bluuebunny/crossref_metadata_2025_split huggingface dataset:
Broad-Line Profile Variability
Authors: Wanders Ignaz 
Published: July 2016

AbstractMany years of monitoring a sample of 10 AGNs with a median sampling rate of about one spectrum per week yields strong evidence that broad-line profile variations are not induced by reverberation effects, but rather signify real changes in the structure of the continuum-source and broad-line region complex, contrary to line flux variations, which do respond to continuum variations. If the profile variations indeed trace internal changes in the BLR, then the BLR cannot consist of the billions of small clouds as the standard model of the BLR prescribes. Rather, small-number statistics are necessary. The sample of AGNs also indicates there are three preferred ‘components’ in the line profiles. These can be explained as geometrical projection effects due to an anisotropic continuum irradiating an otherwise spherical BLR.
Inconsistency of Photoionization Models for NGC 5548: Proof of Mechanical Heating?
Authors: Collin-Souffrin S. , Dumont A.-M. , Nazarova L. 
Published: July 2016

AbstractIt is shown that, in the case of NGC 5548, photoionization models cannot account for line fluxes, line ratios, and line variations. The assumption that a fraction of the broad-line region is mechanically heated can solve the problem.
AGN Spectra as Seen by the Infrared Space Observatory: First Results
Authors: Lutz D. , Genzel R. , Sturm E. , Moorwood A.F.M. , Oliva E. , Marconi A. , Netzer H. 
Published: July 2016

AbstractWe discuss 2.5–45 µm spectra of the Circinus galaxy and of Cen A, obtained with the Short Wavelength Spectrometer (SWS) on board the Infrared Space Observatory. The large number of detected ionic fine structure lines, observable also in visually obscured sources, provides strong constraints on the shape of the ionizing spectrum, which is found to exhibit a UV bump peaking at ~ 70 eV in the case of Circinus. Pure rotational emission of molecular hydrogen, directly probing warm molecular gas, can for the first time be detected in external galaxies.
Cospatial Line Emission and Accelerated Outflow in the Spatially Resolved Narrow-Line Region of NGC 4151: Confirming Model Predictions
Authors: Moore D. , Cohen R.D. , De Robertis M.M. 
Published: July 2016

AbstractWe present results of high S/N, high spatial and spectral resolution (0″.65 and 0.8Å FWHM, respectively) spectrophotometry of the NLR of NGC 4151 using the Keck 10-m Telescope. The observations are the first in a series that test unambiguously several specific predictions that are based on earlier modeling of spatially unresolved emissionline spectra. Importantly, we partially resolve the source of most of the emission-line flux. Thus, the observations suitably complement analyses of spatially unresolved NLR spectra.
Millisecond Pulsar Surveys
Authors: Bailes M. 
Published: July 2016

AbstractThere are now more than 30 millisecond pulsars known to be associated with the Galactic disk. The majority of these have been discovered in just the last few years as the result of large-scale all-sky surveys. The properties of the population vary tremendously. One unique object hosts a planetary system, more than half of those discovered possess white dwarf companions, two have extremely low-mass companions that are undergoing mass-loss and several others appear to be solitary. In this review I discuss the methods employed to find these millisecond pulsars, the parallels with early surveys for “normal” pulsars, and possible strategies for future searches.
The Origin of Millisecond Pulsar Velocities
Authors: Tauris Thomas M. 
Published: July 2016

We have developed a computer code (Tauris &amp; Bailes 1996) to follow the evolution of a binary system from the zero-age main sequence to its “final” state as a binary millisecond pulsar (BMSP), at all stages keeping careful track of the mass and orbital separation of the two stars.To help determine the origin of millisecond pulsars, we compute the space velocities predicted by various models of their formation. It is difficult to produce a millisecond pulsar velocity greater than 270 km s−1with any model, unless the formation of the neutron star is accompanied by some form of asymmetric kick. We obtain average 3-D system velocities of 〈vrecoil〉= 99.6, 137.6 and 160.7 km s−1using Gaussian kicks of 〈vkick〉=0, 200 and 450 km s−1(σ=0, 100 and 200 km s - 1, respectively). Our computations show that, in general, we expect those systems with shorter orbital periods to have larger velocities than those with longer periods, but any relation between the final orbital period and space velocity is fairly weak, especially if asymmetries are involved.
The Cluster Analysis of Pulsar Parameters
Authors: Malov Igor’ F. , Malov Oleg I. 
Published: July 2016

We have used the catalogue of (Taylor et al., 1993) to investigate the problem of a classification of pulsars. Five samples have been analysed by the main components method and by methods of the cluster analysis.i)15 pulsars with 14 known parameters P, Ṗ, W50,L(Malov et al., 1994),B,z,spectral indexa, frequencies of maximumVMand minimumVcin a spectrum (Malofeev et al., 1994), an angle between magnetic moment and rotation axisβ(Malov, 1994), the transformation coefficientη=L/Ė, magnetic field near the light cylinderBlcand a maximum derivative of a position angleC= (dψ/dφ)max(Malov, 1990).ii)130 objects with 10 parameters (the spectral characteristicsα,VM,VCand the parameter C were excluded from the consideration).iii)218 pulsars with 4 known parameters P, Ṗ, L andz. These parameters can be considered as independent variables.iv)89 sources with the same 4 parameters. This sample consists of two subsamples: 65 pulsars withP&gt; 1 s and 24 ones withP&lt; 0.1 s.v)24 pulsars withP&lt; 0.1 s from the previous sample.
Pulsar Astrometry and Improved Terrestrial Clocks
Authors: Matsakis Demetrios N. , Josties Frederick J. , Foster Roger S. 
Published: July 2016

AbstractRecent improvements in cesium and hydrogen terrestrial frequency standards have brought the frequency precision of International Atomic Time (TAI) to a value of 2.5E-15 s/s over an averaging time of a month. In this paper we illustrate the improvement graphically, and discuss the state of the art for frame ties between the radio, dynamical, and optical frames. In a larger paper, available via the World Wide Web, we illustrate the measured accuracy curves of the frequency standards, show their effect on the ensemble time scales, explain the reasons for the confusing array of available time scales, and discuss the inverse problem of using pulsar data to correct the terrestrial time scale.
Phase-referenced VLBA Observations of PSRs B1937+21 and B0329+54
Authors: Dewey Rachel J. , Beasley Anthony J. 
Published: July 2016

In this paper we present the preliminary results of phase-referenced VLBA observations of two pulsars PSRB1937+21 and PSRB0329+54. Since pulsar observations usually require a lower observing frequency than that used for other astrometric applications, ionospheric delays are a significant source of systematic error. For the observations presented here we used total-electron-content (TEC) measurements derived from dual-frequency GPS observations (Wilson, Mannucci &amp; Edwards, 1995) to calibrate ionospheric delays.Using this calibration technique were able to obtain positions for these two pulsars which we believe to be accurate to approximately 2 mas in each coordinate. With this level of accuracy we expect astrometric pulsar observations to be able to address a variety of interesting issues ranging from reference frame alignment and fundamental astrometry to the origin of pulsar velocities.
Inverse Compton Scattering in pulsar physics
Authors: Qiao G.J. 
Published: July 2016

AbstractInverse Compton Scattering (ICS) is a very important process not only in inner gap physics, but also for radio emission. ICS of high energy particles with thermal photons is the dominant and a very efficient mechanism of the particle energy loss above the neutron star surface, and is an important process in causing gap breakdown. The pulsar distribution in theP−Pdiagram and the observed mode changing phenomenon of some pulsars can be expained by the sparking conditions due to ICS. ICS of the secondary particles with the low frequency wave from the inner gap sparking can be responsible for radio emission. In this ICS model, many observational features of pulsar radio emission can be explained, such as: one core and two conal emission components, their different emission altitudes and relative time delay effects; spectral behavior of pulse profiles; the behavior of the linear polarization and position angle.
Microstructure and patterns of coherent radiation
Authors: Ables J. G. , McConnell D. 
Published: July 2016

AbstractWe present data which indicates that micropulses from the bright millisecond pulsar PSR J0437–4715 are observed at equally-spaced preferred phases within the pulse window. We find the pattern similar to that expected if each micropulse is radiated from a source with a coherence scale of ~ 100 m.
A model for PSR J0437-4715
Authors: Gil Janusz , Krawczyk Agnieszka 
Published: July 2016

We present the modelling results of full polarization data of the PSR J0437-4715, recently published by Manchester &amp; Johnston (1995). This pulsar presents a real challenge for pulsar modelling because of seven clear components in its mean profile. In terms of the conal model of pulsar emission this is the first case indicating three distinct cones surrounding the central core beam. We have attempted to model this pulsar and obtained a very satisfactory fit to the data. We succeded to reproduce the complexities of the multiple component profile and polarization properties.To model the radiation from PSR J0437-4715 we use the method presented in Gil et al. (1995 and references therein). We assume that subpulses in single pulses correspond to the subpulse-associated plasma columns distributed within the overall pulsar beam. Each column represents a gaussian intensity distribution. These columns rotate more or less regularly around the magnetic axis. The exception is the central column directed almost along the magnetic axis defined by the local surface magnetic pole. This column corresponds to the core beam and consequently to the core component in our model. Outer columns rotating at some distances from the core axis will form a number of coaxial conal beams corresponding to the conal profile components. Figure 1a represents a projection of the subpulse-associated columns onto the polar cap while Fig. lb represents schematically a corresponding multiconal structure of the average beam. The initial positions, the characteristic dimensions and the relative amplitudes of the subpulse spots (Fig. 1a) have been estimated from the mean profile (Fig. 2b). We assume that the subpulse spots are separated from each other by distances comparable with their sizes (Fig. 1a). The very large polar cap with the radiusrp= 1.4 · 104P−1/2cm ≈ 1900 m as compared with the characteristic subpulse spot dimensionD≈ 300 m allows three conal rings surrounding the central core beam (Fig. 1b).
Properties of individual and integrated pulses drawn into mode changing phenomenon in PSR 0943+10 at 40, 103 and 430 MHz
Authors: Suleymanova S.A. , Izvekova V.A. , Rankin J.M. 
Published: July 2016

AbstractPulsar 0943+10 demonstrates very obviously that the mode switching phenomenon includes simultaneous and dramatic alterations of all principal properties of radioemission, i.e. intensity, polarization (both linear and circular) and drifting behaviour of individual pulses over a broad frequency range. On the basis of observations of PSR 0943+10 at the frequencies 40 and 430 MHz, a complete scenario of the transition process between two modes of radiation has been revealed. The ‘pre-switching transition process’ is found which manifests itself as attenuation of the pulse intensity of the current mode during hundreds of the pulse periods preceding a switch.
An Explanation for Pulsar Mode Changing Phenomenon
Authors: Zhang B. , Qiao G.J. , Lin W.P. , Han J.L. 
Published: July 2016

AbstractThere are three mechanisms to cause pulsar inner gap breakdown: the inverse Compton scattering (ICS) of the high energy particles off the thermal-peak photons, off the resonant-frequency photons and the curvature radiation (CR). The pulsar mode-changing phenomenon can be interpreted as a switching effect between theresonant ICS sparking modeand thethermal ICS sparking mode.
Pulse profiles of millisecond pulsars
Authors: Jayawardhana Ray , Grindlay Jonathan E. 
Published: July 2016

We present a comparison between the average radio pulse profiles of millisecond pulsars (MSPs) in the field and in globular clusters. Our sample consists of 20 field MSPs and 25 cluster MSPs for which observations exist at 400 - 600 MHz.We find that 6 of the 20 field MSPs, or about 30%, have a comparable interpulse at a phase offset of 180 ±30 degrees. None of the cluster objects shows this feature. Here we define a ‘comparable interpulse’ as one whose intensity is at least 10% of the primary pulse. This lower limit is well above the noise level of all the profiles in our sample. While the cluster MSPs have much more poorly resolved profiles at present than field MSPs, it is unlikely that a strong interpulse near 180 degrees could be ‘hidden’ within the primary peak.
Monitoring Millisecond Pulsars in Full Polarization
Authors: Xilouris Kiriaki M. , Kramer Michael 
Published: July 2016

AbstractOver a two year period the polarization properties of the largest sample of millisecond pulsars yet observed have been regularly monitored with the Effelsberg 100-m radiotelescope at λ21cm. A comparison of the observed emission properties with those of the population of long period pulsars is presented here. Most of the sources exhibit wide, often multiple-component profiles, with complex polarization features, not easily interpretable in the context of the well established phenomenological models used to describe the properties of long period pulsars. While both groups share common emission features suggesting similar emission processes, the implied field structures as revealed from polarization information appear substantially different from a dipolar structure. Generally, short period pulsars exhibit a relatively large percentage of circularly polarized emission while at λ21cm they tend to be less polarized than long period pulsars.
Multifrequency Radio Properties of the Crab Pulsar
Authors: Moffett David A. , Hankins Timothy H. 
Published: July 2016

During a single Arecibo observation in 1981 of the Crab pulsar, a profile at 4.7 GHz was recorded which appeared to contain additional components and an interpulse (IP) shifted to earlier phase. The experiment was continued at the VLA, taking advantage of its phased array mode to form a synthesized beam, which resolves out the bright Crab Nebula background. Observations were conducted between February 9 and May 27, 1994, at 0.33, 1.4, 4.9, and 8.4 GHz. Additional radio profiles presented here were recorded at Arecibo (0.43, 0.6, and 4.7GHz) and Effelsberg (2.7GHz) by Hankins &amp; Fowler (unpublished).In Figure 1 we have plotted a summary of normalized profiles from several radio frequencies and infrared. The VLA profiles are time aligned, while the rest are aligned to the main pulse (MP). A new component (labeled LFC) appears 36° ahead of the MP between 0.6 and 4.9 GHz, not coincident with the position of the precursor, and with a spectral index similar to that of the MP. The MP disappears at 8.4 GHz, probably due to spectral effects. The IP appears to undergo a transition in phase and flux, disappearing at 2.7 GHz and reappearing 10° earlier at 4.7 GHz with a radically different spectral index. Two high radio frequency components (labeled HFC1 and HFC2) appear at 4.9 and 8.4 GHz, and possibly at the noise level at 1.4 GHz. They have flatter spectral indices than the MP and IP and their centroid phase changes with respect to the MP – moving to later phase with increasing frequency. The infrared profile exhibits a “bump”, or third component near the same phase as HFC1 and HFC2.
Pulsar radio beams and emission altitudes
Authors: Kijak Jaroslaw , Gil Janusz A. 
Published: July 2016

We verify the relationship proposed by Kijak and Gil (1996) for the pulsar radio emission altitudes(see also Eq.3 in Gil &amp; Krawczyk, 1996), using the pulse-profile Effelsberg raw data at 1.41 GHz. We measured profile pulse-widths at the lowest intensity level corresponding to 0.01% of the maximum intensity (Fig. 1b), using the polarlog-scale technique (Hankins and Fowler, 1986). We calculated opening angles (Fig. 1a) and emission altitudes (Fig. 1c) assuming that:i) pulsar radiation is narrow-band with radius-to-frequency mapping operating in the emission region,ii) pulsar emission is beamed tangentially to the dipolar magnetic field lines,iii) the extreme profile wings originate near or at the last open field lines.
ASCA X-Ray Observations of the Vela Pulsar Jet
Authors: Ögelman Hakki , Markwardt Craig 
Published: July 2016

AbstractAn X-ray jet-like outflow, beginning at the Vela pulsar and extending about seven parsecs along the pulsar spin axis direction has recently been discovered (Markwardt &amp; Ögelman 1995). We present data obtained by the X-ray ASCA satellite which confirms the enhanced X-ray emission at the jet head and discuss the allowable spectral models. The jet parameters are updated according to the combined ROSAT and ASCA results.
Origin of High Velocity Pulsar and Soft Gamma Ray Repeaters
Authors: Hanami Hitoshi 
Published: July 2016

AbstractWe consider a close binary system with separation ≃ 0.2 R⊙which consists of a (C+O) star of mass ≃ 4 M⊙and a neutron star as a progenitor of soft gamma-ray repeater (SGR) and a high velocity pulsar. After the event of the supernova explosion, both new and old neutron stars have high relative velocity of ≃ 1000km s−1to the center of mass of the ejecta. SGR activities can be induced by the episodic accretion of the supernova ejecta onto the old neutron star or the strange high rotating pulsar of the new neutron star. Future observations with fine positional resolution can clarify the position ambiguity between the gamma ray and X-ray sources.
Pulsar/Supernova Remnant Associations
Authors: Kaspi Victoria M. 
Published: July 2016

AbstractWe review proposed pulsar/supernova remnant associations, summarize recent highlights, including searches for young pulsars, searches for remnants, studies of previously proposed associations, and attempts at pulsar/remnant association syntheses. We argue that most proposed associations require additional investigation before they can be considered secure. Existing evidence from secure associations implies pulsars are born with large magnetic fields and short periods, but do not necessarily have particularly large radio luminosities. We argue that the evidence for large space velocities from associations is ambiguous.
Pulsar Flux Monitoring and Refractive Scintillation
Authors: Stinebring Daniel R. , Smirnova Tatiana V. , Hovis Jennifer , Kempner Joshua C. , Myers Edward B. , Hankins Timothy H. , Kaspi Victoria M. , Nice David J. 
Published: July 2016

AbstractWe have monitored the 610 MHz flux density of 21 pulsars on a daily basis for five years. The flux density time series for these pulsars range from nearly constant for the most distant and heavily scattered pulsars to rapidly varying, saturated time series for more nearby pulsars. The measured stability of the flux density from the most distant pulsars (variations less than 5%) implies that the average radio emission from pulsars, before it has been affected by propagation through the ISM, is constant in strength over five years. The flux variations for 12 of the pulsars are consistent with a Kolmogorov turbulence spectrum over a range of more than three orders of magnitude in scattering strength, with no detectable presence of an inner scale (si≥ 107cm). The flux variations are greater than predicted by this model for five pulsars – including the Crab and Vela – but this group is consistent with a Kolmogorov spectrum and an inner scale of ∼ 1010cm.
Resolving Pulsar Magnetospheres Using Interstellar Scintillation
Authors: Smirnova T. V. , Shishov V. I. , Malofeev V. M. 
Published: July 2016

Pulsars are very small objects and to resolve a pulsar magnetosphere you would need an interferometer with a baseline of 14 AU at a frequency 100 MHz. If the angular size of the diffraction pattern at the Earth is less than the angular size of pulsar:θc&lt;θLCthen emission regions separated by alight-cylinder radius will produce scintillations that are independent. The interstellar scintillation method presents a unique oppotunity for measuring the angular size of sources with a resolution up to 10−8arcsec at meter wavelengths.There were different attempts to resolve pulsar magnetospheres by the scintillation method (Cordes, Weisberg and Boriakoff, 1983, Wolszcan and Cordes, 1987; Smirnova and Shishov, 1989; Smirnova, 1992). Here we present new observations of 4 pulsars: PSR 0834+06, 1133+16, 1237+25 and 1919+21 at a frequency 102 MHz from which we can see evident decorrelation of the pulsar spectrum with increasing space separation between sources in the pulsar magnetosphere.
Kinematic distances for southern pulsars: Gum & Carina
Authors: Koribalski Bärbel , Johnston Simon , Weisberg Joel 
Published: July 2016

We have observed 21-cm absorption and emission spectra in the direction of about 20 southern pulsars with the Parkes telescope to derive their kinematic distances and to study the interstellar medium. In each case we thoroughly investigated the environment of each pulsar as well as sources along the line of sight which may contribute to the pulsars’ dispersion measure (DM).Some of the results, which are published in Koribalski et al. (1995) and Johnston et al. (1996), are included in the compilation of Hi absorption measurements by Joel Weisberg in this volume. In the following we present a detailed discussion on pulsars toward 1) the Gum Nebula and 2) the Carina Arm.
Non-Stationary Accretion in Her X–1–like Systems
Authors: Geppert U. , Urpin V. 
Published: July 2016

Accretion heats the neutron star crust thereby decreasing the electric conductivity in the solid region. This leads to a rapid field decay when the currents supporting the field are concentrated in the solid crust (Geppert &amp; Urpin 1994, Urpin &amp; Geppert 1995). Depending on the duration of the accretion phase and on the total mass accreted the field can be decreased by 3 − 4 orders of magnitude after 106− 107years. This mechanism explains the low magnetic fields of many pulsars entering binary systems.However, there exist both low–mass (e.g. Her X–1, 4U 1626–67) and high–mass (e.g. Cen X–3, SMC X–1) systems, where the neutron star deserves strong accretion and the magnetic field is still large.
A Super-Eddington Wind Model for GRO J1655–40
Authors: Meier David L. 
Published: July 2016

AbstractA model for GRO J1655–40 is described in which the hard X/γ-ray behavior, and long delay between the X/γ and radio outbursts, are explained by processes which occur when the accretion rate approaches and exceeds the Eddington limit. The principal feature of the model is a dense, optically thick, super-Eddington wind ejected from the center of the accretion disk. The wind is responsible for determining the luminosity and spectral evolution of the object and for suppressing the formation of a fast, relativistic jet while the accretion rate is above the Eddington limit.Our model makes use of the “magnetic switch” mechanism we recently discovered with MHD simulations of jet production in magnetized accretion disk coronae. A fast jet can be turned on (or off) by increasing (or decreasing) the Alfvén velocity in the corona relative to a critical value. Examination of models of sub- and super-Eddington disks shows that VA remains below the critical value while the wind is present, but could exceed it when the wind disappears and a hot, optically thin corona forms.