A Study of the Abundance of Low-Z Elements in the Sun During its Whole Predicted Life     

M. H. Talafha  M. A. Al-Wardat  N. M. Ershaidat 《Astrophysical Bulletin》2018,73(2):235-240

The study of the chemical composition of stars and galaxies is a key topic for understanding their origin and evolution. In this study, we present the results of the calculation of solar abundances of the isotopes ¹H, ⁴He, ¹²C, ¹⁴N, ¹⁵O, ¹⁶O, ¹⁷O, and ¹⁸O during the four phases of the solar life: hydrogen burning, onset of rapid growth and red giant, helium burning and helium exhaustion. The open source package “NucNet Tools” from the Webnucleo Group in Clemson University, SC, USA was used for this purpose. The results for all isotopes are listed in tables for future use. Abundances found, globally, agree fairly well with those predicted in the literature. Results obtained for the last two phases have no equivalents elsewhere.  相似文献   

New constraints on granulite facies metamorphism and melt production in the Lewisian Complex,northwest Scotland          下载免费PDF全文

Yves Feisel  Richard W. White  Richard M. Palin  Tim E. Johnson 《Journal of Metamorphic Geology》2018,36(6):799-819

In this study, we investigate the metamorphic history of the Assynt and Gruinard blocks of the Archean Lewisian Complex, northwest Scotland, which are considered by some to represent discrete crustal terranes. For samples of mafic and intermediate rocks, phase diagrams were constructed in the Na₂O–CaO–K₂O–FeO–MgO–Al₂O₃–SiO₂–H₂O–TiO₂–O₂ (NCKFMASHTO) system using whole‐rock compositions. Our results indicate that all samples equilibrated at similar peak metamorphic conditions of ~8–10 kbar and ~900–1,000°C, consistent with field evidence for in situ partial melting and the classic interpretation of the central region of the Lewisian Complex as representing a single crustal block. Melt‐reintegration modelling was employed in order to estimate probable protolith compositions. Phase equilibria calculated for these modelled undepleted precursors match well with those determined for a subsolidus amphibolite from Gairloch in the southern region of the Lewisian Complex. Both subsolidus lithologies exhibit similar phase relations and potential melt fertility, with both expected to produce orthopyroxene‐bearing hornblende granulites, with or without garnet, at the conditions inferred for the Badcallian metamorphic peak. For fully hydrated protoliths, prograde melting is predicted to first occur at ~620°C and ~9.5 kbar, with up to 45% partial melt predicted to form at peak conditions in a closed‐system environment. Partial melts calculated for both compositions between 610 and 1,050°C are mostly trondhjemitic. Although the melt‐reintegrated granulite is predicted to produce more potassic (granitic) melts at ~700–900°C, the modelled melts are consistent with the measured compositions of felsic sheets from the central region Lewisian Complex.  相似文献   

Design Experience of a Demonstrator Descent Vehicle Introducing Aeroelastic Deployable Structural Elements to Space Engineering     

O. M. Alifanov  A. L. Medvedskiy  V. V. Terentyev  D. V. Lyskov 《Solar System Research》2018,52(7):590-596

The development project of a prototype demonstrator for a descent vehicle and the possibilities of descent from orbit using aero-elastic braking devices deployable in space and in the atmosphere is considered. The project was carried out jointly by the Lavochkin Scientific Production Association and the Moscow Aviation Institute teams in 2013–2015. The results are evaluated for both the project itself and the cooperation of the two organizations.  相似文献   

Radiosounding of the High-Latitude Ionosphere with the <Emphasis Type="Italic">Arktika-M</Emphasis> Hydrometeorological Complex     

N. P. Danilkin  S. V. Zhuravlev  N. G. Kotonaeva  V. B. Lapshin  I. V. Romanov  M. Y. Filippov  E. N. Khotenko  G. A. Zhbankov 《Solar System Research》2018,52(7):684-690

The satellite ionosondes in highly elliptical orbits are proposed to be used for the task of continuous monitoring of the Arctic ionosphere. The monitoring scheme with the ionosonde location aboard the Arktika-M satellites is presented. The calculations of the vertical topside and transionospheric sounding using the SIMP1 ionospheric model are performed, which show the feasibility of continuous monitoring.  相似文献   

Mineralogy and temperature of crater Haulani on Ceres          下载免费PDF全文

F. Tosi  F. G. Carrozzo  A. Raponi  M. C. De Sanctis  G. Thangjam  F. Zambon  M. Ciarniello  A. Nathues  M. T. Capria  E. Rognini  E. Ammannito  M. Hoffmann  K. Krohn  A. Longobardo  E. Palomba  C. M. Pieters  K. Stephan  C. A. Raymond  C. T. Russell 《Meteoritics & planetary science》2018,53(9):1902-1924

We investigate the region of crater Haulani on Ceres with an emphasis on mineralogy as inferred from data obtained by Dawn's Visible InfraRed mapping spectrometer (VIR), combined with multispectral image products from the Dawn Framing Camera (FC) so as to enable a clear correlation with specific geologic features. Haulani, which is one of the youngest craters on Ceres, exhibits a peculiar “blue” visible to near‐infrared spectral slope, and has distinct color properties as seen in multispectral composite images. In this paper, we investigate a number of spectral indices: reflectance; spectral slopes; abundance of Mg‐bearing and NH₄‐bearing phyllosilicates; nature and abundance of carbonates, which are diagnostic of the overall crater mineralogy; plus a temperature map that highlights the major thermal anomaly found on Ceres. In addition, for the first time we quantify the abundances of several spectral endmembers by using VIR data obtained at the highest pixel resolution (~0.1 km). The overall picture we get from all these evidences, in particular the abundance of Na‐ and hydrous Na‐carbonates at specific locations, confirms the young age of Haulani from a mineralogical viewpoint, and suggests that the dehydration of Na‐carbonates in the anhydrous form Na₂CO₃ may be still ongoing.  相似文献   

Steric Level Fluctuations and Deep Convection in the Labrador and Irminger Seas     

Belonenko  T. V.  Fedorov  A. M. 《Izvestiya Atmospheric and Oceanic Physics》2018,54(9):1039-1049

Izvestiya, Atmospheric and Oceanic Physics - The paper considers steric level fluctuations in the northern Atlantic Ocean. We use a method that combines AVISO altimetry and GRACE gravity...  相似文献   

Dark energy cosmological models with cosmic string     

T. Vinutha  V. U. M. Rao  Bekele Getaneh  Molla Mengesha 《Astrophysics and Space Science》2018,363(9):188

In this paper we have studied the anisotropic Kantowski-Sachs, locally rotationally symmetric (LRS) Bianchi type-I and LRS Bianchi type-III geometries filled with dark energy and one dimensional cosmic string in the Saez-Ballester theory of gravitation. To get physically valid solution we take hybrid expansion law of the average scale factor which is a product of power and exponential type of functions that results in time dependent deceleration parameter (\(q\)). The equation of state parameter of dark energy (\(\omega _{\mathit{de}}\)) has been discussed and we have observed that for the three models it crosses the phantom divide line (\(\omega _{\mathit{de}} = -1\)) and shows quintom like behavior. The density of dark energy (\(\rho _{\mathit{de}}\)) is an increasing function of redshift and remains positive throughout the evolution of the universe for the three models. Moreover in Kantowski-Sachs and LRS Bianchi type-I geometries the dark energy density dominates the string tension density (\(\lambda \)) and proper density (\(\rho \)) throughout the evolution of the universe. The physical and geometrical aspects of the statefinder parameters (\(r,s\)), squared speed of sound (\(v_{s}^{2} \)) and \(\omega _{\mathit{de}}\)–\(\omega ^{\prime }_{\mathit{de}}\) plane are also discussed.  相似文献   

Determination of Supermassive Black Hole Spins Based on the Standard Shakura–Sunyaev Accretion Disk Model and Polarimetric Observations     

V.?L.?Afanasiev  Yu.N.?GnedinEmail author  M.Yu.?Piotrovich  S.?D.?Buliga  T.?M.?Natsvlishvili 《Astronomy Letters》2018,44(6):362-369

Based on spectropolarimetry for 47 type 1 active galactic nuclei observed with the 6-m BTA telescope, we have estimated the spins of the supermassive black holes at the centers of these galaxies. We have determined the spins based on the standard Shakura–Sunyaev accretion disk model. About 70% of the investigated active galactic nuclei are shown to have Kerr supermassive black holes with a dimensionless spin greater than 0.9.  相似文献   

Higher-dimensional perfect fluid collapse in $$ gravity     

M. Sharif  Atiq Anwar 《Astrophysics and Space Science》2018,363(6):123

In this paper, we analyze higher-dimensional spherical perfect fluid collapse in \(f(R,T)\) theory for minimally coupled models. We use Darmois junction conditions by taking Lemaître-Tolman-Bondi geometry as an interior region and Schwarzschild metric as an exterior spacetime. The solution of field equations is obtained for constant scalar curvature. We determine mass in two regions of the collapsing object and discuss the formation of apparent horizons. We conclude that modified curvature term tends to slow down the collapse rate.  相似文献   

Landau damping of dust acoustic waves in the presence of hybrid nonthermal nonextensive electrons     

W. F. El-Taibany  N. A. Zedan  R. M. Taha 《Astrophysics and Space Science》2018,363(6):129

Based on the kinetic theory, Landau damping of dust acoustic waves (DAWs) propagating in a dusty plasma composed of hybrid nonthermal nonextensive distributed electrons, Maxwellian distributed ions and negatively charged dust grains is investigated using Vlasov-Poisson’s equations. The characteristics of the DAWs Landau damping are discussed. It is found that the wave frequency increases by decreasing (increasing) the value of nonextensive (nonthermal) parameter, \(q\) (\(\alpha \)). It is recognized that \(\alpha \) plays a significant role in observing damping or growing DAW oscillations. For small values of \(\alpha \), damping modes have been observed until reaching a certain value of \(\alpha \) at which \(\omega _{i}\) vanishes, then a growing mode appears in the case of superextensive electrons. However, only damping DAW modes are observed in case of subextensive electrons. The present study is useful in the space situations where such distribution exists.  相似文献