Dr. Joachim Puls is renowned for his research on stellar winds in high-mass stars. He has also done fundamental research on the modelling of the expanding atmospheres of these stars. He has also worked on the determination of nitrogen abundances on the surfaces of O-type stars, which is a key element in testing current evolutionary calculations for these objects. Dr. Joachim Puls has been chairman of the IAU commission on massive stars and has collaborated with prestigious organisations worldwide. He has also been a researcher and professor of numerical and statistical methods and radiative transport in stellar atmospheres at the Ludwig-Maximilians-University in Munich for four decades.

Dr. Joachim Puls is one of the world's few experts in modelling radiative transport in (expanding) atmospheres of high-mass stars who are still active today. In addition to being one of the world's leading references in the field (with more than 15000 citations associated with his more than 160 refereed papers in top journals, including several review articles in A&A), he is the main developer of the stellar atmosphere code FASTWIND (Puls et al. 2005) and has maintained a high commitment to passing on knowledge to new generations during his long career that started almost 40 years ago. As an example of the latter, Dr Puls was one of the lecturers at the XXIX IAC Winter School in 2017.

The main objectives of his visit to the IAC are: 

• Testing and improving the atomic models of C, N, O, Si and Mg that are currently incorporated in the FASTWIND atmosphere code.
• Improving the treatment of line-blanketing effects in the effective temperature region between 15000 and 8000 K. 
• The study of the possibility of solving the persistent problem of the ‘mass discrepancy’ by incorporating turbulence pressure effects in the modelling of the atmospheres of O- and B-type stars. 
• The incorporation of machine learning techniques in the modeling and analysis of high-mass stars, including diagnostic lines that give information on the fundamental properties of stellar winds.