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 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...
متن کاملFull evolutionary models for PG 1159 stars . Implications for the helium - rich O ( He ) stars .
Aims. We present full evolutionary calculations appropriate to post-AGB PG1159 stars for a wide range of stellar masses. Methods. We take into account the complete evolutionary stages of PG1159 progenitors starting from the Zero Age Main Sequence. We consider the two kinds of Born Again Scenarios, the very late thermal pulse (VLTP) and the late thermal pulse (LTP), that give rise to hydrogen-de...
متن کاملO(he) Stars
Spectral analyses of H-deficient post-AGB stars have shown that a small group of four extremely hot objects exists which have almost pure He absorption-line spectra in the optical. These are classified as O(He) stars. For their evolution there are two scenarios: They could be the long-sought hot successors of RCrB stars, which have not been identified up to now. If this turns out to be true, th...
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ژورنال
عنوان ژورنال: Symposium - International Astronomical Union
سال: 1991
ISSN: 0074-1809
DOI: 10.1017/s0074180900227356