Speaker
Description
Jets and winds are the result of the conservation of angular momentum in forming stars. How these components are launched and how they impact the gas within the innermost regions of these objects remains vastly unknown, specially in the case of the rare and distant massive stars. MWC 349A is a massive star that presents a circumstellar disk which rotates following a Keplerian law, and an ionized wind that is launched from the disk surface. In the last years, ALMA observations of the strong maser emission of hydrogen radio recombination lines (RRLs) obtained toward this system have provided a detailed picture of its ionized environment with an accuracy down to a few AU scales. The analysis of unresolved RRL emission with our 3D non-LTE radiative transfer model MORELI has unveiled a high velocity ionized jet launched from a rotating disk and engulfed within the wind, consistent with magneto-hydrodynamical (MHD) wind models. This result has been subsequently confirmed by additional ALMA observations of the H26? maser in the most extended configuration of the array with a resolution of 0.02”, which resolves the RRL emission for the first time. The resolved emission delineates the disk and the MHD wind and jet, and the model constrains their mass loss, energy and rotation. Our results show the huge potential of RRL masers as powerful probes of the innermost ionized regions and of the high-velocity jets from massive stars. In addition, we present predictions of RRL emission at the frequencies covered by the upcoming SKA telescope. These observations will allow us to characterise the ionized material from the outermost parts of the disk and recover the full 3D structure of the wind, providing stringent constraints to its launching mechanism and its impact on the lifetimes of disks around massive stars.
