August 11-15, 2014


From a giant towards a white dwarf at record speed: The rapid evolution of the central star of the Stingray nebula.

Nicole Reindl (University of Tübingen)

T. Rauch (University of Tübingen), M. Parthasarathy (Inter-University Centre for Astronomy and Astrophysics, Pune), K. Werner (University of Tübingen), J. W. Kruk (NASA Goddard Space Flight Center)

SAO244567, the exciting star of the Stingray nebula, is an unusually fast evolving star. Within twenty years only, SAO 244567 has turned from a B-type supergiant into a central star of planetary nebula. For the first time we present a comprehensive spectral analysis by means of state-of-the-art NLTE models for static and expanding atmospheres based on all available spectra from 1988 until 2006. We determined the temporal evolution of its effective temperature, surface gravity, mass-loss rate, and photospheric abundances. By comparison with stellar-evolution calculations, we confirm the previous findings, that SAO 244567 must be a low-mass star (M < 0.55 M_sun). The observed fast evolution and the young planetary nebula with kinematical age of only about 1000 years is in strong contradiction with canonical post-asymptotic giant branch evolution. We speculate that the star could be a late He-shell flash object or alternatively, it could be the outcome of close-binary evolution, being a low-mass (0.354 M_sun) helium pre-white dwarf after the common-envelope phase, during which the planetary nebula was ejected.

Mode of presentation: poster