Headwind: Modelling Mass Loss of AGB Stars, Against All Odds

نویسنده

  • Susanne Höfner
چکیده

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. Nevertheless it is clear that realistic models predicting mass loss rates and synthetic spectra are crucial for our understanding of this important phase of stellar evolution. While a number of questions are still open, significant progress has been achieved in recent years. In particular, self-consistent models for atmospheres and winds of C-stars have reached a level of sophistication which allows direct quantitative comparison with observations. In the case of stars with C/O < 1, however, recent work points to serious problems with the dust-driven wind scenario. This contribution analyzes the basic ingredients of this scenario with analytical estimates, focusing on dust formation, non-grey effects, and differences between C-rich and O-rich environments, as well as discussing the status of detailed dynamical wind models and current trends in this field.

برای دانلود رایگان متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Circumstellar molecular line emission from S-type AGB stars: Mass-loss rates and SiO abundances

Aims. The main aim is to derive reliable mass-loss rates and circumstellar SiO abundances for a sample of 40 S-type AGB stars based on new multi-transitional CO and SiO radio line observations. In addition, the results are compared to previous results for M-type AGB stars and carbon stars to look for trends with chemical type. Methods. The circumstellar envelopes are assumed to be spherically s...

متن کامل

Mg and Al Yields from Low and Intermediate Mass AGB stars

We investigate the production of aluminium and the heavy magnesium isotopes in asymptotic giant branch (AGB) models. We evolve models with a wide range in initial mass (1 > (M⊙) > 6) and composition (Z = 0.02,0.008,0.004). We evolve the models from the pre-main sequence, through all intermediate stages including the core helium flash, to near the end of the thermally-pulsing AGB phase. We then ...

متن کامل

Mass Loss Evolution and the Formation of Detached Shells around TP-AGB Stars

Context. The origin of the so called ’detached shells’ around AGB stars is not fully understood, but two common hypotheses state that these shells form either through the interaction of distinct wind phases or an eruptive mass loss associated with a He-shell flash. We present a model of the formation of detached shells around thermal pulse asymptotic giant branch (TP-AGB) stars, based on detail...

متن کامل

Infrared Spectroscopic Study of a Selection of AGB and Post-AGB Stars

We present here near-infrared spectroscopy in the H and K bands of a selection of nearly 80 stars that belong to various AGB types, namely S type, M type and SR type. This sample also includes 16 Post-AGB (PAGB) stars. From these spectra, we seek correlations between the equivalent widths of some important spectral signatures and the infrared colors that are indicative of mass loss. Repeated sp...

متن کامل

Mass-loss rates and luminosity functions of dust-enshrouded AGB stars and red supergiants in the LMC

A radiative transfer code is used to model the spectral energy distributions of 57 mass-losing Asymptotic Giant Branch (AGB) stars and red supergiants (RSGs) in the Large Magellanic Cloud (LMC) for which ISO spectroscopic and photometric data are available. As a result we derive mass-loss rates and bolometric luminosities. A gap in the luminosity distribution around Mbol = −7.5 mag separates AG...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

عنوان ژورنال:

دوره   شماره 

صفحات  -

تاریخ انتشار 2007