Rotational spectra of vibrationally excited AlO and TiO in oxygen rich stars. (arXiv:2010.06485v1 [astro-ph.SR])

Rotational spectra of vibrationally excited AlO and TiO in oxygen rich stars. (arXiv:2010.06485v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Danilovich_T/0/1/0/all/0/1">T. Danilovich</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gottlieb_C/0/1/0/all/0/1">C. A. Gottlieb</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Decin_L/0/1/0/all/0/1">L. Decin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Richards_A/0/1/0/all/0/1">A. M. S. Richards</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lee_K/0/1/0/all/0/1">K. L. K. Lee</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kaminski_T/0/1/0/all/0/1">T. Kaminski</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Patel_N/0/1/0/all/0/1">N. A. Patel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Young_K/0/1/0/all/0/1">K. H. Young</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Menten_K/0/1/0/all/0/1">K. M. Menten</a>

Rotational transitions in vibrationally excited AlO and TiO — two possible
precursors of dust — were observed in the 300 GHz range (1 mm wavelength)
towards the oxygen rich AGB stars R Dor and IK Tau with ALMA, and vibrationally
excited AlO was observed towards the red supergiant VY CMa with the SMA. The
$J=11 to 10$ transition of TiO in the $v=1~{rm{and}}~2$ levels, and the $N =
9 to 8$ transition in the $v=2$ level of AlO were identified towards R Dor;
the $J=11 to 10$ line of TiO was identified in the $v=1$ level towards IK Tau;
and two transitions in the $v=1~{rm{and}}~2$ levels of AlO were identified
towards VY CMa. The newly-derived high vibrational temperature of TiO and AlO
in R Dor of $1800 pm 200$ K, and prior measurements of the angular extent
confirm that the majority of the emission is from a region within
$lesssim2R_{star}$ of the central star. A full radiative transfer analysis of
AlO in R Dor yielded a fractional abundance of $sim$3% of the solar abundance
of Al. From a similar analysis of TiO a fractional abundance of $sim78$% of
the solar abundance of Ti was found. The observations provide indirect evidence
that TiO is present in a rotating disk close to the star. Further observations
in the ground and excited vibrational levels are needed to determine whether
AlO, TiO, and TiO$_2$ are seeds of the Al$_2$O$_3$ dust in R Dor, and perhaps
in the gravitationally bound dust shells in other AGB stars with low mass loss
rates.

Rotational transitions in vibrationally excited AlO and TiO — two possible
precursors of dust — were observed in the 300 GHz range (1 mm wavelength)
towards the oxygen rich AGB stars R Dor and IK Tau with ALMA, and vibrationally
excited AlO was observed towards the red supergiant VY CMa with the SMA. The
$J=11 to 10$ transition of TiO in the $v=1~{rm{and}}~2$ levels, and the $N =
9 to 8$ transition in the $v=2$ level of AlO were identified towards R Dor;
the $J=11 to 10$ line of TiO was identified in the $v=1$ level towards IK Tau;
and two transitions in the $v=1~{rm{and}}~2$ levels of AlO were identified
towards VY CMa. The newly-derived high vibrational temperature of TiO and AlO
in R Dor of $1800 pm 200$ K, and prior measurements of the angular extent
confirm that the majority of the emission is from a region within
$lesssim2R_{star}$ of the central star. A full radiative transfer analysis of
AlO in R Dor yielded a fractional abundance of $sim$3% of the solar abundance
of Al. From a similar analysis of TiO a fractional abundance of $sim78$% of
the solar abundance of Ti was found. The observations provide indirect evidence
that TiO is present in a rotating disk close to the star. Further observations
in the ground and excited vibrational levels are needed to determine whether
AlO, TiO, and TiO$_2$ are seeds of the Al$_2$O$_3$ dust in R Dor, and perhaps
in the gravitationally bound dust shells in other AGB stars with low mass loss
rates.

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