Topic
Equatorial ring
About: Equatorial ring is a research topic. Over the lifetime, 24 publications have been published within this topic receiving 731 citations.
Papers
TL;DR: In this paper, the interaction of the slow wind blown by an asymptotic giant branch (AGB) star with a collimated fast wind (CFW) blown by its main-sequence or white dwarf companion, at orbital separations in the range of several AU a 200 AU, is discussed.
Abstract: We discuss the interaction of the slow wind blown by an asymptotic giant branch (AGB) star with a collimated fast wind (CFW) blown by its main-sequence or white dwarf companion, at orbital separations in the range of several AU a 200 AU. The CFW results from accretion of the AGB wind into an accretion disk around the companion. The fast wind is collimated by the accretion disk. We argue that such systems are the progenitors of bipolar planetary nebulae and bipolar symbiotic nebulae with a very narrow equatorial waist between the two polar lobes. The CFW wind will form two lobes along the symmetry axis and will further compress the slow wind near the equatorial plane, leading to the formation of a dense slowly expanding ring. Therefore, contrary to the common claim that a dense equatorial ring collimates the bipolar flow, we argue that in the progenitors of very narrow waist bipolar planetary nebulae, the CFW, through its interaction with the slow wind, forms the dense equatorial ring. Only later in the evolution, and after the CFW and slow wind cease, does the mass-losing star leave the AGB and blow a second, more spherical, fast wind. At this stage the flow structure becomes the one that is commonly assumed for bipolar planetary nebulae, i.e., collimation of the fast wind by the dense equatorial material. However, this results in the broadening of the waist in the equatorial plane and cannot by itself account for the presence of very narrow waists or jets. We conduct a population synthesis study of the formation of planetary nebulae in wide binary systems which quantitatively supports the proposed model. The population synthesis code follows the evolution of both stars and their arbitrarily eccentric orbit, including mass loss via stellar winds, for 5 ? 104 primordial binaries. We show the number of expected systems that blow a CFW is in accord with the number found from observations, to within the many uncertainties involved. Overall, we find that ~5% of all planetary nebulae are bipolars with very narrow waists. Our population synthesis not only supports the CFW model but more generally supports the binary model for the formation of bipolar planetary nebulae.
202 citations
TL;DR: In this paper, the authors constructed and analyzed the most complete map to date of the progenitor's circumstellar environment, using ground and space-based imaging from the past 16 years PSF-matched difference-imaging analyses of data from 1988 through 1997 reveal material between 1 and 28 lt-yr from the SN.
Abstract: Surrounding SN 1987A is a three-ring nebula attributed to interacting stellar winds, yet no model has successfully reproduced this system Fortunately, the progenitor's mass-loss history can be reconstructed using light echoes, in which scattered light from the supernova traces the three-dimensional morphology of its circumstellar dust In this paper, we construct and analyze the most complete map to date of the progenitor's circumstellar environment, using ground- and space-based imaging from the past 16 years PSF-matched difference-imaging analyses of data from 1988 through 1997 reveal material between 1 and 28 lt-yr from the SN Previously known structures, such as an inner hourglass, Napoleon's Hat, and a contact discontinuity, are probed in greater spatial detail than before Previously unknown features are also discovered, such as a southern counterpart to Napoleon's Hat Careful analyses of these echoes allows the reconstruction of the probable circumstellar environment, revealing a richly structured bipolar nebula An outer, double-lobed Peanut, which is believed to be the contact discontinuity between red supergiant and main-sequence winds, is a prolate shell extending 28 lt-yr along the poles and 11 lt-yr near the equator Napoleon's Hat, previously believed to be an independent structure, is the waist of this Peanut, which is pinched to a radius of 6 lt-yr Interior to this is a cylindrical hourglass, 1 lt-yr in radius and 4 lt-yr long, which connects to the Peanut by a thick equatorial disk The nebulae are inclined 41° south and 8° east of the line of sight, slightly elliptical in cross section, and marginally offset west of the SN From the hourglass to the large, bipolar lobes, echo fluxes suggest that the gas density drops from 1-3 to 003 cm-3, while the maximum dust-grain size increases from ~02 to 2 μm, and the silicate:carbonaceous dust ratio decreases The nebulae have a total mass of ~17 M☉ The geometry of the three rings is studied, suggesting the northern and southern rings are located 13 and 10 lt-yr from the SN, while the equatorial ring is elliptical (b/a 098), and spatially offset in the same direction as the hourglass
96 citations
TL;DR: In this paper, the authors reported the discovery of two new circumstellar ring nebulae in the western Carina Nebula, and discussed their significance in stellar evolution, where the two new objects, SBW 1 and SBW 2, resemble a lidless staring eye and encircles a B1.5 Iab supergiant.
Abstract: We report the discovery of two new circumstellar ring nebulae in the western Carina Nebula, and we discuss their significance in stellar evolution. The brighter of the two new objects, SBW 1, resembles a lidless staring eye and encircles a B1.5 Iab supergiant. Although seen in Carina, its luminosity class and radial velocity imply a larger distance of ~7 kpc in the far Carina arm. At that distance its size and shape are nearly identical to the equatorial ring around SN 1987A, but SBW 1's low N abundance indicates that the ring was excreted without its star passing through a red supergiant phase. The fainter object, SBW 2, is a more distorted ring, is N-rich, and is peculiar in that its central star seems to be invisible. We discuss the implications of these two new nebulae in context with other circumstellar rings such as those around SN 1987A, Sher 25, HD 168625, RY Scuti, WeBo 1, SuWt 2, and others. The ring bearers fall into two groups: Five rings surround hot supergiants, and it is striking that all except for the one known binary are carbon copies of the ring around SN 1987A. We propose a link between these B supergiant rings and B[e] supergiants, where the large spatially resolved rings derive from the same material that would have given rise to emission lines during the earlier B[e] phase, when it was much closer to the star. The remaining four rings surround evolved intermediate-mass stars; all members of this ring fellowship are close binaries, hinting that binary interactions govern the forging of such rings. Two-thirds of our sample are found in or near giant H II regions. We estimate that there may be several thousand more dark rings in the Galaxy, but we are scarcely aware of their existence?either because they are only illuminated in precious few circumstances or because of selection effects. For intermediate-mass stars, these rings might be the preexisting equatorial density enhancements invoked to bind the waists of bipolar nebulae.
87 citations
TL;DR: In this article, the authors used integral field spectroscopy to image the supernova ejecta and the equatorial ring in the emission lines of [Si I]-[Fe II] and He I.
Abstract: Twenty years after the explosion of SN 1987A, we are now able to observe the three-dimensional spatially resolved inner ejecta. Detailed mapping of newly synthesised material and its radioactive decay daughter products sheds light on the explosion mechanism. This may reveal the geometry of the explosion and its connection to the equatorial ring and the outer rings around SN 1987A. We have used integral field spectroscopy to image the supernova ejecta and the equatorial ring in the emission lines of [Si I]+[Fe II] and He I. The spectral information can be mapped into a radial velocity image revealing the expansion of the ejecta both as projected onto the sky and perpendicular to the sky plane. The inner ejecta are spatially resolved in a North-South direction and are clearly asymmetric. We argue that the bulk of the ejecta is situated in the same plane as defined by the equatorial ring and does not form a bipolar structure as has been suggested. The exact shape of the ejecta is modelled and we find that an elongated triaxial ellipsoid fits the observations best. From our spectral analyses of the ejecta spectrum we find that most of the He I, [Si I] and [Fe I-II] emission originates in the core material which has undergone explosive nucleosynthesis. The He I emission may be the result of alpha-rich freeze-out if the positron energy is deposited locally. Our observations clearly indicate a non-symmetric explosion mechanism for SN 1987A. The elongation and velocity asymmetries point towards a large-scale spatial non-spherical distribution as predicted in recent explosion models. The orientation of the ejecta in the plane of the equatorial ring argues against a jet-induced explosion through the poles due to stellar rotation.
56 citations
TL;DR: In this article, Chandra images of the supernova remnant 1987A have been used to study the evolution of the ring of supernova supernova 1987A over the last 16 years, showing that the 0.5-2 keV light curve has remained constant at 8x10^-12 erg s^-1 cm^-2 since 9500 days.
Abstract: Updated imaging and photometric results from Chandra observations of SN 1987A, covering the last 16 years, are presented. We find that the 0.5-2 keV light curve has remained constant at ~8x10^-12 erg s^-1 cm^-2 since 9500 days, with the 3-8 keV light curve continuing to increase until at least 10000 days. The expansion rate of the ring is found to be energy dependent, such that after day 6000 the ring expands faster in the 2-10 keV band than it does at energies <2 keV. Images show a reversal of the east-west asymmetry between 7000 and 8000 days after the explosion. The latest images suggest the southeastern side of the equatorial ring is beginning to fade. Consistent with the latest optical and infrared results, our Chandra analysis indicates the blast wave is now leaving the dense equatorial ring, which marks the beginning of a major change in the evolutionary phase of the supernova remnant 1987A.
45 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2017 | 1 |
| 2016 | 1 |
| 2015 | 2 |
| 2013 | 1 |
| 2010 | 3 |
| 2009 | 1 |