Probing the link between magnetism and accretion/ejection in young stars

The magnetic field is thought to play a central role in the formation of young stars and their associated protoplanetary disks. In particular, young solar type stars host strong ordered kG magnetic fields which shape the accretion flow of matter from the inner disk onto the protostellar surface. This magnetospheric accretion scenario likely plays an important role in regulating the angular momentum evolution of the protostar and in the launching of the high velocity collimated jets, commonly observed around forming stars and whose origin are still debated.

While the magnetospheric accretion scenario is now well established for the optically revealed 1 Myrs old T Tauri stars, it is not clear if it applies to the younger still embedded Class I sources. The objectives of the ANR PROMETHEE project (PI: E. Alecian, dates here ) is to caracterize the magnetic and accretion/ejection properties of this class of objects. This project is a critical missing step in our understanding of the magnetic and angular momentum evolution of young stars.

The proposed PhD project builds on the extensive high spectral resolution and multi-epoch spectro-polarimetric database collected on 15 Class I sources within the context of PROMETHEE, in particular with the SPIROU instrument at the TCFH. The first goal will be to analyze accretion line diagnostics, which combined with the constraints on the magnetic field strength, will allow to investigate the dominant mode of accretion. In a second step, we will analyze ejection line diagnostics and investigate correlation of their properties with the stellar magnetic properties and accretion mode. This first systematic statistical study will provide unprecedented constraints on the role of the prostellar B-field in accretion and ejection processses. Extension of this analysis to archival SPIROU and ESPADONS (optical high-resolution spectro-polarimeter) data on a larger sample of young stars is foreseen. Follow-up observations may be obtained during the course of the PhD in particular with CRIRES+, GRAVITY+ and/or ERIS to map the large scale jets/outflows associated with the sources.