Spitzer observations of acetylene bands in carbon-rich asymptotic giant branch stars in the Large Magellanic Cloud
Identifieur interne : 000928 ( Istex/Curation ); précédent : 000927; suivant : 000929Spitzer observations of acetylene bands in carbon-rich asymptotic giant branch stars in the Large Magellanic Cloud
Auteurs : M. Matsuura [Royaume-Uni, Japon] ; P. R. Wood [Australie] ; G. C. Sloan [États-Unis] ; A. A. Zijlstra [Royaume-Uni] ; J. Th. Van Loon ; M. A. T. Groenewegen [Belgique] ; J. A. D. L. Blommaert [Belgique] ; M.-R. L. Cioni [Royaume-Uni] ; M. W. Feast [Afrique du Sud] ; H. J. Habing [Pays-Bas] ; S. Hony [Belgique] ; E. Lagadec [Royaume-Uni] ; C. Loup [France] ; J. W. Menzies [Afrique du Sud] ; L. B. F. M. Waters [Belgique, Pays-Bas] ; P. A. Whitelock [Afrique du Sud]Source :
- Monthly Notices of the Royal Astronomical Society [ 0035-8711 ] ; 2006-09-01.
Abstract
We investigate the molecular bands in carbon-rich asymptotic giant branch (AGB) stars in the Large Magellanic Cloud (LMC), using the Infrared Spectrograph (IRS) onboard the Spitzer Space Telescope (SST) over the 5–38 μm range. All 26 low-resolution spectra show acetylene (C2H2) bands at 7 and 14 μm. The hydrogen cyanide (HCN) bands at these wavelengths are very weak or absent. This is consistent with low nitrogen abundances in the LMC. The observed 14 μm C2H2 band is reasonably reproduced by an excitation temperature of 500 K. There is no clear dilution of the 14 μm C2H2 band by circumstellar dust emission. This 14-μm band originates from molecular gas in the circumstellar envelope in these high mass-loss rate stars, in agreement with previous findings for Galactic stars. The C2H2 column density, derived from the 13.7 μm band, shows a gas mass-loss rate in the range 3 × 10−6 to 5 × 10−5 M⊙ yr−1. This is comparable with the total mass-loss rate of these stars estimated from the spectral energy distribution. Additionally, we compare the line strengths of the 13.7 μm C2H2 band of our LMC sample with those of a Galactic sample. Despite the low metallicity of the LMC, there is no clear difference in the C2H2 abundance among LMC and Galactic stars. This reflects the effect of the third dredge-up bringing self-produced carbon to the surface, leading to high carbon-to-oxygen ratio at low metallicity.
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DOI: 10.1111/j.1365-2966.2006.10664.x
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J. Th. Van Loon<affiliation><mods:affiliation>Astrophysics Group, School of Physical and Geographical Sciences, Keele University, Staffordshire ST5 5BG</mods:affiliation><wicri:noCountry code="subField">5BG</wicri:noCountry></affiliation>Le document en format XML
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Matsuura</name><affiliation wicri:level="4"><mods:affiliation>School of Physics and Astronomy, University of Manchester, Sackville Street, PO Box 88, Manchester M60 1QD</mods:affiliation><orgName type="university">Université de Manchester</orgName><country>Royaume-Uni</country><placeName><settlement type="city">Manchester</settlement><region type="nation">Angleterre</region><region nuts="2" type="region">Grand Manchester</region></placeName></affiliation><affiliation><mods:affiliation>APS Division, Department of Pure and Applied Physics, Queen's University Belfast, University Road, Belfast BT7 1NN</mods:affiliation><wicri:noCountry code="subField">1NN</wicri:noCountry></affiliation><affiliation wicri:level="1"><mods:affiliation>National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan</mods:affiliation><country xml:lang="fr">Japon</country><wicri:regionArea>National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588</wicri:regionArea></affiliation><affiliation wicri:level="1"><mods:affiliation>E-mail: mikako@optik.mtk.nao.ac.jp</mods:affiliation><country wicri:rule="url">Japon</country></affiliation><affiliation wicri:level="1"><mods:affiliation>*E-mail: mikako@optik.mtk.nao.ac.jp</mods:affiliation><country wicri:rule="url">Japon</country></affiliation><affiliation wicri:level="1"><mods:affiliation>E-mail: mikako@optik.mtk.nao.ac.jp</mods:affiliation><country wicri:rule="url">Japon</country></affiliation></author><author><name sortKey="Wood, P R" sort="Wood, P R" uniqKey="Wood P" first="P. R." last="Wood">P. R. Wood</name><affiliation wicri:level="1"><mods:affiliation>Research School of Astronomy & Astrophysics, Mount Stromlo Observatory, Australian National University, Cotter Road, Weston ACT 2611, Australia</mods:affiliation><country xml:lang="fr">Australie</country><wicri:regionArea>Research School of Astronomy & Astrophysics, Mount Stromlo Observatory, Australian National University, Cotter Road, Weston ACT 2611</wicri:regionArea></affiliation></author><author><name sortKey="Sloan, G C" sort="Sloan, G C" uniqKey="Sloan G" first="G. C." last="Sloan">G. C. Sloan</name><affiliation wicri:level="1"><mods:affiliation>Astronomy Department, Cornell University, 610 Space Sciences Building, Ithaca, NY 14853-6801, USA</mods:affiliation><country xml:lang="fr">États-Unis</country><wicri:regionArea>Astronomy Department, Cornell University, 610 Space Sciences Building, Ithaca, NY 14853-6801</wicri:regionArea></affiliation></author><author><name sortKey="Zijlstra, A A" sort="Zijlstra, A A" uniqKey="Zijlstra A" first="A. A." last="Zijlstra">A. A. Zijlstra</name><affiliation wicri:level="4"><mods:affiliation>School of Physics and Astronomy, University of Manchester, Sackville Street, PO Box 88, Manchester M60 1QD</mods:affiliation><orgName type="university">Université de Manchester</orgName><country>Royaume-Uni</country><placeName><settlement type="city">Manchester</settlement><region type="nation">Angleterre</region><region nuts="2" type="region">Grand Manchester</region></placeName></affiliation></author><author><name sortKey="Van Loon, J Th" sort="Van Loon, J Th" uniqKey="Van Loon J" first="J. Th." last="Van Loon">J. Th. Van Loon</name><affiliation><mods:affiliation>Astrophysics Group, School of Physical and Geographical Sciences, Keele University, Staffordshire ST5 5BG</mods:affiliation><wicri:noCountry code="subField">5BG</wicri:noCountry></affiliation></author><author><name sortKey="Groenewegen, M A T" sort="Groenewegen, M A T" uniqKey="Groenewegen M" first="M. A. T." last="Groenewegen">M. A. T. Groenewegen</name><affiliation wicri:level="1"><mods:affiliation>Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium</mods:affiliation><country xml:lang="fr">Belgique</country><wicri:regionArea>Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200B, 3001 Leuven</wicri:regionArea></affiliation></author><author><name sortKey="Blommaert, J A D L" sort="Blommaert, J A D L" uniqKey="Blommaert J" first="J. A. D. L." last="Blommaert">J. A. D. L. Blommaert</name><affiliation wicri:level="1"><mods:affiliation>Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium</mods:affiliation><country xml:lang="fr">Belgique</country><wicri:regionArea>Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200B, 3001 Leuven</wicri:regionArea></affiliation></author><author><name sortKey="Cioni, M R L" sort="Cioni, M R L" uniqKey="Cioni M" first="M.-R. L." last="Cioni">M.-R. L. Cioni</name><affiliation wicri:level="4"><mods:affiliation>SUPA, School of Physics, University of Edinburgh, IfA, Blackford Hill, Edinburgh EH9 3HJ</mods:affiliation><orgName type="university">Université d'Édimbourg</orgName><country>Royaume-Uni</country><placeName><settlement type="city">Édimbourg</settlement><region type="country">Écosse</region></placeName></affiliation></author><author><name sortKey="Feast, M W" sort="Feast, M W" uniqKey="Feast M" first="M. W." last="Feast">M. W. Feast</name><affiliation wicri:level="1"><mods:affiliation>Astronomy Department, University of Cape Town, 7701 Rondebosch, South Africa</mods:affiliation><country xml:lang="fr">Afrique du Sud</country><wicri:regionArea>Astronomy Department, University of Cape Town, 7701 Rondebosch</wicri:regionArea></affiliation></author><author><name sortKey="Habing, H J" sort="Habing, H J" uniqKey="Habing H" first="H. J." last="Habing">H. J. Habing</name><affiliation wicri:level="1"><mods:affiliation>Sterrewacht Leiden, Niels Bohrweg 2, 2333 RA Leiden, the Netherlands</mods:affiliation><country xml:lang="fr" wicri:curation="lc">Pays-Bas</country><wicri:regionArea>Sterrewacht Leiden, Niels Bohrweg 2, 2333 RA Leiden</wicri:regionArea></affiliation></author><author><name sortKey="Hony, S" sort="Hony, S" uniqKey="Hony S" first="S." last="Hony">S. Hony</name><affiliation wicri:level="1"><mods:affiliation>Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium</mods:affiliation><country xml:lang="fr">Belgique</country><wicri:regionArea>Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200B, 3001 Leuven</wicri:regionArea></affiliation></author><author><name sortKey="Lagadec, E" sort="Lagadec, E" uniqKey="Lagadec E" first="E." last="Lagadec">E. Lagadec</name><affiliation wicri:level="4"><mods:affiliation>School of Physics and Astronomy, University of Manchester, Sackville Street, PO Box 88, Manchester M60 1QD</mods:affiliation><orgName type="university">Université de Manchester</orgName><country>Royaume-Uni</country><placeName><settlement type="city">Manchester</settlement><region type="nation">Angleterre</region><region nuts="2" type="region">Grand Manchester</region></placeName></affiliation></author><author><name sortKey="Loup, C" sort="Loup, C" uniqKey="Loup C" first="C." last="Loup">C. Loup</name><affiliation wicri:level="1"><mods:affiliation>Institut d'Astrophysique de Paris, CNRS, 98bis Boulevard Arago, 75014 Paris, France</mods:affiliation><country xml:lang="fr">France</country><wicri:regionArea>Institut d'Astrophysique de Paris, CNRS, 98bis Boulevard Arago, 75014 Paris</wicri:regionArea></affiliation></author><author><name sortKey="Menzies, J W" sort="Menzies, J W" uniqKey="Menzies J" first="J. W." last="Menzies">J. W. Menzies</name><affiliation wicri:level="1"><mods:affiliation>South African Astronomical Observatory, PO Box 9, 7935 Observatory, South Africa</mods:affiliation><country xml:lang="fr">Afrique du Sud</country><wicri:regionArea>South African Astronomical Observatory, PO Box 9, 7935 Observatory</wicri:regionArea></affiliation></author><author><name sortKey="Waters, L B F M" sort="Waters, L B F M" uniqKey="Waters L" first="L. B. F. M." last="Waters">L. B. F. M. Waters</name><affiliation wicri:level="1"><mods:affiliation>Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium</mods:affiliation><country xml:lang="fr">Belgique</country><wicri:regionArea>Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200B, 3001 Leuven</wicri:regionArea></affiliation><affiliation wicri:level="1"><mods:affiliation>Astronomical Institute ‘Anton Pannekoek’, University of Amsterdam, Kruislaan 403, 1098 SJ, Amsterdam, the Netherlands</mods:affiliation><country xml:lang="fr" wicri:curation="lc">Pays-Bas</country><wicri:regionArea>Astronomical Institute ‘Anton Pannekoek’, University of Amsterdam, Kruislaan 403, 1098 SJ, Amsterdam</wicri:regionArea></affiliation></author><author><name sortKey="Whitelock, P A" sort="Whitelock, P A" uniqKey="Whitelock P" first="P. A." last="Whitelock">P. A. Whitelock</name><affiliation wicri:level="1"><mods:affiliation>Astronomy Department, University of Cape Town, 7701 Rondebosch, South Africa</mods:affiliation><country xml:lang="fr">Afrique du Sud</country><wicri:regionArea>Astronomy Department, University of Cape Town, 7701 Rondebosch</wicri:regionArea></affiliation><affiliation wicri:level="1"><mods:affiliation>South African Astronomical Observatory, PO Box 9, 7935 Observatory, South Africa</mods:affiliation><country xml:lang="fr">Afrique du Sud</country><wicri:regionArea>South African Astronomical Observatory, PO Box 9, 7935 Observatory</wicri:regionArea></affiliation><affiliation wicri:level="1"><mods:affiliation>NASSP, Department of Mathematics and Applied Mathematics, University of Cape Town, 7701 Rondebosch, South Africa</mods:affiliation><country xml:lang="fr">Afrique du Sud</country><wicri:regionArea>NASSP, Department of Mathematics and Applied Mathematics, University of Cape Town, 7701 Rondebosch</wicri:regionArea></affiliation></author></titleStmt><publicationStmt><idno type="wicri:source">ISTEX</idno><idno type="RBID">ISTEX:3069AFB278002056B5714EDFEBC47026C848B163</idno><date when="2006" year="2006">2006</date><idno type="doi">10.1111/j.1365-2966.2006.10664.x</idno><idno type="url">https://api.istex.fr/document/3069AFB278002056B5714EDFEBC47026C848B163/fulltext/pdf</idno><idno type="wicri:Area/Istex/Corpus">000928</idno><idno type="wicri:explorRef" wicri:stream="Istex" wicri:step="Corpus" wicri:corpus="ISTEX">000928</idno><idno type="wicri:Area/Istex/Curation">000928</idno></publicationStmt><sourceDesc><biblStruct><analytic><title level="a">Spitzer observations of acetylene bands in carbon-rich asymptotic giant branch stars in the Large Magellanic Cloud</title><author><name sortKey="Matsuura, M" sort="Matsuura, M" uniqKey="Matsuura M" first="M." last="Matsuura">M. Matsuura</name><affiliation wicri:level="4"><mods:affiliation>School of Physics and Astronomy, University of Manchester, Sackville Street, PO Box 88, Manchester M60 1QD</mods:affiliation><orgName type="university">Université de Manchester</orgName><country>Royaume-Uni</country><placeName><settlement type="city">Manchester</settlement><region type="nation">Angleterre</region><region nuts="2" type="region">Grand Manchester</region></placeName></affiliation><affiliation><mods:affiliation>APS Division, Department of Pure and Applied Physics, Queen's University Belfast, University Road, Belfast BT7 1NN</mods:affiliation></affiliation><affiliation wicri:level="1"><mods:affiliation>National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan</mods:affiliation><country xml:lang="fr">Japon</country><wicri:regionArea>National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588</wicri:regionArea></affiliation><affiliation wicri:level="1"><mods:affiliation>E-mail: mikako@optik.mtk.nao.ac.jp</mods:affiliation><country wicri:rule="url">Japon</country></affiliation><affiliation wicri:level="1"><mods:affiliation>*E-mail: mikako@optik.mtk.nao.ac.jp</mods:affiliation><country wicri:rule="url">Japon</country></affiliation><affiliation wicri:level="1"><mods:affiliation>E-mail: mikako@optik.mtk.nao.ac.jp</mods:affiliation><country wicri:rule="url">Japon</country></affiliation></author><author><name sortKey="Wood, P R" sort="Wood, P R" uniqKey="Wood P" first="P. R." last="Wood">P. R. Wood</name><affiliation wicri:level="1"><mods:affiliation>Research School of Astronomy & Astrophysics, Mount Stromlo Observatory, Australian National University, Cotter Road, Weston ACT 2611, Australia</mods:affiliation><country xml:lang="fr">Australie</country><wicri:regionArea>Research School of Astronomy & Astrophysics, Mount Stromlo Observatory, Australian National University, Cotter Road, Weston ACT 2611</wicri:regionArea></affiliation></author><author><name sortKey="Sloan, G C" sort="Sloan, G C" uniqKey="Sloan G" first="G. C." last="Sloan">G. C. Sloan</name><affiliation wicri:level="1"><mods:affiliation>Astronomy Department, Cornell University, 610 Space Sciences Building, Ithaca, NY 14853-6801, USA</mods:affiliation><country xml:lang="fr">États-Unis</country><wicri:regionArea>Astronomy Department, Cornell University, 610 Space Sciences Building, Ithaca, NY 14853-6801</wicri:regionArea></affiliation></author><author><name sortKey="Zijlstra, A A" sort="Zijlstra, A A" uniqKey="Zijlstra A" first="A. A." last="Zijlstra">A. A. Zijlstra</name><affiliation wicri:level="4"><mods:affiliation>School of Physics and Astronomy, University of Manchester, Sackville Street, PO Box 88, Manchester M60 1QD</mods:affiliation><orgName type="university">Université de Manchester</orgName><country>Royaume-Uni</country><placeName><settlement type="city">Manchester</settlement><region type="nation">Angleterre</region><region nuts="2" type="region">Grand Manchester</region></placeName></affiliation></author><author><name sortKey="Van Loon, J Th" sort="Van Loon, J Th" uniqKey="Van Loon J" first="J. Th." last="Van Loon">J. Th. Van Loon</name><affiliation><mods:affiliation>Astrophysics Group, School of Physical and Geographical Sciences, Keele University, Staffordshire ST5 5BG</mods:affiliation><wicri:noCountry code="subField">5BG</wicri:noCountry></affiliation></author><author><name sortKey="Groenewegen, M A T" sort="Groenewegen, M A T" uniqKey="Groenewegen M" first="M. A. T." last="Groenewegen">M. A. T. Groenewegen</name><affiliation wicri:level="1"><mods:affiliation>Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium</mods:affiliation><country xml:lang="fr">Belgique</country><wicri:regionArea>Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200B, 3001 Leuven</wicri:regionArea></affiliation></author><author><name sortKey="Blommaert, J A D L" sort="Blommaert, J A D L" uniqKey="Blommaert J" first="J. A. D. L." last="Blommaert">J. A. D. L. Blommaert</name><affiliation wicri:level="1"><mods:affiliation>Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium</mods:affiliation><country xml:lang="fr">Belgique</country><wicri:regionArea>Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200B, 3001 Leuven</wicri:regionArea></affiliation></author><author><name sortKey="Cioni, M R L" sort="Cioni, M R L" uniqKey="Cioni M" first="M.-R. L." last="Cioni">M.-R. L. Cioni</name><affiliation wicri:level="4"><mods:affiliation>SUPA, School of Physics, University of Edinburgh, IfA, Blackford Hill, Edinburgh EH9 3HJ</mods:affiliation><orgName type="university">Université d'Édimbourg</orgName><country>Royaume-Uni</country><placeName><settlement type="city">Édimbourg</settlement><region type="country">Écosse</region></placeName></affiliation></author><author><name sortKey="Feast, M W" sort="Feast, M W" uniqKey="Feast M" first="M. W." last="Feast">M. W. Feast</name><affiliation wicri:level="1"><mods:affiliation>Astronomy Department, University of Cape Town, 7701 Rondebosch, South Africa</mods:affiliation><country xml:lang="fr">Afrique du Sud</country><wicri:regionArea>Astronomy Department, University of Cape Town, 7701 Rondebosch</wicri:regionArea></affiliation></author><author><name sortKey="Habing, H J" sort="Habing, H J" uniqKey="Habing H" first="H. J." last="Habing">H. J. Habing</name><affiliation wicri:level="1"><mods:affiliation>Sterrewacht Leiden, Niels Bohrweg 2, 2333 RA Leiden, the Netherlands</mods:affiliation><country xml:lang="fr" wicri:curation="lc">Pays-Bas</country><wicri:regionArea>Sterrewacht Leiden, Niels Bohrweg 2, 2333 RA Leiden</wicri:regionArea></affiliation></author><author><name sortKey="Hony, S" sort="Hony, S" uniqKey="Hony S" first="S." last="Hony">S. Hony</name><affiliation wicri:level="1"><mods:affiliation>Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium</mods:affiliation><country xml:lang="fr">Belgique</country><wicri:regionArea>Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200B, 3001 Leuven</wicri:regionArea></affiliation></author><author><name sortKey="Lagadec, E" sort="Lagadec, E" uniqKey="Lagadec E" first="E." last="Lagadec">E. Lagadec</name><affiliation wicri:level="4"><mods:affiliation>School of Physics and Astronomy, University of Manchester, Sackville Street, PO Box 88, Manchester M60 1QD</mods:affiliation><orgName type="university">Université de Manchester</orgName><country>Royaume-Uni</country><placeName><settlement type="city">Manchester</settlement><region type="nation">Angleterre</region><region nuts="2" type="region">Grand Manchester</region></placeName></affiliation></author><author><name sortKey="Loup, C" sort="Loup, C" uniqKey="Loup C" first="C." last="Loup">C. Loup</name><affiliation wicri:level="1"><mods:affiliation>Institut d'Astrophysique de Paris, CNRS, 98bis Boulevard Arago, 75014 Paris, France</mods:affiliation><country xml:lang="fr">France</country><wicri:regionArea>Institut d'Astrophysique de Paris, CNRS, 98bis Boulevard Arago, 75014 Paris</wicri:regionArea></affiliation></author><author><name sortKey="Menzies, J W" sort="Menzies, J W" uniqKey="Menzies J" first="J. W." last="Menzies">J. W. Menzies</name><affiliation wicri:level="1"><mods:affiliation>South African Astronomical Observatory, PO Box 9, 7935 Observatory, South Africa</mods:affiliation><country xml:lang="fr">Afrique du Sud</country><wicri:regionArea>South African Astronomical Observatory, PO Box 9, 7935 Observatory</wicri:regionArea></affiliation></author><author><name sortKey="Waters, L B F M" sort="Waters, L B F M" uniqKey="Waters L" first="L. B. F. M." last="Waters">L. B. F. M. Waters</name><affiliation wicri:level="1"><mods:affiliation>Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium</mods:affiliation><country xml:lang="fr">Belgique</country><wicri:regionArea>Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200B, 3001 Leuven</wicri:regionArea></affiliation><affiliation wicri:level="1"><mods:affiliation>Astronomical Institute ‘Anton Pannekoek’, University of Amsterdam, Kruislaan 403, 1098 SJ, Amsterdam, the Netherlands</mods:affiliation><country xml:lang="fr" wicri:curation="lc">Pays-Bas</country><wicri:regionArea>Astronomical Institute ‘Anton Pannekoek’, University of Amsterdam, Kruislaan 403, 1098 SJ, Amsterdam</wicri:regionArea></affiliation></author><author><name sortKey="Whitelock, P A" sort="Whitelock, P A" uniqKey="Whitelock P" first="P. A." last="Whitelock">P. A. Whitelock</name><affiliation wicri:level="1"><mods:affiliation>Astronomy Department, University of Cape Town, 7701 Rondebosch, South Africa</mods:affiliation><country xml:lang="fr">Afrique du Sud</country><wicri:regionArea>Astronomy Department, University of Cape Town, 7701 Rondebosch</wicri:regionArea></affiliation><affiliation wicri:level="1"><mods:affiliation>South African Astronomical Observatory, PO Box 9, 7935 Observatory, South Africa</mods:affiliation><country xml:lang="fr">Afrique du Sud</country><wicri:regionArea>South African Astronomical Observatory, PO Box 9, 7935 Observatory</wicri:regionArea></affiliation><affiliation wicri:level="1"><mods:affiliation>NASSP, Department of Mathematics and Applied Mathematics, University of Cape Town, 7701 Rondebosch, South Africa</mods:affiliation><country xml:lang="fr">Afrique du Sud</country><wicri:regionArea>NASSP, Department of Mathematics and Applied Mathematics, University of Cape Town, 7701 Rondebosch</wicri:regionArea></affiliation></author></analytic><monogr></monogr><series><title level="j">Monthly Notices of the Royal Astronomical Society</title><title level="j" type="abbrev">Monthly Notices of the Royal Astronomical Society</title><idno type="ISSN">0035-8711</idno><idno type="eISSN">1365-2966</idno><imprint><publisher>Blackwell Publishing Ltd</publisher><pubPlace>Oxford, UK</pubPlace><date type="published" when="2006-09-01">2006-09-01</date><biblScope unit="volume">371</biblScope><biblScope unit="issue">1</biblScope><biblScope unit="page" from="415">415</biblScope><biblScope unit="page" to="420">420</biblScope></imprint><idno type="ISSN">0035-8711</idno></series></biblStruct></sourceDesc><seriesStmt><idno type="ISSN">0035-8711</idno></seriesStmt></fileDesc><profileDesc><textClass></textClass></profileDesc></teiHeader><front><div type="abstract">We investigate the molecular bands in carbon-rich asymptotic giant branch (AGB) stars in the Large Magellanic Cloud (LMC), using the Infrared Spectrograph (IRS) onboard the Spitzer Space Telescope (SST) over the 5–38 μm range. All 26 low-resolution spectra show acetylene (C2H2) bands at 7 and 14 μm. The hydrogen cyanide (HCN) bands at these wavelengths are very weak or absent. This is consistent with low nitrogen abundances in the LMC. The observed 14 μm C2H2 band is reasonably reproduced by an excitation temperature of 500 K. There is no clear dilution of the 14 μm C2H2 band by circumstellar dust emission. This 14-μm band originates from molecular gas in the circumstellar envelope in these high mass-loss rate stars, in agreement with previous findings for Galactic stars. The C2H2 column density, derived from the 13.7 μm band, shows a gas mass-loss rate in the range 3 × 10−6 to 5 × 10−5 M⊙ yr−1. This is comparable with the total mass-loss rate of these stars estimated from the spectral energy distribution. Additionally, we compare the line strengths of the 13.7 μm C2H2 band of our LMC sample with those of a Galactic sample. Despite the low metallicity of the LMC, there is no clear difference in the C2H2 abundance among LMC and Galactic stars. This reflects the effect of the third dredge-up bringing self-produced carbon to the surface, leading to high carbon-to-oxygen ratio at low metallicity.</div></front></TEI></record>Pour manipuler ce document sous Unix (Dilib)
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|texte= Spitzer observations of acetylene bands in carbon-rich asymptotic giant branch stars in the Large Magellanic Cloud
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