scholarly journals White Dwarf Central Stars of Planetary Nebulae

2003 ◽  
Vol 209 ◽  
pp. 211-214
Author(s):  
Ralf Napiwotzki
Keyword(s):  
White Dwarf ◽  
Spectroscopic Investigation ◽  
Planetary Nebulae ◽  
Distance Scale ◽  
Binary Interaction ◽  
Evolutionary Status ◽  
Central Stars ◽  
Good Agreement

Results of a spectroscopic investigation of central stars of old planetary nebulae (PNe) are reported. The evolutionary status of the central stars is discussed and it is shown that most are in good agreement with standard post-AGB evolution, but some are best explained as descendents from the first RGB after binary interaction. The distance scale of PNe is discussed.

scholarly journals Evolutionary Tracks for Central Stars of Planetary Nebulae

1989 ◽  
Vol 131 ◽  
pp. 463-472 ◽  
Author(s):  
Detlef Schönberner
Keyword(s):  
Mass Loss ◽  
White Dwarf ◽  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
Helium Burning ◽  
Hydrogen Burning ◽  
Stellar Envelope ◽  
Thermal Pulse ◽  
Pulse Cycle ◽  
Central Stars

Our understanding of the evolution of Central Stars of Planetary Nebulae (CPN) has made considerable progress during the last years. This was possible since consistent computations through the asymptotic giant branch (AGB), with thermal pulses and (in some cases) mass loss taken into account, became available (Schönberner, 1979, 1983; Kovetz and Harpaz, 1981; Harpaz and Kovetz, 1981; Iben, 1982, 1984; Wood and Faulkner, 1986). It turned out that the evolution depends very sensitively on the inital conditions on the AGB. More precisely, the evolution of an AGB remnant is a function of the phase of the thermal-pulse cycle during which this remnant was created on the tip of the AGB by the planetary-nebula (PN) formation process (Iben, 1984, 1987). This was first shown by Schönberner (1979), and then fully explored by Iben (1984). In short, two major modes of PAGB evolution to the white dwarf stage are possible, according to the two main phases of a thermally pulsing AGB star: the hydrogen-burning or helium-burning mode. If, for instance, the PN formation, i.e. the removal of the stellar envelope by mass loss, happens during a luminosity peak that follows a thermal pulse of the helium-burning shell, the remnant leaves the AGB while still burning helium as the main energy supplier (Härm and Schwarzschild, 1975). On the other hand, PN formation may also occur during the quiescent hydrogen-burning phase on the AGB, and the remnant continues then to burn mainly hydrogen on its way to becoming a white dwarf.

scholarly journals An imaging and spectroscopic survey of the Abell Planetary Nebulae

1997 ◽  
Vol 180 ◽  
pp. 287-287
Author(s):  
N. A. Walton ◽  
J. R. Walsh ◽  
G. Dudziak
Keyword(s):  
White Dwarf ◽  
Surface Brightness ◽  
Planetary Nebulae ◽  
Central Star ◽  
Large Size ◽  
Low Surface Brightness ◽  
Thermal Pulses ◽  
Central Stars

The Abell catalogue of planetary nebulae (PN) are distinguished by their large size, low surface brightness and generally faint central stars. They are thought to be old PN approaching the White Dwarf cooling track. A number have evidence for late thermal pulses (H-poor ejecta near the central star, e.g. A78) and binary central stars.

scholarly journals NLTE analysis of central stars of highly excited Planetary Nebulae

1997 ◽  
Vol 180 ◽  
pp. 132-132
Author(s):  
T. Rauch ◽  
J. Köppen ◽  
R. Napiwotzki ◽  
K. Werner
Keyword(s):  
White Dwarfs ◽  
State Of The Art ◽  
Planetary Nebulae ◽  
Evolutionary Status ◽  
Agb Stars ◽  
Spectral Analyses ◽  
Central Stars

Very hot central stars (CSPN) of highly excited planetary nebulae (PN) display directly the formation of white dwarfs. Only a few of these CSPN have been analyzed so far due to their low brightness and thus, the interpretation of their evolutionary status is hampered by statistical incompleteness. In the last decade many spectral analyses of very hot post-AGB stars by means of state-of-the-art NLTE model atmospheres have been performed (e.g. Rauch et al. 1996; Werner & Rauch 1994; Rauch & Werner 1995) and our picture of post-AGB evolution has been improved.

scholarly journals Stellar wind models of central stars of planetary nebulae

2020 ◽  
Vol 635 ◽  
pp. A173 ◽  
Author(s):  
J. Krtička ◽  
J. Kubát ◽  
I. Krtičková
Keyword(s):  
Mass Loss ◽  
White Dwarf ◽  
Planetary Nebula ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Planetary Nebulae ◽  
Terminal Velocity ◽  
Asymptotic Giant Branch ◽  
Central Stars ◽  
Loss Rates

Context. Fast line-driven stellar winds play an important role in the evolution of planetary nebulae, even though they are relatively weak. Aims. We provide global (unified) hot star wind models of central stars of planetary nebulae. The models predict wind structure including the mass-loss rates, terminal velocities, and emergent fluxes from basic stellar parameters. Methods. We applied our wind code for parameters corresponding to evolutionary stages between the asymptotic giant branch and white dwarf phases for a star with a final mass of 0.569 M⊙. We study the influence of metallicity and wind inhomogeneities (clumping) on the wind properties. Results. Line-driven winds appear very early after the star leaves the asymptotic giant branch (at the latest for Teff ≈ 10 kK) and fade away at the white dwarf cooling track (below Teff = 105 kK). Their mass-loss rate mostly scales with the stellar luminosity and, consequently, the mass-loss rate only varies slightly during the transition from the red to the blue part of the Hertzsprung–Russell diagram. There are the following two exceptions to the monotonic behavior: a bistability jump at around 20 kK, where the mass-loss rate decreases by a factor of a few (during evolution) due to a change in iron ionization, and an additional maximum at about Teff = 40−50 kK. On the other hand, the terminal velocity increases from about a few hundreds of km s−1 to a few thousands of km s−1 during the transition as a result of stellar radius decrease. The wind terminal velocity also significantly increases at the bistability jump. Derived wind parameters reasonably agree with observations. The effect of clumping is stronger at the hot side of the bistability jump than at the cool side. Conclusions. Derived fits to wind parameters can be used in evolutionary models and in studies of planetary nebula formation. A predicted bistability jump in mass-loss rates can cause the appearance of an additional shell of planetary nebula.

scholarly journals New kinematic distance scale for the Galactic planetary nebulae

2011 ◽  
Vol 7 (S283) ◽  
pp. 406-407
Author(s):  
Alexander F. Kholtygin ◽  
Igor' I. Nikiforov ◽  
Vitalii V. Akimkin
Keyword(s):  
Galactic Center ◽  
Planetary Nebulae ◽  
Distance Scale ◽  
Statistical Distance ◽  
Center Distance ◽  
Good Agreement

AbstractWe analyze the kinematics of disk planetary nebulae (PNe) to derive the formal Galactic center distance, R0, for three catalogues of PNe distances. Then we correct the catalogues' distance scales renormalizing the PNe distances by the ratios of formal R0 values to a best modern value of R0 =7.9 kpc. The created new catalogue of disk's PNe distances was found to be in a good agreement with distances by Stanghellini et al. (2008). Our catalogue of PNe distances was used to recalibrate the statistical distance scale for all Galactic PNe.

scholarly journals Properties of central stars of planetary nebulae with distances in Gaia DR2

2019 ◽  
Vol 630 ◽  
pp. A150 ◽  
Author(s):  
I. González-Santamaría ◽  
M. Manteiga ◽  
A. Manchado ◽  
A. Ulla ◽  
C. Dafonte
Keyword(s):  
Model Fitting ◽  
Planetary Nebulae ◽  
The United States ◽  
Evolutionary Status ◽  
The Galaxy ◽  
Spatially Distributed ◽  
Evolutionary Phase ◽  
Effective Temperatures ◽  
Central Stars ◽  
Hr Diagram

Context. We have compiled a catalogue of central stars of planetary nebulae (CSPN) with reliable distances and positions obtained from Gaia Data Release 2 (DR2) astrometry. Distances derived from parallaxes allow us to analyse the galactic distribution and estimate other parameters such as sizes, kinematical ages, bolometric magnitudes, and luminosities. Aims. Our objective is to analyse the information regarding distances together with other available literature data about photometric properties, nebular kinematics, and stellar effective temperatures to throw new light on this rapid and rather unknown evolutionary phase. We seek to understand how Gaia distances compare with other indirect methods commonly used and, in particular, with those derived from non-local thermodynamic equilibrium (non-LTE) models; how many planetary nebulae (PNe) populate the Galaxy; and how are they spatially distributed. We also aim to comprehend their intrinsic luminosities, range of physical sizes of the nebulae; how to derive the values for their kinematical ages; and whether those ages are compatible with those derived from evolutionary models. Methods. We considered all PNe listed in catalogues from different authors and in Hong Kong/AAO/Strasbourg/Hα (HASH) database. By X-matching their positions with Gaia DR2 astrometry we were able to identify 1571 objects in Gaia second archive, for which we assumed distances calculated upon a Bayesian statistical approach. From those objects, we selected a sample of PNe with good quality parallax measurements and distance derivations, we which refer to as our Golden Astrometry PNe sample (GAPN), and obtained literature values of their apparent sizes, radial and expansion velocities, visual magnitudes, interstellar reddening, and effective temperatures. Results. We found that the distances derived from DR2 parallaxes compare well with previous astrometric derivations of the United States Naval Observatory and Hubble Space Telescope, but that distances inferred from non-LTE model fitting are overestimated and need to be carefully reviewed. From literature apparent sizes, we calculated the physical radii for a subsample of nebulae that we used to derive the so-called kinematical ages, taking into account literature expansion velocities. Luminosities calculated with DR2 distances were combined with literature central stars Teff values in a Hertzsprung–Russell (HR) diagram to infer information on the evolutionary status of the nebulae. We compared their positions with updated evolutionary tracks finding a rather consistent picture. Stars with the smallest associated nebular radii are located in the flat luminosity region of the HR diagram, while those with the largest radii correspond to objects in a later stage, getting dimmer on their way to become a white dwarf. Finally, we commented on the completeness of our catalogue and calculated an approximate value for the total number of PNe in the Galaxy.

scholarly journals Properties and Evolution of White Dwarf Stars

1989 ◽  
Vol 131 ◽  
pp. 555-566
Author(s):  
Harry L. Shipman
Keyword(s):  
White Dwarf ◽  
Mean Value ◽  
Chemical Compositions ◽  
Evolutionary Status ◽  
Dwarf Stars ◽  
White Dwarf Stars ◽  
Abundance Patterns ◽  
Broad Variety ◽  
Ultimate Fate ◽  
Central Stars

This paper reviews the properties and evolutionary status of white dwarf stars, focusing most closely on those aspects which are likely to be of significance to understanding the ultimate fate of planetary nebulae and their central stars. White dwarf stars show a broad variety of chemical compositions. Broadly speaking, they are divided into the DA stars (with H-rich photospheres) and the non-DA stars (with He-rich photospheres), though there are a fairly large number of subtypes. The mass distribution of white dwarf stars is quite narrow, with a mean value near 0.6 and with extremes at 0.43 and 1.05. Different varieties of trace elements (such as C, N, 0, Si, Ca, and Mg) are quite common. I will review several recent proposals for explaining these abundance patterns. A particularly significant question is whether processes operating while the star cools as a white dwarf can account for their variety, or whether at least part of the white dwarf phenomenology is related to events which took place when the object was a planetary nebula or even earlier.

scholarly journals White Dwarfs and Planetary Central Stars

1989 ◽  
Vol 131 ◽  
pp. 545-554
Author(s):  
James Liebert
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
High Surface ◽  
Planetary Nebulae ◽  
Hydrogen Atmosphere ◽  
Surface Gravity ◽  
Surface Hydrogen ◽  
Central Stars

Studies of hot white dwarf samples constrain the properties and evolution of planetary nuclei and the nebulae. In particular, the white dwarf and planetary nebulae formation rates are compared. I discuss the overlap of the sequences of white dwarfs having hydrogen (DA) and helium-rich (DO) atmospheres with known central stars of high surface gravity. There is evidence that the hydrogen atmosphere nuclei have “thick” outer hydrogen layers (≳ 10−4 M⊙), but that DA white dwarfs may have surface hydrogen layers orders of magnitude thinner. Finally, a DA planetary nucleus is discussed (0950+139) which has undergone a late nebular ejection; this object may be demonstrating that a hydrogen layer can be lost even after the star has entered the white dwarf cooling sequence.

scholarly journals Planetary Nebulae and White Dwarfs

1978 ◽  
Vol 76 ◽  
pp. 353-353 ◽  
Author(s):  
V. Weidemann
Keyword(s):  
White Dwarfs ◽  
Birth Rate ◽  
Galactic Center ◽  
Planetary Nebulae ◽  
Radial Velocities ◽  
Distance Scale ◽  
Evolutionary Constraints ◽  
Birth Rates ◽  
Minimum Value ◽  
Central Stars

The present-day birth rate of planetary nebulae, 5·10−12 PN/pc3yr according to Cahn and Wyatt (1976), seems somewhat high compared to white dwarfs, for which a redetermination, including the statistics of Sion and Liebert (1977), yields 2·10−12 WD/pc3yr to within a factor of two. However, an increase of the distance scale for PN by a factor of 1.3 compared to Seaton (1968) - necessary in order to shift the extremum of PN radial velocities to the distance of the galactic center (9 kpc), and to increase the luminosities of the central stars from the position given by Pottasch et al. (1977) to a minimum value compatible with evolutionary constraints (Weidemann, 1977a) - brings birth rates of PN and WD into almost complete agreements.

Evolution of central stars of planetary nebulae towards the crystallizing white dwarf stage

1974 ◽  
Vol 27 (1) ◽  
pp. 217-225
Author(s):  
U. De Angelis ◽  
L. De Cesare ◽  
A. Forlani ◽  
G. Platania
Keyword(s):  
White Dwarf ◽  
Planetary Nebulae ◽  
Central Stars
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