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Register a new userTheoretical Derivation of $Sigma$-$D$ Relation of Galactic SNRs
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We derive the $Sigma$-$D$ relation of Galactic supernova remnants of shell-type separately at adiabatic-phase and at radiative-phase through two sets of different formulas, considering the different physical processes of shell-type remnants at both stages. Also statistics on Galactic shell-type remnants about 57 was made. Then we do some comparison with other results obtained before. It shows that all the best fit lines in the $Sigma$-$D$ relation plots newly are to some extent flatter than those derived by some authors at early time. Our theoretical and statistical outcomes are in somewhat good consistency.
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Relations between radio surface brightness ($Sigma$) and diameter ($D$) of supernova remnants (SNRs) are important in astronomy. In this paper, following the work Duric & Seaquist (1986) at adiabatic phase, we carefully investigate shell-type supernova remnants at radiative phase, and obtain theoretical $Sigma$-$D$ relation at radiative phase of shell-type supernova remnants at 1 GHz. By using these theoretical $Sigma$-$D$ relations at adiabatic phase and radiative phase, we also roughly determine phases of some supernova remnant from observation data.
During detailed searches for new Galactic supernova remnants (SNRs) in the Anglo Australian Observatory/United Kingdom Schmidt Telescope (AAO/UKST) HAlpha survey of the southern Galactic plane, we also uncovered, for the first time, possible associated HAlpha emission in the vicinity of about 24 known Galactic SNRs previously known solely from radio or X-ray observations.The possible optical counterparts to these known SNR were detected due to the 1 arcsecond resolution and 5 Rayleigh sensitivity of this HAlpha survey. The newly discovered emission frequently exhibits the typical filamentary form of other optically detected SNRs although sometimes the HAlpha emission clouds or fragmented filaments largely inside an SNR extend over the radio border. It is true that superposition of general diffuse and extended Galactic emission in the region of these remnants is a complicating factor, but for many optical candidates the HAlpha emission provides an excellent morphological and positional match to the observed radio emission so that an association seems clear. We have already published HAlpha images and confirmatory spectral observations for several of the best optical counterparts to known SNRs but for completeness and convenience we include them in our complete catalogue of previously known radio detected SNRs for which we have now uncovered HAlpha optical emission. For better visualisation of the optical emissions from these faint supernova remnants and to enhance some low surface-brightness features we also present quotient images of the HAlpha data divided by the accompanying broad-band short red (SR) data. Out of 274 Galactic SNRs currently catalogued and detected in the radio only ~20 had previous optical counterparts. We may have now increased this by a further third by adding a further 24 candidate optical counterparts.
An analysis of the relation between radio surface brightness and diameter, so-called Sigma-D relation, for planetary nebulae (PNe) is presented: i) the theoretical Sigma-D relation for the evolution of bremsstrahlung surface brightness is derived; ii) contrary to the results obtained earlier for the Galactic supernova remnant (SNR) samples, our results show that the updated sample of Galactic PNe does not severely suffer from volume selection effect - Malmquist bias (same as for the extragalactic SNR samples) and; iii) we conclude that the empirical Sigma-D relation for PNe derived in this paper is not useful for valid determination of distances for all observed PNe with unknown distances.
We present a new model for the spectral evolution of Pulsar Wind Nebulae inside Supernova Remnants. The model couples the long-term dynamics of these systems, as derived in the 1-D approximation, with a 1-zone description of the spectral evolution of the emitting plasma. Our goal is to provide a simplified theoretical description that can be used as a tool to put constraints on unknown properties of PWN-SNR systems: a piece of work that is preliminary to any more accurate and sophisticated modeling. In the present paper we apply the newly developed model to a few objects of different ages and luminosities. We find that an injection spectrum in the form of a broken-power law gives a satisfactory description of the emission for all the systems we consider. More surprisingly, we also find that the intrinsic spectral break turns out to be at a similar energy for all sources, in spite of the differences mentioned above. We discuss the implications of our findings on the workings of pulsar magnetospheres, pair multiplicity and on the particle acceleration mechanism(s) that might be at work at the pulsar wind termination shock.
Shock acceleration by the shells of supernova remnants (SNRs) has been hypothesized to be the mechanism that produces the bulk of Galactic Cosmic Rays, possibly up to PeV energies. Some SNRs have been shown to accelerate cosmic rays to TeV energies and above. But which SNRs are indeed efficient accelerators of protons and nuclei? And what is the maximum energy up to which they can efficiently accelerate particles? Measurements of non-thermal emission, especially in the gamma-ray regime, are essential to answer these questions. The High-Altitude Water Cherenkov (HAWC) observatory, surveying the northern TeV gamma-ray sky, is currently the most sensitive wide field-of-view survey instrument in the VHE (very-high-energy, >100 GeV) range and has recorded more than five years of data. The Large Area Telescope (LAT) onboard the Fermi satellite has been surveying the GeV gamma-ray sky for more than ten years. Combining measurements from both instruments allows the study of gamma-ray emission from SNRs over many orders of magnitude in energy. In this presentation, I will show measurements of VHE gamma-ray emission from Fermi-LAT-detected SNRs with the HAWC Observatory.
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