Strange Star Heating Events as a Model for Giant Flares of Soft Gamma-ray Repeaters

Two giant flares were observed on 5 March 1979 and 27 August 1998 from the soft gamma-ray repeaters SGR 0526-66 and SGR 1900+14, respectively. The striking similarity between these remarkable bursts strongly implies a common nature. We show that the light curves of the giant bursts may be easily explained in the model where the burst radiation is produced by the bare quark surface of a strange star heated, for example, by impact of a massive comet-like object.Comment: 5 pages, 4 figures, accepted for publication in Phys. Rev. Letter

Dust Formation and He II 4686 emission in the Dense Shell of the Peculiar Type Ib Supernova 2006jc

We present evidence for the formation of dust grains in an unusual Type Ib SN based on late-time spectra of SN 2006jc. The progenitor suffered an LBV-like outburst just 2 yr earlier, and we propose that the dust formation is a consequence of the SN blast wave overtaking that LBV-like shell. The key evidence for dust formation is (a) the appearance of a red/near-IR continuum source fit by 1600 K graphite grains, and (b) fading of the redshifted sides of He I emission lines, yielding progressively more asymmetric blueshifted lines as dust obscures receding material. This provides the strongest case yet for dust formation in any SN Ib/c. Both developments occurred between 51 and 75 d after peak, while other SNe observed to form dust did so after a few hundred days. Geometric considerations indicate that dust formed in the dense swept-up shell between the forward and reverse shocks, and not in the freely expanding SN ejecta. Rapid cooling leading to dust formation may have been aided by extremely high shell densities, as indicated by He I line ratios. The brief epoch of dust formation is accompanied by He II 4686 emission and enhanced X-ray emission. These clues suggest that the unusual dust formation in this object was not due to properties of the SN itself, but instead -- like most peculiarities of SN 2006jc -- was a consequence of the dense environment created by an LBV-like eruption 2 yr before the SN.Comment: ApJ, accepted. added some discussion and 2 figures, better title, conclusions same as previous version. 12 pages, 4 color fig

Influence of random point defects introduced by proton irradiation on critical current density and vortex dynamics of Ba(Fe0.925Co0.075)2As2 single crystals

In this work we analyze the influence of random point defects introduced by 3 MeV proton irradiation on the critical current density (Jc) and vortex dynamics of a Ba(Fe0.925Co0.075)2As2 single crystal. The results show that at low temperatures (T) the irradiation produces an enhancement of Jc of up to 2.6 times. However the Jc (T) retention at different magnetic fields (H) in the elastic regime, estimated by the n exponent in Jc vs (1-(T/Tc)2)n, is poorer after the irradiations, due to the thermal softening of the pinning by the random point defects. We found that the elastic to plastic crossover and melting lines are only affected by the reduction of the superconducting critical temperature (Tc); they are exactly the same after rescaling the phase diagram by T/Tc. The pinning mechanisms in the single crystals can be associated with a mixed pinning landscape that produces a modulation in S(H,T) as a consequence of a fishtail or second peak in the magnetization.Fil: Haberkorn, Nestor Fabian. Los Alamos National Laboratory; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Maiorov, B.. Los Alamos National Laboratory; Estados UnidosFil: Usov, I. O.. Los Alamos National Laboratory; Estados UnidosFil: Weigand, M.. Los Alamos National Laboratory; Estados UnidosFil: Hirata, W.. Osaka University; JapónFil: Miyasaka, S.. Osaka University; JapónFil: Tajima, S.. Osaka University; JapónFil: Chikumoto, N.. International Superconductivity Technology Center. Superconductivity Research Laboratory; JapónFil: Tanabe, K.. International Superconductivity Technology Center. Superconductivity Research Laboratory; JapónFil: Civale, Leonardo. Los Alamos National Laboratory; Estados Unido

Photon Splitting Cascades in Gamma-Ray Pulsars and the Spectrum of PSR1509-58

Magnetic photon splitting, a QED process that becomes important only in magnetic fields approaching the quantum critical value, B_cr = 4.41 X 10^13 Gauss, is investigated as a mechanism for attenuation of gamma-rays emitted near the surface of strongly-magnetized pulsars. We model photon splitting attenuation and subsequent splitting cascades in gamma-ray pulsars, including the dipole field and curved spacetime geometry of the neutron star magnetosphere. We focus specifically on PSR1509-58, which has the highest surface magnetic field of all the gamma-ray pulsars (B_0 = 3 X 10^13 Gauss). We find that splitting will not be important for most gamma-ray pulsars, i.e. those with B_0 <~ 0.2 B_cr, but will be important for gamma-ray pulsars having B_0 >~ 0.3 B_cr, where the splitting attenuation lengths and escape energies become comparable to or less than those for pair production. We compute Monte Carlo spectral models for PSR1509-58. We find that photon splitting, or combined splitting and pair production, can explain the unusually low cutoff energy (between 2 and 30 MeV) of PSR1509-58, and that the model cascade spectra, which display strong polarization, are consistent with the observed spectral points and upper limits for polar cap emission at a range of magnetic colatitudes up to ~ 25 degrees.Comment: 39 pages, 14 embedded figures, AASTEX To appear in ApJ, January 20, 199

High-temperature change of the creep rate in YBa 2Cu 3O 7-δ films with different pinning landscapes

Magnetic relaxation measurements in YBa 2Cu 3O 7-δ (YBCO) films at intermediate and high temperatures show that the collective vortex creep based on the elastic motion of the vortex lattice has a crossover to fast creep that significantly reduces the superconducting critical current density (J c). This crossover occurs at temperatures much lower than the irreversibility field line. We study the influence of different kinds of crystalline defects, such as nanorods, twin boundaries, and nanoparticles, on the high-temperature vortex phase diagram of YBCO films. We found that the magnetization relaxation data is a fundamental tool to understand the pinning at high temperatures. The results indicate that high J c values are directly associated with small creep rates. Based on the analysis of the depinning temperature in films with columnar defects, our results indicate that the size of the defects is the relevant parameter that determines thermal depinning at high temperatures. Also, the extension of the collective creep regime depends on the density of the pinning centers.Fil: Haberkorn, Nestor Fabian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Miura, M.. No especifíca;Fil: Baca, J.. No especifíca;Fil: Maiorov, B.. No especifíca;Fil: Usov, I.. No especifíca;Fil: Dowden, P.. No especifíca;Fil: Foltyn, S. R.. No especifíca;Fil: Holesinger, T. G.. No especifíca;Fil: Willis, J. O.. No especifíca;Fil: Marken, K. R.. No especifíca;Fil: Izumi, T.. No especifíca;Fil: Shiohara, Y.. No especifíca;Fil: Civale, L.. No especifíca

Некоторые аспекты использования системного подхода к исследованию объектов судебной экспертизы

The article is devoted to the application of the systematic approach when studying the objects of forensic examination. Based on the theoretical reflection on the problem, as well as on the materials of practice of forensic computer and integrated psychological and linguistic examinations, the authors demonstrate that it is necessary to consider complex objects of analysis as systems. All the elements of such systems are intertwined, aligned, organized and collectively possess properties that are not inherent in any component of their parts. Application of the systematic approach in the production of forensic examinations will help to avoid mistakes resulting in unreliable conclusions.На основе теоретического осмысления проблемы использования системного подхода к исследованию объектов судебной экспертизы, а также на материале практики производства судебных компьютерно-технических и комплексных психолого-лингвистических экспертиз показано, что сложные объекты судебной экспертизы необходимо рассматривать как систему. Все элементы данной системы взаимосвязаны, упорядочены, организованы и в совокупности обладают свойствами, не присущими ни одной из составляющей его частей. Использование системного подхода в производстве судебных экспертиз позволит избежать ошибок, ведущих к недостоверным выводам