New analyses of earlier ALMA observations of oxygen-rich AGB star EP Aquarii are presented,which complete a previously published analysis and offer a different interpretation of the morpho-kinematics of the circumstel...New analyses of earlier ALMA observations of oxygen-rich AGB star EP Aquarii are presented,which complete a previously published analysis and offer a different interpretation of the morpho-kinematics of the circumstellar envelope.The birth of the equatorial density enhancement(EDE)is shown to occur very close to the star where evidence for rotation has been obtained.Close to the star and where outflows have been observed:their interaction with the gas of the nascent EDE is seen to play an important role in the development of the wind and the evolution of its radial velocity from 8 to 10 km s^(-1) on the polar symmetry axis to~2 km s^(-1) at the equator.It implies complex morpho-kinematics:making reliable interpretations with reasonable confidence is difficult.In particular,it questions an earlier interpretation implying the presence of a white dwarf companion orbiting the star at an angular distance of -0″4 from its center.It proposes instead an interpretation in terms of a standard mass ejection associated with a shock wave leaving a void of emission in its wake.High Doppler velocity wings are seen to consist of two components,the upper velocity end of the global wind,reaching above±12 km s^(-1),and an effective line broadening,confined within 200 mas from the center of the star,reaching above±20 km s^(-1) and interpreted as caused by the pattern of shock waves resulting from the interaction between stellar pulsation and convective cell partition.展开更多
Imaging studies with the Very Large Array（VLA） have revealed H I emission associated with the extended circumstellar shells of red giants. We analyze the spectral map obtained on Y CVn, a J-type carbon star on the A...Imaging studies with the Very Large Array（VLA） have revealed H I emission associated with the extended circumstellar shells of red giants. We analyze the spectral map obtained on Y CVn, a J-type carbon star on the Asymptotic Giant Branch. The H I line profiles can be interpreted with a model of a detached shell resulting from the interaction of a stellar outflow with the local interstellar medium.We reproduce the spectral map by introducing a distortion along a direction corresponding to the star＇s motion in space. We then use this fitting to simulate observations expected from the Five-hundred-meter Aperture Spherical radio Telescope（FAST）, and discuss its potential for improving our description of the outer regions of circumstellar shells.展开更多
基金funded by the Vietnam Academy of Science and Technology(VAST)under grant No.NVCC39.01/24-25。
文摘New analyses of earlier ALMA observations of oxygen-rich AGB star EP Aquarii are presented,which complete a previously published analysis and offer a different interpretation of the morpho-kinematics of the circumstellar envelope.The birth of the equatorial density enhancement(EDE)is shown to occur very close to the star where evidence for rotation has been obtained.Close to the star and where outflows have been observed:their interaction with the gas of the nascent EDE is seen to play an important role in the development of the wind and the evolution of its radial velocity from 8 to 10 km s^(-1) on the polar symmetry axis to~2 km s^(-1) at the equator.It implies complex morpho-kinematics:making reliable interpretations with reasonable confidence is difficult.In particular,it questions an earlier interpretation implying the presence of a white dwarf companion orbiting the star at an angular distance of -0″4 from its center.It proposes instead an interpretation in terms of a standard mass ejection associated with a shock wave leaving a void of emission in its wake.High Doppler velocity wings are seen to consist of two components,the upper velocity end of the global wind,reaching above±12 km s^(-1),and an effective line broadening,confined within 200 mas from the center of the star,reaching above±20 km s^(-1) and interpreted as caused by the pattern of shock waves resulting from the interaction between stellar pulsation and convective cell partition.
基金the Vietnam National Satellite Centre(VNSC/VAST)the NAFOSTED funding agency+3 种基金the World Laboratorythe Odon Vallet Foundationthe Rencontres du Viet Namthe PCMI programme of the CNRS for financial support
文摘Imaging studies with the Very Large Array（VLA） have revealed H I emission associated with the extended circumstellar shells of red giants. We analyze the spectral map obtained on Y CVn, a J-type carbon star on the Asymptotic Giant Branch. The H I line profiles can be interpreted with a model of a detached shell resulting from the interaction of a stellar outflow with the local interstellar medium.We reproduce the spectral map by introducing a distortion along a direction corresponding to the star＇s motion in space. We then use this fitting to simulate observations expected from the Five-hundred-meter Aperture Spherical radio Telescope（FAST）, and discuss its potential for improving our description of the outer regions of circumstellar shells.
