Formation and evolution of binary and millisecond radio pulsars

Hybridization of radioactive nucleic acids with the DNA of cytological preparations shows that the sequences of mouse satellite DNA are located in the centromeric heterochromatin of the mouse chromosomes. Other types of heterochromatin in the cytological preparations do not contain satellite DNA.

https://science.sciencemag.org/content/sci/168/3937/1356.full.pdf

Chromosomal localization of mouse satellite DNA.

There is a wide range of fundamental physical problems directly related to how pulsars function. Some of these are independent of the specific pulsar mechanism. Others relate directly to the physics of the pulsar and already shed some light on the properties of matter at high density (\ensuremath{\sim}${10}^{15}$ g/cc) and in strong magnetic fields (\ensuremath{\sim}${10}^{12}$ G). Pulsars are assumed to be rotating neutron stars surrounded by strong magnetic fields and energetic particles. It is somewhere within this "magnetosphere" that the pulsar action is expected to take place. Currently there has been considerable difficulty in formulating an entirely self-consistent theory of the magnetospheric behavior and there may be rapid revisions in the near future, which is all the more surprising since many of the issues involve "elementary" problems in electromagnetism. One interesting discovery is that charge-separated plasmas apparently can support stable static discontinuities.

Theory of pulsar magnetospheres

We revise the physics of primary electron acceleration in the "slot gap" (SG) above the pulsar polar caps (PCs), a regime originally proposed by Arons and Scharlemann (1979) in their electrodynamic model of pulsar PCs. We employ the standard definition of the SG as a pair-free space between the last open field lines and the boundary of the pair plasma column which is expected to develop above the bulk of the PC. The rationale for our revision is that the proper treatment of primary acceleration within the pulsar SGs should take into account the effect of the narrow geometry of the gap on the electrodynamics within the gap and also to include the effect of inertial frame dragging on the particle acceleration. We show that the accelerating electric field within the gap, being significantly boosted by the effect of frame dragging, becomes reduced because of the gap geometry by a factor proportional to the square of the SG width. The combination of the effects of frame dragging and geometrical screening in the gap region naturally gives rise to a regime of extended acceleration, that is not limited to favorably curved field lines as in earlier models, and the possibility of multiple-pair production by curvature photons at very high altitudes, up to several stellar radii. We present our estimates of the characteristic SG thickness across the PC, energetics of primaries accelerated within the gap, high-energy bolometric luminosities emitted from the high altitudes in the gaps, and maximum heating luminosities produced by positrons returning from the elevated pair fronts. The estimated theoretical high-energy luminosities are in good agreement with the corresponding empirical relationships for gamma-ray pulsars. We illustrate the results of our modeling of the pair cascades and gamma-ray emission from the high altitudes in the SG for the Crab pulsar. The combination of the frame-dragging field and high-altitude SG emission enables both acceleration at the smaller inclination angles and a larger emission beam, both necessary to produce widely-spaced double-peaked profiles.

/pdf/extended-acceleration-in-slot-gaps-and-pulsar-high-energy-27liccfbr5.pdf

Extended acceleration in slot gaps and pulsar high-energy emission

We explore the pulsar slot gap (SG) electrodynamics up to very high altitudes, where for most relatively rapidly rotating pulsars both the standard small-angle approximation and the assumption that the magnetic field lines are ideal stream lines break down. We address the importance of the electrodynamic conditions at the SG boundaries and the occurrence of a steady-state drift of charged particles across the SG field lines at very high altitudes. These boundary conditions and the cross-field particle motion determine the asymptotic behavior of the scalar potential at all radii from the polar cap (PC) to near the light cylinder. As a result, we demonstrate that the steady-state accelerating electric field, E(sub ll), must approach a small and constant value at high altitude above the PC. This E(sub ll) is capable of maintaining electrons moving with high Lorentz factors (approx. a few x 10(exp 7)) and emitting curvature gamma-ray photons up to nearly the light cylinder. By numerical simulations, we show that primary electrons accelerating from the PC surface to high altitude in the SG along the outer edge of the open field region will form caustic emission patterns on the trailing dipole field lines. Acceleration and emission in such an extended SG may form the physical basis of a model that can successfully reproduce some pulsar high-energy light curves.

/pdf/high-altitude-particle-acceleration-and-radiation-in-pulsar-2i3bpb9dyd.pdf

High-Altitude Particle Acceleration and Radiation in Pulsar Slot Gaps

An attempt to account quantitatively for the pulse width, polarization and spectrum of the pulses.

Possible mechanism for the pulsar radio emission.

Measurements of the pulsar tentatively identified with the supernova remnant Vela X support the rotational model. This pulsar is remarkable for the very high degree of linear polarization in its signals.

Evidence in support of a rotational model for the pulsar PSR 0833-45

The first observations from Australia of the pulsating radio source raise difficulties about the precise measurement of the period of oscillation.

Measurements on the Period of the Pulsating Radio Source at 1919 + 21

The apparently random fluctuations in the amplitude of pulsed radio sources1 contrasts strikingly with the strictly periodic nature of the pulses1,2. This behaviour suggests that the fluctuations do not originate in the source itself but rather are imposed by the intervening medium. Scheuer3, however, has argued that the amplitude variations cannot be scintillations produced by either the general interstellar medium or the interplanetary medium. A spaced receiver experiment which we carried out in May 1968 provides experimental confirmation of Scheuer’s conclusion, at least for those fluctuations having quasi-periods of up to several minutes’ duration. Our results demonstrate that there is no detectable time displacement between the amplitude variations at the spaced receivers. This provides direct evidence that variations in pulse amplitude are imposed at or naer the source itselt.

Spaced Receiver Observations of Pulsed Radio Sources

OBSERVATIONS with the Parkes 210 foot telescope during May and June 1968 have shown spectral features in the 150 MHz emission from pulsars with bandwidths as narrow as 0.5 MHz. The sources observed were CP 1919, CP 0950 and CP 1133.

M. M. Komesaroff

Papers

Possible mechanism for the pulsar radio emission.

Evidence in support of a rotational model for the pulsar PSR 0833-45

Measurements on the Period of the Pulsating Radio Source at 1919 + 21

Spaced Receiver Observations of Pulsed Radio Sources

Spectral Fine Structure in Pulsar Radiation