Investigation of natural environment by space means. Geobotany, Geomorphology, soil sciences, agricultural lands, landscape study

Reports given by Soviet specialists at a meeting of Socialist countries on remote sensing of the earth using aerospace methods are presented

Q-phonon description of low lying 1^- two-phonon states in spherical nuclei

The properties of 1^-_1 two-phonon states and the characteristics of E1 transition probabilities between low-lying collective states in spherical nuclei are analysed within the Q-phonon approach to the description of collective states. Several relations between observables are obtained. Microscopic calculations of the E1 0^+_1 -> 1^-_1 transition matrix elements are performed on the basis of the RPA. A satisfactory description of the experimental data is obtained.Comment: 16 pages, 2 figures, 9 table

Photovoltage in curved 1D systems

Curvature of quantum wire results in intrasubband absorption of IR radiation that induces stationary photovoltage in presence of circular polarization. This effect is studied in ballistic (collisionless) and kinetic regimes. The consideration is concentrated on quantum wires with curved central part. It is shown, that if mean free path is shorter than length of the curved part the photovoltage does not depend on the wire shape, but on the total angle of rotation of wire tangent. It is not the case when mean free path is finite or large. This situation was studied for three specific shapes of wires: "hard angle", "open book" and "$\Omega$-like".Comment: 12 pages, 1 figur

Stationary drag photocurrent caused by strong running wave in quantum wire: quantization of current

The stationary current induced by a strong running potential wave in one-dimensional system is studied. Such a wave can result from illumination of a straight quantum wire with special grating or spiral quantum wire by circular-polarized light. The wave drags electrons in the direction correlating with the direction of the system symmetry and polarization of light. In a pure system the wave induces minibands in the accompanied system of reference. We study the effect in the presence of impurity scattering. The current is an interplay between the wave drag and impurity braking. It was found that the drag current is quantized when the Fermi level gets into energy gaps

Spectral state dependence of the 0.4-2 MeV polarized emission in Cygnus X-1 seen with INTEGRAL/IBIS, and links with the AMI radio data

Polarization of the >~400 keV hard tail of the microquasar Cygnus X-1 has been independently reported by INTEGRAL/IBIS, and INTEGRAL/SPI and interpreted as emission from a compact jet. These conclusions were, however, based on the accumulation of all INTEGRAL data regardless of the spectral state. We utilize additional INTEGRAL exposure accumulated until December 2012, and include the AMI/Ryle (15 GHz) radio data in our study. We separate the observations into hard, soft, and intermediate/transitional states and detect radio emission from a compact jet in hard and intermediate states, but not in the soft. The 10-400 keV INTEGRAL (JEM-X and IBIS) state resolved spectra are well modeled with thermal Comptonization and reflection components. We detect a hard tail in the 0.4-2 MeV range for the hard state only. We extract the state dependent polarigrams of Cyg X-1, which all are compatible to no or undetectable level of polarization except in 400-2000 keV range in the hard state where the polarization fraction is 75$\pm$32 % and the polarization angle 40.0 +-14 deg. An upper limit on the 0.4-2 MeV soft state polarization fraction is 70%. Due to the short exposure, we obtain no meaningful constraint for the intermediate state. The likely detection of a >400 keV polarized tail in the hard state, together with the simultaneous presence of a radio jet, reinforce the notion of a compact jet origin of the 400 keV emission.Comment: 13 pages, 5 figures, accepted for publication in Ap

Vela X-1 as a laboratory for accretion in High-Mass X-ray Binaries

Vela X-1 is an eclipsing high mass X-ray binary (HMXB) consisting of a 283s accreting X-ray pulsar in a close orbit of 8.964 days around the B0.5Ib supergiant HD77581 at a distance of just 2.4 kpc. The system is considered a prototype of wind-accreting HMXB and it has been used as a baseline in different theoretical or modelling studies. We discuss the observational properties of the system and the use of the observational data as laboratory to test recent developments in modelling the accretion process in High-Mass X-ray Binaries (e.g., Sander et al. 2018; El Mellah et al. 2018), which range from detailed descriptions of the wind acceleration to modelling of the structure of the flow of matter close to the neutron star and its variations.Comment: 4 pages, 2 figures, proceedings of the 12th INTEGRAL conference "INTEGRAL looks AHEAD to Multimessenger astronomy" in Geneva (Switzerland) on 11-15 February 201

Long term variability of Cygnus X-1: VII. Orbital variability of the focussed wind in Cyg X-1 / HDE 226868 system

Binary systems with an accreting compact object are a unique chance to investigate the strong, clumpy, line-driven winds of early type supergiants by using the compact object's X-rays to probe the wind structure. We analyze the two-component wind of HDE 226868, the O9.7Iab giant companion of the black hole Cyg X-1 using 4.77 Ms of RXTE observations of the system taken over the course of 16 years. Absorption changes strongly over the 5.6 d binary orbit, but also shows a large scatter at a given orbital phase, especially at superior conjunction. The orbital variability is most prominent when the black hole is in the hard X-ray state. Our data are poorer for the intermediate and soft state, but show signs for orbital variability of the absorption column in the intermediate state. We quantitatively compare the data in the hard state to a toy model of a focussed Castor-Abbott-Klein-wind: as it does not incorporate clumping, the model does not describe the observations well. A qualitative comparison to a simplified simulation of clumpy winds with spherical clumps shows good agreement in the distribution of the equivalent hydrogen column density for models with a porosity length on the order of the stellar radius at inferior conjunction; we conjecture that the deviations between data and model at superior conjunction could be either due to lack of a focussed wind component in the model or a more complicated clump structure.Comment: proposed for acceptance in A&A, 11 pages, 11 figures (two in appendix

Radiography in high mass X-ray binaries -- Micro-structure of the stellar wind through variability of the column density

In high mass X-ray binaries (HMXBs), an accreting compact object orbits a high mass star which loses mass through a dense and inhomogeneous wind. Using the compact object as an X-ray backlight, the time variability of the absorbing column density in the wind can be exploited in order to shed light on the micro-structure of the wind and obtain unbiased stellar mass loss rates for high mass stars. We explore the impact of clumpiness on the variability of the column density with a simplified wind model. In particular, we focus on the standard deviation of the column density and the characteristic duration of enhanced absorption episodes, and compare them with analytical predictions based on the porosity length. We identified the favorable systems and orbital phases to determine the wind micro-structure. The coherence time scale of the column density is shown to be the self-crossing time of a clump in front of the compact object. We provide a recipe to get accurate measurements of the size and of the mass of the clumps, purely based on the observable time variability of the column density. The coherence time scale grants direct access to the size of the clumps while their mass can be deduced separately from the amplitude of the variability. If it is due to unaccreted passing-by clumps, the high column density variations in some HMXBs requires high mass clumps to reproduce the observed peak-to-peak amplitude and coherence time scales. These clump properties are hardly compatible with the ones derived from first principles. Alternatively, other components could contribute to the variability of the column density: larger orbital scale structures produced by a mechanism still to be identified, or a dense environment in the immediate vicinity of the accretor such as an accretion disk, an outflow or a spherical shell around the magnetosphere of the accreting neutron star

Cross-relaxation and phonon bottleneck effects on magnetization dynamics in LiYF4:Ho3+

Frequency and dc magnetic field dependences of dynamic susceptibility in diluted paramagnets LiYF$_4$:Ho$^{3+}$ have been measured at liquid helium temperatures in the ac and dc magnetic fields parallel to the symmetry axis of a tetragonal crystal lattice. Experimental data are analyzed in the framework of microscopic theory of relaxation rates in the manifold of 24 electron-nuclear sublevels of the lowest non-Kramers doublet and the first excited singlet in the Ho$^{3+}$ ground multiplet $^5I_8$ split by the crystal field of S$_4$ symmetry. The one-phonon transition probabilities were computed using electron-phonon coupling constants calculated in the framework of exchange charge model and were checked by optical piezospectroscopic measurements. The specific features observed in field dependences of the in- and out-of-phase susceptibilities (humps and dips, respectively) at the crossings (anti-crossings) of the electron-nuclear sublevels are well reproduced by simulations when the phonon bottleneck effect and the cross-spin relaxation are taken into account