A5027465292- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Nuclear physics research studies
- Astronomical and nuclear sciences
- History and Developments in Astronomy
- High-pressure geophysics and materials
- Solar and Space Plasma Dynamics
- Astronomical Observations and Instrumentation
- Geophysics and Gravity Measurements
- Galaxies: Formation, Evolution, Phenomena
- Adaptive optics and wavefront sensing
- Scientific Research and Discoveries
- Historical Astronomy and Related Studies
- Atmospheric Ozone and Climate
- Molecular Spectroscopy and Structure
- Solid-state spectroscopy and crystallography
- Geological and Geophysical Studies
- Tribology and Lubrication Engineering
- Cosmology and Gravitation Theories
- Crystal Structures and Properties
Astronomical Observatory of Rome
2015-2024
National Institute for Astrophysics
2013-2024
Sapienza University of Rome
2010
University of Palermo
2005-2007
European Space Astronomy Centre
2006
Université de Montpellier
2006
Instituto de Astrofísica de Canarias
2006
Consejo Superior de Investigaciones Científicas
2006
Office of AIDS Research
2004
Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano
1985-1997
view Abstract Citations (856) References (54) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS New Pre--Main-Sequence Tracks for M <=2.5 Msun as Tests of Opacities and Convection Model D'Antona, Francesca ; Mazzitelli, Italo We present tabular graphic results on the computation pre-main-sequence evolutionary tracks Population I stellar structures from 2.5 to approximately 0.015 solar mass. Deuterium lithium burning are followed in detail. The chosen input...
Some globular clusters are observed to host a population of second generation (SG) stars which show chemical anomalies and must have formed from gas containing matter processed in the envelopes first (FG) cluster stars. We study SG formation process by means 1D hydrodynamical simulations, assuming that is ejected AGB This collects cooling flow into core, where it forms star subsystem strongly concentrated innermost regions with structural properties largely independent FG initial properties....
High dispersion spectra () for a quite large number of stars at the main sequence turn-off and base giant branch in NGC 6397 6752 were obtained with UVES on Kueyen (VLT UT2). The [Fe/H] values we found are respectively, where first error bars refer to internal second ones systematic errors (within abundance scale defined by our analysis 25 subdwarfs good Hipparcos parallaxes). In both clusters [Fe/H]'s TO-stars agree perfectly few percent) that RGB. value obtain is low, but it agrees...
We use high-precision photometry of red-giant-branch (RGB) stars in 57 Galactic globular clusters (GCs), mostly from the ‘Hubble Space Telescope (HST) UV Legacy Survey GCs’, to identify and characterize their multiple stellar populations. For each cluster pseudo-two-colour diagram (or ‘chromosome map’) is presented, built with a suitable combination magnitudes F275W, F336W, F438W, F814W filters that maximizes separation between In chromosome map most GCs (type-I clusters), separate two...
In this paper we describe a new UV-initiative HST project (GO-13297) that will complement the existing F606W and F814W database of ACS Globular Cluster (GC) Treasury by imaging most its clusters through UV/blue WFC3/UVIS filters F275W, F336W F438W. This "magic trio" has shown an uncanny ability to disentangle characterize multiple-population (MP) patterns in GCs way is exquisitely sensitive C, N, O abundance variations. Combination these passbands with those optical also gives best leverage...
Mass-loss of red giant branch (RGB) stars is still poorly determined, despite its crucial role in the chemical enrichment galaxies. Thanks to recent detection solar-like oscillations G–K giants open clusters with Kepler, we can now directly determine stellar masses for a statistically significant sample old NGC 6791 and 6819. The aim this work constrain integrated RGB mass-loss by comparing average mass clump (RC) that low-luminosity portion [i.e. L≲L(RC)]. Stellar were determined combining...
We build on the evidence provided by our Legacy Survey of Galactic globular clusters (GC) to submit a crucial test four scenarios currently entertained for formation multiple stellar generations in GCs. The observational constraints be fulfilled are manifold, including GC specificity, ubiquity, variety, predominance, discreteness, supernova avoidance, p-capture processing, helium enrichment and mass budget. argue that appealing supermassive stars, fast rotating massive stars interactive...
We present yields from stars of mass in the range Mo<M<8Mo metallicities Z=0.0003 and Z=0.008, thus encompassing chemistry low- high-Z Globular Clusters. The are based on full evolutionary computations, following evolution pre-Main Sequence through Asymptotic Giant Branch phase, until external envelope is lost. Independently metallicity, with M<3Mo dominated by Third Dredge-Up, ejecting into their surroundings gas enriched carbon nitrogen. Conversely, Hot Bottom Burning main responsible for...
Recent work, based on data from the Hubble Space Telescope (HST ) UV Legacy Survey of Galactic Globular Clusters (GCs), has revealed that all analysed clusters host two groups first- (1G) and second-generation (2G) stars. In most GCs, both 1G 2G stars substellar populations with different chemical composition. We compare multiwavelength HST photometry synthetic spectra to determine for first time average helium difference between in a large sample 57 GCs maximum variation within each them....
Fully evolutionary models have been built to follow the phases of asymptotic giant branch evolution with mass loss for metal fractions from Z = 2 × 10-4 4 10-3. The hot bottom burning at base convective envelope is followed by fully coupled nuclear and noninstantaneous mixing. also show occurrence a spontaneous (i.e., not induced overshooting) third dredge-up. For first time, we find that temperatures close or even larger than 108 K are achieved low Z; full CNO cycle operates envelope, 16O...
We studied the color distribution of main sequence Globular Cluster NGC 2808, based on new deep HST-WFPC2 photometry a field in uncrowded outskirts cluster. The stars is wider than expected for single stellar population, given our (carefully determined) measurement errors. About 20% sample are much bluer and most plausibly explained as population having larger helium abundance bulk sequence. estimate that mass fraction these Y ~ 0.4. 2808 may have suffered self-enrichment, with different...
It is becoming clear that `self--pollution' by the ejecta of massive asymptotic giant branch stars has an important role in early chemical evolution globular cluster stars, producing CNO abundance spreads which are observed also at surface unevolved stars. Considering processed must be helium enriched, we have modelled stellar taking into account this possible enhancement with respect to primordial value. We show differences between main evolutionary phases (main sequence, turn--off and red...
Enhancement and spread of helium among globular cluster stars have been recently suggested as a way to explain the horizontal-branch blue tails in those clusters that show primordial abundances C, N, O, other elements involved advanced CNO burning. Helium enhancement is unavoidable if matter responsible for abundance spreads identified with lost by massive asymptotic giant branch stars, which evolve during early phases life, we noted 2002. In this paper examine implications hypothesis that,...
We use Hubble Space Telescope (HST) and ground-based imaging to study the multiple populations of 47 Tucanae (47 Tuc), combining high-precision photometry with calculations synthetic spectra. Using filters covering a wide range wavelengths, our HST splits main sequence into two branches, we find that this duality is repeated in subgiant red giant regions, on horizontal branch. calculate theoretical stellar atmospheres for main-sequence stars, assuming different chemical composition mixtures,...
A large number of spectroscopic studies have provided evidence the presence multiple populations in globular clusters by revealing patterns stellar chemical abundances. This paper is aimed at studying origin these abundance patterns. We explore a model which second generation (SG) stars form out mix pristine gas and ejecta first asymptotic giant branch stars. study constraints imposed data SG on properties super ejecta. With simple one-zone model, we then formation population focussing our...
In this study we present first results from multi-wavelength Hubble Space Telescope (HST) observations of the Galactic globular cluster GC NGC2808 as an extension UV Legacy Survey GCs (GO-13297 and previous proprietary HST archive data). Our analysis allowed us to disclose a multiple-stellar-population phenomenon in even more complex than previously thought. We have separated at least five different populations along main sequence red giant branch (RGB), that name A, B, C, D E (though finer...
Multi-band Hubble Space Telescope photometry reveals that the main sequence, sub-giant, and red-giant branch of globular cluster NGC 6752 splits into three components in close analogy with distinct segments along its horizontal stars. These triple sequences are consistent stellar groups: a population chemical composition similar to field-halo stars (Population a), Population (c) enhanced sodium nitrogen, depleted carbon oxygen, an helium abundance (ΔY ∼ 0.03), (b) intermediate (between...
It is well appreciated that the description of overadiabatic convection affects structure envelopes luminous asymptotic giant branch (AGB) stars in phase "hot bottom burning" (HBB). We stress this important uncertainty modeling plays a role which much more dramatic than can be ascribed, e.g., to nuclear cross-sections. Due tentatively attributed today HBB nucleosynthesis as site self-enrichment Globular Clusters stars, it necessary explore difference obtained by different prescriptions for...
We explain the multiple populations recently found in 'prototype' Globular Cluster (GC) NGC 2808 framework of asymptotic giant branch (AGB) scenario. The chemistry five -or more- is approximately consistent with a sequence star formation events, starting after supernovae type II epoch, lasting until time when third dredge up affects AGB evolution (age ~90-120Myr), and ending Ia begin exploding cluster, eventually clearing it from gas. different requires episodes gas diluted amounts pristine...
We present an abundance analysis of 96 horizontal branch (HB) stars in NGC2808, a globular cluster exhibiting complex multiple stellar population pattern. These are distributed different portions the HB and cover wide range temperature. By studying chemical abundances this sample, we explore connection between morphology enrichment history populations. For lying on red HB, use GIRAFFE UVES spectra to determine Na, Mg, Si, Ca, Sc, Ti, Cr, Mn, Fe, Ni, Zn, Y, Ba, Nd abundances. colder, blue...
Numerous spectroscopic and photometric observational studies have provided strong evidence for the widespread presence of multiple stellar populations in globular clusters. In this paper, we study long-term dynamical evolution population clusters, focusing on spatial distributions first- (FG) second-generation (SG) stars. previous studies, suggested that SG stars formed from ejecta FG AGB are expected initially to be concentrated cluster inner regions. Here, by means N-body simulations,...
We present preliminary asteroseismic results from Kepler on three G-type stars. The observations, made at one-minute cadence during the first 33.5d of science operations, reveal high signal-to-noise solar-like oscillation spectra in all stars: About 20 modes may be clearly distinguished each star. discuss appearance spectra, use frequencies and frequency separations to provide radii, masses ages stars, comment light these prospects for inference other solar-type stars that will observe.
Context: We present the physical and chemical properties of intermediate-mass stars models low metallicity, evolved along thermal pulse phase. Aims: The target this work is to extend metallicities, Z=1,2 6 x 10^{-4}, previously computed for chemistries typical Globular Clusters an intermediate metallicity (Z=0.001), most metal-rich clusters found in our Galaxy (Z=0.004); main goal test self-enrichment scenario also metal poor Methods: calculated three grids with metallicities Z=10^{-4},...
We present high-precision multi-band photometry for the globular cluster (GC) M2. combine analysis of photometric data obtained from Hubble Space Telescope UV Legacy Survey Galactic GCs GO-13297, with chemical abundances by Yong et al.(2014), and compare models in order to analyze multiple stellar sequences we identified color-magnitude diagram (CMD). find three main components, composed metal-poor, metal-intermediate, metal-rich stars (hereafter referred as population A, B, C,...