منابع مشابه
Horizontal Branch Stellar Evolution
I review aspects of the evolution of horizontal branch (HB) stars. The defining characteristic of this, the core He-burning phase of evolution for M < Mflash ∼ 2.2M⊙, is a spread in observed colour amongst HB stars within the (almost) chemically homogeneous, isochronous populations found in Galactic globular clusters. The inference is that the stars within a given cluster must have undergone va...
متن کاملEvolution versus Pulsation along the Horizontal Branch of M15
The horizontal-branch evolutionary tracks of Lee and Demarque (LD) are combined with the period/meandensity law of pulsation theory in an attempt to account for the observed periods and relative luminosities of 62 RR Lyrae stars in the extreme metal-poor globular cluster/MI5. These tests were performed for a number of assumed values for the mean luminosity of the M15 RR Lyrae sample and for dif...
متن کاملGravonuclear Instabilities in Post-Horizontal-Branch Stars
We investigate the gravonuclear instabilities reported by Bono et al. (1997a,b) during the onset of helium-shell burning at the end of the horizontal-branch (HB) phase. These instabilities are characterized by relaxation oscillations within the helium shell which lead to loops in the evolutionary tracks. We find the occurrence of these instabilities depends critically on how the breathing pulse...
متن کاملCalibrating horizontal-branch stars with Hipparcos
Parallaxes from the Hipparcos satellite allow for the first time to calibrate parameters of horizontal-branch (HB) like stars based on geometric distances. We present absolute magnitudes and luminosities for 8 such stars. Using Teff and log g values available from the literature, we also can calculate the mass of the HB stars. We find an average value ofMHB = 0.38 ±0.07 M for stars with 7500< T...
متن کاملRadiative Levitation in Hot Horizontal Branch Stars
There is now considerable evidence that horizontal branch (HB) stars hotter than about 11,500 K experience an enormous enhancement of their photospheric iron abundance due to radiative levitation. In globular clusters, the photospheric iron abundance can reach values of [Fe/H] ∼ +0.3, or up to two orders of magnitude higher than the cluster iron abundance. Model atmospheres which take into acco...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: International Astronomical Union Colloquium
سال: 1989
ISSN: 0252-9211
DOI: 10.1017/s0252921100011477