The Infrared Evolution of Sakurai's Object

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 μm 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 μm band. In 2000 emission by dust has become even more dominant,as the envelope continues to expand and cool and the helium line weakens.