Bibcode
García-Segura, G.; Villaver, E.; Langer, N.; Yoon, S.-C.; Manchado, A.
Referencia bibliográfica
The Astrophysical Journal, Volume 783, Issue 2, article id. 74, 8 pp. (2014).
Fecha de publicación:
3
2014
Revista
Número de citas
65
Número de citas referidas
60
Descripción
We have computed new stellar evolution models that include the effects
of rotation and magnetic torques under different hypotheses. The goal is
to test whether a single star can sustain the rotational velocities
needed in the envelope for magnetohydrodynamical(MHD) simulations to
shape bipolar planetary nebulae (PNe) when high mass-loss rates take
place. Stellar evolution models with main sequence masses of 2.5 and 5 M
☉ and initial rotational velocities of 250 km
s–1 have been followed through the PNe formation phase.
We find that stellar cores have to be spun down using magnetic torques
in order to reproduce the rotation rates observed for white dwarfs.
During the asymptotic giant branch phase and beyond, the magnetic
braking of the core has a practically null effect on increasing the
rotational velocity of the envelope since the stellar angular momentum
is efficiently removed by the wind. We have also tested the best
possible case scenarios in rather non-physical contexts to give enough
angular momentum to the envelope. We find that we cannot get the
envelope of a single star to rotate at the speeds needed for MHD
simulations to form bipolar PNe. We conclude that single stellar
rotators are unlikely to be the progenitors of bipolar PNe under the
current MHD model paradigm.
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