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Using MeerKAT, we have discovered three new millisecond pulsars (MSPs) in the bulge globular cluster M62: M62H, M62I, and M62J. All three are in binary systems, which means all ten known pulsars in the cluster are in binaries. M62H has a planetary-mass companion with a median mass Mc, med ∼ 3 MJ and a mean density of ρ ∼ 11 g cm−3. M62I has an orbital period of 0.51 d and a Mc, med ∼ 0.15 M⊙. Neither of these low-mass systems exhibit eclipses. M62J has only been detected in the two Ultra High Frequency band (816 MHz) observations with a flux density S816 = 0.08 mJy. The non-detection in the L-band (1284 MHz) indicates it has a relatively steep spectrum (β < −3.1). We also present 23-yr-long timing solutions obtained using data from the Parkes ‘Murriyang’, Effelsberg, and MeerKAT telescopes for the six previously known pulsars. For all these pulsars, we measured the second spin-period derivatives and the rate of change of orbital period caused by the gravitational field of the cluster, and their proper motions. From these measurements, we conclude that the pulsars’ maximum accelerations are consistent with the maximum cluster acceleration assuming a core-collapsed mass distribution. Studies of the eclipses of the redback M62B and the black widow M62E at four and two different frequency bands, respectively, reveal a frequency dependence with longer and asymmetric eclipses at lower frequencies. The presence of only binary MSPs in this cluster challenges models which suggest that the MSP population of core-collapsed clusters should be dominated by isolated MSPs.

 

Spider pulsars continue to provide promising candidates for neutron star mass measurements. Here we present the discovery of PSR J1910−5320, a new millisecond pulsar discovered in a MeerKAT observation of an unidentified Fermi-LAT gamma-ray source. This pulsar is coincident with a recently identified candidate redback binary, independently discovered through its periodic optical flux and radial velocity. New multicolour optical light curves obtained with ULTRACAM/New Technology Telescope in combination with MeerKAT timing and updated SOAR/Goodman spectroscopic radial velocity measurements allow a mass constraint for PSR J1910−5320. icarus optical light curve modelling, with streamlined radial velocity fitting, constrains the orbital inclination and companion velocity, unlocking the binary mass function given the precise radio ephemeris. Our modelling aims to unite the photometric and spectroscopic measurements available by fitting each simultaneously to the same underlying physical model, ensuring self-consistency. This targets centre-of-light radial velocity corrections necessitated by the irradiation endemic to spider systems. Depending on the gravity darkening prescription used, we find a moderate neutron star mass of either 1.6 ± 0.2 or 1.4 ± 0.2 M⊙. The companion mass of either 0.45 ± 0.04 or $0.43^{+0.04}_{-0.03}$M⊙ also further confirms PSR J1910−5320 as an irradiated redback spider pulsar.

 

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.

 

We present a sample of well-localized fast radio bursts (FRBs) discovered by the MeerTRAP project at the MeerKAT telescope in South Africa. We discovered the three FRBs in single coherent tied-array beams and localized them to an area of ∼1 arcmin2. We investigate their burst properties, scattering, repetition rates, and localizations in a multiwavelength context. FRB 20201211A shows hints of scatter broadening but is otherwise consistent with instrumental dispersion smearing. For FRB 20210202D, we discovered a faint post-cursor burst separated by ∼200 ms, suggesting a distinct burst component or a repeat pulse. We attempt to associate the FRBs with host galaxy candidates. For FRB 20210408H, we tentatively (0.35–0.53 probability) identify a compatible host at a redshift ∼0.5. Additionally, we analyse the MeerTRAP survey properties, such as the survey coverage, fluence completeness, and their implications for the FRB population. Based on the entire sample of 11 MeerTRAP FRBs discovered by the end of 2021, we estimate the FRB all-sky rates and their scaling with the fluence threshold. The inferred FRB all-sky rates at 1.28 GHz are $8.2_{-4.6}^{+8.0}$ and $2.1_{-1.1}^{+1.8} \times 10^3 \: \text{sky}^{-1} \: \text{d}^{-1}$ above 0.66 and 3.44 Jy ms for the coherent and incoherent surveys, respectively. The scaling between the MeerTRAP rates is flatter than at higher fluences at the 1.4σ level. There seems to be a deficit of low-fluence FRBs, suggesting a break or turn-over in the rate versus fluence relation below 2 Jy ms. We speculate on cosmological or progenitor-intrinsic origins. The cumulative source counts within our surveys appear consistent with the Euclidean scaling.

 

We present the discovery of FRB 20210410D with the MeerKAT radio interferometer in South Africa, as part of the MeerTRAP commensal project. FRB 20210410D has a dispersion measure DM = 578.78 ± 2 ${\rm pc \, cm^{-3}}$ and was localized to subarcsec precision in the 2 s images made from the correlation data products. The localization enabled the association of the FRB with an optical galaxy at z = 0.1415, which when combined with the DM places it above the 3σ scatter of the Macquart relation. We attribute the excess DM to the host galaxy after accounting for contributions from the Milky Way’s interstellar medium and halo, and the combined effects of the intergalactic medium and intervening galaxies. This is the first FRB that is not associated with a dwarf galaxy to exhibit a likely large host galaxy DM contribution. We do not detect any continuum radio emission at the FRB position or from the host galaxy down to a 3σ rms of 14.4 $\mu$Jy beam−1. The FRB has a scattering delay of $29.4^{+2.8}_{-2.7}$ ms at 1 GHz, and exhibits candidate subpulses in the spectrum, which hint at the possibility of it being a repeating FRB. Although not constraining, we note that this FRB has not been seen to repeat in 7.28 h at 1.3 GHz with MeerKAT, 3 h at 2.4 GHz with Murriyang, and 5.7 h at simultaneous 2.3 GHz and 8.4 GHz observations with the Deep Space Network. We encourage further follow-up to establish a possible repeating nature.

 

Galactic plane radio surveys play a key role in improving our understanding of a wide range of astrophysical phenomena. Performing such a survey using the latest interferometric telescopes produces large data rates necessitating a shift towards fully or quasi-real-time data analysis with data being stored for only the time required to process them. We present here the overview and set-up for the 3000-h Max-Planck-Institut für Radioastronomie (MPIfR)–MeerKAT Galactic Plane Survey (MMGPS). The survey is unique by operating in a commensal mode, addressing key science objectives of the survey including the discovery of new pulsars and transients and studies of Galactic magnetism, the interstellar medium and star formation rates. We explain the strategy coupled with the necessary hardware and software infrastructure needed for data reduction in the imaging, spectral, and time domains. We have so far discovered 78 new pulsars including 17 confirmed binary systems of which two are potential double neutron star systems. We have also developed an imaging pipeline sensitive to the order of a few tens of micro-Jansky ($\mu{\rm Jy}$) with a spatial resolution of a few arcseconds. Further science operations with an in-house built S-band receiver operating between 1.7 and 3.5 GHz are about to commence. Early spectral line commissioning observations conducted at S-band, targeting transitions of the key molecular gas tracer CH at 3.3 GHz already illustrate the spectroscopic capabilities of this instrument. These results lay a strong foundation for future surveys with telescopes like the Square Kilometre Array (SKA).

 

Abstract Reliable neutron star mass measurements are key to determining the equation of state of cold nuclear matter, but such measurements are rare. Black widows and redbacks are compact binaries consisting of millisecond pulsars and semi-degenerate companion stars. Spectroscopy of the optically bright companions can determine their radial velocities, providing inclination-dependent pulsar mass estimates. Although inclinations can be inferred from subtle features in optical light curves, such estimates may be systematically biased due to incomplete heating models and poorly understood variability. Using data from the Fermi Large Area Telescope, we have searched for gamma-ray eclipses from 49 spider systems, discovering significant eclipses in 7 systems, including the prototypical black widow PSR B1957+20. Gamma-ray eclipses require direct occultation of the pulsar by the companion, and so the detection, or significant exclusion, of a gamma-ray eclipse strictly limits the binary inclination angle, providing new robust, model-independent pulsar mass constraints. For PSR B1957+20, the eclipse implies a much lighter pulsar (1.81 ± 0.07 solar masses) than inferred from optical light curve modelling. 

The most massive globular cluster in our Galaxy, Omega Centauri, is an interesting target for pulsar searches, because of its multiple stellar populations and the intriguing possibility that it was once the nucleus of a galaxy that was absorbed into the Milky Way. The recent discoveries of pulsars in this globular cluster and their association with known X-ray sources was a hint that, given the large number of known X-ray sources, there is a much larger undiscovered pulsar population. We used the superior sensitivity of the MeerKAT radio telescope to search for pulsars in Omega Centauri. In this paper, we present some of the first results of this survey, including the discovery of 13 new pulsars; the total number of known pulsars in this cluster currently stands at 18. At least half of them are in binary systems and preliminary orbital constraints suggest that most of the binaries have light companions. We also discuss the ratio between isolated and binaries pulsars, and how they were formed in this cluster.

 

We present the polarization profiles of 22 pulsars in the globular cluster 47 Tucanae using observations from the MeerKAT radio telescope at UHF band (544–1088 MHz) and report precise values of dispersion measure (DM) and rotation measure (RM). We use these measurements to investigate the presence of turbulence in electron density and magnetic fields. The structure function of DM shows a break at ∼30 arcsec (∼0.6 pc at the distance of 47 Tucanae) that suggests the presence of turbulence in the gas in the cluster driven by the motion of wind-shedding stars. On the other hand, the structure function of RM does not show evidence of a break. This non-detection could be explained either by the limited number of pulsars or by the effects of the intervening gas in the Galaxy along the line of sight. Future pulsar discoveries in the cluster could help confirm the presence and localize the turbulence.

 

ABSTRACT We report observed and derived timing parameters for three millisecond pulsars (MSPs) from observations collected with the Parkes 64-m telescope, Murriyang. The pulsars were found during reprocessing of archival survey data by Mickaliger et al. One of the new pulsars (PSR J1546–5925) has a spin period P = 7.8 ms and is isolated. The other two (PSR J0921–5202 with P = 9.7 ms and PSR J1146–6610 with P = 3.7 ms) are in binary systems around low-mass (${\gt}0.2\, {\rm M}_{\odot }$) companions. Their respective orbital periods are 38.2 and 62.8 d. While PSR J0921–5202 has a low orbital eccentricity e = 1.3 × 10−5, in keeping with many other Galactic MSPs, PSR J1146–6610 has a significantly larger eccentricity, e = 7.4 × 10−3. This makes it a likely member of a group of eccentric MSP–helium white dwarf binary systems in the Galactic disc whose formation is poorly understood. Two of the pulsars are co-located with previously unidentified point sources discovered with the Fermi satellite’s Large Area Telescope, but no γ-ray pulsations have been detected, likely due to their low spin-down powers. We also show that, particularly in terms of orbital diversity, the current sample of MSPs is far from complete and is subject to a number of selection biases.