Marko Pavlović

MODIFIED EQUIPARTITION CALCULATION FOR SUPERNOVA REMNANTS

Determination of the magnetic field strength in the interstellar medium is one of the more 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 the Zeeman effect and Faraday rotation, the equipartition or 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 its approximate character, it remains a useful tool, especially when there are no other data about the magnetic field in a source. In this paper, we give a modified calculation that we think is more appropriate for estimating magnetic field strengths and energetics in supernova remnants (SNRs). 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 strengths of SNRs is available at http://poincare.matf.bg.ac.rs/~arbo/eqp/.

THE RADIO SURFACE-BRIGHTNESS-TO-DIAMETER RELATION FOR GALACTIC SUPERNOVA REMNANTS: SAMPLE SELECTION AND ROBUST ANALYSIS WITH VARIOUS FITTING OFFSETS

In this paper, we present new empirical radio surface-brightness-to-diameter (?-D) relations for supernova remnants (SNRs) in our Galaxy. We also present new theoretical derivations of the ?-D relation based on equipartition or on a 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 ?-log D plane. Non-standard regressions are used to satisfy the requirement that values of parameters obtained from the fitting of ?-D and D-? relations should be invariant within estimated uncertainties. We impose symmetry between ?-D and D-? due to the existence of large scatter in both D and ?. Using four fitting methods that treat ? and D symmetrically, different ?-D slopes ? are obtained for the calibration sample. Monte Carlo simulations verify that the slopes of the empirical ?-D relation should be determined by using orthogonal regression because of its good performance in data sets with severe scatter. The slope derived here (? = 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 of the Sedov phase. We also analyze the empirical ?-D relations for SNRs in a dense environment of molecular clouds and for SNRs evolving in the lower-density interstellar medium. Applying new empirical relations to estimate distances of Galactic SNRs results in a dramatically changed distance scale.

Modified Equipartition Calculation for Supernova Remnants. Cases α = 0.5 and α = 1

The equipartition or minimum energy calculation is a well-known procedure for estimating the magnetic field strength and the total energy in the magnetic field and cosmic ray particles by using only the radio synchrotron emission. In one of our previous papers, we have offered a modified equipartition calculation for supernova remnants (SNRs) with spectral indices 0.5 < α < 1. Here we extend the analysis to SNRs with α = 0.5 and α = 1.

Headed Shear Studs versus High-Strength Bolts in Prefabricated Composite Decks

Prefabricated steel and concrete composite decks are an interesting option to improve competitiveness and sustainability of the composite structures. Longitudinal shear connection is usually establ ...

Radio Evolution of Supernova Remnants Including Nonlinear Particle Acceleration: Insights from Hydrodynamic Simulations

We present a model for the radio evolution of supernova remnants (SNRs) obtained by using three-dimensional (3D) hydrodynamic simulations, coupled with nonlinear kinetic theory of cosmic ray (CR) acceleration in SNRs. We model the radio evolution of SNRs on a global level, by performing simulations for wide range of the relevant physical parameters, such as the ambient density, the supernova (SN) explosion energy, the acceleration efficiency and the magnetic field amplification (MFA) efficiency. We attribute the observed spread of radio surface brightnesses for corresponding SNR diameters to the spread of these parameters. We did not limit our simulations only to type Ia SNRs, but also considered SNR radio evolution in denser, nonuniform circumstellar environment, modified by the progenitor star wind. These simulations start with the mass of the ejecta substantially higher than in the case of a type Ia SN and presumably lower shock speed. The magnetic field is understandable seen as very important for the radio evolution of SNRs. In terms of magnetic field amplification (MFA), we include both resonant and non-resonant modes in our large scale simulations, by implementing models obtained from the first-principles, particle-in-cell (PIC) simulations and non-linear magnetohydrodynamical (MHD) simulations. We test the quality and reliability of our models on sample consisting of Galactic and extragalactic SNRs. Our simulations give

Industrial Single Board Computer based on OMAP5 processor

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A Multi-Frequency Study of the Milky Way-Like Spiral Galaxy NGC 6744

slopes between -4 and -6 for the full Sedov regime. Recent empirical slopes obtained for the Galactic samples are around -5, while for the entire extragalactic samples are around -4.

Searching for an interstellar medium association for HESS J1534 − 571

This paper presents a detailed hardware architecture of an industrial embedded computer based on the newest OMAP5 processor from Texas Instruments (TI). This processor has specialized hardware blocks for digital signal processing, video acceleration, 3D graphics and others. Device supports rich set of interfaces, covering wide range of required protocols in industrial applications. Wireless support is enabled via special module, which can be inserted in an on-board connector.

Influence of execution tolerances for friction connections in circular and polygonal towers for wind converters

We present a multi-frequency study of the intermediate spiral SAB(r)bc type galaxy NGC 6744, using available data from the Chandra X-Ray telescope, radio continuum data from the Australia Telescope Compact Array and Murchison Widefield Array, and Wide-field Infrared Survey Explorer infrared observations. We identify 117 X-ray sources and 280 radio sources. Of these, we find nine sources in common between the X-ray and radio catalogues, one of which is a faint central black hole with a bolometric radio luminosity similar to the Milky Ways central black hole. We classify 5 objects as supernova remnant candidates, 2 objects as likely supernova remnants, 17 as HII regions, 1 source as an AGN; the remaining 255 radio sources are categorised as background objects and one X-ray source is classified as a foreground star. We find the star-formation rate (SFR) of NGC 6744 to be in the range 2.8 - 4.7

Railway Road Bridge Across the Danube in Novi Sad – Design and Construction

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