Stellar scale

Virtually all of the galactic mass is in the form of a singularity at the galactic center. The bulge, disk, and halo of stars represent an infinitesimal fine mist of stellar-scale objects within the galaxy s Schwarzschild radius". 

Because of their enormous energy output and mass ejection, the SSCM proposes that supernovae are stellar scale analogues of highly excited atoms undergoing radioactive decay events". 

Classical astronomy is largely concerned with the classification of stars without regard to the details of their constituent plasmas (63). Only more recently have sateUite-bome observations begun to yield detailed data from the high temperature regions of other stellar plasmas. Cosmic plasmas of diverse size scales have been discussed (64). 

Abstract. The Milky Way harbours two disks that appear distinct concerning scale-heights, kinematics, and elemental abundance patterns. Recent years have seen a surge of studies of the elemental abundance trends in the disks using high resolution spectroscopy. Here I will review and discuss the currently available data. Special focus will also be put on how we define stars to be members of either disk, and how current models of galaxy formation favour that thick disks are formed from several accreted bodies. The ability for the stellar abundance trends to test such predictions are discussed. 

It is important to remember at this point that the metallicities for the two samples of stars plotted in Fig. 1 were derived using exactly the same techniques, and are thus both in the same scale (see [19]). Also, in the CORALIE planet search sample we have never used the stellar [Fe/H] as a criterion to chose a star. The comparison shown in Fig. 1 is thus not sample-biased. Finally, and as shown in [21], the precision in the derived radial-velocities is not a strong function of the stellar metallicity. The observed increasing frequency of planets with increasing [Fe/H] is thus also not due to any bias in the planet searches. 

The aim of this paper is to re-analyze the stars studied by AP04 with a technique which discriminates a-enhanced (Non Solar Scaled Abundance, NSSA) stars from those with Solar Scaled Abundances (SSA) without requiring any assumption about the stellar atmospheric parameter values. 

Fig. 1. (left panel) [Eu/Fe] as a function of [Fe/H]. Gray-scale indicates predicted distribution of stellar fraction. The r-process site is assumed to be SNe of 8 — IOMq. The average stellar distributions are indicated by thick-solid lines with the 50% (solid lines) and 90% confidence intervals (thin-solid lines). The current observational data are given by large circles, with other previous data (small circles). 

Fig. 4.13. Evidence for the presence of 5 2 per cent 6Li in the warm halo subdwarf HD 84937 with [Fe/H] = -2.4, 7 = 6090 K. The left panel shows synthesized profiles for 0, 5 and 10 per cent 6Li with the observational points on an absolute wavelength scale in the rest frame of the stellar photosphere. The right panel shows the central wavelengths of the doublets of each isotope and a deviation plot for the three hypotheses on 6Li/7Li. Adapted from Smith, Lambert and Nissen (1993).

Fig. 8.16. Upper panel stellar values of [O/H] plotted against age for disk stars, after Nissen, Edvardsson and Gustafsson (1985). Curves show theoretical values of [O/H] and [Fe/H] from an analytical model. The lower panel shows the same curves plotted on a linear scale, where log0 = [O/H] and log / = [Fe/H]. After Pagel (1989a).

Fig. 8.29. Europium to iron ratios plotted against metallicity [Fe/H] according to the model of supernova-induced star formation, after Tsujimoto, Shigeyama and Yoshii (1999). Grey scales represent predicted stellar surface densities in the ([Fe/H],[Eu/Fe]) plane convolved with a Gaussian with o = 0.2dex for Eu/Fe and 0.15 dex for Fe/H, and symbols show observational data from various authors. The inset shows the unconvolved predictions.

The measurements of isotopic anomalies in meteorites has contributed greatly to the understanding of mixing processes and time scales in the formation of the solar system as well as strong constraints on presolar stellar evolution but it also left unanswered questions and revealed new complexities which are discussed here. 

The presence of short-lived nuclides like Ca and Al imply a very short time scale between stellar nucleosynthesis and the formation of planetary bodies. To accommodate this time constraint, it is tempting to try to include some of the short-lived nuclide production... 

Fig. 3.3. Theoretical Hertzsprung-Russell diagram. The right-hand scale shows in absolute bolometric magnitude what the left-hand scale expresses as the logarithm of the intrinsic luminosity in units of the solar intrinsic luminosity (Lq = 4 x 10 erg s ). On the horizontal axis, the logarithm of the effective temperature, i.e. the temperature of the equivalent blackbody, is put into correspondence with the spectral type of the star, as determined by the observer. This temperature-luminosity diagram shows the lifelines of the stars as strands combed out like hair across the graph. With a suitable interpretation, i.e. viewed through the explanatory machinery of nuclear physics, it opens the way to an understanding of stellar evolution and its twin science of nucleosynthesis. (Courtesy of Andre Maeder and co-workers.)...

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