Analysis of chemical abundances in planetary nebulae with [WC] central stars

AbstractThe discrepancy between abundances computed using optical recombination lines (ORLs) and collisionally excited lines (CELs) is a major, unresolved problem with significant implications for the determination of chemical abundances throughout the Universe. In planetary nebulae (PNe), the most common explanation for the discrepancy is that two different gas phases coexist: a hot component with standard metallicity, and a much colder plasma enhanced in heavy elements. This dual nature is not predicted by mass loss theories, and direct observational support for it is still weak. In this work, we present our recent findings that demonstrate that the largest abundance discrepancies are associated with close binary central stars. OSIRIS-GTC tunable filter imaging of the faint O ii ORLs and MUSE-VLT deep 2D spectrophotometry confirm that O ii ORL emission is more centrally concentrated than that of [Oiii] CELs and, therefore, that the abundance discrepancy may be closely linked to binary evolution.

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Analysis of chemical abundances in planetary nebulae with [WC] central stars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201118217 ◽

2012 ◽

Vol 538 ◽

pp. A54 ◽

Cited By ~ 31

Author(s):

J. García-Rojas ◽

M. Peña ◽

C. Morisset ◽

A. Mesa-Delgado ◽

M. T. Ruiz

Keyword(s):

Planetary Nebulae ◽

Chemical Abundances ◽

Central Stars

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Planetary nebulae in the Magellanic Clouds

Symposium - International Astronomical Union ◽

10.1017/s0074180900200624 ◽

1991 ◽

Vol 148 ◽

pp. 299-306 ◽

Cited By ~ 1

Author(s):

M. A. Dopita

Keyword(s):

Planetary Nebulae ◽

Central Star ◽

Magellanic Cloud ◽

Expansion Velocity ◽

H Ii Regions ◽

Type I ◽

Chemical Abundances ◽

Processed Material ◽

Density Radius ◽

Central Stars

We present a simple two-wind model for the evolution of the Magellanic Cloud planetary nebulae (PN) which reproduces the observed density / radius / ionised mass relationships, and serves to define the geometrical relationship between the ionised nebula and the star. From self-consistent photoionisation modelling of 78 Magellanic Cloud PN, we have constructed the H-R Diagram for the central stars, and have derived both the chemical abundances and the nebular parameters. We find that the central stars have masses generally between 0.55 and 0.7 M⊙. Type I PN have more massive precursors, and show clear evidence for the Third dredge-up episode and for the dredge-up of ON processed material. The expansion velocity of the nebula is closely correlated with the position of the central star on the H-R Diagram, proving that the nebula undergoes continuous acceleration. Excluding Type I PN, the mean abundances derived for the LMC and the SMC agree with those derived from H II regions and evolved, radiative SNR.

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Chemical Abundances of the Planetary Nebulae NGC 2392 and NGC 3242

International Astronomical Union Colloquium ◽

10.1017/s0252921100079240 ◽

2001 ◽

Vol 183 ◽

pp. 339-340

Author(s):

C.H. Wu ◽

J.Z. Li ◽

Z.W. Chang ◽

C.Y. Lin ◽

J.Y. Hu ◽

...

Keyword(s):

Planetary Nebulae ◽

Astronomical Observatory ◽

Chemical Compositions ◽

Chemical Abundances ◽

Low Mass Stars ◽

Preliminary Results ◽

Mass Distributions ◽

Low Mass ◽

Red Giant ◽

Central Stars

AbstractPlanetary nebulae represent the end product of the evolution of low mass stars with M < 8M⊙. The central stars have masses between 0.55 and 0.85M⊙. This means a large amount of material must have been distributed in the interiors of the PNe. The observed variations of the chemical compositions and mass distributions therefore carry important information about the nature of the associated AGB superwinds and Red Giant outflows. (Kwok et al, 1978) A program for comprehensive multiwavelength study of PNe has been initiated at NCU. One recent study has to do with the spectrographic observations of the planetary nebulae NGC 2392 and NGC 3242 using the 2.16 m telescope of the Beijing Astronomical Observatory. Some preliminary results are presented here.

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Planetary Nebula Evolution Traced by Distance-Independent Parameters

Symposium - International Astronomical Union ◽

10.1017/s0074180900172134 ◽

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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Chemical Enrichment and Central Star Properties

Symposium - International Astronomical Union ◽

10.1017/s0074180900172468 ◽

1993 ◽

Vol 155 ◽

pp. 572-572

Author(s):

C.Y. Zhang

Keyword(s):

Planetary Nebulae ◽

Central Star ◽

Agb Stars ◽

Physical Processes ◽

Chemical Abundances ◽

Core Mass ◽

Chemical Enrichment ◽

The Core ◽

Stellar Temperature ◽

Independent Parameters

We have selected a sample of planetary nebulae, for which the core masses are determined using distance-independent parameters (Zhang and Kwok 1992). The chemical abundances of He, N, O, and C are taken from the literature for them. Relationships of the ratios of He/H, N/O, and C/O with various stellar parameters of planetary nebulae (PN), such as the core mass, the mass of the core plus the ionized nebular gas, the stellar age and temperature, are examined. It is found that the N/O increases with increasing mass, while the C/O first increases and then decreases with the core mass. No strong correlation seems to exist between the He/H and the core mass. A correlation of the N/O and He/H with the stellar temperature exists. The current dredge-up theory for the progenitor AGB stars cannot satisfactorily account for these patterns of chemical enrichment in PN. Furthermore, the correlations of the N/O and He/H with the stellar age and temperature indicate that besides the dredge-ups in the RG and AGB stages, physical processes that happen in the planetary nebula stage may also play a role in forming the observed patterns of chemical enrichment in the planetary nebulae.

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