arXiv subjects

D. Urosevic

Publications and source records attributed to D. Urosevic.

At least 19 recordsLinked to original sources

arXiv2025

Multi-frequency radio-continuum study of the LMC SNR N206 (Goat's Eye) and its "zig-zag" PWN

We present new radio-continuum observations of the Large Magellanic Cloud (LMC) supernova remnant (SNR) N206, which we give the name "Goat's Eye". Goat's Eye contains an interior radio structure that is likely a pulsar wind nebula (PWN), which we analyse in further detail. We use new radio observations from the Australia Telescope Compact Array (ATCA) telescope, as well as several archival radio observations, to calculate spectral indices, and find a steep spectral index for the whole SNR ($\alpha = -0.60\pm0.02$), and a flatter spectral index for the PWN ($\alpha = -0.16\pm0.03$). We also measure the polarisation and magnetic field properties of the PWN. Previously reported as a linear structure, the new observations show an unusual "zig-zag"-like structure, visible in radio-continuum total intensity, linear polarisation, and magnetic field orientations. The origin of this zig-zag structure is unclear, but we propose some origin scenarios that will require further observations to differentiate between.

astro-ph.HE↗

arXiv2024

Radio Continuum Study of the Large Magellanic Cloud Supernova Remnant Honeycomb Nebula

We present the first and deepest Australia Telescope Compact Array radio continuum images of the Honeycomb Nebula at 2000 and 5500 MHz solely from archival data. The resolutions of these images are 3.6 x 2.8 arcsec2 and 1.3 x 1.2 arcsec2 at 2000 and 5500 MHz. We find an average radio spectral index for the remnant of -0.76 +- 0.07. Polarisation maps at 5500 MHz reveal an average fractional polarisation of 25 +- 5% with a maximum value of 95 x 16. We estimate the equipartition field for Honeycomb Nebula of 48 +- 5 {\mu}G, with an estimated minimum energy of Emin = 3 x 1049 erg. The estimated surface brightness, {\Sigma}1 GHz , is 30 x 10-20 W m-2 Hz-1 sr-1; applying the {\Sigma}-D relation suggests this supernova remnant is expanding into a low-density environment. Finally, using Hi data, we can support the idea that the Honeycomb Nebula exploded inside a low-density wind cavity. We suggest that this remnant is likely to be between late free expansion stage and early Sedov phase of evolution and expanding into a low-density medium.

astro-ph.HE↗

arXiv2021

Determination of Planetary Nebulae angular diameters from radio continuum Spectral Energy Distribution modeling

Powerful new, high resolution, high sensitivity, multi-frequency, wide-field radio surveys such as the Australian Square Kilometre Array Pathfinder (ASKAP) Evolutionary Map of the Universe (EMU) are emerging. They will offer fresh opportunities to undertake new determinations of useful parameters for various kinds of extended astrophysical phenomena. Here, we consider specific application to angular size determinations of Planetary Nebulae (PNe) via a new radio continuum Spectral Energy Distribution (SED) fitting technique. We show that robust determinations of angular size can be obtained, comparable to the best optical and radio observations but with the potential for consistent application across the population. This includes unresolved and/or heavily obscured PNe that are extremely faint or even non-detectable in the optical.

astro-ph.GA↗

arXiv2018

Searching for an interstellar medium association for HESS J1534-571

The Galactic supernova remnant HESS J1534-571 (also known as G323.7-1.0) has a shell-like morphology in TeV gamma-ray emission and is a key object in the study of cosmic ray origin. Little is known about its distance and local environment. We examine Mopra $^{12}$CO/$^{13}$CO(1-0) data, Australian Telescope Compact Array HI, and Parkes HI data towards HESS J1534-571. We trace molecular clouds in at least five velocity ranges, including clumpy interstellar medium structures near a dip in HI emission at a kinematic velocity consistent with the Scutum-Crux arm at ~3.5 kpc. This feature may be a cavity blown-out by the progenitor star, a scenario that suggests HESS J1534-571 resulted from a core-collapse event. By employing parametrisations fitted to a sample of supernova remnants of known distance, we find that the radio continuum brightness of HESS J1534-571 is consistent with the ~3.5 kpc kinematic distance of the Scutum-Crux arm HI dip. Modelling of the supernova evolution suggests an ~8-24 kyr age for HESS J1534-571 at this distance.

astro-ph.HE↗

arXiv2017

Radio Planetary Nebulae in the Large Magellanic Cloud

We present 21 new radio-continuum detections at catalogued planetary nebula (PN) positions in the Large Magellanic Cloud (LMC) using all presently available data from the Australia Telescope Online Archive at 3, 6, 13 and 20 cm. Additionally, 11 previously detected LMC radio PNe are re-examined with $ 7 $ detections confirmed and reported here. An additional three PNe from our previous surveys are also studied. The last of the 11 previous detections is now classified as a compact \HII\ region which makes for a total sample of 31 radio PNe in the LMC. The radio-surface brightness to diameter ($Σ$-D) relation is parametrised as $Σ\propto {D^{ - β}}$. With the available 6~cm $Σ$-$D$ data we construct $Σ$-$D$ samples from 28 LMC PNe and 9 Small Magellanic Cloud (SMC) radio detected PNe. The results of our sampled PNe in the Magellanic Clouds (MCs) are comparable to previous measurements of the Galactic PNe. We obtain $β=2.9\pm0.4$ for the MC PNe compared to $β= 3.1\pm0.4$ for the Galaxy. For a better insight into sample completeness and evolutionary features we reconstruct the $Σ$-$D$ data probability density function (PDF). The PDF analysis implies that PNe are not likely to follow linear evolutionary paths. To estimate the significance of sensitivity selection effects we perform a Monte Carlo sensitivity simulation on the $Σ$-$D$ data. The results suggest that selection effects are significant for values larger than $β\sim 2.6$ and that a measured slope of $β=2.9$ should correspond to a sensitivity-free value of $\sim 3.4$.

astro-ph.GA↗

arXiv2016

A new look at the integrated radio/microwave continuum spectrum of Galactic supernova remnant IC443

Recent observations of the microwave sky, by the space telescopes such as WMAP and Planck, have opened a new window into the analysis of continuum emission from supernova remnants (SNRs). In this paper, different emission models that can explain the characteristic shape of presently known integrated radio/microwave continuum spectrum of the Galactic SNR IC 443 are tested and discussed. In particular, the possibility that the slight bump in the integrated continuum of this remnant around 20 -- 70~GHz is genuine and that can be explained by the contribution of additional emission mechanism such as of spinning dust is emphasized. We find that adding a spinning dust component to the emission model improves the fit of the integrated spectrum of this SNR while, at the same time preserves the physically probable parameter values. Finally, models that include the high-frequency synchrotron bending of the IC 443 radio to microwave continuum are favored.

astro-ph.HE↗

arXiv2014

Optical supernova remnants in nearby galaxies and their influence on star formation rates derived from H$α$ emission

In this paper we present the most up-to-date list of nearby galaxies with optically detected supernova remnants (SNRs). We discuss the contribution of the Hα flux from the SNRs to the total Hα flux and its influence on derived star formation rate (SFR) for 18 galaxies in our sample. We found that the contribution of SNRs' flux to the total Hα flux is 5 $\pm$ 5 per cent. Due to the observational selection effects, the SNRs contamination of SFRs derived herein represents only a lower limit.

astro-ph.GA↗

arXiv2014

On calibration of some distance scales in astrophysics

We present a method for distance calibration without using standard fitting procedures. Instead we use random resampling to reconstruct the probability density function (PDF) of calibration data points in the fitting plane. The resulting PDF is then used to estimate distance-related properties. The method is applied to samples of radio surface brightness to diameter (Σ-D) data for the Galactic supernova remnants (SNRs) and planetary nebulae (PNe), and period-luminosity (PL) data for the Large Magellanic Cloud (LMC) fundamental mode classical Cepheids. We argue that resulting density maps can provide more accurate and more reliable calibrations than those obtained by standard linear fitting procedures. For the selected sample of the Galactic SNRs, the presented PDF method of distance calibration results in a smaller average distance fractional error of up to $\approx 16$ percentage points. Similarly, the fractional error is smaller for up to $\approx 8$ and $\approx 0.5$ percentage points, for the samples of Galactic PNe and LMC Cepheids, respectively. In addition, we provide a PDF-based calibration data for each of the samples.

astro-ph.IM↗

arXiv2014

Radio-continuum study of Large Magellanic Cloud Supernova Remnant J0509-6731

We present a detailed study of Australia Telescope Compact Array (ATCA) observations ($λ$ = 20, 13, 6 & 3~cm) of supernova remnant (SNR) J0509--6731 in the Large Magellanic Cloud (LMC). The remnant has a ring morphology with brightened regions towards the south-western limb. We also find a second brightened inner ring which is only seen in the radio-continuum. The SNR is almost circular, with a diameter ranging from 7 to 8~pc, and a steep radio spectral index between 36 and 3~cm of $α=-0.73\pm0.02$, which is characteristic of younger SNRs. We also report detection of radially orientated polarisation across the remnant at 6~cm, with a mean fractional polarisation level of $P\cong$~(26~$\pm$~13)%. We find the magnetic field ($\sim$168~$μ$G) and $Σ- D$ ($Σ= $ $1.1\times 10^{-19}$~W m$^{-2}$~Hz$^{-1}$~sr$^{-1}$ , $D=$ 7.35~pc) to be consistent with other young remnants.

astro-ph.GA↗

arXiv2013

Optical observations of the nearby galaxy IC342 with narrow band [SII] and H$α$ filters. I

We present observations of the portion of the nearby spiral galaxy IC342 using narrow band [SII] and H$α$ filters. These observations were carried out in November 2011 with the 2m RCC telescope at Rozhen National Astronomical Observatory in Bulgaria. In this paper we report coordinates, diameters, H$α$ and [SII] fluxes for 203 HII regions detected in two fields of view in IC342 galaxy. The number of detected HII regions is 5 times higher than previously known in these two parts of the galaxy.

astro-ph.GA↗

arXiv2013

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 magnetic field strength and 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.

astro-ph.HE↗

arXiv2012

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 (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 lower-density interstellar medium. Applying the new empirical relation to estimate distances of Galactic SNRs results in a dramatically changed distance scale.

astro-ph.GA↗

arXiv2012

Radio confirmation of Galactic supernova remnant G308.3-1.4

We present radio-continuum observations of the Galactic supernova remnant (SNR) candidate, G308.3-1.4, made with the Australia Telescope Compact Array, Molonglo Observatory Synthesis Telescope and the Parkes radio telescope. Our results combined with Chandra X-ray images confirm that G308.3-1.4 is a bona fide SNR with a shell morphology. The SNR has average diameter of D = 34 +- 19 pc, radio spectral index of alpha = -0.68 +- 0.16 and linear polarisation of 10 +- 1%; We estimate the SNR magnetic field B = 29 uG. Employing a Sigma-D relation, we estimate a distance to G308.3-1.4 of d = 19 +- 11 kpc. The radio morphology, although complex, suggests a smaller size for the SNR than previously implied in an X-Ray study. These results imply that G308.3-1.4 is a young to middle-aged SNR in the early adiabatic phase of evolution.

astro-ph.GA↗

arXiv2012

On the existence of "radio thermally active" Galactic supernova remnants

In this paper, we investigate the possibility of significant production of thermal bremsstrahlung radiation at radio continuum frequencies that could be linked to some Galactic supernova remnants (SNRs). The main targets for this investigation are SNRs expanding in high density environments. There are several indicators of radio thermal bremsstrahlung radiation from SNRs, such as a flattening at higher frequencies and thermal absorption at lower frequencies intrinsic to an SNR. In this work we discuss the radio continuum properties of 3 SNRs that are the best candidates for testing our hypothesis of significant thermal emission. In the case of SNRs IC443 and 3C391, thermal absorption has been previously detected. For IC443, the contribution of thermal emission at 1 GHz, from our model fit is 3-57%. It is similar to the estimate obtained from the thermal absorption properties (10-40% at 1 GHz). In the case of the 3C391 the conclusions are not so clear. The results from our model fit (thermal emission contribution of 10-25% at 1 GHz) and results obtained from the low frequency absorption (thermal contribution of 0.15-7% at 1 GHz) do not overlap. For the SNR 3C396 we suggest that if previously detected thermal absorption could be intrinsic to the SNR then the thermal emission (<47% at 1 GHz from our model fit) could be significant enough to shape the radio continuum spectrum at high frequencies. Polarization observations for these SNRs can constrain the strength of a thermal component. Reliable observations at low frequencies (<100 MHz) are needed as well as more data at high radio frequencies (>1 GHz), in order to make stronger conclusions about the existence of "radio thermally active" SNRs.

astro-ph.GA↗

arXiv2011

Observatons of NGC 3077 Galaxy in Narrow Band [SII] and H_alpha Filters

We present observations of the HI tidal arm near dwarf galaxy NGC 3077 (member of the M81 galaxy group) in narrow band [SII] and H_alpha filters. Observations were carried out in March 2011 with the 2m RCC telescope at NAO Rozhen, Bulgaria. Our search for possible supernova remnant candidates (identified as sources with enhanced [SII] emission relative to their H_alpha emission) in this region yielded no sources of this kind. Nevertheless, we found a number of objects with significant H_alpha emission that probably represent uncatalogued, low brightness HII regions.

astro-ph.CO↗

arXiv2011

Modified equipartition calculation for supernova remnants

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 http://poincare.matf.bg.ac.rs/~arbo/eqp/.

astro-ph.HE↗

arXiv2010

The orthogonal fitting procedure for determination of the empirical Σ - D relations for supernova remnants: application to starburst galaxy M82

The radio surface brightness-to-diameter (Σ - D) relation for supernova remnants (SNRs) in the starburst galaxy M82 is analyzed in a statistically more robust manner than in the previous studies that mainly discussed sample quality and related selection effects. The statistics of data fits in log Σ - log D plane are analyzed by using vertical (standard) and orthogonal regressions. As the parameter values of D - Σ and Σ - D fits are invariant within the estimated uncertainties for orthogonal regressions, slopes of the empirical Σ - D relations should be determined by using the orthogonal regression fitting procedure. Thus obtained Σ - D relations for samples which are not under severe influence of the selection effects could be used for estimating SNR distances. Using the orthogonal regression fitting procedure Σ - D slope β \approx 3.9 is obtained for the sample of 31 SNRs in M82. The results of implemented Monte Carlo simulations show that the sensitivity selection effect does not significantly influence the slope of M82 relation. This relation could be used for estimation of distances to SNRs that evolve in denser interstellar environment, with number denisty up to 1000 particles per cm3 .

astro-ph.CO↗

arXiv2009

Optical Observations of M81 Galaxy Group in Narrow Band [SII] and H_alpha Filters: Holmberg IX

We present observations of the nearby tidal dwarf galaxy Holmberg IX in M81 galaxy group in narrow band [SII] and H$α$ filters, carried out in March and November 2008 with the 2m RCC telescope at NAO Rozhen, Bulgaria. Our search for resident supernova remnants (identified as sources with enhanced [SII] emission relative to their H$α$ emission) in this galaxy yielded no sources of this kind, besides M&H 10-11 or HoIX X-1. Nevertheless, we found a number of objects with significant H$α$ emission that probably represent uncatalogued HII regions.

astro-ph.CO↗