Transition probabilities of trans-iron elements

• Applicant: Dr. Thomas Rauch
• Subject Area: Astrophysics and Astronomy
• Term: from 2017 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 386405709

For the quantitative spectral analysis of hot, compact stars, model atmospheres that consider deviations from the local thermodynamical equilibrium (LTE) are mandatory. In contrast to LTE where the occupations numbers of atomic levels are calculated via Saha and Boltzmann equations, in the so-called non-LTE, they have to be calculated in detail. A pre-requisite therefor is accurate data for all radiative and collisional transitions. This includes line transitions, i.e. radiative bound-bound transitions between the atomic levels. Precise oscillator strengths are necessary for all line transitions in the model atom that represents an element in the model-atmosphere calculation. The data quality is crucial for the precision of abundance determinations.The recent discovery of elements that are heavier that iron in a white dwarf allowed for the first time to determine the abundance of so-called trans-iron elements in evolved stars. This was only possible after the calculation of oscillator strengths. We propose in this project to extend the calculation of oscillator strengths to a large part of the trans-iron elements (copper to barium) and to calculate homogeneous data for the ionization stages III to VII, i.e. 2+ to 6+.The newly calculated oscillator strengths allow for the first time the abundance analysis of these elements in stars in the final phase of their evolution. This enables us to establish boundary conditions for the s-process nucleosynthesis, i.e. the creation of trans-iron elements by neutron captures.

• DFG Programme: Research Grants