The Crab pulsar echoes

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

Radio Observations of the Crab Nebula Pulsar

10.1017/s0074180900007233 ◽

1971 ◽

Vol 46 ◽

pp. 73-83

Author(s):

F. D. Drake

Keyword(s):

Multipath Propagation ◽

Crab Nebula ◽

Crab Pulsar ◽

Great Intensity ◽

Radio Observations ◽

Radiated Power ◽

Propagation Effects ◽

The radio properties of the Crab Nebula pulsar are reviewed. The pulsar lies at the centre of the Crab Nebula and has a period of 33 msec. Its increase in period with time releases an amount of energy which is equal in magnitude to the total radiated power. Instabilities in the period of the Crab pulsar have been discovered with timescales ranging from days to months. The length of the pulse increases at longer wavelengths due apparently to multipath propagation effects. A characteristic of the Crab pulsar is the great intensity of the occasional pulse.

X-ray Study of the Crab Nebula and the Crab and Vela Pulsars

10.1017/s0074180900033775 ◽

1983 ◽

Vol 101 ◽

pp. 131-138

Author(s):

F. R. Harnden

Keyword(s):

Crab Nebula ◽

Large Majority ◽

X Ray ◽

The Past ◽

The Crab Nebula ◽

Scientific Questions

The Crab Nebula has been intensely studied by X-ray astronomers ever since its discovery as the first, optically identified X-ray object (Bowyer et al. 1964); and a large majority of X-ray experiments during the past two decades have observed the Crab, seeking not only the answers to scientific questions but also assurance that the instruments' calibrations were understood. It is therefore no surprise that, following its launch in 1978 November, the Einstein X-ray Observatory too had the Crab Nebula on its list of mandatory targets.

Superfluidity in Neutron Stars

10.1017/s0074180900099988 ◽

1974 ◽

Vol 53 ◽

pp. 151-165

Author(s):

George Greenstein

Keyword(s):

Neutron Star ◽

Neutron Stars ◽

Crab Nebula ◽

Crab Pulsar ◽

X Ray ◽

Effects Of Rotation ◽

We present a short Cook's tour of the possible effects of rotation coupled with superfluid properties of neutron star interiors. A suggestion is made to take advantage of forthcoming lunar occultations of the Crab Nebula in order to search for blackbody X-ray emission from the Crab pulsar.

Diffusion and advection model for particle transport in young pulsar wind nebulae

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312023812 ◽

2012 ◽

Vol 8 (S291) ◽

pp. 265-268

Author(s):

Xiaping Tang ◽

Roger A. Chevalier

Keyword(s):

Spectral Index ◽

Particle Transport ◽

Crab Nebula ◽

Outer Boundary ◽

Outer Part ◽

Pulsar Wind Nebulae ◽

Pure Diffusion ◽

Pulsar Wind ◽

Kink Instability ◽

AbstractThe magnetohydrodynamic (MHD) model for young pulsar wind nebulae (PWN) has been successful in reproducing many features of the nebulae. The model is characterized by a termination shock (TS) between the PWN and unshocked pulsar wind. Relativistic particles are injected at the TS and follow an advective flow to the outer boundary. However, toroidal structure of well studied young PWN like the Crab Nebula, 3C 58 and G21.5-0.9 is only present in the region close to the TS. In the outer parts of the nebulae, filamentary and loop-like structure is observed. Also, the radial variation of spectral index due to synchrotron losses is smoother than expected in the MHD flow model. We find that a pure diffusion model with energy independent diffusion and a transmitting boundary can reproduce the basic data on nebular size and spectral index variation for the Crab, 3C 58, and G21.5-0.9. Energy dependent diffusion is also discussed. Power law variations of the coefficient with energy are degenerate with variation in the input particle energy distribution index in the steady state case. Monte Carlo simulations of particle transport with both diffusion and advection for the Crab nebula and 3C 58 suggest a picture in which advection dominates the inner part of the PWN where toroidal structure is clearly present. Diffusion dominates the outer part of the PWN where filamentary and loop-like structure is observed. The source of the chaotic field is uncertain, but may be related to Rayleigh-Taylor instability at the outer boundary of young nebulae and/or the kink instability of the toroidal magnetic field.

Relationship Between Scattering and Dispersion Measure of the Crab Nebula Pulsar

Astronomy Reports ◽

10.1134/s1063772919090051 ◽

2019 ◽

Vol 63 (10) ◽

pp. 830-834

Author(s):

B. Ya. Losovsky ◽

D. V. Dumsky ◽

Yu. A. Belyatsky

Keyword(s):

Crab Nebula ◽

Dispersion Measure ◽

Faraday Rotation of the Crab Pulsar Radiation

10.1017/s0074180900007312 ◽

1971 ◽

Vol 46 ◽

pp. 118-118

Author(s):

R. N. Manchester

Keyword(s):

Faraday Rotation ◽

Radio Astronomy ◽

Crab Nebula ◽

Position Angle ◽

Crab Pulsar ◽

Astronomy Observatory ◽

Pulsar Radiation ◽

Rotation Measure ◽

The Mean ◽

During April, 1970, the 300-ft telescope of the National Radio Astronomy Observatory was used to determine the mean polarisation of the Crab Nebula pulsar radiation at several frequencies around 400 MHz. The position angle of the highly polarised precursor measured at each frequency, corrected for ionospheric Faraday rotation and plotted against inverse frequency squared is shown in Figure 1. The observed variation of the position angle with frequency is consistent with Faraday rotation of the plane of polarisation with a rotation measure of −40.5 ± 4.5 rad/m2. This value is of the same sign but larger than the rotation measure for the nebular radiation in the vicinity of the pulsar.

Optical Observations of the Crab Pulsar, and Searches for other Optical Pulsars

10.1017/s0074180900007257 ◽

1971 ◽

Vol 46 ◽

pp. 87-90

Author(s):

Jerome Kristian

Keyword(s):

Optical Properties ◽

Light Curve ◽

Total Energy ◽

Crab Nebula ◽

Optical Observations ◽

Crab Pulsar ◽

Time Variations ◽

Optical Wavelengths ◽

High Degree ◽

The optical properties of the Crab nebula pulsar are reviewed. The Crab nebula pulsar has a high degree of constancy at optical wavelengths. No time variations over short or long periods have been detected; the light curve is nearly the same in all colors. The intensity and color of the pulsar are V = 16.5, B − V = +0.5, U − B = −0.45 and V − R = −0.75. There is no precursor as found at radio wavelengths and the main pulse contains 65 per cent of the total energy. No lines have been detected.Searches for other pulsars have been unsuccessful.

Search for Plerions in the Direction of Two Young Pulsars

10.1017/s0074180900160590 ◽

1987 ◽

Vol 125 ◽

pp. 124-124

Author(s):

S. Krishnamohan ◽

D.K. Mohanty ◽

A.R. Patnaik ◽

T. Velusamy

Keyword(s):

Supernova Remnants ◽

Large Scale ◽

Galactic Plane ◽

Crab Nebula ◽

Dispersion Measure ◽

Positional Error ◽

Continuum Source ◽

Interesting Possibility ◽

Average Flux ◽

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.

The Crab Pulsar and Nebula as Seen in Gamma-Rays

Universe ◽

10.3390/universe7110448 ◽

2021 ◽

Vol 7 (11) ◽

pp. 448

Author(s):

Elena Amato ◽

Barbara Olmi

Keyword(s):

Gamma Ray ◽

Crab Nebula ◽

High Energy ◽

Crab Pulsar ◽

Gamma Ray Astronomy ◽

Very High Energy ◽

Energy Gamma ◽

The Crab Nebula ◽

The Impact ◽

Very High

Slightly more than 30 years ago, Whipple detection of the Crab Nebula was the start of Very High Energy gamma-ray astronomy. Since then, gamma-ray observations of this source have continued to provide new surprises and challenges to theories, with the detection of fast variability, pulsed emission up to unexpectedly high energy, and the very recent detection of photons with energy exceeding 1 PeV. In this article, we review the impact of gamma-ray observations on our understanding of this extraordinary accelerator.

Plasma Theory of Two Synchrotron Knots’ formation Discovered in the Crab Nebula

International Astronomical Union Colloquium ◽

10.1017/s0252921100060425 ◽

2000 ◽

Vol 177 ◽

pp. 505-506

Author(s):

David Shapakidze ◽

George Machabeli

Keyword(s):

Synchrotron Radiation ◽

Crab Nebula ◽

Crab Pulsar ◽

Electron Positron ◽

Radiation Sources ◽

Plasma Theory ◽

AbstractThe plasma mechanism of synchrotron knots’ formation discovered in the Crab Nebula at the distances 0″.65 (1016cm) and 3″.8 (6 × 1016cm) from the Crab pulsar is presented. The mechanism is based on exitation of cyclotron and Cherenkov-drift instabilities in the relativist s electron-positron plasma of the nebula. The higher luminosity of the knots is supposed due to the orientation of the direction of motion of the synchrotron radiation sources (Larmor circles) relative to the observer.