Quadrupole moment of a magnetically confined mountain on an accreting neutron star: effect of the equation of state

Magnetically confined mountains on accreting neutron stars are promising sources of continuous-wave gravitational radiation and are currently the targets of directed searches with long-baseline detectors like the Laser Interferometer Gravitational Wave Observatory (LIGO). In this paper, previous ideal-magnetohydrodynamic models of isothermal mountains are generalized to a range of physically motivated, adiabatic equations of state. It is found that the mass ellipticity drops substantially, from \epsilon ~ 3e-4 (isothermal) to \epsilon ~ 9e-7 (non-relativistic degenerate neutrons), 6e-8 (relativistic degenerate electrons) and 1e-8 (non-relativistic degenerate electrons) (assuming a magnetic field of 3e12 G at birth). The characteristic mass M_{c} at which the magnetic dipole moment halves from its initial value is also modified, from M_{c}/M_{\sun} ~ 5e-4 (isothermal) to M_{c}/M_{\sun} ~ 2e-6, 1e-7, and 3e-8 for the above three equations of state, respectively. Similar results are obtained for a realistic, piecewise-polytropic nuclear equation of state. The adiabatic models are consistent with current LIGO upper limits, unlike the isothermal models. Updated estimates of gravitational-wave detectability are made. Monte Carlo simulations of the spin distribution of accreting millisecond pulsars including gravitational-wave stalling agree better with observations for certain adiabatic equations of state, implying that X-ray spin measurements can probe the equation of state when coupled with magnetic mountain models.Comment: 20 pages, 15 figures, to be published in MNRA

Practical Aspects of the Implementation of International Financial Reporting Standards and Accounting Policies in Business Structures

Ukraine’s membership in the European Union envisages the introduction of and compliance with the requirements and norms of European law, accompanied by reforms in almost all sectors of the Ukrainian economy including accounting. The main objective of the accounting reform is to bring the national accounting system in line with the requirements of the market economy and international accounting and reporting standards. The aim of the article is to study practical aspects of implementing International Financial Reporting Standards (IFRS) and accounting policies in business structures, with regard to national accounting features, in order to assess their impact on the performance. The article considers advantages of domestic enterprises in preparing reports in accordance with International Financial Reporting Standards, reveals problems associated with the application of the principles and requirements of IFRS, and describes the specifics of the transition of domestic enterprises to IFRS with regard to national peculiarities. The practical aspects of the implementation of IFRS and the principles of accounting policies in business structures are studied, taking into consideration national accounting features, in order to assess their impact on business entities’ performance. The influence of the transition to tax obligations and tax consequences for enterprises in reporting under international standards is calculated. Based on the results of the study, it is concluded that the transformational differences at the stage of transition to IFRS become neutral before taxation; business owners, investors and lenders receive high-quality financial statements to make informed and sound management decisions

Provision of Accounting Services on the Bases of Outsourcing in the Current Conditions

The article explores the main aspects of the introduction and use of accounting on the basis of outsourcing. It is noted that the purpose of the article is to examine and evaluate the current state of accounting services on the basis of outsourcing, as well as to determine the efficiency, feasibility and impact of its application on the activities of enterprises, in particular, in the context of reducing the company’s costs. The concepts of outsourcing and accounting outsourcing, their types, goals and causes are distinguished. Several factors for the selection of outsourcing companies that should be taken into attention when choosing a business entity for conduct of accounting. A separate situation on the calculation of economic efficiency from the use of accounting outsourcing is considered, on the example of the presented enterprise it is proved that its use is efficient and economically substantiated. It is determined that use of accounting outsourcing appears the most optimal for small and medium-sized enterprises. It is noted that outsourcing of accounting services allows not only to focus on a reliable reflection of the facts of economic activity of companies, but also on the rational use of their resources. A number of advantages and disadvantages of accounting at the enterprise for various forms of accounting organization are identified and compared. The article outlines a number of problems faced by a modern enterprise when choosing the use of accounting services on the basis of outsourcing and which slow down the application of outsourcing practice at such enterprises. The financial benefits of a domestic enterprise from the use of outsourcing of accounting services are examined, appropriate generalizations, conclusions and proposals are made. The need for further improvement is substantiated and the prospects for using outsourcing of accounting services in the work of domestic enterprises are determined

Gravitational-wave spin-down and stalling lower limits on the electrical resistivity of the accreted mountain in a millisecond pulsar

The electrical resistivity of the accreted mountain in a millisecond pulsar is limited by the observed spin-down rate of binary radio millisecond pulsars (BRMSPs) and the spins and X-ray fluxes of accreting millisecond pulsars (AMSPs). We find $\eta \ge 10^{-28}\,\mathrm{s}\, (\tau_\mathrm{SD}/1\,\mathrm{Gyr})^{-0.8}$ (where $\tau_\mathrm{SD}$ is the spin-down age) for BRMSPs and $\eta \ge 10^{-25}\,\mathrm{s}\,(\dot{M}_\mathrm{a}/\dot{M}_\mathrm{E})^{0.6}$ (where $\dot{M}_\mathrm{a}$ and $\dot{M}_\mathrm{E}$ are the actual and Eddington accretion rates) for AMSPs. These limits are inferred assuming that the mountain attains a steady state, where matter diffuses resistively across magnetic flux surfaces but is replenished at an equal rate by infalling material. The mountain then relaxes further resistively after accretion ceases. The BRMSP spin-down limit approaches the theoretical electron-impurity resistivity at temperatures \ga 10^5 K for an impurity concentration of $\sim 0.1$, while the AMSP stalling limit falls two orders of magnitude below the theoretical electron-phonon resistivity for temperatures above $10^8$ K. Hence BRMSP observations are already challenging theoretical resistivity calculations in a useful way. Next-generation gravitational-wave interferometers will constrain $\eta$ at a level that will be competitive with electromagnetic observations.Comment: accepted for publication in ApJ

Gravitational waves from rapidly rotating neutron stars

Rapidly rotating neutron stars in Low Mass X-ray Binaries have been proposed as an interesting source of gravitational waves. In this chapter we present estimates of the gravitational wave emission for various scenarios, given the (electromagnetically) observed characteristics of these systems. First of all we focus on the r-mode instability and show that a 'minimal' neutron star model (which does not incorporate exotica in the core, dynamically important magnetic fields or superfluid degrees of freedom), is not consistent with observations. We then present estimates of both thermally induced and magnetically sustained mountains in the crust. In general magnetic mountains are likely to be detectable only if the buried magnetic field of the star is of the order of $B\approx 10^{12}$ G. In the thermal mountain case we find that gravitational wave emission from persistent systems may be detected by ground based interferometers. Finally we re-asses the idea that gravitational wave emission may be balancing the accretion torque in these systems, and show that in most cases the disc/magnetosphere interaction can account for the observed spin periods.Comment: To appear in 'Gravitational Waves Astrophysics: 3rd Session of the Sant Cugat Forum on Astrophysics, 2014', Editor: Carlos F. Sopuert

Gravitational waves from single neutron stars: an advanced detector era survey

With the doors beginning to swing open on the new gravitational wave astronomy, this review provides an up-to-date survey of the most important physical mechanisms that could lead to emission of potentially detectable gravitational radiation from isolated and accreting neutron stars. In particular we discuss the gravitational wave-driven instability and asteroseismology formalism of the f- and r-modes, the different ways that a neutron star could form and sustain a non-axisymmetric quadrupolar "mountain" deformation, the excitation of oscillations during magnetar flares and the possible gravitational wave signature of pulsar glitches. We focus on progress made in the recent years in each topic, make a fresh assessment of the gravitational wave detectability of each mechanism and, finally, highlight key problems and desiderata for future work.Comment: 39 pages, 12 figures, 2 tables. Chapter of the book "Physics and Astrophysics of Neutron Stars", NewCompStar COST Action 1304. Minor corrections to match published versio