bluuebunny/crossref_metadata_2025_split huggingface dataset:
Identification of Physical Components in Pulsar Emission
Authors: Seiradakis J.H. , Karastergiou A. , Kramer M. , Psaltis D. 
Published: July 2016

AbstractWe have used power spectra analysis on high frequency (1.4 GHz) data, obtained with the Effelsberg 100m radio-telescope in order to investigate the emission characteristics of pulsars. This analysis has not only revealed the prominent periodicities of the fluctuating components, but has also proven a powerful tool for identifying weak and often unresolved components and their longitudinal location within the integrated pulsar profile. Furthermore, close examination of the properties of the fluctuating components indicates physical connections between them, giving new insight to the structure of the emitting region.
A Decade of Low Frequency Pulsar Polarimetry at PRAO: a Review of the Main Results
Authors: Suleymanova Svetlana A. , Pugachev V.D. 
Published: July 2016

AbstractThe main results of the linear polarization measurements of pulsars done at the lowest radio frequencies 40, 60 and 103 MHz are summarized in this paper. We have analyzed 35 integrated polarization profiles and 20 statistical distribution displays and compared them with published high frequency results.
Nanoarcsecond Single-Dish Imaging of the Vela Pulsar
Authors: Macquart J.-P. , Johnston S. , Walker M. , Stinebring D. 
Published: July 2016

AbstractWe have measured the properties of the diffractive scintillation toward the Vela pulsar under the extremely strong scattering conditions encountered at 660 MHz. We obtain a decorrelation bandwidth ofvd= 244±4 Hz and diffractive decorrelation timescale oftdiff= 3.3±0.3s. Our measurement of the modulation indicesm= 0.87±0.003±0.05 andm= 0.93±0.03±0.05 (one For each polarization stream), are at variance with the modulation index of the Vela pulsar obtained at 2.3 GHz by Gwinn et al. (F997)ifthe deviation from a modulation index of unity is ascribed to a source size effect.
Radio Polarimetry Results for Young Southern Pulsars
Authors: Crawford Fronefield , Kaspi Victoria M. , Manchester Richard N. 
Published: July 2016

AbstractWe present radio polarimetry results for nine Southern pulsars. Six of the nine are young, with characteristic ages less than 100 kyr and high spin-down luminosities. All six show significant linear polarization, and we confirm a previously noticed trend in which the degree of linear polarization increases with spin-down luminosity. We have used the rotating vector model to fit the observed position angle data for PSR J1513–5908 (B1509–58). We find that a magnetic inclination angleα&gt; 60° is excluded at the 3σlevel in the fit, and that the geometry suggested by the morphology of an apparent bipolar X-ray outflow is marginally inconsistent with a recent model of the pulsar magnetosphere.
The Mode-Separated Pulse Profiles of Pulsar Radio Emission
Authors: McKinnon Mark M. , Stinebring Daniel R. 
Published: July 2016

AbstractTwo modes of orthogonal polarization are generally observed in the radio emission from pulsars. Essentially all attempts to calculate the average profiles of the individual modes have assumed that the modes occur separately. We have presented evidence, however, that the modes occur simultaneously. Therefore, we believe that “mode-separated” pulse profiles which have been published to date reveal little about the polarization properties of the individual modes.Calculating mode-separated pulse profiles for superposed orthogonal modes is complicated by the unknown polarization properties of the individual modes. However, the simplest model of pulsar radio emission which can explain the wide variety in the emission’s polarization is one in which the individual modes are completely polarized. We use our simple model to compute the average profiles of the orthogonal modes in PSR B0525+21. The total intensity of the two mode profiles resembles the overall pulse profile, and each profile is highly linearly polarized.
Pulsar Polarimetry – New Aspects at High Radio Frequencies
Authors: Hoensbroech Alexis von 
Published: July 2016

AbstractPulsar polarimetry is an important tool for the investigation of the physical processes and the environment in the magnetosphere. However, the great variety of observed polarization states and the few obvious systematics hamper a straightforward interpretation. In this paper it is shown that the polarimetric features of pulsars are much more systematic at high radio frequencies. An analysis of 116 profiles at 4.85 GHz reveals a clear correlation between the degree of polarization andĖ. Also evidence is shown for pulsars with a heavily increasing degree of circular polarization. Further, a basic concept of a simple magnetospheric propagation scenario is presented, which can account for a variety of polarimetric properties of pulsars.
CLYPOS: the Cananea-Ljubljana Young Pulsar Optical Survey
Authors: Carramiñana Alberto , Čadež Andrej , Alvarez César 
Published: July 2016

AbstractThe Cananea-Ljubljana Young Pulsar Optical Survey, or CLYPOS, is an observational study of ≳ 30 known radio pulsars, in search for pulsed optical emission. The survey is being carried out at the 2.12m telescope of the Observatorio Astrofísico Guillermo Haro, near Cananea, Sonora, using the stroboscopic camera of the University of Ljubljana. We restricted the study to young pulsars with declinationδ&gt; −35°, prioritized in terms ofE/d2. Our strategy consists in spending two hours of observing time per pulsar, scanning the whole pulsed-phase interval three times. Further details are given below.
Optical Polarization Measurements of Pulsars
Authors: Wagner Stefan J. , Seifert W. 
Published: July 2016

AbstractWe investigate the polarization characteristics of optical emission from young pulsars. In a first attempt we search for polarization in images without time resolution in order to select suitable candidates for time-resolved studies. Polarization information constrains the nature of the faint optical emission of pulsars and will eventually allow to derive the topology of the field in those areas were optical radiation is emitted. We determine the polarization of the time-integrated optical emission of the SMC pulsar B0540-69 and the Vela pulsar B0833-45. We identify a new candidate optical counterpart for the young pulsar B1509-58 and find that the old candidate is unpolarized. The polarization of these three sources is rather high in view of the assumption that averaging over a putative swing of the polarization angle through 180 degrees will lead to depolarisation in the pulse-averaged signal.We also detect high degrees of polarization in the synchrotron nebula surrounding the LMC pulsar B0540-69, indicating even further similarity to the Crab.
X-ray emission characteristics of pulsars and their nebulae
Authors: Becker Werner 
Published: July 2016

AbstractRecent X-ray observatories like ROSAT, ASCA, RXTE, BeppoSAX and Chandra have achieved important progress in neutron star and pulsar astronomy. The identification of Geminga as a rotation-powered pulsar, the discovery of X-ray emission from millisecond pulsars and the identification of cooling neutron stars are only few of the fascinating results. In the following I will give a brief review on the X-ray emission properties of rotation-powered pulsars and their wind nebulae.
RXTE Observations of the Vela Pulsar: The X-ray-Optical Connection
Authors: Harding Alice K , Strickman Mark S. , Gwinn Carl , McCulloch P. , Moffet D. 
Published: July 2016

AbstractWe report on our analysis of a 300 ks observation of the Vela pulsar with the Rossi X-Ray Timing Explorer (RXTE). The double-peaked, pulsed emission at 2 - 30 keV, which we had previously detected during a 93 ks observation, is confirmed with much improved statistics. There is now clear evidence, both in the spectrum and the light curve, that the emission in the RXTE band is a blend of two separate components. The spectrum of the harder component connects smoothly with the OSSE, COMPTEL and EGRET spectrum and the peaks in the light curve are in phase coincidence with those of the high-energy light curve. The spectrum of the softer component is consistent with an extrapolation to the pulsed optical flux, and the second RXTE pulse is in phase coincidence with the second optical peak. In addition, we see a peak in the 2-8 keV RXTE pulse profile at the radio phase.
The Superluminal Model of Pulsars
Authors: Ardavan H. 
Published: July 2016

AbstractSalient features of the pulsar emission are all consequences of a single property of the source of this radiation: the superluminal nature of the phase speeds with which the outer parts of the distribution pattern of the emitting electric current rotate. Here we outline the principles underlying the superluminal model of pulsars, on which this claim is based, and describe a ground-based experiment currently being built that will be capable of testing,inter alia, the validity of this model.
The Statistics of Radio Pulsars: A Spark Model
Authors: Cheng K.S. , Fan G.L. 
Published: July 2016

AbstractWe investigate pulsar statistics based on theoretical model of radio emission of Ruderman-Sutherland (1975) and the revised spark model of Gil et al. (1999). In the present approach the intrinsic luminosity is no more given by observed relationship betweenLrandP,. Our studies show that R-S &amp; spark model can explain the statistical properties of radio pulsars reasonably well.
A low energy-model for coherent radio emission — the three-liter-pulsar
Authors: Lesch Harald , Kunzl Thomas , Jessner Axel 
Published: July 2016

AbstractWe present a new model for the coherent radio emission of pulsars that succeeds in reproducing observed luminosities at emission heights of 50-100 pulsar radii. Based on energy conservation and propagation effects we apply the concept of a free electron maser (FEM) to the creation of coherent radio emission. With the characteristic frequencyν≃γ2νpe(νpedenotes the plasma frequency andγis the Lorentz factor of the emitting particles) we find that even for the lowest frequencies at which the highest degree of coherence is required only low energy particles (γ≃ 10) with Goldreich-Julian-density are necessary. Because of its low energy budget we call itthree-liter-pulsar.
On the nature of optical emission from radio pulsars
Authors: Malov I.F. , Machabeli G.Z. 
Published: July 2016

There are more than one thousand known radio pulsars, but only 9 of them have detected optical emission (Caraveo 1999). A part of optical emission can be caused by thermal radiation from the hot surface of the neutron star. We shall try to describe the non-thermal component (Kurt et al. 1980) on the base of the synchrotron mechanism, using one-dimensional distribution function of emitting electrons.One of the possible reasons of observed pulsar emission is the cyclotron instability developed in an anisotropic plasma (Sagdeev &amp; Shafranov 1960). To generate transversal (t) waves with the spectrumthe condition of the cyclotron resonance (Kazbegi et al. 1992)must be fulfilled. Hereis the Lorentz-factor of resonance particles,is the drift velocity of particles,ρis the curvature radius of field lines.
On the Nature of the Geminga Pulsar
Authors: Khechinashvili D. , Melikidze G. , Gil J. 
Published: July 2016

AbstractThe model provided that Geminga is an almost aligned pulsar, which is supported by the low-frequency observations. The model explains successfully most of the peculiarities of Geminga radio emission. In the frame of the same geometry we propose a mechanism for the recently detected optical pulsation from that pulsar.
The Pulsar Pair Plasma
Authors: Asseo Estelle , Riazuelo Alain 
Published: July 2016

AbstractThe anisotropic and relativistic features of the pulsar pair plasma are adequately modelled using relativistic one-dimensional Jűttner-Synge distribution functions. The dispersion relation for wave propagation in such a plasma involves coefficients that specifically depend on the distribution function of its particles. An analytical determination of these coefficients allows us to obtain characteristics of quasi-longitudinal waves together with the conditions for the unstable interaction of ultrarelativistic beam and plasma. Similar derivations concern electromagnetic waves.
The Crab pulsar echoes
Authors: Smith F. Graham , Lyne A.G. 
Published: July 2016

AbstractObservations over an eight month period from July 1997 to March 1998 show echoes following the radio pulses, and unusual changes in dispersion measure. We interpret this remarkable and complex event as refraction and dispersion in an ionised shell in the outer part of the Crab Nebula. The shell is remarkably compact; it has a electron density of about 103– 104cm−3and a thickness of about 3 × 1011m. Similar events have been noticed on several other occasions during the continuous monitoring of the Crab pulsar over the past 25 years.
Bow Shocks from Radio Pulsars: Observations of the Guitar Nebula
Authors: Chatterjee Shami , Cordes James M. 
Published: July 2016

AbstractWe present optical observations and radio non-detections of the bow shock nebula associated with the pulsar B2224+65 (the “Guitar Nebula”), and fit an analytic model to the observed bow shock to estimate its inclination and constrain other parameters (distance, pulsar velocity, ISM density). We also test scaling laws for bow shock parameters.
Physical Connections Between Pulsar Outer Magnetospheres and Pulsar Nebulae
Authors: Chiueh Tzihnong 
Published: July 2016

AbstractThe spin-down luminosity together with the morphology of pulsar nebula, such a the Crab, have long been known to imply that the pulsar wind be practically unmagnetized immediately before it impinges onto the nebula. In fact, the condition of low wind magnetization can be shown to further imply that the pulsar outer magnetosphere be strongly distorted, where the toroidal field exceeds the conventionally-assumed dipole field by nearly two orders of magnitude in the outer magnetosphere; the current needed requires the plasma density to exceed the Goldreich-Julian charge density by several orders of magnitude. Such a physical condition can certainly impose a constraint on the candidate mechanisms of non-thermal radio emission, and may also place a constraint on the high-energy, electrode-gap emission mechanisms.
Transient radio emission from PSR B1259–63
Authors: Ball Lewis , Melatos Andrew , Johnston Simon , Skjæraasen Olaf 
Published: July 2016

AbstractThe unique binary pulsar system PSR B1259–63, comprising a radio pulsar in an eccentric orbit about a hot, massive companion star, has been extensively monitored at radio frequencies between 843 MHz and 8.4 GHz during its 1994 and 1997 periastron passages. Unpulsed radio emission was detected for about 100 days around each periastron, varying on time scales as short as a day. We argue that the emission is synchrotron radiation generated as the pulsar passes through the Be-star’s excretion disk just before and just after periastron.
Extreme scattering of pulsars
Authors: Walker Mark A. 
Published: July 2016

AbstractExtreme Scattering Events are radio-wave lensing events caused by AU-sized concentrations of ionised gas. Although they were discovered more than a decade ago we still have no clear picture of the physical nature of the lenses. To discriminate between the various models, we need to amass more information on multiple imaging phenomena. Pulsars are perfect targets for such studies: they offer six- to ten-times the information content of quasar observations, and their small angular sizes make them sensitive to distant lenses. In addition, small source-size means that multiple imaging can be studied even when there is little change in the total source flux, because the (weak) secondary images interfere with the primary and create periodic fringes in the spectrum.
Neutron Star Populations at the Millenium
Authors: Cordes James 
Published: July 2016

AbstractIdentified neutron star (NS) classes evidently are determined by several intertwined features: kinematics of NS at their formation (spin and translational); magnetic field strength; and binary membership. I discuss the well-known classes of isolated and accreting NS while keeping in mind recent discoveries of magnetars, anomalous X-ray pulsars, and long-period radio pulsars. I summarize the results of several likelihood analyses on radio pulsars, which yield information on the velocity distribution, luminosity function, and birth rate of high-field radio pulsars. I review the evidence for the occurrence of momentum kicks at the time of NS birth. Discerning the relationship of the classic radio pulsars to the more exotic classes probably requires careful comparison of magnetic fields, kinematics and birthrates, a program for the next millenium. Exciting discoveries of classic pulsars will also be made: sub-millisecond pulsars, massive binaries in fast orbits and truly hyper-velocity pulsars that shed light on core-collapse processes in supernovae.
Theoretical Implications of the 47 Tuc Pulsars
Authors: Rasio Frederic A. 
Published: July 2016

AbstractTwenty millisecond radio pulsars have now been observed in the globular cluster 47 Tuc. This is by far the largest sample of radio pulsars known in any globular cluster. These recent observations provide a unique opportunity to re-examine theoretically the formation and evolution of recycled pulsars in globular clusters.
New Direct Observational Evidence for Kicks in SNe
Authors: Tauris T. M. , Heuvel E. P. J. van den 
Published: July 2016

We present an updated list of direct strong evidence in favour of kicks being imparted to newborn neutron stars. In particular we discuss the new cases of evidence resulting from recent observations of the X-ray binary Circinus X-1 and the newly discovered binary radio pulsar PSR J1141–6545. We conclude that the assumption that neutron stars receive a kick velocity at their formation is unavoidable (van den Heuvel &amp; van Paradijs 1997).This assumption explains a large variety of observations, ranging from direct observed properties of individual binary pulsars and Be/X-ray binaries to the observed birth rates and dynamical properties of the populations of LMXBs, binary recycled pulsars as well as the motion and distribution of single pulsars. Below we give an updated list in favour of kicks based on the compilation given by van den Heuvel &amp; van Paradijs (1997) – see references therein for details.
On the Existence of an Universal Spin-down Equation for Pulsars
Authors: Alvarez César , Carramiñana Alberto 
Published: July 2016

AbstractThe Taylor expansion of the generalized spin-down equation= −f(v), derives into the multipolar equation= −gv5–rv3−sv), which is used here to study pulsar evolution. The coefficientsg,rand s can be physically associated to gravitational radiation, magnetic dipolar radiation and particle aceleration. The multipolar expansion with constant coefficients cannot describe theP Ṗdiagram in a consistent manner and therefore it is unlikely a generalized equation of the form= −f(v;t) can be used to describe pulsar evolution. A more general form,= −f(v;t) can be investigated giving to the coefficientsg,rand s time dependence. We consider some explicit functional forms forg(t),r(t) ands(t) which are consistent with observational and theoretical constraints.
Heat and charge transport in envelopes of weakly and strongly magnetized neutron stars
Authors: Potekhin Alexander 
Published: July 2016

AbstractThermal and electrical electron conductivities are calculated for a broad range of physical parameters typical for envelopes of neutron stars. An appropriate effective electron-ion scattering potential is used, based on calculations involving modified ion structure factors suggested recently for the treatment of the transport problems in dense Coulomb plasmas. These results are applied to calculation of the thermal structure of neutron-star envelopes.
The Temperature and Cooling Age of t h e White-Dwarf Companion to the Millisecond Pulsar PSR B1855+09
Authors: Bell Jon , van Kerkwijk Marten , Kaspi Vicky , Kulkarni Shri 
Published: July 2016

AbstractWe report on Keck and HST observations of the binary millisecond pulsar PSR B1855+09. We detect its white-dwarf companion and measuremF555W= 25.90 ± 0.12 andmF814W= 24.19 ± 0.11 (Vega system). From the reddening-corrected color we infer a temperatureTeff= 4800 ± 800 K. The companion mass is known accurately from measurements of the Shapiro delay of the pulsar signal,. Given a cooling model, one can use the measured temperature to determine the cooling age. The main uncertainty in the cooling models for such low-mass white dwarfs is the amount of residual nuclear burning, which depends on the thickness of the hydrogen layer surrounding the helium core. For PSR B1855+09, such models lead to a cooling age of ∼10Gyr, which is twice the spin-down age of the pulsar. It may be that the pulsar does not brake (n=3.0) like a dipole rotatingin vacuo. For other pulsar companions, however, ages well over lOGyr are inferred, indicating that the problem may lie with the cooling models. There is no age discrepancy for models in which the white dwarfs are formed with thinner hydrogen layers (&lt; 3 × 10−4M⊙). See van Kerkwijk et al. ApJ (submitted) for more details.
Magnetars
Authors: Thompson Christopher 
Published: July 2016

AbstractI summarize recent observational and theoretical advances in the understanding of the Soft Gamma Repeaters and the Anomalous X-ray Pulsars. Several direct physical arguments point to very strong magnetic fields (B&gt; 10BQED= 4.4 × 1014 G) in SGR outbursts. The connection between these two classes of neutron stars is examined. Their persistent X-ray emission and spindown behavior are interpreted in the magnetar model, where a decaying magnetic field dominates all other sources of energy for radiative and particle emission. The response of a magnetic field to the violent motions in a supernova core is also examined, with a focus on mechanisms that may impart unusually large kicks.
Bumpy Spin-Down of Anomalous X-Ray Pulsars: The Link with Magnetars
Authors: Melatos A. 
Published: July 2016

AbstractIt is argued that bumps in the timing histories Ω(t) of the anomalous X-ray pulsars (AXPs) IE 1048.1-5937 and IE 2259+586 are the signature of a magnetar undergoing radiative precession, wherein the hydromagnetic deformation of the neutron star couples to an oscillating component of the vacuum-dipole radiation torque to produce an anharmonic wobble with periodτpr∼ 10 yr. An analysis of Euler’s equations of motion for a biaxial magnet reproduces the amplitude and recurrence time of the bumps for IE 1048.1-5937 and IE 2259+586, predicts Ω(t) for the next 20 years for both objects, and predicts a testable statistical relation betweendΩ/dtandτprfor the AXP population overall. Radiative precession of soft gamma-ray repeaters is also discussed, together with implications for the internal (e.g. viscosity) and magnetospheric (e.g.e+e−pair currents) properties of magnetars.
New ASCA Observations of two Anomalous X-ray Pulsars
Authors: Paul B. , Kawasaki M. , Dotani T. , Nagase F. 
Published: July 2016

AbstractNewASCAobservations of two anomalous X-ray pulsars (AXP) 4U 0142+61 and 1E 1048.1-5937, made in 1998, when compared to earlier observations in 1994 show remarkable stability in the intensity, spectral shape and pulse profile. The energy spectra consist of two components, a power-law and a blackbody emission from the neutron star surface. In IE 1048.1-5937, we have identified three epochs with different spin-down rates and discuss its implications for the magnetar hypothesis of the AXPs. We also note that the spin-down rate and its variations in IE 1048.1-5937 are much larger than what normally can be produced by an accretion disc with very low mass accretion rate corresponding to its low X-ray luminosity.