The hottest horizontal-branch stars in $\mathsf{\omega}$ Centauri. Late hot flasher vs. helium enrichment
نویسندگان
چکیده
منابع مشابه
The Hottest Horizontal - Branch Stars in ω Centauri – Late Hot Flasher vs . Helium Enrichment ⋆
Context. UV observations of some massive globular clusters uncovered a significant population of very hot stars below the hot end of the horizontal branch (HB), the so-called blue hook stars. This feature might be explained either as results of the late hot flasher scenario where stars experience the helium flash while on the white dwarf cooling curve or by the progeny of the helium-enriched su...
متن کاملSpectroscopic Analyses of the “Blue Hook” Stars in ω Centauri: A Test of the Late Hot Flasher Scenario
ω Cen contains the largest population of very hot horizontal branch (HB) stars known in a globular cluster. Recent UV observations (Whitney et al. 1998; D’Cruz et al. 2000) show a significant population of hot stars below the zero-age horizontal branch (“blue hook” stars), which cannot be explained by canonical stellar evolution. Stars which suffer unusually large mass loss on the red giant bra...
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 کاملRotation of Hot Horizontal Branch Stars in Galactic Globular Clusters
We present high resolution UVES+VLT spectroscopic observations of 61 stars in the extended blue horizontal branches of the Galactic globular clusters NGC 1904 (M79), NGC 2808, NGC 6093 (M80), and NGC 7078 M15). Our data reveal for the first time the presence in NGC 1904 of a sizable population of fast (vsini ≥ 20 km/s) horizontal branch (HB) rotators, confined to the cool end of the EHB, simila...
متن کاملObservations of the Hot Horizontal-Branch Stars in the Metal-Rich Bulge Globular Cluster NGC 6388 Indications of Helium Enrichment and a Lesson in Crowded Field Spectroscopy
The metal-rich bulge globular cluster NGC 6388 shows a distinct blue horizontal-branch tail in its colour-magnitude diagram (Rich et al. 1997) and is thus a strong case of the well-known 2nd Parameter Problem. In addition, its horizontal branch (HB) shows an upward tilt toward bluer colours, which cannot be explained by canonical evolutionary models. Several noncanonical scenarios have been pro...
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: Astronomy & Astrophysics
سال: 2007
ISSN: 0004-6361,1432-0746
DOI: 10.1051/0004-6361:20078509