ALMA observations of the not-so detached shell around the carbon AGB star R Sculptoris

11th Pacific Rim Conference on Stellar Astrophysics: Physics and Chemistry of the Late Stages of Stellar Evolution

物理学;天文学

Maercker, Matthias^1

Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, Onsala

43992, Sweden^1

关键词: Binary systems;    Chemical evolution;    Direct measurement;    Driving mechanism;    Fundamental period;    Mass loss rate;    Optical observations;    Stellar evolutions;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/728/2/022006/pdf
DOI  :  10.1088/1742-6596/728/2/022006

学科分类：天文学(综合)

来源: IOP

【 摘 要 】

I present our ALMA observations of the CO emission around the carbon AGB star R Sculptoris. The data reveal the known detached shell and a previously unknown, binary induced, spiral shape. The observations confirm a formation of the shell during a thermal pulse about 2300 years ago. The full analysis of the ALMA data shows that the shell around R Scl in fact is entirely filled with molecular gas, and hence not as detached as previously thought. This has implications for the mass-loss rate evolution immediately after the pulse, indicating a much higher mass-loss rate than previously assumed. Comparing the ALMA images to our optical observations of polarised, dust scattered light, we further show that the distributions of the dust and gas coincide almost perfectly, implying a common evolution of the dust and gas, and constraining the wind-driving mechanism. The mass-loss process and amount of mass lost during the thermal pulse cycle affect the chemical evolution of the star, its lifetime on the AGB, and the return of heavy elements to the ISM. New high-resolution ALMA observations constrain the parameters of the binary system and the inner spiral, and will allow for a detailed hydrodynamical modelling of the gas and dust during and after the last thermal pulse. Our results present the only direct measurements of the thermal pulse evolution currently available. They greatly increase our understanding of this fundamental period of stellar evolution, and the implications it has for the chemical evolution of evolved stars, the ISM, and galaxie.