scholarly journals Appendix A: A Catalog of Hydrogen-Deficient Stars

1985 ◽  
Vol 87 ◽  
pp. 498-506
Author(s):  
J.S. Drilling ◽  
P.W. Hill
Keyword(s):  
Data Base ◽  
White Dwarfs ◽  
Planetary Nebulae ◽  
Basic Data ◽  
Complete List ◽  
Central Stars

The following four tables were originally presented as part of the paper entitled ‘Basic Data on Hydrogen-Deficient Stars’ by J. S. Drilling, which appears earlier in this volume. A number of corrections and additions have been made by the participants, mostly by P. W. Hill using the SIMBAD data base. A much improved version of the catalog therefore follows. Helium-rich central stars of planetary nebulae, helium-rich white dwarfs, and Wolf-Rayet stars are not included. A complete list of helium-rich central stars is given by Mendez et al. elsewhere in this volume.

scholarly journals Central Stars of Old Planetary Nebulae

1993 ◽  
Vol 155 ◽  
pp. 88-88 ◽  
Author(s):  
R. Napiwotzki
Keyword(s):  
White Dwarfs ◽  
Planetary Nebulae ◽  
Complete List ◽  
Close Binaries ◽  
High Gravity ◽  
Hybrid Type ◽  
Central Stars

During a program for the observation of central stars of old planetary nebulae 29 stars are classified until now. Most of them (22) are belonging to the hydrogen-rich sequence and resemble either high-gravity sdO stars or white dwarfs (14 DAOs, 3 DAs). 3 are hydrogen-deficient PG 1159 stars, and also 3 are hybrid type stars Further 3 CPN are close binaries, whose evolution has been certainly influenced by this circumstance. A complete list of so far observed objects is given in Napiwotzki (1992).

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 A High Resolution Far-UV Spectral Atlas of CSPNs and Hot White Dwarfs

1993 ◽  
Vol 155 ◽  
pp. 91-91
Author(s):  
R.W. Tweedy
Keyword(s):  
High Resolution ◽  
White Dwarfs ◽  
Planetary Nebulae ◽  
Central Star ◽  
Evolutionary Sequence ◽  
Spectroscopic Analyses ◽  
Spectroscopic Information ◽  
The University ◽  
Phd Thesis ◽  
Central Stars

A high-resolution IUE spectral atlas of central stars of planetary nebulae and hot white dwarfs has been produced (part of Tweedy, 1991, PhD thesis from the University of Leicester, UK), and examples from it are shown here. It has been sorted into an approximate evolutionary sequence, based on published spectroscopic analyses, from the cool 28,000K young central star He 2–138, through the hot objects like NGC 7293 and NGC 246 at 90,000K and 130,000K respectively, down to 40,000K DA white dwarfs like GD 2, which is the chosen cutoff for this selection. Copies of a revised version of this atlas, which will include more recent spectroscopic information and also white dwarfs down to 35,000K – to include the Si III object GD 394 – will be sent to anyone who requests one.

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.

scholarly journals Implications of White-Dwarf Crystallization for the Chemical Composition of the Planetary Nuclei

1968 ◽  
Vol 34 ◽  
pp. 425-427
Author(s):  
H.M. Van Horn
Keyword(s):  
Chemical Composition ◽  
White Dwarf ◽  
White Dwarfs ◽  
Planetary Nebulae ◽  
Considerable Importance ◽  
Central Stars

It now seems to be reasonably well-established that the central stars of planetary nebulae evolve directly into white dwarfs. Evidently a knowledge of the chemical composition of the white dwarfs would therefore be of considerable importance in helping to identify the point in the evolution at which the mechanism responsible for expulsion of the nebular shell becomes operative. For this reason I would like to present some evidence which provides a direct suggestion for the internal composition of some of the white dwarfs and to examine briefly the implications of this suggestion for the relation between the planetary nuclei and the white dwarfs.

scholarly journals Ages of evolved low mass stars: Central stars of planetary nebulae and white dwarfs

2013 ◽  
Vol 43 ◽  
pp. 05004
Author(s):  
W.J. Maciel ◽  
T.S. Rodrigues ◽  
R.D.D. Costa
Keyword(s):  
White Dwarfs ◽  
Planetary Nebulae ◽  
Low Mass Stars ◽  
Low Mass ◽  
Central Stars

scholarly journals Mass Distribution and Birth Rate of Central Stars of Planetary Nebulae: Comparison with White Dwarfs, and Influence of Selection Effects

1989 ◽  
Vol 131 ◽  
pp. 540-540
Author(s):  
V. Weidemann
Keyword(s):  
Recent Work ◽  
Mass Distribution ◽  
White Dwarfs ◽  
Birth Rate ◽  
Planetary Nebulae ◽  
Magellanic Cloud ◽  
Selection Effects ◽  
The One ◽  
Central Stars

The mass distribution of central stars (CPN) as derived by the Schönberner method (1981) M⊙ vs. age, v(exp) = const, for an enlarged local ensemble, as presented at the London Symposium, 1983, appears to be much narrower and more strongly peaked towards smaller masses than the one recently derived by Heap and Augensen (1987) (HA) using the same method, but IUE data and M⊙ (λ 1300) vs. age, corrected for individual v(exp). Whereas according to Schönberner 65% of all CPN have M < 0.64 M⊙, HA find only 44% below the same limit. We demonstrate that this discrepancy is entirely due to the fact, that HA use Daub and 0.9 × Cahn/Kaler distances, whereas Schönberner used 1.3 × CK. We list a number of arguments which favor the larger distances, especially the recent work by Méndez et al. (preprint, 1987) (Teff/g determinations) and investigations of Magellanic Cloud PN by Aller et al. (1987), Wood et al. (1987) and Barlow (1987) which all indicate a scale ≥. 1.4 × CK. If one uses Barlow's recalibration formula for optically thick PN, the distances for those - which mainly contribute to the massive CPN in the HA analysis - are increased so much as to remove most of them from the local ensemble. We thus obtain for the revised IUE ensemble 84% CPN with M < 0.64 M⊙, in better agreement with results for white dwarfs (70%) (cf. Weidemann, 1987).

The mass distribution of white dwarfs and central stars of planetary nebulae

1988 ◽  
Vol 8 (2-3) ◽  
pp. 333-335
Author(s):  
P.R. Amnuel ◽  
O.H. Guseinov ◽  
H.I. Novruzova ◽  
Yu.S. Rustamov
Keyword(s):  
Mass Distribution ◽  
White Dwarfs ◽  
Planetary Nebulae ◽  
Central Stars
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