Ponente
Descripción
There are many stellar phenomena that are not well understood yet, one of these processes is the Type I X-ray bursts (XRBs). These explosions happen at the surface of neutron stars accreting material from a lower-mass companion. The physical observable in such events is the light curve, i.e., the time evolution of the emitted x-ray intensity. Due to the huge mass of the neutron star, no matter is emitted from the surface and, therefore, there is no direct information about the isotopes created in the nucleosynthesis taking place. With the current models, the simulations of type I XRBs strike to recreate the observed light curve.
The starting point of the XRB is triggered by the triple alpha process, running away from the Hidrogen burning in a proton-rich environment. Subsequent proton capture lead then to the rp-process, along the N=Z line, at temperatures like $10^8$ K. In this regime, a good knowledge of the nuclear data involved in the reactions and decays happening in the rp-process, along the N=Z line, is of paramount importance so the simulations recreating all the nuclear processes at stellar conditions, can reproduce the observed light curves.
In this context, some N=Z nuclei, in which the beta decay can compete with the proton capture, act as waiting points in the nuclear reaction flow. The beta decays of these waiting points are crucial important in the time evolution of the nucleosynthesis, and therefore the light curves, being ${}^{64}$Ge, the main bottle-neck of the rp-process reaction flow. However, the beta-decay properties (Q-value and half-life) at XRB conditions of density and temperature are different from the ones in terrestrial conditions. This means that, at the end, we need robust nuclear theoretical models to calculate the half-lives and Qec values in stellar conditions. These models can only be tested with differential physical quantities, B(GT) distributions rather than half-lives, in the decays of interest.
We applied the Total Absorption Spectroscopy (TAS) technique to measure the beta decay of ${}^{64-66}$Ge and of their daughters ${}^{64-66}$Ga, because for every Ge analysis we need to performed an analysis on its isobar Ga daughter since they did appears on the Ge measurements. In this talk a summary of the research made by our group on the study of the beta decay of relevant waiting point nuclei in type I X-rays burst with emphasis on the latest measurement: ${}^{64}$Ge.
