We discuss the generic characteristics of stochastic particle acceleration by a fully developed turbulence spectrum and show that resonant interactions of particles with high speed waves dominate the acceleration process. To produce the relativistic electrons inferred from the broadband spectrum of a few well-observed shell-type supernova remnants in the leptonic scenario for the TeV emission, fast mode waves must be excited effectively in the downstream and dominate the turbulence in the subsonic phase. Strong collisionless non-relativistic astrophysical shocks are studied with the assumption of a constant Aflven speed. The energy density of non-thermal electrons is found to be comparable to that of the magnetic field. With reasonable parameters, the model explains observations of shell-type supernova remnants. More detailed studies are warranted to better understand the nature of supernova shocks.
The development of observational techniques has inriched our knowledge of supernova remnants. In this paper, we review the main progresses in the last decade, including new discoveries of supernova remnants and the associated (rare type of) pulsars, nucleosynthesis, the interaction between supernova remnants and molecular clouds, dust in the supernova remnants, shock physics, and cosmic ray accelerations.
Supernova remnants are usually analysed in the light of hydrodynamical models of the interaction of supernova ejecta with either a constant density ambient medium or a circumstellar medium produced by a constant presupernova wind. However, the ejection of energetic wind during the presupernova phase changes the ambient medium structure and, consequently, the early supernova remnant evolution. We have analysed the evolution of young remnants of type Ia supernovae, focusing on the imprint of the presupernova wind history on the supernova remnant structure and on the influence of the explosion me…
We have used archival ROSAT data to present X-ray images of thirty-one supernova remnants (SNRs) in the Large Magellanic Cloud (LMC). We have classified these remnants according to their X-ray morphologies, into the categories of Shell-Type, Diffuse Face, Centrally Brightened, Point-Source Dominated, and Irregular. We suggest possible causes of the X-ray emission for each category, and for individual features of some of the SNRs.
October 2004 marks the 400th anniversary of the sighting of SN 1604, now marked by the presence of an expanding nebulosity known as Kepler's supernova remnant. Of the small number of remnants of historical supernovae, Kepler's remnant remains the most enigmatic. The supernova type, and hence the type of star that exploded, is still a matter of debate, and even the distance to the remnant is uncertain by more than a factor of two. As new and improved multiwavength observations become available, and as the time baseline of observations gets longer, Kepler's supernova remnant is slowly revealing …
We present the results of three observations of shell-type supernova remnants observed by BeppoSAX. Two of the remnants (N132D and Cas A) are oxygen rich supernova remnants. They were observed during the PV phase. SN1006 was observed during A01. For SN1006 we present preliminary results on the abundance measurements based on the emission from the center of the remnant.
In this paper we discuss possible ultra high energy ($\ge$ TeV) neutrino emission from Supernova Remnants (SNRs), specifically the hadronic gamma ray production models. Recent very high energy (VHE) $γ$ ray observation from SNRs is the main motivation behind this study.
Supernovae descendent from massive stars explode in media that have been modified by their progenitors' mass loss and UV radiation. The supernova ejecta will first interact with the circumstellar material shed by the progenitors at late evolutionary stages, and then interact with the interstellar material. Circumstellar nebulae in supernova remnants can be diagnosed by their small expansion velocities and high [N II]/H$α$ ratios. The presence of circumstellar nebulae appears ubiquitous among known young supernova remnants. These nebulae can be compared to those around evolved massive stars to …
The interaction between the ejecta from Supernova 1987A and surrounding material is producing steadily brightening radio and X-ray emission. The new-born supernova remnant has been significantly decelerated by this interaction, while its morphology reflects the axisymmetric nature of the progenitor wind.
I briefly summarize some facts and ideas concerning the presence of neutron stars in Supernova remnants. While sources similar to the Crab Nebula require the presence of a central energetic object, shell-type remnants such as Cas A are compatible with the presence of neutron stars releasing a weak relativistic wind.
Supernovae (SN) and supernova remnants (SNR) have key roles in galaxies, but their physical descriptions is still incomplete. Thus, it is of interest to study neutrino radiation to understand SN and SNR better. We will discuss: (1) The ~10 MeV thermal neutrinos that arise from core collapse SN, that were observed for SN1987A, and can be seen with several existing or planned experiments. (2) The 10-100 TeV neutrinos expected from galactic SNR (in particular from RX J1713.7-3946) targets of future underwater neutrino telescopes.
We propose that some of the unidentified Galactic plane (-10 degrees < b < 10 degrees) sources listed in the first EGRET catalog (Fichtel et al. 1994) are associated with nearby supernova remnants. The probability that the association of strong EGRET sources with supernova remnants is due to chance alignment is found to be < 1/2200. Three of the most convincing associations are radio-bright, nearby shell remnants and a fourth is associated with a plerion. We examine possible gamma-ray production mechanisms and conclude that pion production and decay from high-energy protons interacting with th…
The launch of Chandra and XMM-Newton has led to important new findings concerning the X-ray emission from supernova remnants. These findings are a result of the high spatial resolution with which imaging spectroscopy is now possible, but also some useful results have come out of the grating spectrometers of both X-ray observatories, despite the extended nature of supernova remnants. The findings discussed here are the evidence for slow equilibration of electron and ion temperatures near fast supernova remnant shocks, the magnetic field amplification near remnant shocks due to cosmic ray accele…
A review of the main issues in the field of particle acceleration in Supernova Remnants is provided in the context of future X-ray observations with Simbol-X. After a summary of the nonthermal acceleration mechanisms at work, I briefly review the observations of supernova remnants in hard X-rays and in gamma rays. Open issues are discussed in this framework.
After reviewing recent work on the dynamics of young supernova remnants (YSNRs) and discussing how YSNRs can be used as physics laboratories, I discuss several challenges: Where are the very young SNRs in the Galaxy? Can very young SNRs produce gamma ray bursts? The Connections Challenge: Can one infer the nature of the supernova and its progenitor star from observations of the YSNR?
This brief review of recent X-ray observations of young supernova remnants highlights results obtained by the Chandra and XMM Newton Observatories since their launch last year. Their impressive capabilities are illustrated by results for spectral imaging, and for spatially resolved spectroscopy that isolates emission from individual ejecta knots and from the forward shock. I also review X-ray dynamical studies of supernova remnants, which should undergo significant advances during this new era.
We discuss a concept of off-centred cavity supernova explosion as applied to neutron star/supernova remnant associations and show how this concept could be used to preclude the anti-humane decapitating the Duck (G5.4-1.2 + G5.27-0.9) and dismembering the Swan (Cygnus Loop), as well as to search for a stellar remnant associated with the supernova remnant RCW86.
Radio images of supernova remnants in the framework of diffusion model are discussed. The distribution profiles of synchrotron radiation intensity for spherical injection source of relativistic electrons are reduced at different frequencies. An explanation of the observational data obtained on UTR-2, according to which the size of the supernova remnant at decametric waves is larger than the remnant size at high frequencies, is given.
The results of the 2D modelling of Supernova remnant (SNR) RCW86 are given. Models of this remnant, which for the first time interpret the anisotropy of surface brightness as a result of the evolution of adiabatic SNR in the interstellar medium with a large-scale gradient of density, are considered. Estimations on the basic characteristics of RCW86 and the surrounding medium which follow from these models are found. It is shown that the observed surface brightness distribution of RCW86 may be obtaned in the both proposed up till now models with different initial assumptions: one about a Supern…
There are a half-dozen or so young supernova remnants in the Magellanic Clouds that display one or more of the following characteristics: high velocity (>1000 km/s) emission, enhanced metallicity, or a rapidly rotating pulsar. I summarize the current state of knowledge of these remnants and present some recent results mostly from the new X-ray astronomy satellites.
We have obtained high resolution Ca II and Na I absorption line spectra toward 68 OB stars in the direction of the Vela Supernova Remnant. The stars lie at distances of 190 -- 2800 pc as determined by Hipparcos and spectroscopic parallax estimations. The presence of high velocity absorption attributable to the remnant along some of the sight lines constrains the remnant distance to 250+/-30 pc. This distance is consistent with several recent investigations that suggest that the canonical remnant distance of 500 pc is too large.
The successful theoretical supernova explosion models should be able to explain any features of the emission from supernovae at any evolutionary stage. We check several models from two different points of view. With the multi-frequency radiation hydro code STELLA we calculate gamma-ray, bolometric and broad-band UBVI light curves. Then we use the same models to calculate the emission from young supernova remnants. Here we present new plots for gamma-ray luminosity from several SN Ia models and recomputations of bolometric and UBVRI light curves of model 13C for SN 1993J.
We explore the relationship between the models for progenitor systems of Type Ia supernovae and the properties of the supernova remnants that evolve after the explosion. Most models for Type Ia progenitors in the single degenerate scenario predict substantial outflows during the presupernova evolution. Expanding on previous work, we estimate the imprint of these outflows on the structure of the circumstellar medium at the time of the supernova explosion, and the effect that this modified circumstellar medium has on the evolution of the ensuing supernova remnant. We compare our simulations with…
We have carried out a sensitive search for young pulsars associated with supernova remnants using the 76-m Lovell radio telescope at Jodrell Bank. The observations were made at 606 MHz using a system with a bandwidth of 8 MHz and a set noise temperature on cold sky of about 50 K. The survey targeted 33 remnants in the northern hemisphere and achieved a nominal sensitivity of ~1 mJy in most cases. Two pulsars were discovered in the course of this survey and the known pulsar PSR B1952+29 was detected. The new pulsars, J0215+6218 and J1957+2831, were found during searches of the supernova remnant…
We summarise the proceedings of the SRCfTA workshop on ``Supernova Remnants, Pulsars and the Interstellar Medium'' that was held at the University of Sydney on Mar 18 and 19, 1999.
We summarize the current observational evidence for associations between supernova remnants and neutron stars, including radio pulsars, proposed "inactive" young neutron stars, "anomalous" X-ray pulsars, and soft gamma-ray repeaters, and argue that the paradigm that all young neutron stars are Crab-like requires reconsideration.
The last ten years a number of observational advances have substantially increased our knowledge of shock phenomena in supernova remnants. This progress has mainly been made possible by the recent improvements in X-ray and Gamma-ray instrumentation. It has become clear that some shell-type supernova remnants, e.g. SN 1006, have X-ray emission dominated by synchrotron radiation, proving that electrons are accelerated up to 100 TeV. This is still an order of magnitude below 3E15 eV, at which energy the ion cosmic ray spectrum at earth shows a spectral break. So one of the major goals is to prove…
Important results achieved over the last years on supernova remnants, planetary nebulae and superbubbles are briefly reviewed in the context of X-ray observations. I intend to review the important open scientific questions in these fields, and the specific contributions that can be made by XMM-Newton.
We briefly summarize the survey of HI 21 cm emission lines to search for shocked atomic gas associated with Galactic supernova remnants (SNRs) in the southern sky. For G347.3-0.5, we discuss the distance to the SNR and the implications of the HI results.
Anisotropic thermal conduction plays an important role in various astrophysical systems. One of the most stringent tests of thermal conduction can be found in supernova remnants. In this paper we study anisotropic thermal conduction and examine the physical nature of the flux of thermal conduction in the classical and saturated limits. We also present a temporally second-order accurate implicit-explicit scheme for the time-update of thermal conduction terms within a numerical MHD scheme. Several simulations of supernova remnants are presented for a range of ISM parameters. The role of thermal …
We report the discovery of a partial ~2deg. diameter non-thermal radio shell coincident with Taz, the pulsar wind nebula (PWN) in the error box of the apparently variable gamma-ray source 3EG J1809-2328. We propose that this radio shell is a newly identified supernova remnant (SNR G7.5-1.7) associated with the PWN. The SNR surrounds an amorphous region of thermal X-rays detected in archival ROSAT and ASCA observations putting this system in the mixed-morphology class of supernova remnants. G7.5-1.7 is the fifth such supernova remnant coincident with a bright GeV source, and the fourth containi…
We propose to use the thermal X-ray emission from young supernova remnants (SNRs) originated in Type Ia supernovae (SNe) to extract relevant information concerning the explosion mechanism. We focus on the differences between numerical 1D and 3D explosion calculations, and the impact that these differences could have on young SNRs. We use the remnant of the Tycho supernova (SN 1572) as a test case to compare with our predictions, discussing the observational features that allow to accept or discard a given model.
The evidence for associations between neutron stars and supernova remnants is reviewed. After summarizing the situation for young radio pulsars, I consider the evidence from associations that young neutron stars can have properties very different from those of radio pulsars. This, though still controversial, shakes our simple perception of the Crab pulsar as prototypical of the young neutron star population.
We have made VLA images of the fields around three young pulsars which have resulted in the discovery of two new supernova remnants and confirmation of a third. We argue that, in at least two cases and perhaps the third, the pulsars are physically associated with these supernova remnants. A review of all known young pulsars shows that the majority are associated with supernova remnants. We show that the typical density of the interstellar medium into which the supernova remnants are evolving has a density of 0.2 cm$^{-3}$ instead of the low value of 0.01 cm$^{-3}$ which had been calculated fro…
This paper reviews recent advances in the study or circumstellar masers and masers found toward supernova remnants. The review is organized by science focus area, including the astrophysics of extended stellar atmospheres, stellar mass-loss processes and outflows, late-type evolved stellar evolution, stellar maser excitation and chemistry, and the use of stellar masers as independent distance estimators. Masers toward supernova remnants are covered separately. Recent advances and open future questions in this field are explored.
This paper presents archival ROSAT PSPC observations of the G65.2+5.7 supernova remnant (also known as G65.3+5.7). Little material obscures this remnant and so it was well observed, even at the softest end of ROSAT's bandpass (~0.11 to 0.28 keV). These soft X-ray images reveal the remnant's centrally-filled morphology which, in combination with existing radio frequency observations, places G65.2+5.7 in the thermal composite (mixed morphology) class of supernova remnants. Not only might G65.2+5.7 be the oldest known thermal composite supernova remnant, but owing to its optically revealed cool, …
We present a review of the first six years of Chandra X-ray Observatory observations of supernova remnants. From the official "first-light" observation of Cassiopeia A that revealed for the first time the compact remnant of the explosion, to the recent million-second spectrally-resolved observation that revealed new details of the stellar composition and dynamics of the original explosion, Chandra observations have provided new insights into the supernova phenomenon. We present an admittedly biased overview of six years of these observations, highlighting new discoveries made possible by Chand…
A spherically symmetric model is presented for the interaction of a pulsar wind with the associated supernova remnant. This results in a pulsar wind nebula whose evolution is coupled to the evolution of the surrounding supernova remnant. This evolution can be divided in three stages. The first stage is characterised by a supersonic expansion of the pulsar wind nebula into the freely expanding ejecta of the progenitor star. In the next stage the pulsar wind nebula is not steady; the pulsar wind nebula oscillates between contraction and expansion due to interaction with the reverse shock of the …
I present a review of X-ray observations of supernova remnants with an emphasis on shell-type remnants. The topics discussed are the observation of fresh nucleosynthesis products, shock heating and cosmic ray acceleration.
The evolution of type Ia supernova binary system progenitors is highly uncertain. Several evolutionary models predict that the accretion of mass onto the white dwarf is accompanied by mass ejection from the binary in the form of a powerful wind, but very few observations have been made during the initial phase of formation of supernovae remnants, when the interaction of supernova ejecta with presupernova wind could be tested. Here we present hydrodynamical simulations of supernova ejecta interaction with an ambient medium modified by presupernova wind. The structure of the ambient medium when …
The particle acceleration process at a shock wave, in the presence of the second-order Fermi acceleration in the turbulent medium near the shock, is discussed as an alternative explanation for the observed flat synchrotron spectra of supernova remnants (SNRs) in molecular clouds. We argue that medium Alfvén Mach number shocks considered by Chevalier (1999, ApJ, in press) for such SNRs can naturally lead to the observed spectral indices.
Hydrodynamical simulations are presented of a pulsar wind emitted by a supersonically moving pulsar. The pulsar moves through the interstellar medium or, in the more interesting case, through the supernova remnant created at its birth event. In both cases there exists a three-fold structure consisting of the wind termination shock, contact discontinuity and a bow shock bounding the pulsar wind nebula. Using hydrodynamical simulations we study the behaviour of the pulsar wind nebula inside a supernova remnant, and in particular the interaction with the outer shell of swept up interstellar matte…
We present a BIMA image of the supernova remnant G21.5-0.9 at 94 GHz with angular resolution 8.6" x 4.5". On scales larger than our synthesized beam, our results do not indicate any radial or local variations in the acceleration or synchrotron loss processes for the relativistic particles emitting at radio wavelengths. However, the FWHM size of the radio remnant is significantly greater than that of the X-ray remnant. Either any low-frequency spectral break is distributed across the remnant, or more probably the break frequency is in fact higher than ~100 GHz.
(abridged) - We present arcsecond resolution observations from the VLA of the satellite line of the hydroxyl molecule (OH) at 1720.53 MHz toward three Galactic supernova remnants: W28, W44 and IC443. All of our observations are consistent with a model in which the OH(1720 MHz) is collisionally excited by H2 molecules in the postshock gas heated by a non-dissociative shock. Supernova remnants with OH(1720 MHz) maser emission may be promising candidates to conduct high energy searches for the sites of cosmic ray acceleration.
VERITAS observed the supernova remnants Cassiopeia A (Cas A) and IC 443 during 2007, resulting in strong TeV detections of both sources. Cas A is a young remnant, and bright in both the radio and nonthermal X-rays, both tracers of cosmic-ray electrons. IC 443 is a middle-aged composite remnant interacting with a molecular cloud; the molecular cloud provides an enhanced density of target material for hadronic cosmic rays to produce TeV gamma rays via pion decay. The TeV morphology - point-like for Cas A and extended for IC 443 - will be discussed in the context of existing multiwavelength data …
We present a large number of two and a half dimensional simulations of supernova remnants expanding into interstellar media having a range of densities, temperatures and magnetic field strengths. The volume of hot gas produced is strongly dependent on the inclusion of thermal conduction and magnetic fields. The four-volumes and three-areas of hot gas have been catalogued and their dependence on interstellar parameters documented. Simulated line widths of radioactive species ejected by supernovae have also been catalogued.
On the basis of the current observational evidence, we put forward the case that the merger of two CO white dwarfs produces both a Type Ia supernova explosion and a stellar remnant, the latter in the form of a magnetar. The estimated occurrence rates raise the possibility that many, if not most, SNe Ia might result from white dwarf mergers.
This paper discusses several aspects of current research on high energy emission from supernova remnants, covering the following main topics: 1) The recent evidence for magnetic field amplification near supernova remnant shocks, which makes that cosmic rays are more efficiently accelerated than previously thought. 2) The evidence that ions and electrons in some remnants have very different temperatures, and only equilibrate through Coulomb interactions. 3) The evidence that the explosion that created Cas A was asymmetric, and seems to have involved a jet/counter jet structure. And finally, 4),…
A multi-wavelength investigation of the candidate supernova remnant G63.7+1.1 and its surrounding interstellar medium is presented. On the basis of radio continuum data we conclude that the object is a filled-center supernova remnant, perhaps in the course of becoming a composite remnant. The morphology of the remnant, along with HI, 12CO and high resolution IRAS data, suggest that G63.7+1.1 is interacting directly with the ISM, and does not lie in a low density region of the ISM. This in turn strongly suggests that the detected nebula is not surrounded by an invisible halo of supernova ejecta…
The Crab Nebula is likely to be expanding into freely expanding supernova ejecta, although the energy in the ejecta may be less than is typical for a Type II supernova. Pulsar nebulae much younger than the Crab have not been found and could have different properties. The search for such nebulae through ultraviolet/optical line emission in core collapse supernovae, or through their X-ray emission (which could show strong absorption) is warranted. Neutron stars have now been found in many young supernova remnants. There is not a clear link between neutron star and remnant type, although there is…
Wide field CCD observations of three, less known, supernova remnants. Filamentary and diffuse emission is discovered from the supernova remnant G67.7+1.8. Emission can also be seen in the ROSAT All Sky Survey data which indicate an extended hard X-ray source. The optical radiation from the G31.5-0.6 area shows weak sulfur emission and is probably not related to the remnant. Weak sulfur emission is also observed from W51C or G49.2-0.7. However, a small patch of emission in the south-east seems to emit strong sulfur emission. Results from long slit spectra are also presented.
We report the discovery of the shocked molecular gas in the supernova remnant HB 21. We derive the physical parameters of the shocked gas from CO J=1-0 and J=2-1 line observations. We discuss the correlation of the shocked molecular gas with the previously detected, shocked atomic gas and the associated infrared emission.
The cosmic-ray spectrum up to the knee ($E\sim 10^{15}$ eV) is attributed to acceleration processes taking place at the blastwaves which bound supernova remnants. Theoretical predictions give a similar estimate for the maximum energy which can be reached at supernova remnant shocks by particle acceleration. Electrons with energies of the order $\sim 10^{15}$ eV should give a nonthermal X-ray component in young supernova remnants. Recent observations of SN1006 and G347.3-0.5 confirm this prediction. We present a method which uses hydrodynamical simulations to describe the evolution of a young r…
It might be thought that supernova remnants (SNRs) more distant than a few kiloparsec from Earth could not have been detected by the EGRET experiment. This work analyzes the observational status of this statement in the light of new CO studies of SNRs.
This paper describes the X-ray emission from supernova remnants evolving in warm, low density, nonthermal pressure dominated regions. Non-equilibrium ionization hydrocode simulations are used to predict the high resolution spectra, ROSAT PSPC countrates, spatial appearance, color temperatures, and the O VII and O VIII emission line fluxes as a function of time. For comparisons with observations, this paper also applies the standard observational analyses for determining the color temperature, electron density, and thermal pressure to ROSAT ``observations'' of one of the simulated remnants, thu…
Most of the proposed associations between magnetars and supernova remnant suffer from age problems. Usually, supernova remnants ages are determined from an approximation of the Sedov-Taylor phase relation between radius and age, for a fixed energy of the explosion ~ 10^{51} erg. Those ages do not generally agree with the characteristic ages of the (proposed) associated magnetars. We show quantitatively that, by taking into account the energy injected on the supernova remnant by magnetar spin-down, a faster expansion results, improving matches between characteristic ages and supernova remnants …
We present the first results from an ongoing work aimed to use supernovae remnants to discriminate among different type Ia supernovae explosion models. We have computed the hydrodynamic interaction of supernova ejecta with the interstellar medium, obtaining the evolution of the density, temperature and ionization structure of the remnant. We have used ejecta profiles obtained from 1D hydrodynamic calculations of the different explosion mechanisms that are currently under debate. We have analyzed the best indicators that allow to discriminate among the different explosion mechanisms, taking int…
The plerion inside the composite Supernova Remnant G11.2-0.3 appears to be dominated by the magnetic field to an extent unprecedented among well known cases. We discuss its evolution as determined by a central pulsar and the interaction with the surrounding thermal remnant, which in turn interacts with the ambient medium. We find that a plausible scenario exists, where all the observations can be reproduced with rather typical values for the parameters of the system; we also obtain the most likely period for the still undetected pulsar.
We propose a new method to measure the metallicity of Type Ia supernova progenitors using Mn and Cr lines in the X-ray spectra of young supernova remnants. We show that the Mn to Cr mass ratio in Type Ia supernova ejecta is tightly correlated with the initial metallicity of the progenitor, as determined by the neutron excess of the white dwarf material before thermonuclear runaway. We use this correlation, together with the flux of the Cr and Mn Kalpha X-ray lines in the Tycho supernova remnant recently detected by Suzaku (Tamagawa et al. 2008) to derive a metallicity of log(Z) = -1.32 (+0.67,…
