Related papers: Surface pollution of main-sequence stars through e…
The unveiled main-sequence splitting in omega Centauri as well as NGC 2808 suggests that matter highly-enriched in He (in terms of its mass fraction Y~0.4) was produced and made the color of some main-sequence stars bluer in these globular…
[Abbreviated] We have investigated the color-magnitude diagram of Omega Centauri and find that the blue main sequence (bMS) can be reproduced only by models that have a of helium abundance in the range Y=0.35-$0.40. To explain the faint…
In response to the proposed high helium content stars as an explanation for the double main sequence observed in Omega Centauri, we investigated the consequences of such stars elsewhere on the color-magnitude diagram. We concentrated on the…
Recent observational studies of $\omega$ Centauri by {\it Hubble Space Telescope} have discovered a double main sequence in the color magnitude diagrams (CMDs) of its stellar populations. The stellar population with the blue main sequence…
Recent, high precision photometry of Omega Centauri, the biggest Galactic globular cluster, has been obtained with Hubble Space Telescope. The color magnitude diagram reveals an unexpected bifurcation of colors in the main sequence (MS).…
Abundance anomalies observed in globular cluster stars indicate pollution with material processed by hydrogen burning. Two main sources have been suggested: asymptotic giant branch (AGB) stars and massive stars rotating near the break-up…
We investigate the formation processes of the Galactic globular cluster (GC) omega Cen with multiple stellar populations based on our original hydrodynamical simulations with chemical enrichment by Type II supernovae (SNe II), asymptotic…
The star formation history of the globular cluster Omega Centauri is investigated in the context of an inhomogeneous chemical evolution model in which supernovae induce star formation. The proposed model explains recent observations for…
To study the possible origin of the huge helium enrichment attributed to the stars on the blue main sequence of Omega Centauri, we make use of a chemical evolution model that has proven able to reproduce other major observed properties of…
The blue Main Sequence (bMS) of $\omega$ Cen implies a ratio of helium to metal enrichment $\Delta Y/\Delta Z \approx 70$, which is a major enigma. We show that rotating models of low metallicity stars, which account for the anomalous…
We study the formation of multiple populations in globular clusters (GC), under the hypothesis that stars in the second generation formed from the winds of intermediate-mass stars, ejected during the asymptotic giant branch (AGB) phase,…
We numerically investigate whether and how gaseous ejecta from AGB stars can be converted into new stars within originally massive star clusters (MSCs) in order to understand the origin of multiple stellar populations in globular clusters…
Recent observational studies have revealed star-to-star abundance inhomogeneity among light elements (e.g., C, N, O, Na, and Al) of stars on the main sequence in the Galactic globular clusters (GCs). One of promising interpretations for…
Recent observations for the color-magnitude diagrams (CMDs) of the massive globular cluster Omega Centauri have shown that it has a striking double main sequence (MS), with a minority population of bluer and fainter MS well separated from a…
We present a spectral atlas of the post-main-sequence population of the most massive Galactic globular cluster, omega Centauri. Spectra were obtained of more than 1500 stars selected as uniformly as possible from across the (B, B-V)…
Having shown in a recent paper that the main sequence of omega Centauri is split into two distinct branches, we now present spectroscopic results showing that the bluer sequence is_less_ metal-poor. We have carefully combined GIRAFFE@VLT…
We numerically investigate abundance properties of the Galactic globular clusters (GCs) by adopting a new ``external pollution'' scenario. In this framework, GCs are assumed to originate in forming low-mass dwarfs embedded in dark matter…
Using a chemical evolution model we investigate the intriguing suggestion that there are populations of stars in some globular clusters (e.g. NGC 2808, omega Centauri) with enhanced levels of helium (Y from about 0.28 to 0.40) compared to…
The most massive Galactic globular cluster, Omega centauri, appears to have multiple populations. Its bluest main sequence and extended horizontal branch stars are suggested to have the common origin, that is, an extremely high helium…
There is a growing body of evidence for the presence of multiple stellar populations in some globular clusters, including NGC 1851. For most of these peculiar globular clusters, however, the evidence for the multiple red giant-branches…