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The Galactic magnetic field plays an important role in the evolution of the Galaxy, but its small-scale behaviour is still poorly known. It is not known whether the Galactic field permeates the halo of the Galaxy. By observing pulsars in the halo globular cluster 47 Tucanae, we have probed the Galactic magnetic field at arcsecond scales, discovering an unexpected large gradient in the component of the magnetic field parallel to the line of sight. This gradient is aligned with a direction perpendicular to the Galactic disk and could be explained by magnetic fields amplified to some 60 μG within the globular cluster. Such a scenario supports the existence of a magnetized outflow that extends from the Galactic disk to the halo and interacts with 47 Tucanae. Observations of the Faraday rotation towards pulsars in the halo globular cluster 47 Tucanae have been used to constrain the magnetic field strength in the Galactic halo, finding that it is unexpectedly strong.

Improving safety standards in advanced radiotherapy technologies, where historical experience is not sufficient due to innovation aspects, raises the need to perform studies using new tools that follow a holistic view of the process chain. Such studies are useful to identify additional critical elements compared to safety analyses carried out by classic tools. In this field, SAPERO (La SicurezzA del PazientE: tecniche avanzate ed innovative per la valutazione del rischio di eventi indesiderati all'interno del percorso assistenziale nel settore RadioterapicO) is a new assessment tool that allows to use integrated of Hierarchical Task Analysis (HTA); Failure Mode Effects and Criticality Analysis (FMECA); Cognitive Task Analysis (CTA); Human Error Assessment Reduction Technique (HEART). The methodological approaches have been suitably modified to address their operating in the medical sector under study. Some improvements have concerned the application of the fuzzy theory in FMECA and the use of a linguistic approach in HEART. In this paper, SAPERO application on a case study related to treatment procedures in helical tomotherapy performed at the radiotherapy department of ARNAS Civico hospital, Italy, is described. The results have allowed to provide suggestions aimed to improve the examined process.

Globular clusters may host intermediate mass black holes (IMBHs) at their centres. Here we propose a new method for their identification using millisecond pulsars (MSPs) as probes. We show that measuring the first (jerk) and second (jounce) derivatives of the accelerations of an ensemble of MSPs will let us infer the presence of an IMBH in a globular cluster better than measuring the sole accelerations. We test this concept by simulating a set of star clusters with and without a central IMBH to extract the distributions of the stellar jerks and jounces. We then apply this technique to the ensemble of MSPs in the Galactic globular cluster 47 Tucanae. Current timing observations are insufficient to constrain the presence of an IMBH and can only be used to pose upper limits on its mass. But, with few more years of observations it will be possible to test for the presence of a central IMBH with mass smaller than \\(\\sim\\) 1000 M\\(_{\\odot}\\). We conclude that jerks and jounces help significantly in reducing the upper limit of the mass of IMBHs in Galactic globular clusters.

Theoretical models suggest that intermediate mass black holes (IMBHs) may form and reside in the centers of globular clusters. IMBHs are still elusive to observations, but the accelerations of pulsars may bring along a unique fingerprint of their presence. In this work, we focus on the pulsars in the globular cluster M62. Using the new distance of M62 obtained from Gaia observations, we find that the measured pulsars' accelerations suggest a central excess of mass in the range [1200, 6000]\\(M_{\\odot}\\), corresponding to [0.2, 1] percent of the current total mass of the cluster. Our analysis can not unambiguously discriminate between an IMBH or a system of stellar mass dark remnants of comparable total mass.

Pulsar Timing Arrays search for nanohertz-frequency gravitational waves by regularly observing ensembles of millisecond pulsars over many years to look for correlated timing residuals. Recently the first evidence for a stochastic gravitational wave background has been presented by the major Arrays, with varying levels of significance (\\(\\sim\\)2-4\\(\\sigma\\)). In this paper we present the results of background searches with the MeerKAT Pulsar Timing Array. Although of limited duration (4.5 yr), the \\(\\sim\\) 250,000 arrival times with a median error of just \\(3 \\mu\\)s on 83 pulsars make it very sensitive to spatial correlations. Detection of a gravitational wave background requires careful modelling of noise processes to ensure that any correlations represent a fit to the underlying background and not other misspecified processes. Under different assumptions about noise processes we can produce either what appear to be compelling Hellings-Downs correlations of high significance (3-3.4\\(\\sigma\\)) with a spectrum close to that which is predicted, or surprisingly, under slightly different assumptions, ones that are insignificant. This appears to be related to the fact that many of the highest precision MeerKAT Pulsar Timing Array pulsars are in close proximity and dominate the detection statistics. The sky-averaged characteristic strain amplitude of the correlated signal in our most significant model is \\(h_{c, {\\rm yr}} = 7.5^{+0.8}_{-0.9} \\times 10^{-15}\\) measured at a spectral index of \\(\\alpha=-0.26\\), decreasing to \\(h_{c, {\\rm yr}} = 4.8^{+0.8}_{-0.9} \\times 10^{-15}\\) when assessed at the predicted \\(\\alpha=-2/3\\). These data will be valuable as the International Pulsar Timing Array project explores the significance of gravitational wave detections and their dependence on the assumed noise models.

In an accompanying publication, the MeerKAT Pulsar Timing Array (MPTA) collaboration reports tentative evidence for the presence of a stochastic gravitational-wave background, following observations of similar signals from the European and Indian Pulsar Timing Arrays, NANOGrav, the Parkes Pulsar Timing Array and the Chinese Pulsar Timing Array. If such a gravitational-wave background signal originates from a population of inspiraling supermassive black-hole binaries, the signal may be anisotropically distributed on the sky. In this Letter we evaluate the anisotropy of the MPTA signal using a spherical harmonic decomposition. We discuss complications arising from the covariance between pulsar pairs and regularisation of the Fisher matrix. Applying our method to the 4.5 yr dataset, we obtain two forms of sky maps for the three most sensitive MPTA frequency bins between 7 -21 nHz. Our \"clean maps'' estimate the distribution of gravitational-wave strain power with minimal assumptions. Our radiometer maps answer the question: is there a statistically significant point source? We find a noteworthy hotspot in the 7 nHz clean map with a \\(p\\)-factor of \\(p=0.015\\) (not including trial factors). Future observations are required to determine if this hotspot is of astrophysical origin.

PSR J2140\\(-\\)2311B is a 13-ms pulsar discovered in 2001 in a 7.8-hour Green Bank Telescope (GBT) observation of the core-collapsed globular cluster M30 and predicted to be in a highly eccentric binary orbit. This pulsar has eluded detection since then, therefore its precise orbital parameters have remained a mystery until now. In this work, we present the confirmation of this pulsar using observations taken with the UHF receivers of the MeerKAT telescope as part of the TRAPUM Large Survey Project. Taking advantage of the beamforming capability of our backends, we have localized it, placing it \\(1.2(1)^\\prime\\) from the cluster centre. Our observations have enabled the determination of its orbit: it is highly eccentric (\\(e = 0.879\\)) with an orbital period of \\(6.2\\) days. We also measured the rate of periastron advance, \\(\\dot{\\omega} = 0.078 \\pm 0.002\\, \\rm deg \\, yr^{-1}\\). Assuming that this effect is fully relativistic, general relativity provides an estimate of the total mass of the system, \\(M_{\\rm TOT} = 2.53 \\pm 0.08\\) M\\(_{\\odot}\\), consistent with the lightest double neutron star systems known. Combining this with the mass function of the system gives the pulsar and companion masses of \\(m_p < 1.43 \\, \\rm M_{\\odot}\\) and \\(m_c > 1.10 \\, \\rm M_{\\odot}\\) respectively. The massive, undetected companion could either be a massive WD or a NS. M30B likely formed as a result of a secondary exchange encounter. Future timing observations will allow the determination of a phase-coherent timing solution, vastly improving our uncertainty in \\(\\dot{\\omega}\\) and likely enabling the detection of additional relativistic effects which will determine \\(m_p\\) and \\(m_c\\).

PSR J0540\\(-\\)6919 is the second-most energetic radio pulsar known and resides in the Large Magellanic Cloud. Like the Crab pulsar it is observed to emit giant radio pulses (GPs). We used the newly-commissioned PTUSE instrument on the MeerKAT radio telescope to search for GPs across three observations. In a total integration time of 5.7 hrs we detected 865 pulses above our 7\\(\\sigma\\) threshold. With full polarisation information for a subset of the data, we estimated the Faraday rotation measure, \\(\\rm{RM}=-245.8 \\pm 1.0\\) rad m\\(^{-2}\\) toward the pulsar. The brightest of these pulses is \\(\\sim\\) 60% linearly polarised but the pulse-to-pulse variability in the polarisation fraction is significant. We find that the cumulative GP flux distribution follows a power law distribution with index \\(-2.75 \\pm 0.02\\). Although the detected GPs make up only \\(\\sim\\) 10% of the mean flux, their average pulse shape is indistinguishable from the integrated pulse profile, and we postulate that there is no underlying emission. The pulses are scattered at L-band frequencies with the brightest pulse exhibiting a scattering time-scale of \\(\\tau = 0.92 \\pm 0.02\\) ms at 1.2 GHz. We find several of the giants display very narrow-band \"flux knots\" similar to those seen in many Fast Radio Bursts, which we assert cannot be due to scintillation or plasma lensing. The GP time-of-arrival distribution is found to be Poissonian on all but the shortest time-scales where we find four GPs in six rotations, which if GPs are statistically independent is expected to occur in only 1 of 7000 observations equivalent to our data.

The Galactic magnetic field plays an important role in the evolution of the Galaxy, but its small-scale behaviour is still poorly known. It is also unknown whether it permeates the halo of the Galaxy or not. By using observations of pulsars in the halo globular cluster 47 Tucanae, we probed the Galactic magnetic field at arcsecond scales for the first time and discovered an unexpected large gradient in the component of the magnetic field parallel to the line of sight. This gradient is aligned with a direction perpendicular to the Galactic disk and could be explained by magnetic fields amplified to some 60 {\\mu}G within the globular cluster. This scenario supports the existence of a magnetized outflow that extends from the Galactic disk to the halo and interacts with the studied globular cluster.

Pulsar timing arrays are ensembles of regularly observed millisecond pulsars timed to high precision. Each pulsar in an array could be affected by a suite of noise processes, most of which are astrophysically motivated. Analysing them carefully can be used to understand these physical processes. However, the primary purpose of these experiments is to detect signals that are common to all pulsars, in particular signals associated with a stochastic gravitational wave background. To detect this, it is paramount to appropriately characterise other signals that may otherwise impact array sensitivity or cause a spurious detection. Here we describe the second data release and first detailed noise analysis of the pulsars in the MeerKAT Pulsar Timing Array, comprising high-cadence and high-precision observations of \\(83\\) millisecond pulsars over \\(4.5\\) years. We use this analysis to search for a common signal in the data, finding a process with an amplitude of \\(\\log_{10}\\mathrm{A_{CURN}} = -14.25^{+0.21}_{-0.36}\\) and spectral index \\(\\gamma_\\mathrm{CURN} = 3.60^{+1.31}_{-0.89}\\). Fixing the spectral index at the value predicted for a background produced by the inspiral of binary supermassive black holes, we measure the amplitude to be \\(\\log_{10}\\mathrm{A_{CURN}} = -14.28^{+0.21}_{-0.21}\\) at a significance expressed as a Bayes factor of \\(\\ln(\\mathcal{B}) = 4.46\\). Under both assumptions, the amplitude that we recover is larger than those reported by other PTA experiments. We use the results of this analysis to forecast our sensitivity to a gravitational wave background possessing the spectral properties of the common signal we have measured.