Joint Discussion JD02

Wednesday 16 August 2006 (morning)
09:00-09:40Dick Manchester
Recent observational results on the radio emission properties of pulsars are reviewed.
09:40-10:20Maura McLaughlin
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.
10:20-11:00Patricia Caraveo
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.
11:00-11:20Coffee
11:20-12:00Ocker C. de Jager
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.
12:00-12:40David Nice
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.
Wednesday 16 August 2006 (afternoon)
14:00-14:40Vladimir Usov
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.
14:40-15:20K.S. Cheng
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.
15:20-16:00Duncan Lorimer
Poster rapporteur
16:00-16:20Coffee
16:20-17:00John Arons
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.
17:00-17:40Sachiko Tsuruta
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.
17:40-19:00Poster session
Thursday 17 August 2006 (morning)
09:00-09:40Scott Ransom
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.
09:40-10:20Ingrid Stairs
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.
10:20-10:50Coffee
10:50-11:30Michael Kramer
Poster rapporteur
11:30-12:10Werner Becker
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.
12:10-12:50David Smith
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.
12:50-13:00Ali M. Alpar - Summary and concluding remarks

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