Crab-like Remnants Research Articles

The Crab nebula and the class of Type IIn-P supernovae caused by sub-energetic electron-capture explosions

What sort of supernova gave rise to the Crab Nebula? There are several indications that the Crab arose from a sub-energetic explosion of an 8-10 Msun star, this appears to conflict with the high luminosity indicated by historical observations. This paper shows that several properties of the Crab are best suited to Type IIn-P explosions (Type IIn spectra with plateau light curves). These events probably arise from relatively low-energy (1e50 erg) explosions with low 56Ni yield resulting from electron-capture SNe (ecSNe), but their high luminosity and Type IIn spectra are dominated by shock interaction with CSM. After about 120 days, nearly all of the mass in the CSM and ejecta ends up in a slow dense shell. In the scenario proposed here for SN1054, this thin shell is accelerated by the growing pulsar wind nebula, producing the complex network of filaments seen today. There is no need to invoke the invisible fast SN envelope hypothesized to reside outside the Crab. SNeIIn-P explain several observed features of the Crab: (1) No blast wave or rapidly expanding SN envelope outside the filaments, (2) a total mass of 5 Msun swept up in a thin shell, (3) a high peak luminosity despite the low kinetic energy, and (4) chemical abundances consistent with an 8-10 Msun star and low 56Ni yield. A number of other implications are discussed, concerning other Crab-like remnants, dust in the Crab filaments, diversity in the initial masses of SNe IIn, and an association between ecSNe and SN impostors. This model predicts that if light echoes from SN1054 are discovered, they will be consistent with a Type IIn-P spectrum.

The extended X-ray halo of the Crab-like SNR G21.5-0.9

Recent XMM-Newton observations reveal an extended (150") low-surface brightness X-ray halo in the supernova remnant G21.5-0.9. The near circular symmetry, the lack of any limb brightening and the non-thermal spectral form, all favour an interpretation of this outer halo as an extension of the central synchrotron nebula rather than as a shell formed by the supernova blast wave and ejecta. The X-ray spectrum of the nebula exhibits a marked spectral softening with radius, with the power-law spectral index varying from Gamma = 1.63 +/- 0.04 in the core to Gamma = 2.45 +/- 0.06 at the edge of the halo. Similar spectral trends are seen in other Crab-like remnants and reflect the impact of the synchrotron radiation losses on very high energy electrons as they diffuse out from the inner nebula. A preliminary timing analysis provides no evidence for any pulsed X-ray emission from the core of G21.5-0.9.

ROSATandASCAObservations of the Crab‐like Supernova Remnant N157B in the Large Magellanic Cloud

We report the results of ROSAT and ASCA X-ray observations of the supernova remnant N157B (or 30 Dor B, SNR 0539-69.1) in the Large Magellanic Cloud. For comparison, we also briefly describe the results on SNR 0540-69.3, the only confirmed Crab-like remnant in the Cloud. The X-ray emission from N157B can be decomposed into a bright comet-shaped feature, superimposed on a diffuse emission region of a dimension $\sim 20$ pc. The flat and nearly featureless spectrum of the remnant is distinctly different from those of young shell-like remnants, suggesting a predominantly Crab-like nature of N157B. Characterized by a power law with an energy slope $\sim 1.5$, the spectrum of N157B above $\sim 2$ keV is, however, considerably steeper than that of SNR 0540-69.3, which has a slope of $\sim 1.0$. At lower energies, the spectrum of N157B presents marginal evidence for emission lines, which if real most likely arise in hot gas of the diffuse emission region. The hot gas has a characteristic thermal temperature of 0.4-0.7 keV. No significant periodic signal is detected from N157B in the period range of $3 \times 10^{-3}-2000$ s. The pulsed fraction is $\lesssim 9%$ (99% confidence) in the $2-7$ keV range. We discuss the nature of the individual X-ray components. In particular, we suggest that the synchrotron radiation of relativistic particles from a fast-moving ($\sim 10^3 km s^{-1}$) pulsar explains the size, morphology, spectrum, and energetics of the comet-shaped X-ray feature. We infer the age of the remnant as $\sim 5 \times 10^3$ yrs. The lack of radio polarization of the remnant may be due to Faraday dispersion by foreground \ion{H}{2} gas.

X-Ray Emission from the Supernova Remnant CTA 1

view Abstract Citations (40) References (22) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS X-Ray Emission from the Supernova Remnant CTA 1 Seward, F. D. ; Schmidt, B. ; Slane, P. Abstract Three pointings of the ROSAT PSPC have been used to map the X-ray emission of CTA 1. Emission is brightest at the center and extends in all directions to the boundaries of the remnant. The luminosity is model-dependent and (at 1.4 kpc), is, LX(0.1 24 keV) = 5-8 x 1034 ergs s-1. Emission from the center is harder and considerably brighter than that from the rim. Spectra from several parts of the remnant are fitted with two component models. Both a two-temperature thermal model and a model consisting of a power law and a soft thermal component produce good fits to all regions. The spectra do not allow us to distinguish between a remnant with hot evaporated material at the center, or an old Crab-like remnant. Both are plausible models for CTA 1. The ROSAT HRI was used to obtain an accurate location of a bright unresolved source within the remnant. This is identified as a background active galactic nucleus. Properties of eight weaker, unresolved X-ray sources within or nearby the remnant are tabulated. Publication: The Astrophysical Journal Pub Date: November 1995 DOI: 10.1086/176388 Bibcode: 1995ApJ...453..284S Keywords: GALAXIES: SEYFERT; ISM: INDIVIDUAL ALPHANUMERIC: CTA 1; ISM: SUPERNOVA REMNANTS; X-RAYS: ISM full text sources ADS | data products SIMBAD (14) NED (2) HEASARC (1)

84 gigahertz observations of five Crab-like supernova remnants

Flux density measurements at 3.6 mm have been made to extend the frequency coverage for three Crablike remnants and two Crablike components within remnants whose large-scale morphologies show shell-type structure. All five objects show flat, polarized, nonthermal radio spectra and associated X-ray emission characteristic of this class. The flux density is found to be lower than expected on the basis of an extrapolation of the spectrum from lower frequencies. If this is due to steepening caused by evolutionary effects, severe constraints can be put on the characteristics of the objects showing spectral steepening: all must be less than 2000 yr old, and the supernovae in which they were born must all have had very unusual properties. 30 refs.

An EXOSAT observation of CTB 80

The results of an EXOSAT observation of the Crab-like supernova remnant CTB 80 are presented. The 0.05-6 keV X-ray spectrum is well fitted by a power law with an energy index of 0.9, similar to that of other Crab-like remnants. This spectral measurement differs from an earlier result from an Einstein observation where a much steeper index was reported. This discrepancy results from the fact that the Einstein result is sensitive to the assumed line-of-sight absorption, whereas the EXOSAT result is not. A search for an X-ray counterpart to the 39.5 ms radio pulsations is reported; however, the X-ray source is too faint to usefully constrain the pulse amplitude. 21 references.

A Newly-Recognised Galactic Supernova Remnant with Shell-Type and Filled-Centre Features

While the number of galactic supernova remnants (SNRs) now known is fairly large (>150), the subset among these that are known to resemble the Crab Nebula is still distressingly small, about 15 or so (Green, 1984). Thus any object that can be unambiguously included in this exclusive club forms a valuable addition to our knowledge of this class. We report here observations of a newly recognised nonthermal galactic object, G18.94-l.06, having all the hallmarks of the classical shell-type SNRs, while also appearing to have a filled-centre component located inside the shell. Among the known Crab-like remnants, about one third show this dual nature (Green, 1984). This diagnosis of G18.94-1.06 is supported mainly by the variations in spectral index α (Sν∝ να) across the source, as seen between the two observation frequencies, 408 MHz and 5.0 GHz.

Small-Scale Structure in Young Supernova Remnants

AbstractRecent VLA observations of the shell supernova remnant SN 1006 AD (Reynolds and Gilmore 1986) and the Crablike remnant 3C 58 (SN 1181 AD?; Reynolds and Aller 1987) show features at high resolution that contain information on details of particle acceleration and transport in the remnants. Thin arcs at the edge of SN 1006 require time-variable particle acceleration and/or magnetic field amplification. Filaments in 3C 58 probably result from interaction of pulsar-generated relativistic fluid with filaments of thermal gas formed early in the remnant’s life by cooling or dynamical instabilities. Their sharp edges imply efficient scattering by Alfvén waves; as much as 1% of the large-scale magnetic energy density may be in magnetic turbulence on length scales of 1011 cm.

A radio search for Crab-like nebulae in M33

The results of a search for Crablike supernova remnants in M33 using the VLA and spectral indices and center-brightened morphology as discriminants are reported. The observations show that seven of the 12 are unresolved with a 0.3 arcsec beam. Of the five resolved sources, three have morphologies typical of background radio galaxies, and one may be a shell supernova remnant in M33. However, one 'source' is shown at high resolution to be composed of a complex of sources, mostly steep-spectrum, but containing one unresolved component with a flux at both frequencies of about 0.5 mJy. While this could be a Crablike remnant with a very flat spectrum, its properties are also consistent with those of a normal compact H II region. None of the other 11 objects fits the observational definition of a Crablike remnant. Thus M33 joins M31 and the Galaxy in exhibiting far fewer Crablike remnants than theory would predict.

High-resolution radio observations of the supernova remnant G24.7 + 0.6 and the discovery of an ultracompact H II region

The Crab-like SNR G24.7 + 0.6 with 12 arcmin resolution at 20 cm wavelength has been observed. The image reveals a bright Crab-like core surrounded by a faint shell. An ultracompact H II region lies adjacent to the remnant core and several other compact H II regions lie just outside the remnant shell. Optical, far-infrared, and X-ray observations of the region are also presented. The specific attributes of this remnant and its place in the classification of composite versus Crab-like remnants as well as the general question of the association between Crab-like remnants and H II regions are discussed.

Crab-Like Supernova Remnants

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.

No shell around 3C 58

VLA observations were made in a search for radio emission outside the Crablike remnant 3C 58, where the supernova ejecta might be expected to be interacting with the interstellar medium. No evidence for any such emission was found; the 3sigma surface-brightness limit at 1446 MHz is Sigma less than 1.1 micro-Jy/sq arcsec = 0.047 x 10 to the -20th W/sq m Hz sr. The interaction might be taking place at the edge of the observed remnant itself; however, a review of the morphological and spectral evidence for such interaction leads to the conclusion that a normal, steep-spectrum, limb-brightened shell is not an appreciable component of the observed emission. 30 references.

The decrease with time of the radio flux of the Crab Nebula

view Abstract Citations (46) References (6) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The decrease with time of the radio flux of the Crab nebula. Aller, H. D. ; Reynolds, S. P. Abstract Observations of the Crab Nebula at 8.0 GHz over the period 1968 - 1984 show a secular decrease in the flux density at a rate of -0.167%±0.015% yr-1. This observed value is in good quantitative agreement with the rate predicted by a theoretical model for the evolution of the Crab Nebula. The authors discuss inferences that can be made about the characteristic pulsar slowdown time scales in Crab-like remnants. Publication: The Astrophysical Journal Pub Date: June 1985 DOI: 10.1086/184494 Bibcode: 1985ApJ...293L..73A Keywords: Crab Nebula; Decay Rates; Pulsars; Radiant Flux Density; Orion Nebula; Supernova Remnants; Time Response; Astrophysics full text sources ADS | data products SIMBAD (2)

A new class of nonthermal radio sources

Current radio catalogues1,2 list some 145 sources as galactic supernova remnants which are included primarily on the basis of their exhibiting a nonthermal radio spectrum, evidence for extended emission and being located within a few degrees of the galactic plane. Detailed maps including spatially-resolved spectral information and polarimetric data have been obtained for about half of the catalogued objects, primarily those lying within ∼5 kpc of the Sun, and have revealed three classes of remnants: shell-like sources, Crab-like synchrotron nebulae and composite remnants3,4 containing a central Crab-like component surrounded by a shell. While mapping many of the remnants not well studied to date, we have discovered at least two nonthermal extended objects which defy classification in any of these categories. The two sources exhibit a marked axial symmetry with evidence for a compact component at one extreme of the axis. Their diffuse emission includes bright filamentary structures superimposed on a lower surface brightness component which gradually fades, becoming undetectable at the end of the axis opposite the compact source. The mean spectral indices of these sources are intermediate between the shell- and Crab-like remnants. We propose here that these objects are representative of a new class of nonthermal radio sources; elsewhere in this issue5, we suggest that such sources are formed through the emission of relativistic particles produced by high-velocity accreting binary systems.

Discovery of a 50 millisecond pulsar in the Large Magellanic Cloud

The present investigation is concerned with the discovery of a new pulsed X-ray source in the Large Magellanic Cloud (LMC) supernova remnant 0540 - 693. The SNR 0540 - 693 is one of three suspected Crab-like remnants in the LMC. The existing X-ray, optical, and radio observations of the remnant itself are discussed, and an analysis is conducted of the implications of the period, period derivative, and X-ray pulse shape of the new source. It is concluded that the pulsed X-ray source is almost certainly a young, isolated pulsar. Many of its properties are very similar to those of the Crab pulsar.

VLA observations of compact radio sources in the galactic plane - A search for Crab-like supernova remnants

view Abstract Citations (17) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS VLA observations of compact radio sources in the galactic plane : a search for Crab-like supernova remnants. Helfand, D. J. ; Chance, D. ; Becker, R. H. ; White, R. L. Abstract In a search for Crab-like supernova remnants in the Galaxy, 19 compact (<1arcmin.5) radio sources were observed with the VLA. Only the previously known supernova remnant (SNR) G21.5-0.9 has both a centrally peaked brightness distribution and integrated polarization greater than 5%, properties characteristic of Crab-like remnants. The remaining objects are either compact H II regions or extragalactic sources. The authors use these results to set a limit of ⪉5 on the number of undiscovered Crab-like SNR which exist in the Galaxy above a 6-cm flux density of 1 Jy. The implication of this result for the formation rate of galactic Crab-like remnants is discussed. Publication: The Astronomical Journal Pub Date: June 1984 DOI: 10.1086/113576 Bibcode: 1984AJ.....89..819H Keywords: Milky Way Galaxy; Radio Sources (Astronomy); Supernova Remnants; Astronomical Catalogs; Astronomical Maps; Morphology; Polarization Characteristics; Astronomy full text sources ADS | data products SIMBAD (18)

G29.7-0.3: another supernova remnant with an identity crisis

New radio and X-ray observations of the galactic supernova remnant G29.7-0.3 show that it is composed of two spectrally distinct components: a steep-spectrum, incomplete shell 3 arcmin in extent enclosing a flat-spectrum, X-ray emitting region 30 arcsec across. Thus, G29.7-0.3 joins the ranks of supernova remnants which exhibit a combination of Crab-like and shell remnant attributes. The Crab-like core has the highest ratio of X-ray radio luminosity of all the Crab-like remnants observed to date, suggesting that it is an extremely young object.

X-ray Observations of Crab-Like Supernova Remnants

On the basis of extensive radio surveys of the galactic plane, approximately 140 sources of diffuse radio emission have been classified as supernova remnants (SNR). Using spectral index and spatial distribution as the primary selection criteria, these have been subdivided into two groups, “shell” and “Crab-like”. In each case, the radio emission is assumed to be of non-thermal origin. The two distinct morphologies arise from two distinct energy sources. For shell remnants, the energy is drawn from the reservoir of kinetic energy in the expanding shock front; in Crab-like remnants, the energy is drawn from the rotational kinetic energy of a central stellar remnant.These two classes of remnants differ significantly in their x-ray emission. With few exceptions, radio shell remnants emit thermal x-rays from shock heated gas which is itself distributed in a shell. Crab-like sources (as defined by their radio properties) emit synchrotron x-rays in a centrally-peaked spatial distribution. Presumably, the x-ray emission from these objects is an extension of the radio spectrum. Crab-like sources have a high probability of containing a compact (unresolved) source of x-ray emission which in analogy to the Crab Nebula, is identified as the central stellar remnant.The general absence of either compact x-ray sources or Crab-like diffuse nebulae within shell sources indicates that active pulsars are not usually formed in SN events which eventually form shell sources. However, there are several examples of remnants which share both shell and Crab-like characteristics so we cannot rule out an evolutionary connection between these two classes of SNR.

High-Resolution Maps of Two Supernova Remnants

High-resolution radio maps of supernova remnants (SNRs) are indispensable for distinguishing the more common shell remnants from the centrally concentrated (Crab-like) remnants; such studies also reveal any departures from symmetry, and this can yield vital information concerning interaction of the ejecta with the surrounding interstellar medium.

An X-ray study of two Crablike supernova remnants - 3C 58 and CTB 80

The instruments on the Einstein Observatory have been used to study the X-ray properties of two Crablike SNRs: 3C 58 and CTB 80. Images of the objects are similar, showing an extended plateau of emission surrounding a pronounced central maximum consistent with the presence of a point source. The X-ray spectrum of 3C 58 is consistent with a power law of spectral index 0.5 + 0.5 or -0.2 modified by absorption in a hydrogen column density N sub H of (2 + or - 0.5) x 10 to the 21st/sq cm. These data suggest an analogy with the Crab Nebula, where the extended X-ray emission is nonthermal and the pointlike emission emanates from a central neutron star. Quantitative comparisons of the X-ray and radio properties for six Crablike remnants indicate significant differences which may reflect an evolutionary sequence.