bluuebunny/crossref_metadata_2025_split huggingface dataset:
High Time Resolution Observations of the Crab Pulsar with the UCL MIC Detector
Authors: Much R. , Carramiñana A. , Fordham J.L.A. , Kawakami H. , Michel R. 
Published: July 2016

AbstractHigh time resolution (41.4μs) observations of the Crab Pulsar have been undertaken on the 2.1m telescopes at San Pedro Martir and the Observatorio Astrofisico Guillermo Haro (MX) in January/February 1999. In our prelimenary analysis of the Crab Pulsar’s light curve we obtained a slightly narrow widths on the seondary pulse than that reported by Percival et al. Our data indicate the presence of substructures in the pulsar’s main pulse, though not statistically convincing.
Small-eccentricity binary pulsars and relativistic gravity
Authors: Wex Norbert 
Published: July 2016

AbstractSmall-eccentricity binary pulsars with white dwarf companions provide excellent test laboratories for various effects predicted by alternative theories of gravity, in particular tests for the emission of gravitational dipole radiation and the existence of gravitational Stark effects. We will present new limits to these effects. The statistical analysis presented here, for the first time, takes appropriately care of selection effects.
The Proper Motions of Young Pulsars
Authors: McKay N. P. F. , Anderson B. , Lyne A. G. , Horlock J. L. 
Published: July 2016

AbstractWe report on a project to determine the proper motions of a sample of 13 young pulsars. Sky positions are measured with phase referencing using two elements of the MERLIN array, giving a baseline of 198km. This technique involves the concurrent observation of each pulsar with one or more extra-galactic reference sources located in the same primary beam. At an observing wavelength of 21 cm, this allows the measurement of pulsar positions to an accuracy greater than 1 mas.
Pulsar Profiles and Structure of the Emission Region
Authors: Kuzmin Arkady 
Published: July 2016

AbstractRecent radio observations of pulsar profiles and the present knowledge about structure of the emission region based on this profiles data are reviewed.Observations and component structure analysis revealed that there are pulsars profiles having more than 5 components. It call into question that the commonly adopted model of emission region as the double hollow cones and a central core is applicable. Mosaic model of an emission region fit observed profiles with complex more than 5 component structure.The height (radius) for the emission region evaluated from a dependence of a width of integrated profiles from the pulsar period is estimated asrem≅ 1.5 × l07P0.1cm.A comparative analysis of the frequency dependence of the profile widths of millisecond and normal pulsars in 0.1 to 1.4 GHz frequency range indicates that the frequency dependence of a width of their profiles, is much weaker than what is typically observed for normal pulsars. This suggests that the geometry of the emission region of millisecond pulsars is unlike that of normal ones.
Orthogonal Polarization Modes and Emission Regions of PSR B1133+16
Authors: Gupta Y. , Gangadhara R.T. , Rathnashree N. 
Published: July 2016

AbstractResults from an analysis of polarization data, at three different frequencies, for PSR B1133+16, show a clear systematic phase shift between the mode separated profiles for the two orthogonal modes. It is found that the shift has opposite signs for the two components of the profile. Further, the shift shows a tendency to increase at lower frequencies. The implications of these results for the origin of orthogonal modes and the location of pulsar emission regions are discussed.
Polarization Characteristics of Pulsar Profiles
Authors: Han J.L. , Manchester R.N. , Qiao G.J. 
Published: July 2016

AbstractPolarization profiles of several hundred pulsars have been published recently (eg. Gould &amp; Lyne 1998, GL98; Weisberg et al. 1999). In this report, we summarize the characteristics of circular and high linear polarizations of pulsar profiles, based on all previously published data.
Pulsar Research with the GMRT: A Status Report
Authors: Gupta Y. , Gothoskar P. , Joshi B.C. , Vivekanand M. , Swain R. , Sirothia S. , Bhat N.D.R. 
Published: July 2016

AbstractThe Giant Metrewave Radio Telescope (GMRT) coming up near Pune, India will be one of the important instruments for pulsar research work at metre wavelengths. Here we describe the capabilities of the GMRT for pulsar work and give the current status of the telescope in this context. Results from recent test observations are also summarised.
Coherent De-dispersion Observations at Jodrell Bank
Authors: Ord S. M. , Stairs I. H. , Camilo F. 
Published: July 2016

AbstractCoherent de-dispersion removes the dispersive effect of the interstellar medium by convolving the digitally sampled telescope output voltages with an inverse filter function, derived from the tenuous plasma dispersion law. The time resolution obtainable by this method is limited only by the bandwidth that can be sampled sufficiently fast as to avoid aliasing. This allows high time resolution, therefore high precision, timing and polarimetry observations of millisecond pulsars. We present here the first results from the Jodrell Bank coherent de-dispersion system.
Pulsar Applications of the Caltech Parkes Swinburne Baseband Processing System
Authors: van Straten Willem , Britton Matthew , Bailes Matthew , Anderson Stuart , Kulkarni Shri 
Published: July 2016

AbstractThe Caltech-Parkes-Swinburne Recorder (CPSR) was installed at the Parkes Radio-telescope in August of 1998. It is capable of continuously two-bit quadrature-sampling a 20 MHz bandpass in two polarizations, though other configurations are possible. Since its successful installation, over 17 Terabytes of observational data have been recorded. These data were processed using the Swinburne Baseband Processing System (SBPS), a suite of data management and reduction software executed using a Beowulf-style cluster of high-performance workstations. A description of CPSR and SBPS is presented herein, followed by a brief presentation of some results from the past year of observations, and an outline of possible future uses of the system.
NTT and VLT Observations of two young pulsars
Authors: Mignani Roberto 
Published: July 2016

AbstractThe two young pulsars PSR J0537-6910 and PSR B1706-44 have been recently observed with the NTT and the VLT. Although both pulsars turned out to be undetected (V≥ 23.4 andV≥ 27.5 respectively) the observations provided interesting constraints on the evolution of the optical luminosity of young pulsars.
Implications of the Optical Observations of Isolated Neutron Stars
Authors: Shearer Andy , Golden Aaron , Beskin Gregory 
Published: July 2016

AbstractObservations of the 5 confirmed optical pulsars indicate that the peak emission scales according to the outer field strength. We show that this gives gives further confirmation that a simple phenomenological models such as Pacini and Salvati (1987) still have validity. Furthermore we show that the Crab pulsar exhibits unpulsed emission which further complicate any studies of the thermal emission from Isolated Neutron Stars.
PSR J0218+4232 in the energy band 1–10 keV observed with BeppoSAX
Authors: Nicastro Luciano 
Published: July 2016

AbstractOn behalf of a large collaboration (see Mineo et al. (1999) for details) I present the results of a BSAX observation of PSR J0218+4232 which, for the first time, provides detailed information on the pulsar temporal and spectral emission properties in the broad energy band 1–10 keV.
Testing the two-stream instability in a pulsar magnetosphere
Authors: Asseo Estelle 
Published: July 2016

AbstractConditions for the development of a two-stream instability in a pulsar magnetosphere are deduced from specific dispersion relations for plane wave perturbations, that depend on the distribution functions of the involved particles. Three different approaches are investigated.Firstly, using relativistic one-dimensional Juttner Synge distribution functions appropriate to describe pulsar pair plasmas flows, we analytically derive the dispersion relation anew, precisely determining the dependence of its coefficients on the temperature, fluid velocity and associated Lorentz factor. We obtain modified frequencies for quasi-longitudinal waves and specific conditions for a two-stream instability to develop.Secondly, the importance of two-stream instabilities is tested numerically on two different timescales, that concern stationary and non-stationary properties of pair plasma flows. The linear analysis involves Gaussian distribution functions of the momentum, factorized with functions that depend on the localisation of the different groups of particles, and shows results that agree with observed luminosities.Finally as derived from fluid equations, the nonlinear evolution of such an instability process allows to associate the high level of radio radiation observed from pulsars with the existence of a lattice of radiating ‘Langmuir‘ soliton-like structures in a pulsar emission region. Actually, pair plasma particles follow the bundle of diverging magnetic field lines in the open magnetosphere and ‘Langmuir‘ soliton-like solutions, modified by magnetic field and density gradients, imply additional radiation.
Pulsar Electrodynamics
Authors: Shibata Shinpei 
Published: July 2016

AbstractFirst 1 emphasize the magnetospheric loop current system induced by the wind activity. Next, I address the formation of the field-aligned electric field. An interesting aspect is the reaction of the inner magnetosphere to an induced current. In the traditional outer gap, the current running through the gap is all carried by the particles created in the gap. However, if external current-carrying particles are added, the gap moves inward or outward; it can even appear near the star. It is suggested that the gaps appear at various altitudes, depending on the current distribution on field lines, the field line geometry, and the source of the current-carrying particles.For definiteness of sign of charge and current direction,Ω ·μ&gt; 0 is assumed throughout.
Pulsar Death at an Advanced Age
Authors: Arons Jonathan 
Published: July 2016

AbstractI summarize the theory of acceleration of non-neutral particle beams by starvation electric fields along the polar magnetic field lines of rotation powered pulsars, including the effect of dragging of inertial frames which dominates the acceleration of a space charge limited beam. I apply these results to a new calculation of the radio pulsar death line, under the hypotheses that pulsar “death” corresponds to cessation of pair creation over the magnetic polesandthat the magnetic field has a locally dipolar topology. The frame dragging effect in star centered dipole geometry does improve comparison of the theory with observation, but an unacceptably large conflict between obsrvation and theory still persists. Offsetting the dipole improves the comparison, but a fully satisfactory theory requires incorporating magnetic conversion of inverse Compton gamma rays, created by scattering thermal photons from the surface of old neutron stars (t&gt; 108years) kept warm (T≥ 105K) by friction between the rotating core and the crust. The result is a “death valley” for pulsars; offsets of the dipole center from the stellar center in the oldest stars ~ (0.7 − 0.8)R*suffice. The resulting theory predicted the existence of rotation powered pulsars with these advanced ages, a prediction confirmed by the recent discovery that PSR J2144-3933 actually has a rotation period of 8.5 seconds.
ICS as a Limiting Factor for Electron Energies in Pulsar Magnetospheres
Authors: Supper Rodrigo 
Published: July 2016

AbstractBased on the polar cap model, we investigated in the energy loss of accelerated electrons in a neutron star magnetosphere by inverse Compton scattering of thermal photospheric radiation. An analytical treatment is presented, which turns out ranges in the magnetic field strength and thermal temperature where ultrarelativistic electrons can not survive.
1997 October Event(s) in the Crab Pulsar
Authors: Backer D. C. 
Published: July 2016

AbstractIn October 1997 daily monitoring observations of the Crab pulsar at 327 MHz and 610 MHz with an 85ft telescope in Green Bank, WV showed a jump in the dispersion by 0.12 cm−3pc. Pulses were seen simultaneously at both old and new dispersions for a period of days. In the months before this event faint ghost emission, a replica of the pulse, was detected with a nearly frequency independent delay that quadratically diminished to zero. There was also a curious shift in the phase, a slowdown, at all frequencies at the time of the dispersion jump. I attribute most of these phenomena to the perturbing optics of a plasma prism that is located in the filamentary interface between the synchrotron nebula and the supernova ejecta and which crosses the line of sight over a period of months. The required density, scale length and velocity are reasonable given detailed HST and previous observations of these filaments.
Infrared Observations of the Crab Nebula
Authors: Gallant Yves A. , Tuffs Richard J. 
Published: July 2016

AbstractWe obtained narrow-band continuum images of the Crab Nebula at 16, 6.4 and 2.2µm. From these we derive spectral index maps, extending the optical work of Véron-Cetty &amp; Woltjer (1993). In the central parts of the Nebula the IR spectral index is close to the radio one, indicating the region where the radio-emitting electrons are accelerated.
Plasma Theory of Two Synchrotron Knots’ formation Discovered in the Crab Nebula
Authors: Shapakidze David , Machabeli George 
Published: July 2016

AbstractThe plasma mechanism of synchrotron knots’ formation discovered in the Crab Nebula at the distances 0″.65 (1016cm) and 3″.8 (6 × 1016cm) from the Crab pulsar is presented. The mechanism is based on exitation of cyclotron and Cherenkov-drift instabilities in the relativist s electron-positron plasma of the nebula. The higher luminosity of the knots is supposed due to the orientation of the direction of motion of the synchrotron radiation sources (Larmor circles) relative to the observer.
Supernova Remnant CTB 80 and PSR 1951+32
Authors: Strom R. G. , Stappers B. W. 
Published: July 2016

AbstractThe 39.5 ms pulsar PSR 1951+32 and the remnant with which it is associated, CTB 80, have both been observed with the recently upgraded Westerbork synthesis array (WSRT). Parts of CTB 80 have been observed over the frequency coverage from 0.3 to 8 GHz, while PSR 1951+32 has been observed from 0.3 to 1.6 GHz. The results are described and discussed in the context of the pulsar-remnant association.
Pulsars and Interstellar Scintillations
Authors: Gupta Y. 
Published: July 2016

AbstractIn this paper, I review our current understanding of interstellar scintillations (ISS) of pulsars. The emphasis is on new results that have appeared during the last five years. The topics covered include (i) review of the understanding of refractive ISS (ii) the shape of the spectrum of electron density fluctuations in the interstellar medium (iii) the distribution of scattering plasma in the Galaxy (iv) resolving pulsar emission regions using ISS and (v) ISS and pulsar velocities.
Observations of the interstellar scintillation of nearby pulsars at 1.7 GHz with the 32-m Toruń radiotelescope
Authors: Redmerska Malgorzata , Konacki Maciej , Lewandowski Wojciech , Wolszczan Alex 
Published: July 2016

AbstractPreliminary results of 1.7 GHz monitoring of the interstellar scintillation of low-DM pulsars with the TCfA 32-m radiotelescope are presented. The dynamic spectra of pulsar intensity variations have been measured with the PSPM-2 which is a 2 × 64 × 3 MHz - channel spectrometer. The 192 MHz total bandwidth of this device provides an adequate frequency coverage to fully parametrize the observed scintillation. A distinct multiple imaging event has been identified in the dynamic spectra of PSR B1133+16.
Low–Mass He WDs and Millisecond Pulsars Age Determination
Authors: Antipova J. , Ergma Ene , Sarna M. J. 
Published: July 2016

It is accepted that the formation of a millisecond binary pulsar (MBP) with a low–mass companion may be explained as the end–point of close binary evolution in which an old pulsar is spun–up by accretion from the red giant (Bhattacharaya &amp; van den Heuvel 1991). In this paper we shall discuss the cooling properties of the helium white dwarfs (WD) in short orbital period MBP systems PSR J0437–4715, PSR J0751+1807 and PSR J1012+5307, without referring to the rotational history of neutron stars (NS).Below we discuss observational data for several system for which the results of our calculations (Sarna, Antipova, &amp; Muslimov 1998; Sarna, Ergma, &amp; Antipova 1999) may be applied, by taking into account the orbital parameters of the system, the pulsar spin-down time, and the WD cooling time-scale.
Protoneutron stars and neutron stars
Authors: Gondek-Rosińska D. , Haensel P. , Zdunik J. L. 
Published: July 2016

AbstractWe find constraints on minimum and maximum mass of ordinary neutron stars imposed by their early evolution (protoneutron star stage). We calculate models of protoneutron stars using a realistic standard equation of state of hot, dense matter valid for both supranuclear and subnuclear densities. Results for different values of the nuclear incompressibility are presented.
Discovery of a supernova remnant with a central X-ray source: AX J184453.3-025642 in G 29.6+0.1
Authors: Gotthelf E. V. , Vasisht G. , Gaensler B. , Torii K. 
Published: July 2016

AbstractWe report preliminary results from our follow-up X-ray and radio study of AX J1845–0258, the 7-s X-ray pulsar whose characteristics are similar to those found for the anomalous X-ray pulsars (AXPs). We have located a faint X-ray source within the pulsar’s error circle implying a dramatic reduction in flux, however, the source is too faint to provide a confirmation of the expected pulsations. Centered on this X-ray source is a newly discovered supernova remnant, evident in both radio and X-ray emission. This is the third example of an AXP-like object associated with a supernova remnant.
The First Decade of the IERS
Authors: Mueller Ivan I. 
Published: July 2016

AbstractThe International Earth Rotation Service (IERS) was established in 1987 by the International Astronomical Union (IAU) and the International Union of Geodesy and Geophysics (IUGG), and it began operation on 1 January 1988. The primary objectives of the IERS are to serve the astronomical, geodetic and geophysical communities by providing the following:
•The International Celestial Reference System (ICRS) and its realization, the International Celestial Reference Frame (ICRF).•The International Terrestrial Reference System (ITRS) and its realization, the International Terrestrial Reference Frame (ITRF).•Earth orientation parameters required to study Earth orientation variations and to transform between the ICRF and the ITRF.•Geophysical data to interpret time/space variations of the ITRF with respect to the ICRF, i.e., of the Earth orientation parameters, and to model such variations.•Standards, constants and models (i.e., conventions) encouraging international adherence.This presentation primarily covers the first three IERS functions from the operational point of view.
Long-term Earth Orientation Monitoring Using Various Techniques
Authors: Gambis D. 
Published: July 2016

AbstractA continuous composite series of polar motion components extending from 1846 until now called EOP (IERS) C01 is available at the Earth Orientation Section of the Central Bureau of the IERS. This series is the basis of the IERS system. It relies on different series derived from optical astrometry until 1972 and geodetic techniques since. It is given at 0.1 year intervals (1846–1889) and 0.05 year intervals (1890-now). Its accuracy has dramatically improved from 100 mas in 1846 to about 0.2 mas at present.Now the IERS combined solutions involve mainly the contributions of VLBI, GPS and SLR techniques. It is regularly recomputed to take advantage of the improvement of the various recent individual contributions and of the refinement of the analyses procedures.The objective of this paper is to describe this long-term polar motion series and to present the evolution and the state of the art of the multi-technique EOP combined solutions and the predictions regularly computed at the IERS/CB.
Anaglif Representation of Polar Motion over the Last Century
Authors: Nagy S. 
Published: July 2016

This is a special demonstration of the polar motion over the last century. Our figures represent the (xp, yp) coordinates of Earth’s axis, and the elapsed time along the z-axis. The figures remind us of a spiral spring. For the sake of illustration we used the so-called anaglif projection. Red and green glasses must be used to see the figures. The whole century (1899–1999) is too long for one diagram. So we divided the database into ten parts and present ten figures. The historic data was taken from IERS EOP C01 database and the new data from the IERS Bulletin B (1997,1998). The EOP C01 database contains only twenty (xp, yp) pairs per year. This is not sufficient for the refined representation, therefore we used the cubic spline interpolation for densification. The ten figures presented provide a quick review of the history of the polar motion over the last century: small amplitude in the twenties and thirties, with powerful fluctuation in the fifties. It is remarkable how the spiral leaves the Conventional International Origin (CIO) westwards due to the secular polar motion.Remark: a series of figures is available upon request from the author (e-mail: nagy@sgo.fomi.hu).
Regional Signals in Atmospheric and Oceanic Excitation of Polar Motion
Authors: Nastula Jolanta , Ponte Rui M. , Salstein David A. 
Published: July 2016

AbstractAtmospheric and oceanic variability have been shown to play a role in the excitation of polar motion. Regional patterns of atmospheric and oceanic excitation are analysed and compared. The equatorial excitation functions, χ1 an χ2, for the ocean are computed using velocity and mass fields from a near-global ocean model, driven by observed surface winds stresses, surface heat and freshwater fluxes, for the period from January 1985 to June 1997. To understand the relative role of the ocean versus the atmosphere, we used atmospheric excitation functions computed from the National Centers for Environmental Prediction/National Center for Atmospheric Research reanalyses. We consider regional mass terms [bottom pressure and atmospheric surface pressure with the inverted barometer (IB) correction] and regional motion terms as well (currents and winds). Results here confirm recent findings that oceans supplement the atmosphere as an important source for polar motion excitation. Regional signals in the oceanic bottom pressure terms have comparable amplitudes to those in the atmospheric pressure-IB terms. The regional wind term amplitudes, however, are several times larger than the values for both regional oceanic currents term and atmospheric pressure-IB term. Power in regional oceanic excitation is distributed between seasonal and subseasonal timescales while in the case of atmospheric excitation it is concentrated rather at seasonal timescales.