scholarly journals The cooling-down central star of the planetary nebula SwSt 1: a late thermal pulse in a massive post-AGB star?

2020 ◽  
Vol 498 (1) ◽  
pp. 1205-1220
Author(s):  
Marcin Hajduk ◽  
Helge Todt ◽  
Wolf-Rainer Hamann ◽  
Karolina Borek ◽  
Peter A M van Hoof ◽  
...  
Keyword(s):  
Planetary Nebula ◽  
Central Star ◽  
Line Flux ◽  
Stellar Spectrum ◽  
Thermal Pulse ◽  
Ultraviolet Spectra ◽  
Stellar Temperature ◽  
Released Energy ◽  
Red Giant ◽  
Born Again

ABSTRACT SwSt 1 (PN G001.5-06.7) is a bright and compact planetary nebula containing a late [WC]-type central star. Previous studies suggested that the nebular and stellar lines are slowly changing with time. We studied new and archival optical and ultraviolet spectra of the object. The [O iii] 4959 and 5007 Å to H β line flux ratios decreased between about 1976 and 1997/2015. The stellar spectrum also shows changes between these epochs. We modelled the stellar and nebular spectra observed at different epochs. The analyses indicate a drop of the stellar temperature from about 42 kK to 40.5 kK between 1976 and 1993. We do not detect significant changes between 1993 and 2015. The observations show that the star performed a loop in the H–R diagram. This is possible when a shell source is activated during its post-AGB evolution. We infer that a late thermal pulse (LTP) experienced by a massive post-AGB star can explain the evolution of the central star. Such a star does not expand significantly as the result of the LTP and does not became a born-again red giant. However, the released energy can remove the tiny H envelope of the star.

scholarly journals Ablation and Wind Mass-Loading in the Born-Again Planetary Nebula A 30

2011 ◽  
Vol 7 (S283) ◽  
pp. 378-379
Author(s):  
Martín A. Guerrero ◽  
You-Hua Chu ◽  
Wolf-Rainer Hamann ◽  
Lidia Oskinova ◽  
Detlef Schönberner ◽  
...  
Keyword(s):  
Stellar Wind ◽  
Planetary Nebula ◽  
Central Star ◽  
Mass Loading ◽  
Diffuse Emission ◽  
X Ray ◽  
Thermal Pulse ◽  
Born Again

AbstractWe present XMM-Newton and Chandra observations of the born-again planetary nebula A 30. These X-ray observations reveal a bright unresolved source at the position of the central star whose X-ray luminosity exceeds by far the model expectations for photospheric emission and for shocks within the stellar wind. We suggest that a “born-again hot bubble” may be responsible for this X-ray emission. Diffuse X-ray emission associated with the petal-like features and one of the H-poor knots seen in the optical is also found. The weakened emission of carbon lines in the spectrum of the diffuse emission can be interpreted as the dilution of stellar wind by mass-loading or as the detection of material ejected during a very late thermal pulse.

scholarly journals New models for the rapid evolution of the central star of the Stingray Nebula

2021 ◽  
Author(s):  
T M Lawlor
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Planetary Nebula ◽  
Rapid Evolution ◽  
Central Star ◽  
Asymptotic Giant Branch ◽  
Initial Mass ◽  
Thermal Pulse ◽  
The Past ◽  
New Models

Abstract We present stellar evolution calculations from the Asymptotic Giant Branch (AGB) to the Planetary Nebula (PN) phase for models of initial mass 1.2 M⊙ and 2.0 M⊙ that experience a Late Thermal Pulse (LTP), a helium shell flash that occurs following the AGB and causes a rapid looping evolution between the AGB and PN phase. We use these models to make comparisons to the central star of the Stingray Nebula, V839 Ara (SAO 244567). The central star has been observed to be rapidly evolving (heating) over the last 50 to 60 years and rapidly dimming over the past 20–30 years. It has been reported to belong to the youngest known planetary nebula, now rapidly fading in brightness. In this paper we show that the observed timescales, sudden dimming, and increasing Log(g), can all be explained by LTP models of a specific variety. We provide a possible explanation for the nebular ionization, the 1980’s sudden mass loss episode, the sudden decline in mass loss, and the nebular recombination and fading.

scholarly journals Sakurai's object: spectroscopic monitoring and nebula observations

1997 ◽  
Vol 180 ◽  
pp. 392-392
Author(s):  
D. L. Pollacco ◽  
N.A. Walton ◽  
H. G. Schwarz ◽  
S. A. Bell
Keyword(s):  
Planetary Nebula ◽  
Theoretical Models ◽  
Central Star ◽  
Thermal Pulse ◽  
Spectroscopic Monitoring ◽  
Transient Events ◽  
Modern Instrumentation

Sakurai's object is thought to be undergoing a final thermal pulse or shell flash. It is the first example of this type of object to be studied using modern instrumentation and will be useful and unique for the time being for placing theoretical models of these transient events on a firm observational footing. The only other definite candidate is V605 Aql – now the WC central star of the planetary nebula Abell 58 – which is thought to have undergone a final thermal pulse around 1918.

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 A Speculation into the Origin of Neutral Globules in Planetary Nebulae: Could the Helix’s Comets Really be Comets?

1995 ◽  
Vol 12 (2) ◽  
pp. 170-173
Author(s):  
Grant Gussie
Keyword(s):  
Solar System ◽  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Central Star ◽  
Oort Cloud ◽  
Asymptotic Giant Branch ◽  
Neutral Gas ◽  
Red Giant ◽  
The Masses

AbstractA novel explanation for the origin of the cometary globules within NGC 7293 (the ‘Helix’ planetary nebula) is examined, namely that these globules originate as massive cometary bodies at large astrocentric radii. The masses of such hypothetical cometary bodies would have to be several orders of magnitude larger than those of any such bodies observed in our solar system in order to supply the observed mass of neutral gas. It is, however, shown that comets at ‘outer Oort cloud’ distances are likely to survive past the red giant and asymptotic giant branch evolutionary phases of the central star, allowing them to survive until the formation of the planetary nebula. Some observational tests of this hypothesis are proposed.

scholarly journals The very fast evolution of Sakurai's object

2016 ◽  
Vol 12 (S323) ◽  
pp. 380-381 ◽  
Author(s):  
G. C. Van de Steene ◽  
P. A. M. van Hoof ◽  
S. Kimeswenger ◽  
A. A. Zijlstra ◽  
A. Avison ◽  
...  
Keyword(s):  
High Resolution ◽  
Emission Line ◽  
Planetary Nebula ◽  
Temporal Evolution ◽  
Optical Emission ◽  
Central Star ◽  
Evolutionary Models ◽  
Thermal Pulse ◽  
Emission Line Spectrum ◽  
Fast Evolution

AbstractV4334 Sgr (a.k.a. Sakurai's object) is the central star of an old planetary nebula that underwent a very late thermal pulse a few years before its discovery in 1996. We have been monitoring the evolution of the optical emission line spectrum since 2001. The goal is to improve the evolutionary models by constraining them with the temporal evolution of the central star temperature. In addition the high resolution spectral observations obtained by X-shooter and ALMA show the temporal evolution of the different morphological components.

scholarly journals The post-common-envelope binary central star of the planetary nebula PN G283.7−05.1

2020 ◽  
Vol 642 ◽  
pp. A108 ◽  
Author(s):  
D. Jones ◽  
H. M. J. Boffin ◽  
J. Hibbert ◽  
T. Steinmetz ◽  
R. Wesson ◽  
...  
Keyword(s):  
Planetary Nebula ◽  
Main Sequence ◽  
Planetary Nebulae ◽  
Central Star ◽  
Radial Velocity Curve ◽  
Common Envelope ◽  
Low Mass ◽  
Red Giant ◽  
Model Temperature ◽  
Temperature Surface

We present the discovery and characterisation of the post-common-envelope central star system in the planetary nebula PN G283.7−05.1. Deep images taken as part of the POPIPlaN survey indicate that the nebula may possess a bipolar morphology similar to other post-common-envelope planetary nebulae. Simultaneous light and radial velocity curve modelling reveals that the newly discovered binary system comprises a highly irradiated M-type main-sequence star in a 5.9-hour orbit with a hot pre-white dwarf. The nebular progenitor is found to have a particularly low mass of around 0.4 M⊙, making PN G283.7−05.1 one of only a handful of candidate planetary nebulae that is the product of a common-envelope event while still on the red giant branch. In addition to its low mass, the model temperature, surface gravity, and luminosity are all found to be consistent with the observed stellar and nebular spectra through comparison with model atmospheres and photoionisation modelling. However, the high temperature (Teff ∼ 95 kK) and high luminosity of the central star of the nebula are not consistent with post-RGB evolutionary tracks.

scholarly journals Hidden IR structures in NGC 40: signpost of an ancient born-again event

2019 ◽  
Vol 485 (3) ◽  
pp. 3360-3369 ◽  
Author(s):  
J A Toalá ◽  
G Ramos-Larios ◽  
M A Guerrero ◽  
H Todt
Keyword(s):  
Spectral Analysis ◽  
Spatial Distribution ◽  
Aromatic Hydrocarbons ◽  
Planetary Nebula ◽  
Central Star ◽  
Distribution Analysis ◽  
High Excitation ◽  
Polycyclic Aromatic ◽  
Born Again ◽  
Main Cavity

Abstract We present the analysis of infrared (IR) observations of the planetary nebula NGC 40 together with spectral analysis of its [WC]-type central star HD 826. Spitzer IRS observations were used to produce spectral maps centred at polycyclic aromatic hydrocarbons (PAH) bands and ionic transitions to compare their spatial distribution. The ionic lines show a clumpy distribution of material around the main cavity of NGC 40, with the emission from [Ar ii] being the most extended, whilst the PAHs show a rather smooth spatial distribution. Analysis of ratio maps shows the presence of a toroidal structure mainly seen in PAH emission, but also detected in a Herschel PACS 70 $\mu$m image. We argue that the toroidal structure absorbs the UV flux from HD 826, preventing the nebula to exhibit lines of high-excitation levels as suggested by previous authors. We discuss the origin of this structure and the results from the spectral analysis of HD 826 under the scenario of a late thermal pulse.

scholarly journals Fast Winds in Planetary Nebulae

1983 ◽  
Vol 103 ◽  
pp. 305-316 ◽  
Author(s):  
F. D. Kahn
Keyword(s):  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Central Star ◽  
Taylor Instability ◽  
Considerable Time ◽  
Left Behind ◽  
Hot Gas ◽  
Fast Wind ◽  
Rayleigh Taylor Instability ◽  
Red Giant

A planetary nebula consists mainly of gas ejected slowly by a red giant. Its dynamics is dominated by the hot central star which is left behind later. In particular a fast wind from this star forms a bubble of hot gas which fills the inner part of the nebula and pushes the envelope into a shell. This shell remains only partly ionized for a considerable time. Its non-ionized part is subject to a Rayleigh-Taylor instability, and is expected to break up into fragments which remain behind in the HII part of the nebula.

scholarly journals Molecular Radio Line Observations of Mass Loss From Red Giants

1989 ◽  
Vol 106 ◽  
pp. 321-338
Author(s):  
H. Olofsson
Keyword(s):  
Mass Loss ◽  
Planetary Nebula ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Central Star ◽  
Circumstellar Envelope ◽  
Red Giants ◽  
Radio Line ◽  
Red Giant ◽  
Evolution With Time

AbstractThe number of molecules detected at radio wavelengths in envelopes around red giants stands presently at 36. Among these OH and CO have proven to be the most useful for the study of the physical characteristics of a circumstellar envelope. The mass loss rate of the central star can be relatively accurately estimated and it appears possible to trace its evolution with time. Also fascinating objects in transition from the red giant phase to the planetary nebula phase are becoming observationally accessible.

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