scholarly journals 4He abundances: Optical versus radio recombination line measurements

2009 ◽  
Vol 5 (S268) ◽  
pp. 101-106 ◽  
Author(s):  
Dana S. Balser ◽  
Robert T. Rood ◽  
T. M. Bania
Keyword(s):  
Big Bang ◽  
Abundance Ratio ◽  
Small Sample ◽  
Galactic Evolution ◽  
Recombination Line ◽  
Big Bang Nucleosynthesis ◽  
Radio Recombination Line ◽  
Ratio Data ◽  
The Galaxy ◽  
Green Bank Telescope

AbstractAccurate measurements of the 4He/H abundance ratio are important in constraining Big Bang nucleosynthesis, models of stellar and Galactic evolution, and H ii region physics. We discuss observations of radio recombination lines using the Green Bank Telescope toward a small sample of H ii regions and planetary nebulae. We report 4He/H abundance ratio differences as high as 15–20% between optical and ratio data that are difficult to reconcile. Using the H ii regions S206 and M17 we determine 4He production in the Galaxy to be dY/dZ = 1.71 ± 0.86.

scholarly journals Lithium-6 Nucleosynthesis in the ISM

1995 ◽  
Vol 10 ◽  
pp. 465-466
Author(s):  
Robert A. Malaney
Keyword(s):  
Big Bang ◽  
Galactic Evolution ◽  
Local Interstellar Medium ◽  
Complete Understanding ◽  
Big Bang Nucleosynthesis ◽  
Lithium Isotopes ◽  
Primordial Nucleosynthesis ◽  
The Past ◽  
The Galaxy ◽  
Primordial Abundance

The nucleosynthesis of 6Li in the galaxy has become of considerable interest in the past year. This is largely because of the exciting developments relating to the first detection of this isotope outside of our own solar system. Not only has 6Li been recently detected in the atmospheres of halo dwarfs [1-2], but also in the local interstellar medium (ISM) [3-4].It is well known that knowledge of the primordial abundance of the lithium isotopes has important ramifications for cosmology, through the constraints they impose on standard big bang nucleosynthesis (SBBN) [5], and those imposed on non-standard primordial nucleosynthesis models. Since a complete understanding of the galactic evolution of the lithium isotopes is a prerequisite to unambiguously determining their primordial abundance, a thorough interpretation of the new 6Li data in the context of chemical evolution models cannot be overstated.

scholarly journals Li isotopes in metal-poor halo dwarfs: a more and more complicated story

2009 ◽  
Vol 5 (S268) ◽  
pp. 201-210
Author(s):  
Monique Spite ◽  
François Spite
Keyword(s):  
Cosmic Rays ◽  
Big Bang ◽  
The Other ◽  
Big Bang Nucleosynthesis ◽  
Lithium Abundance ◽  
The Galaxy ◽  
Li Isotope ◽  
Low Metallicity ◽  
The Big Bang ◽  
Early Galaxy

AbstractThe nuclei of the lithium isotopes are fragile, easily destroyed, so that, at variance with most of the other elements, they cannot be formed in stars through steady hydrostatic nucleosynthesis.The 7Li isotope is synthesized during primordial nucleosynthesis in the first minutes after the Big Bang and later by cosmic rays, by novae and in pulsations of AGB stars (possibly also by the ν process). 6Li is mainly formed by cosmic rays. The oldest (most metal-deficient) warm galactic stars should retain the signature of these processes if, (as it had been often expected) lithium is not depleted in these stars. The existence of a “plateau” of the abundance of 7Li (and of its slope) in the warm metal-poor stars is discussed. At very low metallicity ([Fe/H] < −2.7dex) the star to star scatter increases significantly towards low Li abundances. The highest value of the lithium abundance in the early stellar matter of the Galaxy (logϵ(Li) = A(7Li) = 2.2 dex) is much lower than the the value (logϵ(Li) = 2.72) predicted by the standard Big Bang nucleosynthesis, according to the specifications found by the satellite WMAP. After gathering a homogeneous stellar sample, and analysing its behaviour, possible explanations of the disagreement between Big Bang and stellar abundances are discussed (including early astration and diffusion). On the other hand, possibilities of lower productions of 7Li in the standard and/or non-standard Big Bang nucleosyntheses are briefly evoked.A surprisingly high value (A(6Li)=0.8 dex) of the abundance of the 6Li isotope has been found in a few warm metal-poor stars. Such a high abundance of 6Li independent of the mean metallicity in the early Galaxy cannot be easily explained. But are we really observing 6Li?

scholarly journals The Galactic Evolution of Boron

2000 ◽  
Vol 198 ◽  
pp. 405-414 ◽  
Author(s):  
Francesca Primas
Keyword(s):  
Hubble Space Telescope ◽  
Cosmic Ray ◽  
Big Bang ◽  
Stellar Structure ◽  
Current Status ◽  
Big Bang Nucleosynthesis ◽  
Medium Resolution ◽  
The Galaxy ◽  
Stellar Interiors ◽  
Astrophysical Research

Boron, together with lithium and beryllium, belongs to the group of the so-called light elements, the importance of which ranges from providing important tests to Big Bang nucleosynthesis scenarios to being useful probes of stellar interiors and useful tools to further constrain the chemical evolution of the Galaxy.Since it became operative in the late eighties, the Hubble Space Telescope (HST) and its high- and medium-resolution spectrographs have played a key role in analyzing boron. Boron has now been observed in several stars and in the interstellar medium (ISM), providing important information in different fields of astrophysical research (nucleosynthesis, cosmic-ray spallation, stellar structure). In particular, determinations of boron in unevolved stars of different metallicity have allowed to study how boron evolves with iron.After a general review of the current status of boron observations and of the major uncertainties affecting the measurements of its abundance, I will mainly concentrate on unevolved stars and discuss the ‘evolutionary’ picture emerging from the most recent analyses and how its interpretation compares with theoretical expectations. A brief discussion on future prospects will conclude this contribution, showing how the field may evolve and improve.

scholarly journals 3He(α,γ)7Be and 3H(α,γ)7Li reaction rates and implication for Big Bang nucleosynthesis in the potential model

2019 ◽  
Vol 49 ◽  
pp. 1960014 ◽  
Author(s):  
S. A. Turakulov ◽  
E. M. Tursunov
Keyword(s):  
Potential Model ◽  
Reaction Rates ◽  
Big Bang ◽  
Abundance Ratio ◽  
Recent Measurement ◽  
Big Bang Nucleosynthesis ◽  
Body Potential ◽  
Text Element ◽  
Good Agreement

The reaction rates of the direct astrophysical capture processes [Formula: see text] and [Formula: see text], as well as the abundance of the [Formula: see text] element are estimated in the framework of a two-body potential model. The estimated [Formula: see text] abundance ratio of [Formula: see text] is in a very good agreement with the recent measurement [Formula: see text] of the LUNA collaboration.

scholarly journals Abundances of the Very Light Elements (D, 3He, 4He and 7LI) And Primordial Nucleosynthesis

1986 ◽  
Vol 7 ◽  
pp. 377-382
Author(s):  
Jean Audouze
Keyword(s):  
Small Groups ◽  
Big Bang ◽  
Galactic Evolution ◽  
Light Elements ◽  
Big Bang Nucleosynthesis ◽  
Primordial Nucleosynthesis ◽  
Groups Of Galaxies

AbstractThe determinations of the primordial abundances of D, 3He, 4He and 7Li play a major role in building up models of Big Bang nucleosynthesis. Much progress has been made recently in that respect but there are still large uncertainties on these determinations. Although canonical Big Bang models predicting a cosmological baryonic parameter ΩB ~ 0.10 consistent with the dynamics of small groups of galaxies and three different families of neutrinos seem to be the most appropriate in accounting for these abundances, the simplest models of galactic evolution lead to discrepant comparisons concerning D and 4He. The relatively small abundance of 4He might challenge the canonical Big Bang models unless specific models of galactic evolution are invoked.

scholarly journals Big Bang Nucleosynthesis

2002 ◽  
Vol 187 ◽  
pp. 1-15
Author(s):  
D.N. Schramm
Keyword(s):  
Systematic Error ◽  
Big Bang ◽  
Baryon Density ◽  
Galactic Evolution ◽  
Big Bang Nucleosynthesis ◽  
X Ray ◽  
Baryonic Density ◽  
The Big Bang ◽  
The Universe

Big Bang Nucleosynthesis (BBN) is on the verge of undergoing a transformation now that extragalactic deuterium is being measured. Previously, the emphasis was on demonstrating the concordance of the Big Bang Nucleosynthesis model with the abundances of the light isotopes extrapolated back to their primordial values using stellar and Galactic evolution theories. Once the primordial deuterium abundance is converged upon, the nature of the field will shift to using the much more precise primordial D/H to constrain the more flexible stellar and Galactic evolution models (although the question of potential systematic error in 4He abundance determinations remains open). The remarkable success of the theory to date in establishing the concordance has led to the very robust conclusion of BBN regarding the baryon density. The BBN constraints on the cosmological baryon density are reviewed and demonstrate that the bulk of the baryons are dark and also that the bulk of the matter in the universe is non-baryonic. Comparison of baryonic density arguments from Lyman-α clouds, x-ray gas in clusters, the Sunyaev-Zeldovich effect, and the microwave anisotropy are made and shown to be consistent with the BBN value.

scholarly journals Constraints on Dark Matter from Primordial Nucleosynthesis

1987 ◽  
Vol 117 ◽  
pp. 499-523
Author(s):  
Jean Audouze
Keyword(s):  
Dark Matter ◽  
Chemical Evolution ◽  
Big Bang ◽  
Baryon Density ◽  
Cosmological Parameter ◽  
Big Bang Nucleosynthesis ◽  
Primordial Nucleosynthesis ◽  
The Galaxy ◽  
Predicted Values ◽  
The Universe

Primordial nucleosynthesis which is responsible for the formation of the lightest elements (D, 3He, 4He and 7Li) provides a unique way to determine the present baryon density pB in the Universe and therefore the corresponding cosmological parameter ΩB. After a brief summary of the relevant abundance determinations and of the consequences of the Standard Big Bang nucleosynthesis, it is argued that one needs to call for specific models of chemical evolution of the Galaxy in order to reconcile the observations with the predictions of this model. In this context the predicted values for ΩB should range from 4 10−3 to 6 10−2. These values are significantly lower than those deduced from current M/L determinations.

The Interstellar 7Li/6Li Ratio

1995 ◽  
Vol 10 ◽  
pp. 455-456
Author(s):  
R. Ferlet
Keyword(s):  
Cosmic Rays ◽  
Solar System ◽  
Big Bang ◽  
Galactic Cosmic Rays ◽  
Galactic Evolution ◽  
Big Bang Nucleosynthesis ◽  
Solar System Formation ◽  
Spallation Reactions ◽  
Primordial Abundance ◽  
Stellar Source

Lithium-7 is now generally accepted to originate in the hot Big Bang nucleosynthesis (BBN), with a primordial abundance (7Li/H)⋍ 10-10 in excellent agreement with the observed uniformity of the Li abundance in very metal deficient Pop II stars.During the galactic evolution, both Li isotopes are created by spallation reactions of galactic cosmic rays (GCR) interacting with the ISM, that yield (7Li/H)⋍ 2 × 10-10 in 10 Gyrs, with a ratio (7Li/6Li)GCR=1.4. The major problem is then to explain the observed Pop I Li abundance, (7Li/H)PopI ∼ 10-9, of which only 30% is accounted for by BBN and GCR spallation, as well as the high 7Li/6Li ratio measured in meteorites, representative of the solar system formation epoch 4.6 Gyrs ago, (7Li/6Li)⊙=12.3, whereas the above mechanisms predict a ratio around 2.The existence of an extra stellar source of Li has been suggested. GCR spallation alone tends to decrease the 7Li/6Li ratio with time, and one should observe today an interstellar ratio ≃5-6 without production of Li in stars, or ≳6 with a steuar production. Measuring this ISM ratio thus provides a key test for the models of lithium evolution. If it is found to be ≲5, then another scenario would have to be considered.

scholarly journals Elements in the Cosmos: Origin of the Light Elements

1991 ◽  
Vol 145 ◽  
pp. 3-12
Author(s):  
Hubert Reeves
Keyword(s):  
Cosmic Ray ◽  
Big Bang ◽  
Light Elements ◽  
Big Bang Nucleosynthesis ◽  
Hadron Phase ◽  
Iron Deficient ◽  
The Galaxy ◽  
Galactic Cosmic Ray ◽  
The Big Bang ◽  
Theoretical Developments

In the first part of this paper, a review is given of the situation of the Big Bang nucleosynthesis of the nuclides D, 3He, 4He and 7Li, taking into account the latest experimental data (number of neutrino species, lifetime of the neutron) and theoretical developments (quark-hadron phase transition). In the second part. I review the process of Galactic Cosmic Ray formation of lithium, beryllium and boron throughout the life of the galaxy, taking advantage of recent measurements of Be and Li in iron deficient stars.

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