Cross-identifications of stars with high proper motions (Version 2.0)

A cross index list of 493 200 stars with proper motions higher than 0.04″/yr (ftp://ftp.mao.kiev.ua/pub/astro/c-ihpms2) was compiled on the basis of the original determinations for the FONAK1.1 catalog stars, the data from the Hipparcos, Tycho-2, UCAC2, CMC (STAR 11), PPM, NPM1, NPM2, XZ80Q, Pul-3, PUL2, GCVS, NLTT, LHS, Lowell Proper Motion, and Bruce Proper Motion catalogs, as well as the data published in other sources.     

Nonresonant effects and hydrogen transition line shape in cosmological recombination problems

Data on the fluctuations in cosmic microwave background (CMB) radiation, whose accuracy is expected to increase in the immediate future, allow the cosmological recombination of atomic hydrogen and its interaction with the CMB radiation to be studied. Nonresonant effects play an important role in these recombination processes. We consider the quantum-mechanical foundations of the nonresonant processes and present our calculations for the differential two-photon decay rates of the 3s and 3d levels in the hydrogen atom. This article was submitted by the authors in English.     

The First Results of Tephrochronological Study of Late Pleistocene–Holocene Volcanic Eruptions in the Zhom–Bolok River Valley (Eastern Sayan)

Doklady Earth Sciences - The first results of tephrochronological studies of Late Pleistocene–Holocene volcanic eruptions in the Zhom-Bolok River valley (Eastern Sayan) are reported. Based on...     

An Unusually Powerful Water-Maser Flare in the Galactic Source W49N

The most powerful flare ever registered in the Galactic water-maser source W49N has been detected in long-term monitoring data in the 6₁₆–5₂₃ transition with line frequency f = 22.235 GHz carried out on the 22-m Simeiz, 32-m Toruń, 100-m Effelsberg, and 32-m Medicina radio telescopes, beginning in September 2017 and continuing in 2018. Some stages of the flare were monitored daily. Detailed variations of the source spectral flux density with time have been obtained. At the flare maximum, the flux exceeded P ≈ 8 × 10⁴ Jy, and this was record highest flux registered over the entire history of observations of this source. Important conclusions related to details of the mechanism for the H₂O line emission have been drawn. An exponential increase in the flare flux density was detected during both the rise and decline of the flare. The data obtained indicate that the maser is unsaturated, and remained in this state up to the maximum observed flux densities. Additional support for the idea that the maser is unsaturated is the shape of the dependence of the line width on the flux. The characteristics of the variations of the spectral flux density are probably associated with a sharp increase in the density of the medium and the photon flux that led to an increase in the temperature from an initial level of 10–40 K to hundreds of Kelvins. Interferometric maps of the object during the increase in the spectral flux density of the flare have been obtained. A possible mechanism for the primary energy release in W49N is considered.

     

Integrated Geological–Geophysical and Oceanographic Research in the South China Sea: Cruise 88 of the R/V “Akademik M.A. Lavrentyev”

Oceanology - Abstract—The paper gives brief results of comprehensive studies in the South China Sea obtained from a joint Russian–Vietnamese expedition in November 2019 (cruise 88 of...     

A Technique for Photogrammetric Estimation of Albedo of Snow–Ice Surfaces

Izvestiya, Atmospheric and Oceanic Physics - New ways to improve the original technique for assessing the albedo of snow–ice surfaces with the use of ground measurements of incoming solar...     

Georadar Investigations of the Peretolchin Glacier (Southern Siberia)

Presented are the results obtained from radar profiling of the Peretolchin glacier in the Munku-Sardyk mountain range in the south of Siberia (June 2014 and May 2016) using georadar OKO-2 with the ABDL Triton antenna unit operating at the radiation frequency of 50 and 100 MHz. The ice thickness was determined from the profiles and the ice volumes from the cross-sectional areas and distances between profiles. The ice volume was calculated for the body of the Peretolchin glacier to be 0.007 ± 0.0019 km³. An analytical method was also used to determine the ice volume according to the type and area of glacier. It is established that the correlation between the glacier volume and area is expressed by a power function V = kS ^p . The mean ice volume, calculated with due regard for different coefficients, was 0.0061 km³. The GlabTop model that assumes the cross-sectional form of the glacier was used to infer the ice volume: the mean volume for two cross-sections (parabolic and elliptic) was 0.0073 km³. It is found that over 110 years since the start of the investigation into the morphology of the Peretolchin glacier, it has increased twice in its length and in area, its volume has decreased by a factor of 3.7, and the lower boundary of the open part of the glacier has risen 184 meters during that period.     

The dynamics of contemporary glaciers in the mountains of the south of East Siberia

An analysis is made of the glaciation status of the mountains in the south of East Siberia to reveal a number of characteristics of changes in glacier systems. It is determined that the mountain systems are all experiencing a deglaciation caused by global climatic changes, while the rates of degradation have increased considerably since the late 1980s. It is established that over the last several decades the rate of thawing of glaciers has decelerated according to data for the key sites in the Kodar, Baikal’skii, Barguzin. Munku-Sardyk and Eastern-Sayan mountain ranges, which is associated with a decrease in mean annual air temperatures in 2009, 2010, 2012 and 2013 after the maximum values in 1990, 1994, 1995, 1997, 2002 and 2007. The changes recorded in the amount of solid atmospheric precipitation do not produce any definite trends in all of the mountain systems analyzed. It is determined that, given a relatively small snow accumulation, the glaciers are fed by snow avalanches and persist due to accumulation of large reserves of cold throughout long and cold winters which impede an intense ablation and promote the sustenance of glaciation. It is pointed out that the thawing of glaciers (especially cirque glaciers) involves a decrease in their thickness, whereas their area changes little.     

Experimental evidence for flexibility of a building foundation supported by concrete friction piles

This article explores the possibility to measure deformations of building foundations from measurements of ambient noise and strong motion recordings. The case under study is a seven-storey hotel building in Van Nuys, California. It has been instrumented by strong motion accelerographs, and has recorded several earthquakes, including the 1971 San Fernando (M_L=6.6, R=22 km), 1987 Whittier–Narrows (M_L=5.9, R=41 km), 1992 Landers (M_L=7.5, R=186 km), 1992 Big Bear (M_L=6.5, R=149 km), and 1994 Northridge (M_L=6.4, R=1.5 km) earthquake and its aftershocks (20 March: M_L=5.2, R=1.2 km; 6 December, 1994: M_L=4.3, R=11 km). It suffered minor structural damage in 1971 earthquake and extensive damage in 1994. Two detailed ambient vibration tests were performed following the Northridge earthquake, one before and the other one after the 20 March aftershock. These included measurements at a grid of points on the ground floor and in the parking lot surrounding the building, presented and analyzed in this article. The analysis shows that the foundation system, consisting of grade beams on friction piles, does not act as a “rigid body” but deforms during the passage of microtremor and therefore earthquake waves. For this geometrically and by design essentially symmetric building, the center of stiffness of the foundation system appears to have large eccentricity (this is seen both from the microtremor measurements and from the earthquake recordings). This eccentricity may have contributed to strong coupling of transverse and torsional responses, and to larger than expected torsional response, contributing to damage during the 1994 Northridge, earthquake.     

Effect of Electron Precipitations on the Effective Recombination Coefficient

The results of an analysis of the possible effect of auroral electron fluxes on the effective recombination coefficient α_eff in the ionosphere are presented. It is shown that the α_eff value in the E-region of the ionosphere is determined mainly by the physical-chemical properties of the medium. In the F1-layer of the ionosphere, the effective recombination coefficient becomes dependent on both the value of the energy flux and the type of the energy spectrum of the auroral electron flux.