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[en] The X-ray emission from a supernova remnant (SNR) is a powerful diagnostic of the state of the shocked plasma. The temperature (kT) and the emission measure (EM) of the shocked gas are related to the energy of the explosion, the age of the SNR, and the density of the surrounding medium. Progress in X-ray observations of SNRs has resulted in a significant sample of Galactic SNRs with measured kT and EM values. We apply spherically symmetric SNR evolution models to a new set of 43 SNRs to estimate ages, explosion energies, and circumstellar medium densities. The distribution of ages yields an SNR birth rate. The energies and densities are well fit with lognormal distributions, with wide dispersions. SNRs with two emission components are used to distinguish between SNR models with uniform interstellar medium and with stellar wind environment. We find Type Ia SNRs to be consistent with a stellar wind environment. Inclusion of stellar wind SNR models has a significant effect on estimated lifetimes and explosion energies of SNRs. This reduces the discrepancy between the estimated SNR birth rate and the SN rate of the Galaxy.
[en] New distances to the supernova remnants (SNRs) G31.9+0.0 and G54.4−0.3 have been found. The analysis method uses H i absorption spectra and CO channel maps. Individual H i channel maps are used to verify absorption features in the H i absorption spectrum or to determine if they have noise. Both of the SNRs are associated with molecular clouds so accurate kinematic velocities are determined. The H iabsorption is used to resolve the kinematic distance ambiguity. The resulting new distance for G31.9+0.0 is 7.1 ± 0.4 kpc and for G54.4−0.3 it is 6.6 ± 0.6 kpc. These are significant revisions to the previous values.
[en] In this paper, we analyze 1420 MHz continuum and H i observations of the supernova remnant (SNR) 3C 397 (G41.1-0.3). The H i absorption spectra show clear absorption up to the tangent point velocity and also the absence of absorption at 50–60 km s"−"1. This yields lower and upper limits to the distances of 6.3 ± 0.1 and 9.7 ± 0.3 kpc, which are better and more robust than previous estimates. We apply generalized SNR models to 3C 397, including the ejecta-dominated phase and the transition-to-Sedov phase. Using emission measures from the X-ray and mean gas density from the infrared, we show that the hard X-ray component has the dominant filling factor and the soft X-ray component has a very small filling factor. The models are required to be consistent with 3C 397's measured properties, including the observed shock temperatures and shock radii. Consistent models are found if 3C 397 has a distance in the range of ≃8–9.7 kpc. For an 8 kpc distance, the estimated age is ≃1350 years and the explosion energy is 1.0 × 10"5"1 erg, while for 9.7 kpc, the the most probable age is ≃1750 years and the energy 1.5 × 10"5"1 erg