Special Issue "Asymmetric Planetary Nebulae VII"

A special issue of Galaxies (ISSN 2075-4434).

Deadline for manuscript submissions: closed (30 June 2018)

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Guest Editor
Prof. Dr. Quentin A. Parker

Department of Physics, University of Hong Kong, Hong Kong, China
Website | E-Mail
Interests: late stage stellar evolution; planetary nebulae; binarity; multi-wavelength photometry; stellar evolution; wide field surveys; supernova remnants
Guest Editor
Prof. Noam Soker

Department of Physics, Technion – Israel Institute of Technology, Technion city, Haifa 32000, Israel
E-Mail
Interests: late stage stellar evolution; planetary nebulae; binarity; magnetic fields; multi-wavelength photometry; stellar evolution

Special Issue Information

Dear Colleagues,

Thank you all for agreeing to publish your APNVII conference presentations in the form of a paper submitted to the special peer reviewed conference proceedings kindly offered to us by the MDPI Galaxies journal. Below is a brief summary of the focus, scope and purpose of this special issue for your information. We look forward to receiving your submissions and the production of this special issue.

a. Focus: This Special Issue’s focus will be broadly based around the current broad and major themes and questions regarding late-stage stellar evolution, and especially planetary nebulae, via the invited and submitted talks

b. Scope: The scope of the meeting and, thus, the contents of this Special Issue include:

  • Shaping Mechanisms—role of binarity, magnetic fields and other factors
  • What can we learn from the major increase in known PNe?
  • How are post-AGB, pre-PNe and PNe phase shapes related?
  • What role do the properties of the central stars play?
  • What can we learn from jets and accretion disks in related/unrelated objects?
  • What do advances in evolutionary models and timescales tell us?
  • How do we maximally extract science from the available/planned facilities?
  • What are the most important current issues to resolve?

c. Purpose of the Special Issue:

  • This Special Issue will bring together the contents of the meeting and capture the status of the field at this time, in some real sense, and can become an important historical record
  • Special refereed conference proceedings will be well received and used as decent reference materials by participants and others, and will lead to increased cites in the field, and for the authors
  • The included reviews can be very useful
  • A Special Issue raises the profile of our community and the science we do

The Special Issue will form an important historical record of a major international conference and will include up to the minute cutting-edge materials that would not normally appear in the literature until 12–18 months later, when full refereed papers are eventually produced. The community will get a “heads-up” on important advances and thinking in a more timely manner.

Prof. Quentin A. Parker
Prof. Noam Soker
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Galaxies is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 350 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • late stage stellar evolution
  • planetary nebulae
  • binarity
  • magnetic fields
  • multi-wavelength photometry
  • stellar evolution
  • theory and observation

Published Papers (27 papers)

View options order results:
result details:
Displaying articles 1-27
Export citation of selected articles as:

Research

Open AccessArticle Understanding the Spatial Distributions of the Ionic/Atomic/Molecular/Dust Components in PNe
Received: 4 December 2018 / Revised: 28 December 2018 / Accepted: 29 December 2018 / Published: 4 January 2019
PDF Full-text (415 KB) | HTML Full-text | XML Full-text
Abstract
Planetary nebulae (PNe) are often recognized as the hallmark of compact H ii regions in the Universe. However, there exist dusty neutral regions extending beyond the central ionized region. We demonstrate that such dusty neutral regions (also known as photo-dissociation regions, or PDRs) [...] Read more.
Planetary nebulae (PNe) are often recognized as the hallmark of compact H ii regions in the Universe. However, there exist dusty neutral regions extending beyond the central ionized region. We demonstrate that such dusty neutral regions (also known as photo-dissociation regions, or PDRs) around the central ionized region are significant parts of PNe in terms of energetics and mass. We do so by using our latest dusty photoionization model of NGC 6781 (of 13 parameters) based on one of the most comprehensive panchromatic data sets ever assembled for a PN encompassing from X-ray to radio (of 136 constraining data, including 19 flux densities, 78 line fluxes, and 37 band fluxes). We find that NGC 6781, evolved out of a 2.25–3.0 M star located 460 pc away from us, possesses a massive concentration of neutral gas (molecular hydrogen) just beyond the central ionized region and that the amount of ionized gas in NGC 6781 is only 22% of the observationally accounted amount of matter in the circumstellar environment, which itself does not even account for the amount of mass presumably ejected by the central star during the last thermal pulse event according to the latest evolutionary models. This means that the observed nebula in this PN is only the tip of the iceberg. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessArticle Radio Continuum Spectra of Planetary Nebulae
Received: 4 December 2018 / Revised: 20 December 2018 / Accepted: 21 December 2018 / Published: 27 December 2018
PDF Full-text (290 KB) | HTML Full-text | XML Full-text
Abstract
Radio continuum emission of planetary nebulae is a rich source of information about their structure and physical parameters. Although radio emission is well studied, planetary nebulae show higher spectral indices than expected for homogeneous sphere. A few competing models exist in the literature [...] Read more.
Radio continuum emission of planetary nebulae is a rich source of information about their structure and physical parameters. Although radio emission is well studied, planetary nebulae show higher spectral indices than expected for homogeneous sphere. A few competing models exist in the literature to explain this discrepancy. We propose that it is related to non-spherical morphology of most of planetary nebulae. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessArticle UV Monochromatic Imaging of the Protoplanetary Nebula Hen 3-1475 Using HST STIS
Galaxies 2018, 6(4), 141; https://doi.org/10.3390/galaxies6040141
Received: 8 August 2018 / Revised: 10 December 2018 / Accepted: 11 December 2018 / Published: 14 December 2018
PDF Full-text (1407 KB) | HTML Full-text | XML Full-text
Abstract
Collimated outflows and jets play a critical role in shaping planetary nebulae (PNe), especially in the brief transition from a spherical AGB envelope to an aspherical PN, which is called the protoplanetary nebula (pPN) phase. We present UV observations of Hen 3-1475, a [...] Read more.
Collimated outflows and jets play a critical role in shaping planetary nebulae (PNe), especially in the brief transition from a spherical AGB envelope to an aspherical PN, which is called the protoplanetary nebula (pPN) phase. We present UV observations of Hen 3-1475, a bipolar pPN with fast, highly collimated jets, obtained with STIS on board the Hubble Space Telescope (HST). The deep, low-dispersion spectroscopy enabled monochromatic imaging of Hen 3-1475 in different UV nebular emission lines; this is the first of such attempt ever conducted for a pPN. The northwest inner knot (NW1) is resolved into four components in Mg ii λ 2800. Through comparison analysis with the HST optical narrowband images obtained 6 yr earlier, we found that these components of NW1 hardly move, despite of a negative gradient of high radial velocities, from −1550 km s - 1 on the innermost component to ∼−300 km s - 1 on the outermost. These NW1 knot components might thus be quasi-stationary shocks near the tip of the conical outflow of Hen 3-1475. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessArticle Spectroscopic and Photometric Variability of Three Oxygen Rich Post-AGB “Shell” Objects
Galaxies 2018, 6(4), 131; https://doi.org/10.3390/galaxies6040131
Received: 28 June 2018 / Revised: 28 November 2018 / Accepted: 29 November 2018 / Published: 3 December 2018
PDF Full-text (863 KB) | HTML Full-text | XML Full-text
Abstract
Light, color, and radial velocity data (2007–2015) for HD 161796, V887 Her, and HD 331319, three oxygen-rich post-AGB stars, have thus far not provided direct support for the binary hypothesis to explain the shapes of planetary nebulae and severely constrain the properties of [...] Read more.
Light, color, and radial velocity data (2007–2015) for HD 161796, V887 Her, and HD 331319, three oxygen-rich post-AGB stars, have thus far not provided direct support for the binary hypothesis to explain the shapes of planetary nebulae and severely constrain the properties of any such undetected companions. The light and velocity curves are complex, showing similar periods and variable amplitudes. Nevertheless, over limited time intervals, we compared the phasing of each. The color curves appear to peak with or slightly after the light curves, while the radial velocity curves peak about a quarter of a cycle before the light curves. Thus it appears that these post-AGB stars are brightest when smallest and hottest. The spectra of these objects are highly variable. The H α line has multiple, variable emission and absorption components. In these oxygen-rich post-AGB stars atmospheric lines, such as near-infrared Ca ii triplet and low-excitation atomic lines, also have multiple components and sometimes show line doubling, indicative of shocks induced by pulsation. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessArticle The Astrochemistry Implications of Quantum Chemical Normal Modes Vibrational Analysis
Galaxies 2018, 6(4), 123; https://doi.org/10.3390/galaxies6040123
Received: 8 October 2018 / Revised: 12 November 2018 / Accepted: 20 November 2018 / Published: 23 November 2018
PDF Full-text (315 KB) | HTML Full-text | XML Full-text
Abstract
Understanding the molecular vibrations underlying each of the unknown infrared emission (UIE) bands (such as those found at 3.3, 3.4, 3.5, 6.2, 6.9, 7.7, 11.3, 15.8, 16.4, 18.9 μm) observed in or towards astronomical objects is a vital link to uncover the [...] Read more.
Understanding the molecular vibrations underlying each of the unknown infrared emission (UIE) bands (such as those found at 3.3, 3.4, 3.5, 6.2, 6.9, 7.7, 11.3, 15.8, 16.4, 18.9 μ m) observed in or towards astronomical objects is a vital link to uncover the molecular identity of their carriers. This is usually done by customary classifications of normal-mode frequencies such as stretching, deformation, rocking, wagging, skeletal mode, etc. A large literature on this subject exists and since 1952 ambiguities in classifications of normal modes via this empirical approach were pointed out by Morino and Kuchitsu New ways of interpretation and analyzing vibrational spectra were sought within the theoretical framework of quantum chemistry. Many of these methods cannot easily be applied to the large, complex molecular systems which are one of the key research interests of astrochemistry. In considering this demand, a simple and new method of analyzing and classifying the normal mode vibrational motions of molecular systems was introduced. This approach is a fully quantitative method of analysis of normal-mode displacement vector matrices and classification of the characteristic frequencies (fundamentals) underlying the observed IR bands. Outcomes of applying such an approach show some overlap with customary empirical classifications, usually at short wavelengths. It provides a quantitative breakdown of a complex vibration (at longer wavelengths) into the contributed fragments such as their aromatic or aliphatic components. In addition, in molecular systems outside the classical models of chemical bonds and structures where the empirical approach cannot be applied, this quantitative method enables an interpretation of vibrational motion(s) underlying the IR bands. As a result, further modifications in the structures (modeling) and the generation of the IR spectra (simulating) of the UIE carriers, initiated by proposing a PAH model, can be implemented in an efficient way. Here fresh results on the vibrational origin of the spectacular UIE bands based on astrochemistry molecular models, explored through the lens of the quantitative method applied to thousands of different vibrational motion matrices are discussed. These results are important in the context of protoplanetary nebulae and planetary nebulae where various molecular species have been uncovered despite their harsh environments. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessArticle Planetary Nebulae Shaped by Common Envelope Evolution
Galaxies 2018, 6(4), 113; https://doi.org/10.3390/galaxies6040113
Received: 16 July 2018 / Revised: 29 September 2018 / Accepted: 2 October 2018 / Published: 26 October 2018
Cited by 8 | PDF Full-text (1132 KB) | HTML Full-text | XML Full-text
Abstract
The morphologies of planetary nebula have long been believed to be due to wind shaping processes in which a “fast wind” from the central star impacts a previously ejected envelope. It is assumed that asymmetries existing in the “slow wind” envelope would lead [...] Read more.
The morphologies of planetary nebula have long been believed to be due to wind shaping processes in which a “fast wind” from the central star impacts a previously ejected envelope. It is assumed that asymmetries existing in the “slow wind” envelope would lead to inertial confinement, shaping the resulting interacting wind flow. We present new results demonstrating the effectiveness of Common Envelope Evolution (CEE) at producing aspherical envelopes which, when impinged upon by a spherical fast stellar wind, produce highly bipolar, jet-like outflows. We have run two simple cases using the output of a single PHANTOM SPH CEE simulation. Our work uses the Adaptive Mesh Refinement code AstroBEAR to track the interaction of the fast wind and CEE ejecta allows us to follow the morphological evolution of the outflow lobes at high resolution in 3-D. Our two models bracket low and high momentum output fast winds. We find the interaction leads to highly collimated bipolar outflows. In addition, the bipolar morphology depends on the fast wind momentum injection rate. With this dependence comes the initiation of significant symmetry breaking between the top and bottom bipolar lobes. Our simulations, though simplified, confirm the long-standing belief that CEE can plan a major role in PPN and PN shaping. These simulations are intended as an initial exploration of the post-CE/PPN flow patterns that can be expected from central source outflows and CE ejecta. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessArticle Close Binaries and the Abundance Discrepancy Problem in Planetary Nebulae
Galaxies 2018, 6(4), 110; https://doi.org/10.3390/galaxies6040110
Received: 27 July 2018 / Revised: 12 October 2018 / Accepted: 15 October 2018 / Published: 19 October 2018
PDF Full-text (866 KB) | HTML Full-text | XML Full-text
Abstract
Motivated by the recent establishment of a connection between central star binarity and extreme abundance discrepancies in planetary nebulae, we have carried out a spectroscopic survey targeting planetary nebula with binary central stars and previously unmeasured recombination line abundances. We have discovered seven [...] Read more.
Motivated by the recent establishment of a connection between central star binarity and extreme abundance discrepancies in planetary nebulae, we have carried out a spectroscopic survey targeting planetary nebula with binary central stars and previously unmeasured recombination line abundances. We have discovered seven new extreme abundance discrepancies, confirming that binarity is key to understanding the abundance discrepancy problem. Analysis of all 15 objects with a binary central star and a measured abundance discrepancy suggests a cut-off period of about 1.15 days, below which extreme abundance discrepancies are found. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessArticle Infrared Observations of the Asymmetric Mass Loss of an AGB Star
Galaxies 2018, 6(4), 108; https://doi.org/10.3390/galaxies6040108
Received: 31 July 2018 / Revised: 9 October 2018 / Accepted: 9 October 2018 / Published: 12 October 2018
PDF Full-text (294 KB) | HTML Full-text | XML Full-text
Abstract
We report on the observations of the circumstellar envelope of the AGB star II Lup in the near- and mid-infrared with the use of direct imaging and interferometric techniques. Our findings indicate that the circumstellar envelope is not spherically symmetric and that the [...] Read more.
We report on the observations of the circumstellar envelope of the AGB star II Lup in the near- and mid-infrared with the use of direct imaging and interferometric techniques. Our findings indicate that the circumstellar envelope is not spherically symmetric and that the majority of the emission originates within 0.5 arcsec from the star. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessArticle Binary Interactions, High-Speed Outflows and Dusty Disks during the AGB-To-PN Transition
Galaxies 2018, 6(4), 102; https://doi.org/10.3390/galaxies6040102
Received: 9 July 2018 / Revised: 12 September 2018 / Accepted: 13 September 2018 / Published: 25 September 2018
PDF Full-text (324 KB) | HTML Full-text | XML Full-text
Abstract
It is widely believed that the dramatic transformation of the spherical outflows of AGB stars into the extreme aspherical geometries seen during the planetary nebula (PN) phase is linked to binarity and driven by the associated production of fast jets and central disks/torii. [...] Read more.
It is widely believed that the dramatic transformation of the spherical outflows of AGB stars into the extreme aspherical geometries seen during the planetary nebula (PN) phase is linked to binarity and driven by the associated production of fast jets and central disks/torii. The key to understanding the engines that produce these jets and the jet-shaping mechanisms lies in the study of objects in transition between the AGB and PN phases. I discuss the results of our recent studies with high-angular-resolution (with ALMA and HST) and at high-energies (with GALEX, XMM-Newton and Chandra) of several such objects, which reveal new details of close binary interactions and high-speed outflows. These include two PPNe (the Boomerang Nebula and IRAS 16342-3814), and the late carbon star, V Hya. The Boomerang Nebula is notable for a massive, high-speed outflow that has cooled below the microwave background temperature, making it the coldest object in the Universe. IRAS 16342-3814 is the prime example of the class of water-fountain pre-planetary nebulae or PPNe (very young PPNe with high-velocity H2O masers) and shows the signature of a precessing jet. V Hya ejects high-speed bullets every 8.5 years associated with the periastron passage of a companion in an eccentric orbit. I discuss our work on AGB stars with strongly-variable high-energy (FUV, X-ray) emission, suggesting that these objects are in the early stages of binary interactions that result in the formation of accretion disks and jets. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessArticle The Formation of Fullerenes in Planetary Nebulae
Galaxies 2018, 6(4), 101; https://doi.org/10.3390/galaxies6040101
Received: 31 July 2018 / Revised: 18 September 2018 / Accepted: 18 September 2018 / Published: 21 September 2018
Cited by 1 | PDF Full-text (337 KB) | HTML Full-text | XML Full-text
Abstract
In the last decade, fullerenes have been detected in a variety of astrophysical environments, with the majority being found in planetary nebulae. Laboratory experiments have provided us with insights into the conditions and pathways that can lead to fullerene formation, but it is [...] Read more.
In the last decade, fullerenes have been detected in a variety of astrophysical environments, with the majority being found in planetary nebulae. Laboratory experiments have provided us with insights into the conditions and pathways that can lead to fullerene formation, but it is not clear precisely what led to the formation of astrophysical fullerenes in planetary nebulae. We review some of the available evidence, and propose a mechanism where fullerene formation in planetary nebulae is the result of a two-step process where carbonaceous dust is first formed under unusual conditions; then, the fullerenes form when this dust is being destroyed. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessArticle AGBs, Post-AGBs and the Shaping of Planetary Nebulae
Received: 31 July 2018 / Revised: 28 August 2018 / Accepted: 29 August 2018 / Published: 17 September 2018
PDF Full-text (1483 KB) | HTML Full-text | XML Full-text
Abstract
During the last decades, observations, mostly with the Hubble Space Telescope, have revealed that round Planetary Nebulae were the exception rather than rule. A huge variety of features are observed, such as jets, discs, tori, showing that the ejection of material is not [...] Read more.
During the last decades, observations, mostly with the Hubble Space Telescope, have revealed that round Planetary Nebulae were the exception rather than rule. A huge variety of features are observed, such as jets, discs, tori, showing that the ejection of material is not due to isotropic radiation pressure on a spherical shell and that more physics is involved. This shaping process certainly occur early in the evolution of these low and intermediate mass stars and must leave imprints in the evolutionary stages prior the PN phase. Thanks to news instruments on the most advanced telescopes (e.g., the VLTI, SPHERE/VLT and ALMA), high angular resolution observations are revolutionising our view of the ejection of gas and dust during the AGB and post-AGB phases. In this review I will present the newest results concerning the mass loss from AGB stars, post-AGB stars and related objects. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessArticle X-ray Shaping of Planetary Nebulae
Received: 30 July 2018 / Revised: 3 September 2018 / Accepted: 4 September 2018 / Published: 11 September 2018
PDF Full-text (441 KB) | HTML Full-text | XML Full-text
Abstract
The stellar winds of the central stars of planetary nebulae play an essential role in the shaping of planetary nebulae. In the interacting stellar winds model, the fast stellar wind injects energy and momentum, which are transferred to the nebular envelope through an [...] Read more.
The stellar winds of the central stars of planetary nebulae play an essential role in the shaping of planetary nebulae. In the interacting stellar winds model, the fast stellar wind injects energy and momentum, which are transferred to the nebular envelope through an X-ray-emitting hot bubble. Together with other physical processes, such as the ionization of the nebular envelope, the asymmetrical mass-loss in the asymptotic giant branch (AGB), and the action of collimated outflows and magnetic fields, the pressurized hot gas determines the expansion and evolution of planetary nebulae. Chandra and XMM-Newton have provided us with detailed information of this hot gas. Here in this talk I will review our current understanding of the effects of the fast stellar wind in the shaping and evolution of planetary nebulae and give some hints of the promising future of this research. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessArticle Post-AGB Discs from Common-Envelope Evolution
Received: 26 July 2018 / Revised: 3 September 2018 / Accepted: 4 September 2018 / Published: 11 September 2018
PDF Full-text (320 KB) | HTML Full-text | XML Full-text
Abstract
Post-asymptotic giant branch (post-AGB) stars with discs are all binaries. Many of these binaries have orbital periods between 100 and 1000days so cannot have avoided mass transfer between the AGB star and its companion, likely through a common-envelope type interaction. We report [...] Read more.
Post-asymptotic giant branch (post-AGB) stars with discs are all binaries. Many of these binaries have orbital periods between 100 and 1000 days so cannot have avoided mass transfer between the AGB star and its companion, likely through a common-envelope type interaction. We report on preliminary results of our project to model circumbinary discs around post-AGB stars using our binary population synthesis code binary_c. We combine a simple analytic thin-disc model with binary stellar evolution to estimate the impact of the disc on the binary, and vice versa, fast enough that we can model stellar population and hence explore the rather uncertain parameter space involved with disc formation. We find that, provided the discs form with sufficient mass and angular momentum, and have an inner edge that is relatively close to the binary, they can both prolong the life of their parent post-AGB star and pump the eccentricity of orbits of their inner binaries. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessArticle The Morphology of the Outflow in the Grazing Envelope Evolution
Received: 24 July 2018 / Revised: 30 August 2018 / Accepted: 31 August 2018 / Published: 6 September 2018
Cited by 2 | PDF Full-text (999 KB) | HTML Full-text | XML Full-text
Abstract
We study the grazing envelope evolution (GEE), where a secondary star, which orbits the surface of a giant star, accretes mass from the giant envelope and launches jets. We conduct simulations of the GEE with different half-opening angles and velocities, and simulate the [...] Read more.
We study the grazing envelope evolution (GEE), where a secondary star, which orbits the surface of a giant star, accretes mass from the giant envelope and launches jets. We conduct simulations of the GEE with different half-opening angles and velocities, and simulate the onset phase and the spiralling-in phase. We discuss the resulting envelope structure and the outflow geometry. We find in the simulations of the onset phase with narrow jets that a large fraction of the ejected mass outflows along the polar directions. The mass ejected at these directions has the fastest velocity and the highest angular momentum magnitude. In the simulations of the spiralling-in phase, a large fraction of the ejected mass concentrates around the orbital plane. According to our findings, the outflow with the highest velocity is closer to the poles as we launch narrower jets. The outflow has a toroidal shape accompanied by two faster rings, one ring at each side of the equatorial plane. The interaction of the jets with the giant envelope causes these outflow structures, as we do not include in our simulations the secondary star gravity and the envelope self-gravity. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessArticle ALMA’s Acute View of pPNe: Through the Magnifying Glass... and What We Found There
Received: 28 June 2018 / Revised: 18 August 2018 / Accepted: 20 August 2018 / Published: 4 September 2018
PDF Full-text (2612 KB) | HTML Full-text | XML Full-text
Abstract
We present recent Atacama Large Millimeter/submillimeter Array (ALMA)-based studies of circumstellar envelopes (CSEs) around Asymptotic Giant Branch (AGB) stars and pre-Planetary Nebulae (pPNe). In only a few years of operation, ALMA is revolutionising the field of AGB-to-PN research by providing unprecedentedly detailed information [...] Read more.
We present recent Atacama Large Millimeter/submillimeter Array (ALMA)-based studies of circumstellar envelopes (CSEs) around Asymptotic Giant Branch (AGB) stars and pre-Planetary Nebulae (pPNe). In only a few years of operation, ALMA is revolutionising the field of AGB-to-PN research by providing unprecedentedly detailed information on the complex nebular architecture (at large but also on small scales down to a few ∼10 AU from the centre), dynamics and chemistry of the outflows/envelopes of low-to-intermediate mass stars in their late stages of the evolution. Here, we focus on continuum and molecular line mapping studies with high angular resolution and sensitivity of some objects that are key to understanding the complex PN-shaping process. In particular, we offer (i) a brief summary of ALMA observations of rotating disks in post-AGB objects and (ii) report on ALMA observations of OH 231.8+4.2 providing the most detailed and accurate description of the global nebular structure and kinematics of this iconic object to date. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessArticle Jsolated Stars of Low Metallicity
Received: 15 July 2018 / Revised: 8 August 2018 / Accepted: 9 August 2018 / Published: 15 August 2018
PDF Full-text (501 KB) | HTML Full-text | XML Full-text
Abstract
We study the effects of a reduced mass-loss rate on the evolution of low metallicity Jsolated stars, following our earlier classification for angular momentum (J) isolated stars. By using the stellar evolution code MESA we study the evolution with different mass-loss rate efficiencies [...] Read more.
We study the effects of a reduced mass-loss rate on the evolution of low metallicity Jsolated stars, following our earlier classification for angular momentum (J) isolated stars. By using the stellar evolution code MESA we study the evolution with different mass-loss rate efficiencies for stars with low metallicities of Z = 0.001 and Z = 0.004 , and compare with the evolution with solar metallicity, Z = 0.02 . We further study the possibility for late asymptomatic giant branch (AGB)—planet interaction and its possible effects on the properties of the planetary nebula (PN). We find for all metallicities that only with a reduced mass-loss rate an interaction with a low mass companion might take place during the AGB phase of the star. The interaction will most likely shape an elliptical PN. The maximum post-AGB luminosities obtained, both for solar metallicity and low metallicities, reach high values corresponding to the enigmatic finding of the PN luminosity function. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessArticle Revealing the True Nature of Hen 2-428
Received: 19 June 2018 / Revised: 7 August 2018 / Accepted: 10 August 2018 / Published: 14 August 2018
Cited by 1 | PDF Full-text (641 KB) | HTML Full-text | XML Full-text
Abstract
The nucleus of Hen 2-428 is a short orbital period (4.2 h) spectroscopic binary, whose status as potential supernovae type Ia progenitor has raised some controversy in the literature. We present preliminary results of a thorough analysis of this interesting system, which combines [...] Read more.
The nucleus of Hen 2-428 is a short orbital period (4.2 h) spectroscopic binary, whose status as potential supernovae type Ia progenitor has raised some controversy in the literature. We present preliminary results of a thorough analysis of this interesting system, which combines quantitative non-local thermodynamic (non-LTE) equilibrium spectral modelling, radial velocity analysis, multi-band light curve fitting, and state-of-the art stellar evolutionary calculations. Importantly, we find that the dynamical system mass that is derived by using all available He II lines does not exceed the Chandrasekhar mass limit. Furthermore, the individual masses of the two central stars are too small to lead to an SN Ia in case of a dynamical explosion during the merger process. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessFeature PaperArticle Surveying Planetary Nebulae Central Stars for Close Binaries: Constraining Evolution of Central Stars Based on Binary Parameters
Received: 7 July 2018 / Revised: 2 August 2018 / Accepted: 3 August 2018 / Published: 6 August 2018
Cited by 2 | PDF Full-text (276 KB) | HTML Full-text | XML Full-text
Abstract
The increase in discovered close binary central stars of planetary nebulae is leading to a sufficiently large sample to begin to make broader conclusions about the effect of close binary stars on common envelope evolution and planetary nebula formation. Herein I review some [...] Read more.
The increase in discovered close binary central stars of planetary nebulae is leading to a sufficiently large sample to begin to make broader conclusions about the effect of close binary stars on common envelope evolution and planetary nebula formation. Herein I review some of the recent results and conclusions specifically relating close binary central stars to nebular shaping, common envelope evolution off the red giant branch, and the total binary fraction and double degenerate fraction of central stars. Finally, I use parameters of known binary central stars to explore the relationship between the proto-planetary nebula and planetary nebula stages, demonstrating that the known proto-planetary nebulae are not the precursors of planetary nebulae with close binary central stars. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessArticle Analysis of Multiple Shell Planetary Nebulae Based on HST/WFPC2 Extended 2D Diagnostic Diagrams
Received: 27 June 2018 / Revised: 30 July 2018 / Accepted: 1 August 2018 / Published: 3 August 2018
PDF Full-text (1186 KB) | HTML Full-text | XML Full-text
Abstract
The investigation of gaseous nebulae, emitting in forbidden lines, is often based extensively on diagnostic diagrams. The special physics of these lines often allows for disentangling with a few line ratios normally coupled thermodynamic parameters like electron temperature, density and properties of the [...] Read more.
The investigation of gaseous nebulae, emitting in forbidden lines, is often based extensively on diagnostic diagrams. The special physics of these lines often allows for disentangling with a few line ratios normally coupled thermodynamic parameters like electron temperature, density and properties of the photo-ionizing radiation field. Diagnostic diagrams are usually used for the investigation of planetary nebulae as a total. We investigated the extension of such integrated properties towards spatially resolved 2D diagnostics, using Hubble Space Telescope/Wide Field Planetary Camera 2 (HST/WFPC2) narrow band images. For this purpose, we also derived a method to isolate pure Hα emission from the [N ii] contamination as normally suffering in the F656N HST/WFPC2 filter. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessArticle Simulations and Modeling of Intermediate Luminosity Optical Transients and Supernova Impostors
Received: 23 June 2018 / Revised: 30 July 2018 / Accepted: 30 July 2018 / Published: 1 August 2018
PDF Full-text (482 KB) | HTML Full-text | XML Full-text
Abstract
More luminous than classical novae, but less luminous than supernovae, lies the exotic stellar eruptions known as Intermediate luminosity optical transients (ILOTs). They are divided into a number of sub-groups depending on the erupting progenitor and the properties of the eruption. A large [...] Read more.
More luminous than classical novae, but less luminous than supernovae, lies the exotic stellar eruptions known as Intermediate luminosity optical transients (ILOTs). They are divided into a number of sub-groups depending on the erupting progenitor and the properties of the eruption. A large part of the ILOTs is positioned on the slanted Optical Transient Stripe (OTS) in the Energy-Time Diagram (ETD) that shows their total energy vs. duration of their eruption. We describe the different kinds of ILOTs that populate the OTS and other parts of the ETD. The high energy part of the OTS hosts the supernova impostors—giant eruptions (GE) of very massive stars. We show the results of the 3D hydrodynamical simulations of GEs that expose the mechanism behind these GEs and present new models for recent ILOTs. We discuss the connection between different kinds of ILOTs and suggest that they have a common energy source—gravitational energy released by mass transfer. We emphasize similarities between Planetary Nebulae (PNe) and ILOTs, and suggest that some PNe were formed in an ILOT event. Therefore, simulations used for GEs can be adapted for PNe, and used to learn about the influence of the ILOT events on the central star of the planetary nebula. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessArticle Simulations of the Formation and X-ray Emission from Hot Bubbles in Planetary Nebulae
Received: 26 June 2018 / Revised: 18 July 2018 / Accepted: 23 July 2018 / Published: 30 July 2018
PDF Full-text (519 KB) | HTML Full-text | XML Full-text
Abstract
High-quality X-ray observations of planetary nebulae (PNe) have demonstrated that the X-ray-emitting gas in their hot bubbles have temperatures in the small range TX = (1 − 3) × 106 K. However, according to theoretical expectations, adiabatically-shocked wind-blown bubbles should have [...] Read more.
High-quality X-ray observations of planetary nebulae (PNe) have demonstrated that the X-ray-emitting gas in their hot bubbles have temperatures in the small range TX = (1 − 3) × 106 K. However, according to theoretical expectations, adiabatically-shocked wind-blown bubbles should have temperatures up to two orders of magnitude higher. Numerical simulations show that instabilities at the interface between the hot bubble and the nebular material form clumps and filaments that generate an intermediate-temperature turbulent mixing layer. We describe the X-ray properties resulting from simulations of PNe in our Galaxy and the Magellanic Clouds. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessArticle The Real-Time Evolution of V4334 Sgr
Received: 19 June 2018 / Revised: 23 July 2018 / Accepted: 24 July 2018 / Published: 26 July 2018
PDF Full-text (467 KB) | HTML Full-text | XML Full-text
Abstract
V4334 Sgr (Sakurai’s object) is an enigmatic evolved star that underwent a very late thermal pulse a few years before its discovery in 1996. It ejected a new hydrogen-deficient nebula in the process. The source has been observed continuously since, at many wavelengths [...] Read more.
V4334 Sgr (Sakurai’s object) is an enigmatic evolved star that underwent a very late thermal pulse a few years before its discovery in 1996. It ejected a new hydrogen-deficient nebula in the process. The source has been observed continuously since, at many wavelengths ranging from the optical to the radio regime. In this paper we evaluate these data and discuss the evolution of this object. We reach the conclusion that we have seen no evidence for photoionization of the nebula yet and that the spectral features we see are caused either by shocks or by dust. These shocks are an integral part of the hydrodynamic shaping that is now producing a new bipolar nebula inside the old planetary nebula (PN), implying that we have a detailed observational record of the very early stages of the shaping of a bipolar nebula. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessArticle Planetary Nebulae Embryo after a Common Envelope Event
Received: 7 June 2018 / Revised: 1 July 2018 / Accepted: 9 July 2018 / Published: 19 July 2018
Cited by 1 | PDF Full-text (619 KB) | HTML Full-text | XML Full-text
Abstract
In the centers of some planetary nebulae are found close binary stars. The formation of those planetary nebulae was likely through a common envelope event, which transformed an initially-wide progenitor binary into the currently observed close binary, while stripping the outer layers away. [...] Read more.
In the centers of some planetary nebulae are found close binary stars. The formation of those planetary nebulae was likely through a common envelope event, which transformed an initially-wide progenitor binary into the currently observed close binary, while stripping the outer layers away. A common envelope event proceeds through several qualitatively different stages, each of which ejects matter at its own characteristic speed, and with a different degree of symmetry. Here, we present how typical post-common envelope ejecta looks kinematically a few years after the start of a common envelope event. We also show some asymmetric features we have detected in our simulations (jet-like structures, lobes, and hemispheres). Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessArticle Spectroscopy of Planetary Nebulae with Herschel: A Beginners Guide
Received: 28 May 2018 / Revised: 11 July 2018 / Accepted: 13 July 2018 / Published: 17 July 2018
PDF Full-text (2824 KB) | HTML Full-text | XML Full-text
Abstract
A brief overview of the Herschel Space Telescope PACS and SPIRE spectrographs is given, pointing out aspects of working with the data products that should be considered by anyone using them. Some preliminary results of Planetary Nebulae (PNe) taken from the Herschel Planetary [...] Read more.
A brief overview of the Herschel Space Telescope PACS and SPIRE spectrographs is given, pointing out aspects of working with the data products that should be considered by anyone using them. Some preliminary results of Planetary Nebulae (PNe) taken from the Herschel Planetary Nebula Survey (HerPlaNs) programme are then used to demonstrate what can be done with spectroscopy observations made with PACS. The take-home message is that using the full 3D information that PACS spectroscopy observations give will greatly aid in the interpretation of PNe. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessArticle On the Origin of Morphological Structures of Planetary Nebulae
Received: 24 May 2018 / Revised: 17 June 2018 / Accepted: 22 June 2018 / Published: 26 June 2018
Cited by 1 | PDF Full-text (610 KB) | HTML Full-text | XML Full-text
Abstract
We suggest that most of the mass in planetary nebulae (PNe) resides in the equatorial region and the spherical envelope and the optically bright lobes of PNe are in fact low-density cavities cleared out by fast outflows and photoionized by UV photons leaked [...] Read more.
We suggest that most of the mass in planetary nebulae (PNe) resides in the equatorial region and the spherical envelope and the optically bright lobes of PNe are in fact low-density cavities cleared out by fast outflows and photoionized by UV photons leaked from the torus. The nature of multi-polar PNe is discussed under this framework. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessFeature PaperArticle Sliding along the Eddington Limit—Heavy-Weight Central Stars of Planetary Nebulae
Received: 23 April 2018 / Revised: 14 June 2018 / Accepted: 15 June 2018 / Published: 19 June 2018
PDF Full-text (883 KB) | HTML Full-text | XML Full-text
Abstract
Due to thermal pulses, asymptotic giant branch (AGB) stars experience periods of convective mixing that provide ideal conditions for slow neutron-capture nucleosynthesis. These processes are affected by large uncertainties and are still not fully understood. By the lucky coincidence that about a quarter [...] Read more.
Due to thermal pulses, asymptotic giant branch (AGB) stars experience periods of convective mixing that provide ideal conditions for slow neutron-capture nucleosynthesis. These processes are affected by large uncertainties and are still not fully understood. By the lucky coincidence that about a quarter of all post-AGB stars turn hydrogen-deficient in a final flash of the helium-burning shell, they display nuclear processed material at the surface providing an unique insight to nucleosynthesis and mixing. We present results of non-local thermodynamic equilibrium spectral analyses of the extremely hot, hydrogen-deficient, PG 1159-type central stars of the Skull Nebula NGC 246 and the “Galactic Soccerballs” Abell 43 and NGC 7094. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Open AccessArticle Planets, Planetary Nebulae, and Intermediate Luminosity Optical Transients (ILOTs)
Received: 16 April 2018 / Revised: 24 May 2018 / Accepted: 24 May 2018 / Published: 28 May 2018
PDF Full-text (3706 KB) | HTML Full-text | XML Full-text
Abstract
I review some aspects related to the influence of planets on the evolution of stars before and beyond the main sequence. Some processes include the tidal destruction of a planet on to a very young main sequence star, on to a low-mass main [...] Read more.
I review some aspects related to the influence of planets on the evolution of stars before and beyond the main sequence. Some processes include the tidal destruction of a planet on to a very young main sequence star, on to a low-mass main sequence star, and on to a brown dwarf. This process releases gravitational energy that might be observed as a faint intermediate luminosity optical transient (ILOT) event. I then summarize the view that some elliptical planetary nebulae are shaped by planets. When the planet interacts with a low-mass, upper asymptotic giant branch (AGB) star, it both enhances the mass-loss rate and shapes the wind to form an elliptical planetary nebula, mainly by spinning up the envelope and by exciting waves in the envelope. If no interaction with a companion, stellar or substellar, takes place beyond the main sequence, the star is termed a Jsolated star, and its mass-loss rates on the giant branches are likely to be much lower than what is traditionally assumed. Full article
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII) Printed Edition available
Figures

Figure 1

Galaxies EISSN 2075-4434 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top