Frontier Research in Astrophysics - A Review from a personal point of view

Abstract

The 17 O(p,α) 14 Na reaction plays a key role in various astrophysical scenarios, from asymptotic giant branch stars to classical novae. It affects the synthesis of rare isotopes such as 17 O and 18 F, which can provide constraints on astrophysical models. Bruno et al. (2016) performed direct determination of the resonance strength E R = 64.5 keV of that reaction at the LUNA accelerator. They found a factor of 2 increase in the reaction rate at astrophysical temperatures relevant to shell hydrogen burning in red giant and asymptotic giant branch stars. The new rate implies lower 17 O/ 16 O ratios, with important implications on the interpretation of astrophysical observable quantities from these stars, as deeply discussed by Straniero et al. (2017). In order to further remark the importance of LUNA measurement, we would like to mention the crucial problem of the correct prediction of the abundances of the light nuclides produced during the epoch of Big Bang Nucleosynthesis (BBN) which is one of the main topics of modern cosmology. Trezzi et al. (2017) report results about the cross section of the 2 H(α,γ) 6 Li reaction that controls 6 Li production in the Big Bang. The cross section has been directly measured at the energies of interest for BBN for the first time, at center-of-mass energy E cm = 80, 93, 120, and 133 keV. They found that the 2 H(α,γ) 6 Li thermonuclear reaction rate is even lower than previously reported, thus increasing the discrepancy between predicted Big Bang 6 Li abundance and the amount of primordial 6 Li inferred from observations. A general data base for Experimental Nuclear Reaction Data (EXFOR) can be found in: https://www-nds.iaea.org/exfor/exfor.htm. PoS(FRAPWS2018)001 Frontier Research in Astrophysics Franco Giovannelli 2.1 Accretion Processes in Cosmic Sources Accretion is a universal phenomenon that takes place in the vast majority of astrophysical objects. The progress of ground-based and space-borne observational facilities has resulted in the great amount of information on various accreting astrophysical objects, collected within the last decades. The accretion is accompanied by the process of extensive energy release that takes place on the surface of an accreting object and in various gaseous envelopes, accretion disk, jets and other elements of the flow pattern. The results of observations inspired the intensive development of accretion theory, which, in turn, enabled us to study unique properties of accreting objects and physical conditions in the surrounding environment. One of the most interesting outcomes of this intensive study is the fact that accretion processes are, in a sense, self-similar on various spatial scales from planetary systems to galaxies.