Evolutionary model

Massive stars play an important role in numerous astrophysical contexts that range from the understanding of starburst environments to the chemical evolution in the early Universe. It is therefore crucial that their evolution be fully and consistently understood. A variety of observations of hot stars reveal discrepancies with the standard evolutionary models (see [1] for review) He and N excesses have been observed in O and B main sequence stars and large depletions of B accompanied by N enhancements are seen in B stars and A-F supergiants [2,3,4,5], All of these suggest the presence of excess-mixing, and have led to the development of a new generation of evolutionary models which incorporate rotation (full reviews in [1], [6], [7]). 

Abstract. We present metallicities for 487 red giants in the Carina dwarf spheroidal (dSph) galaxy that were obtained from FLAMES low-resolution Ca triplet (CaT) spectroscopy. We find a mean [Fe/H] of —1.91dex with an intrinsic dispersion of 0.25 dex, whereas the full spread in metallicities is at least one dex. The analysis of the radial distribution of metallicities reveals that an excess of metal poor stars resides in a region of larger axis distances. These results can constrain evolutionary models and are discussed in the context of chemical evolution in the Carina dSph. 

The chemical analysis has revealed that rather low C/O ratios are found in metal-poor extragalactic carbon stars, as found for galactic carbon stars of the solar vicinity. Furthermore, the three analyzed stars show similar s-elements enhancements [ls/Fe]=0.8-1.3 and [hs/Fe]=l.l-1.7. This leads to new constraints for evolutionary models. For instance, the derived C/O and 13C/12C ratios are lower than model predictions at low metallicity. On the contrary, theoretical predictions of neutrons exposures for the production of the s-elements are compatible with observations (see Fig. 1). Finally, from their known distances, we have estimated the luminosities and masses of the three stars. It results that SMC-B30 and Sgr-C3 are most probably intrinsic carbon stars while Sgr-Cl could be extrinsic. 

Figure 9.3 Stacey and Kramers two-stage evolutionary model for lead isotopes.

Mealey, L. (1995). The sociobiology of sociopathy An integrated evolutionary model. Behavioral and Brain Sciences, 18, 523-599. 

SEXUAL BEHAVIOURS IN MELANESIAN SOCIETIES—EVOLUTIONARY MODELS ... 

An Evolutionary Model for Competence Stimulating Peptide Diversity 312... 

Stars are suns of varying masses, at different stages in their evolution, as our models will show. Some like to design protoype cars or aeroplanes, others wedding dresses, whilst we astral physicists make evolutionary models of stars. 

The story of matter can be read in the evolutionary models fashioned by physicists, astronomers and mathematicians working in unison. Models of stars allow us to determine their mass and their age on the basis of their colour and brightness. But these paper stars, for all their equations, must forever be confronted with real ones. 

The whole art in the study of galactic evolution is to put forward a model that relates to available data, taking their volume and accuracy into account. Consequently, the evolutionary model must itself be conceived in an evolutionary way. 

In summary, both experimental evidence and the evolutionary model suggest that the manipulation of NP pathways will often produce rmexpected changes in NP composition. Such manipulation will be predictably rmpredictable. But can this unpredictability be compensated for by a more thorough study of the new NP composition ... 

The establishment of plant integrated defenses involves the preferential evolutionary retention and production of those SCs exerting synergistic toxic effects and is possible only if a diversification of secondary metabolism in a given plant has previously occurred. This preliminary diversification of secondary metabolism could be mediated via the classical reciprocal co-evolutionary interactions between a host plant and its major pests, as predicted by the chemical arms race model (Beren-baum and Zangerl, 1996). The PICD hypothesis is consequently not an exclusive evolutionary hypothesis because it is compatible with and dependent on other evolutionary processes. The contribution of the PICD hypothesis is to provide both a functional explanation for the diversity of SCs within plants (Romeo et al, 1996) and a reconciliation between different evolutionary models. 

The evolutionary track followed by the center and the temperature profiles against density are shown by the solid lines in Figure 2. The numerals attached to the lines denote the time before the onset of the flash in units of 10 yr. The center does not reach the NCO ignition curve before the 3a reaction ignites at the site of the maximum temperature. The NCO reaction does not change the existing evolutionary models, as was pointed out by Spulak (1980), except that a considerable amount of 80 is produced in the central region. 

The luminosity of HD 50896 was determined to log (L/L ) =5.3 (model A), or less in the case of a smaller distance (cf. Table 1). A complrison with recent evolutionary calculations by Maeder and Meynet (1987) indicates an actual mass of about 10 M (case A) from the (extrapolated) mass-luminosity relation for WR stars. Bu unfortunately, stars of this luminosity do not become WR stars, according to these evolutionary models, since the corresponding tracks (e.g. for an initial mass of 20 M ) never return to the blue side of the HR diagram. 

These parameters define an entirely unremarkable blue supergiant. Conventional wisdom had it that Supemovae of Type n occur either in red supeigiants, or perhaps, in the Wolf-Rayet phase of evolution. The central problem for the evolutionary models is therefore, how can the moment of core collapse be contrived to occur in a blue supergiant star There have already been many attempts made to address this question, and from these it is apparent that the main sequence mass must have been in the range 15-20 M . These models teach us that the end-point of evolution is... 

An important constraint in the evolutionary models is that they should correctly describe the observed ratio of red to blue supergiants in the LMC (Wood and Faulkner Maeder Miyaji and Saio, all this conference). Many models without mass loss are unsuccessful in this, since they fail to evolve to the red supergiant phase at all (Amett, Hillebrandt et al.). However, this problem is code dependent, and others do evolve to the red and then return (Woosley et al. Wood and Faulkner Woosley, this conference). 

Comparison between the presupernova evolutionary model, hydrodynamical models and the observations imposes several interesting constraints on Menv and E, i.e., on the presupernova mass loss history, the explosion mechanism, and material mixing before and after the explosion. These are summarized as follows ... 

Another constraint on Menv is obtained from the presupernova evolutionary model where the star evolves from the blue to the red when the mass of the hydrogen-rich envelope significantly decreases and comes back from the red to the blue if the helium abundance is sufficiently enhanced by mass loss and mixing (Saio, Kato, and Nomoto 1988). The observed N/C ratio, which is 40 times the solar ratio (Panagia 1988), is consistent with Menv 7 - 11 M0. 

Ideally, the evolutionary models for the precursor of SN 1987 A should account for both the SN... 

The development methodology establishes detailed discrete work products, by phases and events, and by associated activities. The computer systems development approach must be consistent with the selected SLC the most common development methodologies are the Waterfall Model, the Incremental Development Model, the Evolutionary Model, the Object Oriented approach, and the Spiral Model. Sample SLC activities and work products are detailed in Appendix E. 

Remote measurements of environmental parameters are often characterized by sets of rows that have highly unstable properties. In this case using methods like that above or other methods of traditional statistics becomes impossible. The method of evolutionary modeling makes it possible under conditions of unavoidable instability to retrieve true estimates of environmental characteristics. This method consists in successive selection of models according to indicators of the reflective quality of these models of the process under study. The model resulting from this selection is assumed to accurately represent the object of monitoring and is used to calculate the necessary characteristics. Various problem-oriented realizations of this method and the necessary computer procedures are described in Bukatova et al. (1991). 

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