Bibcode
Garcia-Segura, G.; Villaver, E.; Langer, N.; Yoon, S. C.; Manchado, A.
Referencia bibliográfica
Asymmetrical Planetary Nebulae VI conference, Proceedings of the conference held 4-8 November, 2013. Edited by C. Morisset, G. Delgado-Inglada and S. Torres-Peimbert. Online at http://www.astroscu.unam.mx/apn6/PROCEEDINGS/,2id. #8
Fecha de publicación:
4
2014
Número de citas
0
Número de citas referidas
0
Descripción
We have computed new stellar evolution models that include the effects
of rotation and magnetic torques under different hypothesis. The goal is
to test if a single star can sustain in the envelope the rotational
velocities needed for the magneto hydrodynamical (MHD) simulations to
shape bipolar Planetary Nebulae (PNe) when the high mass-loss rates take
place. Stellar evolution models with main sequence masses of 2.5 and 5
Mo, and initial rotational velocities of 250 km/s have been followed all
the way to 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 in increasing the rotational velocity of the envelope since
the stellar angular momentum is removed efficiently by the wind. We
have, as well, tested 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 rotating at the
speeds needed by the 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.