scholarly journals Sh 2-68 – A Planetary Nebula Leaving it's Mark on the Interstellar Medium

2003 ◽  
Vol 209 ◽  
pp. 525-526 ◽  
Author(s):  
F. Kerber ◽  
F. Guglielmetti ◽  
R. Mignani ◽  
M. Roth
Keyword(s):  
Interstellar Medium ◽  
Planetary Nebula ◽  
Galactic Disk ◽  
Central Star ◽  
Main Body ◽  
Left Behind ◽  
Sky Survey ◽  
Cometary Tail ◽  
Direct Confirmation

Using Hα images from the Southern H-Alpha Sky Survey Atlas (SHASSA) we have discovered a “cometary tail” of ionized matter extending at least 30 arcmin from the main body of the planetary nebula Sh 2-68 (PN G030.6+06.2). This tail is aligned with the proper motion of the central star and is obviously a contrail of material left behind by Sh 2-68 moving in a Galactic Disk orbit. The tail's existence is a direct confirmation of Sh 2-68's interaction with the interstellar medium (ISM) and highlights the possibly important role of the ISM's magnetic field.

scholarly journals The LMC Planetary Nebula N66 Revisited: Nebular Kinematics and Stellar Models

2003 ◽  
Vol 209 ◽  
pp. 579-580
Author(s):  
M. Peña ◽  
W.-R. Hamann ◽  
M. T. Ruiz
Keyword(s):  
Mass Loss ◽  
Planetary Nebula ◽  
Central Star ◽  
Main Body ◽  
Complex Morphology ◽  
Loss Event ◽  
Stellar Models ◽  
Dark Material

LMC-N66 is an extraordinary planetary nebula whose central star underwent a violent mass loss event which has lasted for 10 years. The outburst reached its maximum in 1994. Since then the star has been slowly fading. During the stellar outburst, the nebular lines have shown no changes.The nebula shows a complex morphology. Two very bright lobes at both sides of the central star, almost aligned in the E-W direction, constitute the main body of the nebula. Several knots and filaments are conspicuous over the surface lying preferentially on the S-E and N-W directions. A couple of faint, extended loops are also detected in the S-E and N-W directions at both sides of the star. The extension of these loops are larger than 0.5 pc at the LMC distance. A no emitting-zone in the S-W quadrant, seems to be part of a dusty toroid around the central star, although the central star is not obscured by such a dark material (see Blades et ale 1992 for a description of N66 morphology).

scholarly journals SALT HRS Discovery of the Binary Nucleus of the Etched Hourglass Nebula MyCn 18

2018 ◽  
Vol 35 ◽  
Author(s):  
Brent Miszalski ◽  
Rajeev Manick ◽  
Joanna Mikołajewska ◽  
Hans Van Winckel ◽  
Krystian Iłkiewicz
Keyword(s):  
Planetary Nebula ◽  
Central Star ◽  
Morphological Features ◽  
Formation Mechanisms ◽  
Orbital Inclination ◽  
Classical Nova ◽  
Formation History ◽  
The Common ◽  
Star Position

AbstractThe shaping of various morphological features of planetary nebulae is increasingly linked to the role of binary central stars. Identifying a binary within a planetary nebula offers a powerful tool with which to directly investigate the formation mechanisms behind these features. The Etched Hourglass Nebula, MyCn 18, is the archetype for several binary-linked morphological features, yet it has no identified binary nucleus. It has the fastest jets seen in a planetary nebula of 630 km s−1, a central star position offset from the nebula centre, and a bipolar nebula with a very narrow waist. Here we report on the Southern African Large Telescope High Resolution Spectrograph detection of radial velocity variability in the nucleus of MyCn 18 with an orbital period of 18.15 ± 0.04 d and a semi-amplitude of 11.0 ± 0.3 km s−1. Adopting an orbital inclination of 38 ± 5° and a primary mass of 0.6 ± 0.1 M⊙ yields a secondary mass of 0.19 ± 0.05 M⊙ corresponding to an M5V companion. The detached nature of the binary rules out a classical nova as the origin of the jets and the offset central star as hypothesised in the literature. Furthermore, scenarios that produce the offset central star during the AGB and that form narrow waist bipolar nebulae result in orbital separations 80–800 times larger than observed in MyCn 18. The inner hourglass and jets may have formed from part of the common envelope ejecta that remained bound to the binary system in a circumbinary disk, whereas the offset central star position may best be explained by proper motion. Detailed simulations of MyCn 18 are encouraged that are compatible with the binary nucleus to further investigate its complex formation history.

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 The role of close pair interactions in triggering stellar bars and rings

2012 ◽  
Vol 10 (H16) ◽  
pp. 369-369
Author(s):  
Preethi Nair ◽  
Sara Ellison ◽  
David Patton
Keyword(s):  
Central Star ◽  
Sloan Digital Sky Survey ◽  
Close Pair ◽  
Sky Survey ◽  
Significant Difference ◽  
The Galaxy ◽  
Pair Separation ◽  
Pair Interactions ◽  
Close Pairs

AbstractRecent works which have looked at bars in clusters versus the field have found no significant difference in bar fraction. However, other works (Nair & Abraham 2010, Lee et al.2012) have found that bar fractions depend sensitively on the mass, morphology and color of the galaxy. In addition, simulations suggest that bar formation may depend on the merger ratio of close pair interactions as well as on the separation between the pairs. In this work, we analyze the bar fractions in a complete sample of ≈23,000 close pairs derived from the Sloan Digital Sky Survey Data Release 7. We will present results illustrating the dependence of bar and ring fractions as a function of merger mass ratio, pair separation, galaxy morphology, and stellar mass. I will further compare the role of bars and close pairs in triggering central star formation and AGN.

scholarly journals PFP 1: A Large Planetary Nebula Caught in the First Stages of ISM Interaction

2004 ◽  
Vol 21 (3) ◽  
pp. 334-343 ◽  
Author(s):  
Mark J. Pierce ◽  
David J. Frew ◽  
Quentin A. Parker ◽  
Joachim Köppen
Keyword(s):  
Survey Data ◽  
Planetary Nebula ◽  
Surface Brightness ◽  
Central Star ◽  
The North ◽  
Sky Survey ◽  
Solar Composition ◽  
Low Surface Brightness ◽  
Imaging And Spectroscopy ◽  
Highly Evolved

AbstractThis paper presents (Hα + [Nii]) imaging and spectroscopy of a previously unknown, highly evolved planetary nebula of low excitation which is in the first stages of an interaction with the interstellar medium (ISM). It was discovered serendipitously from AAO/UKST Hα Survey images as part of a project to exploit the survey data and has evaded detection by previous surveys due to its very low surface brightness. It is a remarkable hollow-sphere planetary nebula, some 19´ across, making it one of the largest examples of its type. We estimate a radius of 1.5 pc and a distance of 550 pc as derived from a new Hα surface brightness–radius relation. PFP 1 has near-perfect circular symmetry, broken only at the north-western edge which is coupled with significantly increased (Hα + [Nii]) intensity, both of which provide evidence for an interaction with the ISM. We find a near solar composition for this object with possibly enhanced He and N abundances. A blue central star candidate has been identified from the SuperCosmos Sky Survey data.

When People Come First

2013 ◽  
Keyword(s):  
Global Health ◽  
Scale Up ◽  
Moral Economy ◽  
Health Science ◽  
Health It ◽  
Left Behind ◽  
New Research ◽  
Health Enterprise ◽  
Conceptual Work

This book critically assesses the expanding field of global health. It brings together an international and interdisciplinary group of scholars to address the medical, social, political, and economic dimensions of the global health enterprise through vivid case studies and bold conceptual work. The book demonstrates the crucial role of ethnography as an empirical lantern in global health, arguing for a more comprehensive, people-centered approach. Topics include the limits of technological quick fixes in disease control, the moral economy of global health science, the unexpected effects of massive treatment rollouts in resource-poor contexts, and how right-to-health activism coalesces with the increased influence of the pharmaceutical industry on health care. The chapters explore the altered landscapes left behind after programs scale up, break down, or move on. We learn that disease is really never just one thing, technology delivery does not equate with care, and biology and technology interact in ways we cannot always predict. The most effective solutions may well be found in people themselves, who consistently exceed the projections of experts and the medical-scientific, political, and humanitarian frameworks in which they are cast. This book sets a new research agenda in global health and social theory and challenges us to rethink the relationships between care, rights, health, and economic futures.

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.

scholarly journals The Remarkable Evolution of the Post-Agb Star FG SGE

1998 ◽  
Vol 11 (1) ◽  
pp. 363-363
Author(s):  
Johanna Jurcsik ◽  
Benjamin Montesinos
Keyword(s):  
Time Scales ◽  
Effective Temperature ◽  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Central Star ◽  
Evolutionary Models ◽  
Single Star ◽  
Line Intensities ◽  
Evolutionary Changes ◽  
Evolutionary Studies

FG Sagittae is one of the most important key objects of post-AGB stellar evolutionary studies. As a consequence of a final helium shell flash, this unique variable has shown real evolutionary changes on human time scales during this century. The observational history was reviewed in comparison with predictions from evolutionary models. The central star of the old planetary nebula (Hel-5) evolved from left to right in the HR diagram, going in just hundred years from the hot region of exciting sources of planetary nebulae to the cool red supergiant domain just before our eyes becoming a newly-born post-AGB star. The effective temperature of the star was around 50,000 K at the beginning of this century, and the last estimates in the late 1980s give 5,000-6,500 K. Recent spectroscopic observations obtained by Ingemar Lundström show definite changes in the nebular line intensities. This fact undoubtedly rules out the possibility that, instead of FG Sge, a hidden hot object would be the true central star of the nebula. Consequently, the observed evolutionary changes are connected with the evolution of a single star.

scholarly journals Characterization of symbiotic and associated bacteria from entomopathogenic nematode Heterorhabditis sp. (nematode: Heterorhabditidae) isolated from India

2020 ◽  
Vol 30 (1) ◽  
Author(s):  
Rashid Pervez ◽  
Showkat Ahmad Lone ◽  
Sasmita Pattnaik
Keyword(s):  
Insect Pests ◽  
Entomopathogenic Nematode ◽  
Alcaligenes Faecalis ◽  
Symbiotic Bacteria ◽  
Rrna Gene ◽  
Main Body ◽  
Associated Bacteria ◽  
Molecular Approaches

Abstract Background Entomopathogenic nematodes (EPNs) harboring symbiotic bacteria are one of the safest alternatives to the chemical insecticides for the control of various insect pests. Infective juveniles of EPNs locate a target insect, enter through the openings, and reach the hemocoel, where they release the symbiotic bacteria and the target gets killed by the virulence factors of the bacteria. Photorhabdus with Heterorhabditis spp. are well documented; little is known about the associated bacteria. Main body In this study, we explored the presence of symbiotic and associated bacteria from Heterorhabditis sp. (IISR-EPN 09) and characterized by phenotypic, biochemical, and molecular approaches. Six bacterial isolates, belonging to four different genera, were recovered and identified as follows: Photorhabdus luminescens, one each strain of Providencia vermicola, Pseudomonas entomophila, Alcaligenes aquatilis, and two strains of Alcaligenes faecalis based on the phenotypic, biochemical criteria and the sequencing of 16S rRNA gene. Conclusion P. luminescens is symbiotically associated with Heterorhabditis sp. (IISR-EPN 09), whereas P. vermicola, P. entomophila, A. aquatilis, and A. faecalis are the associated bacteria. Further studies are needed to determine the exact role of the bacterial associates with the Heterorhabditis sp.

scholarly journals SAO 244567 (HEN1357): A Post-Agb Star which has turned into a Planetary Nebula within the last 20 years

1998 ◽  
Vol 11 (1) ◽  
pp. 358-358
Author(s):  
M. Parthasarathy
Keyword(s):  
Planetary Nebula ◽  
Far Infrared ◽  
Central Star ◽  
Terminal Velocity ◽  
Galactic Latitude ◽  
Iras Source ◽  
High Galactic Latitude ◽  
Alpha Emission ◽  
Early Type Star ◽  
Emission Strength

SAO 244567 (Henl357) (IRAS 17119-5926) is a high galactic latitude (1 = 331°, b = −12°) early type star, originally classified as a B or A type H-alpha emission line star by Henize (1976). It is an IRAS source with far infrared colours similar to planetary nebulae. The IUE ultraviolet spectra obtained during the last eight years show that the central star is rapidly evolving. It is found that the central star of this young PN has faded by a factor of 3 within the last seven eight years. The terminal velocity of the stellar wind has decreased from −3500 km/sec in 1988 to almost zero in 1994. In 1988 the C IV (1550A) line which was a P-Cygni profile with strong absorption component had almost vanished by 1994. The CIII] 1909A emission strength increased markedly within 4 years from 1988 to 1992. The optical spectra obtained since 1990 shows very clearly only the nebular spectrum which is very similar to that of low excitation planetary nebula. The optical spectrum of SAO 244567 obtained in 1971 shows that it was a post-AGB B 1 or B2 supergiant at that time. This result shows that SAO 244567 has turned into a planetary nebula within the last 20 years. Recently Bobrowsky (1994) obtained narrowband optically resolved images in both H-beta and [OIII] 5007A with the HST planetary camera which revealed a well resolved nebula of size 2 seconds of arc. In this paper we discuss the recent new results.

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