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Several sources of repeating coherent bursts of radio emission with periods of many minutes have now been reported in the literature. These 'ultralong period' (ULP) sources have no clear multiwavelength counterparts and challenge canonical pulsar emission models, leading to debate regarding their nature. In this work, we report the discovery of a bright, highly polarized burst of radio emission at low Galactic latitude as part of a wide-field survey for transient and variable radio sources. ASKAP J175534.9 |$-$| 252749.1 does not appear to repeat, with only a single intense two-minute |$\sim$| 200-mJy burst detected from 60 h of observations. The burst morphology and polarization properties are comparable to those of classical pulsars but the duration is more than one hundred times longer, analogous to ULPs. Combined with the existing ULP population, this suggests that these sources have a strong Galactic latitude dependence and hints at an unexplored population of transient and variable radio sources in the thin disc of the Milky Way. The resemblance of this burst with both ULPs and pulsars calls for a unified coherent emission model for objects with spin periods from milliseconds to tens of minutes. However, whether or not these are all neutron stars or have the same underlying power source remains open for debate. [ABSTRACT FROM AUTHOR]

Fast radio bursts (FRBs) are short-time-scale transients of extragalactic origin. The number of detected FRBs has grown dramatically since their serendipitous discovery from archival data. Some FRBs have also been seen to repeat. The polarimetric properties of repeating FRBs show diverse behaviour and, at times, extreme polarimetric morphology, suggesting a complex magneto-ionic circumburst environment for this class of FRB. The polarimetric properties such as circular polarization behaviour of FRBs are crucial for understanding their surrounding magnetic-ionic environment. The circular polarization previously observed in some of the repeating FRB sources has been attributed to propagation effects such as generalized Faraday rotation (GFR), where conversion from linear to circular polarization occurs due to the non-circular modes of transmission in relativistic plasma. The discovery burst from the repeating FRB 20180301A showed significant frequency-dependent circular polarization behaviour, which was initially speculated to be instrumental due to a sidelobe detection. Here, we revisit the properties given the subsequent interferometric localization of the burst, which indicates that the burst was detected in the primary beam of the Parkes/Murriyang 20-cm multibeam receiver. We develop a Bayesian Stokes-Q, U, and V fit method to model the GFR effect, which is independent of the total polarized flux parameter. Using the GFR model we show that the rotation measure (RM) estimated is two orders of magnitude smaller and opposite sign (⁠|$\sim$| 28 rad m |$^{-2}$|⁠) than the previously reported value. We interpret the implication of the circular polarization on its local magnetic environment and reinterpret its long-term temporal evolution in RM. [ABSTRACT FROM AUTHOR]

PSR J1227−6208 is a 34.53-ms recycled pulsar with a massive companion. This system has long been suspected to belong to the emerging class of massive recycled pulsar−ONeMg white dwarf systems such as PSR J2222−0137, PSR J1528−3146, and J1439−5501. Here, we present an updated emission and timing analysis with more than 11 years of combined Parkes and MeerKAT data, including 19 hours of high-frequency data from the newly installed MeerKAT S-band receivers. We measure a scattering timescale of 1.22 ms at 1 GHz with a flat scattering index of 3.33 < β < 3.62, and a mean flux density of 0.53 − 0.62 mJy at 1 GHz with a steep spectral index of 2.06 < α < 2.35. Around 15% of the emission is linearly and circularly polarised, but the polarisation angle does not follow the rotating vector model. Thanks to the sensitivity of MeerKAT, we successfully measure a rate of periastron advance of ω7 = 0.0171(11) deg yr−1, and a Shapiro delay with an orthometric amplitude of h3 = 3.6 ± 0.5 μs and an orthometric ratio of ς = 0.85 ± 0.05. The main source of uncertainty in our timing analysis is chromatic correlated dispersion measure noise, which we model as a power law in the Fourier space thanks to the large frequency coverage provided by the Parkes UWL receiver. Assuming general relativity and accounting for the measurements across all the implemented timing noise models, the total mass, companion mass, pulsar mass, and inclination angle are constrained at 2.3 < Mt/M⊙ < 3.2, 1.21 < Mc/M⊙ < 1.47, 1.16 < Mp/M⊙ < 1.69, and 77.5 < i/deg < 80.3. We also constrain the longitude of ascending node to either Ωa = 266 ± 78 deg or Ωa = 86 ± 78 deg. We argue against a neutron star nature of the companion based on the very low orbital eccentric of the system (e = 1.15 × 10−3), and instead classify the companion of PSR J1227−6208 as a rare, massive ONeMg white dwarf close to the Chandrasekhar limit. [ABSTRACT FROM AUTHOR]

A recent measurement of the proper motion of PSR J0908–4913 shows that it is a fast-moving object at a distance of some 3 kpc. Here, we present evidence that the pulsar is located at the edge of a previously unknown, filled-centre supernova remnant (SNR), G270.4–1.0. The velocity vector of the pulsar points directly away from the centre of the remnant. The putative association of the pulsar with SNR G270.4–1.0 implies the pulsar is ∼12 kyr old, significantly less than its characteristic age of 110 kyr. We show that the rotation axis of the pulsar points in the direction of the proper motion. Rotation measure and dispersion measure variations are seen over time, likely indicating the pulsar is passing behind a filament of the remnant. [ABSTRACT FROM AUTHOR]