ALMA observations of TiO 2 around VY CMa

Elvire de Beck , Wouter Vlemmings , Sébastien Muller (1, 2, 3) , John H. Black (4) , Eamon O'Gorman (5) , Anita M. S. Richards (6) , Alain Baudry (7) , Matthias Maercker , Leen Decin , Elizabeth M. Humphreys

1 OCIF - Objets communicants pour l'Internet du futur
2 RSM - Département Réseaux, Sécurité et Multimédia
3 S'nT - Security, Reliability and Trust Interdisciplibary Research Centre
4 HSU - Humboldt State University
5 Department of Biology
6 Cardiff University
7 FORMATION STELLAIRE 2016

Titanium dioxide, TiO2, is a refractory species that could play a crucial role in the dust-condensation sequence around oxygen-rich evolved stars. We present and discuss the detections of 15 emission lines of TiO2 with ALMA in the complex environment of the red supergiant VY CMa. The observations reveal a highly clumpy, anisotropic outflow in which the TiO2 emission likely traces gas exposed to the stellar radiation field. We find evidence for a roughly east-west oriented, accelerating bipolar-like structure, of which the blue component runs into and breaks up around a solid continuum component. We see a distinct tail to the south-west for some transitions, consistent with features seen in the optical and near-infrared. We find that a significant fraction of TiO2 remains in the gas phase outside the dust-formation zone and suggest that this species might play only a minor role in the dust-condensation process around extreme oxygen-rich evolved stars like VY CMa.

Domaines: Astrophysique galactique [astro-ph.GA]

Elvire de Beck, Wouter Vlemmings, Sébastien Muller, John H. Black, Eamon O'Gorman, et al.. ALMA observations of TiO 2 around VY CMa. Journal of Physics: Conference Series, 2016, 728 (2), pp.id. 022009. ⟨10.1088/1742-6596/728/2/022009⟩. ⟨hal-01435295⟩