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FältnamnIndikatorerMetadata
00005896naa a2200481 4500
001oai:research.chalmers.se:d1112740-4056-4d9e-991b-02d3259ed973
003SwePub
008240414s2024 | |||||||||||000 ||eng|
0247 a https://doi.org/10.1051/0004-6361/2023462642 DOI
0247 a https://research.chalmers.se/publication/5406902 URI
040 a (SwePub)cth
041 a engb eng
042 9 SwePub
072 7a art2 swepub-publicationtype
072 7a ref2 swepub-contenttype
1001 a Unnikrishnan Nair, Ramlal,d 1997u Chalmers tekniska högskola,Chalmers University of Technology4 aut0 (Swepub:cth)ramlal
2451 0a Charting circumstellar chemistry of carbon-rich asymptotic giant branch stars: I. ALMA 3 mm spectral surveys
264 1c 2024
520 a Context. Asymptotic giant branch (AGB) stars are major contributors to the chemical enrichment of the interstellar medium through nucleosynthesis and extensive mass loss. Direct measures of both processes can be obtained by studying their circumstellar envelopes in molecular line emission. Most of our current knowledge of circumstellar chemistry, in particular in a C-rich environment, is based on observations of the carbon star IRC +10216. Aims. We aim to obtain a more generalised understanding of the chemistry in C-rich AGB circumstellar envelopes by studying a sample of three carbon stars, IRAS 15194-5115, IRAS 15082-4808, and IRAS 07454-7112, and to observationally test the archetypal status often attributed to IRC +10216. Methods. We performed spatially resolved, unbiased spectral surveys in ALMA Band 3 (85-116 GHz). We estimated the sizes of the molecular emitting regions using azimuthally averaged radial profiles of the line brightness distributions. We derived abundance estimates, using a population diagram analysis for molecules with multiple detected lines, and using single-line analytical calculations for the others. Results. We identify a total of 132 rotational transitions from 49 molecular species. There are two main morphologies of the brightness distributions: centrally peaked (CS, SiO, SiS, HCN) and shell-like (CN, HNC, C2H, C3H, C4H, C3N, HC5N, c-C3H2). The brightness distributions of HC3N and SiC2 have both a central and a shell component. The qualitative behaviour of the brightness distributions of all detected molecules, in particular their relative locations with respect to the central star, is the same for all three stars, and consistent with those observed towards IRC +10216. Of the shell distributions, the cyanopolyynes peak at slightly smaller radii than the hydrocarbons, and CN and HNC show the most extended emission. The emitting regions for each species are the smallest for IRAS 07454-7112, consistent with this object having the lowest circumstellar density within our sample. We find that, within the uncertainties of the analysis, the three stars present similar abundances for most species, and also compared to IRC +10216. We find, tentatively, that SiO is more abundant in our three stars compared to IRC+10216, and that the hydrocarbons are under-abundant in IRAS 07454-7112 compared to the other stars and IRC +10216. Our estimated 12C/13C ratios match well the literature values for the three sources and our estimated silicon and sulphur isotopic ratios are very similar across the three stars and IRC +10216. Conclusions. The observed circumstellar chemistry appears very similar across our sample and compared to that of IRC +10216, both in terms of the relative location of the emitting regions and molecular abundances. This implies that, to a first approximation, the chemical models tailored to IRC +10216 are, at least, able to reproduce the observed chemistry in C-rich envelopes across roughly an order of magnitude in wind density.
650 7a NATURVETENSKAPx Fysikx Astronomi, astrofysik och kosmologi0 (SwePub)103052 hsv//swe
650 7a NATURAL SCIENCESx Physical Sciencesx Astronomy, Astrophysics and Cosmology0 (SwePub)103052 hsv//eng
653 a astrochemistry
653 a stars: mass-loss
653 a submillimeter: stars
653 a circumstellar matter
653 a stars: AGB and post-AGB
653 a stars: winds, outflows
7001 a De Beck, Elvire,d 1985u Chalmers tekniska högskola,Chalmers University of Technology4 aut0 (Swepub:cth)elvire
7001 a Nyman, Lars-Åke,d 1954u Atacama Large Millimeter-submillimeter Array (ALMA),European Southern Observatory Santiago,Chalmers tekniska högskola,Chalmers University of Technology4 aut0 (Swepub:cth)nymanla
7001 a Olofsson, Hans,d 1952u Chalmers tekniska högskola,Chalmers University of Technology4 aut0 (Swepub:cth)hanolo
7001 a Vlemmings, Wouter,d 1974u Chalmers tekniska högskola,Chalmers University of Technology4 aut0 (Swepub:cth)wouterv
7001 a Tafoya, Daniel,d 1981u Chalmers tekniska högskola,Chalmers University of Technology4 aut0 (Swepub:cth)tafoya
7001 a Maercker, Matthias,d 1979u Chalmers tekniska högskola,Chalmers University of Technology4 aut0 (Swepub:cth)maercker
7001 a Charnley, S.B.u NASA Goddard Space Flight Center4 aut
7001 a Cordiner, M. A.u NASA Goddard Space Flight Center,Catholic University of America4 aut
7001 a De Gregorio, I.u European Southern Observatory Santiago4 aut
7001 a Humphreys, E.u Atacama Large Millimeter-submillimeter Array (ALMA),European Southern Observatory Santiago4 aut
7001 a Millar, T.J.u Queen's University Belfast4 aut
7001 a Rawlings, M.G.u East Asian Observatory,Gemini Observatory North4 aut
7102 a Chalmers tekniska högskolab Atacama Large Millimeter-submillimeter Array (ALMA)4 org
7730 t Astronomy and Astrophysicsg 684q 684x 0004-6361x 1432-0746
8564 8u https://doi.org/10.1051/0004-6361/202346264
8564 8u https://research.chalmers.se/publication/540690

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