The parameters of planetary nebulae and their central stars derived from observations

Abstract

On the basis of data on planetary nebula (PN) central star temperatures obtained by measurements in the ultraviolet (UV) range, the empirical calibration dependence between the number of Lyman photons emitted by a central starS′ and PN diameterD, is constructed. The temperatures of 118 PN central stars are estimated with this dependence. It is shown that the central star masses are distributed in a wide interval from ≈0.5 to ≈1.2M⊙. About 60% of all stars have masses 0.6M⊙ and the remainder have masses ∼0.6M⊙. The averaged empirical tracks of evolution of low-mass ( 0.6M⊙) central stars differing considerably from each other are constructed. It is shown that the majority of central stars may possess hot chromospheres (T>2×105 K) which spread for several tens of radii of the central star. The PN originates as a result of ionization of the matter ejected by a red giant at the superwind stage. The cause for this ionization is the UV radiation of the PN central star.