Related papers: On an Early - Post-AGB Instability
Late asymptotic giant branch (AGB) and early post-AGB stars which are progenitors of planetary nebulae lose mass at extremely high rate, in what is termed a superwind. We show that the existence of this superwind during the post-AGB phase…
Intense mass loss through cool, low-velocity winds is a defining characteristic of low-to-intermediate mass stars during the asymptotic giant branch (AGB) evolutionary stage. Such winds return up ~80% of the initial stellar mass to the…
The winds observed around asymptotic giant branch (AGB) stars are generally attributed to radiation pressure on dust, which is formed in the extended dynamical atmospheres of these pulsating, strongly convective stars. Current…
A popular self--enrichment scenario for the formation of globular clusters assumes that the abundance anomalies shown by the stars in many clusters are due to a second stage of star formation occurring from the matter lost by the winds of…
The post-asymptotic giant branch (AGB) phase is arguably one of the least understood phases of the evolution of low- and intermediate- mass stars. The recent post-AGB evolutionary sequences computed by Miller Bertolami (2016) are at least…
In this paper, a time-dependent magnetohydrodynamic model is presented which aimed at understanding the superwind production by an evolved AGB star and the consecutive formation of a dense circumstellar envelope around it. We know…
The commonly accepted mechanism governing the formation of the nascent wind in oxygen-rich AGB stars combines an initial boost above the photosphere, given by shock waves resulting from stellar pulsations and convective cell granulation,…
We examine the envelope properties of asymptotic giant branch (AGB) stars as they evolve on the upper AGB and during the early post-AGB phase. Due to the high mass loss rate, the envelope mass decreases by more than an order of magnitude.…
The winds of cool luminous AGB stars are commonly assumed to be driven by radiative acceleration of dust grains which form in the extended atmospheres produced by pulsation-induced shock waves. The dust particles gain momentum by absorption…
Winds of AGB stars are thought to be driven by a combination of pulsation-induced shock waves and radiation pressure on dust. In dynamic atmosphere and wind models, the stellar pulsation is often simulated by prescribing a simple sinusoidal…
We summarise the evolution and nucleosynthesis in AGB and Super-AGB stars. We then examine the major sources of uncertainty, especially mass-loss.
AGB stars, the precursors of Planetary Nebulae, exhibit high rates of mass loss and eject material in the form of a slow (10-20 km/s), dusty molecular wind. The general belief that the dust component of AGB circumstellar envelopes have…
When intermediate mass stars reach their last stages of evolution they show pronounced oscillations. This phenomenon happens when these stars reach the so-called Asymptotic Giant Branch (AGB), which is a region of the Hertzsprung-Russell…
Variability and mass-loss are common phenomena in massive OB-type stars. It is argued that they are caused by violent strange mode instabilities identified in corresponding stellar models. We present a systematic linear stability analysis…
In this chapter the focus is on the properties of post-Asymptotic Giant Branch (post-AGB) stars in binary systems. Their Spectral Energy Distributions (SEDs) are very characteristic: they show a near-infrared excess, indicative of the…
The intricate interplay of atmospheric shock waves and a complex, variable radiation field with non-equilibrium dust formation presents a considerable challenge to self-consistent modelling of atmospheres and winds of AGB stars.…
Low- and intermediate-mass stars eject much of their mass during the late, red giant branch (RGB) phase of evolution. The physics of their strong stellar winds is still poorly understood. In the standard model, stellar pulsations extend the…
Almost all stars in the 1-8 Msun range evolve through the Asymptotic Giant Branch (AGB), preplanetary nebula (PPN) and planetary nebula (PN) evolutionary phases. Most stars that leave the main sequence in a Hubble time will end their lives…
A review is presented of the most relevant results obtained in the last few years on this rare class of astronomical sources. Multi-wavelength analysis of an increasing number of post-AGB stars reveal that they constitute a more…
Mass loss is a crucial component in stellar evolution models, since it largely determines the rate of evolution at the later stages of a star's life. The dust-driven outflows from AGB stars are particularly important in this regard.…