Invited Review Talks

JD02-1  Radio Emission Properties of Pulsars

R N Manchester

ATNF - CSIRO, Sydney, Australia

Recent observational results on the radio emission properties of pulsars are reviewed.

JD02-2   New Results on Rotating Radio Transients

M.A. McLaughlin

West Virginia University, Morgantown, United States

We discuss a new population of radio-bursting neutron stars discovered in a large scale search for transient radio sources. Unlike normal radio pulsars, these objects, which we call Rotating RAdio Transient (or RRATs), cannot be detected through their time-averaged emission and are radio sources for typically less than 1 second per day. The spin periods of these objects range from 0.4 to 7 seconds, with period derivatives indicating that at least one RRAT has a magnetar-strength magnetic field. We will detail recent developments, including X-ray observations and observations with more sensitive radio telescopes, and discuss how these objects are related to other neutron star populations. We will also describe the implications of this new source class for neutron star population estimates.

JD02-3  Isolated Neutron Stars in optical and X-rays : room for discovery

P.A. Caraveo

INAF-IASF, Milano, Italy

The multiwavelength behaviour of isolated neutron stars evolves as they age.

In particular, the X-ray and optical emissions allow us to follow the shift from the non-thermal regime, typical of young objects, to a mostly thermal one, typical of older specimen.

New observations unveil tale-telling details both on young and old objects, reminding us that a lot remains to be discovered in the complex INS family tree.

JD02-4   Gamma-ray and TeV Emission Properties of Pulsars and Pulsar Wind Nebulae

OC. DE Jager

North-West University, Potchefstroom, South Africa

Introduction: Although more than 1,600 radio pulsars have been discovered, only a few have been detected in the gamma-ray band. This is not because they are intrinsically faint, but because the pulsed component seems to cut off below about 30 GeV (the EGRET range), where the sensitivity was severely limited. However, ground-based atmospheric Cerenkov telescopes operating above 100 GeV (the Very High Energy or VHE domain), have both good sensitivity and good angular resolution to resolve several pulsar wind nebulae (PWN) in the VHE gamma-ray domain.

Methods: This will be a review talk summarising the progress to date on pulsar and pulsar wind nebula observations and theory.

Results and Conclusions: Since gamma-ray observations below 30 GeV have been limited by poor sensitivity, an instrument like GLAST should be able to resolve the pulsed component of a significant fraction of radio pulsars. This talk will show how the discovery potential of GLAST will be limited for fainter sources in the absence of contemporary radio pulsar parameters. This calls for the introduction of wide field-of-view radio pulsar monitors like KAT to resolve this problem. Most progress on PWN in the gamma-ray domain was made by the HESS telescope system in Namibia. In this case we progressed to the level where VHE Gamma-ray Astronomy is taking the lead at all wavelengths (radio, IR, optical, X-ray and gamma-ray) in the identification and understanding of new PWN. We will show how the spin history of the PWN is more relevant to such VHE observations rather than X-rays, although the latter probe the more recent history of PWN evolution. We will then show how these complementary wavebands can be combined to obtain new information about aspects such as the birth periods of pulsars and conversion efficiency of spin-down power to injected ultra-relativistic electrons.

JD02-5   Pulsar Timing and its Future Perspective

D. J. Nice

Bryn Mawr College, Bryn Mawr, Pennsylvania, United States

I will survey the present state of radio pulsar timing and prospects for future progress.  In recent years, pulsar timing experiments have grown rapidly in both quantity and quality, yielding new tests of gravitation, new constraints on the structure of neutron stars, new insight into neutron star kicks and the dynamics of supernovae, and better understanding of the evolution of compact objects in the Galaxy.

The tremendous success of recent pulsar surveys, especially those with the Parkes multibeam receiver, have vastly increased the number of known pulsars.  Ongoing surveys at Arecibo and elsewhere promise to continue yielding new and exciting pulsars.  At the same time, advances in instrumentation--including the development of wide-band receivers and spectrometers and the routine use of software coherent dedispersion data acquisition systems--are increasing the precision attainable in timing experiments.  State of the art timing precision is now around 100 nanoseconds.  I will discuss limitations on present timing experiments and prospects for future improvements.

JD02-6   Radio emission theories of pulsars

V Usov

Weizmann Institute, Rehovot, Israel

Pulsar magnetospheres contain a multi-component, strongly magnetized, relativistic plasma. The present review is mainly concerned with generation and propagation of coherent radio emission in this plasma, emphasizing reasons why up to now there is no commonly-accepted model of the radio emission of pulsars. Possible progress in our knowledge about the mechanism of the pulsar radio emission is discussed.

JD02-7   Theory of High Energy Emission from Pulsars

KS Cheng

Department of Physics, University of Hong Kong, Hong Kong, China

In this talk we briefly review various models of high energy emission from pulsars. In particular we point out that the light curves can provide important constraints in the radiation emission regions and the location of the accelerators (gaps). Furthermore, the energy dependent light curves and phase-dependent spectrum cannot be explained in terms of simple two dimensional models, three dimensional models must be used to explain the full detail of the observed data. We will present a three dimensional outer gap model to study the magnetospheric geometry, the light curve and the phase-resolved spectra of the Crab pulsar. Using a synchrotron self-Compton mechanism, the phase-resolved spectra with the energy range from 100 eV to 10 GeV of the Crab pulsar can also be explained. We will also use the observed polarization angle swing of optical photons to determine the viewing angle.

JD02-8    On The Theory of Radio And High Energy Emission From Pulsars: Where To Go?

J. Arons

University of California, Berkeley, United States

I discuss recent progress in the theory of the energy loss from pulsars, focusing on the advances in force free models of the magnetopshere and on dissipation in the wind, with implications of the latter for unusually models of pulsed emission.  I also draw attention to the implications the new global magnetopshere models may have may have for the generation of parallel electric fields, and the implications of these for high energy emission, radio emission and the global mass loss rate through pair creation. I discuss parallel electric field formation and consequences for photon emission in scenarios with self-consistent currents, which are rather different from the standard gap models with their starvation electric fields.  Finally, I remark on the importance of radiation transfer effects in unravelling the continuing mystery of pulsar radio emission.

JD02-9   Cooling Neutron Stars: the present and the future

S. Tsuruta

Montana State University, Bozeman, United States

Recent years have seen some significant progress in theoretical studies of physics of dense matter. Combined with the observational data now available from the successful launch of Chandra and XMM/Newton X-ray space missions as well as various lower-energy band observations, these developments now offer the hope for distinguishing various competing neutron star thermal evolution models. For instance, the latest theoretical and observational developments may already exclude both nucleon and kaon direct Urca cooling.  In this way we can now have a realistic hope for determining various important properties, such as the composition, superfluidity, the equation of state and stellar radius. These developments should help us obtain deeper insight into the properties of dense matter.

JD02-10   A Decade of Surprises from the Anomalous X-ray Pulsars

S. M. Ransom

NRAO, Charlottesville, VA, United States

A decade ago, the defining characteristics of the Anomalous X-ray Pulsars (AXPs) included slow spin periods (5-9 s), relatively soft but constant X-ray luminosities in the range of 1035-1036 erg/s, and steady spin-down rates.   The X-ray luminosities are too large to be powered by pulsar spin-down, and given the lack of evidence for accretion, are thought to be caused by the decay of ~1014-1015 G magnetic fields (i.e. the “magnetar” theory as proposed by Thompson and Duncan).  Within the past decade, though, detailed X-ray monitoring observations have shown that these sources are anything but “constant” and “steady”.  Timing noise, glitches, X-ray bursts, and pulse profile and pulsed flux variations are now known to be relatively common in these sources.  In addition, at least one recently discovered AXP, XTE J1810-197, is a full-fledged transient object.  Detections in the optical and infra-red (including pulsations) and recent hard X-ray observations have complicated our views of their emission mechanisms.   Finally, very recent detections of magnetar-like radio pulsars, as well as strong (and transient) radio pulsations from  XTE J1810-197, show that these sources are linked (at least in some way) with the much more common radio pulsars.

JD02-11  Pulsars and Gravity

I. H. Stairs

University of British Columbia, Vancouver, Canada

Radio pulsars are superb tools for testing the predictions of strong-field gravitational theories.  I will describe the currently achieved tests of equivalence principles and of predictions for relativistic binary orbital parameters, as well as limits on a gravitational-wave background, and will discuss future prospects in each of these areas.

JD02-12  Future radio observatories for pulsar studies

M. Kramer

University of Manchester, Jodrell Bank Observatory, Jodrell Bank, United Kingdom

Over the next decade, radio astronomers will have new, exciting instruments available to answer fundamental questions in physics and astrophysics. Without doubts, new discoveries will be made, revealing new objects and phenomena. We can expect pulsar astronomers to receive their fair share. In many respects, the field of pulsar astrophysics will change, as the science will not simply be a continuation of what has been done so successfully over the past 40 years. Instead, the huge number of pulsars to be discovered and studied with an unprecedented sensitivity will provide a step forward into exciting times. Instruments like the Low Frequency Array (LOFAR), the Square Kilometre Array (SKA) and their powerful pathfinder telescopes will enable a complete census of Galactic pulsars, ultimate tests of gravitational physics, unique studies of the emission process and much more. This talk will demonstrate the potential of the future instruments by presenting highlights of the science to be conducted.

JD02-13  Future optical and X-ray observatories for pulsar studies

W. Becker

Max-Planck Institut für extraterr. Physik, Garching, Germany

Optical and X-ray astronomy has made great progress in the past several years thanks to telecopes with larger effective areas and greatly improved spatial, temporal and spectral resolutions. The next generation instruments like XEUS, Constellation-X, Simbol-X, eROSITA, the James Webb Space Telescope and the ESOs Extremely Large optical Telescope are supposed to bring again a major  improvement in sensitivity. The purpose of my talk is to summarize the future plans for X-ray and optical telescopes with the emphasis of their application for pulsar and neutron star astronomy.

JD02-14  Future Gamma-ray and TeV Observatories for Pulsar Searches

D.A. Smith

CENBG/IN2P3/CNRS, Gradignan, France

GeV measurements of pulsar lightcurves versus energy provide information on beam geometry, and spectral cut-offs give insights into the particle acceleration region(s) around the neutron star. The two together can help build a better picture of neutron star populations in the galaxy. We are on the verge of instrumental break-throughs that promise to increase the sample of measured objects by ~10. This talk describes instruments for multi-GeV pulsations for the next few years. We’ll cover developments of ground-based atmospheric Cherenkov detectors, review AGILE’s prospects, and then focus on the LAT (Large Area Telescope) on GLAST, including sensitivity estimations. Accurate radio ephemeredes can greatly enhance the gamma-ray pulsar science, and we will describe efforts to build a large ephemeredes database.

Poster Contributions

    JD02-15            Poster

    Effects of core magnetic fields in evolution of binary neutron stars

    Taghi Mirtorabi, Atefeh Javadi Khasraghi, Shohre Abdolrahimi

    Alzahra, Tehran, Iran

    The standard scenario for evolution in a close binary system in which the neutron star pass through four evolutionary phases ( isolated star, propeller,  wind accretion and Roch lobe accretion)  was employed to calculate transport of orbital angular momentum to the neutron star or loss of angular momentum from the whole system.

    The evolution of  core magnetic field of  neutron stars  in  close binary systems with a low mass main sequence companion  is explored. Assuming the core as a type II superconductor so the magnetic flux can be transported as quantized fluxoids, calculation have been performed  to determine magnetic filed decay  and its interaction with the mater accreted from the companion.

    The evolution of semi major axis of the binary in a time scale of 10^9 year comparable with the main sequence life time of the low mass companion was also investigated.

    JD02-16            Poster

    External Electromagnetic Fields of Slowly Rotating Relativistic Magnetized NUT Stars

    B.J. Ahmedov, A.V. Khugaev

    1Institute of Nuclear Physics, Tashkent, Uzbekistan, 2Ulugh Beg Astronomical Institute, Tashkent, Uzbekistan

    Analytic general relativistic expressions for the electromagnetic fields external to a slowly-rotating magnetized NUT star with nonvanishing gravitomagnetic charge  have been presented. Solutions for the electric and magnetic fields have been found after separating the Maxwell equations in the external background spacetime of a slowly rotating NUT star into angular and radial parts in the lowest order approximation in specific angular momentum and NUT parameter . The relativistic star is considered isolated and in vacuum, with different models for stellar magnetic field: i) monopolar magnetic field and ii) dipolar magnetic field aligned with the axis of rotation.

    It has been shown that the general relativistic corrections due to the dragging of reference frames and gravitomagnetic charge are not present in the form of the magnetic fields but emerge only in the form of the electric fields. In particular, it has been obtained that the frame-dragging and gravitomagnetic charge provide an additional induced electric field which is analogous to the one introduced by the rotation of the star in the flat spacetime limit.

    JD02-17            Poster

    PSR J0538+2817 As The Remnant Of The First Supernova Explosion In A Massive Binary

    V.V. Gvaramadze

    Sternberg Astronomical Institute, Moscow, Russia

    It is generally accepted that the radio pulsar PSR J0538+2817 is associated with the supernova remnant (SNR) S147. The only problem for the association is the obvious discrepancy (Kramer et al. 2003) between the kinematic age of the system of ~30 kyr (estimated from the angular offset of the pulsar from the geometric center of the SNR and pulsar's proper motion) and the characteristic age of the pulsar of  ~600 kyr. To reconcile these ages one can assume that the pulsar was born with a spin period close to the present one (Kramer et al. 2003; Romani & Ng 2003).

    We propose an alternative explanation of the age discrepancy based on the fact that PSR J0538+2817 could be the stellar remnant of the first supernova explosion in a massive binary system and therefore could be as old as indicated by its characteristic age. Our proposal implies that S147 is the diffuse remnant of the second supernova explosion (that disrupted the binary system) and that a much younger second neutron star (not necessarily manifesting itself as a radio pulsar) should be associated with S147. We use the existing observational data on the system PSR J0538+2817/SNR S147 to suggest that the progenitor of the supernova that formed S147 was a Wolf-Rayet star (so that the supernova explosion occurred within a wind bubble surrounded by a massive shell) and to constrain the parameters of the binary system. We also restrict the magnitude and direction of the kick velocity received by the young neutron star at birth and find that the kick vector should not strongly deviate from the orbital plane of the binary system.

    JD02-18            Poster

    Ensemble Pulsar Time Scale

    A.E. Rodin

    Pushchino Radio Astronomy Observatory, Pushchino, Russia

    Purpose of this work is to construct an algorithm of a new astronomical time scale based on the rotation of pulsars, which has comparable accuracy with the most precise terrestrial time scale TT.

    This algorithm is based on the Wiener optimal filtering method and allows separating contributions to the post-fit pulsar timing residuals of the atomic clock used in pulsar timing and spin variations of pulsar itself. The optimal filters are constructed with use of the cross and auto covariance functions (in time domain) or auto and cross power spectra (in frequency domain) of the post-fit timing residuals of pulsars participating in construction of the ensemble time scale..

    The algorithm is applied to the timing data of millisecond pulsars PSR B1855+09 and B1937+21 (Kaspi et al. 1994) and allowed to obtain the corrections of UTC scale relative to ensemble pulsar time scale PTens. Comparison of the differences UTC – PTens   and UTC – TT displays significant correlation between them at level 0.79. Subsequent analysis of TT – PTens shows that TT coincides with PTens within 0.40+/-0.17 mcs and has fractional stability 10^-15 at 7 years time interval.

    Relatively close angular distance (15.5 degrees) on the sky between these pulsars gives grounds to expect that there is a correlated signal in the post-fit timing data caused by the stochastic gravitational wave background (GWB). A new limit of the fractional energy density of GWB based on the difference TT – PTens were established to be Omega_g h^2 ~ 2*10^-10. This new value is by one order lower than previously published one owing to application of the new algorithm that separates the proper pulsars spin and local atomic standard variations.

    JD02-19            Poster

    Comparison of Giant Radio Pulses in Young Pulsars and Millisecond Pulsars

    A. Slowikowska1, A. Jessner2, G. Kanbach1, B. Klein2

    1MPE, Garching, Germany, 2MPIfR, Bonn, Germany

    Pulse-to-pulse intensity variations are a common property of pulsar radio emission. For some of the objects single pulses are often 10-times stronger than their average pulse. The most dramatic events are so called giant radio pulses (GRPs). They can be 1000-times stronger than the regular single pulses from the pulsar. Giant pulses are a rare phenomenon, occurring in very few pulsars which split into two groups. The first group contains very young and energetic pulsars like the Crab pulsar, and its twin in the LMC (PSR B0540-69), while the second group is represented by old, recycled millisecond pulsars like PSR B1937+21, PSR B1821-24, PSR B1957+20, and PSR J0218+4232 - the only millisecond pulsar detected in gamma-rays. We compare the characteristics of GRP's for these two pulsar groups. In particular, we focus on the flux distributions of GRPs. Moreover, our latest findings of new features in the Crab GRPs are presented. Analysis of our Effelsberg data at 8.35~GHz shows that GRPs do occur in all phases of its ordinary radio emission, including the phases of the two high frequency components (HFCs) visible only between 5 and 9~GHz. This suggests that a similar emission mechanism may be responsible for the main pulse, the inter pulse and the HFCs. Finally, we discuss the similarities and differences between both groups of pulsars  in the context of timing, spectral and polarisation properties of these pulsars. We also try to answer the question why pulsars belonging to so different classes do show the same giant radio emission phenomena.

    JD02-20            Poster

    Integral IBIS and JEM-X Observations of PSR B0540-69

    A. Slowikowska1, G. Kanbach1, J. Borkowski2, W. Becker1

    1MPE, Garching, Germany, 2CAMK, Torun, Poland

    The high-energy pulsar PSR B0540-69 in the Large Magellanic Cloud (d~49.4 kpc), embedded in a synchrotron plerion in the centre of SNR 0540-69.3 is often referred to as an extragalactic 'twin' of the Crab pulsar. Its pulsed emission has been detected up to about 48 keV so far. We present the results from our search for PSR B0540-69 up to 300 keV in the 1 Ms INTEGRAL data. INTEGRAL was pointed to the LMC during 6 revolutions in January 2003, and 3 revolutions in January 2004. The events used for timing and spectral analysis of the source come from the IBIS/ISGRI and JEM-X detectors. Moreover, we describe in details our data analysis technique used for this weak source.

    JD02-21            Poster

    Plasma Modes Along Open Field Lines of Neutron Star Endowed with Gravitomagnetic NUT Charge

    B.J. Ahmedov1, V.G. Kagmanova2

    1Institute of Nuclear Physics, Tashkent, Uzbekistan, 2Ulugh Beg Astronomical Institute, Tashkent, Uzbekistan

    Electrostatic plasma modes along the open field lines of a rotating neutron star endowed with gravitomagnetic charge or NUT parameter have been considered. Goldreich-Julian charge density in general relativity is analyzed for the neutron star with nonzero NUT parameter. It is found that the charge density is maximum at the polar cap and remains almost the same in a certain extended region of the pole. For a steady state Goldreich-Julian charge density we found the usual plasma oscillation along the field lines; plasma frequency resembles the gravitational redshift close to the Schwarzschild radius. We study the nonlinear plasma mode along the field lines. The equation contains a term that describes the growing plasma modes near Schwarzschild radius in a black hole environment. The term vanishes with the distance far away from the gravitating object. For initially zero potential and field on the surface of a neutron star, Goldreich-Julian charge density is found to create the plasma mode, which is enhanced and propagates almost without damping along the open field lines of magnetized NUT star.

    JD02-22            Poster

    The Drift Model of Magnetars

    I.F. Malov1, G.Z. Machabeli2

    1Lebedev Physical Institute, Pushchino, Russia, 2Abastumani Astrophysical Observatory, Tbilisi, Georgia

    It is shown that the drift waves near the light cylinder can cause the modulation of emission with periods of order several seconds. These periods explain the intervals  between successive pulses observed in "magnetars" and radio pulsars with long periods. The model under consideration  gives the possibility to calculate real rotation periods of host neutron stars. They are less than 1 sec for the investigated objects. The magnetic fields at the surface of the neutron star are of order 1011 –1013 G and equal to the fields  usual for known radio pulsars.

    JD02-23            Poster

    Substellar companions around neutron stars

    B. Posselt2, R. Neuhäuser2, F. Haberl1

    1Max-Planck-Institut für extraterrestrische Physik, Garching, Germany, 2Astrophysikalisches Institut und Universitäts-Sternwarte, Jena, Germany

    Planets or substellar companions around neutron stars can give valuable insights into a neutron star's formation history considering for example birth kicks or fallback disks. They may also help to derive neutron star masses which would be very welcome especially if the radius can be derived by other means as for the radio-quiet X-ray thermal neutron stars. Currently there are two planetary systems around millisecond pulsars known. They have been found by the pulse timing technique which is most sensitive to old  millisecond pulsars. Some of the formation theories can already be ruled out for these systems. However, statistics are very poor and other search techniques are needed to cover also young, even radio-quiet neutron stars.

    We will present first results of our direct imaging search for substellar companions around the closest and youngest neutron stars started three years ago with ESO's VLT. Among the objects is the famous RX J1856.5-3754 for which a substellar object could help to constrain the equation of state as the radius has been already previously derived by its X-ray thermal emission.

    JD02-24            Poster

    Detection Of The Individual Pulses Of The Pulsars В0809+74; В0834+06; В0950+08; В0943+10; В1133+16 At Decameter Wave Range

    O.M. Ulyanov1, V.V. Zakharenko1, A.A. Konovalenko1, A. Lecacheux2, C. Rosolen2, H.O. Rucker3

    1Institute of Radio Astronomy of NASU, Kharkov, Ukraine, 2L' Observatoire de Paris, Paris, France, 3Space Research Institute of the Austrian Academy of Sciences, Graz, Austria

    Radio emission of single pulses for five pulsars (PSR В0809+74; В0834+06; В0950+08; В0943+10; В1133+16) was found at frequencies 18-30 MHz.  The radio emission is caused by the strong subpulses that have peak intensity of more than 20 times larger than peak intensity of average profiles. The intensity of single pulses has a strong variation in frequency and time. The probability of detection of the anomalous intense pulses does not exceed several percents at Decameter wave range. Usually such pulses are detected in short series (not more than 10 pulses).  Typical band values of detection for the pulses with anomalous intensities lie in the range from 0.2 to 0.5 octaves.

    JD02-25            Poster

    An Analytical Description of Low-Energy Secondary Plasma Particle Distribution in Pulsar Magnespheres

    V. M. Kontorovich, A. B. Flanchik

    Institute of Radio Astronomy, National Academy of Sciences of Ukraine, Kharkov, Ukraine

    A simple analytical approximation of the form of low-energy cut-off of the secondary particle distribution is proposed. This approximation is acceptable for describing the known cascade numerical simulation [1]. The distribution form and maximum position as function of pulsar parameters have been found theoretically by considering the curvature radiation process and the electron-positron pairs production [2, 3]. An influence of synchrotron radiation [4] on the form and maximum of the low-energy distribution is considered.

    [1]  Harding A. K., Daugherty J. K., ApJ, 252, 337, 1982.

    [2]  Beskin V. S., Usp. Fiz. Nauk 169, 1169, 1999.

    [3] Malov I. F., Radiopulsars, Moscow, Nauka, 2004, 192 p.

    [4] Gurevich A. V., Isomin Ya. N., Zh. Eksp. Teor. Fiz. 89, 3, 1985.

    JD02-26            Poster

    Timing Irregularities and the Neutron Star Stability

    J.O. Urama

    University of Nigeria, Nsukka, Nigeria

    Observations show that the different manifestations of neutron stars exhibit measurable departures from the predicted slow down. This has been largely attributed to rotational irregularities – timing noise, glitches, and precession. Here, We present an analysis of the regular spin-down and jump parameters for a combined set of the pulsars (radio, optical, x-ray and gamma-ray) and magnetars. We attempt to quantify the stability of neutron stars, in general.

    JD02-27            Poster

    Force-free pulsar magnetosphere

    A.N. Timokhin

    Sternberg Astronomical Institute, Moscow, Russia

    I discuss properties of a force-free pulsar magnetosphere and address the role of electron-positron cascades in determining a particular configuration among other possible force-free magnetospheric configurations. I report on results of high resolution numerical simulations of the force-free magnetosphere of aligned rotator and analyse in details properties of an aligned pulsar. I argue that the closed field line zone should grow with time slower than the light cylinder; this yield the pulsar breaking index less than 3. However, models of aligned rotator magnetosphere with widely accepted configuration of magnetic field, when the last closed field line lies in equatorial plane at large distances from pulsar, have serious difficulties. I discuss solutions of this problem and argue that in any case, also for inclined pulsar, energy losses should evolve with time differently than it is predicted by the magnetodipolar formula and the pulsar breaking index should be different from the "canonical" value equal to 3.

    JD02-28            Poster

    Crab pulsar optical photometry and spectroscopy with microsecond temporal resolution

    G. Beskin1, S. Karpov1, V. Plokhotnichenko1, V. Debur1, A. Biryukov2, D. Badjin2, M. Redfern3, A. Shearer3

    1Special Astrophysical Observatory of Russian Academy of Sciences, Nizhnij Arkhyz, Zelenchukskaya, Russia, 2Sternberg Astronomical Institute of Moscow State University, Moscow, Russia, 3National University of Ireland, Galway, Ireland

    The results of fast photometry and spectroscopy of the Crab pulsar with microsecond temporal resolution are presented. The observations have been performed on William Hershel 4-m and BTA 6-m telescopes using APD avalanche photon counter and PSD panoramic photon imager.

    The stability of the optical pulse is analysed and the search for the variations of the pulse shape along with its arrival time stability is performed. Upper limits on the possible short time scale free precession of the pulsar and the stochastic variable optical emission component are placed. The results of the low resolution (~300 angstrom) phase-resolved spectroscopy of the pulsar emission are discussed, first of all – the distinction of the spectra of pulses and off-pulse phase intervals.

    JD02-29            Poster

    Discovery of a large time scale cyclic evolution of radio pulsars rotational frequency

    G. Beskin1, A. Biryukov2, S. Karpov1

    1Special Astrophysical Observatory of Russian Academy of Sciences, Nizhnij Arkhyz, Zelenchukskaya, Russia, 2Sternberg Astronomical Institute of Moscow State University, Moscow, Russia

    The recent massive measurements of  pulsar frequency second derivatives have shown that they are 100-1000 times larger than expected for standard pulsar slowdown low. Moreover, the second derivatives as well as braking indices are even negative for about half of pulsars. We explain these paradoxical results on the basis of the statistical analysis of the rotational parameters (frequency, its first and second derivatives) of the subset of 295 pulsars taken mostly from the ATNF database. We have found strong correlation of second and first frequency derivatives either for positive (correlation coefficient r~0.9) and negative (r~0.85) values of second derivative, and of the frequency and and its first derivative (r~0.7). We interpret these dependencies as evolutionary ones due to the first frequency derivative being nearly proportional to the characteristic age. The derived statistical relations as well as "anomalous" values of the second frequency derivative are well explained in the framework of the simple model of cyclic evolution of the rotational frequency of the pulsars. It combines the secular change of the rotational parameters according to the power law with braking index n~5 and harmonic oscillations of 100--1000 years period with an amplitude from 10-3 Hz for young pulsars to 10-10 Hz for elder ones. The physical nature of these cyclic variations of the rotational frequency may be similar to the well-known red timing noise, however, with much larger characteristic time scale.

    JD02-30            Poster

    Abnormal Phases in Nuclear Matter in Supernova core collapse model

    D.J. Bora, H.L. Duorah, K. Duorah

    Gauhati university, Guwahati, India

    The role of abnormal phases in nuclear matter on the basis of the well-known Lee-Wick theory is studied for the determination of the shock strength at the core bouncing of type II supernova. Relativistic equation for collapse beyond nuclear density with a still stronger magnetic field is developed to study the effect of appearance of the abnormal phases. This leads to the softening of the equation of state giving rise to strong shock. The magnetar thus formed can be a store-house of many high energy events including rapid gamma-ray bursts. A strong magnetic field beyond some critical value sometimes can exponentially accelerate certain reactions  producing rapid bursts of energy. Some seismic events on the solidified crusts of magnetars can also be alluded  for the short gamma-ray burst discovered in December 2004 at the site of SGR 1806-20.

    JD02-31            Poster

    Instant Radio Spectra of Giant Pulses from the Crab Pulsar Over Decimeter to Decameter Wave Band

    M.V. Popov1, A.D. Kuzmin2, O.M. Ulyanov3, A.A. Deshpande4, A.A. Ershov2, V.I. Kondratiev1, S.V. Kostyuk1, B.Ya. Losovsky2, V.A. Soglasnov1, V.V. Zakharenko3

    1Astronomy Space Center FIAN, Moscow, Russia, 2Pushchino Radio Astronomy Observatory ASC FIAN, Pushchino, Russia, 3Institute of Radio Astronomy of NAS, Kharkov, Ukraine, 4Raman Research Institute, Bangalore, India

    We present results of simultaneous multifrequency observations of giant radio pulses (GPs) from the Crab pulsar PSR B0531+21 at frequencies of 23, 111 and 600 MHz. For the first time GPs were detected at such low frequency as 23 MHz. Among 45 GPs detected in the overall observations time with 600 MHz, 12 GPs were identified as simultaneous ones at 600 and 23 MHz. At 111 MHz among 128 GPs detected in the overall observations time with 600 MHz, 21 GPs were identified as simultaneous ones at 600 and 111 MHz. Spectral indexes for the power-law frequency dependence of GPs energy were enclosed between -3.1 and -1.6. Mean spectral index equals to -2.7 ± 0.1 and is the same for both frequency combinations 600-111 MHz and 600-23 MHz.

    A big scatter in values of the individual spectral indexes and a large number of unidentified giant pulses, indicate that a real form of spectra of individual giant pulses does not follow a simple power law. The shape of giant pulses at all three frequencies is governed by the scattering of radio waves on the inhomogeneities of the interstellar plasma. The pulse scatter broadening and their frequency dependence was measured as tSC=20(n/100)-3.5±0.1 ms, where frequency n is in MHz.

    JD02-32            Poster

    Pulsar Nulling Quantitative Analysis

    J.H. Seiradakis, K. Lazaridis

    University of Thessaloniki, Thessaloniki, Greece

    Using long sequences of single pulses we have analyzed the nulling behaviour of several pulsars. Each pulsar has been characterized by a "nulling parameter", which represents the average length of consecutive null pulses and a "nulling max" parameter, which represents the maximum length of consecutive null pulses. These two parameters have been compared to other pulsar parameters. Some interesting correlations have been derived.

    JD02-33            Poster

    Eclipse Study Of The Double Pulsar

    R. P. Breton1, V. M. Kaspi1, M. A. McLaughlin2, S. M. Ransom3, M. Lyutikov5, M. Kramer6, F. Camilo4, I. H. Stairs5, R. Ferdman5

    1McGill University, Montreal, Canada, 2West Virginia University, Morgantown, United States, 3National Radio Astronomy Observatory, Charlottesville, United States, 4Columbia University, New York, United States, 5University of British Columbia, Vancouver, Canada, 6University of Manchester, Macclesfield, United Kingdom

    The double pulsar system PSR J0737-3039 offers an unprecedented opportunity for studying General Relativity and neutron-star magnetospheres. This system has a favourable orbital inclination such that the millisecond pulsar, "A", is eclipsed when its slower companion, "B", passes in front. High time resolution light curves of the eclipses reveal periodic modulations of the radio flux corresponding to the fundamental and the first harmonic of pulsar B spin frequency. Eclipse modeling is highly sensitive to the geometrical configuration of the system and thus provides a unique probe for parameters like the inclination angle of pulsar "B" spin axis as well as their time evolution due to relativistic effects. We report on detailed fitting of the pulsar A eclipse light curves to a model that includes, for pulsar B, a simple dipolar magnetic field. We find that the eclipses can be reproduced very well, and we obtain precise measurements of pulsar B's orientation in space. We report on a search for secular changes caused by geodetic precession of pulsar B's spin axis.

    JD02-34            Poster

    Observations of southern pulsars at high radio frequencies

    A. Karastergiou1, S. Johnston2

    1IRAM, St'Martin d'Heres, France, 2ATNF, Epping, Australia

    We have observed a number of pulsars at 1.4, 3.1 and 8.4 GHz in full polarization at the Parkes radio-telescope. Our main objective was to study the frequency evolution of polarization by means of new high quality polarization data at high frequencies. Average polarization profiles with high time resolution to update already existing previous observations were also obtained. We have provided a detailed description of a total of 97 polarization profiles at the 3 aforementioned frequencies. This relatively large sample has given us the opportunity to study effects related to the linear and circular polarization as well as the polarization position angle. We find evidence that

    1) a simple model where two orthogonal polarization modes with competing spectral indices can account for many observational properties of the linear polarization and total power,

    2) the position angle dependence on frequency depends on the different relative strength of profile components at different frequencies,

    3) young, energetic pulsars remain highly polarized at high frequencies, and

    4) highly polarized components may originate from higher up in the pulsar magnetosphere then unpolarized components.  We present here a summary of these results.

    JD02-35            Poster

    Pulsar Braking Indices

    Altan Baykal, Ali Alpar

    1Middle East Technical University, Ankara, Turkey, 2Sabancı University, Istanbul, Turkey

    Almost all pulsars with anomalous positive second derivative of angular acceleration measurements (corresponding to anomalous braking indices in the range 5<n<100), including all the pulsars with observed large glitches ( ) as well as post glitch or intergiltch second  measurement obey the scaling between  and glitch parameters originally noted in the Vela pulsar. Negative second derivative values can be understood in terms of glitches that were missed or remained unresolved. We discuss the glitch rates and a priori probabilities of positive and negative braking indices according to the model developed for the Vela pulsar. This behaviour supports the universal occurrence of a nonlinear dynamical coupling between the neutron star crust and an interior superfluid component.

    JD02-36            Poster

    Electrodynamics Of Pulsar's Electrospheres

    J.A. Petri

    Max-Planck-Institut für Kernphysik, Heidelberg, Germany

    We present a self-consistent model of the magnetosphere of inactive, charged, aligned rotator pulsars with help on a semi-analytical and numerical algorithm. The only free parameter is the total charge of the system.  This "electrosphere" is stable to vacuum breakdown by electron-positron pair production.  However, it appears to be unstable to the so-called ``diocotron'' instability which is an electrostatic instability.  Eigenspectra and eigenfunctions for different disc models, which differ by the total charge of the disc-star system are presented.  The evolution of this instability on a long time-scale is studied in a fully non-linear description by means of numerical simulations.  For multimode excitation, the average macroscopic response of the system can be described by a quasi-linear model.  In the presence of an external source feeding the disk with positive charges, representing the effect of pair creation activity in the gaps, the diocotron instability may give rise to an efficient diffusion of charged particles across the magnetic field lines.

    JD02-37            Poster

    About one hypothesis on the origin of Anomalous X-ray Pulsars and Soft Gamma-ray Repeaters

    F. Kasumov, A. Allakhverdiev, A. Asvarov

    Institute of Physics, Baku, Azerbaijan

    We analyze the possibility of realization of the scenario, according to which Anomalous X-ray Pulsars (AXPs) and Soft Gamma-ray repeaters (SGRs) originate from the radio pulsars with the very close initial parameters (period, magnetic field etc.) subjected to considerable and prolonged glitches. This scenario provides both an increase in the period of ordinary pulsars and the attainment of magnetic field strengths typical of these objects (B ~ 1013 - 1014 G), a new class of neutron stars, called magnetars, at an insignificant initial magnetic field value B » 3 1010 -1011 G.  With this aim, the criteria to which the potential progenitors of AXPs and SGRs must be satisfied were determined and analyzed.  So,  taking into account the combined action of all factors (magnetic field, distance, birth place, satisfying to our criteria etc.) we restricted our analysis to ~100 pulsars with B > 5 1012 G and P > 0.5 s. The observed characteristics of such pulsars, their association with supernova remnants, and their evolution in the P– P/dot  diagram with allowance made for the actual age of the possible AXP and SGR progenitors are shown to being in conflict with the suggested scenario and can be better described in the framework of the standard magneto-dipole model of pulsar evolution.

    JD02-38            Poster

    Combined models of evolution and real ages of pulsars

    A. Allakhverdiev, F. Kasumov, S. Tagieva

    Institute of Physics, Baku, Azerbaijan

    We offered the test for checking the applicability of fall-back or propeller models for the pulsar evolution. This test based on the comparison of the pulsars’ ages predicted by these models with the real kinematical ages of pulsars. With this goal two groups of pulsars, namely relatively young and old pulsars with the distances from the galactic plane çZ ç< 100 pc and çZ ç>300 pc, respectively, were selected. At the same time, the irregular character of deviation of the pulsars’ birthplaces from the geometrical plane of the Galaxy has been taken into account. The distribution of these groups of pulsars in Period-Period derivative diagram is compared with the theoretical tracks of the evolution of the pulsars predicted by fall-back and combined dipole + propeller models at various values of the initial parameters of radio pulsars (magnetic field and accretion rate of matter). As it is well known, characteristic feature of combined model (unlike to the pure magneto-dipole) is the increase of period derivative up to some critical value with increase of the period of pulsars, i.e. the age of pulsars. It is shown that the distribution of selected pulsars in the mentioned diagram contradicts to this model and can be easily explained by standard model of pulsar evolution.

    JD02-39            Poster

    X-ray Emission From Hot Polar Cap In Pulsars With Drifting Subpulses

    J. Gil, G. Melikidze

    Institute of Astronomy, University of Zielona Gora, Zielona Gora, Poland

    Within the framework of the partially screened inner acceleration region the relationship between the X-ray luminosity and the circulational periodicity of drifting subpulses is derived. This relationship is quite well satisfied in pulsars for which an appropriate radio and X-ray measurements exist. A special case of PSR B0943+10 is presented and discussed.The problem of formation of a partially screened inner acceleration region for all pulsars with drifting subpulses is also considered. It is argued that an efficient inner acceleration region just above the polar cap can be formed in a very strong and curved non-dipolar surface magnetic field.

    JD02-40            Poster

    Pulsed Radio Emission From Two XDINS

    V.M. Malofeev, O.I. Malov, D.A. Teplykh

    Lebedev Physical Inst., Pushchino Radio Astronomy Observatory, Pushchino, Russia

    We report the investigations of two X-ray dim isolated neutron stars: J1308.6 +212708 and J2143.03+065419. The observations were carried out on two sensetive transit radio telescopes in Pushchino at a few frequencies in the range 111 – 42 MHz.

    Mean pulse profiles, the flux density and the dispersion measures are presented. The measures of periods and their derivatives are reported, as well as, the estimation of distances and integral radio luminosities. The comparison with X-ray observations are made.

    Aknowledgements. Authors grateful for a support of this work by grant No 06-02-16888 of Russian Foundation for Basic Research.

    JD02-41            Poster

    Magnetospheric Eclipses in the Double Pulsar System J0737-3039

    R. R. Rafikov1, P. Goldreich2

    1CITA, Toronto, Canada, 2IAS, Princeton, United States

    Recently discovered double pulsar system J0737-3039 consisting of  millisecond and normal pulsars in a 2.4 hour orbit provides us with unprecedented tests of general relativity and magnetospheric effects.  One of the most interesting phenomena observed in this system is the eclipse of the millisecond pulsar in the radio at its conjunction with the normal pulsar. I will describe a theory which explains this observation as a result of synchrotron absorption of the millisecond pulsar radiobeam in the magnetosphere of the normal pulsar. Absorption is “induced” in a sense that the intense radiobeam of millisecond pulsar itself strongly modifies the properties of the plasma in the closed part of the normal pulsar magnetosphere: absorption of high-brightness temperature radio emission heats up particles already present there and also allows additional pair plasma to be trapped in this region by magnetic bottling effect. This theory self-consistently predicts the size of the eclipsing region which agrees very well with the observed duration of eclipse. Recent observations of the variability of transmission during the eclipse modulated at the rotation period of the normal pulsar have been interpreted as resulting from the absorption by the rigidly rotating dipolar-shaped magnetosphere which is in perfect agreement with our theory.

    JD02-42            Poster

    Electromagnetic Fields of Magnetized Neutron Stars in Braneworld

    B.J. Ahmedov, F.J. Fattoyev

    1Ulugh Beg Astronomical Institute, Tashkent 700052, Uzbekistan, 2International Centre for theoretical Physics, Trieste, Italy

    We study the dipolar magnetic field configuration in dependence on brane tension and present solutions of Maxwell equations in the internal and external background spacetime of a magnetized spherical neutron star in a Randall-Sundrum II type braneworld. The star is modelled as sphere consisting of perfect highly magnetized fluid with infinite conductivity and frozen-in dipolar magnetic field. With respect to solutions for magnetic fields found in the Schwarzschild spacetime brane tension introduces enhancing corrections both to the interior and the exterior magnetic field. These corrections could be relevant for the magnetic fields of magnetized compact objects as pulsars and magnetars and may provide the observational evidence for the brane tension through the modification of formula for magneto-dipolar emission which gives amplification of electromagnetic energy loss up to few orders depending on the value of the brane tension.

    JD02-43            Poster

    On Dependence of Some Parameters of Radio Pulsars Radiation on Their Age

    V.H. Malumian, A.N. Harutyunyan

    1Byurakan Astrophysical Observatory, Byurakan, Armenia

       In the paper we have studied the relationship between parameters of the radiation from pulsars and the dependence of the rates of the radiation periods of these objects on their characteristic ages. We have obtained the following results.

    (a.) The rate of change in the radiation periods (derivatives of periods, dP/dt) of pulsars depends on their characteristic age. These changes proceed more slowly with age. The rate of change of the radiation period of pulsars can in some way serve as an indicator of their age.

    (b.) The relationship between the rate dP/dt of change of the period and the period P has been demonstrated. For young pulsars this relationship is weak. In the course of evolution with age, the relationship between the derivative of the period and the period becomes closer. Whereas for “young” (T<106 years) pulsars the correlation coefficient for the logdP/dt – logP plot is only 0.49 (p<0.0001), for “old” (T≥108 years, T> 09 years) pulsars the correlation coefficient approaches unity (p<0.0001). Since, as shown above, the rate of change of the radiation period decreases with age in pulsars, we can say that the lower the rate of change of the radiation period of a pulsar is, the closer is the relationship between the derivative of its period and its period.

    In conclusion, it should be noted that we have also examined separately the data in the catalog of Taylor et al., which contains 706 objects. After eliminating the members of binary and multiple systems, as well as the members of the Magellanic Clouds, slightly more than 500 objects remain.

    JD02-44            Poster

    The Nançay Pulsar Instrumentation : The BON Coherent Dedispersor

    I. Cognard, G. Theureau

    LPCE-CNRS, Orléans, France

    We present here a summary of the Nançay pulsar instrumentation and the on going observational pulsar timing programs.

          The BON coherent dedispersor is able to handle 128MHz of bandwidth. It is made of a spectrometer, plus four data servers to spread data out to a 70-node cluster of PCs (with Linux Operating System). Dedispersion is done by applying a special filter in the complex Fourier domain. This backend has been designed in close collaboration with UC Berkeley. It benefits from the many qualities of the large Nançay radiotelescope (NRT, equivalent to a 94 m circular dish), which receivers were upgraded in 2000 : a factor  of 2.2 sensitivity improvement was obtained at 1.4MHz, with an efficiency of 1.4K/Jy for a system temperature of 35K ; a better frequency coverage was also achieved (from 1.1 to 3.5GHz).

         The first two years of BON data acquisition demonstrates that the timing data quality is comparable with the Arecibo and Green Bank results. As an example, a Time Of Arrival (TOA) measurement accuracy better than 200ns (170-180ns) is obtained in only 30 seconds of integration on the millisecond pulsar PSR B1937+21. With this up to date instrumentation, we operate two main observational programs in pulsar timing with the Nançay antenna : 1) the radio follow-up of X- and gamma-ray pulsars for the building of a complete multi-wavelength sample and 2) the monitoring of both a millisecond pulsar timing array and a targeted list of  binary or unstable pulsars for gravitational wave detection. Joining both list of targets, a total sample of 150 pulsars is then monitored regularly with a dense sampling in time.

    JD02-45            Poster

    Relation of Pulsars to the Remnants of Supernova Bursts

    V.H. Malumian, A.N. Harutyunyan

    Byurakan Astrophysical Observatory, Byurakan, Armenia

    Based on a large volume of statistical data it is shown that the spatial distributions of radio pulsars in the galaxy with characteristic ages 106£ T years and T > 106 years differ significantly. The overwhelming majority of the pulsars with 106 £T years lie within a narrow band of width 400 pc around the galactic plane. A large portion of the pulsars with T > 106 years is concentrated outside this zone. In the case of younger pulsars, a larger fraction of them lies within the confines of the above mentioned zone. It is also shown that pulsars with 106 £ T years and the remnants of supernova explosions have essentially the same spatial distribution. These facts support the existence of a relationship between pulsars and supernova remnants, as well as the acquisition of high spatial velocities by pulsars during their birth.

    JD02-46           Poster

    The Multi-photon Electron-Positron Pair Production in the Magnetosphere of Pulsars

    Ara K. Avetissian

    Yerevan State University, Yerevan, Armenia

    In general, the single-photon reaction γ → e- + e+, as well as the inverse reaction of the electron-positron annihilation can proceed in a medium that must be a plasma-like. To provide a macroscopic refractive index n(ω)<1 at necessary for pair production γ-frequencies one needs plasma densities ρ > 1033 cm-3. Such superdense matter exists in the core of the neutron stars - pulsars. At these densities the electron component of the superdense plasma is fully degenerate and taking also into account the Pauli principle the probabilities of these processes actually turn to zero [1]. Hence, here we consider the possibility of multi-photon electron-positron pair production by strong electromagnetic radiation of soft frequencies in magnetosphere of pulsars [2], which is possible at ordinary densities of plasma [3]. Such multi-photon process occurs via nonlinear channels at high intensities of electromagnetic radiation in wide region of frequencies from radio to UV and soft X-ray in pulsars’ magnetosphere.

    Numerical simulations for various pulsars (Ω~1÷200 s-1) with the help of analytical distribution functions of magnetosphere’s plasma with densities ρ~1020÷1022 cm-3 [2] and pair production probabilities [3] have been made, and both energetic and angular distributions of produced electron-positron pairs are presented.

    JD02-47            Poster


    O. Skjaeraasen

    University of Oslo, Oslo, Norway

    We study extremely nonlinear, coherent electromagnetic waves in the context of relativistic, expanding plasma flows, where a confining external medium triggers the formation of a shock.

    Using a combination of analytical methods and Particle-In-Cell simulations, we discuss mechanisms of wave generation and dissipation, as well as how the waves affect the particle distribution.

    For a large-amplitude wave of general polarisation, any given set of wave parameters uniquely fixes the particle and energy flux associated with the flow. In cases where the wave properties can be constrained, this can be used to estimate the flow parameters.

    The prime application of our work is to pulsar winds and pulsar wind termination shocks, where our model provides a viable alternative to magneto-hydrodynamic models. Using canonical parameters for the Crab, we discuss mode couplings and transitions between the inner and outer parts of the wind, and use simulation data to shed new light on the microphysics of the wave as it reaches the shock.

    JD02-48            Poster

    Coupled Spin, Mass, Magnetic field, and Orbital Evolution of Accreting Neutron stars

    M. Mirtorabi, A. Javadi Khasraghi, S. Abdolrahimi

    Alzahra, Tehran, Iran

    The present study is mainly addressed to the coupled spin, mass, magnetic field, orbital separation, and orbital period evolution of a neutron star entering a close binary system with a low mass main sequence companion, which loses mass in form of homogenous stellar wind. We apply flux expulsion of the magnetic field from the superfluid  superconductive core of a neutron star , based on different equation of states, and its subsequent decay in the crust , which also depends on conductivity of the crust, and hence on the temperature, T, and the neutron star age. The initial core and surface magnetic field are of the same order of magnitude. To derive the rate of expulsion of the magnetic flux out of the core we consider various forces which act on the fluxoids in the interior of a neutron star, including a force due to their pinning interaction with the moving neutron vortices, buoyancy force, curvature force, and viscous drag force due to magnetic scattering of electrons. Various effects accompanying mass exchange in binaries can influence the evolution of spin and magnetic field of the neutron star. The orbital separation of the binary clearly affects the estimated value of , and it itself evolves due to mass exchange between the components, mass loss from the system, and two other sinks of the orbital angular momentum namely magnetic braking and gravitational waves. The neutron star passes through four evolutionary phases ( isolated pulsar- propeller- accretion from the wind of a companion- accretion resulting from Roche-lobe overflow). Models for a range of parameters, and initial orbital period, magnetic field and spin period are constructed. The impurity parameter, Q, is assumed to be constant during the whole evolution of the star and range from 1 to 0.001.  Final magnetic field, spin and orbital period are presented in this paper. The surface magnetic field weakens by a factor of .The suggested mechanism can explain the lower magnetic field and faster spins of millisecond pulsars that have been recycled by accretion in close binaries.

    JD02-49            Poster

    Investigating The Magnetic Field of The Solar Corona With Pulsars


    University of Sydney, Sydney, Australia

    We propose a novel experiment to examine both the magnetic field and electron content of the solar corona. We intend to measure the Faraday rotation and dispersion evident in observations of background pulsar sources as they are occulted by the Sun. As we will be utilising a number of simultaneous lines of sight, that will cut different paths through the corona as the Sun rotates, we will be able to strongly constrain the global topology of both the plasma and the magnetic field.

    Although similar experiments have been performed using other background radio sources and space probes; this experiment differs in that many lines of sight can be examined simultaneously, and the Magnetic field and plasma density can be measured independently.

    We propose to use the Parkes radio telescope to observe a number of pulsars as they are occulted by the Sun in December 2006. We present an outline of the experiment and a discussion of the expected results.

    JD02-50            Poster

    RRATs and PSR B1931+21

    X.-D. Li

    Department of Astronomy, Nanjing University, Nanjing, China

    Introduction: The recent discovery of rotating radio transients and the quasi-periodicity of pulsar activity in the radio pulsar PSR B1931+24 has challenged the conventional theory of radio pulsar emission.

    Methods: Here we suggest that these phenomena could be due to the interaction between the neutron star magnetosphere and the surrounding debris disk.

    Results: The pattern of pulsar emission depends on whether the disk can penetrate the light cylinder and efficiently quench the processes of particle production and acceleration inside the magnetospheric gap.

    Discussion: A precessing disk may naturally account for the switch-on/off behaviour in PSR B1931+24.

    JD02-51            Poster

    Is PSR B0656+14 a very nearby RRAT source?

    P Weltevrede1, B Stappers2, J Rankin3, G Wright4

    1Astronomical Institute ``Anton Pannekoek'', Amsterdam, Netherlands, 2Stichting ASTRON, Dwingeloo, Netherlands, 3Physics Department, Vermont, United States, 4Astronomy Centre, Sussex, United Kingdom

    The recently discovered RRAT sources are characterized by very bright

    radio bursts which, while being periodically related, occur infrequently. We find bursts with the same characteristics for the known pulsar B0656+14. These bursts represent pulses from the bright end of an extended smooth pulse-energy distribution and are shown to be unlike giant pulses, giant micropulses or the pulses of normal pulsars. The extreme peak-fluxes of the brightest of these pulses indicates that PSR B0656+14, were it not so near, could only have been discovered as an RRAT source. Longer observations of the RRATs may reveal that they, like PSR B0656+14, emit weaker emission in addition to the bursts.

    The emission of PSR B0656+14 can be characterized by two separate populations of pulses: bright pulses have a narrow ``spiky'' appearance consisting of short quasi-periodic bursts of emission with microstructure, in contrast to the underlying weaker broad pulses. The spiky pulses tend to appear in clusters which arise and dissipate over about 10 periods. We demonstrate that the spiky emission builds a narrow and peaked profile, whereas the weak emission produces a broad hump, which is largely responsible for the shoulders in the total emission profiles at both high and low frequencies.

    JD02-52            Poster

    Glitch Observations In Slow Pulsars

    G.H. Janssen1, B.W. Stappers2

    1Astronomical Institute 'Anton Pannekoek', University of Amsterdam, Amsterdam, Netherlands, 2Stichting Astron, Dwingeloo, Netherlands

    We have analyzed 5.5 years of timing observations of 7 ``slowly'' rotating radio pulsars, made with the Westerbork Synthesis Radio Telescope. We present improved timing solutions and  30, mostly small, new glitches. Particularly interesting are our  results on PSR J1814-1744, which is one of the pulsars with similar rotation parameters and magnetic field strength to the  Anomalous X-ray Pulsars (AXPs). Although the high-B radio pulsars  don't show X-ray emission, and no radio emission is detected for AXPs, the roughly similar glitch parameters provide us with another tool to compare these classes of neutron stars. Furthermore, we were able to detect glitches one to two orders of magnitude smaller than before, for example in our well-sampled observations of PSR B0355+54.  We double the total number of known glitches in PSR B1737-30, and improve statistics on glitch sizes for this pulsar individually and pulsars in general.  We detect no significant variations in dispersion measure for PSRs B1951+32 and B2224+65, two pulsars located in high-density surroundings. We discuss the effect of small glitches on timing noise, and show it is possible to resolve timing-noise looking structures in the residuals of PSR B1951+32 by using a set of small glitches.

    JD02-53            Poster

    Mode Coupling in Pulsar Magnetospheres Due to Plasma Gradients Perpendicular to the Magnetic Field

    A. C. Judge

    University of Sydney, Sydney, Australia

    Conventional ideas regarding plasma instabilities suggest that the polarisation of pulsar radio emission should be dominated by that corresponding to the fastest growing mode.  The presence of two distinct polarisations, indicating emission in two distinct modes, is, however, almost ubiquitous in observations of these objects. In order to reconcile the basic theory with the observations it has been proposed that energy is exchanged between the natural modes of the plasma as the radiation propagates through the magnetosphere of the pulsar.

    The basic theory of mode-coupling in stratified media has already been developed in work relating to wave propagation in the ionosphere and the solar corona. Here, this formalism is applied to a relativistically streaming plasma and gradients in the plasma perpendicular to the direction of the local magnetic field are investigated as a possible mechanism for effective mode-coupling in a pulsar magnetosphere.

    JD02-54            Poster

    Software Aspects of PuMa-II

    R Karuppusamy1, B Stappers1, B Stappers2

    1ASTRON, Dwingeloo, Netherlands, 2University of Amsterdam, Amsterdam, -

    The Pulsar Machine II (PuMa-II) is a state of the art pulsar machine,installed at the Westerbork Synthesis Radio Telescope (WSRT), in December 2005. PuMa-II is a flexible instrument and is designed   around an ensemble of 44 high-performance computers running the Linux operating system.  Much of the flexibility of PuMa-II comes from the software that is being developed for this instrument. The radio signals reaching the telescope undergo several stages of electronic and software processing before a scientifically useful data product is generated. The electronic processing of signals includes the usual RF to IF conversion, analogue to digital conversion and telescope dependent electronic digital delay compensation that happen in the signal chain of WSRT. Within PuMa-II, this data is acquired, stored and suitably processed. In this poster we present various aspects of PuMa-II software and illustrate its pulsar signal processing capabilities.

    JD02-55            Poster

    High Time Resolution Low-Frequency Pulsar Studies

    B. W. Stappers

    ASTRON, Dwingeloo, Netherlands

    Low frequency observations of radio pulsars have, to a certain extent, fallen out of favour in recent times. This is despite exciting and interesting work in Russia, Ukraine and India. The move to higher frequencies has mainly been due to the deleterious effects of the interstellar medium. However, with the increased availability of baseband recording and coherent dedispersion techniques and new facilities such as the LFFEs at the Westerbork Synthesis Radio Telescope (WSRT) and in the future LOFAR/LWA, the interest in observations at frequencies below 300 MHz is growing again. I will present some exciting results on single pulse studies from observations at the WSRT (115-180 MHz). These will include the first full polarisation observations of Crab giant pulses at these frequencies. I will also present the prospects for pulsar research with LOFAR. LOFAR will have unprecedented collecting area and bandwidth at frequencies below 220 MHz, allowing for a wide range of pulsar studies, in particular in emission physics. I will show results from simulations which show that an all-sky survey with LOFAR could be expected to find up to 1500 new pulsars.  This survey would provide significant constraints on the low-end of the pulsar luminosity distribution which has important consequences for the total pulsar population. I will also show that LOFAR could detect pulsars in nearby galaxies.

    JD02-56            Poster

    The 8gr8 Cygnus Survey for New Pulsars and RRATs

    E. Rubio-Herrera1, R. Braun2, G. Janssen1, J. van Leeuwen3, B.W. Stappers1

    1Astronomical Institute Anton Pannekoek, Amsterdam, Netherlands, 2ASTRON, Dwingeloo, Netherlands, 3University of British Columbia, Vancouver, Canada

    We are currently undertaking a survey to search for new pulsars and the recently found Rotating RAdio Transcients (RRATs) in the Cygnus OB complex. The survey uses the Westerbrok Synthesis Radio Telescope in a unique mode which gives it the best sensitivity of any low-frequency wide-area survey.  So far we have found a few new pulsars and have begun using routines for the detection of RRATs. We present here some initial results on the new pulsars and possible transients. We expect to find a few tens of new pulsars and a similar number of RRATs. The latter discoveries will help us to improve our knowledge about the population and properties of the  poorly known objects as well as provide an improved knowledge of the number of young pulsars associated with the OB complexes in the Cygnus region.

    JD02-57            Poster

    Pulsar Coherent De-dispersion Observation at Urumqi Observatory

    Aili Yishamuding

    Urumuqi Observatory,NAO,CAS, Urumqi, China

    Based on a Mark5A VLBI backend and a four node cluster, pulsar off-line conerent de-dispersion observations has been conducted by usuing Urumqi 25m telescope. The observing system is described and the initial results are presented in this paper.

    JD02-58            Poster

    X-ray Monitoring of the Pulsar PSR B1259−63

    H. H. Huang, W. Becker

    Max-Planck-Institut für extraterrestrische Physik, Garching, Germany

    PSR B1259-63, a rotation-powered radio pulsar with a ~48 millisecond period, is in a highly eccentric (e~0.87) 3.4 year orbit around a massive Be star SS 2883. We report the results of the XMM-Newton observations performed between 2001 and 2004. Combining the XMM-Newton observations with the previous results from ASCA, we found that the best-fit power-law models in 1.0-10.0 keV energy band show long term variations in the photon indices from ~1.11 to ~1.95. The X-ray flux is observed to increase by a factor of > 10 at perisatron to apastron. No X-ray pulsation at the pulsar's spin period was found in any observations so far. A model invoking the interaction between the pulsar and the stellar wind is likely to explain the observed orbital phase-dependent time variability in the X-ray flux and spectrum.

    JD02-59            Poster

    XMM-Newton Observation of PSR B1957+20

    H. H. Huang, W. Becker

    Max-Planck-Institut für extraterrestrische Physik, Garching, Germany

    The "Black Widow pulsar", PSR B1957+20, is a millisecond pulsar which is in a 9.16 - hour binary system. H-alpha bow-shock nebula created by the interaction between the relativistic wind of the pulsar and the surrounding ISM and ablation of the low-mass companion star by the pulsar wind were observed. We report on a 30 ksec observation of PSR B1957+20, using the EPIC-MOS detector on-board the XMM-Newton Observatory. The detect X-ray diffused emissions detected from this source is consistent with the result derived from Chandra observations. The spectrum of the nebular emission can be modeled with a single power law spectrum of photon index 2.1 (+0.4) (-0.3). This extended emission generated by accelerated particles in the post shock flow is considered to explain this result. For the first time, we detected significant X-ray flux modulation near to the pulsar's radio eclipse.

    JD02-60            Poster

    Optical observations of binary millisecond X-ray pulsars in quiescence

    P Callanan1, M Reynolds1, A Filippenko2, P Garnavich1, R Foley2

    1University College Cork, Cork, Ireland, 2Astronomy Department, University of California, Berkeley, Berkeley, United States, 3Department of Physics, University of Notre Dame, Notre Dame, United States

    The discovery of accreting binary millisecond pulsars finally provided firm confirmation of the link between bright accreting Low Mass X-ray Binries and millisecond pulsars. Little is known about their optical properties in quiewscence, however. Here we present optical observations of SAX J1808.4-3658 and IGR J00291+5934 in quiescence, and compare them to other quiescent X-ray transients.

    JD02-61            Poster

    X-Ray Studies of the Central Compact Objects in Puppis-A& RX J0852.0-4622

    C. Y. Hui, W. Becker

    Max-Planck Institut fuer Extraterrestrische Physik, Garching, Germany

    The Supernova remnants (SNRs) Puppis-A and RX J0852.0-4622 (Vela-Junior) are located along the line of sight towards the outer rim of the Vela SNR. Central compact objects (CCOs) were discovered in each of them. Both CCOs are thought to be the compact stellar remnants formed in core-collapsed supernova explosions. Nevertheless, the emission properties observed from these sources are completely different from what is observed in other young canonical neutron stars. Based on observations with the X-ray observatories Chandra and XMM-Newton, we present the most recent results from a detailed spectro-imaging and timing analysis of these two enigmatic sources.

    JD02-62            Poster

    Probing the Proper Motion of the Central Compact Object in Puppis-A

    C. Y. Hui, W. Becker

    Max-Planck Institut fuer Extraterrestrische Physik, Garching, Germany

    Using two observations taken with the High Resolution Camera (HRC-I) aboard the Chandra X-ray satellite, we have examined the central compact object RX J0822-4300 for a possible proper motion. The position of RX J0822-4300 is found to be different by 0.574±0.184arcsec, implying a proper motion of 107.49±34.46 mas/yr with a position angle of 241±24 deg. For a distance of 2.2 kpc, this proper motion is equivalent to a recoil velocity of 1121.79±359.60 km/s. Both the magnitude and the direction of the proper motion are in agreement with the birth place of RX J0822-4300 being near to the optical expansion centre of the supernova remnant. Although this is a promising indication of a fast moving compact object in a supernova remnant, the relative large error prevents any constraining conclusion.

    JD02-63            Poster

    Exposing Drifting Subpulses From The Slowest To The Fastest Pulsars

    Joeri van Leeuwen

    University of British Columbia, Department of Physics & Astronomy, Vancouver, Canada

    Pulsar emission is surprisingly similar over a vast range of periods and magnetic fields: all the way from the 2-millisecond 108 G recycled pulsars to the 6-second 1014 G magnetar-like regular pulsars. We investigate how the curious instabilities called 'drifting subpulses' we observe can discern between different mechanisms for pulsar emission.

    JD02-64            Poster

    Pulsar Research With LOFAR, The First Next-Generation Radio Telescope

    Joeri van Leeuwen1, Ben Stappers2

    1University of British Columbia, Department of Physics & Astronomy, Vancouver, Canada, 2Stichting ASTRON ; Astronomical Institute 'Anton Pannekoek', University of Amsterdam, Amsterdam, Netherlands

    LOFAR is a low-frequency radio telescope of revolutionary design that is currently being constructed and will be operational in 2007. In stark contrast to radio dishes, LOFAR is the first telescope that relies on a central supercomputer to combine the signals of ten thousand individual dipoles to form several extremely sensitive, independently steerable beams on the sky. I will discuss how LOFAR opens up a new frequency window with unprecedented sensitivity and why LOFAR will have considerable impact on radio pulsar research.

    JD02-65            Poster

    Non-Dipolar Surface Magnetic Field of Neutron Stars: General Approach and Observational Consequences

    G.I. Melikidze, A. Szary, J. Gil

    Institute of Astronomy, Zielona Gora, Poland

    It is widely accepted that the magnetic field structure near the surface of neutron stars may significantly differ from the star centered global dipole structure. Due to flux conservation of the open magnetic field lines, strong non-dipolar surface field results in significant shrinking of the canonical polar cap, in general. We have modeled different possible configurations and found out that for some configurations the pair creation is possible not only along the open field lines, but also in the region of closed field lines. Therefore, in this case, we can naturally explain some peculiarities of pulsar activities, such as unusual thermal x-ray emission, reversible radio emission and rotating radio transients.

    The pairs created along the closed field lines can easily reach the stellar surface near the polar cap at the opposite side of the neutron star and heat the surface area that can even exceed that of the canonical polar cap. Both smaller (often) and larger (rarely) bolometric surface areas of the hot polar cap are observed.

    In the frame of this model, we can easily realize the configuration, which allows the pair creation near both polar caps (along the same field). In this case, two streams of the pair plasma penetrate each other creating a favourable condition for the two-stream instability to be developed. Such a process can lead to the radio emission generation, either in quasi-stationary or stochastic process. Consequently, either quasi-stationary reversible radiation, or stochastic emission of the transients can be observed.

    JD02-66            Poster

    Glitches In the Vela Pulsar

    SJ Buchner1, C Flanagan2

    1HartRAO, Krugersdorp, South Africa, 2Johannesburg Planetarium, Johannesburg, South Africa

    The Vela pulsar undergoes occasional sudden “spin-ups” in rotational frequency. The recovery from these glitches provides insight into the internal structure of the neutron star. We have used HartRAO to monitor Vela since 1984 and have observed eight large glitches. We present this data. 

    JD02-67           Poster

    Optical polarization of the Crab pulsar with 19 us time resolution

    A. Slowikowska1, G. Kanbach1, A.Stefanescu1

    1MPE, Garching, Germany

    1NCAC Torun, Poland

    We have observed the Crab nebula and pulsar for about 25 hours with the high-speed photo-polarimeter OPTIMA in November 2003 at the Nordic Optical Telescope, La Palma. The instrument’s sensitivity (white light) extends from about 450nm to 950nm and reaches about 60%. Linear polarization is measured with a continuously rotating polaroid filter which modulates the incoming radiation. The astronomical target is viewed through the polaroid  and imaged onto a hexagonal bundle of optical fibers which are coupled to single photon APD counters. The spacing and size of the fibers at NOT corresponds to about 2 arcsec. GPS based time tagging of single photons with 4 microsec resolution, together with the instantaneous determination of the angular position of the rotating polaroid filter, allows to measure the phase dependent linear polarization state of the pulsar and the surrounding nebula simultaneously.

    The Crab pulsar and its net optical polarization are determined at all phases of rotation with extremely high statistical accuracy. On time scales of a few 10’s of microseconds significant details of the polarization of the main emission peak become visible.

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