ALMA observations of TiO2 around VY Canis Majoris
Journal article, 2015
Context. Titanium dioxide, TiO2, is a refractory species that could play a crucial role in the dust-condensation sequence around oxygen-rich evolved stars. To date, gas phase TiO2 has been detected only in the complex environment of the red supergiant VY CMa. Aims. We aim to constrain the distribution and excitation of TiO2 around VY CMa in order to clarify its role in dust formation. Methods. We analyse spectra and channel maps for TiO2 extracted from ALMA science verification data. Results. We detect 15 transitions of TiO2, and spatially resolve the emission for the first time. The maps demonstrate a highly clumpy, anisotropic outflow in which the TiO2 emission likely traces gas exposed to the stellar radiation field. An accelerating bipolar-like structure is found, oriented roughly east-west, of which the blue component runs into and breaks up around a solid continuum component. A distinct tail to the south-west is seen for some transitions, consistent with features seen in the optical and near-infrared. Conclusions. 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.
Stars: mass-loss
Submillimeter: stars
Supergiants
Circumstellar matter
Stars: individual: VY Canis Majoris
Author
Elvire De Beck
Chalmers, Earth and Space Sciences, Onsala Space Observatory
Wouter Vlemmings
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
Sebastien Muller
Chalmers, Earth and Space Sciences, Onsala Space Observatory
John H Black
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
Eamon O Gorman
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
A. M. S. Richards
University of Manchester
A. Baudry
Centre national de la recherche scientifique (CNRS)
Laboratoire d'Astrophysique de Bordeaux
Matthias Maercker
Chalmers, Earth and Space Sciences, Onsala Space Observatory
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
L. Decin
University of Amsterdam
KU Leuven
E. M. Humphreys
European Southern Observatory (ESO)
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 580 A36Magnetic fields and the outflows during the formation and evolution of stars (OUTFLOWMAGN)
European Commission (EC) (EC/FP7/614264), 2014-05-01 -- 2019-04-30.
Subject Categories
Astronomy, Astrophysics and Cosmology
Roots
Basic sciences
Infrastructure
Onsala Space Observatory
DOI
10.1051/0004-6361/201525990