The rapid evolution of the exciting star of the Stingray nebula
Abstract
Context.
Aims: A comprehensive model-atmosphere analysis of UV and optical spectra taken during 1988-2006 should reveal the detailed temporal evolution of its atmospheric parameters and provide explanations for the unusually fast evolution.
Methods: Fitting line profiles from static and expanding non-LTE model atmospheres to the observed spectra allowed us to study the temporal change of effective temperature, surface gravity, mass-loss rate, and terminal wind velocity. In addition, we determined the chemical composition of the atmosphere.
Results: We find that the central star has steadily increased its effective temperature from 38 kK in 1988 to a peak value of 60 kK in 2002. During the same time, the star was contracting, as concluded from an increase in surface gravity from log g = 4.8 to 6.0 and a drop in luminosity. Simultaneously, the mass-loss rate declined from log (Ṁ/M⊙ yr-1) = -9.0 to -11.6 and the terminal wind velocity increased from v∞ = 1800 km s-1 to 2800 km s-1. Since around 2002, the star stopped heating and has cooled down again to 55 kK by 2006. It has a largely solar surface composition with the exception of slightly subsolar carbon, phosphorus, and sulfur. The results are discussed by considering different evolutionary scenarios.
Conclusions: The position of
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- May 2014
- DOI:
- 10.1051/0004-6361/201323189
- arXiv:
- arXiv:1403.6056
- Bibcode:
- 2014A&A...565A..40R
- Keywords:
-
- stars: abundances;
- stars: evolution;
- stars: AGB and post-AGB;
- stars: individual: SAO 244567;
- stars: fundamental parameters;
- planetary nebulae: individual: Stingray nebula (Henize 3-1357);
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 16 pages, 13 figures, accepted for publication in A&