Evidence for episodic and patchy mass ejection in the circumstellar envelope of AGB star R Leonis

被引:2
作者
Hoai, D. T. [1 ]
Nhung, P. T. [1 ]
Tan, M. N. [1 ]
Darriulat, P. [1 ]
Diep, P. N. [1 ,2 ]
Ngoc, N. B. [1 ]
Thai, T. T. [1 ]
Tuan-Anh, P. [1 ,2 ]
机构
[1] Vietnam Acad Sci & Technol, Dept Astrophys, Vietnam Natl Space Ctr, 18 Hoang Quoc Wet, Hanoi, Vietnam
[2] Grad Univ Sci & Technol GUST, Vietnam Acad Sci & Technol VAST, 18 Hoang Quoc Viet, Hanoi, Vietnam
关键词
stars: AGB and post-AGB; circumstellar matter; stars: individual: R Leonis; radio lines: stars; MIRA VARIABLES; SIO MASERS; LINE EMISSION; K-BAND; O-RICH; PULSATION; POLARIZATION; SPECTROSCOPY; TEMPERATURES; ATMOSPHERE;
D O I
10.1093/mnras/stac3176
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
The morpho-kinematics of the circumstellar envelope of oxygen-rich AGB star R Leonis is probed using Atacama Large Millimeter/submillimeter Array observations of the emission of molecular lines, including in particular CO(2-1) and (SiO)-Si-29(5-4). Evidence is found for an episode of enhanced mass-loss, a few centuries ago, that produced a broad expanding shell of mean radius similar to 6 arcsec and mean radial expansion velocity similar to 5.5 km s(-1). Detailed scrutiny of its structure, as displayed by the emission of the CO(2-1) line, reveals strong inhomogeneity and patchy morphology. Evidence is also found, in particular from the morpho-kinematics of the emission of SiO, SO, and SO2 lines probing the close neighbourhood of the star, for distinct gas outflows covering broad solid angles in the south-eastern, south-western, and north-western quadrants, suggesting significant contribution of the convective cell granulation in defining the pattern of mass ejection. A study of relative molecular abundances in these outflows suggests that a local thermal equilibrium description applies approximately beyond similar to 10 stellar radii from the centre of the star but not at the smaller angular separations where the SO and SO2 molecules are found to be confined. Near the stellar disc, masers of the vibrationally excited SiO lines are found to probe north-western parts of a layer of hot gas, consistent with the earlier observation of an asymmetric expanding shell within 1-2 stellar radii from the centre of the star. Globally, a picture dominated by episodic and patchy mass ejections is found to prevail.
引用
收藏
页码:2034 / 2049
页数:16
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