Rotation of the asymptotic giant branch star R Doradus
Artikel i vetenskaplig tidskrift, 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

Författare

Wouter Vlemmings

Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik, Galaktisk astrofysik

Theo Khouri

Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik, Galaktisk astrofysik

Elvire De Beck

Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik, Galaktisk astrofysik

Hans Olofsson

Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik, Galaktisk astrofysik

G. Garcia-Segura

Universidad Nacional Autonoma de Mexico

E. Villaver

Universidad Autonoma de Madrid (UAM)

A. Baudry

Universite de Bordeaux

E. M. L. Humphreys

European Southern Observatory Santiago

Matthias Maercker

Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik, Galaktisk astrofysik

S. Ramstedt

Uppsala universitet

Astronomy and Astrophysics

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

Vol. 613 L4

Ämneskategorier

Subatomär fysik

Astronomi, astrofysik och kosmologi

Strömningsmekanik och akustik

DOI

10.1051/0004-6361/201832929