A survey of the inner Galaxy region of Galactic longitude

Nuclear astrophysics is a field at the intersection of nuclear physics and astrophysics, which seeks to understand the nuclear engines of astronomical objects and the origin of the chemical elements. This white paper summarizes progress and status of the field, the new open questions that have emerged, and the tremendous scientific opportunities that have opened up with major advances in capabilities across an ever growing number of disciplines and subfields that need to be integrated. We take a holistic view of the field discussing the unique challenges and opportunities in nuclear astrophysics in regards to science, diversity, education, and the interdisciplinarity and breadth of the field. Clearly nuclear astrophysics is a dynamic field with a bright future that is entering a new era of discovery opportunities.

In the study of the crust of an accreting neutron star, electron capture rates on nuclei in the mass range A=20-106 from the neutron deficient region to the neutron drip line are needed. At the low temperatures typical of a neutron star crust (T 9 ∼ 0.4) the determination of the phase space poses a problem since the integrand is very sharply peaked and an error in finding the peak using numerical differentiation or cruder maximum-locator methods will result in inaccuracies at the energies where the integrand has its highest value. In this work we present a global set of temperature and density-dependent continuum electron capture rates and a fast phase space calculator valid for low temperatures. The electron capture rates have been calculated using Gamow-Teller strength distributions from the quasi-particle random-phase approximation (QRPA, [1]) nuclear model. We present a new analytic technique to carry out the evaluation of the phase space for electron capture that is fast enough to be implemented in a reaction network. The integral is split into two separate terms at the chemical potential of the electron gas, thus eliminating the need to find the peak of the integrand. The Coulomb correction, which is essentially constant over the range of energies considered, is taken outside the integral and is evaluated at a suitable effective energy which is a function of the charge of the capturing nucleus, the temperature, the chemical potential and the threshold. We compare our calculated electron capture rates to the compilations by Fuller, Fowler and Newman [2] and by . Cosmos -IX 25-30 June 2006 CERN * Currently at Theoretical Division, Los Alamos National Laboratory, NM 87545. International Symposium on Nuclear Astrophysics -Nuclei in thec Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.http://pos.sissa.it/ PoS(NIC-IX)075Electron capture rates for neutron star crusts MotivationObserved X-ray bursts in the universe have been explained as the result of thermonuclear explosions on the surface of a neutron star accreting matter from a companion in a binary system. Superbursts are extremely powerful X-ray bursts in which the energy release is ∼ 10 3 times that of a regular burst. They occur with less frequency but have longer cooling timescales (on the order of hours). Superbursts show the same spectral behavior as a normal X-ray burst and hence they are thought to have a thermonuclear nature too, being fueled by the ashes of regular X-ray bursts. Thus, a detailed understanding of the underlying nuclear physics is needed in the study of these phenomena [4]. Deep crust processes, like electron captures and pycnonuclear fusion are crucial in these studies since they determine the composition and thermal properties of the neutron star crust.At accretion rates of ∼ 10 −8 − 10 −10 M yr −1 , a neutron star can accrete enough material from its companion to replace its entire crust with ashes of H and He burning not in nuclear statistical equilibrium (N...

in the fall of 2005. The purpose of the campaign was the measurement of the β-decay half-lives and β-delayed neutron-emission probabilities of different unknown neutron-rich nuclei participating in the r-process. Details of this campaign are presented.