We present a 0.8-2.5 μm spectrum of the very late thermal pulse object V4334 Sgr (Sakurai's Object), obtained in 2020 September. The spectrum displays a continuum that rises strongly to longer wavelengths, and is considerably brighter than the most recent published spectrum obtained 7 yr earlier. At the longer wavelengths, the continuum is well fitted by a blackbody with a temperature of 624 ± 8 K. However, there is excess continuum at the shortest wavelengths that we interpret as being due to hot dust that has very recently formed in an environment with C/O ≃ 2.5. Other possible sources for this excess continuum are discussed - such as the stellar photosphere dimly seen through the dust shell, and light scattered off the inner wall of the dust torus - but these interpretations seem unlikely. Numerous emission lines are present, including those of He i, C i, [C i], and O i. Our observations confirm that emission in the He i 1.083 μm and [C i] 0.9827/0.9852 μm lines is spatially extended. The [C i] line fluxes suggest that the electron density increased by an order of magnitude between 2013 and 2020, and that these two lines may soon disappear from the spectrum. The flux ratio of the 1.083 and 2.058 μm He i lines is consistent with the previously assumed interstellar extinction. The stellar photosphere remains elusive, and the central star may not be as hot as suggested by current evolutionary models.
|Original language||English (US)|
|Number of pages||10|
|Journal||Monthly Notices of the Royal Astronomical Society|
|State||Published - Mar 1 2022|
Bibliographical noteFunding Information:
Visiting Astronomer at the Infrared Telescope Facility, which is operated by the University of Hawaii under contract 80HQTR19D0030 with the National Aeronautics and Space Administration.
ACKNOWLEDGEMENTS This paper is based on observations obtained at the international Gemini Observatory, a programme of NSF's NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation, on behalf of the Gemini Observatory partner- ship: the National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Inno- vación (Argentina), Ministério da Ciência, Tecnologia, Inova ções e Comunica ções (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). Data were also obtained under IRTF programmes 2020A-001 and 2020A-010. The Infrared Telescope Facility is operated by the University of Hawaii under contract 80HGTR19D0030 with the National Aeronautics and Space Administration. DPKB was supported by a CSIR Emeritus Scientist grant-in- aid and is being hosted by the Physical Research Laboratory, Ahmedabad. RDG was supported by the United States Airforce. CEW was supported by USRA/Sofia contract SOF 07-0027 (NASA prime award NNA17BF53C). This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France
© 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.
- circumstellar matter
- infrared: stars
- stars: AGB and post-AGB
- stars: carbon
- stars: evolution
- stars: individual: V4334 Sgr (Sakurai's Object)