Coronal genealogy: the evolution of high-energy emission from low-mass stars
28 February 2023
About the project
This PhD project will use models and observations of forming low-mass stars to shed light on the history and evolution of Sun-like stars.
Newborn stars are violent high-energy emitters - up to ten-thousand times more luminous in X-rays than the present-day Sun. Many are still surrounded by substantial disks of gas and dust, the eventual birthplace of planets. How their X-ray emission evolves over time and how it is linked to the stellar magnetic field topology derived from observations are open questions. High-energy emission may influence the disk chemistry and structure, and therefore the formation of planets.
Large spectropolarimetric surveys have revealed that the magnetic field topology of young stars is linked to their internal structure. Pre-main sequence magnetism evolves as stars complete their gravitational contraction and move across the Hertzsprung-Russell diagram. In particular, it appears as though Sun-like stars are born with simple magnetic fields that become more multipolar/complex as the stellar internal structure transitions from fully to partially convective (Gregory et al. 2012). This magnetic topology evolution also has a signature in X-rays, with some stars losing their coronae as they evolve towards the main sequence (Gregory et al. 2016).
Using the latest observational data as a basis, the student will model the star-disk interaction and coronal magnetic evolution as a function of magnetic field topology, as stars evolve across the pre-main sequence. For more mature pre-main sequence stars, where the disk has dispersed but the star is still contracting under gravity, it has been observed that the scatter in X-ray luminosities decreases. However, stars in young clusters do not yet follow the well known rotation-activity relation (e.g. Argiroffi et al. 2016).
You will create a series of simulated stellar clusters, evolved from observational data of pre-main sequence regions, to model the emergence of the rotation-activity relation.
The work will be guided by observed trends in stellar magnetism (Vidotto et al. 2014) and exploit ground and space-based data (e.g. from the Gaia satellite and the SPIRou nIR spectropolarimeter). The overarching goal is to develop a framework for how stellar coronal X-ray emission must vary with age, rotation, and magnetic field topology, for stars of differing mass and internal structure.
How to apply
- Email Dr Scott Gregory, (firstname.lastname@example.org) to:
- send a copy of your CV
- discuss your potential application and any practicalities (e.g. suitable start date)
- After discussion with Dr Gregory, formal applications can be made via our direct application system.