flare events in the TESS survey data. We determined the flare rise and delay times, the flare durations and amplitudes, and flare energies. We obtained a value of the power-law index of 0.359 ± 0.023 between the flare energies and decay times, which is similar to the theoretically predicted value of 1/3. This in turn indicates that PSR J1023+0038 might be exhibiting physical mechanisms described by magnetic reconnection theory. Using the maximum likelihood estimation method, we also calculated the power-law index of the cumulative flare frequency distribution, finding 1.87 ± 0.27 for the Kepler data and 1.74 ± 0.29 for the TESS data. Meanwhile, we reduced six FAST observations of PSR J1023+0038 from 2019–2021 using a standard pulsar search procedure. We report that we detected a prompt signal with a period compatible with that found in previous observations of PSR J1023+0038. However, there are several reasons (statistical, excess DM, pulse shape, etc.) as to why the association is not likely.

A Pulsar Vector Observation-Based Link Acquisition Method for X-Ray Communications

X-ray communication (XCOM) is an emerging laser communication technique for deep space applications. Traditional link acquisition of laser communications depends significantly on Earth support and shows little autonomy. For XCOM, a pulsar vector observation-based link acquisition method is proposed, which utilizes noncooperative pulsars in deep space as beacons to acquire absolute attitude information and accomplish link acquisition. Firstly, a pulsar vector observation model was established based on the coordinate definition of the X-ray detector and X-ray collimator model. Secondly, a modified “success-failure” pulsar vector search algorithm with two degrees of freedom was proposed to acquire the pulsar vector. With the pulsar vector and the relative attitude obtained from inertial sensors, the link acquisition pointing vector could be determined. Finally, the performance of the proposed method was evaluated using numerical experiments, and factors that influence the performance are discussed and analyzed.

A Search for Pulsars around Sgr A* in the First Event Horizon Telescope Data Set

In 2017 the Event Horizon Telescope (EHT) observed the supermassive black hole at the center of the Milky Way, Sagittarius A* (Sgr A*), at a frequency of 228.1 GHz (λ = 1.3 mm). The fundamental physics tests that even a single pulsar orbiting Sgr A* would enable motivate searching for pulsars in EHT data sets. The high observing frequency means that pulsars—which typically exhibit steep emission spectra—are expected to be very faint. However, it also negates pulse scattering, an effect that could hinder pulsar detections in the Galactic center. Additionally, magnetars or a secondary inverse Compton emission could be stronger at millimeter wavelengths than at lower frequencies. We present a search for pulsars close to Sgr A* using the data from the three most sensitive stations in the EHT 2017 campaign: the Atacama Large Millimeter/submillimeter Array, the Large Millimeter Telescope, and the IRAM 30 m Telescope. We apply three detection methods based on Fourier-domain analysis, the fast folding algorithm, and single-pulse searches targeting both pulsars and burst-like transient emission. We use the simultaneity of the observations to confirm potential candidates. No new pulsars or significant bursts were found. Being the first pulsar search ever carried out at such high radio frequencies, we detail our analysis methods and give a detailed estimation of the sensitivity of the search. We conclude that the EHT 2017 observations are only sensitive to a small fraction (≲2.2%) of the pulsars that may exist close to Sgr A*, motivating further searches for fainter pulsars in the region.

Potential pulsars prediction based on machine learning

The search for potential pulsars is a difficult job because of the complex nature of the signals and the vast amounts of data involved. In the last few years, a lot of researchers have tried to use machine learning to deal with complex data. This essay examines how machine learning could help to identify potential pulsars, exploring the various types of algorithms and the challenges and limitations associated with this approach. The essay mainly explored three themes: the training of 5 algorithms for the identification of pulsars, the improvement of 2 algorithms by adjusting parameters, and the simplification of the data to improve the processing speed and performance of the algorithms on prediction. All 5 algorithms reached great accuracy after adjustment and the simplification of the input data can help to boost the prediction time and accuracy for future research about pulsars. The essay highlights the need for further research in this area, as machine learning has demonstrated strong potential for pulsar prediction. By analyzing the results of several previous studies, this essay underscores the importance of machine learning as an approach for predicting potential pulsars and made improvements to the performance of current algorithms by adjusting parameters and simplifying the data.

PulsarX: A new pulsar searching package

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.

Digging a little deeper: characterizing three new extreme ULX candidates

ABSTRACT A prime motivation for compiling catalogues of any celestial X-ray source is to increase our numbers of rare subclasses. In this work, we take a recent multimission catalogue of ultraluminous X-ray sources (ULXs) and look for hitherto poorly-studied ULX candidates that are luminous ($L_{\rm X} \ge 10^{40}\,{\rm erg\,s}^{-1}$), bright ($f_{\rm X} \ge 5 \times 10^{-13}\,{\rm erg\,cm}^{-2}\,{\rm s}^{-1}$), and have archival XMM–Newton data. We speculate that this luminosity regime may be ideal for identifying new pulsating ULXs (PULXs), given that the majority of known PULXs reach similar high luminosities. We find three sources that match our criteria and study them using archival data. We find 4XMM J165251.5−591503 to possess a bright and variable Galactic optical/IR counterpart, and so conclude it is very likely to be a foreground interloper. 4XMM J091948.8−121429 does appear to be an excellent ULX candidate associated with the dwarf irregular galaxy PGC 26378, but has only one detection to date with low data quality. The best data set belongs to 4XMM J112054.3+531040 which we find to be a moderately variable, spectrally hard (Γ ≈ 1.4) X-ray source located in a spiral arm of NGC 3631. Its spectral hardness is similar to known PULXs, but no pulsations are detected by accelerated pulsation searches in the available data. We discuss whether other missions provide objects for similar studies and compare this method to others suggested for identifying good PULX candidates.

A stacking survey of gamma-ray pulsars

ABSTRACT We report on a likelihood-stacking search for γ-ray pulsars at 362 high-latitude locations that coincide with known radio pulsar positions. We observe a stacked signal conservatively 2.5σ over the background. Stacking their likelihood profiles in spectral parameter space implies a pulsar-like spectral index and a characteristic flux a factor of 2 below the Fermi Large Area Telescope point-source sensitivity, assuming isotropic/unbeamed emission from all sample pulsars. The same procedures performed on empty control fields indicate that the pulsars as a population can be distinguished from the background with a Δ(TS) = 28, where TS refers to test statistic, at the peak location (or 4.8σ), and the stacked spectra of the control fields are distinctly softer than those of the pulsars. This study also probes a unique region of parameter space populated by low $\dot{E}$ pulsars, most of which have no γ-ray ephemeris available, and is sensitive to high duty cycles. We also discuss the possible γ-ray emission mechanism from such pulsars.

New constraints on the kinematic, relativistic, and evolutionary properties of the PSR J1757−1854 double neutron star system

ABSTRACT PSR J1757−1854 is one of the most relativistic double neutron star binary systems known in our Galaxy, with an orbital period of $P_\text{b}=4.4\, \text{h}$ and an orbital eccentricity of e = 0.61. As such, it has promised to be an outstanding laboratory for conducting tests of relativistic gravity. We present the results of a 6-yr campaign with the 100-m Green Bank and 64-m Parkes radio telescopes, designed to capitalize on this potential. We identify secular changes in the profile morphology and polarization of PSR J1757−1854, confirming the presence of geodetic precession and allowing the constraint of viewing geometry solutions consistent with General Relativity. We also update PSR J1757−1854’s timing, including new constraints of the pulsar’s proper motion, post-Keplerian parameters, and component masses. We conclude that the radiative test of gravity provided by PSR J1757−1854 is fundamentally limited to a precision of 0.3 per cent due to the pulsar’s unknown distance. A search for pulsations from the companion neutron star is also described, with negative results. We provide an updated evaluation of the system’s evolutionary history, finding strong support for a large kick velocity of $w\ge 280\, \rm{km\,s}^{-1}$ following the second progenitor supernova. Finally, we reassess PSR J1757−1854’s potential to provide new relativistic tests of gravity. We conclude that a 3-σ constraint of the change in the projected semimajor axis ($\dot{x}$) associated with Lense–Thirring precession is expected no earlier than 2031. Meanwhile, we anticipate a 3-σ measurement of the relativistic orbital deformation parameter δθ as soon as 2026.

Multimessenger observations of double neutron stars in the Galactic disk with gravitational and radio waves

We evaluate the prospects for radio follow-up of the double neutron stars (DNSs) in the Galactic disk that could be detected through future space-borne gravitational wave (GW) detectors. We first simulate the DNS population in the Galactic disk that is accessible to space-borne GW detectors according to the merger rate from recent LIGO results. Using the inspiraling waveform for the eccentric binary, the average number of the DNSs detectable by TianQin (TQ), LISA, and $\mathrm{TQ}+\mathrm{LISA}$ are 217, 368, and 429, respectively. For the joint GW detection of $\mathrm{TQ}+\mathrm{LISA}$, the forecasted parameter estimation accuracies, based on the Fisher information matrix, for the detectable sources can reach the levels of $\mathrm{\ensuremath{\Delta}}{P}_{\mathrm{b}}/{P}_{\mathrm{b}}\ensuremath{\lesssim}{10}^{\ensuremath{-}6}$, $\mathrm{\ensuremath{\Delta}}\mathrm{\ensuremath{\Omega}}\ensuremath{\lesssim}100\text{ }\text{ }{\mathrm{deg}}^{2}$, $\mathrm{\ensuremath{\Delta}}e/e\ensuremath{\lesssim}0.3$, and $\mathrm{\ensuremath{\Delta}}{\stackrel{\ifmmode \dot{}\else \textperiodcentered \fi{}}{P}}_{\mathrm{b}}/{\stackrel{\ifmmode \dot{}\else \textperiodcentered \fi{}}{P}}_{\mathrm{b}}\ensuremath{\lesssim}0.02$. These estimation accuracies are fitted in the form of power-law function of signal-to-noise ratio. Next, we simulate the radio pulse emission from the possible pulsars in these DNSs according to pulsar beam geometry and the empirical distributions of spin period and luminosity. For the DNSs detectable by $\mathrm{TQ}+\mathrm{LISA}$, the average number of DNSs detectable by the follow-up pulsar searches using the Parkes, FAST, SKA1, and SKA are 8, 10, 43, and 87, respectively. Depending on the radio telescope, the average distances of these GW-detectable pulsar binaries vary from 1 to 7 kpc. Considering the dominant radiometer noise and phase jitter noise, the timing accuracy of these GW-detectable pulsars can be as low as 70 ns while the most probable value is about $100\text{ }\text{ }\mathrm{\ensuremath{\mu}}\mathrm{s}$.

An RFI Mitigation Pipeline for CRAFTS Multi-beam Data Based on Signal Cross-Correlation Function and SumThreshold Algorithm

The increasing radio frequency interference (RFI) is a well-recognized problem in radio astronomy research. Pulsars and Fast Radio Bursts (FRBs) are high-priority science targets of the ongoing Commercial Radio Astronomy FAST Survey (CRAFTS). To improve the quality of RFI removal in searches of pulsars and FRBs based on CRAFTS multi-beam data, we here propose an intuitive but powerful RFI mitigation pipeline (CCF-ST). The “CCF-ST” is a spatial filter constructed by signal cross-correlation function (CCF) and Sum-Threshold (ST) algorithm. The RFI marking result is saved in a “mask” file, a binary format for RFI masks in PRESTO. Three known pulsars, PSR B0525-21, PSR B0621-04, and PSR J0943 + 2252 from CRAFTS L-band 19 beams data are used for evaluation of the performance of CCF-ST in comparison with other methods, such as PRESTO’s “rfifind”, ArPLS-ST and ArPLS-SF. The result shows that CCF-ST can reduce effective data loss rate and improves the detected signal-to-noise ratio of the pulsations by ∼26% and ∼18% respectively compared with PRESTO’s “rfifind” and ArPLS-ST. The CCF-ST also has the advantage of low computational cost, e.g., reducing the time consumption by ∼40% and memory consumption by ∼90% compared with ArPLS-SF. We expect that the new RFI mitigation and analysis toolkit (CCF-ST) demonstrated in this paper can be applied to CRAFTS and other multi-beam telescope observations to improve the data quality and efficiency of pulsar and FRB searches.

Investigation of a Machine learning methodology for the SKA pulsar search pipeline

The SKA pulsar search pipeline will be used for real time detection of pulsars. Modern radio telescopes, such as SKA will be generating petabytes of data in their full scale of operation. Hence, experience-based and data-driven algorithms are being investigated for applications, such as candidate detection. Here, we describe our findings from testing a state of the art object detection algorithm called Mask R-CNN to detect candidate signatures in the SKA pulsar search pipeline. We have trained the Mask R-CNN model to detect candidate images. A custom semi-auto annotation tool was developed and investigated to rapidly mark the regions of interest in large datasets. We have used a simulation dataset to train and build the candidate detection algorithm. A more detailed analysis is planned. This paper presents details of this initial investigation highlighting the future prospects.

Proteomic analysis identifies dysregulated proteins and associated molecular pathways in a cohort of gallbladder cancer patients of African ancestry

BackgroundGallbladder cancer (GBC) is a lethal cancer with a poor prognosis. The lack of specific and sensitive biomarkers results in delayed diagnosis with most patients presenting at late stages of the disease. Furthermore, there is little known about the molecular mechanisms associated with GBC, especially in patients of African ancestry. This study aimed to determine dysregulated proteins in South African GBC patients to identify potential mechanisms of the disease progression and plausible biomarkers.MethodsTissues (27 GBC, 13 Gallstone disease, and 5 normal tissues) and blood plasma (54 GBC and 73 Benign biliary pathology) were obtained from consenting patients. Protein extraction was performed on all tissues and liquid chromatography-mass spectrometry was used for proteomic profiling. A project-specific spectral library was built using the Pulsar search algorithm. Principal component and Spearman’s rank correlation analyses were performed using PAST (V4.07b). Pathway and Network analyses were conducted using REACTOME (v3.7) and stringAPP (v1.7.0), respectively.ResultsIn the tissue sample group, there were 62 and 194 dysregulated proteins in GBC compared to normal and gallstone groups, respectively. In the plasma group, there were 33 altered proteins in GBC compared to the benign biliary pathology group. We found 9 proteins (APOA1, APOA2, RET4, TTR, HEMO, HBB, HBA, PIGR, and APOE) to be commonly dysregulated in both tissue and plasma. Furthermore, a subset analysis demonstrated that 2 proteins, S100A8 and S100A9, were downregulated in GBC patients with GD history compared to those without. Pathway analysis showed that the dysregulated proteins in GBC patients were enriched in pathways involved in smooth muscle contraction, metabolism, ECM organization, and integrin cell surface interactions.ConclusionThe identified dysregulated proteins help in understanding GBC molecular mechanisms in our patient group. Furthermore, the alteration of specific proteins in both tissue and plasma samples suggests their potential utility as biomarkers of GBC in this sample cohort.

Fermi-LAT Gamma-Ray Emission Discovered from the Composite Supernova Remnant B0453-685 in the Large Magellanic Cloud

We report the second extragalactic pulsar wind nebula (PWN) to be detected in the megaelectronvolt–gigaelectronvolt band by the Fermi-LAT, located within the Large Magellanic Cloud. The only other known PWN to emit in the Fermi band outside of the Milky Way is N157B, which lies to the west of the newly detected gamma-ray emission at an angular distance of 4°. Faint, pointlike gamma-ray emission is discovered at the location of the composite supernova remnant (SNR) B0453-685 with a ∼4σ significance with energies ranging from 300 MeV–2 TeV. We present the Fermi-LAT data analysis of the new gamma-ray source, coupled with a detailed multiwavelength investigation to understand the nature of the observed emission. Combining the observed characteristics of the SNR and the physical implications from broadband modeling, we argue it is unlikely that the SNR is responsible for the gamma-ray emission. While the gamma-ray emission is too faint for a pulsation search, we try to distinguish between any pulsar and PWN component of SNR B0453-685 that could be responsible for the observed gamma-ray emission using semi-analytic models. We determine the most likely scenario is that the old PWN (τ ∼ 14,000 yr) within B0453-685 has been impacted by the return of the SNR reverse shock with a possible substantial pulsar component below 5 GeV.

Discovery of 37 new pulsars through GPU-accelerated reprocessing of archival data of the Parkes multibeam pulsar survey

ABSTRACT We present the discovery of 37 pulsars from ∼ 20 yr old archival data of the Parkes Multibeam Pulsar Survey using a new FFT-based search pipeline optimized for discovering narrow-duty cycle pulsars. When developing our pulsar search pipeline, we noticed that the signal-to-noise ratios of folded and optimized pulsars often exceeded that achieved in the spectral domain by a factor of two or greater, in particular for narrow duty cycle ones. Based on simulations, we verified that this is a feature of search codes that sum harmonics incoherently and found that many promising pulsar candidates are revealed when hundreds of candidates per beam even with modest spectral signal-to-noise ratios of S/N∼5–6 in higher-harmonic folds (up to 32 harmonics) are folded. Of these candidates, 37 were confirmed as new pulsars and a further 37 would have been new discoveries if our search strategies had been used at the time of their initial analysis. While 19 of these newly discovered pulsars have also been independently discovered in more recent pulsar surveys, 18 are exclusive to only the Parkes Multibeam Pulsar Survey data. Some of the notable discoveries include: PSRs J1635−47 and J1739−31, which show pronounced high-frequency emission; PSRs J1655−40 and J1843−08 belong to the nulling/intermittent class of pulsars; and PSR J1636−51 is an interesting binary system in a ∼0.75 d orbit and shows hints of eclipsing behaviour – unusual given the 340 ms rotation period of the pulsar. Our results highlight the importance of reprocessing archival pulsar surveys and using refined search techniques to increase the normal pulsar population.