Search: WFRF:(Winnberg Anders 1937)
> (2020-2022) >
CO line observation...
CO line observations of OH/IR stars in the inner Galactic Bulge: Characteristics of stars at the tip of the AGB
-
- Olofsson, Henrik, 1972 (author)
- Chalmers University of Technology
-
- Khouri, Theo, 1985 (author)
- Chalmers University of Technology
-
- Sargent, B. A. (author)
- Space Telescope Science Institute (STScI),Johns Hopkins University,Johns Hopkins University Krieger School of Arts and Sciences,Space Telescope Science Institute
-
show more...
-
- Winnberg, Anders, 1937 (author)
- Chalmers University of Technology
-
- Blommaert, J. A. D. L. (author)
- Vrije Universiteit Brüssel (VUB),Vrije Universiteit Brussel (VUB)
-
- Groenewegen, M. A. T. (author)
- Royal Observatory of Belgium,NASA Ames Research Center
-
- Muller, Sebastien, 1976 (author)
- Chalmers University of Technology
-
- Kastner, J. H. (author)
- Rochester Institute of Technology
-
- Meixner, M. (author)
- NASA Ames Research Center,Kyoto University
-
- Otsuka, M. (author)
- Kyoto University
-
- Patel, N. (author)
- Harvard-Smithsonian Center for Astrophysics,Harvard–Smithsonian Center for Astrophysics
-
- Ryde, N. (author)
- Lund University,Lunds universitet,Astronomi - Genomgår omorganisation,Institutionen för astronomi och teoretisk fysik - Genomgår omorganisation,Naturvetenskapliga fakulteten,Lund Observatory - Undergoing reorganization,Department of Astronomy and Theoretical Physics - Undergoing reorganization,Faculty of Science
-
- Srinivasan, S. (author)
- Universidad Nacional Autónoma de México (UNAM),Universidad Nacional Autonoma de Mexico,National Autonomous University of Mexico
-
show less...
-
(creator_code:org_t)
- 2022-09-15
- 2022
- English.
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 665
- Related links:
-
https://research.cha... (primary) (free)
-
show more...
-
http://dx.doi.org/10... (free)
-
https://research.cha...
-
https://doi.org/10.1...
-
https://lup.lub.lu.s...
-
show less...
Abstract
Subject headings
Close
- Context. OH/IR stars are examples of late stellar evolution on the asymptotic giant branch (AGB), and they are, as such, important objects to study. They are also excellent probes of stellar populations, in particular in regions of high interstellar extinction such as the central regions of our Galaxy. Aims. Our goal is to characterise the stellar and circumstellar properties of high-mass-loss-rate OH/IR stars in the inner Galactic Bulge using the Atacama Large Millimeter/submillimeter Interferometer (ALMA). Methods. Rotational lines of (CO)-C-12 and (CO)-C-13, as well as a millimetre-wave continuum, have been observed for a sample of 22 OH/IR stars in directions within 2 degrees of the Galactic Centre. Photometry data (approximate to 1-30 mu m) have been gathered from the literature to construct spectral energy distributions (SEDs) and to determine pulsational variability. Radiative transfer models have been used to interpret the line and photometry data. Results. All stars in the sample were detected in at least one CO line, and eight objects were detected in 324 GHz continuum. Based on luminosity criteria, the sample is divided into 17 objects that most likely lie within the inner Galactic Bulge, and five objects that are most likely foreground objects. The median luminosity of the inner-Galactic-Bulge sub-sample, 5600 L-circle dot, corresponds to an initial mass in the range 1.2-1.6 M-circle dot, indicating that these inner-Galactic-Bulge OH/IR stars descend from solar-type stars. The objects in this sub-sample are further divided into two classes based on their SED characteristics: Eleven objects have SEDs that are well matched by models invoking dust envelopes extending from a few stellar radii and outwards, while six objects are better modelled as having detached dust envelopes with inner radii in the range 200-600 au and warmer central stars. The former objects have periodic variability, while the latter objects are predominantly non-periodic. The median gas-mass-loss rate, gas terminal expansion velocity, gas-to-dust mass ratio, and circumstellar (CO)-C-12/(CO)-C-13 abundance ratio have been estimated to be 2 x 10(-5) M-circle dot yr(-1), 18 km s(-1), 200 (excluding the sources with detached dust envelopes, which show markedly lower gas-to-dust ratios), and 5, respectively, for the inner-Galactic-Bulge sub-sample. All line brightness distributions are resolved at an angular scale of approximate to 0 ''.15, but only two objects show a structure in their circumstellar envelopes at our resolution and sensitivity. In both cases, this structure takes the form of a cavity and a bipolar morphology. Conclusions. The inner-Galactic-Bulge sub-sample consists of high mass-loss-rate stars that descend from solar-type progenitors and that lie near the tip of the AGB. Some of the sample stars may have recently ceased mass loss and, hence, have begun to evolve beyond the AGB, as evidenced by a change in circumstellar characteristics and indications of warmer central stars. The inferred very low stellar C-12/C-13 isotope ratios are indicative of CNO-cycle nuclear processing, and they are most likely established at the surfaces of the stars during the first dredge-up on the red giant branch since these stars are not expected to experience hot-bottom burning. The inner-Galactic-Bulge OH/IR stars studied here constitute an excellent sample of equidistant objects for the purpose of understanding the evolution of the mass-loss-rate characteristics at the tip of the AGB.
Subject headings
- NATURVETENSKAP -- Geovetenskap och miljövetenskap -- Meteorologi och atmosfärforskning (hsv//swe)
- NATURAL SCIENCES -- Earth and Related Environmental Sciences -- Meteorology and Atmospheric Sciences (hsv//eng)
- NATURVETENSKAP -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)
- NATURVETENSKAP -- Matematik -- Sannolikhetsteori och statistik (hsv//swe)
- NATURAL SCIENCES -- Mathematics -- Probability Theory and Statistics (hsv//eng)
Keyword
- stars: mass-loss
- circumstellar matter
- radio lines: stars
- AGB and post-AGB
- AGB and post-AGB
- Circumstellar matter
- Radio lines: stars
- Stars: mass-loss
Publication and Content Type
- art (subject category)
- ref (subject category)
Find in a library
To the university's database
- By the author/editor
-
Olofsson, Henrik ...
-
Khouri, Theo, 19 ...
-
Sargent, B. A.
-
Winnberg, Anders ...
-
Blommaert, J. A. ...
-
Groenewegen, M. ...
-
show more...
-
Muller, Sebastie ...
-
Kastner, J. H.
-
Meixner, M.
-
Otsuka, M.
-
Patel, N.
-
Ryde, N.
-
Srinivasan, S.
-
show less...
- About the subject
-
- NATURAL SCIENCES
-
NATURAL SCIENCES
-
and Earth and Relate ...
-
and Meteorology and ...
-
- NATURAL SCIENCES
-
NATURAL SCIENCES
-
and Physical Science ...
-
and Astronomy Astrop ...
-
- NATURAL SCIENCES
-
NATURAL SCIENCES
-
and Mathematics
-
and Probability Theo ...
- Articles in the publication
-
Astronomy and As ...
- By the university
-
Chalmers University of Technology
-
Lund University