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1. The Green Bank North Celestial Cap Survey. VIII. 21 New Pulsar Timing Solutions

   https://doi.org/10.3847/1538-4357/aceef7  

   Fiore, W.; Levin, L.; McLaughlin, M. A.; Anumarlapudi, A.; Kaplan, D. L.; Swiggum, J. K.; Agazie, G. Y.; Bavisotto, R.; Chawla, P.; DeCesar, M. E.; et al (October 2023, The Astrophysical Journal)

   Abstract We present timing solutions for 21 pulsars discovered in 350 MHz surveys using the Green Bank Telescope (GBT). All were discovered in the Green Bank North Celestial Cap pulsar survey, with the exception of PSR J0957−0619, which was found in the GBT 350 MHz Drift-scan pulsar survey. The majority of our timing observations were made with the GBT at 820 MHz. With a spin period of 37 ms and a 528 days orbit, PSR J0032+6946 joins a small group of five other mildly recycled wide binary pulsars, for which the duration of recycling through accretion is limited by the length of the companion’s giant phase. PSRs J0141+6303 and J1327+3423 are new disrupted recycled pulsars. We incorporate Arecibo observations from the NANOGrav pulsar timing array into our analysis of the latter. We also observed PSR J1327+3423 with the Long Wavelength Array, and our data suggest a frequency-dependent dispersion measure. PSR J0957−0619 was discovered as a rotating radio transient, but is a nulling pulsar at 820 MHz. PSR J1239+3239 is a new millisecond pulsar (MSP) in a 4 days orbit with a low-mass companion. Four of our pulsars already have published timing solutions, which we update in this work: the recycled wide binary PSR J0214+5222, the noneclipsing black widow PSR J0636+5128, the disrupted recycled pulsar J1434+7257, and the eclipsing binary MSP J1816+4510, which is in an 8.7 hr orbit with a redback-mass companion. 

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

   https://doi.org/10.1093/mnras/stad508  

   Sengar, R.; Bailes, M.; Balakrishnan, V.; Bernadich, M. C. i.; Burgay, M.; Barr, E. D.; Flynn, C. M. L.; Stevenson, R. Shannon S.; Wongphechauxsorn, J. (February 2023, Monthly Notices of the Royal Astronomical Society)

   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. 

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3. A Pilot Study of Nulling in 22 Pulsars Using Mixture Modeling

   https://doi.org/10.3847/1538-4357/acbb68  

   Anumarlapudi, Akash; Swiggum, Joseph_K; Kaplan, David_L; Fichtenbauer, Travis_D_J (May 2023, The Astrophysical Journal)

   Abstract The phenomenon of pulsar nulling, observed as the temporary inactivity of a pulsar, remains poorly understood both observationally and theoretically. Most observational studies that quantify nulling employ a variant of Ritchings algorithm, which can suffer significant biases for pulsars where the emission is weak. Using a more robust mixture model method, we study pulsar nulling in a sample of 22 recently discovered pulsars, for which we publish the nulling fractions for the first time. These data clearly demonstrate biases of the former approach and show how an otherwise nonnulling pulsar can be classified as having significant nulls. We show that the population-wide studies that find a positive correlation of nulling with pulsar period/characteristic age can similarly be biased because of the bias in estimating the nulling fraction. We use our probabilistic approach to find the evidence for periodicity in the nulls in a subset of three pulsars in our sample. In addition, we also provide improved timing parameters for 17 of the 22 pulsars that had no prior follow-up. 

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4. Independent Discovery of a Nulling Pulsar with Unusual Subpulse Drifting Properties with the Murchison Widefield Array

   https://doi.org/10.3847/1538-4357/ac75bc  

   McSweeney, Samuel J.; Bhat, N. D. Ramesh; Swainston, Nicholas A.; Smith, Keegan R.; Kudale, Sanjay; Hancock, Paul; Straten, Willem van; Dai, Shi; Shannon, Ryan M.; Tingay, Steven J.; et al (July 2022, The Astrophysical Journal)

   Abstract We report the independent discovery of PSR J0026-1955 with the Murchison Widefield Array (MWA) in the ongoing Southern-sky MWA Rapid Two-metre pulsar survey. J0026-1955 has a period of ∼1.306 s, a dispersion measure of ∼20.869 pc cm⁻³, and a nulling fraction of ∼77%. This pulsar highlights the advantages of the survey's long dwell times (∼80 minutes), which, when fully searched, will be sensitive to the expected population of similarly bright, intermittent pulsars with long nulls. A single-pulse analysis in the MWA's 140–170 MHz band also reveals a complex subpulse drifting behavior, including both rapid changes of the drift rate characteristic of mode switching pulsars, as well as a slow, consistent evolution of the drift rate within modes. In some longer drift sequences, interruptions in the otherwise smooth drift rate evolution occur preferentially at a particular phase, typically lasting a few pulses. These properties make this pulsar an ideal test bed for prevailing models of drifting behavior such as the carousel model. 

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5. Discovery of a Young, Highly Scattered Pulsar PSR J1032-5804 with the Australian Square Kilometre Array Pathfinder

   https://doi.org/10.3847/1538-4357/ad0fe8  

   Wang, Ziteng; Kaplan, David L.; Sengar, Rahul; Lenc, Emil; Zic, Andrew; Anumarlapudi, Akash; Gaensler, B. M.; Hurley-Walker, Natasha; Murphy, Tara; Wang, Yuanming (January 2024, The Astrophysical Journal)

   Abstract We report the discovery of a young, highly scattered pulsar in a search for highly circularly polarized radio sources as part of the Australian Square Kilometre Array Pathfinder Variables and Slow Transients survey. In follow-up observations with the Parkes radio telescope, Murriyang, we identified PSR J1032−5804 and measured a period of 78.7 ms, a dispersion measure of 819 ± 4 pc cm⁻³, a rotation measure of −2000 ± 1 rad m⁻², and a characteristic age of 34.6 kyr. We found a pulse scattering timescale at 3 GHz of ∼22 ms, implying a timescale at 1 GHz of ∼3845 ms, which is the third most scattered pulsar known and explains its nondetection in previous pulsar surveys. We discuss the identification of a possible pulsar wind nebula and supernova remnant in the pulsar’s local environment by analyzing the pulsar spectral energy distribution and the surrounding extended emission from multiwavelength images. Our result highlights the possibility of identifying extremely scattered pulsars from radio continuum images. Ongoing and future large-scale radio continuum surveys will offer us an unprecedented opportunity to find more extreme pulsars (e.g., highly scattered, highly intermittent, and highly accelerated), which will enhance our understanding of the characteristics of pulsars and the interstellar medium. 

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