Axel Hahlin (Uppsala University): Multi-scale magnetic field analysis of single and binary late-type stars (6 Month Seminar)

Thursday 12 Dec 2024, 14:00 → 15:00 Europe/Stockholm

Title: Multi-scale magnetic field analysis of single and binary late-type stars
Speaker: Axel Hahlin
Affiliation: Uppsala University
Time: Thursday 12th December 2024, 14:00 to 15:00
Location: 101166 Å

Abstract:  Stellar magnetism can have a significant influence on both the star and its surroundings. The most direct way to measure these magnetic fields on stars is to utilise the Zeeman effect on magnetically sensitive spectral lines as both the line shape and polarisation of the line contains information of the stellar magnetic field.

I have worked on eclipsing binary stars in order to test the possible influence of convective inhibition caused by magnetic fields that tends to increase stellar radii. While this radius inflation has been observed and theoretical predictions on magnetic fields have been made, little work has been done on the observational characterisation of the magnetic fields of these binaries. What our studies have revealed is that the observed magnetic fields are closely in line for what would be needed to suppress convection and inflate the star. Indicating that magnetic fields could be the answer to the radius inflation problem.

Another important discussion point is the systematic sensitivity to different models and choice of spectral lines. What we find is that both of these aspects can significantly shift magnetic field results. In particular, the choice of spectral line sensitivity indicates that different lines might be sensitive to different regions in the stellar photosphere. While more work needs to be done to resolve this, it does open up an interesting opportunity to get a better idea of magnetic structures on stellar surfaces.