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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…

Solar and Stellar Astrophysics · Physics 2022-12-07 Susanne Höfner , Bernd Freytag

The purpose of this work is to present an extensive grid of dynamical atmosphere and wind models for M-type AGB stars, covering a wide range of relevant stellar parameters. We used the DARWIN code, which includes frequency-dependent…

Solar and Stellar Astrophysics · Physics 2019-07-10 S. Bladh , S. Liljegren , S. Höfner , B. Aringer , P. Marigo

We study the close circumstellar environment of the nearby S-type star Pi^1 Gruis using high spatial-resolution, mid-infrared observations from the ESO/VLTI. Spectra and visibilities were obtained with the MIDI interferometer on the VLT…

Stellar winds of cool and pulsating asymptotic giant branch (AGB) stars enrich the interstellar medium with large amounts of processed elements and various types of dust. We present the first study on the influence of gas-to-dust drift on…

Solar and Stellar Astrophysics · Physics 2023-08-30 C. Sandin , L. Mattsson , K. L. Chubb , M. Ergon , P. M. Weilbacher

Winds of asymptotic giant branch (AGB) stars are commonly assumed to be driven by radiative acceleration of dust grains. For M-type AGB stars, the nature of the wind-driving dust species has been a matter of intense debate. A proposed…

Solar and Stellar Astrophysics · Physics 2017-07-19 Erik Aronson , Sara Bladh , Susanne Höfner

The formation of silicates in circumstellar envelopes of stars evolving through the AGB is still debated given the uncertainties affecting stellar evolution modelling, the description of the dust formation process, and the capability of…

Solar and Stellar Astrophysics · Physics 2023-02-22 E. Marini , F. Dell'Agli , D. Kamath , P. Ventura , L. Mattsson , T. Marchetti , D. A. García-Hernández , R. Carini , M. Fabrizio , S. Tosi

Convection and mass loss by stellar winds are two dynamical processes that shape asymptotic giant branch (AGB) stars and their evolution. Observations and earlier 3D models indicate that giant convection cells cause high-contrast surface…

Solar and Stellar Astrophysics · Physics 2023-01-30 Bernd Freytag , Susanne Höfner

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…

Solar and Stellar Astrophysics · Physics 2016-04-27 S. Liljegren , S. Höfner , W. Nowotny , K. Eriksson

We aim to constrain the dust mass and grain sizes in the interaction regions between the stellar winds and the ISM around asymptotic giant branch stars. By describing the dust in these regions, we aim to shed light on the role of low mass…

Astrophysics of Galaxies · Physics 2022-09-21 M. Maercker , T. Khouri , M. Mecina , E. De Beck

It is commonly believed that winds of cool giants in their late evolutionary stages are driven by radiative pressure on dust grains, but the actual grain species responsible for driving winds of M-type AGB stars are still a matter of debate…

Solar and Stellar Astrophysics · Physics 2011-02-28 Sara Bladh , Susanne Höfner , Bernhard Aringer

Aims. We present a study of the envelope morphology of the carbon Mira R For with VLTI/MIDI. This object is one of the few asymptotic giant branch (AGB) stars that underwent a dust-obscuration event. The cause of such events is still a…

Solar and Stellar Astrophysics · Physics 2015-06-05 C. Paladini , S. Sacuto , D. Klotz , K. Ohnaka , M. Wittkowski , W. Nowotny , A. Jorissen , J. Hron

Wind-driving in asymptotic giant branch (AGB) stars is commonly attributed to a two-step process. First, matter in the stellar atmosphere is levitated by shock waves, induced by stellar pulsation, and second, this matter is accelerated by…

Solar and Stellar Astrophysics · Physics 2017-09-27 S. Liljegren , S. Höfner , K. Eriksson , W. Nowotny

We observed the AGB stars S Ori, GX Mon and R Cnc with the MIDI instrument at the VLTI. We compared the data to radiative transfer models of the dust shells, where the central stellar intensity profiles were described by dust-free dynamic…

Solar and Stellar Astrophysics · Physics 2015-06-17 I. Karovicova , M. Wittkowski , K. Ohnaka , D. A. Boboltz , E. Fossat , M. Scholz

Recently available near-infrared interferometric data on late-type stars show a strong increase of diameter for asymptotic giant branch (AGB) stars between the K (2.0 - 2.4 \mu m) and L (3.4 - 4.1 \mu m) bands. Aiming at an explanation of…

Dust grains forming in the extended atmospheres of AGB stars are critical for the heavy mass loss of these cool luminous giants, as they provide radiative acceleration for the stellar winds. Characteristic mid-IR spectral features indicate…

Solar and Stellar Astrophysics · Physics 2019-03-27 Susanne Höfner , Bernd Freytag

The mass loss experienced on the asymptotic giant branch (AGB) at the end of the lives of low- and intermediate-mass stars is widely accepted to rely on radiation pressure acting on dust grains formed in the extended AGB atmospheres. The…

Solar and Stellar Astrophysics · Physics 2024-02-22 T. Khouri , H. Olofsson , W. H. T. Vlemmings , T. Schirmer , D. Tafoya , M. Maercker , E. De Beck , L. -Å. Nyman , M. Saberi

Context: Red super-giant (RSG) stars exhibit significant mass loss through a slow and dense wind. They are often considered to be the more massive counter parts of Asymptotic Giant Branch (AGB) stars. While the AGB mass loss is linked to…

Solar and Stellar Astrophysics · Physics 2009-11-13 T. Verhoelst , N. Van der Zypen , S. Hony , L. Decin , J. Cami , K. Eriksson

The presence of stable, compact circumbinary discs of gas and dust around post-asymptotic giant branch (post-AGB) binary systems has been well established. We focus on one such system: IRAS 08544-4431. We present an interferometric…

Solar and Stellar Astrophysics · Physics 2021-06-16 A. Corporaal , J. Kluska , H. Van Winckel , D. Bollen , D. Kamath , M. Min

We investigate the composition of the solid-state materials in the winds around S-type AGB stars. The S stars produce dust in their wind that bears a resemblance to the dust produced in some O-rich AGB stars. However, the reported…

Solar and Stellar Astrophysics · Physics 2017-09-27 S. Hony , A. M. Heras , F. J. Molster , K. Smolders

We present calculations for a magnetised hybrid wind model for Asymptotic Giant Branch (AGB) stars. The model incorporates a canonical Weber-Davis (WD) stellar wind with dust grains in the envelope of an AGB star. The resulting hybrid…

Solar and Stellar Astrophysics · Physics 2014-09-15 Anand Thirumalai , Jeremy S. Heyl