We present an analysis of the evolution of circumstellar dust and molecules in the environment of the very late thermal pulse object V4334 Sgr (Sakurai's object) over an ∼20-yr period, drawing on ground-, airborne-, and space-based infrared photometry and spectroscopy. The dust emission, which started in 1997, resembles a blackbody that cooled from ∼1200 K in 1998 August to ∼180 K in 2016 July. The dust mass, assuming amorphous carbon, was ∼5 × 10-10M⊙ in 1998 August, and we estimate that the total dust mass was ∼2 × 10-5M⊙ by ∼2016. The appearance of a near-infrared excess in 2008 suggests that a new episode of (or renewed) mass-loss began then. We infer lower limits on the bolometric luminosity of the embedded star from that of the dust shell, which rose to ∼16 000 L⊙ before declining to ∼3000 L⊙. There is evidence for weak 6-7 μmabsorption, which we attribute to hydrogenated amorphous carbon formed in material ejected by Sakurai's object during a mass ejection phase that preceded the 1997 event.We detect small hydrocarbon and other molecules in the spectra, and trace the column densities in hydrogen cyanide (HCN) and acetylene (C2H2). We use the former to determine the 12C/13C ratio to be 6.4 ± 0.7, 14 times smaller than the Solar system value.
Bibliographical noteFunding Information:
Based in part on observations made with the NASA/DLR SOFIA. SOFIA is jointly operated by the Universities Space Research Association, Inc. (USRA), under NASA contract NNA17BF53C, and the Deutsches SOFIA Institut (DSI) under DLR contract 50 OK 0901 to the University of Stuttgart.
This publication makes use of data products from the WISE, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration.
It also makes use of data products from the 2MASS, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation.
RDG was supported by NASA and the United States Air Force. CEW acknowledges support from SOFIA and NASA. DPKB is supported by a CSIR Emeritus Scientist grant-in-aid, which is being hosted by the Physical Research Laboratory, Ahmedabad. TRG’s research is supported by the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), Ministério da Ciência, Tec-nologia e Inovac¸ão (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). PJS thanks the Leverhulme Trust for the award of a Leverhulme Emeritus Fellowship. SS acknowledges partial support from NASA and HST grants to ASU. TL acknowledges financial support from Grantová agentura Cˇ eské republiky (GACˇ R) (grant number 17-02337S). The Astronomical Institute Ondˇejov is supported by the project RVO:67985815. This project has received funding from the European Union’s Framework Programme for Research and Innovation Horizon 2020 (2014-2020) under the Marie Skłodowska-Curie Grant Agreement No. 823734.
- Circumstellar matter
- Infrared: stars
- Stars: AGB and post-AGB
- Stars: carbon
- Stars: evolution
- Stars: individual, V4334 Sgr (Sakurai's object)