Evolution of Lithium-Beryllium-Boron and Oxygen in the early Galaxy

Oxygen is a much better evolutionary index than iron to describe the history of Lithium-Beryllium-Boron (LiBeB) since it is the main producer of these light elements at least in the early Galaxy. The O-Fe relation is crucial to the determination of the exact physical process responsible for the LiBeB production. At low metallicity, if [O/Fe] vs [Fe/H] is flat, then the production mode is independent of the interstellar metallicity, BeB is proportional to oxygen, i.e. is of primary nature. If not, the production mode is function of the progressive enrichment in O of the interstellar medium, BeB varies rather as the square of O, i.e. is of secondary nature. In the first case, fast nuclei enriched into He, C and O injected by supernovae and accelerated in surrounding superbubbles would explain the primary trend. In the second case, the main spallative agent would be the standard galactic cosmic rays. Calculated nucleosynthetic yields of massive stars, estimates of the energy cost of production of beryllium nuclei, and above all recent observations reported in this meeting seem to favor the primary mechanism, at least in the early Galaxy.Comment: invited review, IAU Symposium, JD8, Manchester, August 2000, New Astronomy Review, in press 6 pages 1 figur

Lithium-Beryllium-Boron and Oxygen in the early Galaxy

Oxygen is a much better evolutionary index than iron to follow the history of Lithium-Beryllium-Boron (LiBeB) since it is the main producer of these light elements at least in the early Galaxy. The O-Fe relation is crucial to the determination of the exact physical process responsible for the LiBeB production. Calculated nucleosynthetic yields of massive stars, estimates of the energy cost of Be production, and above all recent observations reported in this meeting seem to favor a mechanism in which fast nuclei enriched into He, C and O arising from supernovae are accelerated in superbubbles and fragment on H and He in the interstellar medium.Comment: Invited Review, IAU, JD8, Manchester, August 2000, to be published in Highlights of Astronom

Nuclear Gamma ray Astronomy in the perspective of the INTEGRAL satellite

We present a broad overview of the principal processes and astrophysical sites of gamma-ray line production and review the main pre-INTEGRAL satellite observations to set the stage to the next European era of gamma-ray line astronomy.Comment: 5 pages, 0 figures, in "International Nuclear Physics Conference, Paris, August 1998, to be published Elsevier Ed

INTEGRAL and Nuclear Astrophysics

We briefly review the fundamentals of nuclear gamma-ray line astronomy (radioactive astronomy), focusing on its role to decipher the intimate physics of supernovae, either immediatly (via $^{56}Co)$ or after a time delay (via $^{44}Ti$). All kinds of supernovae can be in principle tested through their radioactivities and their associated gamma-ray lines. Dedicated to the spectroscopy and imaging of celestial sources in the 15 keV to 10 MeV band, the ESA scientific observatory INTEGRAL will open a golden age of nuclear astrophysics in EuropeComment: Invited review, "Cosmic Evolution", meeting in honor of the 60th birthday of Jean Audouze and Jim Truran, to be published by World Scientific, 6 pages, 1 figur

Big Bang Nucleosynthesis updated with the NACRE Compilation

We update the Big Bang Nucleosynthesis calculations on the basis of the recent NACRE compilation. The average values of the calculated abundances of light nuclei do not differ significantly from that obtained using the previous Fowler's compilation. ${^7}Li$ is slightly depressed at high baryon to photon ratio $\eta$. The main uncertainty concerns the $D(p,\gamma){^3}He$ reaction rate affecting the synthesis of ${^7}Li$ (via the ${^3}He(\alpha,\gamma){^7}Be(e\nu){^7}Li$) at rather high baryonic density. On the left part of the lithium valley the uncertainty is strongly reduced due to the improvement of the measurement of the $T(\alpha,\gamma)^{7}Li$ reaction rate. We use lithium-7 as the main baryometer, since, though much efforts have been devoted to the determination of Deuterium in absorbing clouds in the line of sight of remote quasars, the statistics is very poor compared to the long series of lithium measurements. Taking into account the lithium constraints, two possible baryonic density ranges emerge, $\eta_{10}= 1.4 - 1.9$ and $\eta_{10} = 3.3 - 5.1$. The Be and B abundances produced in the big bang are orders of magnitudes lower, and spallation of fast carbon and oxygen is probably their unique source, in the early Galaxy.Comment: 8 pages, 5 figures, accepted in Astronomy and Astrophysic

The Impact of the NACRE Compilation on the Big Bang Nucleosynthesis

We update the Big Bang Nucleosynthesis (BBN) calculations on the basis of the recent NACRE compilation of reaction rates. We estimate the uncertainties related to the nuclear reaction rates on the abundances of D, 3He, 4He, 6Li, 7Li, 9Be, 10B and 11B of cosmological and astrophysical interest. We use lithium as the main indicator of the baryon density of the Universe, rather than deuterium.Comment: 3 pages, 1 figure, contribution to Nuclei in the Cosmos 2000, proceedings to appear in Nucl. Phy

On the Galactic Evolution of DD and 3He^3He

The determined abundances of primordial $^4He$ and $^7Li$ provide a basis with which to test the standard model of big bang nucleosynthesis in conjunction with the other two light element isotopes $D$ and $^3He$, also produced in the big bang. Overall, consistency in the standard big bang nucleosynthesis model is best achieved for a baryon-to-photon ratio of typically $3 \times 10^{-10}$ for which the primordial value of $D$ is five times greater than the present observed abundance and about three times greater than the pre-solar value. We consider various models for the chemical evolution of the Galaxy to test the feasibility for the destruction of D without the overproduction of $^3He$ and overall metallicity. Models which are capable of achieving this goal include ones with a star formation rate proportional to the gas mass fraction or an exponentially decreasing star formation rate. We discuss the effect of parameters that govern the initial mass function and of surviving fractions of $^3He$ in stars between one and three solar masses.Comment: 25 pages, LaTeX, UMN-TH-1206/9

Updated Big-Bang Nucleosynthesis compared to WMAP results

From the observations of the anisotropies of the Cosmic Microwave Background (CMB) radiation, the WMAP satellite has provided a determination of the baryonic density of the Universe, \Omega_b.h^2, with an unprecedented precision. This imposes a careful reanalysis of the standard Big-Bang Nucleosynthesis (SBBN) calculations. We have updated our previous calculations using thermonuclear reaction rates provided by a new analysis of experimental nuclear data constrained by $R$-matrix theory. Combining these BBN results with the \Omega_b.h^2 value from WMAP, we deduce the light element (4He, D, 3He and 7Li) primordial abundances and compare them with spectroscopic observations. There is a very good agreement with deuterium observed in cosmological clouds, which strengthens the confidence on the estimated baryonic density of the Universe. However, there is an important discrepancy between the deduced 7Li abundance and the one observed in halo stars of our Galaxy, supposed, until now, to represent the primordial abundance of this isotope. The origin of this discrepancy, observational, nuclear or more fundamental remains to be clarified. The possible role of the up to now neglected 7Be(d,p)2\alpha and 7Be(d,\alpha)5Li reactions is considered.Comment: Invited contribution to the Origin of Matter and Evolution of the Galaxies (OMEG03) conference, RIKEN, Japan. Proceedings to appear in World Scientifi