We model the nucleosynthesis during a radiative interpulse phase of a rotating 3 M⊙ Asymptotic Giant Branch (AGB) star. We find an enhanced production of the neutron source species 13C compared to non-rotating models due to shear mixing of protons and 12C at the core-envelope interface. We estimate that the resulting total production of heavy elements by slow neutron capture (s-process) is too low to account for most observations. This due to the fact that rotationally induced mixing during the interpulse phase causes a pollution of the 13C pocket layer with the neutron poison 14N. As a result we find a maximum neutron exposure of τmax = 0.04 mbarn–1 in the s-process layer of our solar metallicity model with rotation. This is about a factor of 5 … 10 less than required to reproduce the observed stellar s-process abundance patterns. We compare our results with models that include hydrodynamic overshooting mixing, and with simple parametric models including the combined effects of overshooting and mixing in the interpulse. Within the parametric model a range of mixing efficiencies during the interpulse phase correlates with a spread in the s-process-efficiency. Such a spread is observed in AGB and post-AGB stars as well as in pre-solar SiC grains.

Planetary nebulae are formed as the result of the interaction between a slow stellar wind from the asymptotic giant branch progenitor and a later-developed fast outflow from the central star. Many of the morphological and kinematic properties of planetary nebulae have been successfully explained by this interacting stellar winds model. The observed diverse morphologies of planetary nebulae can also be understood if the slow wind is not spherically symmetric. However, new observational features such as collimated outflows and multi-polar lobes suggest that the fast wind may be non-isotropic and time variable. The possible roles of magnetic fields and rotation may play in the formation of these features are discussed.

The observational evidence for non-spherical winds of rapidly rotating hot and cool stars is presented. Models to explain equatorially enhanced winds of AGB stars and of hot B[e]-supergiants are discussed. We distinguish between models with a disk due to an increased equatorial mass flux and those with a disk due to spherical mass loss with a wind flowing towards the equatorial plane.

Most LBVs and Ofpe/WN9 stars in the Milky Way and in the Magellanic Clouds are surrounded by associated circumstellar nebulae which have been ejected in some previous phase of their evolution. These nebulae are the fossil record of the interactions of previous winds and of the violent ejections in which the stars most likely have shed their outer layers. The study of the morphology, kinematics and chemical composition of the ejected material has allowed us to gain deep insight in the ejection and shaping mechanism, and in the properties of the central star at the moment of the ejection. In this review I will address how ejected nebulae are providing independent supporting evidence that rotation plays a major role in the evolution of massive stars.

Rotation appears as a dominant effect in massive star evolution. It largely affects all the model outputs: inner structure, tracks, lifetimes, isochrones, surface compositions, blue to red supergiant ratios, etc. At lower metallicities, the effects of rotational mixing are larger; also, more stars may reach critical velocity, even if the initial distribution of rotational velocities is the same.

The dynamical shear instability is an important mixing process in the advanced stages of the evolution of massive stars. We calculated different models of 15 M⊙ with an initial rotational velocity, vini = 300 km/s to investigate its efficiency. We found that the dynamical shear instability has a timescale shorter than oxygen burning timescale and that it slightly enlarges the convective zones and smoothens the omega gradients throughout the evolution. However, its effect is too localized to slow down the core of the star.

A calibration of the O spectral types and luminosity classes has been plotted onto evolutionary tracks and isochrones for both nonrotating models and models with an initial rotational velocity of 300 km sec–1. Differences in the physical interpretation of the spectral types between the two cases have been investigated.

The characteristic signature of Be Stars is the Balmer line emission understood to arise in a circumstellar disk. Unlike the accretion disks of protostars or mass-exchange binary systems, the evolved and generally single or wide-binary status of Be Stars seems to require that its disk must form from mass ejection (a.k.a. decretion) from the star itself. In this paper, I use analogies with launching orbital satellites to discuss two candidate processes (radiation, pulsation) for driving such orbital mass ejection, with particular emphasis on the role of the rapid, possibly near-critical, rotation of Be Stars in facilitating the formation of their signature disks.

There is extensive evidence that the radiatively driven stellar winds of OB-type stars are not the steady, smooth outflows envisioned in classical models, but instead exhibit extensive structure and variability on a range of temporal and spatial scales. We examine the possible role of stellar magnetic fields in forming large-scale wind structure. It is based on numerical magnetohydrodynamic (MHD) simulations of the interaction of a line-driven flow with an assumed stellar dipole field.

Unlike previous fixed-field analyses, the MHD simulations here take full account of the dynamical competition between field and flow, and thus apply to a full range of magnetic field strength, and within both closed and open magnetic topologies. A key result is that the overall degree to which the wind is influenced by the field depends largely on a single, dimensionless, ‘wind magnetic confinement parameter’, η∗ (= B2eqR2∗/Ṁv∞), which characterizes the ratio between magnetic field energy density and kinetic energy density of the wind.

We extend these MHD simulations to include field-aligned stellar rotation. The results indicate that a combination of the magnetic confinement parameter and the rotation rate as a fraction of the ‘critical’ rotation now determine the global properties of the wind. For models with strong magnetic confinement, rotation can limit the extent of the last closed magnetic loop, and lead to episodic mass ejections that break through the close loop and are carried outward with a slow, dense, equatorial outflow. Our 2-D numerical simulations indicate that the magnetic fields provide excessive amount of angular momentum to the wind preventing the formation of a Keplerian disk.

There are three important effects in optically thin line-driven winds that have been shown to inhibit the equatorial compression inherent in the wind-compressed disk model:

1) gravity darkening, which concentrates the driving flux over the poles,

2) stellar oblateness, which rotates the flux vectors poleward, and

3) nonisotropic opacity, which rotates the force vectors poleward.

The first two of these effects tend to yield fairly spherical winds, while the last one actually reverses the wind compression and should generate prolate winds. This poster argues that this third mechanism is not present for multiline scattering in Wolf-Rayet winds. Hence, it is argued that rotating optically thick line-driven winds should have a more spherical UV photosphere, especially for CAK α ≅ 2/3. However, owing to flux migration from polar to equatorial regions, such winds should have an even more prolate optical photosphere.

Based on the viscous decretion disk model for Be Stars, we study the effect of the torque from the star on the Be star disk, using a 3-D smoothed particle hydrodynamics code and turning on and off the mass ejection from the star. We find that, after the mass ejection is shut off, the innermost part of the disk begins to accrete and the accreting part gradually propagates outward. We also find that the Be disk in misaligned binaries precesses in a retrograde sense when no mass is supplied from the star. If the mass supply is resumed for such a disk, an inner disk is formed with its rotation axis misaligned with that of the outer disk. By the interaction between the inner and outer disks, the outer disk rapidly changes its direction to that of the inner disk.

We discuss the first available binary evolution models which include up-to-date rotational physics for both components, as well as angular momentum accretion and spin-orbit coupling. These models allow a self-consistent computation of the mass transfer efficiency during Roche-lobe overflow phases, and a determination of the transition from quasi-conservative to non-conservative evolution. Applications to massive binary systems lead to predictions for the spin rates of compact objects in binaries, and for the occurrence of gamma-ray bursts from collapsars in binaries. Rotational effects in accreting white dwarfs are found to stabilise the shell burning and decrease the carbon abundance in progenitor models for Chandrasekhar-mass Type Ia supernovae, and to potentially avoid a detonation of the white dwarf within the sub-Chandrasekhar mass scenario.

Cataclysmic Variables are binary star systems and so are closely connected to the subject of this meeting. The stars revolve around the center of mass of the system. The gas lost by the secondary through the inner Lagrangian point enters the Roche lobe of the white dwarf with the angular momentum of the L1 point and, therefore, forms an accretion disk which rotates around the white dwarf. The gas must lose angular momentum to fall onto the white dwarf, and the white dwarf itself must rotate as it accretes infalling material and angular momentum and is gradually spun up. We will review what is known about these phenomena, and emphasize the new results about the white dwarfs that have been learned in the past few years.

White dwarfs rotate. The angular momentum in single white dwarfs must originate early in the life of the star, but also must be modified (and perhaps severely modified) during the many stages of evolution between birth as a main–sequence star and final appearance as a white dwarf. Observational constraints on the rotation of single white dwarf stars come from traditional spectroscopy and from asteroseismology, with the latter providing hints of angular velocity with depth. Results of these observational determinations, that white dwarfs rotate with periods ranging from hours to days (or longer), tells us that the processes by which angular momentum is deposited and/or drained from the cores of AGB stars are complex. Still, one can place strong limits on these processes by considering relatively simple limiting cases for angular momentum evolution in prior stages, and on subsequent angular momentum evolution in the white dwarfs. These limiting-case constraints will be reviewed in the context of the available observations.

Classical studies of accreting white dwarfs have assumed spherical symmetry. However, it is believed that in close binary systems the transfered matter carries angular momentum to spin up the accreting star. Here, we present preliminary results of CO white dwarf models which accrete helium rich matter with effects of rotation considered, in the context of the Sub-Chandrasekhar mass scenario for Type Ia supernovae.

Previous investigations on hydrogen-rich white dwarfs generally yield only very small rotational velocities (v sin i). We have analyzed line profiles in high-resolution optical spectra of eight hydrogen-deficient (pre-) white dwarfs and find deviations from the dominant Stark line broadening in five cases which, interpreted as an effect of stellar rotation, indicate projected rotational velocities of 40 – 70 km s–1. For the three least luminous stars upper limits of v sin i = 15 – 25 km s–1 could be derived only. The resulting velocities correlate with luminosity and mass. However, since the mass-loss rate is correlated to the luminosity of a star, the observed line profiles may be affected by a stellar wind as well. In the case of RX J2117.1+3412, this would solve discrepancies to results of pulsational modeling (v sin i ≈ 0).

AA Dor (LB 3459) is an eclipsing, close binary (P = 0.26 d) consisting of a sdOB primary star and an unseen secondary with an extraordinary small mass. The secondary is possibly a former planet which may have survived a common-envelope phase and has even gained mass.

In order to investigate on an existing discrepancy between the components' mass derived from NLTE spectral analysis and subsequent comparison to evolutionary tracks and masses derived from radial-velocity and the eclipse curves, we performed phase-resolved high-resolution and high-SN spectroscopy with the UVES attached to the ESO VLT. from the obtained spectra, we have determined AA Dor's orbital parameters (P = 22 600.702±0.005 sec, A = 39.19±0.05 km s–1, T0 = 2451917.152690) and the rotational velocity (vrot = 47±5 km s–1) of the primary.

In the quest to understand the origin of Planetary Nebula (PN) morphology, correlations have been sought between the nebular shapes and the evolutionary status of the central stars. Several of the mechanisms proposed to explain asymmetric shapes have a direct link with the central star's evolutionary status. Among the possible mechanisms invoked to produce asymmetric PNs, stellar rotation is certainly an effective one, as several hydrodynamics models have shown. In this work we present Space Telescope Imaging Spectrograph (STIS) UV spectra of a sample of bright LMC PNs and their central stars. LMC PNs distances are known, thus the observed characteristics of the stars translate into absolute physical quantities readily, and provide the safest dataset for theory-observation comparisons. We are planing to fit stellar models to the observed spectra using black-body SEDs and synthetic photometry to estimate stellar temperature and reddening. We are going to use the stellar evolutionary tracks to compare the post-AGB age with the dynamical age from the nebula. P-Cygni profiles will be analyzed in order to determine an approximation of the mass loss rate. Stellar characteristics will be related to the morphology of the nebulae observed by our group with HST STIS optical slitless spectroscopy.

We use the rotating stellar models described in the paper by A. Maeder & G. Meynet in this volume to consider the effects of rotation on the evolution of the most massive stars into and during the Wolf–Rayet phase, and on the post-Main Sequence evolution of intermediate mass stars. The two main results of this discussion are the following. First, we show that rotating models are able to account for the observed properties of the Wolf–Rayet stellar populations at solar metallicity. Second, at low metallicities, the inclusion of stellar rotation in the calculation of chemical yields can lead to a longer time delay between the release of oxygen and nitrogen into the interstellar medium following an episode of star formation, since stars of lower masses (compared to non-rotating models) can synthesize primary N. Qualitatively, such an effect may be required to explain the relative abundances of N and O in extragalactic metal–poor environments, particularly at high redshifts.