Discovery of a Planar Waveguide for an X-Ray Radiation

A simple model of X-Ray standing waves (XSW) formation in the slit of a planar waveguide of X-Ray radiation beam for the angle area restricted by the critical total reflection angle is developed. It is shown that the model is true for a case of the Bragg reflection. The conditions required for XSW to appear in the space between two polished parallel plane plates are formulated and a slit size interval conforming to these conditions is evaluated. A mechanism of a XSW intensity decrease in a planar waveguide is proposed. This mechanism explains a high efficiency of slitless collimator application for the transportation of narrow X-Ray beams. Some recommendations on the application of the planar X-Ray waveguide in X-Ray structural and spectral studies of surface are presented.Comment: 15 pages, 2 figures, 1 tabl

Riemannian Spin(7) holonomy manifold carries octonionic-Kahler structure

We prove that Riemannian $Spin(7)$ holonomy manifolds carry octonionic-K\"{a}hler structure.Comment: 5 page

Symplectic analog of Calabi's conjecture for Calabi--Yau threefolds

In this paper we state an analog of Calabi's conjecture proved by Yau. The difference with the classical case is that we propose deformation of the complex structure, whereas the complex Monge--Amp\`{e}re equation describes deformation of the K\"{a}hler (symplectic) structure.Comment: 4 pages. This is a revised version of "Mirror Kaehler potential on Calabi-Yau threefolds" arXiv:1110.473

Metallicity and ionization state of the gas in polar-ring galaxies

The ionization state and oxygen abundance distribution in a sample of polar-ring galaxies (PRGs) were studied from the long-slit spectroscopic observations carried out with the SCORPIO-2 focal reducer at the Russian 6-m telescope. The sample consists of 15 PRGs classified as `the best candidates' in the SDSS-based Polar Ring Catalogue. The distributions of line-of-sight velocities of stellar and gaseous components have given kinematic confirmation of polar structures in 13 galaxies in the sample. We show that ionization by young stars dominates in the external parts of polar discs, while shocks have a significant contribution to gas excitation in the inner parts of polar structures. This picture was predicted earlier in a toy model implying the collision between gaseous clouds on polar orbits with the stellar disc gravitational potential well. The exception is a moderately inclined ring to the host galaxy NGC 5014: the accreted gas in the centre has already settled on the main plane and ionized by young stars, while the gas in the internal part of the ring is excited by shocks. The present study three times increases the number of polar structures with an available oxygen abundance estimation. The measured values of the gas metallicity almost do not depend on the galaxy luminosity. The radial [O/H] gradient in the considered polar rings is shallow or absent. No metal-poor gas was detected. We ruled out the scenario of the formation of polar rings due to cold accretion from cosmic filaments for the considered sample of PRGs.Comment: 13 pages, accepted for publication in MNRA

Search for gas accretion imprints in voids: I. Sample selection and results for NGC 428

We present the first results of a project aimed at searching for gas accretion events and interactions between late-type galaxies in the void environment. The project is based on long-slit spectroscopic and scanning Fabry-Perot interferometer observations performed with the SCORPIO and SCORPIO-2 multimode instruments at the Russian 6-m telescope, as well as archival multiwavelength photometric data. In the first paper of the series we describe the project and present a sample of 18 void galaxies with oxygen abundances that fall below the reference `metallicity-luminosity' relation, or with possible signs of recent external accretion in their optical morphology. To demonstrate our approach, we considered the brightest sample galaxy NGC 428, a late-type barred spiral with several morphological peculiarities. We analysed the radial metallicity distribution, the ionized gas line-of-sight velocity and velocity dispersion maps together with WISE and SDSS images. Despite its very perturbed morphology, the velocity field of ionized gas in NGC 428 is well described by pure circular rotation in a thin flat disc with streaming motions in the central bar. We also found some local non-circular gas motions clearly related to stellar feedback processes. At the same time, we revealed a circumnuclear inclined disc in NGC 428 and a region with significant residual velocities that could be considered as a result of a recent (<0.5 Gyr) accretion event. The observed oxygen abundance gradient does not contradict this conclusion.Comment: Accepted for publication in MNRAS; 13 pages, 10 figures, 4 table

Photospheric magnetic field variations accompanying the 2011 June 7 eruptive event

From vector measurements of the photospheric magnetic field with the SDO/HMI instrument, we studied the field variations within the 2011 June 7 eruptive event related to the filament eruption (FE), flare, and coronal mass ejection (CME). We analyzed the variations in modulus (B), in radial (Br) and transversal (Bt) magnetic induction components, as well as in the field line inclination angle ({\alpha}) to the radial direction from the Sun center were. The conclusion is that the most probable cause for the FE onset being the trigger related to the flares and CME, as well as for Stage 1 of the filament dramatic acceleration, is {\guillemotleft}magnetic flux cancellation{\guillemotright} in several sites inside and around the filament channel. We assumed that the flare and the stage of the filament fastest acceleration are related to a spot emergence near the south-eastern filament footpoint, in which the field polarity and value satisfy a possibility of this field magnetic reconnection with the field surrounding the filament. We studied in detail the time variations in the field line inclination angles within different sites of the eruptive event. During the filament slow emergence, a decrease in the field line inclination angles was revealed to occur in its channel neighboring, whereas the field line inclination angles dramatically grew in the neutral line neighboring within the flare region after the flare onset. The flare ribbons at all the stages of their existence are shown to be located under the photosphere sites with the field modulus local maxima and with minima of the field line inclination angles. We show that, near the photospheric magnetic field polarity inversion line (PIL), the azimuth decreases after the flare onset, which means a decrease in the angle \b{eta} between PIL and the magnetic induction vector projection onto the sky plane

Triggered star formation in giant HI supershells: ionized gas

We considered the regions of triggered star formation inside kpc-sized HI supershells in three dwarf galaxies: IC 1613, IC 2574 and Holmberg II. The ionized and neutral gas morphology and kinematics were studied based on our observations with scanning Fabry-Perot interferometer at the SAO RAS 6-m telescope and 21 cm archival data of THINGS and LITTLE THINGS surveys. The qualitative analysis of the observational data performed in order to highlight the two questions: why the star formation occurred very locally in the supershells, and how the ongoing star formation in HI supershells rims influence its evolution? During the investigation we discovered the phenomenon never observed before in galaxies IC 2574 and Holmberg II: we found faint giant (kpc-sized) ionized shells in H-alpha and [SII]6717,6731 lines inside the supergiant HI shells.Comment: Published in proceedings of the conference "Galaxies" (Essentuki, Russia, November 24-28, 2014). 9 pages, 4 figure

Emission spectrum of ionized gas in the Irr galaxy Holmberg II

We study the ionized gas spectrum of star forming regions in the Holmberg II galaxy using the optical long-slit spectroscopic observations made at the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS). We estimate the oxygen, nitrogen, sulphur, neon, and argon abundances in individual HII regions and find the average metallicity in the galaxy to be Z=0.1 or 0.3 Zsun depending on the estimation method employed. We use these observations combined with the results of our earlier studies of the Irr galaxy IC 10 and BCD galaxy VII Zw 403 to compare the currently most popular methods of gas metallicity estimation in order to select among them the techniques that are most reliable for analysing Irr galaxies. To this end, we use the "direct" Te method and six empirical and theoretical methods. The results of our observations mostly confirm the conclusions of Lopez-Sanchez et al. (2012) based on the analysis of systematic deviations of metallicity estimates derived by applying different methods to "model" HII regions.Comment: 17 pages, 8 figures, 4 tables. Landscape tables 2 and 3 are on the last pages. Accepted by MNRA

Current and field stimulated motion of domain wall in narrow permalloy stripe

Of the new types of cryoelectronic devices under development, including phase shifters, giant magnetoresistance switches, diodes, transistors, and memory cells, some are based on hybrid superconductor-normal metal or superconductor-ferromagnet films. Control of these devices is realized by means of pulses of voltage, light, or magnetic field. Spin-polarized current may be used to switch low-temperature devices, as in spin-electronic devices. In the superconducting layer, the current is dissipation less, which would bring large reduction of energy consumption. We demonstrate that mag-netic domain walls in bilayer niobium-permalloy stripes are shifted by electrical current along the stripe even at low tem-perature, with the niobium in the superconducting state. The wall motion in response to current pulses is quite different from that induced by a magnetic field pulses only. The effect could be used to create a new type of sequentially switched serial devices because of very high value of the wall velocity, which excides by many orders of magnitude the velocity of the wall moved with magnetic field pulses.Comment: 5 pages, 6 figure

Memory effects in permalloy-niobium hybrid structures

The kineticts of magnetization reversal of stripe-shaped permalloy-niobium hybrid nanofilms is studied in 6-300 K temperature range by means of magneto-optics visualization technique. The niobium influence on magnetic domain walls type and on magnetic domain structure of permalloy via the interface quality and via the distortion of stray fields is found. The memory effect, which is the superconducting niobium memory about an initial magnetic domain structure of permalloy at cooling below T_c, is found. The memory is razed only by hybrid heating over T_c