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

Lithium-Beryllium-Boron Evolution: From Meneguzzi, Audouze and Reeves 1971 Up to Now

We review the main sources of LiBeB production and show that a primary mechanism is at work in the early Galaxy involving both ejection and acceleration of He, C and O at moderate energy, which by nuclear interaction with H and He produce light isotopes. The precise measurement of the Be abundance at [Fe/H] = -3.3 and of $^6Li$ in halo stars find an explanation in this framework. Thus, the preservation of $^6Li$ in the atmosphere of metal poor stars implied, points toward the fact the Spite plateau reflects the primordial value of Li. Consequently, it can be used as a baryodensitometer.Comment: 6 pages, no figure, invited talk, to be published in World Scientific, Proceedings of the conference "Cosmic Evolution" in the honor of Jean Audouze and James W. Truran, held at the Institut d'Astrophysique de Paris, Franc

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