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The extended molecu...
The extended molecular envelope of the asymptotic giant branchstar π1 Gruis as seen by ALMA : I. Large-scale kinematic structure and CO excitation properties
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- Doan, Lam (författare)
- Uppsala universitet,Teoretisk astrofysik
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- Ramstedt, Sofia (författare)
- Uppsala universitet,Teoretisk astrofysik
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- Vlemmings, W. H. T. (författare)
- Department of Earth and Space Sciences, Chalmers University of Technology
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- Höfner, Susanne (författare)
- Uppsala universitet,Teoretisk astrofysik
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- De Beck, E. (författare)
- Department of Earth and Space Sciences, Chalmers University of Technology
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- Kerschbaum, F. (författare)
- Department of Astrophysics, University of Vienna
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- Lindqvist, M. (författare)
- Department of Earth and Space Sciences, Chalmers University of Technology
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- Maercker, M. (författare)
- Department of Earth and Space Sciences, Chalmers University of Technology
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- Mohamed, S. (författare)
- South African Astronomical Observatory; Astronomy Department, University of Cape Town; National Institute for Theoretical Physics, Private Bag X1, 7602 Matieland
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- Paladini, C. (författare)
- Institut d’Astronomie et d’Astrophysique, Université Libre de Bruxelles
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- Wittkowski, M. (författare)
- European Southern Observatory, Germany
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(creator_code:org_t)
- 2017-09-04
- 2017
- Engelska.
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 605
- Relaterad länk:
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https://www.aanda.or...
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https://urn.kb.se/re...
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https://doi.org/10.1...
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Abstract
Ämnesord
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- Context. The S-type asymptotic giant branch (AGB) star pi(1) Gru has a known companion at a separation of 2 ''.7 (approximate to 400 AU). Previous observations of the circumstellar envelope (CSE) show strong deviations from spherical symmetry. The envelope structure, including an equatorial torus and a fast bipolar outflow, is rarely seen in the AGB phase and is particularly unexpected in such a wide binary system. Therefore a second, closer companion has been suggested, but the evidence is not conclusive.Aims. The aim is to make a 3D model of the CSE and to constrain the density and temperature distribution using new spatially resolved observations of the CO rotational lines.Methods. We have observed the J = 3-2 line emission from (CO)-C-12 and (CO)-C-13 using the compact arrays of the Atacama Large Millimeter/submillimeter Array (ALMA). The new ALMA data, together with previously published (CO)-C-12 J = 2-1 data from the Submillimeter Array (SMA), and the (CO)-C-12 J = 5-4 and J = 9-8 lines observed with Herschel/Heterodyne Instrument for the Far-Infrared (HIFI), is modeled with the 3D non-LTE radiative transfer code SHAPEMOL.Results. The data analysis clearly confirms the torus-bipolar structure. The 3D model of the CSE that satisfactorily reproduces the data consists of three kinematic components: a radially expanding torus with velocity slowly increasing from 8 to 13 km s(-1) along the equator plane; a radially expanding component at the center with a constant velocity of 14 km s(-1); and a fast, bipolar outflow with velocity proportionally increasing from 14 km s(-1) at the base up to 100 km s(-1) at the tip, following a linear radial dependence. The results are used to estimate an average mass-loss rate during the creation of the torus of 7.7 x 10(-7) M-circle dot yr(-1). The total mass and linear momentum of the fast outflow are estimated at 7.3 x 10(-4) M-circle dot and 9.6 x 10(37) g cm s(-1), respectively. The momentum of the outflow is in excess (by a factor of about 20) of what could be generated by radiation pressure alone, in agreement with recent findings for more evolved sources. The best-fit model also suggests a (CO)-C-12/(CO)-C-13 abundance ratio of 50. Possible shaping scenarios for the gas envelope are discussed.
Ämnesord
- NATURVETENSKAP -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)
Nyckelord
- stars: AGB and post-AGB; stars: mass-loss; stars: individual: pi(1) Gru; stars: general; radio lines: stars; binaries: general
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Doan, Lam
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Ramstedt, Sofia
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Vlemmings, W. H. ...
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Höfner, Susanne
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De Beck, E.
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Kerschbaum, F.
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visa fler...
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Lindqvist, M.
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Maercker, M.
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Mohamed, S.
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Paladini, C.
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Wittkowski, M.
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