Licentiat defence: Fundamental atmospheric parameters of M dwarfs

  • Date: –17:00
  • Location: Online: Zoom
  • Lecturer: Terese Olander
  • Website
  • Organiser: Division of Astronomy and Space Physics, Department of Physics and Astronomy
  • Contact person: Terese Olander
  • Licentiatseminarium

M dwarfs have become important targets in the hunt for exoplanets. This is due to that over 70% of the stars in the Galaxy are M dwarfs and their faintness and small radii make it easier to detect exoplanets around them, especially planets in the habitable zone. In order to determine habitability of the planet we must first characterise the host stellar atmosphere, which can be done with spectroscopic methods.

However, M dwarfs are difficult targets. Their spectra have many molecular features, blending and masking atomic lines complicating spectroscopic analysis. At near-infrared wavelengths there are less molecules and more stellar flux.

In this thesis we go through M dwarf characteristics such as common molecules found in the atmosphere and observational challenges. We also present a short review on spectroscopic methods and non-LTE effects.

We present the results from a comparative study between different spectroscopic methods in which we found that the effective temperatures agree within uncertainties while the surface gravities and metallicities do not. We explored the differences by looking into non-LTE effects of iron and potassium and found a negligible effect for iron and a significant effect for potassium.

Link for defence on zoom: