Identification of oxygen-rich late/post-asymptotic giant branch stars and water fountains via maser and infrared criteria

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

物理学;天文学

Yung, Bosco H.K.^1,2 ; Nakashima, Jun-Ichi^1,3 ; Henkel, Christian^4,5 ; Hsia, Chih-Hao^6,7

Department of Physics, University of Hong Kong, Pokfulam, Hong Kong^1

Nicolaus Copernicus Astronomical Center, Rabiaka 8, Toru

87-100, Poland^2

Department of Astronomy and Geodesy, Institute of Natural Science, Ural Federal University, Lenin Ave. 51, Ekaterinburg

620000, Russia^3

Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, Bonn

D-53121, Germany^4

Astronomy Department, King Abdulaziz University, P.O. Box 80203, Jeddah

21589, Saudi Arabia^5

Laboratory for Space Research, Faculty of Science, University of Hong Kong, Pokfulam, Hong Kong^6

Space Science Insitute, Macau University of Science and Technology, Avenida Wai Long, Taipa, China^7

关键词: Asymptotic giant branch;    Giant branch stars;    Identification criterion;    Planetary nebulae;    Radiative transfer modelling;    Representative object;    Spectral energy distribution;    Transitional phase;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/728/7/072005/pdf
DOI  :  10.1088/1742-6596/728/7/072005

学科分类：天文学(综合)

来源: IOP

【 摘 要 】

The transitional phase between the asymptotic giant branch (AGB) and post-AGB phases holds the key to our understanding of the late-stage metamorphosis of intermediate-mass stars. In particular, high velocity jets forming during this phase are suggested to contribute significantly to the shaping of planetary nebulae. For oxygen-rich stars, the rare "water fountains (WFs)" have been regarded as representative objects in this phase, and it is important to identify more of them for further studies. Here we briefly report the results of our latest OH and H2O maser surveys in which a new WF candidate (IRAS 19356+0754) was found. We also performed radiative transfer modelling on the spectral energy distributions (SEDs) of all known WFs. It is concluded that WFs might in fact not be the transitional objects, as opposed to previous belief. WFs could be AGB or post-AGB stars with no obvious similarities amongst their SEDs. Further efforts are still needed to improve the identification criteria.