Monday, January 21, 2013

1301.4344 (T. Kaminski et al.)

Pure rotational spectra of TiO and TiO_2 in VY Canis Majoris    [PDF]

T. Kaminski, C. A. Gottlieb, K. M. Menten, N. A. Patel, K. H. Young, S. Brunken, H. S. P. Muller, M. C. McCarthy, J. M. Winters, L. Decin
We report the first detection of pure rotational transitions of TiO and TiO_2 at (sub-)millimeter wavelengths towards the red supergiant VY CMa. A rotational temperature, T_rot, of about 250 K was derived for TiO_2. Although T_rot was not well constrained for TiO, it is likely somewhat higher than that of TiO_2. The detection of the Ti oxides confirms that they are formed in the circumstellar envelopes of cool oxygen-rich stars and may be the "seeds" of inorganic-dust formation, but alternative explanations for our observation of TiO and TiO_2 in the cooler regions of the envelope cannot be ruled out at this time. The observations suggest that a significant fraction of the oxides is not converted to dust, but instead remains in the gas phase throughout the outflow.
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