ALMA observations of the circumstellar envelope around EP Aqr
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摘要
Atacama Large Millimetre/sub-millimetre Array(ALMA) observations of CO(1–0) and CO(2–1) emissions from the circumstellar envelope of the asymptotic giant branch(AGB) star EP Aqr have been made with four times better spatial resolution than previously available. They are analysed with emphasis on the de-projection in space of the effective emissivity and flux of matter using as input a prescribed configuration of the velocity field, assumed to be radial. The data are found to display an intrinsic axisymmetry with respect to an axis making a small angle with respect to the line of sight. A broad range of wind configurations, from prolate(bipolar) to oblate(equatorial) has been studied and found to be accompanied by significant equatorial emission. Qualitatively, the effective emissivity is enhanced near the equator to produce the central narrow component observed in the Doppler velocity spectra and its dependence on star latitude generally follows that of the wind velocity with the exception of an omni-present depression near the poles. In particular, large equatorial expansion velocities produce a flared disc or a ring of effective emissivity and mass loss. The effect on the determination of the orientation of the star axis of radial velocity gradients, and possibly competing rotation and expansion in the equatorial disc, is discussed. In general,the flux of matter is found to reach a broad maximum at distances of the order of 500 AU from the star.Arguments are given that may be used to favour one wind velocity distribution over another. As a result of the improved quality of the data, a deeper understanding of the constraints imposed on morphology and kinematics has been obtained.
Atacama Large Millimetre/sub-millimetre Array(ALMA) observations of CO(1–0) and CO(2–1) emissions from the circumstellar envelope of the asymptotic giant branch(AGB) star EP Aqr have been made with four times better spatial resolution than previously available. They are analysed with emphasis on the de-projection in space of the effective emissivity and flux of matter using as input a prescribed configuration of the velocity field, assumed to be radial. The data are found to display an intrinsic axisymmetry with respect to an axis making a small angle with respect to the line of sight. A broad range of wind configurations, from prolate(bipolar) to oblate(equatorial) has been studied and found to be accompanied by significant equatorial emission. Qualitatively, the effective emissivity is enhanced near the equator to produce the central narrow component observed in the Doppler velocity spectra and its dependence on star latitude generally follows that of the wind velocity with the exception of an omni-present depression near the poles. In particular, large equatorial expansion velocities produce a flared disc or a ring of effective emissivity and mass loss. The effect on the determination of the orientation of the star axis of radial velocity gradients, and possibly competing rotation and expansion in the equatorial disc, is discussed. In general,the flux of matter is found to reach a broad maximum at distances of the order of 500 AU from the star.Arguments are given that may be used to favour one wind velocity distribution over another. As a result of the improved quality of the data, a deeper understanding of the constraints imposed on morphology and kinematics has been obtained.
Atacama Large Millimetre/sub-millimetre Array(ALMA) observations of CO(1–0) and CO(2–1) emissions from the circumstellar envelope of the asymptotic giant branch(AGB) star EP Aqr have been made with four times better spatial resolution than previously available. They are analysed with emphasis on the de-projection in space of the effective emissivity and flux of matter using as input a prescribed configuration of the velocity field, assumed to be radial. The data are found to display an intrinsic axisymmetry with respect to an axis making a small angle with respect to the line of sight. A broad range of wind configurations, from prolate(bipolar) to oblate(equatorial) has been studied and found to be accompanied by significant equatorial emission. Qualitatively, the effective emissivity is enhanced near the equator to produce the central narrow component observed in the Doppler velocity spectra and its dependence on star latitude generally follows that of the wind velocity with the exception of an omni-present depression near the poles. In particular, large equatorial expansion velocities produce a flared disc or a ring of effective emissivity and mass loss. The effect on the determination of the orientation of the star axis of radial velocity gradients, and possibly competing rotation and expansion in the equatorial disc, is discussed. In general,the flux of matter is found to reach a broad maximum at distances of the order of 500 AU from the star.Arguments are given that may be used to favour one wind velocity distribution over another. As a result of the improved quality of the data, a deeper understanding of the constraints imposed on morphology and kinematics has been obtained.
引文
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Mamon,G.A.,Glassgold,A.E.,&Huggins,P.J.1988,ApJ,328,797
Mastrodemos,N.,&Morris,M.1999,ApJ,523,357
Nakashima,J.-i.2006,ApJ,638,1041
Nhung,P.T.,Hoai,D.T.,Winters,J.M.,et al.2015,A&A,583,A64
Nhung,P.T.,Hoai,D.T.,Diep,P.N.,et al.2016,MNRAS,460,673
Nhung,P.T.,Hoai,D.T.,Tuan-Anh,P.,et al.2018,MNRAS,480,3324
Theuns,T.,&Jorissen,A.1993,MNRAS,265,946
van Leeuwen,F.,ed.2007,Astrophysics and Space Science Library,350,Hipparcos,the New Reduction of the Raw Data
Winters,J.M.,Le Bertre,T.,Jeong,K.S.,Nyman,L.-?A.,&Epchtein,N.2003,A&A,409,715
Winters,J.M.,Le Bertre,T.,Pety,J.,&Neri,R.2007,A&A,475,559
1http://casa.nrao.edu
2 https://www.iram.fr/IRAMFR/GILDAS
Cami,J.,Yamamura,I.,de Jong,T.,et al.2000,A&A,360,562
Castro-Carrizo,A.,Quintana-Lacaci,G.,Neri,R.,et al.2010,A&A,523,A59
Cox,N.L.J.,Kerschbaum,F.,van Marle,A.-J.,et al.2012,A&A,537,A35
Diep,P.N.,Phuong,N.T.,Hoai,D.T.,et al.2016,MNRAS,461,4276
Hoai,D.T.,Matthews,L.D.,Winters,J.M.,et al.2014,A&A,565,A54
Knapp,G.R.,Young,K.,Lee,E.,&Jorissen,A.1998,ApJS,117,209
Le Bertre,T.,&G′erard,E.2004,A&A,419,549
Le Bertre,T.,Hoai,D.T.,Nhung,P.T.,&Winters,J.M.2016,in SF2A-2016:Proceedings of the Annual meeting of the French Society of Astronomy and Astrophysics,eds.C.Reyl′e,J.Richard,L.Cambr′esy,M.Deleuil,E.P′econtal,L.Tresse,&I.Vauglin,433
Lebzelter,T.,&Hron,J.1999,A&A,351,533
Libert,Y.,Winters,J.M.,Le Bertre,T.,G′erard,E.,&Matthews,L.D.2010,A&A,515,A112
Mamon,G.A.,Glassgold,A.E.,&Huggins,P.J.1988,ApJ,328,797
Mastrodemos,N.,&Morris,M.1999,ApJ,523,357
Nakashima,J.-i.2006,ApJ,638,1041
Nhung,P.T.,Hoai,D.T.,Winters,J.M.,et al.2015,A&A,583,A64
Nhung,P.T.,Hoai,D.T.,Diep,P.N.,et al.2016,MNRAS,460,673
Nhung,P.T.,Hoai,D.T.,Tuan-Anh,P.,et al.2018,MNRAS,480,3324
Theuns,T.,&Jorissen,A.1993,MNRAS,265,946
van Leeuwen,F.,ed.2007,Astrophysics and Space Science Library,350,Hipparcos,the New Reduction of the Raw Data
Winters,J.M.,Le Bertre,T.,Jeong,K.S.,Nyman,L.-?A.,&Epchtein,N.2003,A&A,409,715
Winters,J.M.,Le Bertre,T.,Pety,J.,&Neri,R.2007,A&A,475,559
1http://casa.nrao.edu
2 https://www.iram.fr/IRAMFR/GILDAS