Chemical composition of eclipsing binaries: a new approach to the helium-to-metal enrichment ratio     

Ignasi Ribas  Carme Jordi  Jordi Torra  Álvaro Giménez 《Monthly notices of the Royal Astronomical Society》2000,313(1):99-111

The chemical enrichment law Y ( Z ) is studied by using detached double-lined eclipsing binaries with accurate absolute dimensions and effective temperatures. A sample of 50 suitable systems was collected from the literature, and their effective temperatures were carefully re-determined. The chemical composition of each of the systems was obtained by comparison with stellar evolutionary models, under the assumption that they should fit an isochrone to the observed properties of the components. Evolutionary models covering a wide grid in Z and Y were adopted for our study. An algorithm was developed for searching the best-fitting chemical composition (and the age) for the systems, based on the minimization of a χ ² function. The errors (and biases) of these parameters were estimated by means of Monte Carlo simulations, with special care put on the correlations existing between the errors of both components. In order to check the physical consistency of the results, we compared our metallicity values with empirical determinations, obtaining excellent coherence. The independently derived Z and Y values yielded a determination of the chemical enrichment law via weighted linear least-squares fit. Our value of the slope, Δ Y /Δ Z =2.2±0.8, is in good agreement with recent results, but it has a smaller formal error and it is free of systematic effects. Linear extrapolation of the enrichment law to zero metals leads to an estimation of the primordial helium abundance of Y _p=0.225±0.013, possibly affected by systematics in the effective temperature determination.  相似文献   

Diversity dynamics of the Late Cenozoic rodent community from south‐western Kansas: the influence of historical processes on community structure          下载免费PDF全文

ROBERT A. MARTIN  PABLO PELÁEZ‐CAMPOMANES 《第四纪科学杂志》2014,29(3):221-231

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Early Carboniferous blueschist facies metamorphism in metapelites of the West Sudetes (Northern Saxothuringian Domain,Bohemian Massif)     

E. ŽÁČKOVÁ  J. KONOPÁSEK  P. JEŘÁBEK  F. FINGER  J. KOŠLER 《Journal of Metamorphic Geology》2010,28(4):361-379

The metamorphic evolution of micaschists in the north‐eastern part of the Saxothuringian Domain in the Central European Variscides is characterized by the early high‐pressure M1 assemblage with chloritoid in cores of large garnet porphyroblasts and a Grt–Chl–Phe–Qtz ± Pg M2 assemblage in the matrix. Minerals of the M1–M2 stage were overprinted by the low‐pressure M3 assemblage Ab–Chl–Ms–Qtz ± Ep. Samples with the best‐preserved M1–M2 mineralogy mostly appear in domains dominated by the earlier D1 deformation phase and are only weakly affected by subsequent D2 overprint. Thermodynamic modelling suggests that mineral assemblages record peak‐pressure conditions of ≥18–19 kbar at 460–520 °C (M1) followed by isothermal decompression 10.5–13.5 kbar (M2) and final decompression to <8.5 kbar and <480 °C (M3). The calculated peak P–T conditions indicate a high‐pressure/low‐temperature apparent thermal gradient of ～7–7.5 °C km^?1. Laser ablation inductively coupled plasma mass spectrometry isotopic dating and electron microprobe chemical dating of monazite from the M1–M2 mineral assemblages give ages of 330 ± 10 and 328 ± 6 Ma, respectively, which are interpreted as the timing of a peak pressure to early decompression stage. The observed metamorphic record and timing of metamorphism in the studied metapelites show striking similarities with the evolution of the central and south‐western parts of the Saxothuringian Domain and suggest a common tectonic evolution along the entire eastern flank of the Saxothuringian Domain during the Devonian–Carboniferous periods.  相似文献   

Identification of magnetic minerals related to hydrocarbon authigenesis in venezuelan oil fields using an alternative decomposition of isothermal remanence curves     

Milagrosa Aldana  Vincenzo Costanzo-Álvarez  Luis Gómez  Carlos González  Marisel Díaz  Pedro Silva  Myriam Rada 《Studia Geophysica et Geodaetica》2011,55(2):343-358

In this work we try to better characterise the shallow magnetic signature of hydrocarbon microseepage in oil fields from eastern and western Venezuela. To get a better insight of the processes involved, we attempt to find out the main magnetic phases responsible for the observed oil-related shallow magnetic anomalies. In this way, a new and alternative numerical approach to decompose Isothermal Remagnetization (IRM) curves is introduced. The method is based on a Direct Signal Analysis (DSA) of the IRM curve in order to identify the number and type of magnetic components. Representative wells from western (La Victoria) and eastern (San Joaquín) Venezuelan fields are studied. The DSA approach, together with rock magnetic experimental results, indicates that in the well from western Venezuela the main magnetic mineralogy associated to hydrocarbon microseepage is magnetite. Conversely, in the well from eastern Venezuela, these MS anomalies are mainly caused by the presence of Fe-sulphides (i.e. greigite). These results support the hypothesis of two different authigenic processes. For the well at the western field, we propose that a net electron transfer from the organic matter, degraded by hydrocarbon gas leakage, should occur precipitating Fe(II) magnetic minerals (e.g. magnetite). On the other hand, in the well of the eastern field, high concentrations of H2S at shallow levels, might allow the formation of secondary Fe-sulphides.  相似文献   

Climate change related land use problems in protected wetlands: a study in a seriously affected Hungarian area     

Ákos Malatinszky  Szilvia Ádám  Eszter Falusi  Dénes Saláta  Károly Penksza 《Climatic change》2013,118(3-4):671-682

Land managers of wetlands face various challenges emerging from climate change. Exploration of these problems is a prerequisite to developing adaptive management of vulnerable areas. Central and Eastern European countries are highly vulnerable to climate change. The Balaton Uplands National Park, an attractive tourist destination with natural values of high national and community importance, has suffered the greatest extremities in precipitation in Hungary during 2010 and 2011. After identification of stakeholder groups, private landowners and land managers as being most likely affected by climate change were interviewed in the national park. A compilation of the most important land use problems that already have influence on the management of protected wetlands was listed. Land managers connect several problems to weather extremities and long-term changes, but take practically no actions in favor of mitigation or adaptation, or strengthening resilience. As there is strong evidence that wet habitats are becoming more sensitive and vulnerable, land managers have to adapt their objectives, strategies and measures to changing climate and be involved in the process of adapting the management measures of protected areas, especially wetlands, to probable effects of climate change.  相似文献   

Ibvs and the long-term monitoring of behaviour of variable stars     

L. SZABADOS  K. OLÁH 《Experimental Astronomy》1994,5(1-2):9-12

Roles of the Information Bulletin on Variable Stars (IBVS) in servicing some of the information needs of observers of variable stars are briefly summarized.  相似文献   

On the nature of high luminosity ULIRGs     

Josefa Masegosa  Isabel MÁrquez 《Astrophysics and Space Science》2003,284(2):483-486

We present the preliminary results for a sample of 21 high luminosity ULIRGs (L_IR > 10^12.3 L⊙), selected from the 1Jy sample. Based on R band imaging we have performed an analysis of their morphologies. The main result obtained is that about half of the host galaxies are represented by spheroids and in the other half an exponential disk has been detected or they show still trace of a merging process going on. Regarding the relation between morphology and nuclear activity it seems that more advanced mergers appear in the most active galaxies. Hence the data support the evolutionary scheme proposed by Sanders 15 years ago that ULIRGs can be the earliest precursors of optical QSOs. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Long-Term Evolution of FU Ori-Type Stars at Infrared Wavelengths     

Ágnes Kóspál  Péter Ábrahám  Mária Kun  Szilárd Csizmadia  Eva Verdugo 《Astrophysics and Space Science》2004,292(1-4):547-551

We investigated the brightness evolution of 5 FU Ori systems in the 1–200 μm wavelength range using observations from the Infrared Space Observatory, 2MASS and MSX data. The SEDs were compared with earlier ones derived from the IRAS photometry and ground-based observations around the epoch 1983. In three cases no difference was seen, in one object the near- and mid-infrared part of the spectrum became fainter by a factor of 2, and in the fifth case a marginal fading was observed. We study in detail the case of V1057 Cyg.  相似文献   

Scientific and engineering studies, the flexural bar transducer     

Henriquez  T. 《Oceanic Engineering, IEEE Journal of》1987,12(3):537-537

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THERMAP: a mid-infrared spectro-imager for space missions to small bodies in the inner solar system     

O. Groussin  J. Licandro  J. Helbert  J. L. Reynaud  P. Levacher  M. Reyes García-Talavera  V. Alí-Lagoa  P. E. Blanc  E. Brageot  B. Davidsson  M. Delbó  M. Deleuze  A. Delsanti  J. J. Diaz Garcia  K. Dohlen  D. Ferrand  S. F. Green  L. Jorda  E. Joven Álvarez  J. Knollenberg  E. Kührt  P. Lamy  E. Lellouch  J. Le Merrer  B. Marty  G. Mas  C. Rossin  B. Rozitis  J. Sunshine  P. Vernazza  S. Vives 《Experimental Astronomy》2016,41(1-2):95-115

We present THERMAP, a mid-infrared spectro-imager for space missions to small bodies in the inner solar system, developed in the framework of the MarcoPolo-R asteroid sample return mission. THERMAP is very well suited to characterize the surface thermal environment of a NEO and to map its surface composition. The instrument has two channels, one for imaging and one for spectroscopy: it is both a thermal camera with full 2D imaging capabilities and a slit spectrometer. THERMAP takes advantage of the recent technological developments of uncooled microbolometer arrays, sensitive in the mid-infrared spectral range. THERMAP can acquire thermal images (8–18 μm) of the surface and perform absolute temperature measurements with a precision better than 3.5 K above 200 K. THERMAP can acquire mid-infrared spectra (8–16 μm) of the surface with a spectral resolution Δλ of 0.3 μm. For surface temperatures above 350 K, spectra have a signal-to-noise ratio >60 in the spectral range 9–13 μm where most emission features occur.  相似文献