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arXiv · 2211.13085

First spatially resolved Na I and He I transitions towards an MYSO. Finding new tracers for the gaseous star/disc interface

Evgenia Koumpia·M. Koutoulaki·W. -J. de Wit·R. D. Oudmaijer·A. J. Frost·S. L. Lumsden·J. M. Pittard
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Abstract

With steady observational advances, the formation of massive stars is being understood in more detail. Numerical models are converging on a scenario where accretion discs play a key role. Direct observational evidence of such discs at a few au scales is scarce, due to the rarity of such objects and the observational challenges, including the lack of adequate diagnostic lines in the near-IR. We present the analysis of K-band spectro-interferometric observations toward the Massive Young Stellar Object IRAS 13481-6124, which is known to host an accreting dusty disc. Using GRAVITY on the VLTI, we trace the crucial au-scales of the warm inner interface between the star and the accretion dusty disc. We detect and spatially resolve the Na I doublet and He I transitions towards an object of this class for the first time. The new observations in combination with our geometric models allowed us to probe the smallest au-scales of accretion/ejection around an MYSO. We find that Na I originates in the disc at smaller radii than the dust disc and is more compact than any of the other spatially resolved diagnostics (Br$\gamma$, He I, and CO). Our findings suggest that Na I can be a new powerful diagnostic line in tracing the warm star/disc accreting interface of forming (massive) stars, while the similarities between He I and Br$\gamma$ point towards an accretion/ejection origin of He I

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Evgenia Koumpia, M. Koutoulaki, W. -J. de Wit, R. D. Oudmaijer, A. J. Frost, S. L. Lumsden, J. M. Pittard. 2022-11-23. First spatially resolved Na I and He I transitions towards an MYSO. Finding new tracers for the gaseous star/disc interface. https://doi.org/10.1093/mnrasl%2Fslac151

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