He-rich and He-poor populations in RGB stars. Results on a sample of 19 globular clusters
نویسندگان
چکیده
منابع مشابه
Properties of He - rich stars
We present an abundance analysis of light elements in the most massive chemically peculiar (CP) stars, He-rich stars. The analysis is based on both low and high-resolution observations collected at ESO, La Silla, Chile in the optical region and includes 6 standard and 21 He-rich stars. Light element abundances display a diverse pattern from under-solar up to above-solar values. Carbon is found ...
متن کاملASTROPHYSICS Properties of He - rich stars
We present a study of helium rich atmospheres in the interval He/H 0.1–1.0 as derived from fully consistent model computations for effective temperature (from 15000K up to 32000K) and surface gravity (log g=3.5 and 4.0). Also the basic diagnostic tools are re-examined, particularly, broad-band UBV and intermediate photometric systems, hydrogen line profiles, continuum fluxes and helium equivale...
متن کاملNa - O Anticorrelation and HB . IV . Detection of He - rich and He - poor stellar populations in the globular cluster NGC 6218 ⋆
We used the multifiber spectrograph FLAMES on the ESO Very Large Telescope UT2 to derive atmospheric parameters, metallicities and abundances of O and Na for 79 red giant stars in the Galactic globular cluster NGC 6218 (M 12). We analyzed stars in the magnitude range from about 1 mag below the bump to the tip of the Red Giant Branch. The average metallicity we derive is [Fe/H]=−1.31 ± 0.004 ± 0...
متن کاملFormation of the Galactic globular clusters with He-rich stars in low-mass halos virialized at high redshift
Recent observations have reported that the Galactic globular clusters (GCs) with unusually extended horizontal-branch (EHB) morphologies show a significantly lower velocity dispersion compared with that of the entire Galactic GC system. We consider that the observed distinctive kinematics of GCs with EHB has valuable information on the formation epochs of GCs and accordingly discuss this observ...
متن کاملASTRONOMY AND ASTROPHYSICS Properties of He - rich stars I . Their
A determination of the surface gravity and an abundance analysis of helium in a sample of 17He-rich and 5 normal, reference stars is presented. These results are derived from low resolution CCD spectra, but each star was measured at least 6 times in order to obtain a significant average spectrum for the spectroscopic variables. The helium abundances derived from the models used are very close t...
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ژورنال
عنوان ژورنال: Proceedings of the International Astronomical Union
سال: 2009
ISSN: 1743-9213,1743-9221
DOI: 10.1017/s1743921310004023