ALMA observations of TiO2 around VY Canis Majoris
Artikel i vetenskaplig tidskrift, 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
Författare
Elvire De Beck
Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium
Wouter Vlemmings
Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik
Sebastien Muller
Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium
John H Black
Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik
Eamon O Gorman
Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik
A. M. S. Richards
University of Manchester
A. Baudry
Centre national de la recherche scientifique (CNRS)
Laboratoire d'Astrophysique de Bordeaux
Matthias Maercker
Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium
Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik
L. Decin
Universiteit Van 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)
Europeiska kommissionen (EU) (EC/FP7/614264), 2014-05-01 -- 2019-04-30.
Ämneskategorier
Astronomi, astrofysik och kosmologi
Fundament
Grundläggande vetenskaper
Infrastruktur
Onsala rymdobservatorium
DOI
10.1051/0004-6361/201525990