Recent mass ejection from AGB star W Hya
We analyse archival ALMA (Atacama Large Millimeter/submillimeter Array) observations of two molecular line emissions, 12CO(3-2) and 29SiO(8-7), from oxygen-rich AGB (Asymptotic Giant Branch) star W Hya. Together with results of earlier VLT observations at visible and infrared wavelengths, our resul...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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Vietnam Ministry of Science and Technology
2022-12-01
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| Series: | Vietnam Journal of Science, Technology and Engineering |
| Subjects: | |
| Online Access: | https://vietnamscience.vjst.vn/index.php/vjste/article/view/1078 |
| _version_ | 1797937809195008000 |
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| author | D.T. Hoai P.T. Nhung P. Darriulat P.N. Diep N.B. Ngoc T.T. Thai P. Tuan-Anh |
| author_facet | D.T. Hoai P.T. Nhung P. Darriulat P.N. Diep N.B. Ngoc T.T. Thai P. Tuan-Anh |
| author_sort | D.T. Hoai |
| collection | DOAJ |
| description |
We analyse archival ALMA (Atacama Large Millimeter/submillimeter Array) observations of two molecular line emissions, 12CO(3-2) and 29SiO(8-7), from oxygen-rich AGB (Asymptotic Giant Branch) star W Hya. Together with results of earlier VLT observations at visible and infrared wavelengths, our results suggest a two-component picture of the morpho-kinematics of the circumstellar envelope (CSE), one stable over time, at the scale of centuries, and the other variable, at the scale of years. The stable component consists of an approximately spherical shell of gas and dust expanding radially to a terminal velocity of ~5 km s−1 at a distance of ~30 au from the star. It is found to display comparable features as seen in the CSE of R Dor, a star similar to W Hya. The variable component projects on the plane of the sky over a region confined to the neighbourhood of the star and elongated toward the north. Its very high density and sudden acceleration suggest an interpretation in terms of mass ejection initiated a few years ago. We discuss its properties in relation with earlier observations of dust formation in the same region. Our results offer a picture of the wind of W Hya that differs significantly from the picture that could be suggested by earlier analyses, giving evidence for a mass ejection that had been previously overlooked and underscoring new relations between the dust and gas emissions. They have an impact on the evidence published earlier for the presence of CO masers. They favour an interpretation in terms of convective cell ejections playing the main role in the generation of the nascent wind, the stable component of the CSE being seen as the result of many successive such events occurring in different directions at short time intervals.
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| first_indexed | 2024-04-10T18:50:02Z |
| format | Article |
| id | doaj.art-1b609500cbff4ea3972192d7d491eb2b |
| institution | Directory Open Access Journal |
| issn | 2525-2461 2615-9937 |
| language | English |
| last_indexed | 2024-04-10T18:50:02Z |
| publishDate | 2022-12-01 |
| publisher | Vietnam Ministry of Science and Technology |
| record_format | Article |
| series | Vietnam Journal of Science, Technology and Engineering |
| spelling | doaj.art-1b609500cbff4ea3972192d7d491eb2b2023-02-01T08:10:41ZengVietnam Ministry of Science and TechnologyVietnam Journal of Science, Technology and Engineering2525-24612615-99372022-12-0164410.31276/VJSTE.64(4).16-27Recent mass ejection from AGB star W HyaD.T. HoaiP.T. NhungP. DarriulatP.N. DiepN.B. NgocT.T. ThaiP. Tuan-Anh We analyse archival ALMA (Atacama Large Millimeter/submillimeter Array) observations of two molecular line emissions, 12CO(3-2) and 29SiO(8-7), from oxygen-rich AGB (Asymptotic Giant Branch) star W Hya. Together with results of earlier VLT observations at visible and infrared wavelengths, our results suggest a two-component picture of the morpho-kinematics of the circumstellar envelope (CSE), one stable over time, at the scale of centuries, and the other variable, at the scale of years. The stable component consists of an approximately spherical shell of gas and dust expanding radially to a terminal velocity of ~5 km s−1 at a distance of ~30 au from the star. It is found to display comparable features as seen in the CSE of R Dor, a star similar to W Hya. The variable component projects on the plane of the sky over a region confined to the neighbourhood of the star and elongated toward the north. Its very high density and sudden acceleration suggest an interpretation in terms of mass ejection initiated a few years ago. We discuss its properties in relation with earlier observations of dust formation in the same region. Our results offer a picture of the wind of W Hya that differs significantly from the picture that could be suggested by earlier analyses, giving evidence for a mass ejection that had been previously overlooked and underscoring new relations between the dust and gas emissions. They have an impact on the evidence published earlier for the presence of CO masers. They favour an interpretation in terms of convective cell ejections playing the main role in the generation of the nascent wind, the stable component of the CSE being seen as the result of many successive such events occurring in different directions at short time intervals. https://vietnamscience.vjst.vn/index.php/vjste/article/view/1078circumstellar matterradio lines: starsstars: AGB and post-AGBstars: individual: W Hya |
| spellingShingle | D.T. Hoai P.T. Nhung P. Darriulat P.N. Diep N.B. Ngoc T.T. Thai P. Tuan-Anh Recent mass ejection from AGB star W Hya Vietnam Journal of Science, Technology and Engineering circumstellar matter radio lines: stars stars: AGB and post-AGB stars: individual: W Hya |
| title | Recent mass ejection from AGB star W Hya |
| title_full | Recent mass ejection from AGB star W Hya |
| title_fullStr | Recent mass ejection from AGB star W Hya |
| title_full_unstemmed | Recent mass ejection from AGB star W Hya |
| title_short | Recent mass ejection from AGB star W Hya |
| title_sort | recent mass ejection from agb star w hya |
| topic | circumstellar matter radio lines: stars stars: AGB and post-AGB stars: individual: W Hya |
| url | https://vietnamscience.vjst.vn/index.php/vjste/article/view/1078 |
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