Master defense by David John Willumsen

Title: Effect of water in cool atmospheres

Abstract: Water is one of the most abundant species that have been identified in observed exoplanets. Yet, there are several existing theoretical line lists that, when applied to model spectra, give quite different interpretations of the observed spectra.
The project concerns comparing results from the different line lists and estimating which are in best agreement with observations.

The compared line lists, SCAN, BT2, POKAZATEL, and HITEMP are implemented in cool atmospheric models using marcs to compute synthetic spectra. The spectra are compared to mediumresolution spectra of M-dwarfs from the SpeX Prism Library and an SWS-ISO spectrum of M-giant SV Peg. All line lists show good fits with the giant spectrum, while the dwarf synthetic spectra from BT2, POKAZATEL, and HITEMP models show long-wavelength and short-wavelength regions, that can not fit the observed spectra simultaneously. I discuss the possible explanations for their inability to reproduce these spectra, and what this means for the use of line lists in stellar modeling.

The defense takes place at the Auditorium of the Geological Museum (Øster Voldgade 5-7), but can also be followed via Zoom: