Sakurai's Object: characterizing the near-infrared CO ejecta between 2003 and 2007

• Published in: Monthly notices of the Royal Astronomical Society Vol. 393; no. 1; pp. 108 - 112
• Main Authors: Worters, H. L., Rushton, M. T., Eyres, S. P. S., Geballe, T. R., Evans, A.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 2009; Wiley-Blackwell; Oxford University Press
• Subjects: Astronomy; Astrophysics; circumstellar matter; Earth, ocean, space; Exact sciences and technology; Gases; Infrared imaging systems; outflows; Stars & galaxies; stars: abundances; stars: AGB and post-AGB; stars: individual: Sakurai's Object; stars: individual: V4334 Sgr; stars: winds; stars: winds, outflows; stars: AGB and post-AGB; stars: winds, outflows; stars: abundances; stars: individual: V4334 Sgr; circumstellar matter; stars: individual: Sakurai's Object; Stellar winds; Stellar radiation; Stellar abundance; Central stars; Circumstellar matter; Planetary nebulae; Models; Radiative transfer; Excitation; Asymptotic giant branch
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1111/j.1365-2966.2008.14135.x

We present observations of Sakurai's Object obtained at 1–5 μm between 2003 and 2007. By fitting a radiative transfer model to an echelle spectrum of CO fundamental absorption features around 4.7 μm, we determine the excitation conditions in the line-forming region. We find 12C/13C = 3.5+2.0−1.5, consistent with CO originating in ejecta processed by the very late thermal pulse, rather than in the pre-existing planetary nebula. We demonstrate the existence of 2.2 × 10−6≤MCO≤ 2.7 × 10−6 M⊙ of CO ejecta outside the dust, forming a high-velocity wind of 500 ± 80 km s−1. We find evidence for significant weakening of the CO band and cooling of the dust around the central star between 2003 and 2005. The gas and dust temperatures are implausibly high for stellar radiation to be the sole contributor.