Our calculations show that the cross section of the inverse Compton scattering in strong magnetic fields may be larger than that of Thompson scattering by sevaral orders of magnitude in the case of polar cap surface of pulsars. We can also see that when the energy of e± exceeds a certain value, their energy loss caused by the inverse Compton scattering may be larger than the energy gain from electric field in the inner gap, which implies that the e± could not be accelerated to γ = 106. Meanwhile, the electrostatic forces acting on the electrons will be balanced by the radiative pressure if temperature T > 108 K.

It is beleived that the surface temperarure for most of pulsars is less than 106 K, in that case the ions of iron can not be emitted from the surface of pulsars. However, the temperarure at the polar cap can be increased to 3×106 through the bombardment of electrons to the polar cap according to R-S model. This quasi-equilibrium state by self-regulating must make the coherent radio emission unstable on the contrary.

The possible existence of strong electromagnetic fields in pulsars has motivated extensive interest in investigation of various quantum electrodynamics processes. In particular, the process of converting high energy photons into electron-positron pairs is of great significance in pulsar theory.

The downward accelerated e− in the “unfavorable” zone, like that in the “favorable” one, will emit γ-photons, which in turn convert into e± pairs in some places near the surface of stars. But what happens, which is different from that in the “favorable” zone, is that some γ-photons will travel through a long distance before their conversion. This makes it possible that some γ-photons arrive at the “diode” district in the “favorable” zone. The magnetic conversion of pairs is much easier to happen than that occured in the “favorable” zone, where the γ-photons are created by the primary e− beam. The existence of dense e± plasma near the surface of stars makes the E, vanish at places where such plasma is present.

Pulse timing observations at Jodrell Bank have shown that the relatively old pulsar PSR 0355+54 has suffered two glitches in the last 18 months, the second glitch being larger than any previously observed in any pulsar.

A pulsar-monitoring programme has been running at Hartebeesthoek Radio Astronomy Observatory over the last three years, at 2.32 and (during the last year) at 1.67 GHz. Twenty pulsars are observed once or twice a fortnight, and PSRs 1641-45 and 0833-45 (the Vela pulsar) daily.

The radio pulsars in the Galaxy are found predominantly in the disk, with a scale height of several hundred parsecs. After allowing for pulsar velocities, the data are consistent with the hypothesis that single pulsars form from massive stellar progenitors. The number of active single pulsars in the Galaxy is ∼ 1.5 × 105, and their birthrate is 1 per ∼ 60 yrs. There is some evidence that many single pulsars, particularly those with high magnetic fields, are born spinning slowly, with initial periods ∼ 0.5–1s. This could imply an origin through binary “recycling” followed by orbit disruption, or might suggest that the pre-supernova stellar core efficiently loses angular momentum to the envelope through magnetic coupling. The birthrate of binary radio pulsars, particularly of the millisecond variety, seems to be much larger than previous estimates, and might suggest that these systems do not originate in low mass X-ray binary systems.

We review facts, myths and theories related to the formation of neutron stars and their coupling to the environment.

Crab-like SNR are markers for recently formed pulsars. The current catalog of 15 objects allows a direct measure of the space distribution of pulsars, the beaming factor of pulsars, and the energetics at young pulsars. The 15 Crab-like SNR are equally divided between those with surroundings shells and those without. No other properties appear to correlate with the presence or lack of a shell. The ratio of 10 to 1 between all remnants and Crab-like remnants has important implications for the formation of pulsars.

X-ray observations of selected SNR are summarized. Five contain internal spinning neutron stars–four isolated and one in a binary system. Another seven contain central unresolved sources or bright nebulae. Observations of these nebulae, probably due to synchrotron emission, are used to estimate characteristics of the unseen pulsars.

The progenitors of single as well as binary pulsars are discussed with special emphasis on binary pulsars with low mass companions. Several predictions are made concerning millisecond pulsars.

Recently, pulsars are classified into two types. On the basis of these data, it is possible to discuss the relation between these two types of pulsars and supernova remnants, respectively. In this paper, the statistical K-S test is used to judge whether the two samples of distributions may come from one original distribution or not.

We have found solutions to the problem of a relativistic pulsar wind interacting with a nebula moving at constant velocity vn. The wind is assumed to contain a toroidal magnetic field; the ratio of Poynting flux to particle flux in the wind is a constant σ. Under these assumptions, the wind is shocked at a radius rs that moves out at constant velocity. Solutions for the shocked wind are only possible if σ < σc = 1/(−1 + c/vn). For a given value of vn, rs → as σ → σc. Kennel and Coroniti (1984) have calculated similar models for the Crab Nebula but they assume that rs is a constant; i.e. they calculate steady-state models. The steady-state approximation is expected to be good close to the shock wave, but it breaks down in the outer parts of the nebula. For vn = 2000 km s−1 and rn/rg = 20, Kennel and Coroniti find σ = 0.003. For the same Crab Nebula pmeters, our time-dependent model yields σ = 0.0016. There may be times in the evolution of Crab Nebula or of other pulsar nebulae when a model with a shocked relativistic wind and a toroidal magnetic field cannot apply. It appears that a wide variety of structures are possible for pulsar nebulae.

We report Very Large Array1 observations of 3C 58, the Crab Nebula's closest relative at radio wavelengths. We combined A, B, C, and D configurations (baselines ranging from 0.08 to 35 km) at frequencies of 1446 MHz and 4886 MHz, achieving resolutions of 1″.9 and 2″.5, respectively, and a sensitivity at both frequencies of about 70 μJy per beam. We deconvolved the point-source response from the images using a maximum-entropy technique. The 1446 MHz total-intensity image shows that filamentation not only dominates the spatial distribution of flux in the bright inner regions, but appears to continue into the faint outer envelope as well. This envelope fades smoothly into the noise over about half the circumference of the remnant; the lowest contours of our map show maximum extents in RA and δ of 10′.3 and 6′.3 respectively. However, in some places the edge is relatively well-defined, suggesting confinement of some kind. A remarkably jet-like extension can be seen protruding from the south central part of the remnant, with a position angle of about 150° with respect to the radio peak. Unlike the Crab's jet, this is wedge-shaped and somewhat resembles the brighter extension to the north. The X-ray point source (Becker, Helfand, and Szymkowiak 1982, Ap. J. 255, 557) lies about 30″ east of the peak in the radio map. No obvious radio feature coincides with it. We have made spectral-index maps of the remnant, and find only small variations, with little apparent correlation of spectral index with structure. The rms deviation from the remnant mean spectral index is 0.18, but profiles of filaments show less than 0.1 difference in spectral index between peaks and adjacent valleys. Thus the bright filaments are neither flatter nor steeper in spectrum than the remnant mean, ruling out a picture in which bright filaments are locations where shock acceleration produces a steeper particle energy spectrum. Filaments have brightness contrasts of factors of 1.5 to 2, steep edges (<10″, sometimes unresolved) and widths of 10″–30″; if they have similar thicknesses along the line of sight, their emissivity ranges up to 40–50 times the remnant mean.

Two of the recently discovered pulsars PSR 1800-21 and 1823-13 have characteristics ages of 17,000 and 22,000 yr respectively and all the three known pulsars that are younger than these two lie within the known supernova remnants (Clifton and Lyne, 1986). These two pulsars are expected to have, by scaling from the Crab nebula, plerions of ∼1 Jy each associated with them at 327 MHz. We mapped a field of 1.˚95 × 1.˚5 around both the pulsars with the Ooty Synthesis Radio Telescope (Swarup, 1984). As the fields are on the galactic plane having complex large scale emission and as the plerions are expected to be compact, we have made maps by excluding baselines less than 500 λ. This would make our maps insensitive to emission regions larger than ∼7 arc min. The synthesised beam is 96 × 36 arc sec in PA 0°. No source with a surface brightness greater than 60 mJy/beam was detected in the direction of PSR 1823-13. An unresolved source of ∼150 mJy was detected, in the positional error box of PSR 1800-21, as is shown in the figure. No pulsed emission with an average flux density greater than 10 mJy was detected from this continuum source. It is possible that the pulse is so highly scatter broadened that it becomes undetectable at 327 MHz and the detected source is the scatter broadened pulsar. But, such a possibility seems unlikely as the pulsar's dispersion measure is only 230 cm−3 pc, leaving the interesting possibility that the detected source is a plerion associated with the pulsar.

Two examples are given of probable radio jet/supernova remnant association, G332.4+0.1 and G315.8-0.0. In both cases the jet length is larger than the radius of the remnant's shell; the jet diameter is barely resolved, and is substantially less than the observed shell thickness. The jet luminosity is 5–10% that of the shell. The G332.4+0.1 jet termi nates in an extended plume whose luminosity is ∼50% that of the shell.

The remnants of the Kepler's and Tycho's supernovae show a thick shell structure with a sharp outer edge and significant brightness irregularities. Models of their expansion have been constructed using a one-dimensional spherical hydrodynamics code, which includes both a leading shock and a reverse shock moving back into the ejectum. The dynamics are controlled by conditions between these shocks. Synchrotron radio emission is produced by acceleration and amplification of initial relativistic particles and fields by eddy motion at the interface between the ejected and swept-up material and at the boundaries of clumps in the surroundings with a mean separation of 5×1017 cm, Gaussian sizes of 1×1017 cm and peak densities of 3.6×10−24 cm−3. The latter was typically 10 times the mean density between clumps. A net radial orientation of the magnetic fields is attributed to stretching by Rayleigh-Taylor instabilities at the contact surfaces. To simulate true three-dimensional structure with the one-dimensional model, random contributions from four runs with varying spacings for the clumps were summed along the line of sight. The results are shown in the figure. Without clumps the observed shell is much too narrow and steep on the inside. Whether the clumpiness is a result of presupernova mass loss or a general property of the interstellar medium is not known.

Aim of my poster is to show that Kepler's supernova progenitor was a massive star, rather than an old population object, as commonly accepted. The star was subject to strong mass loss, and the present remnant is due to the interaction of the blast wave with dense circumstellar matter

The supernova remnants (SNR) SN1006 and Tycho are considered to be originating from type I supernovae (SN). Therefore one may expect a large amount of heavy elements, particularly iron, in the SNRs. In fact, our recent analysis of new data on the X-ray spectrum Tycho shows strong line emission associated with ionized silicon, sulfur and iron. This result contradicts the results of previous analyses which did not require an overabundance of iron.

Long after a supernova event, the stellar core (neutron star) may continue to excite an extended remnant of ejecta surrounding it, as in the case of the Crab nebula. In contrast, the more common shell supernova remnants (SNRs) appear unaffected by any embedded neutron star.