Probing the neutron star interior and the Equation of State of cold dense matter with the SKA

With an average density higher than the nuclear density, neutron stars (NS) provide a unique test-ground for nuclear physics, quantum chromodynamics (QCD), and nuclear superfluidity. Determination of the fundamental interactions that govern matter under such extreme conditions is one of the major unsolved problems of modern physics, and -- since it is impossible to replicate these conditions on Earth -- a major scientific motivation for SKA. The most stringent observational constraints come from measurements of NS bulk properties: each model for the microscopic behaviour of matter predicts a specific density-pressure relation (its `Equation of state', EOS). This generates a unique mass-radius relation which predicts a characteristic radius for a large range of masses and a maximum mass above which NS collapse to black holes. It also uniquely predicts other bulk quantities, like maximum spin frequency and moment of inertia. The SKA, in Phase 1 and particularly in Phase 2 will, thanks to the exquisite timing precision enabled by its raw sensitivity, and surveys that dramatically increase the number of sources: 1) Provide many more precise NS mass measurements (high mass NS measurements are particularly important for ruling out EOS models); 2) Allow the measurement of the NS moment of inertia in highly relativistic binaries such as the Double Pulsar; 3) Greatly increase the number of fast-spinning NS, with the potential discovery of spin frequencies above those allowed by some EOS models; 4) Improve our knowledge of new classes of binary pulsars such as black widows and redbacks (which may be massive as a class) through sensitive broad-band radio observations; and 5) Improve our understanding of dense matter superfluidity and the state of matter in the interior through the study of rotational glitches, provided that an ad-hoc campaign is developed.Comment: 22 pages, 8 figures, to be published in: "Advancing Astrophysics with the Square Kilometre Array", Proceedings of Science, PoS(AASKA14)04

Pinning down the superfluid and nuclear equation of state and measuring neutron star mass using pulsar glitches

Pulsars are rotating neutron stars that are renowned for their timing precision, although glitches can interrupt the regular timing behavior when these stars are young. Glitches are thought to be caused by interactions between normal and superfluid matter in the star. We update our recent work on a new technique using pulsar glitch data to constrain superfluid and nuclear equation of state models, demonstrating how current and future astronomy telescopes can probe fundamental physics such as superfluidity near nuclear saturation and matter at supranuclear densities. Unlike traditional methods of measuring a star’s mass by its gravitational effect on another object, our technique relies on nuclear physics knowledge and therefore allows measurement of the mass of pulsars which are in isolatio

Comparative evaluation of container handling systems in a container terminal

160 σ.In the present diploma thesis, a detailed presentation of the container transport method is carried out, including the cargo units, the container vessels, and the equipment and vehicles utilized in container handling at terminals, focusing upon the analytic description of various type of equipment and their technical and operational characteristics. The container handling and transfer methods, cited in the bibliography are examined, in order to compare the alternatives and derive the parameters for rating them for optimal port terminal usage.Δανάη-Κανέλλα Αντωνοπούλο

Pinning down the superfluid and measuring masses using pulsar glitches

Pulsars are known for their superb timing precision, although glitches can interrupt the regular timing behavior when the stars are young. These glitches are thought to be caused by interactions between normal and superfluid matter in the crust of the star. However, glitching pulsars such as Vela have been shown to require a superfluid reservoir that greatly exceeds that available in the crust. We examine a model in which glitches tap the superfluid in the core. We test a variety of theoretical superfluid models against the most recent glitch data and find that only one model can successfully explain up to 45 years of observational data. We develop a new technique for combining radio and X-ray data to measure pulsar masses, thereby demonstrating how current and future telescopes can probe fundamental physics such as superfluidity near nuclear saturatio

[Editorial] CompOSE: a repository for neutron star equations of state and transport properties

The CompOSE Topical Issue is a compendium of several works on neutron star equations of state (EoS) and transport properties related to the online repository CompOSE (CompStar Online Supernovae Equations of State).The Guest Editors of the CompOSE Topical Issue are grateful for the support of the COST Action CA16214 PHAROS (The multi-messenger physics and astrophysics of neutron stars), which permitted the community involved in the process to complete the Topical Issue and set the working bases for future developments in the fields. The COST Action CA16214 PHAROS ran from November 2017 to May 2022.Peer reviewe

The Jodrell Bank Glitch Catalogue: 106 new rotational glitches in 70 pulsars

Pulsar glitches are rapid spin-up events that occur in the rotation of neutron stars, providing a valuable probe into the physics of the interiors of these objects. Long-term monitoring of a large number of pulsars facilitates the detection of glitches and the robust measurements of their parameters. The Jodrell Bank pulsar timing programme regularly monitors more than 800 radio pulsars and has accrued, in some cases, over 50 years of timing history on individual objects. In this paper we present 106 new glitches in 70 radio pulsars as observed up to the end of 2018. For 70% of these pulsars, the event we report is its only known glitch. For each new glitch we provide measurements of its epoch, amplitude and any detected changes to the spin-down rate of the star. Combining these new glitches with those listed in the Jodrell Bank glitch catalogue we analyse a total sample of 543 glitches in 178 pulsars. We model the distribution of glitch amplitudes and spin-down rate changes using a mixture of two Gaussian components. We corroborate the known dependence of glitch rate and activity on pulsar spin-down rates and characteristic ages, and show that younger pulsars tend to exhibit larger glitches. Pulsars whose spin-down rates between $10^{-14}$ Hz s$^{-1}$ and $10^{-10.5}$ Hz s$^{-1}$ show a mean reversal of 1.8% of their spin-down as a consequence of glitches. Our results are qualitatively consistent with the superfluid vortex unpinning models of pulsar glitches.Comment: 14 pages, 17 figures, 3 tables. Accepted for publication in MNRA

Return of the Big Glitcher: NICER timing and glitches of PSR J0537−6910

International audiencePSR J0537−6910, also known as the Big Glitcher, is the most prolific glitching pulsar known, and its spin-induced pulsations are only detectable in X-ray. We present results from analysis of 2.7 yr of NICER timing observations, from 2017 August to 2020 April. We obtain a rotation phase-connected timing model for the entire time span, which overlaps with the third observing run of LIGO/Virgo, thus enabling the most sensitive gravitational wave searches of this potentially strong gravitational wave-emitting pulsar. We find that the short-term braking index between glitches decreases towards a value of 7 or lower at longer times since the preceding glitch. By combining NICER and RXTE data, we measure a long-term braking index n = −1.25 ± 0.01. Our analysis reveals eight new glitches, the first detected since 2011, near the end of RXTE, with a total NICER and RXTE glitch activity of |$8.88\times 10^{-7}\, \mathrm{yr^{-1}}$|⁠. The new glitches follow the seemingly unique time-to-next-glitch–glitch-size correlation established previously using RXTE data, with a slope of |$5\, \rm {d} \, \mu \mathrm{Hz}^{-1}$|⁠. For one glitch around which NICER observes 2 d on either side, we search for but do not see clear evidence of spectral nor pulse profile changes that may be associated with the glitch

Solar photocatalytic decomposition of ethyl paraben in zinc oxide suspensions

Summarization: The photocatalytic degradation of ethyl paraben (EP) in zinc oxide (ZnO) suspensions under simulated solar radiation was investigated. The effect of EP concentration (500–1500 μg/L), ZnO concentration (100–500 mg/L), reaction time (3–9 min), initial pH (3–9), light intensity (7.3 10−7–1.1 10−6 einstein/(L.s)) and the water matrix (0–10 mg/L of humic acid) on degradation was evaluated implementing a factorial design methodology. Of the six variables tested, EP concentration, ZnO concentration, reaction time and the water matrix were found to be statistically significant variables, and also important was the second order interaction of EP concentration with reaction time. With the exception of the water matrix, all other effects were positive with respect to the concentration of EP removed. Experiments at increased EP concentration (20 mg/L) were performed to identify transformation products (TPs) and assess the extent of mineralization. LC-TOF-MS analysis revealed the formation of seven early-stage TPs through hydroxylation and dealkylation reactions and a plausible reaction pathway was proposed. Besides the identified TPs, other unidentified TPs were also formed as has been verified measuring the extent of mineralization and performing a carbon balance in the liquid phase. EP at 20 mg/L exhibited mild estrogenic activity, which was partially removed upon oxidation. The stability of ZnO was evaluated measuring the extent of zinc leaching, which was just 1.5%; moreover, ZnO was found to be more active than reference P25 TiO2 for EP degradation and mineralization.Presented on: Catalysis Toda