bluuebunny/crossref_metadata_2025_split huggingface dataset:
Detection of Pulsed X-ray Emission from The Fastest Millisecond Pulsar PSR B1937+21 with ASCA
Authors: Takahashi Motoki , Shibata Shinpei , Torii Ken’ichi , Saito Yoshitaka , Kawai Nobuyuki , Hirayama Masaharu , Dotani Tadayasu , Gunji Shuichi , Sakurai Hirohisa 
Published: July 2016

AbstractWe report the first detection of the pulsed X-ray emission from the fastest millisecond pulsar known PSR B1937+21 (P=1.558msec) with ASCA. The pulsar is detected as a point source above ∼ 1.7keV, with no nebulosity indicated. The source flux in the energy band 2–10keV is found to bef= 4.3 × 10−13erg s−1cm−2, which corresponds to the luminosity ofLx= 4πD2f≈ 6.6 × 1032(D/3.6kpc)2erg s−1, whereDis the distance, and correspond to ≈ 6 × 10−4of the rotation power of the pulsar. The pulsation is found at the period predicted by the radio ephemerides with very narrow primary peaks, the width of which is about 1/16 phase ≈ 100μs near the time resolution limit (61μs) of the observation. The pulsed luminosity within the primary peak (1/16 phase interval) is found to befp= 4.0 × 10−12erg s−1cm−2. Although there may be a secondary peak, its statistical significance is too low to identify. Spectra of the whole source region and the primary peak are fitted by power law models to give photon indices of about unity for both.
Gamma Ray Pulsar Luminosities
Authors: McLaughlin Maura , Cordes James 
Published: July 2016

AbstractWe apply a likelihood analysis to pulsar detections, pulsar upper limits, and diffuse background measurements from the OSSE and EGRET instruments to constrain theγ-rays pulsar luminosity law. We find a steeper dependence on period and magnetic field at OSSE than at EGRET energies. We also find that pulsars may be an important component of the OSSE diffuse flux, but are most likely not important for EGRET. We estimate that as many as half of the unidentified EGRET sources may beγ-rays pulsars. Furthermore, we predict that GLAST will detect roughly 1000γ-rays pulsars, only 100 of which are currently known.
Energy Loss of Radio Pulsars
Authors: Beskin V.S. , Rafikov R.R. 
Published: July 2016

AbstractTwo-fluid effects on the radial 2D outflow of relativistic electron–positron plasma are considered. It is shown that when the longitudinal electric current is smaller than the Goldreich–Julian one, almost all electromagnetic energy is transformed into the energy of particles in the narrow boundary layer near the light surface |E| = |B|.
Beaming Due to Comptonisation in X-ray Pulsars
Authors: Galloway D.K. , Wu K. 
Published: July 2016

AbstractComptonisation may play an important role in determining beam patterns and hence pulse profiles in X-ray pulsars. We describe a Monte Carlo simulation used to investigate the spectra and pulse profiles emitted by two semi-infinite homogeneous cyclindrical accretion columns diametrically located on the surface of a ‘canonical’ neutron star.
Possible re-acceleration regions above the inner gap and pulsar gamma-ray emission
Authors: Hong B.H. , Qiao G.J. , Zhang B. , Han J.L. , Xu R.X. 
Published: July 2016

AbstractWe propose that the violent breakdown of the Ruderman-Sutherland type vacuum gap above the pulsar polar cap region may produce copious primary particles and make the charge density above the gap in excess of the Goldreich-Julian density. Such an excess residue of charge density may arise some re-acceleration regions above the gap due to the space-charge-limited flow mechanism. Such re-acceleration regions, if exist, may accelerate particles to carry away more spin-down energy, and may have some implications for pulsar γ-ray emission.
Emission of particles and photons in the pulsar polar cap
Authors: Tsygan A. I. 
Published: July 2016

AbstractWe study emission of particles and photons from a pulsar polar cap. The Goldreich-Julian model for the regime of free emission of charged particles from the neutron star surface is used. In this case the electric field is generated due to the general relativistic effect of dragging of inertial frames. The spectra and shapes of gamma-ray pulses, the parameters of the electron-positron plasma and the intensity of X-ray emission from hot spots in the polar region of radio pulsars are discussed. The effect of non-dipole magnetic field on X-ray emission of polar caps is considered. It is shown that the increase of magnetic line curvature leads to much smaller temperatures and X-ray luminosities of the polar caps as compared with the purely dipole field.
High-energy accelerators above pulsar polar caps
Authors: Xu R. X. , Qiao G. J. , Zhang B. 
Published: July 2016

AbstractSimilar to the terrestrial collision accelerators of e±, another kind of accelerator is above a positively or negatively charged pulsar polar cap. In the case of pulsars with magnetic axis parallel (anti-parallel) to rotational axis, relativistic e+(e−) with Lorentz factorγ~ 106hit the electrons in the polar caps. These scenarios are investigated both for pulsars being BSSs (bare strange stars) and for pulsars being NSs (neutron stars). Such a study may be valuable to differentiate NSs and BSSs observationally.
A full polar cap cascade model: pulsar γ-ray and X-ray luminosities
Authors: Zhang Bing , Harding Alice K. 
Published: July 2016

AbstractWe propose a full polar cap cascade model which includes the curvature and inverse Compton emission of the primary particles, and both synchrotron radiation and inverse Compton of the higher generation pairs. Such a full cascade model can reproduce both theLγ∝ (Lsd)1/2and theLx~ 10−3Lsddependences observed from the known spin-powered pulsars.
A VLBI Search for a Pulsar Nebula in SN1993J in the Galaxy M81
Authors: Bartel N. , Bietenholz M. F. , Cannon W. H. , Rupen M. P. , Beasley A. J. , Graham D. A. , Altunin V. I. , Venturi T. , Umana G. , Conway J. E. 
Published: July 2016

AbstractTwenty consecutive VLBI images of supernova 1993J in M81 from the time of explosion to the present show the dynamic evolution of the expanding radio shell of an exploded star. No clear sign of a pulsar nebula, expected to have a spectral luminosity 10 to 1,000 times larger than that of the Crab, has yet been seen. The upper limit on the brightness at 8.4 GHz in the center of the shell in one of the latest images is 0.15 mJy per beam of 0.4 mas2, corresponding to a spectral luminosity of that of the Crab. Any nebula that may have formed in the center is probably still obscured by the surrounding thermal matter with no substantial filamentation having yet occurred in the latter.
Pulsar distance measurements using interstellar scintillation data
Authors: Smirnova T.V. , Shishov V.I. 
Published: July 2016

AbstractWe evaluate the distance to pulsars and the location of the effective scattering layer of turbulent medium along the line of sight on the base of analysis diffractive and refractive scintillation of pulsars. In some cases our estimations of distances to pulsars as more than 3 times differ from the values quoted in the TML pulsar catalog.
Recycling NSs to ultrashort periods: a statistical analysis of their evolution in the μ – P plane
Authors: Possenti Andrea , Colpi Monica , Geppert Ulrich , Burderi Luciano , D’Amico Nichi 
Published: July 2016

AbstractWe investigate the statistical evolution of magnetic neutron stars recycled in Low Mass Binary (LMB) systems, simulating synthetic populations. Irrespective to the details of the physical models, we find to be significant the fraction of neutron stars spinning close to their mass shedding limit relative to the millisecond pulsar population. The simulated neutron stars show a tail in their period distribution at periods shorter than 1.558 ms, the minimum detected so far. Crustal magnetic field decay models predict also the existence of massive rapidly spinning neutron stars with very low magnetic moment.
HST Observations of PSR J2051–0827: Asymmetry, Variability and Modelling
Authors: Stappers B. W. , van Kerkwijk M. , Bell J. F. 
Published: July 2016

AbstractUsing the Hubble Space Telescope we have successfully detected the ”dark” side of the optical companion to the eclipsing millisecond pulsar J2051–0827. These data were obtained over a number of system orbits and clearly show that there is variability in the optical flux, particularly at orbital phases after maximum light. Comparison with phases before maximum light suggests this variation is due to an additional component. The data are modelled by a gravitationally-distorted low-mass secondary star which is irradiated by the impinging pulsar wind. The quality of the model fits are however limited by the variability.
Studying pulsars with the SKA and other new facilities
Authors: Bell Jon 
Published: July 2016

AbstractThe Square Kilometre Array (SKA) is a proposed next generation radio telescope. Between now and 2005 this project is in a technology development and prototyping phase, with construction likely to begin in ~ 2010. This paper describes what the SKA may be like, its key features, the motivation for building it and where you can access more details about it. Its is important to see any new facility in context, so other new facilities are also discussed. Avenues for future extensibility of the SKA other telescopes are covered, with some emphasis on multiple beam systems. Some suggestions for useful pulsar experiments and pulsar searches strategies are summarised. A conclusion is that the SKA may not be the most cost effective way to search for pulsars and that a 128 beam receiver system on an Arecibo like telescope working between 1 and 5 GHz may be a more cost effective approach.
Detecting Gravitational Waves from Quasi-Continuous Sources: the German-British Project GEO 600
Authors: Rüdiger Albrecht 
Published: July 2016

AbstractAt five sites, laser-interferometric detectors, with armlengths ranging from 0.3 to 4 km, are being built. By using advanced optical technologies early on, the German-British project GEO 600, although only intermediate in size (600 m), has good chances for a competitive sensitivity. Particularly the use of the so-calledsignal recyclingtechnique will allow a search for faint sources of only slowly varying frequency (pulsars, close binaries). First science runs of GEO 600 are expected in the year 2001.
Browsing through the Observing Books of Carloforte
Authors: Uras S. , Poma A. , Calledda P. 
Published: July 2016

The history of the Carloforte ILS Station is also the history of all the people who have spent part of their life working there. Table 1 shows the names of these people from the beginning of the service till its end.Running our eyes through the pages of the Carloforte ILS Station Observing books, we can read, beyond the cold figures that refer to the star transits, a lot of notes and comments that allow us to understand the high degree of humanity, scientific reliability and self-abnegation of the observers. Many of them, after their experience at Carloforte, had continued their activity as researchers in other fields of the Astronomy; just as an example, we may cite Bianchi, Volta, Martin, Righini, that respectively became Directors of the Astronomical Observatories of Brera, Turin, Trieste, Arcetri. We also may cite Camera, Cecchini, Nicolini, that played important roles in the Central Bureau of ILS when this one was awarded to Italy. A few on the list were just temporary observers, and their history outside of the Observatory remains unknown for us.
Survey of Observational Techniques and Hipparcos Reanalysis
Authors: Vondrák Jan , Ron Cyril , Pešek Ivan 
Published: July 2016

AbstractPolar motion and Universal Time have been regularly determined since 1899 and 1956, respectively, at a number of observatories all over the world. Before the International Earth Rotation Service (IERS) was established in 1988, the classical astrometry instruments such as visual zenith-telescopes, PZTs, transit instruments, astrolabes etc. were used. The survey of all these instruments and the methods of observation used is described. The values of instantaneous latitude and UT0-UTC made at a set of selected observatories and based on individual star observations have been collected at the Astronomical Institute in Prague during the past years. They were recalculated using the most recent astronomical standards and the Hipparcos Catalogue, and used to determine the Earth orientation parameters (polar motion, celestial pole offsets and Universal Time). The most recent solution, based on about 4.5 million observations with 47 different instruments at 33 observatories, is described and the results of polar motion presented.
The Markowitz Wobble
Authors: Poma A. 
Published: July 2016

AbstractSeveral decades ago Markowitz was the first to report the existence of fluctuations in the motion of the Earth’s axis with a period of about twenty-four years. This empirical term was often considered not real but only an artifact due to local effects. In this paper long-term variations and the relationship between the 30-yr Markowitz wobble and changes in the Earth’s rotational speed are briefly discussed.
ILS Polar Motion Results at Interannual Time Scales
Authors: Li Z.X. , Pâquet P. 
Published: July 2016

AbstractFrom a comparison between the ILS interannual polar motion and that calculated from the ILS latitude data but with different combinations of the ILS stations, the ILS polar motion has been studied at interannual time scales. It has been concluded that the interannual polar motion reduced from the ILS observations is influenced by an unknown phenomenon of the Earth; the obtained polar motion is reflecting, at interannual time scales, the real motion of the pole at certain epochs only.
Free Frequencies for a Three Layered Earth Model
Authors: Escapa Alberto , Getino Juan , Ferrándiz J.M. 
Published: July 2016

AbstractThe Hamiltonian formalism is applied to the treatment of the free motion of a three layered Earth model, where the effects of the pressure coupling, centrifugal deformation as well as gravitational and viscous-electromagnetic torques, are considered. Analytical expressions of the four normal modes of this dynamical system are derived.
Mathematical Theory of Motion of Revolving Axes on the Surface of Planets
Authors: Kozhanov T.S. , N. Nizyarov 
Published: July 2016

Let a planet perform translational and rotational motions in the field of solar attraction. Let’s assume that the observer on the surface of the planet, knows (even approximately) an orbit and variations of orientation. It is necessary to clarify the motion of the instanteous rotation axis on the planet’s surface from the observer’s point of view on the planet’s surface.1. The coordinate system, to describe the translational and rotational motions of planets around the Sun we shall take into account the properties of orbits of solar system planets, namely:
1)All planets move in the same direction as the Sun revolves.2)At the present time, from June until December the Earth’s inhabitants see the north pole of the Sun and during the second half of year the southern one (Beleckei 1975, Menzel 1959).
On the Solution of the Exterior Boundary Value Problem with the Aid of Series
Authors: Petrovskaya M. S. 
Published: July 2016

AbstractThe exterior gravitational field depending on the Earth’s non-sphericity is usually determined from the analysis of satellite data or by the solution of the exterior boundary value problem. In the latter case some integral equations are solved which correlate the exterior potential with the known vector of gravity and the shape of the Earth’s surface (molodensky problem). In order to carry out the integration the small parameter method is applied. As a result, all the quantities which involve the equations should be expanded in powers of a certain small parameter, among these being the heights of the Earth’s surface points as well as the inclination α of the Earth’s physical surface. Since the angle α can be significant, especially in mountains, and in fact does not depend on any small parameter then the solution of integral equations is possible only for the Earth’s surface which is smoothed enough.
New Formulation of De Sitter’s Theory of Motion for Jupiter I-IV. I. Equations of Motion and the Disturbing Function
Authors: Aksnes K. 
Published: July 2016

AbstractA brief discussion is given of the basic features of de Sitter’s theory. The main advantage of his theory is that it contains no small divisors, thanks to the use of elliptic rather than circular intermediate orbits in the first approximation. A 50-year extension of the satellite observations available to de Sitter makes it desirable to rederive the elements of his intermediate orbits, whose perijoves have a common retrograde motion. Furthermore, the theory suffers from a convergence problem, which can be avoided by reformulating the theory in terms of canonical variables, a task that is begun here. We adopt a formulation in Poincaré’s canonical relative coordinates rather than, as customary, in ordinary relative coordinates or in the Jacobian canonical coordinates. By means of the generalized Newcomb operators devised by Izsak, the disturbing function is expanded in a form that is very convenient for use with the modified Delaunay variables, G, L – G, H – G,l+ ω + Ω,l, and ω and their associated Poincaré variables.
Solar Perturbations in Saturnian Satellite Motions and Iapetus-Titan Interactions
Authors: Kozai Yoshihide 
Published: July 2016

AbstractSolar perturbations in Saturnian satellite motions are computed with accuracy of 10-5 to try to analyze observed data of orbital elements for Titan. Perturbations due to Iapetus in Titan’s orbit are also developed by taking into account the motion of the orbital plane of Iapetus. Then the mass of Iapetus is determined by the motion of the orbital plane of Titan. Also oblateness parameters of Saturn and the mass of Rhea are determined by seven secular motions for six satellites. It is also found in the analysis that G. Struve’s values for the semi-major axes adopted in almanacs differ from the computed values by using the new data.
Gravitational Restricted Three-Body Problem: Existence of Retrograde Satellites at Large Distance
Authors: Benest Daniel 
Published: July 2016

AbstractIn the frame of the gravitational restricted three-body problem, we study by numerical simulation the retrograde satellites -and their stability-at large distance. In the circular plane case, the stable satellites mostly surround (in the phase-space X°-V°) the characteristic of a family of single-periodic orbits where this family is stable, and librates (in the physical space) around a curve which corresponds to the nearest (in the phase-space X°-V°) periodic orbit. An analytical analysis of this libration is made for Hill’s case. The beginning of the study of the three—dimensional orbits is presented.
Periodic Orbits of the First Kind in the Restricted Three-Body Problem When the More Massive Primary is an Oblate Spheroid
Authors: Sharma R.K. 
Published: July 2016

AbstractThe existence of periodic orbits of the first kind using Delaunay’s canonical variables is established through analytic continuation in the planar restricted three-body problem when the more massive primary is an oblate spheroid with its equatorial plane coincident with the plane of motion.
Photospheric Models for Cool Giant Stars
Authors: Bessell M.S. , Scholz M. 
Published: July 2016

AbstractModels for M and C giant stars differ from those for hotter stars by having complicated state equations and opacities dominated by lines from diatomic and polyatomic molecules. In addition many cool giants have atmospheres which are extended, and which cannot therefore be adequately modelled using a plane-parallel approximation. Mira variable stars have atmospheres which are even more extended due to the regular passage of shock waves through their atmosphere. In this review we will discuss recent modelling of such atmospheres and show comparisons with observations of variable and non-variable M stars.
Current Status of the Astrometric Capabilities of the Hubble Space Telescope Fine Guidance Sensors
Authors: Jefferys W.H. , Benedict G.F. , Duncombe R.L. , Franz O.G. , Fredrick L.W. , Gerard T. , Hemenway P.D. , McArthur B. , McCartney J. , Nelan E. , Shelus P.J. , Story D. , van Altena W. , Wasserman L. , Whipple A. , Whitney J. 
Published: July 2016

AbstractThe Fine Guidance Sensors (FGSs) are the instrument of choice for most astrometric measurements with the Hubble Space Telescope (HST). The observed amount of spherical aberration in the Ritchey Chretien optical system does not affect positional measurements with perfectly aligned FGSs because they are interferometers. The FGSs combine wavefronts from points in the exit pupil with other points which are at the same radial distance from the optical axis. Asymmetric aberrations such as coma and astigmatism do affect the measured positions. The current knowledge of the HST wavefront error, the FGS operation and the implications for milliarcsecond relative astrometry are discussed. It is still planned to use the HST to tie the HIPPARCOS and VLBI Reference Frames together at the few milliarcsecond level.
Procedure for VLBI Estimates of Earth Rotation Parameters Referred to the Nonrotating Origin
Authors: Capitaine N. , Gontier A.M. 
Published: July 2016

AbstractThis paper investigates the practical use of the nonrotating origin (NRO) (Guinot 1979) for estimating the Earth Rotation Parameters from VLBI data, which is based on the rotational transformation between the geocentric celestial and terrestrial frames as previously derived by Capitaine (1990). Numerical checks of consistency show that the transformation referred to the NRO is equivalent to the classical one referred to the equinox and considering the complete “equation of the equinoxes” (Aoki & Kinoshita 1983). The paper contains the expressions for the partial derivatives of the VLBI geometric delay to be used for the adjustment of the pole coordinates, UT1 and deficiencies in the two celestial coordinates of the Celestial Ephemeris Pole (CEP) in the multiparameters fits to VLBI data. The use of the NRO is shown to simplify the estimates of these parameters and to free the estimated UT1 parameter from the model for precession and nutation.
The Organization of Space: Frames, Systems and Standards
Authors: Eichhorn Heinrich 
Published: July 2016

AbstractThe term “frame of reference” or “reference frame” has long been established in physics. The recent emergence of the use of this very term in astronomy to denote “a catalogue of the adopted coordinates of reference points that serves to define, or realize, a particular coordinate frame” is misleading because “a catalogue of adopted coordinates” must necessarily consists of estimates which cannot uniquely define a coordinate system.
Permanent Milliarcsecond Link of Celestial and Terrestrial Reference Systems
Authors: Feissel M. 
Published: July 2016

AbstractThe celestial reference system and the terrestial reference system of the International Earth Rotation Service (IERS) are realized on the basis of observation programs in Very Long Baseline radio Interferometry and laser ranging to the Moon and artificial satellites. The celestial frame is materialized by the equatorial coordinates of radio sources observed in VLBI; the terrestrial frame is materialized by the cartesian coordinates of the terrestrial sites monitored by the three techniques. Series of the Earth Orientation Parameters are derived from the same observations. These series provide a permanent link between the celestial system and the terrestrial system at the level of 0.001”.The global adjustment in which the reference systems are defined and realized is described, and the metrological properties of the frames and of the derived EOP are evaluated.