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NASA NTRS2000

Modelling Hard Gamma-Ray Emission from Supernova Remnants

The observation by the CANGAROO experiment of TeV emission from SN 1006, in conjunction with several instances of non-thermal X-ray emission from supernova remnants, has led to inferences of super-TeV electrons in these extended sources. While this is sufficient to propel the theoretical community in their modelling of particle acceleration and associated radiation, the anticipated emergence in the next decade of a number of new experiments probing the TeV and sub-TeV bands provides further substantial motivation for modellers. In particular, the quest for obtaining unambiguous gamma-ray signatures of cosmic ray ion acceleration defines a "Holy Grail" for observers and theorists alike. This review summarizes theoretical developments in the prediction of MeV-TeV gamma-rays from supernova remnants over the last five years, focusing on how global properties of models can impact, and be impacted by, hard gamma-ray observational programs, thereby probing the supernova remnant environment. Properties of central consideration include the maximum energy of accelerated particles, the density of the unshocked interstellar medium, the ambient magnetic field, and the relativistic electron-to-proton ratio. Criteria for determining good candidate remnants for observability in the TeV band are identified.

Baring, Matthew↗
NASA NTRS2002

Neutron Stars in Supernova Remnants

The grant provided funds for a conference entitled 'Neutron Stars in Supernova Remnants' held in Boston on 14-17 August 2001, in part to support invited speakers and students attending the meeting. The conference was completed on the specified dates and was a considerable success, attracting over 100 scientists from around the world. The conference included talks and papers on the most recent work in this field, including results from the Chandra X-ray Observatory, XMM-Newton, the Parkes Multibeam Pulsar Survey, the Very Large Array, and many other facilities. Theoretical work based on the latest results was also highlighted. The Proceedings of the conference have now been published as 'Neutron Stars in Supernova Remnants'. In addition, a large fraction of the papers from the conference have been submitted to astro-ph, and the volume in indexed through the Astronomical Data System.

Slane, Patrick↗
NASA NTRS1984

Ultraviolet observations of the peculiar supernova remnant in NGC 4449

IUE spectra were obtained of the emission region in the irregular galaxy NGC 4449 that has been identified as a young, oxygen-rich supernova remnant embedded in an H II region. The spectra show a blue continuum with a strong C IV 1550 P Cygni feature. Comparison to spectral standard stars observed with IUE shows similarities to O3-O7 V and early B Ia stars, indicating that massive young stars are present in the H II region. This comparison also indicates that the ultraviolet extinction in NGC 4449 may be peculiar. Careful inspection of the line-by-line data reveals a broad emission feature at 1657 A that may be semiforbidden O III emission from the supernova remnant. These observations are used in conjunction with shock model calculations to estimate limits on the relative abundances of carbon, silicon, and oxygen in the supernova remnant.

Blair, W. P.↗
NASA NTRS1978

Detection of star formation regions near supernova remnant W44

Observations of two infrared objects embedded in molecular clouds near the supernova remnant W44 are presented. W44-IRS1 offers compelling evidence that it is a star whose formation was recently induced by expansion of the supernova remnant. W44-IRS2 lies beyond the remnant, possibly apart from the region of its influence.

Wootten, A.↗
NASA NTRS2002

Chandra Observations of Supernova Remnants and Neutron Stars: An Overview

We present a brief overview of Chandra observations of supernova remnants and neutron stars, with emphasis on neutron stars in supernova remnants. The Chandra images demonstrate the importance of angular resolution in separating the neutron star emission from the surrounding nebulosity.

Weisskopf, Martin C.↗
NASA NTRS1993

An astrophysics data program investigation of spatial structure of supernova remnants

The final report on astrophysics data program investigation of spatial structure of supernova remnants for the period 1 Aug. 1989 to 31 Jul. 1991 is presented. The goal of the project was the study of the spatial structure of supernova remnants (SNR's) as observed in the x-ray band. A number of software tools were developed for the analysis: (1) a program to fit various geometric models to high resolution x-ray data, and (2) programs for Fourier Transform analysis of clumping in SNR's. These programs were applied to high resolution imager (HRI) data on the young galactic SNR's Tycho and Kepler with some success.

Hughes, John P.↗
NASA NTRS1994

An X-ray and optical study of the supernova remnant W44

We report the results of a 8000 s observation of the supernova remnant W44 using the ROSAT Position Sensitive Proportional Counter (PSPC). The image shows the same centrally peaked morphology observed by the Einstein IPC and contrasts with the shell-like radio morphology. The eastern limb shows a lack of X-ray emission within the radio shell, probably due to the interaction between the Supernova Remnants (SNR) and a molecular cloud. No counterpart to the pulsar 1853 + 01 in W44 has been detected, with L(sub X) less than 1.3 x 10(exp 32) ergs/s in the 0.2 to 2.4 keV band. The spectral analysis of the central part of W44, combining EXOSAT ME and Einstein SSS data, shows that the shocked plasma has not reached ionization equilibrium. The best nonequilibrium fit to PSPC, ME, and SSS spectra gives Eta = 10(exp 51) ergs cm(exp -6), T(sub s) = 10(exp 7) K with T(sub e) = T(sub i), suggesting conditions are approaching ionization equilibrium. There is no evidence of enhanced abundances of Mg, Si, S, or Fe. The variation of temperature and column density was obtained region by region using the PSPC and Einstein IPC. The temperature is largely uniform over the remnant, but strong column density variations are found to be consistent with molecular clouds in the line of sight. An evaporation model with a two-phase interstellar medium structure of clumps and interclump gas (White & Long 1991) can explain the X-ray centrally peaked morphology of W44. The clumps remaining behind a SN shock provide a reservoir of material, and evaporat e to increase the density of X-ray emitting gas in the interior of a SNR. The uniform temperature distribution of W44 strongly supports the predictions of this model. In addition, mosaiced H alpha and (S II) images of W44, taken using the prime focus universal extragalactic instrument (PFUEI) camera on the Palomar 60 sec telescope, reveal the first discovery of optical filaments (both H alpha and (S II)) in the northwestern and southeastern portion of the remnant, within the X-ray emitting region. The optical filaments and the X-ray image showing locally brighter emission and clumps along the filaments suggest both are produced by the interaction between the supernova shock front and regions of enhanced ambient density.

Rho, Jeongee↗
NASA NTRS1995

Supernovae, supernova remnants, and superbubbles

Supernovae, supernova remmants, and superbubbles in the interstellar medium are reviewed, with an emphasis on infrared studies of these phenomena. Superbubbles are likely to be relevant for understanding such Galactic and extragalactic issues as the photoionization of gas in the Galactic halo, 'superwinds,' and the contribution of 'starbursts' to photoionization of the intergalactic medium.

Shull, J. Michael↗
NASA NTRS1989

On evidence for quasi-parallel and quasi-perpendicular acceleration in supernova remnants

An attempt is made to determine whether or not the structure of supernova remnant shells is dependent on the angle between the line of sight and the Galactic magnetic field and if this structure can be explained either by quasi-parallel or quasi-perpendicular acceleration. The method used to determine the line of sight angles to the magnetic field is described. A model for the emissivity of a supernova remnant is developed.

Leckband, James A.↗
NASA NTRS1984

The nature of the filaments northeast of the supernova remnant IC 443

New optical spectrophotometry of the faint filaments northeast of the bright supernova remnant IC 443 show emission-line ratios very similar to those seen in the bright filaments of IC 443 and other supernova remnants. This suggests that these northeastern filaments also represent shock-heated interstellar gas and are not simply the southern boundary of the neighboring H II region S249 as previously suspected. If these filaments are associated with IC 443, they then reveal a much more extended remnant structure than previously assumed and permit a relatively accurate determination of IC 443's distance via its interaction with S249.

Fesen, R. A.↗
NASA NTRS2012

The Proper Motion of the Central Compact Object RX J0822-4300 in the Supernova Remnant Puppis A

Using the High Resolution Camera (HRC) aboard the Chandra X-ray Observatory, we have re-examined the proper motion of the central compact object RX J0822-4300 in the supernova remnant Puppis A. New data from 2010 August, combined with three archival data sets from as early as 1999 December, provide a baseline of 3886 days (more than 10 1/2 years) to perform the measurement. Correlating the four positions of RX J0822-4300 measured in each data set implies a projected proper motion of mu = 71 +/- 12 mas/yr. For a distance of 2 kpc this proper motion is equivalent to a recoil velocity of 672 +/- 115 km/s. The position angle is found to be 244 +/- 11 degrees. Both the magnitude and direction of the proper motion are in agreement with RX J0822-4300 originating near the optical expansion center of the supernova remnant. For a displacement of 371 +/- 31 arcsec between its birth place and today's position we deduce an age of (5.2 +/- 1.0) 10(exp 3) yrs for RX J0822-4300. The age inferred from the neutron star proper motion and filament motions can be considered as two independent measurements of the same quantity. They average to 4450 +/- 750 yrs for the age of the supernova remnant Puppis A.

Becker, Werner↗
NASA NTRS1999

Modelling Hard Gamma-Ray Emission from Supernova Remnants

The observation by the CANGAROO (Collaboration of Australia and Nippon Gamma Ray Observatory at Outback) experiment of TeV emission from SN 1006, in conjunction with several instances of non-thermal X-ray emission from supernova remnants, has led to inferences of super-TeV electrons in these extended sources. While this is sufficient to propel the theoretical community in their modelling of particle acceleration and associated radiation, the anticipated emergence in the next decade of a number of new experiments probing the TeV and sub-TeV bands provides further substantial motivation for modellers. In particular, the quest for obtaining unambiguous gamma-ray signatures of cosmic ray ion acceleration defines a "Holy Grail" for observers and theorists alike. This review summarizes theoretical developments in the prediction of MeV-TeV gamma-rays from supernova remnants over the last five years, focusing on how global properties of models can impact, and be impacted by, hard gamma-ray observational programs, thereby probing the supernova remnant environment. Properties of central consideration include the maximum energy of accelerated particles, the density of the unshocked interstellar medium, the ambient magnetic field, and the relativistic electron-to-proton ratio. Criteria for determining good candidate remnants for observability in the TeV band are identified.

Baring, Matthew G.↗
NASA NTRS2018

Expansion and Age of the X-Ray Synchrotron-Dominated Supernova Remnant G330.2+1.0

We report new Chandra observations of one of the few Galactic supernova remnants whose X-ray spectrum is dominated by nonthermal synchrotron radiation, G330.2+1.0. We find that between 2006 and 2017, some parts of the shell have expanded by about 1%, giving a free-expansion (undecelerated) age of about 1000 yr, and implying shock velocities there of 9000 km/s for a distance of 5 kpc. Somewhat slower expansion is seen elsewhere around the remnant periphery, in particular in compact knots. Because some deceleration must have taken place, we infer that G330.2+1.0 is less than about 1000 yr old. Thus, G330.2+1.0 is one of only four Galactic core-collapse remnants of the last millennium. The large size, low brightness, and young age require a very low ambient density, suggesting expansion in a stellar-wind bubble. We suggest that in the east, where some thermal emission is seen and expansion velocities are much slower, the shock has reached the edge of the cavity. The high shock velocities can easily accelerate relativistic electrons to X-ray-emitting energies. A few small regions show highly significant brightness changes by 10%–20%, both brightening and fading, a phenomenon previously observed in only two supernova remnants, indicating strong and/or turbulent magnetic fields.

Borkowski, Kazimierz J.↗
NASA NTRS1985

Excess gamma rays from the Loop I supernova remnant

Evidence is presented for an excess of cosmic ray intensity within the Loop I supernova remnant based on an interpretation of the observed distribution of gamma-rays across the remnant and the column densities of the associated gas. A strong case can thus be made for the bulk of the cosmic radiation (E , 10 to the 11th power eV) being produced in the Galactic supernova remnants.

Bhat, C. L.↗
NASA NTRS1983

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.

Becker, R. H.↗
NASA NTRS1997

High energy survey of supernova remnants with BATSE

The burst and transient source experiment (BATSE) survey of the high energy emission from supernova remnants is reported on. The ability of BATSE to continuously monitor the entire sky in the 20 keV to 2 MeV energy range enables a large group of remnants to by studied at high energies. Preliminary analysis indicates the likely detection of several supernova remnants other than the Crab nebula. Among these are MSH 15-52, Vela, Cas A and possibly HB 9. The techniques employed are discussed together with the status of the survey and its limitations.

McCollough, M. L.↗
NASA NTRS1977

Hot interstellar tunnels. I - Simulation of interacting supernova remnants

It has been suggested that intersecting supernova remnants (SNRs) contribute to the production of gas at about 1 million K which is apparently observed in the interstellar medium. This suggestion is evaluated through a fairly detailed numerical simulation that is used to investigate the large-scale three-dimensional behavior of a test section of the gaseous galactic disk under the influence of evolving and interacting SNRs. Models for a noninteracting 'isolated' SNR and the ambient medium are discussed, pairs of interacting remnants are examined along with the mechanism by which their central cavities can become connected, and the evolution of larger aggregates of SNRs is analyzed. Results are presented for a sequence of simulations having the same values of supernova blast energy, ambient ion density, and isolated SNR lifetime, but different supernova rates per unit volume. These results show that SNR intersections can quickly generate large volumes, or 'tunnels', of very hot gas from a cold starting medium under conservative and reasonable assumptions, the most important of which are that SNRs can be treated as spheres and mass motions can be treated implicitly.

Smith, B. W.↗