Harm Jan Habing

Asymptotic giant branch stars

Preface Chapter 1: Introduction: H.J. Habing and H. Olofsson N.B.: This chapter is not yet completed! 1.1 Bits of history 1.2 The structure of AGB stars 1.3 Observational characteristics of AGB stars 1.4 Distinctive properties of AGB stars Chapter 2: Evolution, Nucleosynthesis and Pulsation: P. Wood and J. Lattanzio 2.1 Basic observational properties 2.2 Pre-AGB evolution 2.3 Stellar evolution on the AGB 2.4 Evolution beyond the AGB: planetary nebula nuclei and white dwarfs 2.5 Nucleosynthesis in AGB stars 2.6 Variability 2.7 Conclusions and outlook Chapter 3: Synthetic AGB Evolution: M. Groenewegen, P. Marigo 3.1 The role of synthetic evolutionary models 3.2 A historical overview 3.3 The main ingredients of a synthetic AGB model 3.4 Stellar yields 3.5 From one star to population synthesis 3.6 Observational constraints 3.7 conclusions and outlook Chapter 4: Atmospheres: B. Gustafsson and S. Hofner 4.1 Introduction 4.2 Observations 4.3 Physics and characteristic conditions 4.4 The microscopic state of matter 4.5 The radiation .eld 4.6 The modelling of AGB star atmospheres 4.7 Dynamics 4.8 Mass loss 4.9 Abundances and other fundamental paramters 4.10 Conclusions and outlook Chapter 5: Molecule and grain formation: T. Miller 5.1 Introduction 5.2 Chemical processes for molecule and dust formation 5.3 Detailed models- carbon-rich envelopes 5.4 Detailed models- oxygen-rich envelopes 5.5 Complications 5.6 Conclusions and outlook Chapter 6: Dynamics and instabilities in dusty winds: Y. Simis and P. Woitke 6.1 Introduction 6.2 Modelling the AGB wind 6.3 Instabilities and structure in the out.ow 6.4 Conclusions and outlook Chapter 7: Circumstellar envelopes: H. Olofsson 7.1 Introduction 7.2 A standard gas AGB-CSE 7.3 Circumstellar line observations 7.4 A standard dustAGB-CSE 7.5 Circumstellar dust observations 7.6 Morphology and kinematics of AGB-CSEs 7.7 Mass-loss rate estimators 7.8 Mass-loss rate 7.9 Conclusions and outlook Chapter 8: AGB stars as tracers of a galactic population: H.J. Habing and P.A. Whitelock 8.1 Introduction 8.2 The Milky Way galaxy and its companions 8.3 M31 and its companions 8.4 The remaining members of the Local Group 8.5 AGB stars in galaxies outside of the Local Group 8.6 Conclusions and outlook Chapter 9: AGB stars in Binaries and their Progeny: A. Jorissen 9.1 The binary-AGB connection 9.2 AGB stars in binary systems 9.3 Impact of binarity on intrinsic properties of AGB stars 9.4 The progeny of AGB stars in binary system 9.5 Conclusions and outlook Chapter 10: Post-AGB stars: C.Waelkens and R.Waters 10.1 Introduction 10.2 Observational de.nition of a post-AGB star 10.3 Observed properties of post-AGB stars: the central star 10.4 Observed properties of post-AGB stars: the envelope 10.5 Binary post-AGB stars 10.6 Confrontation of observations with theory 10.7 Conclusions and outlook Index List of acronyms Some biographical notes about the authors

Incidence and survival of remnant disks around main-sequence stars

We present photometric ISO 60 and 170 um measurements, complemented by some IRAS data at 60

A Spitzer mid-infrared spectral survey of mass-losing carbon stars in the Large Magellanic Cloud

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AGB stars in the Magellanic Clouds. II. The rate of star formation across the LMC

, of a sample of 84 nearby main-sequence stars of spectral class A, F, G and K in order to determine the incidence of dust disks around such main-sequence stars. Fifty stars were detected at 60

Lithium and zirconium abundances in massive Galactic O-rich AGB stars

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AGB stars in the Magellanic Clouds - I. The C/M ratio

; 36 of these emit a flux expected from their photosphere while 14 emit significantly more. The excess emission we attribute to a circumstellar disk like the ones around Vega and β Pictoris. Thirty four stars were not detected at all; the expected photospheric flux, however, is so close to the detection limit that the stars cannot have an excess stronger than the photospheric flux density at 60

Spitzer observations of acetylene bands in carbon-rich asymptotic giant branch stars in the Large Magellanic Cloud

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ISOGAL : A deep survey of the obscured inner Milky Way with ISO at 7 mu m and 15 mu m and with DENIS in the near-infrared

. Of the stars younger than 400 Myr one in two has a disk; for the older stars this is true for only one in ten. We conclude that most stars arrive on the main sequence surrounded by a disk; this disk then decays in about 400 Myr. Because (i) the dust particles disappear and must be replenished on a much shorter time scale and (ii) the collision of planetesimals is a good source of new dust, we suggest that the rapid decay of the disks is caused by the destruction and escape of planetesimals. We suggest that the dissipation of the disk is related to the heavy bombardment phase in our Solar System. Whether all stars arrive on the main sequence surrounded by a disk cannot be established: some very young stars do not have a disk. And not all stars destroy their disk in a similar way: some stars as old as the Sun still have significant disks.

Disappearance of stellar debris disks around main-sequence stars after 400 million years

We present a Spitzer Space Telescopespectroscopic survey of mass-losing carbon stars (and one oxygen-rich star) in the Large Magellanic Cloud. The stars represent the superwind phase on the Asymptotic Giant Branch, which forms a major source of dust for the interstellar medium in galaxies. The spectra cover the wavelength range 5‐38� m. They show varying combinations of dust continuum, dust emission features (SiC, MgS) and molecular absorption bands (C2H2, HCN). A set of four narrow bands, dubbed the Manchester system, is used to define the infrared continuum for dusty carbon stars. The r elations between the continuum colours and the strength of the dust and molecular features are studied, and are compared to Galactic stars of similar colours. The circumstellar 7-� m C2H2 band is found to be stronger at lower metallicity, from a comparison of stars in the Galaxy, the LMC and the SMC. This is explained by dredge-up of carbon, causing higher C/O ratios at low metallicity (less O). A possible 10-� m absorption feature seen in our spectra may be due to C3. This band has also been identified with interstellar silicate or silicon-nitr ite dust. We investigate the strength and central wavelength of the SiC and MgS dust bands as function of colour and metallicity. The line-to-continuum ratio of these bands shows some indication of being lower at low metallicity. The MgS band is only seen at dust temperatures below 600 K. We discuss the selection of carbon versus oxygen-rich AGB stars using the J K vs. K A colours, and show that these colours are relatively insensitive to chemical type. Metal -poor carbon stars form amorphous carbon dust from self-produced carbon. This type of dust forms more readily in the presence of a higher C/O ratio. Low metallicity carbon dust may contain a smaller fraction of SiC and MgS constituents, which do depend on metallicity. The formation efficiency of oxygen-rich dust depends more strongly on metallicity. We suggest that in lower-metallicity environments, the dust input into the Interstellar Medium by AGB stars is efficient but may be strongly biassed towards carbonaceous dust, as compared to the Galaxy.

A 25 micron search for Vega-like disks around main-sequence stars with ISO

This article compares the distribution of Ks magnitudes of Large Magellanic Cloud (LMC) asymptotic giant branch (AGB) stars obtained from the DENIS and 2MASS data with theoretical distributions. These have been constructed using up-to-date stellar evolution calculations for low and intermediate-mass stars, and in particular for thermally pulsing AGB stars. A fit of the magnitude distribution of both carbon- and oxygen-rich AGB stars allowed us to constrain the metallicity distribution across the LMC and its star formation rate (SFR). The LMC stellar population is found to be on average 5−6 Gyr old and is consistent with a mean metallicity corresponding to Z = 0.006. These values may however be affected by systematic errors in the underlying stellar models, and by the limited exploration of the possible SFR histories. Instead our method should be particularly useful for detecting variations in the mean metallicity and SFR across the LMC disk. There are well defined regions where both the metallicity and the mean-age of the underlying stellar population span the whole range of grid parameters. The C/M ratio discussed in Paper I is a tracer of the metallicity distribution if the underlying stellar population is older than about a few Gyr. A similar study across the Small Magellanic Cloud is given in Paper III of this series.