The extended molecular envelope of the asymptotic giant branch star π1 Gruis as seen by ALMA II. The spiral-outflow observed at high-angular resolution

被引：14

作者：

Doan, L. ^{[1
]}

Ramstedt, S. ^{[1
]}

Vlemmings, W. H. T. ^{[2
]}

Mohamed, S. ^{[3
,4
,5
]}

Hofner, S. ^{[1
]}

De Beck, E. ^{[2
]}

Kerschbaum, F. ^{[6
]}

Lindqvist, M. ^{[2
]}

Maercker, M. ^{[2
]}

Paladini, C. ^{[7
]}

Wittkowski, M. ^{[8
]}

机构：

[1] Uppsala Univ, Dept Phys & Astron, Theoret Astrophys, Box 516, S-75120 Uppsala, Sweden

[2] Chalmers Univ Technol, Dept Earth & Space Sci, S-43992 Onsala, Sweden

[3] South African Astron Observ, POB 9, ZA-7935 Observatory, South Africa

[4] Univ Cape Town, Astron Dept, ZA-7701 Rondebosch, South Africa

[5] Natl Inst Theoret Phys, Private Bag X1, ZA-7602 Matieland, South Africa

[6] Univ Vienna, Dept Astrophys, Turkenschanzstr 17, A-1180 Vienna, Austria

[7] European Southern Observ, Alonso de Cordova 3107, Santiago, Chile

[8] European Southern Observ, Karl Schwarzschild Str 2, D-85748 Garching, Germany

来源：

ASTRONOMY & ASTROPHYSICS | 2020年 / 633卷

基金：

瑞典研究理事会; 新加坡国家研究基金会;

关键词：

stars: AGB and post-AGB; stars: low-mass; radio lines: general; binaries: general; stars: individual: pi(1) Gru; BIPOLAR PREPLANETARY NEBULAE; BINARY-SYSTEMS; MASS-TRANSFER; DUSTY WINDS; CIRCUMSTELLAR; HYDRODYNAMICS;

D O I：

10.1051/0004-6361/201935245

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

Context. This study is a follow up to the previous analysis of lower-angular resolution data in which the kinematics and structure of the circumstellar envelope (CSE) around the S-type asymptotic giant branch (AGB) star pi(1) Gruis were investigated. The AGB star has a known companion (at a separation of 400 AU) that cannot explain the strong deviations from spherical symmetry of the CSE. Recently, hydrodynamic simulations of mass transfer in closer binary systems have successfully reproduced the spiral-shaped CSEs found around a handful of sources. There is growing evidence for an even closer, undetected companion complicating the case of pi(1) Gruis further. Aims. The improved spatial resolution allows for the investigation of the complex circumstellar morphology and the search for imprints on the CSE of the third component. Methods. We have observed the (CO)-C-12 J = 3-2 line emission from pi(1) Gruis using both the compact and extended array of Atacama Large Millimeter/submillimeter Array (ALMA). The interferometric data have furthermore been combined with data from the ALMA total power array. The imaged brightness distribution has been used to constrain a non-local, non-local thermodynamic equilibrium 3D radiative transfer model of the CSE. Results. The high-angular resolution ALMA data have revealed the first example of a source on the AGB where both a faster bipolar outflow and a spiral pattern along the orbital plane can be seen in the gas envelope. The spiral can be traced in the low- to intermediate-velocity (13-25 km s(-1)) equatorial torus. The largest spiral-arm separation is approximate to 5.'' 5 and consistent with a companion with an orbital period of approximate to 330 yr and a separation of less than 70 AU. The kinematics of the bipolar outflow is consistent with it being created during a mass-loss eruption where the mass-loss rate from the system increased by at least a factor of five for 10-15 yr. Conclusions. The spiral pattern is the result of an undetected companion. The bipolar outflow is the result of a rather recent mass-loss eruption event.

引用

页数：11

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