Rotation of the asymptotic giant branch star R Doradus
Journal article, 2018

High-resolution observations of the extended atmospheres of asymptotic giant branch (AGB) stars can now directly be compared to the theories that describe stellar mass loss. Using Atacama Large Millimeter/submillimeter Array (ALMA) high angular resolution (30 x 42 mas) observations, we have for the first time resolved stellar rotation of an AGB star, R Dor. We measure an angular rotation velocity of omega(R) sin i = (3.5 +/- 0.3) x 10(-9) rad s(-1), which indicates a rotational velocity of vertical bar nu(rot) sin i vertical bar = 1.0 +/- 0.1 km s(-1) at the stellar surface (R-* = 31.2 mas at 214 GHz). The rotation axis projected on the plane of the sky has a position angle Phi = 7 +/- 6 degrees. We find that the rotation of R Dor is two orders of magnitude faster than expected for a solitary AGB star that will have lost most of its angular momentum. Its rotational velocity is consistent with angular momentum transfer from a close companion. As a companion has not been directly detected, we suggest R Dor has a low-mass, close-in companion. The rotational velocity approaches the critical velocity, set by the local sound speed in the extended envelope, and is thus expected to affect the mass-loss characteristics of R Dor.

stars: AGB and post-AGB

stars: rotation

Author

Wouter Vlemmings

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics, Galactic Astrophysics

Theo Khouri

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics, Galactic Astrophysics

Elvire De Beck

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics, Galactic Astrophysics

Hans Olofsson

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics, Galactic Astrophysics

G. Garcia-Segura

Universidad Nacional Autonoma de Mexico

E. Villaver

Universidad Autonoma de Madrid (UAM)

A. Baudry

University of Bordeaux

E. M. L. Humphreys

European Southern Observatory Santiago

Matthias Maercker

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics, Galactic Astrophysics

S. Ramstedt

Uppsala University

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 613 L4

Magnetic fields and the outflows during the formation and evolution of stars (OUTFLOWMAGN)

European Commission (FP7), 2014-05-01 -- 2019-04-30.

Subject Categories

Subatomic Physics

Astronomy, Astrophysics and Cosmology

Fluid Mechanics and Acoustics

DOI

10.1051/0004-6361/201832929

More information

Latest update

9/12/2018