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Spectral indices are useful tools for quantifying the strengths of features in moderate-resolution spectra and relating them to intrinsic stellar parameters. This paper focuses on the 4300AA CH G-band, a classic example of a feature interpreted through use of spectral indices. G-band index definitions, as applied to globular clusters of different metallicity, abound in the literature, and transformations between the various systems, or comparisons between different authors work, are difficult and not always useful. We present a method for formulating an optimized G-band index, using a large grid of synthetic spectra. To make our new index a reliable measure of carbon abundance, we minimize its dependence on [N/Fe] and simultaneously maximize its sensitivity to [C/Fe]. We present a definition for the new index S2(CH), along with estimates of the errors inherent in using it for [C/Fe] determination, and conclude that it is valid for use with spectra of bright globular cluster red giants over a large range in [Fe/H], [C/Fe], and [N/Fe].
We have obtained high-res, high S/N ratio CCD echelle spectra of 10 bright red giants in 3 GCs (47Tuc, NGC6752 and NGC6397) roughly spanning the range of metallicities of the galactic GC system; they reveal no evidence of star to star variation of [F
We report chemical abundances obtained by SDSS-III/APOGEE for giant stars in five globular clusters located within 2.2 kpc of the Galactic centre. We detect the presence of multiple stellar populations in four of those clusters (NGC 6553, NGC 6528, T
The behaviour of the Delta nu =2 CO bands around 2.3 micron was examined by comparing observed and synthetic spectra in stars in globular clusters of different metallicity. Changes in the 12C/13C isotopic ratio and the carbon abundances were invest
NGC 6522 is a moderately metal-poor bulge globular cluster ([Fe/H]$sim$$-$1.0), and it is a well-studied representative among a number of moderately metal-poor blue horizontal branch clusters located in the bulge. The NGC 6522 abundance pattern can g
Thermohaline mixing is a favoured mechanism for the so-called extra mixing on the red giant branch of low-mass stars. The mixing is triggered by the molecular weight inversion created above the hydrogen shell during first dredge-up when helium-3 burn