Transparent Helium in Stripped Envelope Supernovae

Using simple arguments based on photometric light curves and velocity evolution, we propose that some stripped envelope supernovae (SNe) show signs that a significant fraction of their helium is effectively transparent. The main pieces of evidence are the relatively low velocities with little velocity evolution, as are expected deep inside an exploding star, along with temperatures that are too low to ionize helium. This means that the helium should not contribute to the shaping of the main SN light curve, and thus the total helium mass may be difficult to measure from simple light curve modeling. Conversely, such modeling may be more useful for constraining the mass of the carbon/oxygen core of the SN progenitor. Other stripped envelope SNe show higher velocities and larger velocity gradients, which require an additional opacity source (perhaps the mixing of heavier elements or radioactive nickel) to prevent the helium from being transparent. We discuss ways in which similar analysis can provide insights into the differences and similarities between SNe Ib and Ic, which will lead to a better understanding of their respective formation mechanisms.Comment: Revised version accepted for publication in The Astrophysical Journal Letters, 4 pages, 4 figure

Exploring the Potential Diversity of Early Type Ia Supernova Light Curves

During the first several days after explosion, Type Ia supernova light curves probe the outer layers of the exploding star and therefore provide important clues for identifying their progenitors. We investigate how both the shallow $^{56}$Ni distribution and the presence of circumstellar material shape these early light curves. This is performed using a series of numerical experiments with parameterized properties for systematic exploration. Although not all of the considered models may be realized in nature (and indeed there are arguments why some of them should not occur), the spirit of this work is to provide a broader exploration of the diversity of possibilities. We find that shallower $^{56}$Ni leads to steeper, bluer light curves. Differences in the shape of the rise can introduce errors in estimating the explosion time and thus impact efforts to infer upper limits on the progenitor or companion radius from a lack of observed shock cooling emission. Circumstellar material can lead to significant luminosity during the first few days, but its presence can be difficult to identify depending on the degree of nickel mixing. In some cases, the hot emission of circumstellar material may even lead to a signature similar to interaction with a companion, and thus in the future additional diagnostics should be gathered for properly assessing early light curves.Comment: Revised version with additional figures and discussions. 8 pages, 15 figures, accepted for publication in The Astrophysical Journa

General Relativistic Magnetospheres of Slowly Rotating and Oscillating Magnetized Neutron Stars

We study the magnetosphere of a slowly rotating magnetized neutron star subject to toroidal oscillations in the relativistic regime. Under the assumption of a zero inclination angle between the magnetic moment and the angular momentum of the star, we analyze the Goldreich-Julian charge density and derive a second-order differential equation for the electrostatic potential. The analytical solution of this equation in the polar cap region of the magnetosphere shows the modification induced by stellar toroidal oscillations on the accelerating electric field and on the charge density. We also find that, after decomposing the oscillation velocity in terms of spherical harmonics, the first few modes with $m=0,1$ are responsible for energy losses that are almost linearly dependent on the amplitude of the oscillation and that, for the mode $(l,m)=(2,1)$, can be a factor $\sim8$ larger than the rotational energy losses, even for a velocity oscillation amplitude at the star surface as small as $\eta=0.05 \ \Omega \ R$. The results obtained in this paper clarify the extent to which stellar oscillations are reflected in the time variation of the physical properties at the surface of the rotating neutron star, mainly by showing the existence of a relation between $P\dot{P}$ and the oscillation amplitude. Finally, we propose a qualitative model for the explanation of the phenomenology of intermittent pulsars in terms of stellar oscillations that are periodically excited by star glitches.Comment: 13 pages, 4 figures, submitted to MNRA

Explaining the subpulse drift velocity of pulsar magnetosphere within the space-charge limited flow model

We try to explain the subpulse drift phenomena adopting the space-charge limited flow (SCLF) model and comparing the plasma drift velocity in the inner region of pulsar magnetospheres with the observed velocity of drifting subpulses. We apply the approach described in a recent paper of van Leeuwen & Timokhin (2012), where it was shown that the standard estimation of the subpulse drift velocity through the total value of the scalar potential drop in the inner gap gives inaccurate results, while the exact expression relating the drift velocity to the gradient of the scalar potential should be used instead. After considering a selected sample of sources taken from the catalog of Weltevrede, Edwards & Stappers (2006) with coherently drifting subpulses and reasonably known observing geometry, we show that their subpulse drift velocities would correspond to the drift of the plasma located very close or above the pair formation front. Moreover, a detailed analysis of PSR B0826-34 and PSR B0818-41 reveals that the variation of the subpulse separation with the pulse longitude can be successfully explained by the dependence of the plasma drift velocity on the angular coordinates.Comment: 14 pages, 6 figures, 2 table

Модельний аспект оцінки ефективності організації управління та мотивації персоналу

This paper proposes methodological aspects of evaluation of organization efficiency of personnel management and motivation on the bases of application of economic and mathematical tools by implementing a three-component algorithmic model. The structural divisions heads’ work effectiveness evaluation is carried out on the basis of econometric systems of structural equations that allow you to rank personality, communicative, innovative, social and corporate managers characteristics that have the greatest impact on the overall performance indicators of the bank staff among which are considered amount of attracted funds; assessment of employee's compliance with the standard; activity efficiency (number of contracts); contribution to development. The obtained modeling results confirm the hypothesis that structural unit managers need to work on the development of their communicative, innovative, personal and social characteristics. Models for analyzing the personnel motivation factors on the bases of the methodology of multivariate statistical factor analysis with initial list of 13 main indicators of staff motivation are proposed; as a result, we set up the aggregated factors that reflect the properties of several motivational components such as financial, social incentives and medical insurance for employees. The model for estimating influence of motivation factors on results of bank's activity on the bases of nonlinear econometric functions is constructed. The regression equation of the motivation factors influence on the bank total profit is obtained. The proposed model toolkit for evaluation of efficiency of management and staff motivation will allow the bank's management to improve motivation and incentives mechanisms in order to raise efficiency of stuff productivity in direction of increasing bank profitability and competitiveness.У статті запропоновано методологічні аспекти оцінки ефективності організації управління персоналом та мотивації на основі застосування економіко-математичного інструментарію шляхом реалізації трьохкомпонентної алгоритмічної моделі. Здійснено оцінку ефективності праці керівників структурних підрозділів на основі економетричних систем структурних рівнянь, що дозволяють ранжувати особистісні, комунікативні, інноваційні, соціальні та корпоративні характеристики, які в найбільшій мірі впливають на загальні показники ефективності роботи персоналу банку, серед яких розглядаються обсяг залучених коштів; оцінка працівника щодо відповідності стандарту; ефективність діяльності (кількість контрактів); вклад у розвиток. Отримані результати підтверджують гіпотезу, що керівникам структурних підрозділів треба працювати над розвитком своїх комунікативних, інноваційних, особистих та соціальних характеристик. Запропоновані моделі аналізу факторів мотивації персоналу за методологією багатовимірного статистичного факторного аналізу на основі вихідного переліку з 13 основних показників мотивації персоналу, у результаті чого сформовані агреговані фактори, що відбивають властивості декількох мотиваційних компонентів, а саме: матеріального стимулювання робітників, соціального стимулювання та охорони здоров’я персоналу. Побудовано модель оцінки впливу факторів мотивації на результати діяльності банку на основі нелінійних економетричних функцій. Отримано регресійне рівняння впливу факторів мотивації на загальний прибуток банку.Запропонований модельний інструментарій оцінювання ефективності управління та мотивації персоналу дозволить керівництву банку вдосконалити механізми стимулювання та заохочення працівників з метою підвищення ефективності їх праці в напрямі підвищення прибутковості та конкурентоспроможності банку

Crystal structure and conductivity of bismuth-containing complex oxides

In the paper, a comprehensive systematic study of different classes of bismuth containing oxide compounds was carried out. The relationship between composition, temperature and concentration regions of existence of stable, specific structure and properties of solid solutions on the basis of vanadates, molybdates, niobates and bismuth was found. The general regularities of synthesis of solid solutions with different variants of solid-phase and soluble methods were determined. On this basis, the optimal conditions for obtaining single-phase materials were formulated. For the first time the temperature and concentration boundaries of the regions of homogeneity and areas of stable existence of polymorphic modifications of solid solutions were defined and/or refined. The structural parameters of the synthesized phases were determined. By the method of electrochemical impedance spectroscopy the nature and features of impedance spectra, the temperature and concentration dependences of electrical conductivity of ceramic materials based on bismuth containing complex oxides were identified

Preparation and characterization of Bi26–2xMn2xMo10O69-d and Bi26.4Mn0.6Mo10–2yMe2yO69-d(Me = V, Fe) solid solutions

Received: 06.06.2017; accepted: 23.06.2017; published: 14.07.2017.Single phase samples of bismuth molybdate, Bi26Mo10O69, doped with Mn on the bismuth sublattice and V, Fe on the molybdenum sublattice were found to crystallize in the triclinic Bi26Mo10O69 structure at low doping levels and in the monoclinic Bi26Mo10O69 structure - at higher dopant concentration. The assumption that all Mn ions have an oxidation state of +2 was confirmed by means of magnetic measurement results analysis using Curie-Weiss law. Conductivity was investigated using impedance spectroscopy. The conductivity of Bi26.4Mn0.6Mo9.6Fe0.4O69-d was 1.2*10-2 S*cm-1 at 973 K and 2.2*10-4 S*cm-1 at 623 K, and the conductivity of Bi26.4Mn0.6Mo9.2V0.8O69-d was 2.2*10-3 S*cm-1 at 973 K and 2.2*10-5 S*cm-1 at 623 K

Nonsingular electrodynamics of a rotating black hole moving in an asymptotically uniform magnetic test field

We extend the Wald solution to a black hole that is also moving at constant velocity. More specifically, we derive analytic solutions for the Maxwell equations for a rotating black hole moving at constant speed in an asymptotically uniform magnetic test field. By adopting Kerr-Schild coordinates we avoid singular behaviors at the horizon and obtain a complete description of the charge and current distributions in terms of the black-hole spin and velocity. Using this solution, we compute the energy losses expected when charged particles are accelerated along the magnetic field lines, improving previous estimates that had to cope with singular electromagnetic fields on the horizon. When used to approximate the emission from binary black holes in a uniform magnetic field, our estimates match reasonably well those from numerical-relativity calculations in the force-free approximation

NMR and LDA evidence for spiral magnetic order in the chain cuprate LiCu2O2

We report on {6,7}Li nuclear magnetic resonance measurements of the spin-chain compound LiCu2O2 in the paramagnetic and magnetically ordered states. Below T about 24 K the NMR lineshape presents a clear signature of incommensurate (IC) static modulation of the local magnetic field consistent with an IC spiral modulation of the magnetic moments. {7}Li NMR reveals strong phason-like dynamical fluctuations extending well below 24 K. We hypothesize that a series of phase transitions at 24.2, 22.5, and 9 K reflects a "Devil's staircase" type behavior generic for IC systems. LDA based calculations of exchange integrals reveal a large in-chain frustration leading to a magnetical spiral.Comment: 4 pages, 4 figure