scholarly journals Observed Evolution of the Nebulae and Central Stars

2003 ◽  
Vol 209 ◽  
pp. 159-166 ◽  
Author(s):  
Romuald Tylenda
Keyword(s):  
Observational Studies ◽  
Planetary Nebulae ◽  
Time Dependent ◽  
Central Stars

Several points involved in observational studies of evolution of planetary nebulae and their central stars are discussed. It concerns observed masses of nebulae and central stars, nature of H-deficient central stars, role of time-dependent ionization in the nebular haloes, and a recent discovery of strong enrichements in some planetary nebulae.

scholarly journals The role of heat conduction to the formation of [WC]-type planetary nebulae

2011 ◽  
Vol 7 (S283) ◽  
pp. 494-495
Author(s):  
Christer Sandin ◽  
Matthias Steffen ◽  
Ralf Jacob ◽  
Detlef Schönberner ◽  
Ute Rühling ◽  
...  
Keyword(s):  
Heat Conduction ◽  
Chemical Composition ◽  
Physical Properties ◽  
Planetary Nebulae ◽  
Time Dependent ◽  
Diffuse Emission ◽  
Hydrodynamic Models ◽  
X Ray ◽  
Central Stars

AbstractX-ray observations of young Planetary Nebulæ (PNe) have revealed diffuse emission in extended regions around both H-rich and H-deficient central stars. In order to also reproduce physical properties of H-deficient objects, we have, at first, extended our time-dependent radiation-hydrodynamic models with heat conduction for such conditions. Here we present some of the important physical concepts, which determine how and when a hot wind-blown bubble forms. In this study we have had to consider the, largely unknown, evolution of the CSPN, the slow (AGB) wind, the fast hot-CSPN wind, and the chemical composition. The main conclusion of our work is that heat conduction is needed to explain X-ray properties of wind-blown bubbles also in H-deficient objects.

scholarly journals The Role of Binarity in Wolf-Rayet Central Stars of Planetary Nebulae

2015 ◽  
Vol 71-72 ◽  
pp. 117-120 ◽  
Author(s):  
B. Miszalski ◽  
R. Manick ◽  
V. McBride
Keyword(s):  
Planetary Nebulae ◽  
Central Stars

scholarly journals Planetary Nebulae with Massive Nuclei

1983 ◽  
Vol 103 ◽  
pp. 230-230
Author(s):  
R. Tylenda
Keyword(s):  
Thermal Structure ◽  
Planetary Nebulae ◽  
General Rule ◽  
Central Star ◽  
Time Dependent ◽  
Equilibrium Conditions ◽  
Ngc 7027 ◽  
Different Temperatures ◽  
Far From Equilibrium ◽  
Central Stars

Massive central stars (M > 1 Mo) of planetary nebulae burn nuclear fuel on a time scale of hundreds or tens of years which is shorter than the recombination time in a typical planetary nebula. Consequently the ionization and thermal structure of a nebula with such a nucleus is expected to be far from equilibrium conditions. The greatest chance of observing such a nebula is when the central star cools down to the white dwarf region. Time-dependent photoionization models suggest the following non-equilibrium effects to be expected at this stage. Firstly, the nebula shows a double shell structure, i.e. a bright, inner ring is surrounded by a faint, extended halo best seen in the HI lines and infrared lines from low-ionization species, such as (Ne II) 12.8 μ. Secondly, the low-excitation emission ((O II), (Ne II), (S III)) is enhanced relative to the high-excitation ((O III), (Ne III), (S III)). Thirdly, different modifications of the Zanstra method result in significantly different temperatures for the central star with a general rule that THI > THeII > THeII/HI The He II Zanstra method gives the most reliable result. Fourthly, the electron temperature derived from the (O III) lines is appreciably higher than that obtained from the (N II) lines. It is suggested that NGC 7027 and NGC 2440 possess massive central stars and that the above time-dependent effects are currently observed in these nebulae.

scholarly journals Binary Central Stars of Planetary Nebulae

Galaxies ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 28 ◽  
Author(s):  
David Jones
Keyword(s):  
Planetary Nebulae ◽  
Current Understanding ◽  
Intermediate Mass ◽  
Single Star ◽  
Intermediate Mass Stars ◽  
Binary Evolution ◽  
Central Stars

It is now clear that a vast majority of intermediate-mass stars have stellar and/or sub-stellar companions, therefore it is no longer appropriate to consider planetary nebulae as a single-star phenomenon, although some single, isolated stars may well lead to planetary nebulae. As such, while understanding binary evolution is critical for furthering our knowledge of planetary nebulae, the converse is also true: planetary nebulae can be valuable tools with which to probe binary evolution. In this brief review, I attempt to summarise some of our current understanding with regards to the role of binarity in the formation of planetary nebulae, and the areas in which continued study of planetary nebulae may have wider ramifications for our grasp on the fundaments of binary evolution.

scholarly journals Observational Studies of Close Binary Central Stars of Planetary Nebulae: HFG 1 and a 63

1993 ◽  
Vol 155 ◽  
pp. 393-393
Author(s):  
Hakim Lufthfi Malasan ◽  
Atsuma Yamasaki
Keyword(s):  
Observational Studies ◽  
Planetary Nebulae ◽  
Close Binary ◽  
Photometric Observations ◽  
Central Stars

We have made spectroscopic and photometric observations of two close binary central stars of planetary nebulae HFG 1 (V 664 Cas) and A 63 (UU Sge), using the UH 2.2–m telescope (Mauna Kea Observatory) and the NAO 1.9–m and 0.9–m telescopes (Okayma Astrophysical Observatory).

scholarly journals Analysis of hydrogen rich PG 1159 central stars of Planetary Nebulae

1997 ◽  
Vol 180 ◽  
pp. 103-103 ◽  
Author(s):  
S. Dreizler ◽  
K. Werner ◽  
U. Heber
Keyword(s):  
Detection Limit ◽  
Mass Loss ◽  
Small Group ◽  
Qualitative Agreement ◽  
Planetary Nebulae ◽  
Time Dependent ◽  
Spectral Analyses ◽  
Abundance Pattern ◽  
Incomplete Removal ◽  
Central Stars

The PG 1159 stars represent the hottest stage of post-AGB evolution. Quantitative spectral analyses of most known PG 1159 stars have been carried out by us from optical, UV and EUV observations (see Dreizler et al 1995 for a review). It has been shown that these stars have atmospheres dominated by C and He with a significant admixture of O. These abundances reveal the inter–shell matter of a former AGB star. The four stars, HS 2324+3944, NGC 7094, Abell 43, and Sh 2-68, define a small group of peculiar PG 1159 stars (termed hybrid PG 1159). Unlike all other PG 1159 stars hydrogen is detected in their spectra. Three of them are CSPNe. Our Non-LTE analyses (Dreizler et al 1995; Dreizler et al 1996) show that these stars have typical PG 1159 Teff, log g as well as C and He abundances (Table 1). In contrast, the O abundance is lower than in PG 1159 stars. N is probably present but near the detection limit of the currently available spectra. Hybrid PG 1159 stars tend to have lower masses/luminosities than ordinary PG 1159 stars. A reduced mass-loss in their post-AGB evolution might be responsible for the incomplete removal of the H rich envelope. However, peeling of a post-AGB star alone can not produce the observed abundance pattern. In addition, mixing is required. A first evolution calculation with time dependent mixing of Iben & MacDonald (1995) shows some qualitative agreement in the abundance pattern like the C/He ratio it is, however, not able to explain the overall abundances.

scholarly journals Planetary nebulae seen with TESS: Discovery of new binary central star candidates from Cycle 1

2020 ◽  
Vol 635 ◽  
pp. A128 ◽  
Author(s):  
A. Aller ◽  
J. Lillo-Box ◽  
D. Jones ◽  
L. F. Miranda ◽  
S. Barceló Forteza
Keyword(s):  
Main Sequence ◽  
Planetary Nebulae ◽  
Central Star ◽  
Statistical Validation ◽  
Low Mass ◽  
The Common ◽  
Binary Evolution ◽  
The Individual ◽  
Central Stars

Context. It has become clear in recent years that binarity plays a crucial role in many aspects of planetary nebulae (PNe), particularly with regard to the striking morphologies they exhibit. To date, there are nearly 60 known binary central stars of PNe (bCSPNe). However, both theory and observation indicate that this figure represents only the tip of the iceberg, with the Galactic PN population hosting orders of magnitude more stars. Aims. We are involved in a search for new bCSPNe with the aim of enhancing the statistical validation of the key role of binarity in the formation and shaping of PNe. New discoveries of bCSPNe and their characterization carry important implications not only for understanding PN evolution, but also for studying binary evolution and the common-envelope phase, which is still poorly understood. Methods. We used data from the TESS satellite to search for variability in the eight CSPNe that belong to the two-minute cadence of preselected targets in Cycle 1, with their available pipeline-extracted light curves. We identified strong periodicities and analysed them in the context of the binary scenario. Results. All the CSPNe but one (Abell 15) show clear signs of periodic variability in TESS. The cause of this variability can be attributed to different effects, some of them requiring the presence of a companion star. We find simple sinusoidal modulations in several of the systems, compatible with irradiation effects. In addition, two of the central stars (PG 1034+001 and NGC 5189) also show photometric variations due to ellipsoidal variations and other signs of variability that are probably caused by star spots or relativistic Doppler-beaming. The case of the well-studied Helix Nebula is of particular interest; here we constructed a series of binary models to explain the modulations we see in the light curve. We find that the variability constrains the possible companion to be very low-mass main-sequence star or sub-stellar object. We also identify, in substantial detail, the individual pulsation frequencies of NGC 246.

scholarly journals Time-Dependent Effects in Planetary Nebulae Caused by Thermal Pulses in Central Stars

1978 ◽  
Vol 76 ◽  
pp. 211-211
Author(s):  
R. Tylenda
Keyword(s):  
Time Scale ◽  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Theoretical Models ◽  
Emission Lines ◽  
Time Dependent ◽  
Stationary Model ◽  
Ionization Structure ◽  
Thermal Pulses ◽  
Central Stars

Nuclei of planetary nebulae are suspected to go through thermal pulses. A time scale of such pulses is of the order of 10–103 years and so it is comparable with the time of recombination in a typical planetary nebula. Theoretical models have been constructed to study evolution of ionization structure of nebulae in which the spectrum of ionizing radiation varies with time. Resulting intensities of emission lines are compared with those produced by stationary model nebulae.

scholarly journals Planetary Nebula Evolution Traced by Distance-Independent Parameters

1993 ◽  
Vol 155 ◽  
pp. 480-480
Author(s):  
C.Y. Zhang ◽  
S. Kwok
Keyword(s):  
Physical Properties ◽  
Mass Distribution ◽  
Planetary Nebula ◽  
Strong Support ◽  
Planetary Nebulae ◽  
Central Star ◽  
Evolution Model ◽  
The Core ◽  
Independent Parameters ◽  
Central Stars

Making use of the results from recent infrared and radio surveys of planetary nebulae, we have selected 431 nebulae to form a sample where a number of distance-independent parameters (e.g., Tb, Td, I60μm and IRE) can be constructed. In addition, we also made use of other distance-independent parameters ne and T∗ where recent measurements are available. We have investigated the relationships among these parameters in the context of a coupled evolution model of the nebula and the central star. We find that most of the observed data in fact lie within the area covered by the model tracks, therefore lending strong support to the correctness of the model. Most interestingly, we find that the evolutionary tracks for nebulae with central stars of different core masses can be separated in a Tb-T∗ plane. This implies that the core masses and ages of the central stars can be determined completely independent of distance assumptions. The core masses and ages have been obtained for 302 central stars with previously determined central-star temperatures. We find that the mass distribution of the central stars strongly peaks at 0.6 M⊙, with 66% of the sample having masses <0.64 MM⊙. The luminosities of the central stars are then derived from their positions in the HR diagram according to their core masses and central star temperatures. If this method of mass (and luminosity) determination turns out to be accurate, we can bypass the extremely unreliable estimates for distances, and will be able to derive other physical properties of planetary nebulae.

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