scholarly journals The Evolution of the Planetary Nebulae in the Magellanic Clouds and the Galactic Bulge

1993 ◽  
Vol 155 ◽  
pp. 433-441 ◽  
Author(s):  
M.A. Dopita
Keyword(s):  
Strong Evidence ◽  
Central Star ◽  
Magellanic Clouds ◽  
Expansion Velocity ◽  
Type I ◽  
Chemical Abundances ◽  
Helium Burning ◽  
The Third ◽  
Self Consistent ◽  
Central Stars

From self-consistent photoionisation modelling of 147 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 core masses generally between 0.55 and 0.7 M⊙, and find strong evidence to support the model that they leave the AGB as helium-burning stars following the final shell flash. Type I PN have more massive cores, up to near the Schwartzschild limit, and show clear evidence for the Third dredge-up episode. From HST images, younger PN are very compact. The expansion velocity of the nebula is closely correlated with the position of the central star on the H-R Diagram.

scholarly journals Planetary nebulae in the Magellanic Clouds

1991 ◽  
Vol 148 ◽  
pp. 299-306 ◽  
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.

scholarly journals 3D photoionization models: the bipolar PN IC 4406

1997 ◽  
Vol 180 ◽  
pp. 231-231
Author(s):  
R. Gruenwald ◽  
S. M. Viegas ◽  
D. Broguière
Keyword(s):  
Planetary Nebula ◽  
Three Dimensional ◽  
Chemical Properties ◽  
Diffuse Radiation ◽  
Central Star ◽  
Type I ◽  
Chemical Abundances ◽  
Line Intensities ◽  
Physical Conditions ◽  
Self Consistent

A three-dimensional (3D) self-consistent photoionization code is developed in order to build more realistic models for asymmetrical and/or inhomogeneous photoionized nebulae. With these models the assumption of spherical or plane-parallel symmetry can be dropped and models with various geometries can be treated. The gaseous region is divided into numberous cubic cells, and the physical conditions in each cell are obtained taking into account the effect of the other cells in the optical depth and their contribution into the diffuse radiation. A model for IC 4406, which is a typical example of bipolar planetary nebula is presented. The model assumes a torus of dense material around the central star, as suggested in the literature. Its presence is confirmed by the model, in particular by the shape of the theoretical Hα + [NII] isophotal map. The chemical abundances required to explain the observed line intensities indicate that the chemical properties of this bipolar nebula are not characteristic of type I planetaries. A detailed paper will be published in Ap.J. (FAPESP, CNPq)

scholarly journals When nature tries to trick us

2018 ◽  
Vol 619 ◽  
pp. A84 ◽  
Author(s):  
Henri M. J. Boffin ◽  
David Jones ◽  
Roger Wesson ◽  
Yuri Beletsky ◽  
Brent Miszalski ◽  
...  
Keyword(s):  
Planetary Nebula ◽  
Binary Star ◽  
Central Star ◽  
Equal Mass ◽  
Type I ◽  
Eclipsing Binary ◽  
Common Envelope ◽  
Bright Object ◽  
F Stars ◽  
Central Stars

Bipolar planetary nebulae (PNe) are thought to result from binary star interactions and, indeed, tens of binary central stars of PNe have been found, in particular using photometric time-series that allow for the detection of post-common envelope systems. Using photometry at the NTT in La Silla we have studied the bright object close to the centre of PN M 3-2 and found it to be an eclipsing binary with an orbital period of 1.88 days. However, the components of the binary appear to be two A or F stars, of almost equal mass, and are therefore too cold to be the source of ionisation of the nebula. Using deep images of the central star obtained in good seeing conditions, we confirm a previous result that the central star is more likely much fainter, located 2″ away from the bright star. The eclipsing binary is thus a chance alignment on top of the planetary nebula. We also studied the nebular abundance and confirm it to be a Type I PN.

scholarly journals Twenty years of observations of PM 1-188: Its chemical abundances and extraordinary kinematics

2021 ◽  
Author(s):  
Miriam Peña ◽  
Liliana Hernández-Martínez ◽  
Francisco Ruiz-Escobedo
Keyword(s):  
Chemical Composition ◽  
Planetary Nebula ◽  
Central Star ◽  
Emission Lines ◽  
Type I ◽  
Chemical Abundances ◽  
Line Intensities ◽  
Physical Conditions ◽  
The Past ◽  
Spectrophotometric Data

Abstract The analysis of 20 years of spectrophotometric data of the double shell planetary nebula PM 1-188 is presented, aiming to determine the time evolution of the emission lines and the physical conditions of the nebula, as a consequence of the systematic fading of its [WC 10] central star whose brightness has declined by about 10 mag in the past 40 years. Our main results include that the [O iii], [O ii], [N ii] line intensities are increasing with time in the inner nebula as a consequence of an increase in electron temperature from 11 000 K in 2005 to more than 14 000 K in 2018, due to shocks. The intensity of the same lines are decreasing in the outer nebula, due to a decrease in temperature, from 13 000 K to 7000 K, in the same period. The chemical composition of the inner and outer shells was derived and they are similar. Both nebulae present subsolar O, S and Ar abundances, while they are He, N and Ne rich. For the outer nebula the values are 12+log He/H = 11.13 ± 0.05, 12+log O/H = 8.04 ± 0.04, 12+log N/H = 7.87 ± 0.06, 12+log S/H = 7.18 ± 0.10 and 12+log Ar = 5.33 ± 0.16. The O, S and Ar abundances are several times lower than the average values found in disc non-Type I PNe, and are reminiscent of some halo PNe. From high resolution spectra, an outflow in the N-S direction was found in the inner zone. Position-velocity diagrams show that the outflow expands at velocities in the −150 to 100 km s−1 range, and both shells have expansion velocities of about 40 km s−1.

scholarly journals Model Planetaries with rapidly evolving central stars: A case for FG Sge

1997 ◽  
Vol 180 ◽  
pp. 391-391
Author(s):  
K. Kifonidis ◽  
D. Schönberner
Keyword(s):  
White Dwarfs ◽  
Central Star ◽  
Frequency Of Occurrence ◽  
Helium Burning ◽  
Temporary Growth ◽  
Red Giant ◽  
Born Again ◽  
Thermal Pulses ◽  
Central Stars

Ever since the pioneering work of Schönberner (1979, A&A, 79, 108) and Iben (1984, ApJ, 277, 333) who showed that the evolution of post-AGB remnants might be affected by late thermal pulses of the helium-burning shell, resulting in a temporary growth of these objects to red giant dimensions, many attempts were made to explain a number of puzzling objects, among them the well-known variable central star FG Sge as well as the R CrB and PG 1159 stars, by this so-called “born-again AGB” scenario (Iben et al. 1983, ApJ, 264, 605; Iben & MacDonald 1995, in: White Dwarfs, Springer, p. 48). However, it is still not clear if the frequency of occurrence of such events is high enough as to be consistent with the number of born-again candidates. This is due to the very short evolutionary timescales during the pulse and the character of the post-pulse evolution which resembles the first post-AGB phase and makes it difficult for an observer to distinguish such objects from “normal” central stars.

scholarly journals IFU Spectroscopy of Southern Planetary Nebulae V: Low-Ionisation Structures

2017 ◽  
Vol 34 ◽  
Author(s):  
A. Ali ◽  
M. A. Dopita
Keyword(s):  
Emission Line ◽  
Planetary Nebulae ◽  
Central Star ◽  
Chemical Compositions ◽  
Physical Analysis ◽  
Type I ◽  
High Excitation ◽  
Chemical Abundances ◽  
Physical Conditions ◽  
Integral Field Spectroscopy

AbstractIn this fifth paper of the series, we examine the spectroscopy and morphology of four southern Galactic planetary nebulae Hen 2-141, NGC 5307, IC 2553, and PB 6 using new integral field spectroscopy data. The morphologies and ionisation structures of the sample are given as a set of emission-line maps. In addition, the physical conditions, chemical compositions, and kinematical characteristics of these objects are derived. The results show that PB 6 and Hen 2-141 are of very high excitation classes and IC 2553 and NGC 5307 are mid to high excitation objects. The elemental abundances reveal that PB 6 is of Type I, Hen 2-141 and IC 2553 are of Type IIa, and NGC 5307 is of Type IIb/III. The observations unveil the presence of well-defined low-ionisation structures or ‘knots’ in all objects. The diagnostic diagrams reveal that the excitation mechanism of these knots is probably by photoionisation of dense material by the nebular central stars. The physical analysis of six of these knots show no significant differences with their surrounding nebular gas, except their lower electron densities. In spite of the enhancement of the low-ionisation emission lines of these knots, their chemical abundances are nearly comparable to their surrounding nebulae, with the exception of perhaps slightly higher nitrogen abundances in the NGC 5307 knots. The integrated spectrum of IC 2553 reveals that nearly all key lines that have led researchers to characterise its central star as a weak-emission line star type are in fact of nebular origin.

scholarly journals Hubble Space Telescope observations of Planetary Nebulae in the Magellanic Clouds

1997 ◽  
Vol 180 ◽  
pp. 417-427
Author(s):  
M. A. Dopita ◽  
P. R. Wood ◽  
S. J. Meatheringham ◽  
E. Vassiliadis ◽  
R. C. Bohlin ◽  
...  
Keyword(s):  
Hubble Space Telescope ◽  
Uv Spectroscopy ◽  
Current Theory ◽  
Magellanic Clouds ◽  
Expansion Velocity ◽  
Abundance Patterns ◽  
Age Relation ◽  
Mass Dependent ◽  
First Time ◽  
Central Stars

We present the results of our major HST study of the evolution of PN in the Magellanic Clouds. This consists of imaging studies in [O III] and FOS UV spectroscopy. These data are then used in theoretical photoionisation models in conjuction with ground-based spectrophotometry, absolute flux and expansion velocity and density to derive self consistent diameters, ages, masses, and nebular abundances and to accurately place the central stars on the H-R Diagram. We find that observed sizes and ages can be reconciled with evolutionary theory provided that the He-burners outnumber the H-burners in the approximate ratio 2:1. For the LMC observed abundance patterns are qualitatively consistent with the (mass-dependent) operation of the various chemical dredge-up processes as predicted by theory. However, the observed dredge-up efficiencies do not agree with current theory. Finally, since core masses are determined with adequate precision, we are able to derive, for the first time, the metallicity age relation for of the LMC. We find that the base metallicity of the LMC rapidly increased ∼ 2 Gyr ago, consistent with the age of the burst of star formation inferred from field stars and clusters.

scholarly journals Abundances in Magellanic Cloud planetary nebulae

1991 ◽  
Vol 148 ◽  
pp. 291-298 ◽  
Author(s):  
M. J. Barlow
Keyword(s):  
Planetary Nebulae ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
Type I ◽  
The Third

The enhanced nitrogen abundances in planetary nebulae (PN) show the effects of CN-cycle processing at the time of the first dredge-up, while their very enhanced carbon abundances show the effects of the third dredge-up. The efficiency of both the first and third dredge-ups increases with decreasing initial metallicity. ON-cycle depletion of oxygen via the second dredge-up does not appear to have been significant in LMC Type I planetary nebulae (those with N/O > 0.5) – these nebulae have experienced the third dredge-up and envelope-burning, giving enhanced C+N abundances. The LMC Type I PN show enhanced Ne/O ratios. Enrichment rates in nitrogen and carbon by PN are estimated for the ISM s of the Magellanic Clouds.

scholarly journals The Magellanic Clouds and Planetary Nebulae

1984 ◽  
Vol 108 ◽  
pp. 363-374
Author(s):  
Manuel Peimbert
Keyword(s):  
Emission Line ◽  
Chemical Evolution ◽  
Stellar Evolution ◽  
Central Star ◽  
Magellanic Clouds ◽  
Chemical Compositions ◽  
Intermediate Mass ◽  
Chemical Abundances ◽  
Line Intensities ◽  
Intermediate Mass Stars

A review of the statistics, emission line intensities, central star fluxes, radial velocities and chemical compositions of PN in the MC is given. From these data a discussion is made of: a) the distance scale, b) the envelope mass, c) the comparison between the observed chemical abundances and those predicted from stellar evolution models and, d) the effect that intermediate mass stars have on the chemical evolution of the MC and our galaxy.

scholarly journals Distances of the Central Stars and their Position in the HR Diagram

1983 ◽  
Vol 103 ◽  
pp. 391-409 ◽  
Author(s):  
S.R. Pottasch
Keyword(s):  
Galactic Center ◽  
Planetary Nebulae ◽  
Central Star ◽  
Magellanic Clouds ◽  
Constant Mass ◽  
Theoretical Predictions ◽  
Statistical Distance ◽  
Central Stars ◽  
Hr Diagram

Determination of the distances to individual planetary nebulae are discussed. Especially those methods which are independent of assumed nebular properties (mass, absolute flux, etc.) are assembled and discussed. In this way, reasonable approximations to the distance can be obtained for about 50 planetary nebulae. The accuracy of the distances is tested by comparing nebular properties derived from these distances with the properties of nebulae at the galactic center or in the Magellanic clouds. A comparison is also made with the statistical distance determinations; the conclusion is that the assumption of constant mass often leads to an overestimate of the distance, while the assumption of constant Hβ flux leads to distances having individual uncertainties of up to a factor of 3.The central star temperature determination is summarized. Individual central stars are placed on the HR diagram and compared with theoretical predictions. Deductions concerning the evolution which can be made from the observations are discussed.

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