A VLTI view of Massive Young Stellar Objects

Abstract: The formation of massive stars, objects with masses larger than eight times solar, is central to stellar astronomy and galactic evolution. In recent years, significant progress has been made in understanding the formation of high-mass young stellar objects (MYSOs; i.e. M∗ ≥ 8 M⊙, Lbol ≥ 5 x 103 L⊙. The latest observational and theoretical studies present evidence that HMYSOs are born the same way as their low-mass counterparts, via disc accretion rather than through the coalescence of lower mass stars (Rosen+ 2019; Klassen+ 2016; Kraus+ 2010). While massive protostellar discs have been established, little is known about how they eventually disperse and how this is linked to the central protostar. A recent interferometric study at mid-infrared wavelengths (VLTI/MIDI) has shown substructures in the discs of 8 HMYSOs, and one source showed a spiral-gap structure (Frost et al. 2021). These substructures could result from a forming companion; thus, understanding their formation is vital since massive stars have a high binary fraction. Moreover, investigating their inner structure, where the mass transfer to the protostar occurs, gives us insights into determining the physical and dynamic characteristics and the accretion/ejection processes in HMYSOs. In this talk, I will present our results on a sample of MYSOs using VLTI/GRAVITY (operating in K-band) and discuss the continuum and the gas (Brγ, Na I and CO lines) of their inner disc a few au from the star.