scholarly journals Autopsy of the Supernova Remnant Cassiopeia A

2013 ◽  
Vol 9 (S296) ◽  
pp. 155-159
Author(s):  
Dan Milisavljevic ◽  
Robert A. Fesen
Keyword(s):  
Large Scale ◽  
Supernova Remnant ◽  
Three Dimensional ◽  
Radioactive Material ◽  
Core Collapse ◽  
Common Phenomenon ◽  
Cassiopeia A ◽  
Circular Rings ◽  
Cas A ◽  
Emission Line Profile

AbstractThree-dimensional kinematic reconstructions of optically emitting ejecta in the young Galactic supernova remnant Cassiopeia A (Cas A) are discussed. The reconstructions encompass the remnant's faint outlying ejecta knots, including the exceptionally high-velocity NE and SW streams of debris often referred to as ‘jets’. The bulk of Cas A's ejecta are arranged in several circular rings with diameters between approximately 30″ (0.5 pc) and 2′ (2 pc). We suggest that similar large-scale ejecta rings may be a common phenomenon of young core-collapse remnants and may explain lumpy emission line profile substructure sometimes observed in spectra of extragalactic core-collapse supernovae years after explosion. A likely origin for these large ejecta rings is post-explosion input of energy from plumes of radioactive 56Ni-rich ejecta that rise, expand, and compress non-radioactive material to form bubble-like structures.

scholarly journals Spectropolarimetry of stripped-envelope supernovae: observations and modelling

2017 ◽  
Vol 375 (2105) ◽  
pp. 20160273 ◽  
Author(s):  
Masaomi Tanaka
Keyword(s):  
Large Scale ◽  
Massive Stars ◽  
Three Dimensional ◽  
Core Collapse ◽  
Ion Distribution ◽  
Typical Size ◽  
Cassiopeia A ◽  
Accretion Shock

Spectropolarimetry is one of the most powerful methods to study the multi-dimensional geometry of supernovae (SNe). We present a brief summary of the spectropolarimetric observations of stripped-envelope core-collapse SNe. Observations indicate that stripped-envelope SNe generally have a non-axisymmetric ion distribution in the ejecta. Three-dimensional clumpy geometry nicely explains the observed properties. A typical size of the clumps deduced from observations is relatively large: 25% of the photosphere. Such a large-scale clumpy structure is similar to that observed in Cassiopeia A, and suggests that large-scale convection or standing accretion shock instability takes place at the onset of the explosion. This article is part of the themed issue ‘Bridging the gap: from massive stars to supernovae’.

scholarly journals Spatial distribution of radionuclides in 3D models of SN 1987A and Cas A

2017 ◽  
Vol 12 (S331) ◽  
pp. 148-156 ◽  
Author(s):  
Hans-Thomas Janka ◽  
Michael Gabler ◽  
Annop Wongwathanarat
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
3D Models ◽  
Core Collapse ◽  
Mixing Processes ◽  
Free Expansion ◽  
3D Simulations ◽  
Sn 1987A ◽  
Explosion Mechanism ◽  
Cas A

AbstractFostered by the possibilities of multi-dimensional computational modeling, in particular the advent of three-dimensional (3D) simulations, our understanding of the neutrino-driven explosion mechanism of core-collapse supernovae (SNe) has experienced remarkable progress over the past decade. First self-consistent, first-principle models have shown successful explosions in 3D, and even failed cases may be cured by moderate changes of the microphysics inside the neutron star (NS), better grid resolution, or more detailed progenitor conditions at the onset of core collapse, in particular large-scale perturbations in the convective Si and O burning shells. 3D simulations have also achieved to follow neutrino-driven explosions continuously from the initiation of the blast wave, through the shock breakout from the progenitor surface, into the radioactively powered evolution of the SN, and towards the free expansion phase of the emerging remnant. Here we present results from such simulations, which form the basis for direct comparisons with observations of SNe and SN remnants in order to derive constraints on the still disputed explosion mechanism. It is shown that predictions based on hydrodynamic instabilities and mixing processes associated with neutrino-driven explosions yield good agreement with measured NS kicks, light-curve properties of SN 1987A and asymmetries of iron and 44Ti distributions observed in SN 1987A and Cassiopeia A.

scholarly journals The bubble-like interior of the core-collapse supernova remnant Cassiopeia A

Science ◽  
2015 ◽  
Vol 347 (6221) ◽  
pp. 526-530 ◽  
Author(s):  
D. Milisavljevic ◽  
R. A. Fesen
Keyword(s):  
Supernova Remnant ◽  
Core Collapse ◽  
Cassiopeia A ◽  
Core Collapse Supernova ◽  
The Core

scholarly journals Cassiopeia A – the Youngest Known Galactic Supernova Remnant

1971 ◽  
Vol 46 ◽  
pp. 263-267
Author(s):  
Sidney van den Bergh
Keyword(s):  
Proper Motion ◽  
Fast Moving ◽  
Supernova Remnant ◽  
Cassiopeia A ◽  
Cas A

Proper motion observations show that the explosion of the Cas A supernova took place in AD 1667 ± 8 (me). Individual moving knots have lifetimes ~ 10 yr. In these fast-moving knots oxygen and argon are overabundant by a factor of at least seventy with respect to hydrogen and nitrogen. Nitrogen is found to be overabundant in quasi-stationary flocculi. This suggests that these flocculi were formed from material that was ejected from the outer layers of the pre-supernova before its explosion in AD 1667.

scholarly journals Light-Echo Spectrum Reveals the Type of Tycho Brahe's 1572 Supernova

2011 ◽  
Vol 7 (S281) ◽  
pp. 335-336
Author(s):  
T. Usuda ◽  
O. Krause ◽  
M. Tanaka ◽  
T. Hattori ◽  
M. Goto ◽  
...  
Keyword(s):  
Supernova Remnants ◽  
Three Dimensional ◽  
Supernova Explosion ◽  
Cassiopeia A ◽  
Type Ia ◽  
Light Echoes ◽  
Explosion Mechanism ◽  
Cas A ◽  
Ia Supernovae ◽  
Insight Into

AbstractWe successfully obtained the first optical spectra of the faint light echoes around Cassiopeia A and Tycho Brahe's supernova remnants (SNRs) with FOCAS and the Subaru Telescope. We conclude that Cas A and Tycho's SN 1572 belong to the Type IIb and normal Type Ia supernovae, respectively. Light echo spectra are important in order to obtain further insight into the supernova explosion mechanism of Tycho's SN 1572: how the Type Ia explosion actually proceeds, and whether accretion occurs from a companion or by the merging of two white dwarfs. The proximity of the SN 1572 remnant has allowed detailed studies, such as the possible identification of the binary companion, and provides a unique opportunity to test theories of the explosion mechanism and the nature of the progenitor. Future light-echo spectra, obtained in different spatial directions of SN 1572, will enable to construct a three-dimensional spectroscopic view of the explosion.

scholarly journals Near-Infrared Study of Iron Knots in Cassiopeia A Supernova Remnant

2013 ◽  
Vol 9 (S296) ◽  
pp. 368-369
Author(s):  
Yong-Hyun Lee ◽  
Bon-Chul Koo ◽  
Dae-Sik Moon ◽  
Michael G. Burton
Keyword(s):  
Supernova Remnant ◽  
Near Infrared ◽  
Spectral Characteristics ◽  
Principal Component ◽  
Reverse Shock ◽  
Infrared Study ◽  
Cassiopeia A ◽  
Deep Layers ◽  
Nir Emission ◽  
Cas A

AbstractWe present the results of near-infrared (NIR) imaging and spectroscopic observations of the Galactic supernova remnant Cassiopeia A (Cas A). Applying the method of Principal Component Analysis to our broadband NIR spectra, we identify a total of 61 NIR emission knots of Cas A and classify them into three groups of distinct spectral characteristics: Helium-rich, Sulfur-rich, and Iron-rich groups. The first and second groups are of the circumstellar and supernova ejecta origin, respectively. The third group, which has enhanced iron emission, is of particular interests since it shows intermediate characteristics between the former two groups. We suggest that the Iron-rich group is knots of swept-up circumstellar medium around the contact discontinuity in Cas A and/or supernova ejecta from deep layers of its progenitor star which have recently encountered a reverse shock in the remnant.

scholarly journals A Review on Additive Manufacturing Possibilities for Electrical Machines

Energies ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1940
Author(s):  
Muhammad Usman Naseer ◽  
Ants Kallaste ◽  
Bilal Asad ◽  
Toomas Vaimann ◽  
Anton Rassõlkin
Keyword(s):  
Additive Manufacturing ◽  
Large Scale ◽  
Three Dimensional ◽  
Electrical Machines ◽  
Electromagnetic Properties ◽  
Scale Production ◽  
Performance Parameters ◽  
Large Scale Production ◽  
One Step ◽  
Manufacturing Techniques

This paper presents current research trends and prospects of utilizing additive manufacturing (AM) techniques to manufacture electrical machines. Modern-day machine applications require extraordinary performance parameters such as high power-density, integrated functionalities, improved thermal, mechanical & electromagnetic properties. AM offers a higher degree of design flexibility to achieve these performance parameters, which is impossible to realize through conventional manufacturing techniques. AM has a lot to offer in every aspect of machine fabrication, such that from size/weight reduction to the realization of complex geometric designs. However, some practical limitations of existing AM techniques restrict their utilization in large scale production industry. The introduction of three-dimensional asymmetry in machine design is an aspect that can be exploited most with the prevalent level of research in AM. In order to take one step further towards the enablement of large-scale production of AM-built electrical machines, this paper also discusses some machine types which can best utilize existing developments in the field of AM.

scholarly journals Vibration characteristics of triple-gear-rotor system in compressed air energy storage under variable torque load

2021 ◽  
Vol 104 (1) ◽  
pp. 003685042098705
Author(s):  
Xinran Wang ◽  
Yangli Zhu ◽  
Wen Li ◽  
Dongxu Hu ◽  
Xuehui Zhang ◽  
...  
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Element Model ◽  
Rotor System ◽  
Dynamic Responses ◽  
System Response ◽  
Rotating Speed ◽  
Torque Load ◽  
Set Up ◽  
Two Stages

This paper focuses on the effects of the off-design operation of CAES on the dynamic characteristics of the triple-gear-rotor system. A finite element model of the system is set up with unbalanced excitations, torque load excitations, and backlash which lead to variations of tooth contact status. An experiment is carried out to verify the accuracy of the mathematical model. The results show that when the system is subjected to large-scale torque load lifting at a high rotating speed, it has two stages of relatively strong periodicity when the torque load is light, and of chaotic when the torque load is heavy, with the transition between the two states being relatively quick and violent. The analysis of the three-dimensional acceleration spectrum and the meshing force shows that the variation in the meshing state and the fluctuation of the meshing force is the basic reasons for the variation in the system response with the torque load. In addition, the three rotors in the triple-gear-rotor system studied show a strong similarity in the meshing states and meshing force fluctuations, which result in the similarity in the dynamic responses of the three rotors.

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