Collisional hardening of compact binaries in globular clusters

We consider essential mechanisms for orbit shrinkage or 'hardening' of compact binaries in globular clusters (GCs) to the point of Roche lobe contact and X-ray emission phase, focusing on the process of collisional hardening due to encounters between binaries and single stars in the cluster core. The interplay between this kind of hardening and that due to emission of gravitational radiation produces a characteristic scaling of the orbit-shrinkage time with the single-star binary encounter rate γ in the cluster which we introduce, clarify and explore. We investigate possible effects of this scaling on populations of X-ray binaries in GCs within the framework of a simple 'toy' scheme for describing the evolution of pre-X-ray binaries in GCs. We find the expected qualitative trends sufficiently supported by data on X-ray binaries in Galactic GCs to encourage us towards a more quantitative study.     

The symbiotic star CH Cygni – I. Non-thermal bipolar jets

Very Large Array surface brightness and spectral index maps of the evolving extended emission of the triple symbiotic star CH Cygni are presented. These are derived from observations at 4.8, 8.4 and 14 GHz between 1985 and 1999. The maps are dominated by thermal emission around the central bright peak of the nebula, but we also find unambiguous non-thermal emission associated with the extended regions. Our observations confirm that this is a jet. The central region has been associated with the stellar components through Hubble Space Telescope imaging. If the jets are the result of ejection events at outburst, expansion velocities are consistent with those from other measurement methods. We propose that the non-thermal emission is caused by material ejected in the bipolar jets interacting with the circumstellar wind envelope. The resulting shocks lead to local enhancements in the magnetic field from the compact component of the order of 3 mG.     

Environmental factors influencing aggregation of manta rays (Manta birostris) off the northeastern coast of the Yucatan Peninsula

Manta rays inhabit tropical, subtropical and temperate waters. Aggregation sites of manta rays have been recognized worldwide, but the reasons for this behavior are still poorly understood. This study describes environmental factors influencing aggregation sites of the giant manta ray (Manta birostris) off the northeastern coast of the Yucatan Peninsula. Observations of manta rays were obtained from scientific surveys conducted during 2006–2011. Environmental data were obtained from satellite imagery. The maximum entropy (Maxent) method for habitat modeling was used to determine the effects of environmental conditions on the species and predict suitable habitat for manta rays in this region. Primary productivity and distance to the coast were the most influential variables, suggesting that aggregation occurs in highly productive coastal waters. The distribution of manta rays predicted by the Maxent model showed that the most suitable habitat within the study area is located off the northeastern coast of the Yucatán Peninsula, more precisely, northeast of Isla Holbox and northwest of Isla Contoy. Seasonal patterns of distribution suggest that the most suitable conditions are present from July through September.     

Physical modeling of long-range infrasonic propagation in the atmosphere

The results of experiments on the physical modeling of long-range infrasonic propagation in the atmosphere are given. Such modeling is based on the possible coincidence between the forms of the vertical profiles of the effective sound speed stratification in the atmospheric boundary layer (between 0 and 600 m for the case under consideration) and in the atmosphere as a whole (from the land surface up to thermospheric heights (about 150 km)). The source of acoustic pulses was an oscillator of detonation type. Owing to the detonation of a gas mixture of air (or oxygen) and propane, this generator was capable of producing short, powerful (the maximum acoustic pressure was on the order of 30 to 60 Pa at a distance of 50 to 100 m from the oscillator), and sufficiently stable acoustic pulses with a spectral maximum at frequencies of 40 to 60 Hz and a pulsing period of 20 to 30 s. The sites of acoustic-signal recording were located at different distances (up to 6.5 km) from the source and in different azimuthal directions. The temperature and wind stratifications were monitored in real time during the experiments with an acoustic locator—a sodar—and a temperature profiler. The data on the physical modeling of long-range sound propagation in the atmosphere are analyzed to verify the physical and mathematical models of predicting acoustic fields in the inhomogeneous moving atmosphere on the basis of the parabolic equation and the method of normal waves. A satisfactory agreement between calculated and experimental data is obtained. One more task was to compare the theoretical relations between variations in the azimuths and angles of tilting of sound rays about the horizon and the parameters of anisotropic turbulence in the lower troposphere and stratosphere with the experimental data. A theoretical interpretation of the experimental results is proposed on the basis of the theory of anisotropic turbulence in the atmosphere. The theoretical and experimental results are compared, and a satisfactory agreement between these results is noted.     

New stellar members of the Coma Berenices open star cluster

We present the results of a survey of the Coma Berenices open star cluster (Melotte 111), undertaken using proper motions from the USNO-B1.0 (United States Naval Observatory) and photometry from the Two-Micron All-Sky Survey (2MASS) Point Source catalogues. We have identified 60 new candidate members with masses in the range  1.007 < M < 0.269 M_⊙  . For each we have estimated a membership probability by extracting control clusters from the proper motion vector diagram. All 60 are found to have greater than 60 per cent probability of being members, more than doubling the number of known cluster members. The new luminosity function for the cluster peaks at bright magnitudes, but is rising at   K ≈ 12  , indicating that it is likely that lower mass members may exist. The mass function also supports this hypothesis.     

On the evolution of low mas binary systems

The evolution of parameters of close binary systems containing a red dwarf (with mass loss) and a condensed star is investigated. The mass loss from the system and asynchronism of the red dwarf rotation are taken into consideration. The calculations show that if the initial mass ratioq ₀2 then during 10⁷ yr the instability of mass loss process arises, and a bright X-ray source forms with luminosity close to the Eddington one. Ifq ₀>2 then during the mass loss phase the bright X-ray source arises twice. The models explain the existence of the forbidden interval of orbital periods and the absence of systems with periods less than 80 min.     

The structure of a type-II supernova remnant G 160.5+2.8 (HB-9) observed at λ=12m

A two-dimensional brightness distribution of the old supernova remnant G 160.5+2.8 (HB-9) has been measured at a frequency of 25 MHz with the T-Shaped UTR-2 radio telescope, with the resolution 29×27. The source has a distinctly pronounced, almost spherical envelope. At the same time, individual features located near the internal boundary of the source are observable.Certain considerations are put forward to validate a suggestion that the brightest feature in the decameter range (maximum at=4^h55^m.3 and =46°.37) might be of an extragalactic origin.From structure considerations, the velocity of the pulsar PSR 0459+47 projected on HB-9 is estimated. The estimate does not contradict the hypothesis of Damasheket al. (1978) concerning a possible genetic relation between HB-9 and PSR 0459+47.     

Small hypervelocity particles captured in aerogel collectors: Location,extraction, handling and storage

Abstract— It has now been about a decade since the first demonstrations that hypervelocity particles could be captured, partially intact, in aerogel collectors. But the initial promise of a bonanza of partially‐intact extraterrestrial particles, collected in space, has yet to materialize. One of the difficulties that investigators have encountered is that the location, extraction, handling and analysis of very small (10 μm and less) grains, which constitute the vast majority of the captured particles, is challenging and burdensome. Furthermore, current extraction techniques tend to be destructive over large areas of the collectors. Here we describe our efforts to alleviate some of these difficulties. We have learned how to rapidly and efficiently locate captured particles in aerogel collectors, using an automated microscopic scanning system originally developed for experimental nuclear astrophysics. We have learned how to precisely excavate small access tunnels and trenches using an automated micromanipulator and glass microneedles as tools. These excavations are only destructive to the collector in a very small area—this feature may be particularly important for excavations in the precious Stardust collectors. Using actuatable silicon microtweezers, we have learned how to extract and store “naked” particles—essentially free of aerogel—as small as 3 μm in size. We have also developed a technique for extracting particles, along with their terminal tracks, still embedded in small cubical aerogel blocks. We have developed a novel method for storing very small particles in etched nuclear tracks. We have applied these techniques to the extraction and storage of grains captured in aerogel collectors (Particle Impact Experiment, Orbital Debris Collector Experiment, Comet‐99) in low Earth orbit.     

Roche volume filling and the dissolution of open star clusters

From direct N‐body simulations we find that the dynamical evolution of star clusters is strongly influenced by the Roche volume filling factor. We present a parameter study of the dissolution of open star clusters with different Roche volume filling factors and different particle numbers. We study both Roche volume underfilling and overfilling models and compare with the Roche volume filling case. We find that in the Roche volume overfilling limit of our simulations two‐body relaxation is no longer the dominant dissolution mechanism but the changing cluster potential. We call this mechanism “mass‐loss driven dissolution” in contrast to “two‐body relaxation driven dissolution” which occurs in the Roche volume underfilling regime. We have measured scaling exponents of the dissolution time with the two‐body relaxation time. In this experimental study we find a decreasing scaling exponent with increasing Roche volume filling factor. The evolution of the escaper number in the Roche volume overfilling limit can be described by a log‐logistic differential equation. We report the finding of a resonance condition which may play a role for the evolution of star clusters and may be calibrated by the main periodic orbit in the large island of retrograde quasiperiodic orbits in the Poincaré surfaces of section. We also report on the existence of a stability curve which may be of relevance with respect to the structure of star clusters. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Recent geodynamics of dangerous faults

The analysis of the existing information concerning the present-day deformation activity of the fault zones in seismically active and aseismic regions suggests that the notions of an active fault and a dangerous fault should be distinguished. It is shown that a fault which is active for an expert in geotectonics will not be considered dangerous by an expert in geotechnical monitoring of buildings. The definition is given according to which a dangerous fault is understood as a zone of linear destruction which accommodates the contemporary short-period (a few months and years) pulsed and/or alternating motions with strain rates above 5 × 10^–5 per annum and earthquakes with M ≥ 5. A technique is developed for identifying the dangerous faults based on monitoring the recent ground surface displacements in accordance with a special protocol which ensures an increased degree of detail in time and space. Based on the idea of the probable accumulation of dangerous strains during the operating cycle of the objects, the criteria for assessing their geodynamical risks are formulated.