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arXiv · 1608.03271

ALMA observations of the vibrationally-excited rotational CO transition $v=1, J=3-2$ towards five AGB stars

T. Khouri·W. H. T. Vlemmings·S. Ramstedt·R. Lombaert·M. Maercker·E. De Beck
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Abstract

We report the serendipitous detection with ALMA of the vibrationally-excited pure-rotational CO transition $v=1, J=3-2$ towards five asymptotic giant branch (AGB) stars, $o$ Cet, R Aqr, R Scl, W Aql, and $\pi^1$ Gru. The observed lines are formed in the poorly-understood region located between the stellar surface and the region where the wind starts, the so-called warm molecular layer. We successfully reproduce the observed lines profiles using a simple model. We constrain the extents, densities, and kinematics of the region where the lines are produced. R Aqr and R Scl show inverse P-Cygni line profiles which indicate infall of material onto the stars. The line profiles of $o$ Cet and R Scl show variability. The serendipitous detection towards these five sources shows that vibrationally-excited rotational lines can be observed towards a large number of nearby AGB stars using ALMA. This opens a new possibility for the study of the innermost regions of AGB circumstellar envelopes.

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T. Khouri, W. H. T. Vlemmings, S. Ramstedt, R. Lombaert, M. Maercker, E. De Beck. 2016-08-10. ALMA observations of the vibrationally-excited rotational CO transition $v=1, J=3-2$ towards five AGB stars. https://doi.org/10.1093/mnrasl/slw161

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