Vela Supernova Remnant Research Articles

Discovery of explosion fragments outside the Vela supernova remnant shock-wave boundary

THE nearby (500 pc) Vela supernova remnant has presented several puzzles. Its true shape has been difficult to determine1, and as a result it has never been clear whether the pulsar seen in that part of the sky resulted from the same explosion that created the remnant 2. Here we present an X-ray image of the Vela supernova remnant which shows that the pulsar is close to the centre, and therefore most probably resulted from the same explosion. We see six extended X-ray features outside the blast-wave front, which apparently originated close to the pulsar. We propose that these features result from the passage through the surrounding medium of fragments formed by instabilities during the collapse and subsequent explosion of the progenitor star.

ROSAT PSPC observation of the northeast region of the VELA supernova remnant. 1: Evidence of thermal structure on a scale of 5 min

ROSAT PSPC observation of the northeast region of the VELA supernova remnant. 1: Evidence of thermal structure on a scale of 5 min

A speckle hologram of the interstellar plasma

Observations of a speckle hologram of scattering material along the line of sight to the Vela pulsar indicate that this material is concentrated in the Vela supernova remnant, deep within the Gum Nebula. The speckle hologram is observed through the amplitude and phase variations of the interferometric cross-power spectrum with time and frequency. These variations describe the density fluctuations of the interstellar plasma, in a holographic fashion. The decorrelation due to the phase variations of the speckles yields the angular size of the scattering disk; comparison with the bandwidth of their amplitude variations yields a characteristic distance from earth to the scattering material of 0.81 +/- 0.03 of the distance from earth to the pulsar. This result is consistent with theories of irregularities associated with particle acceleration in shocks in supernova remnants.

Morphology and Physics of Supernova Remnants

AbstractSpectrally resolved X-ray images of the Cygnus Loop and the Vela supernova remnant have been obtained during the ROSAT all sky survey. The remnants show highly filamentary brightness distributions. Temperatures between 1·106 K and 10·106 K have been measured. Both remnants show significant deviation from thermal pressure equilibrium. The highest pressure excursions of up to a factor of 50 are associated with the X-ray brightest filaments. Pressure variations are expected for very recently shocked clouds, on a smaller scale though. In a limited search of the all sky survey data 14 extended objects have been found, which have tentatively been identified as previously unknown supernova remnants. A total number of ~ 60 new remnants are expected from the analysis of the full sky.

Evidence for a thermally unstable shock wave in the VELA supernova remnant

The emission and absorption line signatures of supernova remnant shock waves provide complementary diagnostic capabilities. This paper presents IUE spectra of the nebulosity and new spectra of HD 72088. Models of the emission and absorption lines from shocked gas are used to derive a shock velocity and elemental depletions. There is evidence from the absorption-line strengths and widths for thermally unstable cooling behind a 150 km/s shock. The shock velocity and swept-up column density estimates of Wallerstein and Balick (1990) are confirmed, and evidence is found for a nonthermal contribution to the pressure.

Low-frequency observations of the Vela supernova remnant and their implications

We have studied the Vela supernova remnant in the light of the 34.5 MHz observations made with the GEETEE low frequency array. The flux densities of Vela X and YZ at 34.5 MHz are estimated to be 1800 and 3900 Jy respectively. These values, along with those from earlier observa- tions at higher frequencies, imply spectral indices (S∝v α ) of -0.16 ± 0.02 for Vela X and -0.53 ± 0.03 for Vela YZ. This situation is further substantiated by the spectral-index distribution over the region obtained between 34.5 and 408 MHz. The spectral-index estimates, along with other known characteristics, strengthen the earlier hypothesis that Vela X is a plerion, while Vela YZ is a typical shell-type supernova remnant. We discuss the implications of this result.

Progress of the MOST Galactic Survey

AbstractThe Molonglo Observatory Synthesis Telescope (MOST), operating at a frequency of 843 MHz, is currently surveying the southern galactic plane between 245° <l<360° and −1.5°<b<1.5°. The resolution of the survey is 43″ (HPBW), providing radio continuum maps of unprecedented resolution and sensitivity (1 mJy/beam) in this part of the sky. The survey involves 12-hour synthesis observations of over four hundred fields, each extending over one degree. Eighty of these have been mapped in the past year, bringing the number now completed to three hundred. The survey is revealing many faint structures with intriguing morphology, including filamentary emission associated with the Vela supernova remnant, and a number of very weak (<5 mJy/beam) disc-like objects.

The proper motion of the VELA pulsar

The proper motion of the Vela pulsar using the Parkes-Tidbinbilla Interferometer has been measured over a 2 yr period and obtain a value of 49 + or - 5 mas/yr at a position angle 305 deg. This proper motion implies that the pulsar was not born at the geometric center of the Vela supernova remnant nor at the peak of radio emission in Vela X. It is concluded that Vela X is not pulsar-driven, and that, like many other Galactic supernova remnants, the Vela supernova remnant has expanded asymmetrically since its birth. 26 refs.

An X-ray investigation of crab-like supernova remnants

The Crab Nebula is the most noticeable object in our Galaxy, and the remnant of the famous Chinese guest star appeared in 1054AD, the best association between supernova remnants(SNR) and ancient guest stars. Before seventies, the Crab Nebula was considered as a special SNR with different morphology and physical features from that of most SNRs, Now more and more Crab-like SNRs have been detected(Weiler 1985). It is necessary to make a systematical investigation for the Crab-like SNRs, especially for those with central pulsars because they offer us more physical messages than others. The two associations SNR and PSR, the Crab Nebula with PSR 0531+21 and the Vela SNR with PSR 0833-45, were confirmed at the end of sixties and still were the only two associations before eighties. Recent years, PSR 1509-58 in MSH 15-52 and PSR 0540-69 in a SNR of l~(Seward & Harnden 1984, Seward etal. 1984) as well as PSR 1951+32 in CTB 80 ( Clifton et al. 1987, Fruchter etal. 1987 ) were discovered. On the other hand , the X-ray emission of PSR i055-52 and others were detected (Cheng & Helfand 1983, Helfand 1983). Recently, we searched for the X-ray emission of isolated pulsars over more than thirty fields in Einstein observation. By use of the same instrunent ealibrstions, the X-ray luminosities of ten isolated pulsars and their surrounding nebulae are obtained. Let L x be the total X-ray luminosity of a pulsar and its nebula in the 0.2-4.0 key band, and E be the rotating energy loss rate of the pulsar, the following statistical relation is obtained by linear regression and shown, as the line in Fig. 3.

An X-Ray Investigation of Crab-Like Supernova Remnants

The Crab Nebula is the most noticeable object in our Galaxy, and the remnant of the famous Chinese guest star appeared in 1054AD, the best association between supernova remnants(SNR) and ancient guest stars. Before seventies, the Crab Nebula was considered as a special SNR with different morphology and physical features from that of most SNRs, Now more and more Crab-like SNRs have been detected(Weiler 1985). It is necessary to make a systematical investigation for the Crab-like SNRs, especially for those with central pulsars because they offer us more physical messages than others.The two associations SNR and PSR, the Crab Nebula with PSR 0531+21 and the Vela SNR with PSR 0833-45, were confirmed at the end of sixties and still were the only two associations before eighties. Recent years, PSR 1509-58 in MSH 15-52 and PSR 0540-69 in a SNR of LMC(Seward & Harnden 1984, Seward etal. 1984) as well as PSR 1951+32 in CTB 80 (Clifton et al. 1987, Fruchter etal. 1987) were discovered. On the other hand, the X-ray emission of PSR 1055-52 and others were detected (Cheng & Helfand 1983, Helfand 1983). Recently, we searched for the X-ray emission of isolated pulsars over more than thirty fields in Einstein observation. By use of the same instrument calibrstions, the X-ray luminosities of ten isolated pulsars and their surrounding nebulae are obtained. Let Lx be the total X-ray luminosity of a pulsar and its nebula in the 0.2-4.0 kev band, and E be the rotating energy loss rate of the pulsar, the following statistical relation is obtained by linear regression and shown as the line in Fig. 1.

High-resolution IUE observations of interstellar absorption lines in the VELA supernova remnant

view Abstract Citations (78) References (34) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS High-resolution IUE observations of interstellar absorption lines in the VELA supernova remnant. Jenkins, E. B. ; Wallerstein, G. ; Silk, J. Abstract Ultraviolet spectra of 45 stars in the vicinity of the Vela supernova remnant were recorded by the short-wavelength echelle spectrograph aboard the International Ultraviolet Explorer (IUE). Over one-third of the stars show interstellar absorption lines at large radial velocities (greater than 60 km/s). The mapping of these high-velocity components in the sky suggests the motions are chaotic, rather than from a coherent expansion of the remnant material. In accord with earlier conclusions from Copernicus data, the gas at high velocity exhibits higher than normal ionization and shows substantially less depletion of nonvolatile elements than normal interstellar material at low velocities. Relatively strong lines from neutral carbon in the two excited fine-structure states indicate that the neutral clouds within the remnant have had their pressures enhanced by the passage of the blast wave from the supernova. Also, the remnant seems to show a significant enhancement in the abundances of low-velocity Si IV, C IV, and N V over those found in the general interstellar medium. Publication: The Astrophysical Journal Pub Date: March 1984 DOI: 10.1086/161832 Bibcode: 1984ApJ...278..649J Keywords: Interstellar Matter; Nebulae; Stellar Spectra; Supernova Remnants; Ultraviolet Spectra; Absorption Spectra; Abundance; Carbon; Interstellar Gas; Ionized Gases; Iue; Radial Velocity; Velocity Distribution; Astrophysics full text sources ADS | data products SIMBAD (45) MAST (1)

A compressed cloud in the VELA supernova remnant

Strong interstellar absorption lines of C I, arising from the two excited fine-structure levels, are found in IUE observations of HD 72350 (type B4 III). An analysis of the excited-level populations of C I gives local temperature and pressure limits, and auxiliary data on the limit of column density for excited O I and the carbon ionization help to establish that (1) the local temperature is within the limits of 25-100 K, and (2) the pressure/Boltzmann's constant ratio is at least 10 to the 4.3/cu cm K, despite its small size. This high-pressure cloud is discussed in terms of shock compression by the Vela supernova blast wave, along with the relationship of this kind of cloud compression to star formation and to the origin of the characteristic filamentary emission arcs seen in Vela and other supernova remnants

Secular Changes in the Flux Density of PSR 0833-45

The pulsar 0833-45 associated with the Vela supernova remnant has been known as a strong source with fairly constant pulse amplitude since its discovery (Large, Vaughan & Mills 1968) using the east-west arm of the Molonglo telescope. The pulse stability together with the short period of 89 ms allowed its integrated flux to be seen also as a 1.7 Jy point source with the pencil beam of the full Cross, and a more precise declination was obtained. Further observations in 1971/72 with a beat period integrator used on the fan beams of the north-south arm showed that the pulsed radiation had the same declination as the point source within 2 arcsec (Vaughan & McAdam 1973). Monitoring observations in 1975/76 gave an independent position, and the mean of all Molonglo (408 MHz), Fleurs (1415 MHz) and NRAO interferometer (2700 MHz) positions led to the optical detection of the pulsar (Goss et al. 1977). The point source, therefore, is reliably identified with the pulsar.

Ultraviolet spectroscopy of the Vela supernova remnant

A preliminary ultraviolet spectrum secured from the IUE satellite, of a bright filament in the Vela supernova remnant, displays both emission-line and continuum components. The emission-line spectrum shows the same anomalously low carbon-line strength reported previously for the Cygnus Loop. The continuum emission may be explained in terms of normal recombination processes in hydrogen and helium in a dense hot knot which dominates the field. The interpretation of the UV spectrum is supported by optical data for this region of Vela.

X-ray maps of the VELA supernova remnant

X-ray maps of the Vela supernova remnant in two energy channels, 0.1-0.4 keV and 0.4-0.8 keV, are presented. The data were obtained in 1975 from a SAS 3 satellite observation. We describe the Wiener filter technique used to deconvolve the angular response of the instrument from the data. The X-ray structure is compared with the optical and radio features of the region.

Shock waves in the interstellar medium

Calculations of the optical and UV emission-line intensities and column densities of ions observable in the optical and UV are presented for plane-parallel steady-state shock waves in the interstellar medium. The range of shock velocities considered is from 50 to 200 km/s, and preshock densities are between 1 and 300 per cu cm. The ionization state of the preshock gas is found to be an important parameter, and several sets of elemental abundances corresponding to various amounts of depletion onto grains are used. The results are compared with observations of the Cygnus Loop, the Vela supernova remnant, and Herbig-Haro objects.

Detection of change in rotation measure of the Vela pulsar

OBSERVATIONS made over the past six years show that the rotation measure of the Vela pulsar has increased by 14%, while over the same period the dispersion measure has shown a marginally significant decrease of about 0.2%. These results imply that a region containing a relatively strong magnetic field has moved across the path to the pulsar. This region of strong field is most probably associated with filamentary structure in the Vela supernova remnant.

Ultraviolet absorption lines associated with the VELA supernova remnant

Two stars behind the Vela supernova remnant and two stars offset from the remnant have been observed with the UV spectrometer aboard the Copernicus satellite. Over 200 interstellar atomic and molecular absorption features between 1000 and 1400 A have been identified and measured for radial velocity and equivalent width. In many cases, additional information was obtained by studying the detailed shapes of the recorded profiles. Most of the stars show several absorption components, with clouds of the highest radial velocity appearing in the spectra of stars behind the remnant. For each component, column densities were derived using velocity dispersion parameters which yielded the most self-consistent results. Qualitatively, the gas toward the remnant exhibits a number of unusual properties, when compared with normal interstellar material. First, abnormally high radial velocities were evident. Second, the degree of ionization of some elements suggested the existence of ionizing processes significantly more potent than those found in general regions of space. Finally, an investigation of electron densities shows that much of the gas, especially that at high velocity, must exist in the form of relatively thin sheets or filaments. If cosmic abundances prevail, the column densities of high-velocity excited material suggest that H-alpha emission measures could be as large as 100 sq cm/cu pc.

Interaction of the VELA supernova remnant with the cloudy interstellar medium

Using the Copernicus ultraviolet spectrometer, we have investigated interstellar absorption lines in the spectra of several stars behind the Vela supernova remnant. From observations of multiple velocity components ranging from +90 km s/sup -1/ to -180 km s/sup -1/ (and possibly even at -450 km s/sup -1/), some of which contain absorption by O VI, N V, and by fine-structure levels of C II and N II, we are able to demonstrate that the supernova must have interacted with a cloudy interstellar medium. The high-velocity gas is identified with shocked and compressed clouds, and is in the form of inhomogeneous filaments or sheets. In the low-velocity gas, analysis of the ionization trace elements, in particular for the ions S III, S IV, Si IV, N V, and O VI, suggests that we are observing clumpy gas in the immediate vicinity of the supernova remnant. We briefly describe a shock model for the observed gas, and emphasize the need for new optical observations of emission lines from the Vela region. (AIP)

Radius of the VELA pulsar

Lasker (1976) has proposed to identify a B roughly equals 23.7 mag star as thermal radiation from the hot neutron star associated with the Vela pulsar. It is shown that this identification, if correct, together with existing X-ray surveys of the Vela supernova remnant, requires that the radius of this pulsar certainly exceed 45 km, and probably 95 km.