Unbeamed tidal disruption events at hard X-rays

Owing to their thermal emission, tidal disruption events (TDEs) were regularly detected in the soft X-rays and sometimes in the optical. Only a few TDEs have been detected at hard X-rays: two are high redshift beamed events, one of which occurred at the core of a nearby galaxy, and the most recent one is of a different nature, involving a compact object in the Milky Way. The aims of this work are to obtain a first sample of hard X-ray-selected unbeamed TDEs, to determine their frequency and to probe whether TDEs usually or exceptionally emit at hard X-ray energies. We performed extensive searches for hard X-ray flares at positions in over 53000 galaxies, up to a distance of 100 Mpc in the Swift BAT archive. Light curves were extracted and parametrized. The quiescent hard X-ray emission was used to exclude persistently active galactic nuclei. Significant flares from non-active galaxies were derived and checked for possible contamination. We found a sample of nine TDE candidates, which translates into a rate of $2 \times 10^{-5}\,{\rm galaxy}^{-1}\,{\rm yr}^{-1}$ above the BAT detection limit. This rate is consistent with those observed by XMM-Newton at soft X-rays and in the optical from SDSS observations, and is as expected from simulations. We conclude that hard X-ray emission should be ubiquitous in un-beamed TDEs and that electrons should be accelerated in their accretion flow.Comment: accepted for publication in A&A; 14 pages, 6 figures, 2 table

Cr/Fe ratio by XPS spectra of magnetoelectropolished AISI 316L SS fitted by Gaussian-Lorentzian shape lines

U radu su predstavljene analize XPS spektara željeza Fe2p3/2 i kroma Cr2p3/2 podešavanjem pomoću simetričnih i asimetričnih oblika linija. Izračuni su provedeni na AISI 316L SS biomaterijalu nakon postupka magnetoelektropoliranja MEP. Najbolji rezultati su postignuti za podešavanje pomoću oblika linija GL(30) i LA(1,3; 4; 5) plus GL(40). Ustanovljeno je da se nakon postupka magnetoelektropoliranja MEP omjer kroma i željeza povećao od 16,4 do 22,4 puta u odnosu na onaj u rasutom materijalu.In the paper, the analyses of Fe2p3/2 and chromium Cr2p3/2 XPS spectra with fitting by symmetrical and asymmetrical line shapes, are presented. The calculations are performed on AISI 316L SS biomaterial after magnetoelectropolishing MEP operation. The best results were obtained for fitting by GL(30) and by LA(1,3; 4; 5) plus GL(40) line shapes. It was found, the chromium-to-iron ratio after magnetoelectropolishing MEP was increasing in the range from 16,4 to 22,4 times versus that one of bulk material

On the Intermediate Line Region in AGNs

In this paper we explore the intermediate line region (ILR) by using the photoionisation simulations of the gas clouds present at different radial distances from the center, corresponding to the locations from BLR out to NLR in four types of AGNs. We let for the presence of dust whenever conditions allow for dust existence. All spectral shapes are taken from the recent multi-wavelength campaigns. The cloud density decreases with distance as a power law. We found that the slope of the power law density profile does not affect the line emissivity radial profiles of major emission lines: H${\beta}$, He~II, Mg~II, C~III] ~and [O~III]. When the density of the cloud at the sublimation radius is as high as 10$^{11.5}$ cm$^{-3}$, the ILR should clearly be seen in the observations independently of the shape of the illuminating radiation. Moreover, our result is valid for low ionization nuclear emission regions of active galaxies.Comment: 8 pages, 2 figures, Accepted for publication in the Journal Frontiers in Astronomy and Space Science

Comparative SEM and EDX analysis of surface coatings created on niobium and titanium alloys after plasma electrolytic oxidation (PEO)

U radu su opisani rezultati SEM i EDS analize površinskih slojeva nastalih na legurama niobija i titanija (TNZ, NiTi, Ti6Al4V) nakon plazma elektrolitičke oksidacije (PEO), poznate i kao mikro lučna oksidacija (Micro Arc Oxidation - MAO). Za eksperiment PEO postupka upotrebljen je nekonvencionalni elektrolit, temeljen na koncentriranoj ortofosfornoj kiselini. Nakon PEO dobiveni su i proučavani bakrom obogaćeni površinski slojevi na biomaterijalu. Prikazane su i statistički obrađene opće značajke površine u odnosu na kovinske biomaterijale nakon PEO postupka, uz značajne razlike u rezultatima.In the paper, the SEM and EDS study results of the surface coatings formed on the niobium and titanium alloys (TNZ, NiTi, Ti6Al4V) after the Plasma Electrolytic Oxidation (PEO), also known as Micro Arc Oxidation (MAO), are described. For the experiment of the PEO treatment, a non-conventional electrolyte, based on the concentrated orthophosphoric acid, was used. Copper-enriched surface coatings on the biomaterials after the PEO were obtained and studied. General surface characteristics, regarding the metallic biomaterials after the PEO treatment, with the significant differences of the results, have been displayed and statistically developed

Long-term optical spectroscopic variations in blazar 3C 454.3

Characterisation of the long-term variations in the broad line region in a luminous blazar, where Comptonisation of broad-line emission within a relativistic jet is the standard scenario for production of gamma-ray emission that dominates the spectral energy distribution. We analysed ten years of optical spectroscopic data from the Steward Observatory for the blazar 3C 454.3, as well as gamma-ray data from the Fermi Large Area Telescope (LAT). The optical spectra are dominated by a highly variable non-thermal synchrotron continuum with a prominent Mg II broad emission line. The line flux was obtained by spectral decomposition including significant contribution from the Fe II pseudo-continuum. Three methods were used to characterise variations in the line flux: (1) stacking of the continuum-subtracted spectra, (2) subtracting the running mean light curves calculated for different timescales, and (3) evaluating potential time delays via the discrete correlation function (DCF). Despite very large variations in the gamma-ray and optical continua, the line flux changes only moderately (< 0.1 dex). The data suggest that the line flux responds to a dramatic change in the blazar activity from a very high state in 2010 to a deep low state in 2012. Two interpretations are possible: either the line flux is anti-correlated with the continuum or the increase in the line luminosity is delayed by ~600 days. If this time delay results from the reverberation of poorly constrained accretion disc emission in both the broad-line region (BLR) and the synchrotron emitting blazar zone within a relativistic jet, we would obtain natural estimates for the BLR radius [R_{BLR,MgII} >~ 0.28 pc] and for the supermassive black hole mass [M_SMBH ~ 8.5x10^8 M_sun]. We did not identify additional examples of short-term 'flares' of the line flux, in addition to the previously reported case observed in 2010.Comment: 8 pages, 7 figures, published in A&A, replaced to match the titl

Development of porous coatings enriched with magnesium and zinc obtained by DC plasma electrolytic oxidation

Coatings with developed surface stereometry, being based on a porous system, may be obtained by plasma electrolytic oxidation, PEO (micro arc oxidation, MAO). In this paper, we present novel porous coatings, which may be used, e.g., in micromachine's biocompatible sensors' housing, obtained in electrolytes containing magnesium nitrate hexahydrate Mg(NO3)(2)center dot 6H(2)O and/or zinc nitrate hexahydrate Zn(NO3)(2)center dot 6H(2)O in concentrated phosphoric acid H3PO4 (85% w/w). Complementary techniques are used for coatings' surface characterization, such as scanning electron microscopy (SEM), for surface imaging as well as for chemical semi-quantitative analysis via energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), glow discharge optical emission spectroscopy (GDOES), and X-ray powder diffraction (XRD). The results have shown that increasing contents of salts (here, 250 g/L Mg(NO3)(2)center dot 6H(2)O and 250 g/L Zn(NO3)(2)center dot 6H(2)O) in electrolyte result in increasing of Mg/P and Zn/P ratios, as well as coating thickness. It was also found that by increasing the PEO voltage, the Zn/P and Mg/P ratios increase as well. In addition, the analysis of XPS spectra revealed the existence in 10 nm top of coating magnesium (Mg2+), zinc (Zn2+), titanium (Ti4+), and phosphorus compounds (PO43-, or HPO42-, or H2PO4-, or P2O74-).Web of Science97art. no. 33

ANSYS analysis of stress and strain after cones plastic deformation

The paper deals with study of stress and strain after cones plastic deformation by ANSYS software. There are shown the new results of FEM analysis, what is the base for the further experimental studies.Web of Science22250850