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Журнальные статьи

1. U03691
Ade P. a. R. et al. Planck intermediate results. XXVI. Optical identification and redshifts of Planck clusters with the RTT150 telescope // Astron. Astrophys. 2015. Vol. 582. P. A29.

We present the results of approximately three years of observations of Planck Sunyaev-Zeldovich (SZ) sources with the Russian-Turkish 1.5m telescope (RTT150), as a part of the optical follow-up programme undertaken by the Planck collaboration. During this time period approximately 20% of all dark and grey clear time available at the telescope was devoted to observations of Planck objects. Some observations of distant clusters were also done at the 6 m Bolshoi Telescope Alt-azimutalnyi (BTA) of the Special Astrophysical Observatory of the Russian Academy of Sciences. In total, deep, direct images of more than one hundred fields were obtained in multiple filters. We identified 47 previously unknown galaxy clusters, 41 of which are included in the Planck catalogue of SZ sources. The redshifts of 65 Planck clusters were measured spectroscopically and 14 more were measured photometrically. We discuss the details of cluster optical identifications and redshift measurements. We also present new spectroscopic redshifts for 39 Planck clusters that were not included in the Planck SZ source catalogue and are published here for the first time.


2. U03691
Aghanim N. et al. Planck intermediate results XXVII. High-redshift infrared galaxy overdensity candidates and lensed sources discovered by Planck and confirmed by Herschel-SPIRE // Astron. Astrophys. 2015. Vol. 582. P. A30.

We have used the Planck all-sky submillimetre and millimetre maps to search for rare sources distinguished by extreme brightness, a few hundred millijanskies, and their potential for being situated at high redshift. These "cold" Planck sources, selected using the High Frequency Instrument (HFI) directly from the maps and from the Planck Catalogue of Compact Sources (PCCS), all satisfy the criterion of having their rest-frame far-infrared peak redshifted to the frequency range 353-857 GHz. This colour-selection favours galaxies in the redshift range z = 2-4, which we consider as cold peaks in the cosmic infrared background. With a 4.'5 beam at the four highest frequencies, our sample is expected to include overdensities of galaxies in groups or clusters, lensed galaxies, and chance line-of-sight projections. We perform a dedicated Herschel-SPIRE follow-up of 234 such Planck targets, finding a significant excess of red 350 and 500 mu m sources, in comparison to reference SPIRE fields. About 94% of the SPIRE sources in the Planck fields are consistent with being overdensities of galaxies peaking at 350 mu m, with 3% peaking at 500 mu m, and none peaking at 250 mu m. About 3% are candidate lensed systems, all 12 of which have secure spectroscopic confirmations, placing them at redshifts z > 2.2. Only four targets are Galactic cirrus, yielding a success rate in our search strategy for identifying extragalactic sources within the Planck beam of better than 98%. The galaxy overdensities are detected with high significance, half of the sample showing statistical significance above 10 sigma. The SPIRE photometric redshifts of galaxies in overdensities suggest a peak at z similar or equal to 2, assuming a single common dust temperature for the sources of T-d = 35 K. Under this assumption, we derive an infrared (IR) luminosity for each SPIRE source of about 4x10(12) L-circle dot, yielding star formation rates of typically 700 M-circle dot yr(-1). If the observed overdensities are actual gravitationally-bound structures, the total IR luminosity of all their SPIRE-detected sources peaks at 4 x 10(13) L-circle dot, leading to total star formation rates of perhaps 7 x 10(3) M-circle dot yr(-1) per overdensity. Taken together, these sources show the signatures of high-z (z > 2) protoclusters of intensively star-forming galaxies. All these observations confirm the uniqueness of our sample compared to reference samples and demonstrate the ability of the all-sky Planck-HFI cold sources to select populations of cosmological and astrophysical interest for structure formation studies.


3. U03691
Barnes S.A. et al. A color-period diagram for the open cluster M48 (NGC2548), and its rotational age // Astron. Astrophys. 2015. Vol. 583. P. A73.


4. U03691
Benic S. et al. A new quark-hadron hybrid equation of state for astrophysics I. High-mass twin compact stars // Astron. Astrophys. 2015. Vol. 577. P. A40.

Aims. We present a new microscopic hadron-quark hybrid equation of state model for astrophysical applications, from which compact hybrid star configurations are constructed. These are composed of a quark core and a hadronic shell with a first-order phase transition at their interface. The resulting mass-radius relations are in accordance with the latest astrophysical constraints. Methods. The quark matter description is based on a quantum chromodynamics (QCD) motivated chiral approach with higher-order quark interactions in the Dirac scalar and vector coupling channels. For hadronic matter we select a relativistic mean-field equation of state with density-dependent couplings. Since the nucleons are treated in the quasi-particle framework, an excluded volume correction has been included for the nuclear equation of state at suprasaturation density which takes into account the finite size of the nucleons. Results. These novel aspects, excluded volume in the hadronic phase and the higher-order repulsive interactions in the quark phase, lead to a strong first-order phase transition with large latent heat, i.e. the energy-density jump at the phase transition, which fulfils a criterion for a disconnected third-family branch of compact stars in the mass-radius relationship. These twin stars appear at high masses (similar to 2 M-circle dot) that are relevant for current observations of high-mass pulsars. Conclusions. This analysis offers a unique possibility by radius observations of compact stars to probe the QCD phase diagram at zero temperature and large chemical potential and even to support the existence of a critical point in the QCD phase diagram.


5. U03691
Bernhard K. et al. A search for photometric variability in magnetic chemically peculiar stars using ASAS-3 data // Astron. Astrophys. 2015. Vol. 581. P. A138.

Context. The (magnetic) chemically peculiar (CP) stars of the upper main sequence are well-suited laboratories for investigating the influence of magnetic fields on the stellar surface because they produce abundance inhomogeneities (spots), which results in photometric variability that is explained in terms of the oblique rotator model. CP stars exhibiting this phenomenon are normally classified as alpha(2) Canum Venaticorum (ACV) variables. It is important to increase the sample of known rotational periods among CP stars by discovering new ACV variables. An increased sample size will contribute to the understanding of the CP stars' evolution in time. Aims. We aim at discovering new ACV variables in the public data of the third phase of the All Sky Automated Survey (ASAS-3). Furthermore, by analysis of the available photometric data, we intend to derive rotational periods of the stars. Methods. The ASAS-3 data were cross-correlated with the Catalogue of Ap, HgMn, and Am stars in order to analyse the light curves of bona fide CP and related stars. The light curves were downloaded and cleaned of outliers and data points with a flag indicating bad quality. Promising candidates showing a larger scatter than observed for constant stars in the corresponding magnitude range were searched for periodic signals using a standard Fourier technique. Objects exhibiting periodic signals well above the noise level were considered and visually inspected, whereas borderline cases were rejected. Results. In total, we found 323 variables, from which 246 are reported here for the first time, and 77 were probably wrongly classified before. The observed variability pattern of most stars is in accordance with an ACV classification. For some cases, it is difficult to distinguish between the light curves of double-waved ACVs and the variability induced by orbital motion (ellipsoidal variables/eclipsing variables), especially for objects exhibiting very small amplitudes and/or significant scatter in their light curves. Thus, some eclipsing or rotating ellipsoidal variables might be present. However, we are confident that the given periods are the correct ones. There seems to be a possible weak correlation between the rotational period and colour, in the sense that cooler magnetic CP stars rotate more slowly. However, this correlation seems to disappear when correcting for the interstellar reddening. Conclusions. The next steps have to include a compilation of all available rotational periods from the literature and a detailed investigation of the astrophysical parameters of these stars. This includes a determination of the individual masses, luminosities, ages, and inclination angles. However, this information cannot be straightforwardly determined from photometric data alone.


6. U03691
Boesch A., Reiners A. Spectral line lists of a nitrogen gas discharge for wavelength calibration in the range 4500-11 000 cm(-1) // Astron. Astrophys. 2015. Vol. 582. P. A43.

Context. A discharge of nitrogen gas, as created in a microwave-induced plasma, exhibits a very dense molecular emission line spectrum. Emission spectra of this kind could serve as wavelength calibrators for high-resolution astrophysical spectrographs in the near-infrared, where only very few calibration sources are currently available. Aims. The compilation of a spectral line list and the characterization of line intensities and line density belong to the initial steps when investigating the feasibility of potential wavelength calibration sources. Although the molecular nitrogen spectrum was extensively studied in the past, to our knowledge, no line list exists that covers a continuous range of several thousand wavenumbers in the near-infrared. Methods. We recorded three high-resolution (Delta(v) over tilde = 0.018 cm(-1)) spectra of a nitrogen gas discharge operated at different microwave powers. The nitrogen gas is kept inside a sealed glass cell at a pressure of 2 mbar. The emission lines in the spectra were fitted by a superposition of Gaussian profiles to determine their position, relative intensity, and width. The line parameters were corrected for an absolute wavelength scale, instrumental line broadening, and intensity modulation. Molecular and atomic transitions of nitrogen were identified with available line positions from the literature. Results. We report line lists with more than 40 000 emission lines in the spectral range 4500-11 000 cm(-1) (0.9-2.2 mu m). The spectra exhibit emission lines over the complete spectral range under investigation with about 350-1300 lines per 100 cm(-1). Depending on the microwave power, a fraction of 35-55% of all lines are blended. The total dynamic range of the detected lines covers about four orders of magnitude. Conclusions. Line density and peak intensities qualify the recorded discharge as a useful wavelength calibrator, and the line list provides an empirical reference for nitrogen spectra in the near-infrared.


7. U03691
Clark J.S. et al. A long-period Cepheid variable in the starburst cluster VdBH222 // Astron. Astrophys. 2015. Vol. 584. P. L12.

Context. Galactic starburst clusters play a twin role in astrophysics, serving as laboratories for the study of stellar physics and also delineating the structure and recent star formation history of the Milky Way. Aims. In order to exploit these opportunities we have undertaken a spectroscopic survey of the red supergiant dominated young massive clusters thought to be present at both near and far ends of the Galactic Bar. Methods. Specifically, multi-epoch observations were employed to identify and investigate stellar variability and its potential role in initiating mass loss amongst the cool super-/hypergiant populations of these aggregates. Results. Significant spectroscopic variability suggestive of radial pulsations was found for the yellow supergiant VdBH 222 #505. Follow-up photometric investigations revealed modulation with a period of similar to 23.325 d; both timescale and pulsational profile are consistent with a Cepheid classification. Conclusions. #505 is one of the longest period Galactic cluster Cepheids identified to date and hence of considerable use in constraining the bright end of the period/luminosity relation at solar metallicities. In conjunction with extant photometry we infer a distance of similar to 6 kpc for VdBH222 and an age of similar to 20 Myr. This results in a moderate reduction in both the integrated cluster mass (similar to 2x 10(4) M-circle dot) and the initial masses of the evolved cluster members (similar to 10 M-circle dot). As such VdBH222 becomes an excellent test-bed for studying the properties of some of the lowest mass stars observed to undergo type-II supernovae. Moreover, the distance is in tension with a location of VdBH 222 at the far end of the Galactic Bar. Instead a birthsite in the near 3 kpc arm is suggested; providing compelling evidence of extensive recent star formation in a region of the inner Milky Way which has hitherto been thought to be devoid of such activity.


8. U03691
Collado A. et al. A new massive double-lined spectroscopic binary system: The Wolf-Rayet star WR68a // Astron. Astrophys. 2015. Vol. 581. P. A49.

Double-lined spectroscopic binary systems, containing a Wolf-Rayet and a massive O-type star, are key objects for the study of massive star evolution because these kinds of systems allow the determination of fundamental astrophysical parameters of their components. We have performed spectroscopic observations of the star WR 68a as part of a dedicated monitoring program of WR stars to discover new binary systems. We identified spectral lines of the two components of the system and disentangled the spectra. We measured the radial velocities in the separated spectra and determined the orbital solution. We discovered that WR 68a is a double-lined spectroscopic binary with an orbital period of 5.2207 days, very small or null eccentricity, and inclination ranging between 75 and 85 deg. We classified the binary components as WN6 and O5.5-6. The WN star is less massive than the O-type star with minimum masses of 15 +/- 5 M-circle dot and 30 +/- 4 M-circle dot, respectively. The equivalent width of the He II lambda 4686 emission line shows variations with the orbital phase, presenting a minimum when the WN star is in front of the system. The light curve constructed from available photometric data presents minima in both conjunctions of the system.


9. U03653
Conroy K.E. et al. Kepler Eclipsing Binary Stars. Iv. Precise Eclipse Times for Close Binaries and Identification of Candidate Three-Body Systems // Astron. J. 2014. Vol. 147, № 2. P. 45.

We present a catalog of precise eclipse times and analysis of third-body signals among 1279 close binaries in the latest Kepler Eclipsing Binary Catalog. For these short-period binaries, Kepler's 30 minute exposure time causes significant smearing of light curves. In addition, common astrophysical phenomena such as chromospheric activity, as well as imperfections in the light curve detrending process, can create systematic artifacts that may produce fictitious signals in the eclipse timings. We present a method to measure precise eclipse times in the presence of distorted light curves, such as in contact and near-contact binaries which exhibit continuously changing light levels in and out of eclipse. We identify 236 systems for which we find a timing variation signal compatible with the presence of a third body. These are modeled for the light travel time effect and the basic properties of the third body are derived. This study complements J.A. Orosz et al. (in preparation), which focuses on eclipse timing variations of longer period binaries with flat out-of-eclipse regions. Together, these two papers provide comprehensive eclipse timings for all binaries in the Kepler Eclipsing Binary Catalog, as an ongoing resource freely accessible online to the community.


10. U03691
Covino S. et al. Short timescale photometric and polarimetric behavior of two BL Lacertae type objects // Astron. Astrophys. 2015. Vol. 578. P. A68.

Context. Blazars are astrophysical sources whose emission is dominated by non-thermal processes, i.e. synchrotron and inverse Compton emission. Although the general picture is rather robust and consistent with observations, many aspects are still unexplored. Aims. Polarimetric monitoring can off er a wealth of information about the physical processes in blazars. Models with largely different physical ingredients can provide almost indistinguishable predictions for the total flux, but usually are characterized by different polarization properties. We explore the possibility to derive structural information about the emitting regions of blazars by means of a joint analysis of rapid variability of the total and polarized flux at optical wavelengths. Methods. Short timescale (from tens of seconds to a couple of minutes) optical linear polarimetry and photometry for two blazars, BL Lacertae and PKS 1424+240, was carried out with the PAOLO polarimeter at the 3.6 m Telescopio Nazionale Galileo. Several hours of almost continuous observations were obtained for both sources. Results. Our intense monitoring allowed us to draw different scenarios for BL Lacertae and PKS 1424+240, with the former characterized by intense variability and the latter practically constant in total flux. Essentially the same behavior is observed for the polarized flux and the position angle. The variability time-scales turned out to be as short as a few minutes, although involving only a few percent variation of the flux. The polarization variability time-scale is generally consistent with the total flux variability. Total and polarized flux appear to be essentially uncorrelated. However, even during our relatively short monitoring, different regimes can be singled out. Conclusions. No simple scenario is able to satisfactorily model the very rich phenomenology exhibited in our data. Detailed numerical simulations show that the emitting region should be characterized by some symmetry, and the inclusion of turbulence for the magnetic field may constitute the missing ingredient for a more complete interpretation of the data.


11. U03653
Curtis J.L. et al. Ruprecht 147: The Oldest Nearby Open Cluster as a New Benchmark for Stellar Astrophysics // Astron. J. 2013. Vol. 145, № 5. P. 134.

Ruprecht 147 is a hitherto unappreciated open cluster that holds great promise as a standard in fundamental stellar astrophysics. We have conducted a radial velocity survey of astrometric candidates with Lick, Palomar, and MMT observatories and have identified over 100 members, including 5 blue stragglers, 11 red giants, and 5 double-lined spectroscopic binaries (SB2s). We estimate the cluster metallicity from spectroscopic analysis, using Spectroscopy Made Easy (SME), and find it to be [M/H] = +0.07 +/- 0.03. We have obtained deep CFHT/MegaCam g'r'i'z' photometry and fit Padova isochrones to the (g' - i') and Two Micron All Sky Survey (J - K-S) color-magnitude diagrams, using the tau(2) maximum-likelihood procedure of Naylor, and an alternative method using two-dimensional cross-correlations developed in this work. We find best fits for Padova isochrones at age t = 2.5 +/- 0.25 Gyr, m - M = 7.35 +/- 0.1, and A(V) = 0.25 +/- 0.05, with additional uncertainty from the unresolved binary population and possibility of differential extinction across this large cluster. The inferred age is heavily dependent on our choice of stellar evolution model: fitting Dartmouth and PARSEC models yield age parameters of 3 Gyr and 3.25 Gyr, respectively. At similar to 300 pc and similar to 3 Gyr, Ruprecht 147 is by far the oldest nearby star cluster.


12. U03691
Deal M., Richard O., Vauclair S. Accretion of planetary matter and the lithium problem in the 16 Cygni stellar system // Astron. Astrophys. 2015. Vol. 584. P. A105.

Context. The 16 Cygni system is composed of two solar analogues with similar masses and ages. A red dwarf is in orbit around 16 Cygni A, and 16 Cygni B hosts a giant planet. The abundances of heavy elements are similar in the two stars, but lithium is much more depleted in 16 Cygni B than in 16 Cygni A, by a factor of at least 4.7. Aims. The interest of studying the 16 Cygni system is that the two star have the same age and the same initial composition. The differences currently observed must be due to their different evolution, related to the fact that one of them hosts a planet while the other does not. Methods. We computed models of the two stars that precisely fit the observed seismic frequencies. We used the Toulouse Geneva Evolution Code (TGEC), which includes complete atomic diffusion (including radiative accelerations). We compared the predicted surface abundances with the spectroscopic observations and confirm that another mixing process is needed. We then included the effect of accretion-induced fingering convection. Results. The accretion of planetary matter does not change the metal abundances but leads to lithium destruction, which depends upon the accreted mass. A fraction of the Earth's mass is enough to explain the lithium surface abundances of 16 Cygni B. We also checked the beryllium abundances. Conclusions. In the case of accretion of heavy matter onto stellar surfaces, the accreted heavy elements do not remain in the outer convective zones, but are mixed downwards by fingering convection induced by the unstable mu-gradient. Depending on the accreted mass, this mixing process may transport lithium down to its nuclear destruction layers and lead to an extra lithium depletion at the surface. A fraction of the Earth's mass is enough to explain a lithium ratio of 4.7 in the 16 Cygni system. In this case beryllium is not destroyed. Such a process may be frequent in planet-hosting stars and should be studied in other cases in the future.


13. U03691
Dieckmann M.E. et al. Particle-in-cell simulation study of the interaction between a relativistically moving leptonic micro-cloud and ambient electrons // Astron. Astrophys. 2015. Vol. 577. P. A137.

Context. The jets of compact accreting objects are composed of electrons and a mixture of positrons and ions. These outflows impinge on the interstellar or intergalactic medium and both plasmas interact via collisionless processes. Filamentation (beam-Weibel) instabilities give rise to the growth of strong electromagnetic fields. These fields thermalize the interpenetrating plasmas. Aims. Hitherto, the effects imposed by a spatial non-uniformity on filamentation instabilities have remained unexplored. We examine the interaction between spatially uniform background electrons and a minuscule cloud of electrons and positrons. The cloud size is comparable to that created in recent laboratory experiments and such clouds may exist close to internal and external shocks of leptonic jets. The purpose of our study is to determine the prevalent instabilities, their ability to generate electromagnetic fields and the mechanism, by which the lepton micro-cloud transfers energy to the background plasma. Methods. A square micro-cloud of equally dense electrons and positrons impinges in our particle-in-cell (PIC) simulation on a spatially uniform plasma at rest. The latter consists of electrons with a temperature of 1 keV and immobile ions. The initially charge- and current neutral micro-cloud has a temperature of 100 keV and a side length of 2.5 plasma skin depths of the micro-cloud. The side length is given in the reference frame of the background plasma. The mean speed of the micro-cloud corresponds to a relativistic factor of 15, which is relevant for laboratory experiments and for relativistic astrophysical outflows. The spatial distributions of the leptons and of the electromagnetic fields are examined at several times. Results. A filamentation instability develops between the magnetic field carried by the micro-cloud and the background electrons. The electromagnetic fields, which grow from noise levels, redistribute the electrons and positrons within the cloud, which boosts the peak magnetic field amplitude. The current density and the moduli of the electromagnetic fields grow aperiodically in time and steadily along the direction that is anti-parallel to the cloud's velocity vector. The micro-cloud remains conjoined during the simulation. The instability induces an electrostatic wakefield in the background plasma. Conclusions. Relativistic clouds of leptons can generate and amplify magnetic fields even if they have a microscopic size, which implies that the underlying processes can be studied in the laboratory. The interaction of the localized magnetic field and high-energy leptons will give rise to synchrotron jitter radiation. The wakefield in the background plasma dissipates the kinetic energy of the lepton cloud. Even the fastest lepton micro-clouds can be slowed down by this collisionless mechanism. Moderately fast charge-and current neutralized lepton micro-clouds will deposit their energy close to relativistic shocks and hence they do not constitute an energy loss mechanism for the shock.


14. U03691
Fouvry J.B. et al. Secular diffusion in discrete self-gravitating tepid discs II. Accounting for swing amplification via the matrix method // Astron. Astrophys. 2015. Vol. 584. P. A129.

The secular evolution of an infinitely thin tepid isolated galactic disc made of a finite number of particles is investigated using the inhomogeneous Balescu-Lenard equation expressed in terms of angle-action variables. The matrix method is implemented numerically in order to model the induced gravitational polarisation. Special care is taken to account for the amplification of potential fluctuations of mutually resonant orbits and the unwinding of the induced swing amplified transients. Quantitative comparisons with N-body simulations yield consistent scalings with the number of particles and with the self-gravity of the disc: the fewer the particles and the colder the disc, the faster the secular evolution. Secular evolution is driven by resonances, but does not depend on the initial phases of the disc. For a Mestel disc with Q similar to 1.5, the polarisation cloud around each star boosts its secular effect by a factor of a thousand or more, accordingly promoting the dynamical relevance of self-induced collisional secular evolution. The position and shape of the induced resonant ridge are found to be in very good agreement with the prediction of the Balescu-Lenard equation, which scales with the square of the susceptibility of the disc. In astrophysics, the inhomogeneous Balescu-Lenard equation may describe the secular diffusion of giant molecular clouds in galactic discs, the secular migration and segregation of planetesimals in proto-planetary discs, or even the long-term evolution of population of stars within the Galactic centre. It could be used as a valuable check of the accuracy of N-body integrators on secular timescales.


15. U03691
Fouvry J.B., Pichon C., Chavanis P.H. Secular diffusion in discrete self-gravitating tepid discs I. Analytic solution in the tightly wound limit // Astron. Astrophys. 2015. Vol. 581. P. A139.

The secular evolution of an infinitely thin tepid isolated galactic disc made of a finite number of particles is described using the inhomogeneous Balescu-Lenard equation. Assuming that only tightly wound transient spirals are present in the disc, a WKB approximation provides a simple and tractable quadrature for the corresponding drift and diffusion coefficients. It provides insight into the physical processes at work during the secular diffusion of a self-gravitating discrete disc and makes quantitative predictions on the initial variations of the distribution function in action space. When applied to the secular evolution of an isolated stationary self-gravitating Mestel disc, this formalism predicts the initial importance of the corotation resonance in the inner regions of the disc leading to a regime involving radial migration and heating. It predicts in particular the formation of a ridge-like feature in action space, in agreement with simulations, but over-estimates the timescale involved in its appearance. Swing amplification is likely needed to resolve this discrepancy. In astrophysics, the inhomogeneous Balescu-Lenard equation and its WKB limit may also describe the secular diffusion of giant molecular clouds in galactic discs, the secular migration and segregation of planetesimals in proto-planetary discs, or even the long-term evolution of population of stars within the Galactic centre.


16. U03691
Gounelle M. The abundance of Al-26-rich planetary systems in the Galaxy // Astron. Astrophys. 2015. Vol. 582. P. A26.

One of the most puzzling properties of the solar system is the high abundance at its birth of Al-26, a short-lived radionuclide with a mean life of 1 Myr. Now decayed, it has left its imprint in primitive meteoritic solids. The origin of Al-26 in the early solar system has been debated for decades and strongly constrains the astrophysical context of the Sun and planets formation. We show that, according to the present understanding of star-formation mechanisms, it is very unlikely that a nearby supernova has delivered Al-26 into the nascent solar system. A more promising model is the one whereby the Sun formed in a wind-enriched, Al-26-rich dense shell surrounding a massive star (M > 32 M-circle dot). We calculate that the probability of any given star in the Galaxy being born in such a setting, corresponding to a well-known mode of star formation, is of the order of 1%. It means that our solar system, though not the rule, is relatively common and that many exo-planetary systems in the Galaxy might exhibit comparable enrichments in Al-26. Such enrichments played an important role in the early evolution of planets because Al-26 is the main heat source for planetary embryos.


17. U03691
Gronke M., Mota D.F., Winther H.A. Universal predictions of screened modified gravity on cluster scales // Astron. Astrophys. 2015. Vol. 583. P. A123.

Modified gravity models require a screening mechanism to be able to evade the stringent constraints from local gravity experiments and, at the same time, give rise to observable astrophysical and cosmological signatures. Such screened modified gravity models necessarily have dynamics determined by complex nonlinear equations that usually need to be solved on a model-by-model basis to produce predictions. This makes testing them a cumbersome process. In this paper, we investigate whether there is a common signature for all the different models that is suitable to testing them on cluster scales. To do this we propose an observable related to the fifth force, which can be observationally related to the ratio of dynamical-to-lensing mass of a halo, and then show that the predictions for this observable can be rescaled to a near universal form for a large class of modified gravity models. We demonstrate this using the Hu-Sawicki f(R), the Symmetron, the nDGP, and the Dilaton models, as well as unifying parametrizations. The universal form is determined by only three quantities: a strength, a mass, and a width parameter. We also show how these parameters can be derived from a specific theory. This self-similarity in the predictions can hopefully be used to search for signatures of modified gravity on cluster scales in a model-independent way.


18. U03691
Guiglion G. et al. The Gaia-ESO Survey: New constraints on the Galactic disc velocity dispersion and its chemical dependencies // Astron. Astrophys. 2015. Vol. 583. P. A91.

Context. Understanding the history and the evolution of the Milky Way is one of the main goals of modern astrophysics. In particular, the formation of the Galactic disc is a key problem of Galactic archaeology. Aims. We study the velocity dispersion behaviour of Galactic disc stars as a function of the [Mg/Fe] ratio, which for small metallicity bins can be used as a proxy of relative age. This key relation is essential to constrain the formation mechanisms of the disc stellar populations as well as the cooling and settling processes. Methods. We used the recommended parameters and chemical abundances of 7800 FGK Milky Way field stars from the second internal data release of the Gaia-ESO spectroscopic Survey. These stars were observed with the GIRAFFE spectrograph (HR10 and HR21 setups), and cover a large spatial volume in the intervals 6 < R < 10 kpc and vertical bar Z vertical bar < 2 kpc. Based on a chemical criterion, we separated the thin- from the thick-disc sequence in the [Mg/Fe] vs. [Fe/H] plane. Results. From analysing the Galactocentric velocity of the stars for the thin disc, we find a weak positive correlation between 170 and [Fe/H] that is due to a slowly rotating [Fe/H]-poor tail. For the thick disc stars, a strong correlation with [Fe/H] and [Mg/Fe] is established. In addition, we have detected an inversion of the velocity dispersion trends with [Mg/Fe] for thick-disc stars with [Fe/H] < -0.10 dex and [Mg/Fe] > +0.20 dex for the radial component. First, the velocity dispersion increases with [Mg/Fe] at all [Fe/H] ratios for the thin-disc stars, and then it decreases for the thick-disc population at the highest [Mg/Fe] abundances Similar trends are observed for several bins of [Mg/Fe] within the errors for the azimuthal velocity dispersion, while a continuous increase with [Mg/Fe] is observed for the vertical velocity dispersion. The velocity dispersion decrease agrees with previous measurements of the RAVE survey, although it is observed here for a greater metallicity interval and a larger spatial volume. Conclusions. Thanks to the Gaia-ESO Survey data, we confirm the existence of [Mg/Fe]-rich thick-disc stars with cool kinematics in the generally turbulent context of the primitive Galactic disc. This is discussed in the framework of the different disc formation and evolution scenarios.


19. U03691
Hartman H. et al. The FERRUM project: Experimental lifetimes and transition probabilities from highly excited even 4d levels in Fe II // Astron. Astrophys. 2015. Vol. 584. P. A24.

We report lifetime measurements of the 6 levels in the 3d(6)(5D)4d e(6)G term in Fe II at an energy of 10.4 eV, and f-values for 14 transitions from the investigated levels. The lifetimes were measured using time-resolved laser-induced fluorescence on ions in a laser-produced plasma. The high excitation energy, and the fact that the levels have the same parity as the the low-lying states directly populated in the plasma, necessitated the use of a two-photon excitation scheme. The probability for this process is greatly enhanced by the presence of the 3d(6)(D-5)4p z(6)F levels at roughly half the energy difference. The f-values are obtained by combining the experimental lifetimes with branching fractions derived using relative intensities from a hollow cathode discharge lamp recorded with a Fourier transform spectrometer. The data is important for benchmarking atomic calculations of astrophysically important quantities and useful for spectroscopy of hot stars.


20. U03691
Hertfelder M., Kley W. Wave mediated angular momentum transport in astrophysical boundary layers // Astron. Astrophys. 2015. Vol. 579. P. A54.

Context. Disk accretion onto weakly magnetized stars leads to the formation of a boundary layer (BL) where the gas loses its excess kinetic energy and settles onto the star. There are still many open questions concerning the BL, for instance the transport of angular momentum (AM) or the vertical structure. Aims. It is the aim of this work to investigate the AM transport in the BL where the magneto-rotational instability (MRI) is not operating owing to the increasing angular velocity Omega(r) with radius. We will therefore search for an appropriate mechanism and examine its efficiency and implications. Methods. We perform 2D numerical hydrodynamical simulations in a cylindrical coordinate system (r; phi) for a thin, vertically integrated accretion disk around a young star. We employ a realistic equation of state and include both cooling from the disk surfaces and radiation transport in radial and azimuthal direction. The viscosity in the disk is treated by the alpha-model; in the BL there is no viscosity term included. Results. We find that our setup is unstable to the sonic instability which sets in shortly after the simulations have been started. Acoustic waves are generated and traverse the domain, developing weak shocks in the vicinity of the BL. Furthermore, the system undergoes recurrent outbursts where the activity in the disk increases strongly. The instability and the waves do not die out for over 2000 orbits. Conclusions. There is indeed a purely hydrodynamical mechanism that enables AM transport in the BL. It is efficient and wave mediated; however, this renders it a non-local transport method, which means that models of a effective local viscosity like the alpha-viscosity are probably not applicable in the BL. A variety of further implications of the non-local AM transport are discussed.


21. U03653

In this study we present photometric and spectroscopic variation analysis and an orbital period study of a low-mass interacting system OO Aql. Simultaneous solution of the light and radial velocity curves provides us with the determination of a new set of stellar physical parameters for the primary and the secondary companion, M-1 = 1.05(2) M-circle dot, M-2 = 0.89(2) M-circle dot, R-1 = 1.38(2) R-circle dot, R-2 = 1.28(2) R-circle dot, log(L-1/L-circle dot) = 0.258, and log (L-2/L-circle dot) = 0.117, and the separation of the components was determined to be a = 3.333(16) R-circle dot. Newly obtained parameters yield the distance of the system as 136(8) pc. Analyses of themid-eclipse times indicate a period increase of (P/(P) over dot) = 4x10(7) yr that can be interpreted in terms of the mass transfer (dM/dt) = 5 x 10(-8) M-circle dot yr(-1) from the less massive component to the more massive component. Our new solution confirmed that OO Aql is a multiple system in the form of AB + C + D. We found initial astrophysical parameters for the component of the system and its current age to be 8.6 Gyr using a non-conservative stellar evolution model (EV-TWIN code).


22. U03691
Jofre P. et al. Gaia FGK benchmark stars: abundances of alpha and iron-peak elements // Astron. Astrophys. 2015. Vol. 582. P. A81.

Context. In the current era of large spectroscopic surveys of the Milky Way, reference stars for calibrating astrophysical parameters and chemical abundances are of paramount importance. Aims. We determine elemental abundances of Mg, Si, Ca, Sc, Ti, V, Cr, Mn, Co, and Ni for our predefined set of Gaia FGK benchmark stars. Methods. By analysing high-resolution spectra with a high signal-to-noise ratio taken from several archive datasets, we combined results of eight different methods to determine abundances on a line-by-line basis. We performed a detailed homogeneous analysis of the systematic uncertainties, such as differential versus absolute abundance analysis. We also assessed errors that are due to non-local thermal equilibrium and the stellar parameters in our final abundances. Results. Our results are provided by listing final abundances and the different sources of uncertainties, as well as line-by-line and method-by-method abundances. Conclusions. The atmospheric parameters of the Gaia FGK benchmark stars are already being widely used for calibration of several pipelines that are applied to different surveys. With the added reference abundances of ten elements, this set is very suitable for calibrating the chemical abundances obtained by these pipelines.


23. U00918
Larsen A.C. et al. ASTROPHYSICAL REACTION RATES AND THE LOW-ENERGY ENHANCEMENT IN THE gamma STRENGTH // Acta Phys. Pol. B. 2013. Vol. 44, № 3. P. 563–566.

An unexpected enhancement in the gamma-strength function for E (gamma) < 3 MeV for Ti, Sc, V, Fe, and Mo nuclei close to the valley of stability has been discovered at the Oslo Cyclotron Laboratory. Provided that this enhancement is present also in very neutron-rich nuclei, it could give an increase in the neutron-capture rates up to two orders of magnitude. However, it is still an open question whether this structure persists when approaching the neutron drip line. DOI:10.5506/APhysPolB.44.563


24. U03691
Leurini S. et al. Spectroscopically resolved far-IR observations of the massive star-forming region G5.89-0.39 // Astron. Astrophys. 2015. Vol. 584. P. A70.

The secular evolution of an infinitely thin tepid isolated galactic disc made of a finite number of particles is described using the inhomogeneous Balescu-Lenard equation. Assuming that only tightly wound transient spirals are present in the disc, a WKB approximation provides a simple and tractable quadrature for the corresponding drift and diffusion coefficients. It provides insight into the physical processes at work during the secular diffusion of a self-gravitating discrete disc and makes quantitative predictions on the initial variations of the distribution function in action space. When applied to the secular evolution of an isolated stationary self-gravitating Mestel disc, this formalism predicts the initial importance of the corotation resonance in the inner regions of the disc leading to a regime involving radial migration and heating. It predicts in particular the formation of a ridge-like feature in action space, in agreement with simulations, but over-estimates the timescale involved in its appearance. Swing amplification is likely needed to resolve this discrepancy. In astrophysics, the inhomogeneous Balescu-Lenard equation and its WKB limit may also describe the secular diffusion of giant molecular clouds in galactic discs, the secular migration and segregation of planetesimals in proto-planetary discs, or even the long-term evolution of population of stars within the Galactic centre.


25. U03653
Mack C.E. et al. A Cautionary Tale: Marvels Brown Dwarf Candidate Reveals Itself to Be a Very Long Period, Highly Eccentric Spectroscopic Stellar Binary // Astron. J. 2013. Vol. 145, № 5. P. 139.

We report the discovery of a highly eccentric, double-lined spectroscopic binary star system (TYC 3010-1494-1), comprising two solar-type stars that we had initially identified as a single star with a brown dwarf companion. At the moderate resolving power of the MARVELS spectrograph and the spectrographs used for subsequent radial-velocity (RV) measurements (R less than or similar to 30,000), this particular stellar binary mimics a single-lined binary with an RV signal that would be induced by a brown dwarf companion (M sin i similar to 50 M-Jup) to a solar-type primary. At least three properties of this system allow it to masquerade as a single star with a very-low-mass companion: its large eccentricity (e similar to 0.8), its relatively long period (P similar to 238 days), and the approximately perpendicular orientation of the semi-major axis with respect to the line of sight (omega similar to 189 degrees). As a result of these properties, for similar to 95% of the orbit the two sets of stellar spectral lines are completely blended, and the RV measurements based on centroiding on the apparently single-lined spectrum is very well fit by an orbit solution indicative of a brown dwarf companion on a more circular orbit (e similar to 0.3). Only during the similar to 5% of the orbit near periastron passage does the true, double-lined nature and large RV amplitude of similar to 15 km s(-1) reveal itself. The discovery of this binary system is an important lesson for RV surveys searching for substellar companions; at a given resolution and observing cadence, a survey will be susceptible to these kinds of astrophysical false positives for a range of orbital parameters. Finally, for surveys like MARVELS that lack the resolution for a useful line bisector analysis, it is imperative to monitor the peak of the cross-correlation function for suspicious changes in width or shape, so that such false positives can be flagged during the candidate vetting process.


26. U03691
Martin-Domenech R. et al. UV photoprocessing of CO2 ice: a complete quantification of photochemistry and photon-induced desorption processes // Astron. Astrophys. 2015. Vol. 584. P. A14.

Context. Ice mantles that formed on top of dust grains are photoprocessed by the secondary ultraviolet (UV) field in cold and dense molecular clouds. UV photons induce photochemistry and desorption of ice molecules. Experimental simulations dedicated to ice analogs under astrophysically relevant conditions are needed to understand these processes. Aims. We present UV-irradiation experiments of a pure CO2 ice analog. Calibration of the quadrupole mass spectrometer allowed us to quantify the photodesorption of molecules to the gas phase. This information was added to the data provided by the Fourier transform infrared spectrometer on the solid phase to obtain a complete quantitative study of the UV photoprocessing of an ice analog. Methods. Experimental simulations were performed in an ultra-high vacuum chamber. Ice samples were deposited onto an infrared transparent window at 8K and were subsequently irradiated with a microwave-discharged hydrogen flow lamp. After irradiation, ice samples were warmed up until complete sublimation was attained. Results. Photolysis of CO2 molecules initiates a network of photon-induced chemical reactions leading to the formation of CO, CO3, O-2, and O-3. During irradiation, photon-induced desorption of CO and, to a lesser extent, O-2 and CO2 took place through a process called indirect desorption induced by electronic transitions, with maximum photodesorption yields (Y-pd) of similar to 1.2 x 10(-2) molecules incident photon(-1), similar to 9.3 x 10(-4) molecules incident photon(-1), and similar to 1.1 x 10(-4) molecules incident photon(-1), respectively. Conclusions. Calibration of mass spectrometers allows a direct quantification of photodesorption yields instead of the indirect values that were obtained from infrared spectra in most previous works. Supplementary information provided by infrared spectroscopy leads to a complete quantification, and therefore a better understanding, of the processes taking place in UV-irradiated ice mantles.


27. U03691
Moravveji E. et al. Tight asteroseismic constraints on core overshooting and diffusive mixing in the slowly rotating pulsating B8.3V star KIC 10526294 // Astron. Astrophys. 2015. Vol. 580. P. A27.

Context. KIC 10526294 was recently discovered to be a very slowly rotating and slowly pulsating late B-type star. Its 19 consecutive dipole gravity modes constitute a series with almost constant period spacing. This unique collection of identified modes probes the near-core environment of this star and holds the potential to reveal the size and structure of the overshooting zone above the convective core, as well as the mixing properties of the star. Aims. We revisit the asteroseismic modelling of this star with specific emphasis on the properties of the core overshooting, while considering additional diffusive mixing throughout the radiative envelope of the star. Methods. We pursued forward seismic modelling based on adiabatic eigenfrequencies of equilibrium models for eight extensive evolutionary grids tuned to KIC 10526294 by varying the initial mass, metallicity, chemical mixture, and the extent of the overshooting layer on top of the convective core. We examined models for both OP and OPAL opacities and tested the occurrence of extra diffusive mixing throughout the radiative interior. Results. We find a tight mass-metallicity relation within the ranges M is an element of [3.13,3.25] M-circle dot, and Z is an element of [0.014, 0.028]. We deduce that an exponentially decaying diffusive core overshooting prescription describes the seismic data better than a step function formulation and derive a value of f(ov) between 0.017 and 0.018. Moreover, the inclusion of extra diffusive mixing with a value of log D-mix between 1.75 and 2.00 dex (with D-mix in cm(2) s(-1)) improves the goodness-of-fit based on the observed and modelled frequencies by a factor similar to 11 compared to the case where no extra mixing is considered, irrespective of the (M, Z) combination within the allowed seismic range. Conclusions. The inclusion of diffusive mixing in addition to core overshooting is essential to explain the structure in the observed period spacing pattern of this star. Moreover, for the input physics and chemical mixtures we investigated, we deduce that an exponentially decaying prescription for the core overshooting is to be preferred over a step function, regardless of the adopted mixture or choice of opacity tables. Our best models for KIC 10526294 approach the seismic data to a level that they can serve future inversion of its stellar structure.


28. U03691
Nakamura K. et al. r-process nucleosynthesis in the MHD plus neutrino-heated collapsar jet // Astron. Astrophys. 2015. Vol. 582. P. A34.

It has been proposed that the collapsar scenario for long-duration gamma ray bursts is a possible astrophysical site for r-process nucleosynthesis. Here we present r-process nucleosynthesis calculations based upon a model for a MHD+neutrino-heated collapsar jet. We utilize a relativistic magnetohydrodynamic model that includes ray-tracing neutrino transport to describe the development of the black hole accretion disk and the neutrino heating of the funnel region above the black hole. The late time evolution of the collapsar jet is then evolved using axisymmetric special relativistic hydrodynamics. We employ representative test particles to follow the trajectories in density, temperature, entropy, and electron fraction for material flowing from the accretion disk into the jet until they are several thousand km above the black hole. The evolution of nuclear abundances from nucleons to heavy nuclei for ejected test particle trajectories was solved in a large nuclear reaction network as temperatures fall from 9 x 10(9) to 3 x 10(8) K. We show that an r-process-like abundance distribution forms in material ejected in the collapsar jet. The possibility for a signature of collapsar r-process material to be found in metal-poor stars is discussed.


29. U03691
Nielsen M.B. et al. Constraining differential rotation of Sun-like stars from asteroseismic and starspot rotation periods // Astron. Astrophys. 2015. Vol. 582. P. A10.

In previous work, we identified six Sun-like stars observed by Kepler with exceptionally clear asteroseismic signatures of rotation. Here, we show that five of these stars exhibit surface variability suitable for measuring rotation. We compare the rotation periods obtained from light-curve variability with those from asteroseismology in order to further constrain differential rotation. The two rotation measurement methods are found to agree within uncertainties, suggesting that radial differential rotation is weak, as is the case for the Sun. Furthermore, we find significant discrepancies between ages from asteroseismology and from three different gyrochronology relations, implying that stellar age estimation is problematic even for Sun-like stars.


30. U03691
Oksala M.E. et al. An infrared diagnostic for magnetism in hot stars (Research Note) // Astron. Astrophys. 2015. Vol. 578. P. A112.

Magnetospheric observational proxies are used for indirect detection of magnetic fields in hot stars in the X-ray, UV, optical, and radio wavelength ranges. To determine the viability of infrared (IR) hydrogen recombination lines as a magnetic diagnostic for these stars, we have obtained low-resolution (R similar to 1200), near-IR spectra of the known magnetic B2V stars HR 5907 and HR 7355, taken with the Ohio State Infrared Imager/Spectrometer (OSIRIS) attached to the 4.1 m Southern Astrophysical Research (SOAR) Telescope. Both stars show definite variable emission features in IR hydrogen lines of the Brackett series, with similar properties as those found in optical spectra, including the derived location of the detected magnetospheric plasma. These features also have the added advantage of a lowered contribution of stellar flux at these wavelengths, making circumstellar material more easily detectable. IR diagnostics will be useful for the future study of magnetic hot stars, to detect and analyze lower-density environments, and to detect magnetic candidates in areas obscured from UV and optical observations, increasing the number of known magnetic stars to determine basic formation properties and investigate the origin of their magnetic fields.


31. U03691
Pehlivan A., Nilsson H., Hartman H. Laboratory oscillator strengths of Sc I in the near-infrared region for astrophysical applications // Astron. Astrophys. 2015. Vol. 582. P. A98.

Context. Atomic data is crucial for astrophysical investigations. To understand the formation and evolution of stars, we need to analyse their observed spectra. Analysing a spectrum of a star requires information about the properties of atomic lines, such as wavelengths and oscillator strengths. However, atomic data of some elements are scarce, particularly in the infrared region, and this paper is part of an effort to improve the situation on near-IR atomic data. Aims. This paper investigates the spectrum of neutral scandium, Sc I, from laboratory measurements and improves the atomic data of Sc I lines in the infrared region covering lines in R, I, J, and K bands. Especially, we focus on measuring oscillator strengths for Sc I lines connecting the levels with 4p and 4s configurations. Methods. We combined experimental branching fractions with radiative lifetimes from the literature to derive oscillator strengths (f-values). Intensity-calibrated spectra with high spectral resolution were recorded with Fourier transform spectrometer from a hollow cathode discharge lamp. The spectra were used to derive accurate oscillator strengths and wavelengths for Sc I lines, with emphasis on the infrared region. Results. This project provides the first set of experimental Sc I lines in the near-infrared region for accurate spectral analysis of astronomical objects. We derived 63 log(gf) values for the lines between 5300 angstrom and 24 300 angstrom. The uncertainties in the f-values vary from 5% to 20%. The small uncertainties in our values allow for an increased accuracy in astrophysical abundance determinations.


32. U03691
Perri S. et al. Parameter estimation of superdiffusive motion of energetic particles upstream of heliospheric shocks // Astron. Astrophys. 2015. Vol. 578. P. A2.

Context. In-situ spacecraft observations recently suggested that the transport of energetic particles accelerated at heliospheric shocks can be anomalous, i.e. the mean square displacement can grow non-linearly in time. In particular, a new analysis technique has permitted the study of particle transport properties from energetic particle time profiles upstream of interplanetary shocks. Indeed, the time/spatial power laws of the differential intensity upstream of several shocks are indicative of superdiffusion. Aims. A complete determination of the key parameters of superdiffusive transport comprises the power-law index, the superdiffusion coefficient, the related transition scale at which the energetic particle profiles turn to decay as power laws, and the energy spectral index of the shock accelerated particles. Methods. Assuming large-scale spatial homogeneity of the background plasma, the power-law behaviour can been derived from both a ( microscopic) propagator formalism and a ( macroscopic) fractional transport equation. We compare the two approaches and find a relation between the diffusion coefficients used in the two formalisms. Based on the assumption of superdiffusive transport, we quantitatively derive these parameters by studying energetic particle profiles observed by the Ulysses and Voyager 2 spacecraft upstream of shocks in the heliosphere, for which a superdiffusive particle transport has previously been observed. Further, we have jointly studied the electron energy spectra, comparing the values of the spectral indices observed with those predicted by the standard diffusive shock acceleration theory and by a model based on superdiffusive transport. Results. For a number of interplanetary shocks and for the solar wind termination shock, for the first time we obtain the anomalous diffusion constants and the scale at which the probability of particle free paths changes to a power-law. The investigation of the particle energy spectra indicates that a shock acceleration theory based on superdiffusive transport better explains observed spectral index values. Conclusions. This study, together with the analysis of energetic particles upstream of shock waves, allows us to fully determine the transport properties of accelerated particles, even in the case of superdiffusion. This represents a new powerful tool to understand the transport and acceleration processes at astrophysical shocks.


33. U03691
Ramos-Ceja M.E. et al. Constraining the intracluster pressure profile from the thermal SZ power spectrum // Astron. Astrophys. 2015. Vol. 583. P. A111.

The angular power spectrum of the thermal Sunyaev-Zel'dovich (tSZ) effect is highly sensitive to cosmological parameters such as sigma(8) and Omega(m), but its use as a precision cosmological probe is hindered by the astrophysical uncertainties in modeling the gas pressure profile in galaxy groups and clusters. In this paper we assume that the relevant cosmological parameters are accurately known and explore the ability of current and future tSZ power spectrum measurements to constrain the intracluster gas pressure or the evolution of the gas mass fraction, f(gas). We use the CMB bandpower measurements from the South Pole Telescope and a Bayesian Markov chain Monte Carlo (MCMC) method to quantify deviations from the standard, universal gas pressure model. We explore analytical model extensions that bring the predictions for the tSZ power into agreement with experimental data. We find that a steeper pressure profile in the cluster outskirts or an evolving f(gas) have mild-to-severe conflicts with experimental data or simulations. Varying more than one parameter in the pressure model leads to strong degeneracies that cannot be broken with current observational constraints. We use simulated bandpowers from future tSZ survey experiments, in particular a possible 2000 deg(2) CCAT survey, to show that future observations can provide almost an order of magnitude better precision on the same model parameters. This will allow us to break the current parameter degeneracies and place simultaneous constraints on the gas pressure profile and its redshift evolution, for example.


34. U03653
Ribeiro V. a. R.M., Russo P., Cardenas-Avendano A. A Survey of Astronomical Research: A Baseline for Astronomical Development // Astron. J. 2013. Vol. 146, № 6. P. 138.

Measuring scientific development is a difficult task. Different metrics have been put forward to evaluate scientific development; in this paper we explore a metric that uses the number of peer-reviewed, and when available non-peer-reviewed, research articles as an indicator of development in the field of astronomy. We analyzed the available publication record, using the Smithsonian Astrophysical Observatory/NASA Astrophysics Database System, by country affiliation in the time span between 1950 and 2011 for countries with a gross national income of less than 14,365 USD in 2010. This represents 149 countries. We propose that this metric identifies countries in "astronomical development" with a culture of research publishing. We also propose that for a country to develop in astronomy, it should invest in outside expert visits, send its staff abroad to study, and establish a culture of scientific publishing. Furthermore, we propose that this paper may be used as a baseline to measure the success of major international projects, such as the International Year of Astronomy 2009.


35. U03691
Scholz R.-D. et al. Global survey of star clusters in the Milky Way IV. 63 new open clusters detected by proper motions // Astron. Astrophys. 2015. Vol. 581. P. A39.

Context. The global Milky Way Star Clusters (MWSC) survey provided new cluster membership lists and mean cluster parameters for nearly 80% of all previously known Galactic clusters. The MWSC data reduction pipeline involved the catalogue of positions and proper motions (PPMXL) on the International Celestial Reference System (ICRS) and near-infrared photometry from the Two Micron All Sky Survey (2MASS). Aims. In the first extension to the MWSC, photometric filters were applied to the 2MASS catalogue to find new cluster candidates that were subsequently confirmed or rejected by the MWSC pipeline. To further extend the MWSC census, particularly of nearby clusters, we aimed at discovering new clusters by conducting an almost global search in proper motion catalogues as a starting point. Methods. We first selected high-quality samples from the PPMXL and the Fourth US Naval Observatory CCD Astrograph Catalog (UCAC4) for comparison and verification of the proper motions. For 441 circular proper motion bins (radius 15 mas/yr) within +/- 50 mas/yr, the sky outside a thin Galactic plane zone (vertical bar b vertical bar < 5 degrees) was binned in small areas ("sky pixels") of 0.25 x 0.25 deg(2). Sky pixels with enhanced numbers of stars with a certain common proper motion in both catalogues were considered as cluster candidates. After visual inspection of the sky images, we built an automated procedure that combined these representations of the sky for neighbouring proper motion subsamples after a background correction. The 692 compact cluster candidates detected above a threshold that was equivalent to a minimum of 12 to 130 cluster stars in dependence on the Galactic latitude were then cross-checked with known star clusters and clusters of galaxies. New candidates served as input for the MWSC pipeline. Results. About half of our candidates overlapped with known clusters (46 globular and 68 open clusters in the Galaxy, about 150 known clusters of galaxies) or the Magellanic Clouds. About 10% of our candidates are 63 new open clusters confirmed by the MWSC pipeline. They predominantly occupy the two inner Galactic quadrants and have apparent sizes and numbers of highly probable members slightly larger than those of the typically small MWSC clusters, whereas their other parameters (ages, distances, tidal radii) fall in the typical ranges. As we searched for compact clusters, we did not find new very nearby (extended) clusters, and the mean total proper motion of the new 63 clusters is with 6.3 mas/yr similar to the MWSC average (5.5 mas/yr). Only four new clusters have mean proper motions between 10 mas/yr and our observed maximum of about 13 mas/yr.


36. U03691
Sharma B.K. et al. Unified equation of state for neutron stars on a microscopic basis // Astron. Astrophys. 2015. Vol. 584. P. A103.

We derive a new equation of state (EoS) for neutron stars (NS) from the outer crust to the core based on modern microscopic calculations using the Argonne v(18) potential plus three-body forces computed with the Urbana model. To deal with the inhomogeneous structures of matter in the NS crust, we use a recent nuclear energy density functional that is directly based on the same microscopic calculations, and which is able to reproduce the ground-state properties of nuclei along the periodic table. The EoS of the outer crust requires the masses of neutron-rich nuclei, which are obtained through Hartree-Fock-Bogoliubov calculations with the new functional when they are unknown experimentally. To compute the inner crust, Thomas-Fermi calculations in Wigner-Seitz cells are performed with the same functional. Existence of nuclear pasta is predicted in a range of average baryon densities between similar or equal to 0.067 fm(-3) and similar or equal to 0.0825 fm(-3), where the transition to the core takes place. The NS core is computed from the new nuclear EoS assuming non-exotic constituents (core of npe mu matter). In each region of the star, we discuss the comparison of the new EoS with previous EoSs for the complete NS structure, widely used in astrophysical calculations. The new microscopically derived EoS fulfills at the same time a NS maximum mass of 2 M-circle dot with a radius of 10 km, and a 1.5 M-circle dot NS with a radius of 11.6 km.


37. U03691
Skala J. et al. The 3D MHD code GOEMHD3 for astrophysical plasmas with large Reynolds numbers Code description, verification, and computational performance // Astron. Astrophys. 2015. Vol. 580. P. A48.

Context. The numerical simulation of turbulence and flows in almost ideal astrophysical plasmas with large Reynolds numbers motivates the implementation of magnetohydrodynamical (MHD) computer codes with low resistivity. They need to be computationally efficient and scale well with large numbers of CPU cores, allow obtaining a high grid resolution over large simulation domains, and be easily and modularly extensible, for instance, to new initial and boundary conditions. Aims. Our aims are the implementation, optimization, and verification of a computationally efficient, highly scalable, and easily extensible low-dissipative MHD simulation code for the numerical investigation of the dynamics of astrophysical plasmas with large Reynolds numbers in three dimensions (3D). Methods. The new GOEMHD3 code discretizes the ideal part of the MHD equations using a fast and efficient leap-frog scheme that is second-order accurate in space and time and whose initial and boundary conditions can easily be modified. For the investigation of diffusive and dissipative processes the corresponding terms are discretized by a DuFort-Frankel scheme. To always fulfill the Courant-Friedrichs-Lewy stability criterion, the time step of the code is adapted dynamically. Numerically induced local oscillations are suppressed by explicit, externally controlled diffusion terms. Non-equidistant grids are implemented, which enhance the spatial resolution, where needed. GOEMHD3 is parallelized based on the hybrid MPI-OpenMP programing paradigm, adopting a standard two-dimensional domain-decomposition approach. Results. The ideal part of the equation solver is verified by performing numerical tests of the evolution of the well-understood Kelvin-Helmholtz instability and of Orszag-Tang vortices. The accuracy of solving the (resistive) induction equation is tested by simulating the decay of a cylindrical current column. Furthermore, we show that the computational performance of the code scales very efficiently with the number of processors up to tens of thousands of CPU cores. This excellent scalability of the code was obtained by simulating the 3D evolution of the solar corona above an active region (NOAA AR1249) for which GOEMHD3 revealed the energy distribution in the solar atmosphere in response to the energy influx from the chromosphere through the transition region, taking into account the weak Joule current dissipation and viscosity in the almost dissipationless solar corona. Conclusions. The new massively parallel simulation code GOEMHD3 enables efficient and fast simulations of almost ideal astrophysical plasma flows with large Reynolds numbers well resolved and on huge grids covering large domains. Its abilities are verified by comprehensive set of tests of ideal and weakly dissipative plasma phenomena. The high-resolution (2048(3) grid points) simulation of a large part of the solar corona above an observed active region proves the excellent parallel scalability of the code up to more than 30 000 processor cores.


38. U00918
Sperhake U. Black Holes on Supercomputers: Numerical Relativity Applications to Astrophysics and High-Energy Physics // Acta Phys. Pol. B. 2013. Vol. 44, № 12. P. 2463–2536.

We review the state-of-the-art of the numerical modeling of black-hole spacetimes in the framework of General Relativity in four and more space-time dimensions. The latest developments of the applications of these techniques to study black holes in the context of astrophysics, gravitational wave physics and high-energy physics are summarized.


39. U03691
Tercero B. et al. Searching for trans ethyl methyl ether in Orion KL // Astron. Astrophys. 2015. Vol. 582. P. L1.

We report on the tentative detection of trans ethyl methyl ether (tEME), t-CH3CH2OCH3, through the identification of a large number of rotational lines from each one of the spin states of the molecule towards Orion KL. We also search for gauche-trans-n-propanol, Gt-n-CH3CH2CH2OH, an isomer of tEME in the same source. We have identified lines of both species in the IRAM 30 m line survey and in the ALMA Science Verification data. We have obtained ALMA maps to establish the spatial distribution of these species. Whereas tEME mainly arises from the compact ridge component of Orion, Gt-n-propanol appears at the emission peak of ethanol (south hot core). The derived column densities of these species at the location of their emission peaks are <=(4.0 +/- 0.8) x 10(15) cm(-2) and <=(1.0 +/- 0.2) x 10(15) cm(-2) for tEME and Gt-n-propanol, respectively. The rotational temperature is similar to 100 K for both molecules. We also provide maps of CH3OCOH, CH3CH2OCOH, CH3OCH3, CH3OH, and CH3CH2OH to compare the distribution of these organic saturated O-bearing species containing methyl and ethyl groups in this region. Abundance ratios of related species and upper limits to the abundances of non-detected ethers are provided. We derive an abundance ratio N(CH3OCH3)/N(tEME) >= 150 in the compact ridge of Orion.


40. U03691
Thurgood J.O., Tsiklauri D. Self-consistent particle-in-cell simulations of fundamental and harmonic plasma radio emission mechanisms // Astron. Astrophys. 2015. Vol. 584. P. A83.

Aims. The simulation of three-wave interaction based plasma emission, thought to be the underlying mechanism for Type III solar radio bursts, is a challenging task requiring fully-kinetic, multi-dimensional models. This paper aims to resolve a contradiction in past attempts, whereby some studies indicate that no such processes occur. Methods. We self-consistently simulate three-wave based plasma emission through all stages by using 2D, fully kinetic, electromagnetic particle-in-cell simulations of relaxing electron beams using the EPOCH2D code. Results. Here we present the results of two simulations; Run 1 (n(b)/n(0) = 0.0057, v(b)/Lambda v(b) = v(b)/V-e = 16) and Run 2 (n(b)/n(0) = 0.05, v(b)/Delta v(b) = v(b)/V-e = 8), which we find to permit and prohibit plasma emission respectively. We show that the possibility of plasma emission is contingent upon the frequency of the initial electrostatic waves generated by the bump-in-tail instability, and that these waves may be prohibited from participating in the necessary three-wave interactions due to frequency conservation requirements. In resolving this apparent contradiction through a comprehensive analysis, in this paper we present the first self-consistent demonstration of fundamental and harmonic plasma emission from a single-beam system via fully kinetic numerical simulation. We caution against simulating astrophysical radio bursts using unrealistically dense beams (a common approach which reduces run time), as the resulting non-Langmuir characteristics of the initial wave modes significantly suppresses emission. Comparison of our results also indicates that, contrary to the suggestions of previous authors, an alternative plasma emission mechanism based on two counter-propagating beams is unnecessary in an astrophysical context. Finally, we also consider the action of the Weibel instability which generates an electromagnetic beam mode. As this provides a stronger contribution to electromagnetic energy than the emission, we stress that evidence of plasma emission in simulations must disentangle the two contributions and not simply interpret changes in total electromagnetic energy as evidence of plasma emission.


41. U03691
Tkachenko A. Grid search in stellar parameters: a software for spectrum analysis of single stars and binary systems // Astron. Astrophys. 2015. Vol. 581. P. A129.

Context. The currently operating space missions, as well as those that will be launched in the near future, will deliver high-quality data for millions of stellar objects. Since the majority of stellar astrophysical applications still (at least partly) rely on spectroscopic data, an efficient tool for the analysis of medium-to high-resolution spectroscopy is needed. Aims. We aim at developing an efficient software package for the analysis of medium-to high-resolution spectroscopy of single stars and those in binary systems. The major requirements are that the code should have a high performance, represent the state-of-the-art analysis tool, and provide accurate determinations of atmospheric parameters and chemical compositions for different types of stars. Methods. We use the method of atmosphere models and spectrum synthesis, which is one of the most commonly used approaches for the analysis of stellar spectra. Our Grid Search in Stellar Parameters (Gssp) code makes use of the Message Passing Interface (OpenMPI) implementation, which makes it possible to run in parallel mode. The method is first tested on the simulated data and is then applied to the spectra of real stellar objects. Results. The majority of test runs on the simulated data were successful in that we were able to recover the initially assumed sets of atmospheric parameters. We experimentally find the limits in signal-to-noise ratios of the input spectra, below which the final set of parameters is significantly affected by the noise. Application of the gssp package to the spectra of three Kepler stars, KIC 11285625, KIC 6352430, and KIC 4931738, was also largely successful. We found an overall agreement of the final sets of the fundamental parameters with the original studies. For KIC 6352430, we found that dependence of the light dilution factor on wavelength cannot be ignored, as it has a significant impact on the determination of the atmospheric parameters of this binary system. Conclusions. The gssp software package is a compilation of three individual program modules suitable for spectrum analysis of single stars and individual binary components. The code is highly effective and can be used for spectrum analysis of large samples of stars.


42. U03691
Turlione A., Aguilera D.N., Pons J.A. Quiescent thermal emission from neutron stars in low-mass X-ray binaries // Astron. Astrophys. 2015. Vol. 577. P. A5.

Context. We monitored the quiescent thermal emission from neutron stars in low-mass X-ray binaries after active periods of intense activity in X-rays (outbursts). Aims. The theoretical modeling of the thermal relaxation of the neutron star crust may be used to establish constraints on the crust composition and transport properties, depending on the astrophysical scenarios assumed. Methods. We numerically simulated the thermal evolution of the neutron star crust and compared them with inferred surface temperatures for five sources: MXB 1659-29, KS 1731-260, XTE J1701-462, EXO 0748-676 and IGRJ17480-2446. Results. We find that the evolution of MXB 1659-29, KS 1731-260 and EXO0748-676 can be well described within a deep crustal cooling scenario. Conversely, we find that the other two sources can only be explained with models beyond crustal cooling. For the peculiar emission of XTE J1701-462 we propose alternative scenarios such as residual accretion during quiescence, additional heat sources in the outer crust, and/or thermal isolation of the inner crust due to a buried magnetic field. We also explain the very recent reported temperature of IGRJ17480-2446 with an additional heat deposition in the outer crust from shallow sources.


43. U03691
Vaidya B. et al. Astrophysical fluid simulations of thermally ideal gases with non-constant adiabatic index: numerical implementation // Astron. Astrophys. 2015. Vol. 580. P. A110.

Context. An equation of state (EoS) is a relation between thermodynamic state variables and it is essential for closing the set of equations describing a fluid system. Although an ideal EoS with a constant adiabatic index Gamma is the preferred choice owing to its simplistic implementation, many astrophysical fluid simulations may benefit from a more sophisticated treatment that can account for diverse chemical processes. Aims. In the present work we first review the basic thermodynamic principles of a gas mixture in terms of its thermal and caloric EoS by including effects like ionization, dissociation, and temperature dependent degrees of freedom such as molecular vibrations and rotations. The formulation is revisited in the context of plasmas that are either in equilibrium conditions (local thermodynamic- or collisional excitation-equilibria) or described by non-equilibrium chemistry coupled to optically thin radiative cooling. We then present a numerical implementation of thermally ideal gases obeying a more general caloric EoS with non-constant adiabatic index in Godunov-type numerical schemes. Methods. We discuss the necessary modifications to the Riemann solver and to the conversion between total energy and pressure (or vice versa) routinely invoked in Godunov-type schemes. We then present two different approaches for computing the EoS. The first employs root-finder methods and it is best suited for EoS in analytical form. The second is based on lookup tables and interpolation and results in a more computationally efficient approach, although care must be taken to ensure thermodynamic consistency. Results. A number of selected benchmarks demonstrate that the employment of a non-ideal EoS can lead to important differences in the solution when the temperature range is 500-10(4) K where dissociation and ionization occur. The implementation of selected EoS introduces additional computational costs although the employment of lookup table methods (when possible) can significantly reduce the overhead by a factor of similar to 3-4.


44. U03691
Vos J. et al. Testing eccentricity pumping mechanisms to model eccentric long-period sdB binaries with MESA // Astron. Astrophys. 2015. Vol. 579. P. A49.

Context. Hot subdwarf-B stars in long-period binaries are found to be on eccentric orbits, even though current binary-evolution theory predicts these objects to be circularised before the onset of Roche-lobe overflow (RLOF). Aims. We aim to find binary-evolution mechanisms that can explain these eccentric long-period orbits, and reproduce the currently observed period-eccentricity diagram. Methods. Three different processes are considered; tidally-enhanced wind mass-loss, phase-dependent RLOF on eccentric orbits and the interaction between a circumbinary disk and the binary. The binary module of the stellar-evolution code Modules for Experiments in Stellar Astrophysics (MESA) is extended to include the eccentricity-pumping processes. The effects of different input parameters on the final period and eccentricity of a binary-evolution model are tested with MESA. Results. The end products of models with only tidally-enhanced wind mass-loss can indeed be eccentric, but these models need to lose too much mass, and invariably end up with a helium white dwarf that is too light to ignite helium. Within the tested parameter space, no sdBs in eccentric systems are formed. Phase-dependent RLOF can reintroduce eccentricity during RLOF, and could help to populate the short-period part of the period-eccentricity diagram. When phase-dependent RLOF is combined with eccentricity pumping via a circumbinary disk, the higher eccentricities can be reached as well. A remaining problem is that these models favour a distribution of higher eccentricities at lower periods, while the observed systems show the opposite. Conclusions. The models presented here are potentially capable of explaining the period-eccentricity distribution of long-period sdB binaries, but further theoretical work on the physical mechanisms is necessary.


45. U03691
Wang B. et al. Super-Eddington wind scenario for the progenitors of type Ia supernovae: Accreting He-rich matter onto white dwarfs // Astron. Astrophys. 2015. Vol. 584. P. A37.

Context. Supernovae of type Ia (SNe Ia) are believed to be thermonuclear explosions of carbon-oxygen white dwarfs (CO WDs). However, the mass accretion process onto CO WDs is still not completely understood. Aims. In this paper, we study the accretion of He-rich matter onto CO WDs and explore a scenario in which a strong wind forms on the surface of the WD if the total luminosity exceeds the Eddington limit. Methods. Using a stellar evolution code called modules for experiments in stellar astrophysics (MESA), we simulated the He accretion process onto CO WDs for WDs with masses of 0.6-1.35 M-circle dot and various accretion rates of 10(-8)-10(-5) M-circle dot yr(-1). Results. If the contribution of the total luminosity is included when determining the Eddington accretion rate, then a super-Eddington wind could be triggered at relatively lower accretion rates than those of previous studies based on steady-state models. The super-Eddington wind can prevent the WDs with high accretion rates from evolving into red-giant-like He stars. We found that the contributions from thermal energy of the WD are non-negligible, judging by our simulations, even though the nuclear burning energy is the dominating source of luminosity. We also provide the limits of the steady He-burning regime in which the WDs do not lose any accreted matter and increase their mass steadily, and calculated the mass retention efficiency during He layer flashes for various WD masses and accretion rates. These obtained results can be used in future binary population synthesis computations.


46. U03691
Wolff M., Tautz R.C. Cosmic-ray acceleration at collisionless astrophysical shocks using Monte-Carlo simulations // Astron. Astrophys. 2015. Vol. 580. P. A58.

Context. The diffusive shock acceleration mechanism has been widely accepted as the acceleration mechanism for galactic cosmic rays. While self-consistent hybrid simulations have shown how power-law spectra are produced, detailed information on the interplay of diffusive particle motion and the turbulent electromagnetic fields responsible for repeated shock crossings are still elusive. Aims. The framework of test-particle theory is applied to investigate the effect of diffusive shock acceleration by inspecting the obtained cosmic-ray energy spectra. The resulting energy spectra can be obtained this way from the particle motion and, depending on the prescribed turbulence model, the influence of stochastic acceleration through plasma waves can be studied. Methods. A numerical Monte-Carlo simulation code is extended to include collisionless shock waves. This allows one to trace the trajectories of test particle while they are being accelerated. In addition, the diffusion coefficients can be obtained directly from the particle motion, which allows for a detailed understanding of the acceleration process. Results. The classic result of an energy spectrum with E-2 is only reproduced for parallel shocks, while, for all other cases, the energy spectral index is reduced depending on the shock obliqueness. Qualitatively, this can be explained in terms of the diffusion coefficients in the directions that are parallel and perpendicular to the shock front.


47. U03653
Zacharias N., Zacharias M.I. Radio-Optical Reference Frame Link Using the Us Naval Observatory Astrograph and Deep Ccd Imaging // Astron. J. 2014. Vol. 147, № 5. 95

Between 1997 and 2004 several observing runs were conducted, mainly with the CTIO 0.9 m, to image International Celestial Reference Frame (ICRF) counterparts (mostly QSOs) in order to determine accurate optical positions. Contemporary to these deep CCD images, the same fields were observed with the U.S. Naval Observatory astrograph in the same bandpass. They provide accurate positions on the Hipparcos/Tycho-2 system for stars in the 10-16 mag range used as reference stars for the deep CCD imaging data. Here we present final optical position results of 413 sources based on reference stars obtained by dedicated astrograph observations that were reduced following two different procedures. These optical positions are compared to radio very long baseline interferometry positions. The current optical system is not perfectly aligned to the ICRF radio system with rigid body rotation angles of 3-5 mas (=3 sigma level) found between them for all three axes. Furthermore, statistically, the optical-radio position differences are found to exceed the total, combined, known errors in the observations. Systematic errors in the optical reference star positions and physical offsets between the centers of optical and radio emissions are both identified as likely causes. A detrimental, astrophysical, random noise component is postulated to be on about the 10 mas level. If confirmed by future observations, this could severely limit the Gaia to ICRF reference frame alignment accuracy to an error of about 0.5 mas per coordinate axis with the current number of sources envisioned to provide the link. A list of 36 ICRF sources without the detection of an optical counterpart to a limiting magnitude of about R = 22 is provided as well.


48. 006647
Бакланов П.В., Блинников С.И., Мануковский К.В., Надёжин Д.К., Панов И.В., Утробин В.П., Юдин А.В. ДОСТИЖЕНИЯ АСТРОФИЗИКОВ ИТЭФ // Успехи физических наук. 2016. Т. 186. № 8. С. 879-890.

Представлен исторический очерк астрофизических исследований, проводимых в Институте теоретической и экспериментальной физики (ИТЭФ) на протяжении более чем 30 лет. Основное внимание уделено проблематике сверхновых звёзд: начиная с классических работ В.С. Имшенника и Д.К. Надёжина, заложивших основы теории сверхновых, вплоть до современных моделей этих мощнейших звёздных взрывов во вселенной. Кроме того, описаны некоторые исследования в других разделах астрофизики: нуклеосинтез химических элементов, использование сверхновых типа IIn в космологии, модели тёмной материи и т.д. Работа подготовлена к 70-летию ИТЭФ.


49. 008074
Барабанов И.Р., Безруков Л.Б., Вересникова А.В., Гаврилюк Ю.М., Гангапшев А.М., Гришина В.Ю., Гуренцов В.И., Заварзина В.П., Казалов В.В., Крохалева С.Д., Кузьминов В.В., Курлович А.С., Лубсандоржиев Б.К., Лубсандоржиев С.Б., Межох А.К., Моргалюк В.П., Наумов П.Ю., Новикова Г.Я., Петков В.Б., Пшуков А.М. и др. ДЕТЕКТОР БОЛЬШОГО ОБЪЕМА В БАКСАНСКОЙ НЕЙТРИННОЙ ОБСЕРВАТОРИИ ИЯИ РАН ДЛЯ ИССЛЕДОВАНИЯ ПРИРОДНЫХ ПОТОКОВ НЕЙТРИНО ДЛЯ ЦЕЛЕЙ ГЕО- И АСТРОФИЗИКИ // Ядерная физика. 2017. Т. 80. № 3. С. 230-238.

В Баксанской нейтринной обсерватории ИЯИ РАН на Северном Кавказе предлагается создать на глубине, соответствующей 4760 м в. э., нейтринный детектор большого объема на основе жидкого сцинтиллятора с массой мишени 10 кт. Детектор предназначен для регистрации природных потоков нейтрино низкой энергии (до 100 МэВ). В работе рассматриваются потоки нейтрино от различных источников и оценивается ожидаемый эффект в предлагаемом детекторе. Разрабатываемый детектор в Баксанской нейтринной обсерватории будет являться частью мировой сети нейтринных детекторов по изучению природных нейтринных потоков.


50. 008074
Беляев В.С., Батищев П.А., Большаков В.В., Ёлкин К.С., Карабаджак Г.Ф., Ковков Д.В., Матафонов А.П., Райкунов Г.Г., Яхин Р.А., Пикуз С.А., Скобелев И.Ю., Фаенов А.Я., Фортов В.Е., Крайнов В.П., Розанов В.Б. ПЕРСПЕКТИВНЫЕ НАПРАВЛЕНИЯ ИССЛЕДОВАНИЙ В ОБЛАСТИ ЛАБОРАТОРНОЙ АСТРОФИЗИКИ С ИСПОЛЬЗОВАНИЕМ МОЩНЫХ ЛАЗЕРОВ // Ядерная физика. 2013. Т. 76. № 4. С. 441.

Представлены результаты работы по выбору и обоснованию перспективных направлений исследований в области лабораторной астрофизики с использованием мощных лазеров. Эти направления определяются возможностью моделирования в лабораторных условиях проблемных процессов современной астрофизики, таких, как: 1) генерация и эволюция электромагнитных полей в космосе, роль магнитных полей в космосе на разных пространственных масштабах; 2) космические гамма-всплески и релятивистские джеты, механизмы их образования и эволюции; 3) плазменные неустойчивости в космосе и астрофизических объектах, плазменные струи, ударные волны; 4) взрывы сверхновых, механизмы взрыва сверхновых с коллапсирующим ядром; 5) ядерные процессы в астрофизических объектах; 6) космические лучи, механизмы генерации и ускорения до высоких энергий; 7) астрофизические источники рентгеновского излучения. Показано, что использование существующих мощных лазеров с интенсивностью в диапазоне 10 ?10 Вт/см и длительностью импульса 0.1?1 пс и высокоэнергетических лазеров с энергией более 1 кДж и длительностью импульса 1?10 нс позволяет проводить исследования в области лабораторной астрофизики по всем выбранным перспективным направлениям. Представленные результаты экспериментальных исследований лазерной плазмы, полученные с помощью созданной в ЦНИИмаш лазерной установки с уровнем мощности 10 ТВт, показывают возможности и перспективность подобных установок для проведения ряда экспериментов в области лабораторной астрофизики.


51. 008074
Варламов В.В., Ишханов Б.С., Орлин В.Н., Песков Н.Н., Стопани К.А. ФОТОНЕЙТРОННЫЕ РЕАКЦИИ В АСТРОФИЗИКЕ // Ядерная физика. 2014. Т. 77. № 12. С. 1563.

Одной из центральных проблем ядерной астрофизики является понимание природы синтеза химических элементов. Большинство тяжелых элементов, существующих в природе, образуется в звездах в процессах радиационного захвата нейтронов, так называемых - и -процессах, соответственно медленных и быстрых в сравнении с конкурирующими процессами -распада. Вместе с тем известны 35 нейтронно-дефицитных так называемых обойденных -ядер от Se до Hg, которые не могут быть образованы в упомянутых - и -процессах. Их формирование возможно в фотоядерных реакциях ( ), ( ) или ( ). В связи с этим данные по фотонейтронным реакциям играют важную роль в предсказании и описании процеcсов формирования -ядер. В последнее время существенно возрос интерес к определению сечений фотонейтронных реакций в области энергий вблизи порога, представляющей особый интерес с точки зрения астрофизики. Использование современных источников квазимоноэнергетических фотонов, полученных в процессах обратного комптоновского рассеяния лазерного излучения на релятивистских электронах, с одной стороны, позволяет выявить весьма интересные особенности этих сечений типа проявления пигми 1- и 1-резонансов или образования ядер в изомерных состояниях, а с другой - заставляет вернуться к проблеме систематических расхождений данных по сечениям реакций, полученных в экспериментах разного типа. Эти проблемы рассматриваются с использованием данных, полученных в рамках нового экспериментально-теоретического подхода к оценке сечений парциальных фотонейтронных реакций.


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Джилкибаев Ж.А.А.М., Домогацкий Г.В., Суворова О.В. ЧЕРЕНКОВСКИЕ ДЕТЕКТОРЫ В НЕЙТРИННОЙ АСТРОФИЗИКЕ ВЫСОКИХ ЭНЕРГИЙ // Успехи физических наук. 2015. Т. 185. № 5. С. 531-539.

Обсуждаются состояние и перспективы развития крупномасштабных детекторов черенковского излучения в естественных средах — глубоко под водой и во льду. (Байкал, Средиземное море, Антарктида), — ставших в последние десятилетия основным инструментом исследования природных потоков нейтрино высоких энергий. К 110-летию со дня рождения П.А. Черенкова (Научная сессия Отделения физических наук Российской академии наук, 17 декабря 2014 г.)


53. 006647

Представлен обзор полученных за последние несколько лет астрономических данных, которые говорят о том, что массивные первичные чёрные дыры играют гораздо более существенную роль во Вселенной, чем считалось ранее. Речь идет как о современной Вселенной, так и о молодой при красных смещениях порядка 10. Обсуждается предложенная в 1993 г. модель рождения в очень ранней Вселенной тяжёлых и сверхтяжёлых чёрных дыр с логарифмически-нормальным спектром масс, которая естественным образом объясняет факты из жизни Вселенной, не вписывающиеся в стандартные космологию и астрофизику.


54. 008074
КОНФЕРЕНЦИЯ ПО АСТРОФИЗИКЕ Земля и Вселенная. 2018. № 3. С. 81-89.

Определены основные проблемы ядерной астрофизики, которые могут быть исследованы в лабораторных условиях при интенсивности лазерного излучения 10 Вт/см и более: литиевая проблема, проблема определения источников нейтронов при протекании s-процессов образования тяжелых элементов, образование обойденных стабильных p-ядер, ядерные реакции с изотопами, используемыми астрономами для диагностических целей. Приведены результаты экспериментов на установке “Неодим” и даны предложения по дальнейшим исследованиям в этой области.


55. 006647
Крюков П.Г. ФЕМТОСЕКУНДНЫЕ ЛАЗЕРЫ ДЛЯ АСТРОФИЗИКИ // Успехи физических наук. 2015. Т. 185. № 8. С. 817-827.

Лазеры непрерывного действия с пассивной синхронизацией мод обладают уникальной особенностью: они испускают строго периодическую последовательность совершенно одинаковых импульсов фемтосекундной длительности, а спектр их излучения представляет собой гребёнку эквидистантно расположенных узких спектральных линий, интервал между которыми определяется частотой непрерывного следования импульсов. Таким образом, фемтосекундный непрерывный лазер является источником регулярной гребёнки оптических частот (ГОЧ), значения которых можно сопоставить с цезиевым стандартом частоты (эталоном секунды), что предоставило возможность прецизионного измерения частоты в оптическом диапазоне, чрезвычайно важную для создания сверхточных атомных часов, прецизионной спектроскопии и метрологии. Одним из основных применений ГОЧ на основе непрерывных лазеров фемтосекундных импульсов является прецизионное измерение с помощью астрономических спектрометров доплеровских смещений в спектрах звёзд, которые возникают вследствие радиального движения звёзд по отношению к наблюдателю. Для того чтобы обеспечить высокую точность измерений, требуемую для поиска и исследований экзопланет, необходим прецизионный калибратор астрономического спектрометра. Такой калибратор может быть основан на фемтосекундной лазерной гребёнке спектральных линий. Рассматриваются лазерные системы, предназначенные для астрономических исследований, в том числе фемтосекундные лазеры для исследований в космосе. Предполагается, что развитие рассматриваемых методов сделает возможными прямые измерения ускорения расширения Вселенной.


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Моделирование астрофизических течений в рамках классической магнитной гидродинамики нередко наталкивается на значительные затруднения, связанные с большими значениями альвеновской скорости (вплоть до релятивистских). Такие ситуации могут возникать в задачах моделирования магнитосфер планет и звёзд, аккреционных течений в полярах, промежуточных полярах и вблизи нейтронных звёзд. В условиях сильного магнитного поля в плазме может развиваться турбулентность волнового типа. Она может оказывать существенное влияние, приводя к изменению энергетического баланса и сил, определяющих динамику плазмы. Получена замкнутая система уравнений модифицированной магнитной гидродинамики с учётом волновой турбулентности для большого диапазона величин магнитного поля и турбулентной энергии. Течение описывается как сумма усреднённого течения и возмущений, вызванных волновыми пульсациями. В качестве возмущений рассматриваются альвеновские волны со скоростями вплоть до релятивистских значений. Найдены выражения для величины объёмной силы, вязкости и диссипативного нагрева, вызванных турбулентностью. Выполнен анализ уравнений для некоторых предельных случаев. Показано, что предлагаемый подход можно использовать для моделирования широкого класса течений астрофизической плазмы.


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Снытников Н.В. ДЕКОМПОЗИЦИЯ ОБЛАСТИ НА ОСНОВЕ ПРЯМОГО МЕТОДА РЕШЕНИЯ ТРЕХМЕРНОГО УРАВНЕНИЯ ПУАССОНА В НЕСТАЦИОНАРНЫХ ЗАДАЧАХ АСТРОФИЗИКИ // Вычислительные методы и программирование: новые вычислительные технологии. 2015. Т. 16. № 1. С.85-89

Предложен новый параллельный алгоритм для решения трехмерного уравнения Пуассона в контексте нестационарных задач астрофизики. Алгоритм основан на декомпозиции трехмерной области по двум направлениям, в применении прямого метода решения задачи Дирихле в каждой подобласти и в комбинации метода сопряжения подобластей для двумерного экранированного уравнения Пуассона с методом разделения переменных. Тестовые эксперименты проводились на суперкомпьютерах Межведомственного суперкомпьютерного центра (МСКЦ) и Сибирского суперкомпьютерного центра (ССКЦ).


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