We construct the most complete sample of supernova remnants (SNRs) in any galaxy -the Large Magellanic Cloud (LMC) SNR sample. We study their various properties such as spectral index (α), size and surface-brightness. We suggest an association between the spatial distribution, environment density of LMC SNRs and their tendency to be located around supergiant shells. We find evidence that the 16 known type Ia LMC SNRs are expanding in a lower density environment compared to the Core-Collapse (CC) type. The mean diameter of our entire population (74) is 41 pc, which is comparable to nearby galaxies. We didn't find any correlation between the type of SN explosion, ovality or age. The N (< D) relationship of a = 0.96 implies that the randomised diameters are readily mimicking such an exponent. The rate of SNe occurring in the LMC is estimated to be ∼1 per 200 yr. The mean α of the entire LMC SNR population is α=-0.52, which is typical of most SNRs. However, our estimates show a clear flattening of the synchrotron α as the remnants age. As predicted, our CC SNRs sample are significantly brighter radio emitters than the type Ia remnants. We also estimate the Σ − D relation for the LMC to have a slope ∼3.8 which is comparable with other nearby galaxies. We also find the residency time of electrons in the galaxy

Determination of the magnetic field strength in the interstellar medium is one of the most complex tasks of contemporary astrophysics. We can only estimate the order of magnitude of the magnetic field strength by using a few very limited methods. Besides Zeeman effect and Faraday rotation, the equipartition or the minimum-energy calculation is a widespread method for estimating magnetic field strength and energy contained in the magnetic field and cosmic ray particles by using only the radio synchrotron emission. Despite of its approximate character, it remains a useful tool, especially when there is no other data about the magnetic field in a source. In this paper we give a modified calculation which we think is more appropriate for estimating magnetic field strengths and energetics in supernova remnants (SNRs). Finally, we present calculated estimates of the magnetic field strengths for all Galactic SNRs for which the necessary observational data are available. The web application for calculation of the magnetic field strength of SNRs is available at

We present the updated empirical radio surface-brightness-to-diameter (? ? D) relation for supernova remnants (SNRs) in our Galaxy. Our original calibration sample of Galactic SNRs with independently determined distances (Pavlovic et al. 2013, hereafter Paper I) is reconsidered and updated with data which became available in the past two years. The orthogonal fitting procedure and probability-density-function-based (PDF) method are applied to the calibration sample in the log? ? logD plane. Non-standard orthogonal regression keeps the ??D and D?? relations invariant within estimated uncertainties. Our previous Monte Carlo simulations verified that the slopes of the empirical ??D relation should be determined by using the orthogonal regression, because of its good performances for data sets with severe scatter. The updated calibration sample contains 65 shell SNRs. 6 new Galactic SNRs are added to the sample from Paper I, one is omitted and distances are changed for 10 SNRs. The slope derived is here slightly steeper (? ? 5.2) than the ??D slope in Paper I (? ? 4.8). The PDF method relies on data points density maps which can provide more reliable calibrations that preserve more information contained in the calibration sample. We estimate distances to five new faint Galactic SNRs discovered for the first time by Canadian Galactic Plane Survey, and obtained distances of 2.3, 4.0, 1.3, 2.9 and 4.7 kiloparsecs for G108.5+11.0, G128.5+2.6, G149.5+3.2, G150.8+3.8 and G160.1?1.1, respectively. The updated empirical relation is used to estimate distances of 160 shell Galactic SNRs and new results change their distance scales up to 15 per cent, compared to the results from Paper I. The PDF calculation can provide even few times higher or lower values in comparison with the orthogonal fit, as it uses a totally different approach. However, on average, this difference is 32, 24 and 18 per cent for mode, median and mean distances. [Projekat Ministarstva nauke Republike Srbije, br. 176005: Emission nebulae: structure and evolution?. B.V. also acknowledges financial support through the Project i br. 176021: Visible and invisible matter in nearby galaxies: theory and observations]

No abstract

In this paper we present new empirical radio surface brightness-to-diameter (Σ − D) relations for supernova remnants (SNRs) in our Galaxy. We also present new theoretical derivations of the Σ − D relation based on equipartition or on constant ratio between cosmic rays and magnetic field energy. A new calibration sample of 60 Galactic SNRs with independently determined distances is created. Instead of (standard) vertical regression, used in previous papers, different fitting procedures are applied to the calibration sample in the log Σ − log D plane. Non-standard regressions are used to satisfy the requirement that values of parameters obtained from the fitting of Σ − D and D − Σ relations should be invariant within estimated uncertainties. We impose symmetry between Σ − D and D − Σ due to the existence of large scatter in both D and Σ. Using four fitting methods which treat Σ and D symmetrically, different Σ − D slopes β are obtained for the calibration sample. Monte Carlo simulations verify that the slopes of the empirical Σ − D relation should be determined by using orthogonal regression, because of its good performance for data sets with severe scatter. The slope derived here (β = 4.8) is significantly steeper than those derived in previous studies. This new slope is closer to the updated theoretically predicted surface brightness-diameter slope in the radio range for the Sedov phase. We also analyze the empirical Σ − D relations for SNRs in the dense environment of molecular clouds and for SNRs evolving in lowerdensity interstellar medium. Applying the new empirical relation to estimate distances of Galactic SNRs results in a dramatically changed distance scale.