We present the results of optical (R band) photometric and polarimetric monitoring and Very Long Baseline Array (VLBA) imaging of the blazar S5 0716+714 along with Fermi gamma -ray data during a ...multi-waveband outburst in 2011 October. We analyze total and polarized intensity images of the blazar obtained with the VLBA at 43 GHz during and after the outburst. Monotonic rotation of the linear polarization vector at a rate of > ~50degrees per night coincided with a sharp maximum in gamma -ray and optical flux. At the same time, within the uncertainties, a new superluminal knot appeared with an apparent speed of 21 + or - 2c. The general multi-frequency behavior of the outburst can be explained within the framework of a shock wave propagating along a helical path in the blazar's jet.
Using the template synthesis method, nanowires (NWs) of various types are prepared from pure cobalt, an alloy of cobalt with copper, and layered structures comprised of alternating cobalt layers of ...various thicknesses and copper interlayers. Using the method of nuclear magnetic resonance (NMR) on
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Co nuclei, structural features of the arrays have been investigated. It is established that fcc and hcp Co phases are present in single-component NWs; the addition of copper ions to the electrolyte leads to almost complete disappearance of the hcp Co phase in the NW. Parameters that characterize the structure of interlayer boundaries of layered NWs with different layer thicknesses are determined.
•Pores, fats and bone inclusions were distinguished in sausage meat.•Identification of Ca from bone inclusions from the total calcium content in the sausage samples was performed using ...microCT.•Analysis of bone content and bone mineral density of sausage samples was implemented with SkyScan software.
This study highlights the possibility of computing microtomography application in food engineering. Standard methods for identifying bone inclusions in sausage products were compared to the proposed method of computing microtomography. The disadvantages of chemical and histological analysis in determining the content of mechanically separated meat in sausage are indicated and described. 2D and 3D microtomograms of the studied sausage samples were obtained. Using computing tomography analyzer (CTAn) software, quantitative analysis of sausage microstructure characteristics were produced. Characteristics of bone and cartilage inclusions in experimental samples are determined. At the end of the study, additional parameters of sausage samples were obtained and analyzed that allowed us to conduct complete sausage microstructure engineering. It is concluded that computer microtomography can be used for detailed microstructural analysis of food products to ensure the quality of production or food fraud identification.
The quasar 3C 454.3 is a blazar known for its rapid and violent outbursts seen across the electromagnetic spectrum. Using γ-ray, X-ray, multiband optical, and very-long-baseline interferometric data ...we investigate the nature of two such events that occurred in 2013 and 2014 accompanied by strong variations in optical polarization, including a ∼230° electric vector position angle (EVPA) rotation. Our results suggest that a single disturbance was responsible for both flaring events. We interpret the disturbance as a shock propagating down the jet. Under this interpretation the 2013 flare originated most likely due to changes in the viewing angle caused by perhaps a bent or helical trajectory of the shock upstream of the radio core. The 2014 flare and optical polarization behavior are the result of the shock exiting the 43 GHz radio core, suggesting that shock crossings are one of the possible mechanisms for EVPA rotations.
We present time-resolved broadband observations of the quasar 3C 279 obtained from multi-wavelength campaigns conducted during the first two years of the Fermi Gamma-ray Space Telescope mission. ...While investigating the previously reported gamma -ray/optical flare accompanied by a change in optical polarization, we found that the optical emission appears to be delayed with respect to the gamma -ray emission by about 10 days. X-ray observations reveal a pair of "isolated" flares separated by ~90 days, with only weak gamma -ray/optical counterparts. The spectral structure measured by Spitzer reveals a synchrotron component peaking in the mid-infrared band with a sharp break at the far-infrared band during the gamma -ray flare, while the peak appears in the millimeter (mm)/submillimeter (sub-mm) band in the low state. Selected spectral energy distributions are fitted with leptonic models including Comptonization of external radiation produced in a dusty torus or the broad-line region. Adopting the interpretation of the polarization swing involving propagation of the emitting region along a curved trajectory, we can explain the evolution of the broadband spectra during the gamma -ray flaring event by a shift of its location from ~1 pc to ~4 pc from the central black hole. On the other hand, if the gamma -ray flare is generated instead at sub-pc distance from the central black hole, the far-infrared break can be explained by synchrotron self-absorption. We also model the low spectral state, dominated by the mm/sub-mm peaking synchrotron component, and suggest that the corresponding inverse-Compton component explains the steady X-ray emission.
Parameters of the type-IIP supernova SN 2012aw Nikiforova, A A; Baklanov, P V; Blinnikov, S I ...
Monthly notices of the Royal Astronomical Society,
05/2021, Letnik:
504, Številka:
3
Journal Article
Recenzirano
ABSTRACT
We present the results the photometric observations of the Type IIP supernova SN 2012aw obtained for the time interval from 7 to 371 d after the explosion. Using the previously published ...values of the photospheric velocities, we have computed the hydrodynamic model which simultaneously reproduced the photometry observations and velocity measurements. We found the parameters of the pre-supernova: radius R = 500 R⊙, nickel mass M(56Ni$)\, \sim 0.06\, \rm M_\odot$, pre-supernova mass 25 M⊙, mass of ejected envelope 23.6 M⊙, explosion energy E ∼ 2 × 1051 erg. The model progenitor mass M = 25 M⊙ significantly exceeds the upper limit mass M = 17 M⊙, obtained from analysis the pre-SNe observations. This result confirms once more that the ’Red Supergiant Problem’ must be resolved by stellar evolution and supernova explosion theories in interaction with observations.
Context. Blazar AO 0235+164 , located at a redshift of z = 0.94, has undergone several sharp multi-spectral-range flaring episodes over recent decades. In particular, the episodes that peaked in 2008 ...and 2015, which were subject to extensive multi-wavelength coverage, exhibited an interesting behavior. Aims. We study the actual origin of these two observed flares by constraining the properties of the observed photo-polarimetric variability as well as of the broadband spectral energy distribution and the observed time-evolution behavior of the source. We use ultra-high-resolution total-flux and polarimetric very-long-baseline interferometry (VLBI) imaging. Methods. The analysis of VLBI images allowed us to constrain kinematic and geometrical parameters of the 7 mm jet. We used the discrete correlation function to compute the statistical correlation and the delays between emission at different spectral ranges. The multi-epoch modeling of the spectral energy distributions allowed us to propose specific models of the emission; in particular, with the aim to model the unusual spectral features observed in this source in the X-ray region of the spectrum during strong multi spectral-range flares. Results. We find that these X-ray spectral features can be explained by an emission component originating in a separate particle distribution than the one responsible for the two standard blazar bumps. This is in agreement with the results of our correlation analysis, where we did not find a strong correlation between the X-ray and the remaining spectral ranges. We find that both external Compton-dominated and synchrotron self-Compton-dominated models are able to explain the observed spectral energy distributions. However, the synchrotron self-Compton models are strongly favored by the delays and geometrical parameters inferred from the observations.
We present the results of optical (R-band) photometric and polarimetric monitoring and Very Long Baseline Array imaging of the blazar S4 0954+658, along with Fermi gamma -ray data during a ...multi-waveband outburst in 2011 March-April. After a faint state with a brightness level R ~ 17.6 mag registered in the first half of 2011 January, the optical brightness of the source started to rise and reached ~14.8 mag during the middle of March, showing flare-like behavior. The most spectacular case of intranight variability was observed during the night of 2011 March 9, when the blazar brightened by ~0.7 mag within 7 hr. During the rise of the flux, the position angle of the optical polarization rotated smoothly over more than 300degrees. At the same time, within 1sigma uncertainty, a new superluminal knot appeared with an apparent speed of 19.0+ or -0.3c. We have very strong evidence that this knot is associated with the multi-waveband outburst in 2011 March-April. We also analyze the multi-frequency behavior of S4 0954+658 during a number of minor outbursts from 2008 August to 2012 April. We find some evidence of connections between at least two additional superluminal ejecta and near-simultaneous optical flares.
Nanowires of different types (homogeneous (made of iron) and heterogeneous (layered)), obtained by the template synthesis method, have been investigated. A technique for preparation of layered ...nanowire arrays with alternating thin layers of magnetic and nonmagnetic metals (Co/Cu and Ni/Cu) has been developed and described. Microscopy methods (SEM and TEM with elemental analysis) are used to study topography of the obtained structures, nanowire diameters, individual-layer thicknesses, and specific features of layer interfaces. Several ways of synthesis of nanowires with thin layers and sharp interfaces are proposed: dilution of electrolyte, use of a reference electrode, and monitoring of the charge passage. Layered nanowires are investigated by magnetometry; it is shown that the magnetic properties of a layered nanowire array (in particular, direction of the easy magnetization axis in the Co/Cu nanowire array) depend not only on the aspect ratio of the magnetic layer but also on the thickness ratio between the magnetic-metal layer and the nonmagnetic spacer (copper interlayer). Nanowires of the two types are studied using the nuclear magnetic resonance (NMR) method. Layered Co/Cu structures are analyzed by
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Co NMR: it is shown that nanowires with smaller-thickness layers (and, accordingly, with a larger contribution from the interfaces) are characterized by a larger fraction of Co atoms coordinated by Cu atoms. The large fraction of the Cu-coordinated atoms suggests that copper impurity enters cobalt layers. Homogeneous nanowires made of iron are compared with bulk iron samples (
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Fe NMR). The line is found to be shifted to higher frequencies (by 0.3 MHz), which is indicative of an increase in the field by about 0.2 T. A significant line broadening and a decrease in the spin–lattice relaxation time may indicate that there is a large dispersion between the local magnetic field values.
Abstract
In 2015 July 29–September 1, the satellite XMM–Newton pointed at the BL Lac object PG 1553+133 six times, collecting data for 218 h. During one of these epochs, simultaneous observations by ...the Swift satellite were requested to compare the results of the X-ray and optical–UV instruments. Optical, near-infrared and radio monitoring was carried out by the Whole Earth Blazar Telescope (WEBT) collaboration for the whole observing season. We here present the results of the analysis of all these data, together with an investigation of the source photometric and polarimetric behaviour over the last 3 yr. The 2015 EPIC spectra show slight curvature and the corresponding light curves display fast X-ray variability with a time-scale of the order of 1 h. In contrast to previous results, during the brightest X-ray states detected in 2015 the simple log-parabolic model that best fits the XMM–Newton data also reproduces reasonably well the whole synchrotron bump, suggesting a peak in the near-UV band. We found evidence of a wide rotation of the polarization angle in 2014, when the polarization degree was variable, but the flux remained almost constant. This is difficult to interpret with deterministic jet emission models, while it can be easily reproduced by assuming some turbulence of the magnetic field.
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