TY - JOUR
T1 - Magnetic field, dust and axisymmetrical mass loss on the asymptotic giant branch
AU - Soker, Noam
N1 - Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.
PY - 1998/10/1
Y1 - 1998/10/1
N2 - I propose a mechanism for axisymmetrical mass loss on the asymptotic giant branch (AGB) that may account for the axially symmetric structure of elliptical planetary nebulae. The proposed model operates for slowly rotating AGB stars, having angular velocities in the range of 10-4ωKep ≲ ω ≲ 10-2ωKep, where ωKep is the equatorial Keplerian angular velocity. Such angular velocities could be gained from a planet companion of mass ≳0.1MJupiter, which deposits its orbital angular momentum to the envelope at late stages, or even from single stars that are fast rotators on the main sequence. The model assumes that dynamo magnetic activity results in the formation of cool spots, above which dust forms much more easily. The enhanced magnetic activity towards the equator results in a higher dust formation rate there, and hence higher mass-loss rate. As the star ascends the AGB, both the mass-loss rate and magnetic activity increase rapidly, and hence the mass loss becomes more asymmetrical, with higher mass-loss rate closer to the equatorial plane.
AB - I propose a mechanism for axisymmetrical mass loss on the asymptotic giant branch (AGB) that may account for the axially symmetric structure of elliptical planetary nebulae. The proposed model operates for slowly rotating AGB stars, having angular velocities in the range of 10-4ωKep ≲ ω ≲ 10-2ωKep, where ωKep is the equatorial Keplerian angular velocity. Such angular velocities could be gained from a planet companion of mass ≳0.1MJupiter, which deposits its orbital angular momentum to the envelope at late stages, or even from single stars that are fast rotators on the main sequence. The model assumes that dynamo magnetic activity results in the formation of cool spots, above which dust forms much more easily. The enhanced magnetic activity towards the equator results in a higher dust formation rate there, and hence higher mass-loss rate. As the star ascends the AGB, both the mass-loss rate and magnetic activity increase rapidly, and hence the mass loss becomes more asymmetrical, with higher mass-loss rate closer to the equatorial plane.
KW - Circumstellar matter
KW - MHD
KW - Planetary nebulae: general
KW - Stars: AGB and post-AGB
KW - Stars: mass-loss
UR - http://www.scopus.com/inward/record.url?scp=0011077541&partnerID=8YFLogxK
U2 - 10.1046/j.1365-8711.1998.01884.x
DO - 10.1046/j.1365-8711.1998.01884.x
M3 - 文章
AN - SCOPUS:0011077541
VL - 299
SP - 1242
EP - 1248
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 4
ER -