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DEATHSTAR: Nearby AGB stars with the Atacama Compact Array: III. Mass-loss rates for a sample of carbon stars
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
Department of Space, Earth and Environment, Chalmers University of Technology.
Department of Space, Earth and Environment, Chalmers University of Technology.
Department of Space, Earth and Environment, Chalmers University of Technology.
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(English)Manuscript (preprint) (Other academic)
Keywords [en]
AGB and post-AGB stars, mass loss, circumstellar matter, stellar evolution
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy and Astrophysics
Identifiers
URN: urn:nbn:se:uu:diva-523694OAI: oai:DiVA.org:uu-523694DiVA, id: diva2:1839753
Available from: 2024-02-21 Created: 2024-02-21 Last updated: 2024-02-23
In thesis
1. Mass Loss of Evolved Stars: Improving Mass-Loss Rates and Distances
Open this publication in new window or tab >>Mass Loss of Evolved Stars: Improving Mass-Loss Rates and Distances
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the final stages of their lives, low to intermediate-mass stars enter the Asymptotic Giant Branch (AGB) phase, where they experience significant mass loss through dusty stellar winds. This mass loss is pivotal, not only for the chemical enrichment of the interstellar medium, setting the stage for new stars and planets to form, but also in dictating the evolution and the ultimate fate of the stars themselves. The study of mass loss in AGB stars is therefore of paramount importance. Analyses of emission from CO gas in these outflows allow for the determination of mass-loss rates, as CO serves as a primary tracer for the molecular gas in the circumstellar envelopes of AGB stars. 

However, one of the main uncertainties in mass loss estimations arises from the assumptions on the size of the CO envelope. This uncertainty can be removed using interferometry, which allows for direct measurements of the spatial extent of the CO emission. Using the compact array of the Atacama Large Millimeter/submillimeter Array (ALMA), we measured the extent and investigated the degree of sphericity of the CO-emitting regions around 69 AGB stars in the DEATHSTAR programme. Of those, 27 are presented in this thesis.

Another significant source of uncertainty in mass-loss rate estimates lies in the distance, a fundamental parameter which has been notoriously difficult to accurately determine for AGB stars, especially when relying on optical parallaxes like those from Gaia. To tackle this, we conducted a comparative analysis between Gaia DR3 parallaxes and the more robust parallaxes obtained from high-resolution interferometric observations of maser emissions. This approach enabled us to provide reliable distance estimates for a sample of 200 AGB stars, including the DEATHSTAR sample, offering a valuable resource for the AGB scientific community. 

Using the newly calculated distances and updated CO envelope size measurements, we performed radiative transfer modelling to derive the mass-loss rates of a sample of 27 carbon-rich AGB stars. The spatial information provided by ALMA observations acted as strong constraints for our models, ensuring a more accurate representation of flux contributions from various spatial scales.

By providing the measurement of CO envelope sizes, improving the distance determination to AGB stars, and presenting improved mass-loss rates, this thesis provides new insights into the complex nature of AGB stars and their mass loss.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2024. p. 90
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 2367
Keywords
AGB stars, Mass loss, Distance, Circumstellar matter, Radio interferometry, Stellar evolution
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Physics with specialization in Astrophysics
Identifiers
urn:nbn:se:uu:diva-523696 (URN)978-91-513-2043-4 (ISBN)
Public defence
2024-04-11, Heinz-Otto Kreiss (101195), Ångströmslaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
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Supervisors
Available from: 2024-03-20 Created: 2024-02-23 Last updated: 2024-03-20

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CiteExportLink to record
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Citation style
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