Evidence for Flash Mixing in He-rich sdB Stars
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 ...
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The core helium-flash in low-mass stars with extreme mass loss occurs after the tip of the RGB, when the H-rich envelope is very thin. The low efficiency of the H-shell source enables the He-flash driven convective zone to penetrate H-rich layers and trigger a thermonuclear runaway, resulting in a subsequent surface enrichment with He and C. In this work we present the first full computations o...
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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 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 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: Astrophysics and Space Science
سال: 2004
ISSN: 0004-640X
DOI: 10.1023/b:astr.0000044345.85262.dd