An impact-melt origin for lithology A of martian meteorite Elephant Moraine A79001

Abstract— Mixing models using major and trace elements show that the bulk composition of lithology A (xenocryst-bearing magnesian basalt) of Elephant Moraine A79001 (EETA79001) can be reasonably approximated as a simple mixture of ～44% EETA79001 lithology B (ferroan basalt) and ～56% of Allan Hills A77005 (ALHA7705) light lithology (incompatible element-poor lherzolite). Micro-instrumental neutron activation analysis (INAA) data on xenocryst-free groundmass samples of lithology A show that about 20–25% of the melt phase could be dissolved lherzolite. The bulk and groundmass samples of lithology A have excesses in Au, which indicates either meteoritic contamination or addition by some unknown martian geochemical process. Previous workers have suggested that lithology A was formed by either assimilation of cumulates (like ALHA77005), by a basalt (like lithology B), or by mixing of basaltic and lherzolitic magmas. The former scenario is energetically improbable and unlikely to explain the normal Fe/Mg zonation in lithology A groundmass pyroxenes, whereas the latter scenario is unlikely to satisfy the constraints of the mixing model indicating the ultramafic component is poor in incompatible elements. We suggest rather that EETA79001 lithology A is an impact melt composed dominantly of basalt like lithology B and lherzolitic cumulates like the trace-element-poor fraction of ALHA77005 or Y-793605. This model can satisfy the energetic, petrologic, and geochemical constraints imposed by the samples. If EETA79001 lithology A is an impact melt, this would have considerable consequences for current models of martian petrologic evolution. It would call into question the generally accepted age of magmatism of martian basalts and preclude the use of lithology A groundmass as a primary martian basalt composition in experimental studies. Regardless, the latter is required because lithology A groundmass is a hybrid composition.     

A substructure analysis of the A3558 cluster complex

The 'algorithm driven by the density estimate for the identification of clusters' ( DEDICA ) is applied to the A3558 cluster complex in order to find substructures. This complex, located at the centre of the Shapley Concentration supercluster, is a chain formed by the ACO clusters A3556, A3558 and A3562 and the two poor clusters SC 1327-312 and SC 1329-313. We find a large number of clumps, indicating that strong dynamical processes are active. In particular, it is necessary to use a fully three-dimensional sample (i.e. using the galaxy velocity as third coordinate) in order also to recover the clumps superimposed along the line of sight. Even though a large number of detected substructures was already found in a previous analysis, this method is more efficient and faster when compared with a wide battery of tests, and permits the direct estimate of the detection significance. Almost all subclusters previously detected by the wavelet analyses found in the literature are recognized by DEDICA . On the basis of the substructure analysis, we also briefly discuss the origin of the A3558 complex by comparing two hypotheses: (i) the structure is a cluster–cluster collision seen just after the first core–core encounter; or (ii) this complex is the result of a series of incoherent group–group and cluster–group mergings, focused in that region by the presence of the surrounding supercluster. We studied the fraction of blue galaxies in the detected substructures and found that the bluest groups reside between A3562 and A3558, i.e. in the expected position for the scenario of cluster–cluster collision.     

Radio properties of the Shapley Concentration – IV.The A3528 cluster complex

We report and discuss the results of a 22-cm radio survey carried out with the Australia Telescope Compact Array (ATCA) covering the A3528 complex, a chain formed by the merging ACO clusters A3528–A3530–A3532 , located in the central region of the Shapley Concentration. Simultaneous 13-cm observations are also presented. Our final catalogue includes a total of 106 radio sources above the flux density limit of 0.8 mJy. By cross-correlation with optical and spectroscopic catalogues we found 32 optical counterparts, nine of them belonging to the A3528 complex.
We explored the effects of cluster mergers on the radio emission properties of radio galaxies by means of the radio luminosity function (RLF) and radio source counts. We found that the radio source counts are consistent with the background counts, as already found for the A3558 complex. The RLF for this complex is consistent, in both shape and normalization, with the general cluster luminosity function for early-type galaxies derived by Ledlow & Owen. This result is different from the one we obtained for the A3558 merging complex, the RLF of which is significantly lower than that derived by Ledlow & Owen.
We propose that the different stage of the merger is responsible for the different RLFs in the two cluster complexes in the core of the Shapley Concentration. The early stage of merger for the A3528 complex, proposed by many authors, may not yet have affected the radio properties of cluster galaxies, while in the more much advanced merger in the A3558 region we actually see the effects of this process on the radio emission.     

The Skewness of a Solar Cycle as a Precursor of the Amplitude of the Next

As a precursor for predicting the maximum amplitude of the coming solar cycle, the skewness of the previous cycle proposed by Ramaswamy (1977) is revisited. The reliability of the prediction method is improved by separating odd and even cycles. A first method is proposed on the basis of calculated skewness. In that case, the prediction is available at the end of the previous cycle. A possibility to anticipate the availability of the skewness by about one year is pointed out. A second method, adding prediction of the skewness itself is studied. The statistical reliability is lower than in the first case, but the prediction of a cycle maximum is available at the maximum of the previous cycle.     

The dying accretion and jet in a powerful radio galaxy of Hercules A

Hercules A(Her A) is one of a rare class of dying and transition-type objects, which has a pair of giant, powerful radio lobes and a weak radio core. We reduce and analyze the radio data of Her A that were observed by the Expanded Very Large Array(EVLA) during 2010-2011 at C band. The intensity distribution is very smooth along the edge of the lobe front and the intensity also sharply decreases at the edge, which supports that magnetic fields may play an important role in radio lobes. The spectrum of the weak core is very steep and the core flux becomes weaker by about ten percent when compared to what was observed twenty years ago, which suggest that the central engine is still dying quickly. Her A deviates a lot from the relation between [O III] luminosity and low-frequency 178 MHz luminosity(LO III-L178 MHz) as defined by other FR I/II sources. However, when only radio core emission is considered, it roughly follows an LO III-L178 MHzcorrelation. This result supports that the black-hole accretion and large-scale jet in Her A did not evolve simultaneously, and indicates that although the large-scale jet is still powerful, the accretion and inner jet have changed into an inactive state. Based on the estimated Bondi accretion rate, we model the spectrum of Her A with a radiatively inefficient accretion flow and jet model.     

On the periodicity hypothesis of the ages of large impact craters

An analysis is made of the periodicity hypothesis of the ages of large craters, based on the compilation by Grieve with the addition of recently identified craters. A method earlier proposed by Broadbent is used to derive a period, and the significance of the derived period is tested by a Monte Carlo experiment. In accordance with the result of Stothers, the ages of large craters  ( D >30 km)  are shown to exhibit a period close to 37.5 Myr. Monte Carlo experiments show, however, that the derived period is far from being statistically significant. A subset of crater data earlier adopted by Napier for the purpose of similar investigation is also tested, and it is shown that they also exhibit a similar period at an almost identical level of confidence. A brief discussion is made of the relation between the derived period and that associated with faunal mass extinctions.     

The Galactic Center: a laboratory for AGN?

Summary. This paper reviews the physical state of stars and Interstellar Matter in the Galactic Bulge (radius kpc from the dynamical center of the Galaxy), in the Nuclear Bulge (kpc) and in the Sgr A Radio and GMC Complex, i.e. the central \,pc of our Galaxy. The Galactic Bulge is devoid of cold Interstellar Matter and consists mainly of old stars, while the Nuclear Bulge accounts for of the mass of all of the Interstellar Matter in the Galaxy. A similar ratio holds for the formation rate of medium and high mass stars in Bulge and Disk. The metal abundance of the Interstellar Matter in the Galactic Bulge is found to be . The H-to-CO conversion factors to be applied to molecular gas in the Central Region are by factors 3 (Arimoto et al. 1996) to 10 (Sodroski et al. 1995) lower than in the solar vicinity. Hence, most H masses derived for the Central Region appear to be considerably overestimated. The Nuclear Bulge is pervaded by a thermal plasma (K) which is responsible for the diffuse free-free emission. Lyman continuum photon and dust IR luminosity of the Nuclear Bulge again account for of the respective total luminosities of the Galaxy. Magnetic fields in the Nuclear Bulge are strong (up to mG) as compared with the Galactic Disk (a few tens of G). The field lines are oriented parallel to the galactic plane inside giant molecular clouds and perpendicular to the plane in the intercloud medium. The compact source Sgr A* is close to or at the dynamical center of the Galaxy. Its radio spectrum with a high frequency cut-off at GHz, a low frequency turnover at GHz and a flux density dependence in between can be explained by synchrotron emission from quasi-monoenergetic relativistic electrons. Due to an extinction between Sun and Galactic Center corresponding to , an intrinsic weakness of this source in the near infrared, and a strong background emission from warm dust there are only upper limits available for the flux density of Sgr A* in the far, mid and near infrared and X-ray regime. The size of Sgr A* in the radio regime is cm, its dereddened K-band flux density is mJy, its luminosity has upper limits of (if radiation comes from an Accretion Disk) and (if black-body radiation from an object with a single temperature of K is assumed). If anyone of the soft X-ray sources detected by ROSAT actually coincides with Sgr A*, its X-ray luminosity would be less than a few . With a dark mass of Sgr A* is the best candidate for a starving black hole, although there are no observational indications for the presence of a (Standard) Accretion Disk. While the radio/IR spectrum of Sgr A* is purely nonthermal, the spectrum integrated over the central parsec resembles that of a Seyfert galaxy. Sgr A* is embedded in the Hii region Sgr A West with part of the ionized gas forming a minispiral. Sgr A West is surrounded by the Circum Nuclear Disk, an irregular shaped assembly of molecular gas which extends from pc and rotates around the Galactic Center with an estimated dynamical time scale of \,yr. The total luminosity of of the central parsec is due to the radiation of early-type stars of which have now been directly identified as luminous blue supergiants. It is still debated, however, if these stars can also account for all of the ionization of Sgr A West. In addition, the central parsec contains red giants, AGB stars, and a few super giants of which the brightest are now identified by direct imaging. These stars – together with a few million low mass main sequence stars – account for the bulk of the 2.2\,m emission. The spatial distributions of the three stellar populations in the central pc are remarkably different. Sgr A* is – along the line-of-sight – presumably located close to the center of the Hii region Sgr A West, which in turn is located in front of the extended (pc) synchrotron source Sgr A East, which appears to be the remnant of a gigantic explosion (of the order of the energy of a single supernova explosion) which took place yr ago inside the GMC Sgr A East Core. X-ray observations show within pc a pervasive hot (keV) plasma of expansion age of yr. Both phenomena – as well as the formation of the Circum Nuclear Disk – may have the same origin. Influx of material is observed within the Nuclear Bulge on all distance scales. In the Nuclear Bulge (pc) as well as in the Circum Nuclear Disk (pc) inflow towards the Galactic Center occurs primarily in the galactic plane and amounts to a few . The accretion rate into the central Black Hole, deduced from the luminosity of Sgr A*, however, appears to be lower by at least five orders of magnitude (assuming standard disk accretion). But in an equilibrium state only part of the infalling mass which is not accreted by the Black Hole can be consumed by star formation. A mass inflow rate varying with time is a more natural explanation. Comparing the physical state of the Center of our Galaxy with that of Active Galactic Nuclei derived from observations and modelling, we find that most of the basic characteristics of an AGN are also present in the Galactic Center. Lacking are, however, both the evidence for a standard Accretion Disk and a hard UV spectrum with accompanying high excitation emission lines in the Galactic Center which are characteristic for AGN. The luminosity of the central parsec, , amounts to only of the total luminosity of the Galaxy of . Seen from a distance of M31 (kpc) with an angular resolution of (corresponding to a linear size of pc) the Center of our Galaxy would appear as a mildly active nucleus with some starburst activity and would probably be classified as a weak Seyfert galaxy. The synchrotron spectrum of Sgr A*, however, would be completely masked by reprocessed stellar light (i.e. free-free and dust emission). Received: October 21, 1996     

A sample of E+A galaxy candidates in the Second Data Release of LAMOST Survey

A sample of 70 E+A galaxies is selected from 37 206 galaxies in the second data release of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST). This sample is selected according to the criteria for E+A galaxies defined by Goto, and each of these objects is further visually identified. In this sample, most objects are low redshift E+A galaxies with z 0.25, and are located in an area of the sky with high Galactic latitude and magnitude from 14 to 18 mag in the g, r and i bands. A stellar population analysis of the whole sample indicates that the E+A galaxies are characterized by both young and old stellar populations(SPs), and the metalrich SPs have relatively higher contributions than the metal-poor ones. Additionally, a morphological classification of these objects is performed based on images taken from the Sloan Digital Sky Survey.     

Forward modeling of the coronal response to reconnection in an X-ray bright point

We use MDI magnetic field observations and the theory of reconnection through a separator to constrain a numerical simulation of an X-ray bright point observed in EUV by TRACE. A gasdynamic model is employed to describe the corona and transition region in the bright point loop. Nonlocal effects such as opacity and ambipolar diffusion are important to the transition region; these effects are approximated locally by modification of the radiative loss and thermal conduction. A straightforward comparison of measured light curves versus those generated by the simulation shows that the reconnection model is unable to account for the observations. Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1005205807984     

Existence of the solution of Szebehely's equation in three dimensions using a two-parametric family of orbits

The three-dimensional inverse problem is investigated. A quasi-linear system of partial differential equations is derived for the determination of the potential. The solution of this system is studied by a method of differential geometry. A necessary condition for the solution is derived and the determination of the potential is reduced to algebraic equations written in vectorial form. A few examples are also given.     

Petrology and shock history of the first depleted-like poikilitic shergottite Asuka 12325

Asuka (A) 12325 is the first poikilitic shergottite having a depleted pattern in light rare earth elements (REE). Compared with known poikilitic shergottites, A 12325 has smaller but more abundant pyroxene oikocrysts with remarkable Fe-rich pigeonite rims, indicating that A 12325 cooled relatively faster at a shallower part of the crust. The redox condition (logfO₂ = IW + 0.6-IW + 1.7) and Fe-rich chemical compositions of each mineral in A 12325 are close to enriched shergottites. The intermediate shergottites could not form by a simple mixing between parent magmas of A 12325 and enriched shergottites. Although A 12325 contains various high-pressure minerals such as majorite and ringwoodite, plagioclase is only partly maskelynitized. Therefore, the maximum shock pressure may be within 17–22 GPa. Thermal conduction and ringwoodite growth calculation around a shock vein revealed that the shock dwell time of A 12325 is at least 40 ms. The weaker shock pressure and longer shock dwell time in A 12325 may be attained by an impact event similar to those of nakhlites and Northwest Africa (NWA) 8159. Such a weak shock ejection event may be as common on Mars as a severe shock event recorded in shergottites. Alteration of sulfide observed in A 12325 may imply the presence of magmatic fluid in its reservoir on Mars. A 12325 expands a chemical variety of Martian rocks and has a unique shock history among poikilitic shergottites while A 12325 also implies that poikilitic shergottites are common rocks on Mars regardless of their sources.     

Steady-state double layer structures in the interstellar medium

A one-dimensional, self consistent theoretical model is constructed for double layers in a thermodynamically nonequilibrium astrophysical plasma. A steady state is maintained by an asymmetry in the fluxes from both sides. The range of possible values of the parameters is determined.     

Steady-state drift-dominated modulation models for galactic cosmic rays

A number of steady-state drift-dominated modulation models has been developed by the Potchefstroom modulation group. In this review a selection of these models is discussed and briefly compared. A short overview of the relevant drift theory incorporated into the models is also given.     

Evidence of type II and type IV solar radio emission from a common flare-induced shock wave

A solar radio outburst is described in which a moving type IV burst is observed to break up into several components. A close association is found to exist between this source and a type II burst which occurred during the same period and detailed analysis indicates that both bursts were excited by a common shock wave ejected from the flare region.     

MAGNETISM IN METEORITES

We present here a somewhat simplified overview of the subject of magnetism in meteorites. A glossary of magnetism terminology is included, followed by discussion of the various techniques used for magnetism studies in meteorites. The generalized results from use of these techniques by workers in the field is described. A brief critical analysis is offered.     

Formation of the prelunar accretion disk

According to the single-impact hypothesis for forming the Moon, the angular momentum needed for the present Earth-Moon system can be imparted to the proto-Earth by a collision with a body having one-tenth of the mass or more. The collision must vaporize a large amount of rock which must stay in the form of vapor after expanding in density by a factor of several, so that pressure gradients can accelerate significant amounts of the matter into orbital motion about the proto-Earth. A successful theory must put considerably more than a lunar mass into orbit, having considerably more angular momentum than is needed to assemble a lunar mass in orbit at 3 Earth radii. Such a collision has been simulated by a particular form of a particle-in-cell representation of hydrodynamics and 78 cases have been run representing variations in a variety of parameters. A significant fraction of the cases were successful in creating a satisfactory prelunar accretion disk. A fairly common characteristic of these cases was the presence of an excess velocity in the collision (above that of a parabolic orbit), implying that the projectile involved in the collision existed in an Earth-crossing orbit of significant ellipticity. A majority of the mass of the prelunar accretion disk is contributed by the projectile.     

Features of Kamiokande-II,IMB, and Baksan observations and their interpretation in a two-component model for the signal

We consider the time, angular, and energy distributions of SN 1987A events and discuss the quality of their agreement with the expectations. A global interpretation is made by considering a simple model based on the standard scenario for the explosion. Despite the contrasting and confusing indications, a straightforward fit to the data provides a result that does not contradict but rather supports the expectations. The calculated electron antineutrino flux is applied to predict the relic neutrino signal. The article was translated by the authors.     

Injected spectrum for TeV-γ-ray emission from the galactic center

The detection of very high energy γ-ray emission from the Galactic center has been reported by four independent groups. One of these γ-ray sources, the 10TeV γ-ray radiation reported by HESS, has been suggested as having a hadronic origin when relativistic protons are injected into and interact with the dense ambient gas. Assuming that such relativistic protons required by the hadronic model come from the tidal disruption of a star by the massive black hole of Sgr A*, we explore the spectrum of the relativistic protons. In the calculations, we investigate cases where different types of stars are tidally disrupted by the black hole of Sgr A*, and we consider that different diffusion mechanisms are used for the propagation of protons. The initial energy distribution of the injected spectrum of protons is assumed to follow a power-law with an exponential cut-off, and we derive the different indices of the injected spectra for the tidal disruption of different types of stars. For the best fit to the spectrum of photons detected by HESS, the spectral index of the injected relativistic protons is about 2.05 when a red giant is tidally disrupted by the black hole of Sgr A* and the diffusion mechanism is the Effective Confinement of Protons.