scholarly journals Light Element Abundances and Multiple Populations in M53

2021 ◽  
Vol 161 (6) ◽  
pp. 288
Author(s):  
Jeffrey M. Gerber ◽  
Eileen D. Friel ◽  
Enrico Vesperini
Keyword(s):  
Light Element ◽  
Multiple Populations ◽  
Element Abundances

scholarly journals Chemical inhomogeneities amongst first population stars in globular clusters

2018 ◽  
Vol 616 ◽  
pp. A168 ◽  
Author(s):  
C. Lardo ◽  
M. Salaris ◽  
N. Bastian ◽  
A. Mucciarelli ◽  
E. Dalessandro ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Light Element ◽  
Small Range ◽  
Multiple Populations ◽  
Chromosome Map ◽  
Element Abundances ◽  
Metal Abundance ◽  
Suitable Combination ◽  
Chromosome Maps ◽  
Homogeneous Composition

Spreads in light element abundances among stars (also known as multiple populations) are observed in nearly all globular clusters. One way to map such chemical variations using high-precision photometry is to employ a suitable combination of stellar magnitudes in the F275W, F336W, F438W, and F814W filters (called the “chromosome map”), to maximise the separation between the different multiple populations. For each individual cluster its chromosome map separates the first population (with metal abundance patterns typical of field halo stars) from the second population (which displays distinctive abundance variations among a specific group of light elements). Surprisingly, the distribution of first population stars in chromosome maps of several but not all clusters has been found to be more extended than expected from purely observational errors, suggesting a chemically inhomogeneous origin. We consider here three clusters with similar metallicity ([Fe/H] ~ −1.3) and different chromosome maps, namely NGC 288, M 3, and NGC 2808, and argue that the first population extended distribution (as observed in two of these clusters) is due to spreads of the initial helium abundance and possibly a small range of nitrogen abundances as well. The presence of a range of initial He and N abundances amongst stars traditionally thought to have homogeneous composition, and that these spreads appear only in some clusters, challenges the scenarios put forward so far to explain the multiple population phenomenon.

scholarly journals Light Element Abundances and Multiple Populations in M10

2018 ◽  
Vol 156 (1) ◽  
pp. 6 ◽  
Author(s):  
Jeffrey M. Gerber ◽  
Eileen D. Friel ◽  
Enrico Vesperini
Keyword(s):  
Light Element ◽  
Multiple Populations ◽  
Element Abundances

scholarly journals Theoretical Predictions of Surface Light Element Abundances in Protostellar and Pre-Main Sequence Phase

2021 ◽  
Vol 8 ◽  
Author(s):  
E. Tognelli ◽  
S. Degl’Innocenti ◽  
P. G. Prada Moroni ◽  
L. Lamia ◽  
R. G. Pizzone ◽  
...  
Keyword(s):  
Cross Sections ◽  
Main Sequence ◽  
Light Element ◽  
Element Abundance ◽  
Light Elements ◽  
Convective Envelope ◽  
Stellar Envelope ◽  
Element Abundances ◽  
Stellar Interior ◽  
Theoretical Predictions

Theoretical prediction of surface stellar abundances of light elements–lithium, beryllium, and boron–represents one of the most interesting open problems in astrophysics. As well known, several measurements of 7Li abundances in stellar atmospheres point out a disagreement between predictions and observations in different stellar evolutionary phases, rising doubts about the capability of present stellar models to precisely reproduce stellar envelope characteristics. The problem takes different aspects in the various evolutionary phases; the present analysis is restricted to protostellar and pre-Main Sequence phases. Light elements are burned at relatively low temperatures (T from ≈2 to ≈5 million degrees) and thus in the early evolutionary stages of a star they are gradually destroyed at different depths of stellar interior mainly by (p, α) burning reactions, in dependence on the stellar mass. Their surface abundances are strongly influenced by the nuclear cross sections, as well as by the extension toward the stellar interior of the convective envelope and by the temperature at its bottom, which depend on the characteristics of the star (mass and chemical composition) as well as on the energy transport in the convective stellar envelope. In recent years, a great effort has been made to improve the precision of light element burning cross sections. However, theoretical predictions surface light element abundance are challenging because they are also influenced by the uncertainties in the input physics adopted in the calculations as well as the efficiency of several standard and non-standard physical processes active in young stars (i.e. diffusion, radiative levitation, magnetic fields, rotation). Moreover, it is still not completely clear how much the previous protostellar evolution affects the pre-Main Sequence characteristics and thus the light element depletion. This paper presents the state-of-the-art of theoretical predictions for protostars and pre-Main Sequence stars and their light element surface abundances, discussing the role of (p, α) nuclear reaction rates and other input physics on the stellar evolution and on the temporal evolution of the predicted surface abundances.

scholarly journals The light elements in a helio- and asteroseismic perspective

2009 ◽  
Vol 5 (S268) ◽  
pp. 387-394
Author(s):  
Sylvie Vauclair
Keyword(s):  
Main Sequence ◽  
Light Element ◽  
Heavy Elements ◽  
Light Elements ◽  
Main Sequence Stars ◽  
General Introduction ◽  
Helium Content ◽  
Element Abundances ◽  
The Past

AbstractAsteroseismology is a powerful tool to derive stellar parameters, including the helium content and internal helium gradients, and the macroscopic motions which can lead to lithium, beryllium, and boron abundance variations. Precise determinations of these parameters need deep analyses for each individual stars. After a general introduction on helio and asteroseismology, I first discuss the solar case, the results which have been obtained in the past two decades, and the crisis induced by the new determination of the abundances of heavy elements. Then I discuss asteroseismology in relation with light element abundances, especially for the case of main sequence stars.

Big Bang nucleosynthesis, microwave anisotropy, and the light element abundances

2005 ◽  
Vol 752 ◽  
pp. 522-531 ◽  
Author(s):  
A. Coc ◽  
C. Angulo ◽  
E. Vangioni-Flam ◽  
P. Descouvemont ◽  
A. Adahchour
Keyword(s):  
Light Element ◽  
Big Bang ◽  
Big Bang Nucleosynthesis ◽  
Element Abundances

scholarly journals Dark matter annihilation in the universe

2014 ◽  
Vol 30 ◽  
pp. 1460256 ◽  
Author(s):  
Pierre Salati
Keyword(s):  
Dark Matter ◽  
Galactic Halo ◽  
Light Element ◽  
Big Bang ◽  
Microwave Background ◽  
Dark Matter Annihilation ◽  
Element Abundances ◽  
Primordial Plasma ◽  
Relic Abundance ◽  
The Universe

The astronomical dark matter is an essential component of the Universe and yet its nature is still unresolved. It could be made of neutral and massive elementary particles which are their own antimatter partners. These dark matter species undergo mutual annihilations whose effects are briefly reviewed in this article. Dark matter annihilation plays a key role at early times as it sets the relic abundance of the particles once they have decoupled from the primordial plasma. A weak annihilation cross section naturally leads to a cosmological abundance in agreement with observations. Dark matter species subsequently annihilate — or decay — during Big Bang nucleosynthesis and could play havoc with the light element abundances unless they offer a possible solution to the 7 Li problem. They could also reionize the intergalactic medium after recombination and leave visible imprints in the cosmic microwave background. But one of the most exciting aspects of the question lies in the possibility to indirectly detect the dark matter species through the rare antimatter particles — antiprotons, positrons and antideuterons — which they produce as they currently annihilate inside the galactic halo. Finally, the effects of dark matter annihilation on stars is discussed.

Nucleosynthesis

1986 ◽  
Vol 320 (1556) ◽  
pp. 557-564 ◽  
Keyword(s):  
Light Element ◽  
Hubble Constant ◽  
Big Bang ◽  
Element Abundances ◽  
Stellar Nucleosynthesis ◽  
Baryonic Density ◽  
Redshift Surveys ◽  
A Value ◽  
First Case ◽  
The Universe

Both Big-Bang and stellar nucleosynthesis have outcomes related to the density of baryonic matter, but whereas in the first case there is a standard model that makes very precise predictions of light element abundances as a function of the mean density of baryons in the Universe, in the second case various uncertainties permit only very limited conclusions to be drawn. As far as Big-Bang synthesis and the light elements are concerned, existing results on D, 3 He and 7 Li indicate a value of Ω N h 2 0 greater than 0.01 and less than 0.025, where Ω N is the ratio of baryonic density to the closure density and h 0 is the Hubble constant in units of 100 km s -1 Mpc -1 ; probably 0.5 < h 0 < 1. New results on the primordial helium abundance give a still tighter upper limit to Ω N ,Ω N h 2 0 < 0.013, which when compared with redshift surveys giving Ω > 0.05 implies that the observed matter can all be baryonic only if the various uncertainties are stretched to their limits.

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