Masses of the Central Stars of Planetary Nebulae

The physical structure of the planetary nebula NGC 6781

“…However, it is clear that the comparison is restricted by the lack of kinematic data and the uncertainties in the distance and the central star properties. In addition, we note that Górny et al (1997) estimate a mass of 0.57 M and an age of ∼17 000 yrs following the formation of the planetary nebula, whereas Gathier and Pottasch's (1989) evolutionary tracks suggest a mass of ∼0.546 M and a time interval of 320 000-400 000 yrs since the temperature of the star was 10 3.7 K. Their results also show that the evolutionary track of a star with the slightly higher mass of 0.565 M at ∼25 000-40 000 yrs after its temperature was 10 3.7 K, is relatively close to current estimates of the central star's temperature and luminosity. It is evident that small changes in the mass of the central star leads to significant variations in the evolutionary times.…”

“…Measurements of the central star properties in NGC 6781 suggest a temperature of ∼100 000 K and a luminosity of ∼200 L indicative of an evolved system according to the evolutionary tracks of Gathier & Pottasch (1989) and Górny et al (1997). This implies that this planetary has most likely, passed, the turn-around point and is in the stage where the luminosity of the central star continously decreases until it fades as a white-dwarf.…”

“…The optical extent of the main nebula is ∼95 , while the optical halo has a much larger extent, around 180 ×109 (Chu et al 1987). Górny et al (1997) studied the properties of the central stars of 72 PNe through models of stellar evolution. The authors estimate a temperature of ∼10 5 K, a luminosity of ∼200 L and an evolutionary time scale of ∼17 000 yr for the central star in NGC 6781.…”

Stellar Evolution and Nucleosynthesis of Post-AGB Stars

“…Planetary nebulae (PNe) of [WC]-type central stars are on average not older than PNe surrounding chemically normal central stars (Gorny and Stasinska, 1995). This indicates that these objects are on their first evolutionary departure from the AGB.…”

The Validity of Mass Functions for the Central Stars of Planetary Nebulae

“…A variety of analyses have been used to constrain PN central-star masses and conÐrm their similarity to those of white dwarfs, including investigations of PN locations within the H-R plane (Kaler 1983 ;Kaler et al 1990 ;Kaler & Jacoby 1990, 1991Dopita & Meatheringham 1991), of the variation of radio brightness temperatures with Zanstra temperatures (Gorny et al 1993), using Monte Carlo simulations of the Galactic bulge population , comparing observed and theoretical I(He II j4686)/I(Hb) ratios (Szczerba 1987(Szczerba , 1990, investigating the variations of distance-independent parameters (Tylenda & Stasinska 1989 ;Gorny et al 1993 ;Zhang & Kwok 1993), using mixes of di †ering procedures , and so forth. All of these concur in Ðnding that PN masses are more or less concentrated about M CS \ 0.6 M _ ; although the various analyses also indicate di †ering strengths for the higher mass "" tail.ÏÏ Perhaps the most inÑu-ential of all of these methods, however, and the one that has certainly spawned the most imitators, is the one originally proposed by (1981 Weidemann & Koester (1984).…”