The Infrared Evolution of Sakurai's Object

Gemini Observatory; Keele University; Liverpool John Moores University
Astrophysics and Space Science (Impact Factor: 2.06). 02/2002; 279(1):39-49. DOI: 10.1023/A:1014683521291
Source: arXiv

ABSTRACT Infrared spectroscopy and photometry have revealed the remarkableevolution of Sakurai''s Object from 1996 to the present. A cooling,carbon-rich photospheric spectrum was observable from 1996 to 1998.Considerable changes occured in 1998 as the continuum reddened due toabsorption and emission by newly formed dust located outside thephotosphere. In addition, a strong and broad helium 1.083 m P Cygniline developed, signifying the acceleration of an outer envelope ofmaterial to speeds as high as 1000 km s-1. At the same time thephotosphere of the central star remained quiescent. By 1999 thephotosphere was virtually completely obscured by the dust and the heliumemission line was the only detectable spectral feature remaining in the1–5 m band. In 2000 emission by dust has become even more dominant,as the envelope continues to expand and cool and the helium line weakens.

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    ABSTRACT: We present near (ground-based) and far (ISO) infrared spectroscopy of Sakurai's object. As in the case of the optical spectrum, between 1996 and 1997 April the near-infrared spectrum underwent a dramatic change to later spectral type, and there is some evidence that the spectrum continued to evolve during 1997. Molecular features of carbon-bearing molecules (CN, C2, CO) — corresponding to those seen in cool carbon stars — are now prominent in the 1–2.5 μ m range, and the 12C/13C ratio is low. The ISO data demonstrate the presence of hot circumstellar dust at a temperature of ∼ 680 K. If the dust shell is optically thin, the dust mass is ∼ 2.8 × 10−8 M⊙.
    Monthly Notices of the Royal Astronomical Society 04/2002; 298(2):L37 - L41. · 5.52 Impact Factor
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    ABSTRACT: We report the appearance and evolution during 1998 of strong neutral helium ^3S-^3P^o absorption at ~10830Å in Sakurai's Object (V4334 Sgr), which is believed to be a planetary nebula nucleus (PNN) undergoing a final helium shell-flash. First detected on 1998 March 18, the profile of the Hei feature is P Cygni-like. The absorption depth has increased in three subsequent spectra in 1998. If this is owing to a wind, the profile indicates a wind velocity of ~670+/-50kms^-1. The strong Ci 10690-Å line seen prior to the appearance of the helium feature has disappeared; however Srii and CN absorption features remain present. We tentatively identify several new features as Sii. Taken together with other observations we suggest that the data are consistent with Sakurai's Object entering a phase in which it seems to have become a member of the R Coronae Borealis-type class of stars.
    Monthly Notices of the Royal Astronomical Society 01/1999; 307(1). · 5.52 Impact Factor

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