bluuebunny/crossref_metadata_2025_split huggingface dataset:
Predictions of inverse Compton radiation from PSR B1259–63
Authors: Kirk J. G. , Ball Lewis , Skjæraasen O. 
Published: July 2016

Unpulsed high energy (TeV) emission has been detected from several isolated pulsars (Aharonian 1999) and presumably results from relativistic electrons accelerated at the termination shock of an MHD wind driven by the pulsar itself. These electrons inverse Compton scatter target photons from either the cosmic microwave background, or from their own synchrotron radiation.The rotation-powered binary pulsar PSR B1259–63 (Johnston et al. 1996) is also thought to drive an MHD wind, and the synchrotron radiation of electrons accelerated at its termination shock is probably the source of the unpulsed X-rays seen from this object by ROSAT, OSSE and ASCA (Tavani &amp; Arons 1997). Compared to the isolated pulsars, however, the the pulsar’s Be-star companion provides an energy density of target photons available for inverse Compton scattering which is some 11 orders of magnitude larger. Using delta-function approximations to the emissivities and a monochromatic approximation to the spectrum of the target photons, we modelled the observed X-ray synchrotron emission and predicted the TeV emission in a recent paper (Kirk et al. 1999). In this contribution we improve these calculations in two respects – by treating the target spectrum more precisely, as described in the companion paper (Ball &amp; Kirk 1999), and by relaxing the approximations made in the emissivities.
On the Nature of Radio Eclipsing
Authors: Istomin Ya. N. 
Published: July 2016

AbstractIt is shown that the phenomena of radio eclipsing can be explained by the linear mechanism of transformation of the transverse electromagnetic wave, propagating in the pulsar wind, into the plasma waves in the region of interaction of wind with a companion star atmosphere. The coefficient of the passingηdepends on the wave frequencyωby the exponential mannerη= exp{–const ·ω−1}. The estimated scale for the pulsar wind and star’s atmosphere density gradients are of the order of 100 meters. Such gradient can be obtained in the bow shock forming when the pulsar wind enters into the companion star atmosphere. Annihilation of the part of the wind’s positrons with the star’s electrons produces the electric current. This current generates the magnetic field from which the pulsar wind’s particles are reflected. The magnitude of the magnetic field in this shock of about several Gauss.
Pulsar Scintillation Studies and Structure of the Local Interstellar Medium
Authors: Bhat N. D. Ramesh , Gupta Yashwant , Rao A. Pramesh , Preethi P. B. 
Published: July 2016

AbstractResults from new observations of pulsars using the Ooty Radio Telescope (ORT) are used for investigating the structure of the Local Interstellar Medium (LISM). The observations show anomalous scintillation effects towards several nearby pulsars, and these are modeled in terms of large-scale spatial inhomogeneities in the distribution of plasma density fluctuations in the LISM. A 3-component model, where the Solar neighbourhood is surrounded by a shell of enhanced plasma turbulence, is proposed for the LISM. The inferred scattering structure is strikingly similar to the Local Bubble. Further, analysis based on recent scintillation measurements show evidence for enhanced scattering towards pulsars located in the general direction of the Loop I Superbubble. The model for the LISM has been further extended by incorporating the scattering due to turbulent plasma associated with Loop I.
A (new) Phenomenon in Pulsar Dynamic Spectra
Authors: Stinebring D. R. , Becker K. M. , Goodman J. E. Espinoza , Kramer M. A. , Sheckard J. L. , Cordes J. M. , Lazio T. J. 
Published: July 2016

AbstractSeveral studies in the last decade have explored dramatic instances of refractive fringing in dynamic spectra. We draw attention to a subtler but more widespread refractive effect: wisp-like structures extending (either linearly or with curvature) outward from the origin in the secondary spectrum plane. We have employed a simple pinhole screen simulation to investigate this phenomenon. It appears that the presence of one or more wisps in a secondary spectrum indicates a clump of scattering material that is significantly offset from the optical axis. Unlike the dramatic fringing events that have been investigated in the past, however, the interference that gives rise to a wisp is interference between rays within a scattering clump rather than between two major ray bundles. Furthermore, the scattering clump must be significantly elongated along the direction of pulsar motion. The range of fringe spacings that this produces, all with a similar slope in the secondary spectrum, gives rise to the linear extent of the wisp in the secondary spectrum.
Close Binaries with Two Compact Objects
Authors: Kalogera V. 
Published: July 2016

AbstractThe coalescence of close binary systems with two compact objects (neutron stars and black holes) are considered to be promising sources of gravitational waves for the currently built laser interferometers. Here, I review the current Galactic coalescence estimates derived both theoretically and empirically. I discuss the uncertainties involved as well as ways of obtaining an upper limit to the coalescence rate of two neutron stars.
Partially ionized layers of accreted envelopes of weakly and strongly magnetized neutron stars
Authors: Potekhin Alexander , Chabrier Gilles , Shibanov Yuri 
Published: July 2016

AbstractWe study equilibrium properties of partially ionized hydrogen atmospheres and subphotospheric layers of weakly (with magnetic fieldB≪ 109G) and strongly (B≫ 1010G) magnetized neutron stars. In both weak- and strong-field cases, the ionization degree, atomic occupation numbers, and equation of state are calculated. These results are used to calculate opacities of neutron-star atmospheres.
Kilohertz QPOs and general-relativistic orbital motion—a maximum likelihood test
Authors: Bulik Tomasz 
Published: July 2016

AbstractUsing the maximum likelihood method we show that the observed distribution of maximum frequencies of kilohertz quasi periodic oscillations (QPOs) in LMXBs agrees with the frequencies of orbital motion in the marginally stable orbit around compact objects with masses chosen randomly from some interval, which we find to be (1.55M⊙, 2.40M⊙) at the 99% confidence level. As this remarkable agreement with the expected mass range of neutron stars in LMXBs demonstrates, the assumption that the maximum-frequency QPOs occur in the marginally stable orbit is consistent with the current data set.
Effect of Photon Rocket in X-ray Binaries
Authors: Pal’shin V. D. , Tsygan A. I. 
Published: July 2016

AbstractIt is shown that X-ray binaries can be accelerated by their own radiation. It is possible if the magnetic field of a neutron star in a binary differs from the dipolar field. Asymmetric X-ray emission generated due to accretion of matter onto a neutron star surface creates an accelerating force. Its magnitude can be comparable or even larger than gravitational attraction of the binary to the Galaxy.
Are Pulsars Bare Strange Stars?
Authors: Xu R. X. , Qiao G. J. , Zhang B. 
Published: July 2016

AbstractIt is believed that pulsars are neutron stars or strange stars with crusts. However we suggest here that pulsars may bebare strange stars(i.e., strange stars without crust). Due to rapid rotation and strong emission, young strange stars produced in supernova explosions should be bare when they act as radio pulsars. Because of strong magnetic field,twopolar-crusts would shield the polar caps of an accreting strange star. Such a suggestion can be checked by further observations.
Anomalous X-ray pulsars and soft gamma-ray repeaters in supernova remnants
Authors: Gaensler B. M. 
Published: July 2016

AbstractI consider the state of play regarding associations of supernova remnants (SNRs) with anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs). The three AXP/SNR associations are convincing, and are consistent with AXPs being young, low-velocity neutron stars. The three SGR/SNR associations are far more likely to be chance superpositions, and rely on SGRs being high velocity (&gt;1000 km s−1) objects. These results imply either that AXPs evolve into SGRs, or that SGRs and AXPs represent different populations of object.
The Status of Pulsar Emission Theory
Authors: Melrose D.B. 
Published: July 2016

AbstractIt is argued that there is now a preferred pulsar radio emission mechanism, involving beam-driven Langmuir turbulence. A testable prediction is that, at least in a statistical sense, features in the spectra of pulsars should scale with the plasma frequency,υGJ, implied by the Goldreich-Julian number density.
Küstner’s Observations of 1884–85: the Turning Point in the Empirical Establishment of Polar Motion
Authors: Brosche P. 
Published: July 2016

AbstractSince Euler in 1765 predicted the possibility of polar motion, the search for an observational confirmation went on. While some indications were found before, the proof without doubt is generally attributed to Küstner. Ironically, the aim of Küstner’s precise observations of 1884–1885 in Berlin was another one, namely an improved value of the constant of aberration. Using the Horrebow-Talcott method, he could conclude that the latitude of Berlin had decreased significantly by 02 in about one year. His findings promoted the start of international cooperation to observe the polar motion. Measurements from Honolulu in 1891 exhibited the effect in counterphase, thus omitting the last chance for a local explanation.
Seth Carlo Chandler Jr.: The Discovery of Variation of Latitude
Authors: Carter M.S. , Carter W.E. 
Published: July 2016

AbstractIt took Seth Carlo Chandler Jr. just one year to discover the 14 month and annual components of the variation of latitude (polar motion) that had eluded the most talented astronomers for more than a century. He succeeded where those before him had failed because: he used a global set of observations that had been painstakingly collected by astronomers of many nationalities over more than 150 years; he ignored the common wisdom that unexpected annual variations in astronomical observations were always caused by temperature effects on instruments or atmospheric refraction anomalies; and he was not misled by the theory, which predicted that the Eulerian wobble must have a period of approximately 10 months. Chandler was a true amateur only in the sense that he pursued astronomy out of love, while making his living as an actuary. He began his scientific training at the youthful age of 15 under the tutelage of Benjamin Pierce, perhaps the greatest American mathematician of that time. He then became: a private assistant to Benjamin Apthorp Gould, Jr., an aide to Gould while employed by the US Coast Survey, and Assistant Editor to Gould for the Astronomical Journal. It would be impossible to understand and appreciate Chandler’s achievements without recognizing his relationship with Gould, his brilliant mentor and lifelong colleague — the man he once described as his “Magnus Apollo.”In 1901 Chandler announced that the 14 month motion was not a simple oscillation but was in itself a compound motion consisting of the previously discovered 428 day component, and a much smaller 436 day component, whose reality was “beyond reasonable doubt.” The beating of two such components would result in a rapid change in the phase and amplitude of the Chandler motion at intervals of about 80 years. If Chandler was correct, in about 2010, give or take perhaps five years, we should see the next occurrence of this phenomenon. With the International Earth Rotation Service in operation there should be no difficulty in detecting and quantifying such an event, very nearly one century after Chandler’s death.
Polar Motion — An Overview
Authors: McCarthy Dennis D. 
Published: July 2016

AbstractAfter one hundred years of intensive study, some aspects of polar motion remain poorly understood. This motion of the Earth’s axis of rotation with respect to its mantle and crust has been observed and studied since the creation of the International Latitude Service. Research has shown that the motion of the pole is quite complicated and distinguished by components over all time scales. Observationally, the secular, Chandler and annual components of polar motion are well documented, and various geophysical processes have been suggested as likely causes. Other components such as the approximately thirty-year motion, the high-frequency motion and the daily/sub-daily motion remain as subjects of extensive research.
IGS Combined and Contributed Earth Rotation Parameter Solutions
Authors: Kouba Jan , Beutler Gerhard , Rothacher Markus 
Published: July 2016

AbstractSince January 1995 the International GPS Service (IGS) has been combining and analyzing daily polar motion (PM) series, produced and submitted by seven IGS analysis centers (ACs) for the IGS Final orbit/clock combinations. Since June 30, 1996 the IGS Earth Rotation Parameter (ERP) series that accompany the IGS combined orbits, also include combined PM rates. Furthermore, since March 1997, the IGS LOD (Length of Day) solutions are based on separate combinations of AC LOD solutions calibrated and weighted according to the IERS Bulletin A definite values. Similar to AC orbit solutions, the PM solutions have improved considerably since 1995, so that currently the IGS combined and the best AC PM solutions are at or below the 0.1 mas precision level, although PM biases may exceed .1 mas. Comparisons of AC ERP and PM rate solutions with the IGS Final combined ERP series revealed signals with 7 and 14-day periods for some AC solutions.During 1998, the IGS Final and the best AC PM rate solutions compared with Atmospheric Angular Momentum (AAM) at 0.3 mas/day (rms) with an average correlation of about 0.8 and 0.6 for the PM x and PM y rate components. The correlation varied considerably with time and frequency, though significant correlation already started from 6-day periods and reaching maxima within 10 to 50 day period bands. Most of the remaining signal in the PM rate solutions could likely be accounted for by Ocean Angular Momentum (OAM) as seen from the comparisons of combined OAM and AAM with the IGS PM series during 1995 and early 1996 when also OAM data were made available. During this period the IGS PM rates agreed with the combined OAM + AAM series with 0.3 and 0.2 mas/day (rms) for the PM x and y components and with an average correlation of about 0.8 for both PM components.
A Mechanism of Variations of the Earth Rotation at Different Timescales
Authors: Barkin Yu. V. 
Published: July 2016

AbstractTo explain the observed effects in the Earth’s polar motion, a mechanism of the relative motion of the lower mantle and upper mantle with a boundary at 670 km of depth is proposed. According to the new approach, the Earth’s layers (including separate plates) are considered as nonspherical, heterogeneous celestial bodies, interacting with each other, with the Moon and the Sun and executing a wide spectrum of relative motions in different timescales. The small displacements of the centers of masses of the lower and upper mantles and their relative rotations have here a primary importance. These displacements display themselves at various time scales (from a few months to millions of years), and their manifestations are readily detected in the regularities of the distribution of geological structures as well as in many geodynamical processes. Important regularities of the ordered positions of the plate centers, of their triple junctions, hot spots, systems of fractures and cracks, geographic structures, fields of fossils, etc., are observed as consequences of certain displacements and inclined rotations (Barkin, 1999). At geological time intervals, the slow motion of the layers causes mutually correlated variations of the processes of rifting, spreading, subduction, regressions and transgressions of the sea, of the plate motion, formation and breakdown of super continents, etc. The motions and the accompanying tectonic mass redistribution cause variations of the components of the Earth’s inertia tensor and geopotential, which lead to variations of its diurnal rotation and polar motion. Explanation of the main properties of the perturbed Chandler polar motion has been done.
Excitation of the Chandler Wobble
Authors: Sidorenkov N.S. 
Published: July 2016

AbstractThe redistribution of air and water masses between the Pacific and Indian oceans during the El Niño/Southern oscillation (ENSO) changes the components of the Earth’s inertia tensor and shifts the position of the pole of the Earth’s rotation. The spectrum of the ENSO has components with periods of about 6, 3.6, 2.8, and 2.4 years. These periods are all the multiples of the Chandler period T = 1.2 yr. and the principal period of nutation 18.6 yr. A nonlinear model for the Chandler polar motion has been constructed based on this empirical fact. In this model, the ENSO excites the Chandler polar motion by acting on the Earth at the frequencies of combinative resonance. At the same time, the Chandler polar motion induces a polar tide in the atmosphere and the World Ocean, which orders the ENSO. As a result, the dominant components in the noise spectrum of the ENSO are those with the periods indicated above.
Dissipation and Ellipticity of the Chandler Wobble
Authors: Zhu Yaozhong , Gao Buxi 
Published: July 2016

AbstractThe Chandler wobble, one of the main feature of the Earth’s polar motion, is related to the properties of the mantle and liquid core as well as the mobility of the oceans. The equilibrium pole tide and mantle anelasticity both lengthen the Chandler period, moreover, the former imposes a slight ellipticity on the pole path, and the latter is responsible for the wobble energy dissipation. On the basis of the perturbation principles, we derive the theoretical Qω of the Chandler wobble, assuming that the wobble energy is totally dissipated within the mantle. The theoretical ellipticity and orientation of the semimajor axis of the Chandler wobble path for an anelastic Earth are given. Compared with the results for the elastic Earth, the effect of mantle anelasticity does not change the wobble ellipticity significantly, but slightly changes the orientation of the semimajor axis in the opposite direction. This paper has also proved that the effect of the Earth’s 3-axis feature on the wobble ellipticity is only about 19% of that of the equilibrium pole tide. Analysis of the polar motion data obtained by using modern geodetic techniques shows that the observed ellipticity and orientation of the semimajor axis agree with the theoretical results. We can deduce that the pole tide in the globe should be close to equilibrium.
Atmospheric Angular Momentum Variations and Diurnal Polar Motion
Authors: Zharov V.E. , Pasynok S.L. 
Published: July 2016

AbstractThe atmospheric effective angular momentum functions were used to study the excitation of the diurnal polar motion and nutation. The main effect on polar motion at the frequency of the S1 tide is up to 10 µas, and on the annual prograde nutation term is up to 0.1 mas. The atmosphere and viscosity of the outer core of the Earth were taken into account in calculating the transfer function.The atmosphere treated as a thin rotating layer gives two new eigen-modes or two new resonance frequencies in the Earth’s transfer function, and one of them is in the diurnal frequency band. Viscosity of the fluid outer core and choice of the Earth’s model change the nearly diurnal frequencies of the normal modes.
δ Scuti and RRs Type Variables: Theoretical Aspects
Authors: Petersen J. Otzen 
Published: July 2016

AbstractTheoretical problems in connection with δ Sct and RRs type variables are reviewed. All evidence shows that δ Sct stars are normal main-sequence or early post main-sequence stars. Results of linear stability analyses of δ Sct models agree well with observations, the presence of non-variables in the strip being understandable in terms of helium diffusion. Excitation of non-radial modes may also occur; comparison of observed multiple periodicities with the theoretically derived period patterns for radial and non-radial modes is discussed as a means to distinguish between these possibilities.It is not known whether RRs variables are of the same nature as δ Sct stars or in a late evolutionary state with low mass. RRs variables pulsate in radial modes, and recent linear stability analyses seem to agree well with observations for both normal and low masses. The reason for the difference in amplitude between RRs and δ Sct stars is not known. Non-linear investigations may provide important information in the near future. The observed period ratios of RRs variables indicate for most of the double mode pulsators a slight deficiency in heavy elements and a normal mass; but more detailed investigations of this problem are needed.
A Theory of the Trojan Asteroids
Authors: Garfinkel B. 
Published: July 2016

AbstractThe paper constructs a long-periodic solution for the case of 1:1 resonance in the restricted problem of three bodies. The polar coordinates r and 0 appear in the formHere λ is the mean synodic longitude, m is the small mass-parameter, k is the integer nearest to the ratio ω2/ω1 of the fundamental angular frequencies of the motion, and ck is a Fourier coefficient of a certain periodic function. Only elementary functions enter r(λ) and θ(λ), while the calculation of λ(t) requires the inversion of a hyper-elliptic integral t(λ).The internal resonant terms, carrying the critical divisor D, impart to the orbit an epicyclic character, in qualitative accord with the results of the numerical integration by Deprit and Henrard (1970). Our solution is valid except in the vicinity of the singularities at D = 0 and λ = 0.The presence of the resonant terms invalidates the Brown conjecture (1911) regarding the termination of the family of the tadpoleshaped orbits at the Lagrangian point L3. However, this conjecture holds for the mean orbits defined by r = r(λ), θ = θ(λ), and it also holds in the limit as m → 0.
A Second-Order Theory of the Galilean Satellites of Jupiter
Authors: Ferraz-Mello S. 
Published: July 2016

AbstractThe theory of the motion of the Galilean satellites of Jupiter is developed up to the second-order terms. The disturbing forces are those due to mutual attractions, to the non-symmetrical internal mass distribution of Jupiter and to the attraction from the Sun. The mean equator of Jupiter is taken as the reference plane and its motion is considered. The integration of the equations is performed. The geometric equations are solved for the case in which the amplitude of libration is zero. The perturbation method is shortly commented on the grounds of some recent advances in non-linear mechanics.In a previous paper (Ferraz-Mello, 1974) one perturbation theory has been constructed with special regard to the problem of the motion of the Galilean satellites of Jupiter. In this problem, the motions are nearly circular and coplanar; on the other hand the quasi-resonances lead to strong perturbations. The main characteristic of the theory is that it allows the main frequencies to be kept fixed from the earlier stages, and so, to have a purely trigonometric solution.
Some Considerations on the Theoretical Determination of the Potential by the Motion of Artificial Satellites in the Plane Case
Authors: Martinez-Benjamin J.J. 
Published: July 2016

AbstractWe consider the determination of the potential from the orbit of a satellite. The potential obtained is not unique because the satellite might describe the same orbit with different forces. The classical problem of determination of orbits has a unique solution, for given initial conditions. The problem is reduced to the planar case with a conservative force. The mathematical results depend on the arbitrary functions of the system of coordinates used.