scholarly journals Simulations and Modeling of Intermediate Luminosity Optical Transients and Supernova Impostors

2018 ◽  
Author(s):  
Amit Kashi
Keyword(s):  
High Energy ◽  
Gravitational Energy ◽  
Time Diagram ◽  
High Energy Part ◽  
Classical Novae ◽  
Energy Part ◽  
Optical Transients ◽  
Hydrodynamical Simulations ◽  
Simulations And Modeling ◽  
Optical Transient

Intermediate-luminosity-optical-transients (ILOTs) are stellar outbursts with luminosity between those of classical novae and supernovae. They are divided into a number of sub-groups depending on the erupting progenitor and the properties of the eruption. Many of the ILOTs sit 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. We also stand on similarities between Planetary Nebulae (PN) to ILOTs, and suggest that some PNe were formed in an ILOT event. The high energy part of the OTS is reserved to the supernova impostors -- giant eruption of very massive stars. We show results of 3D hydrodynamical simulations of supernova impostors that expose the mechanism behind these giant eruptions, and present new models for recent ILOTs. We stand on the connection between different kinds of ILOTs, and suggest that they are powered by a similar source of energy -- gravitational energy released by mass transfer.

scholarly journals Simulations and Modeling of Intermediate Luminosity Optical Transients and Supernova Impostors

Galaxies ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 82 ◽  
Author(s):  
Amit Kashi
Keyword(s):  
Central Star ◽  
High Energy ◽  
Gravitational Energy ◽  
High Energy Part ◽  
Classical Novae ◽  
Energy Part ◽  
Optical Transients ◽  
Hydrodynamical Simulations ◽  
Simulations And Modeling ◽  
Optical Transient

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.

Compact back-scattered electrons' energy analyzer for standard SEM

1994 ◽  
Vol 52 ◽  
pp. 488-489
Author(s):  
S. Likharev ◽  
A. Kramarenko ◽  
V. Vybornov
Keyword(s):  
Depth Resolution ◽  
High Energy ◽  
Primary Beam ◽  
Layer By Layer ◽  
Energy Analyzer ◽  
High Energy Part ◽  
Small Window ◽  
Energy Part ◽  
Wide Range ◽  
High Voltage Supply

At present time the interest is growing considerably for theoretical and experimental analysis of back-scattered electrons (BSE) energy spectra. It was discovered that a special angle and energy nitration of BSE flow could be used for increasing a spatial resolution of BSE mode, sample topography investigations and for layer-by layer visualizing of a depth structure. In the last case it was shown theoretically that in order to obtain suitable depth resolution it is necessary to select a part of BSE flow with the directions of velocities close to inverse to the primary beam and energies within a small window in the high-energy part of the whole spectrum.A wide range of such devices has been developed earlier, but all of them have considerable demerit: they can hardly be used with a standard SEM due to the necessity of sufficient SEM modifications like installation of large accessories in or out SEM chamber, mounting of specialized detector systems, input wires for high voltage supply, screening a primary beam from additional electromagnetic field, etc. In this report we present a new scheme of a compact BSE energy analyzer that is free of imperfections mentioned above.

scholarly journals Multiple retrograde substructures in the Galactic halo: A shattered view of Galactic history

2019 ◽  
Vol 631 ◽  
pp. L9 ◽  
Author(s):  
Helmer H. Koppelman ◽  
Amina Helmi ◽  
Davide Massari ◽  
Adrian M. Price-Whelan ◽  
Tjitske K. Starkenburg
Keyword(s):  
High Resolution ◽  
Clustering Algorithm ◽  
Galactic Halo ◽  
High Energy ◽  
Galaxy Mergers ◽  
Chemical Abundance ◽  
Distinct Structure ◽  
Halo Stars ◽  
Energy Part ◽  
Hydrodynamical Simulations

Aims. Several kinematic and chemical substructures have been recently found amongst Milky Way halo stars with retrograde motions. It is currently unclear how these various structures are related to each other. This Letter aims to shed light on this issue. Methods. We explore the retrograde halo with an augmented version of the Gaia DR2 RVS sample, extended with data from three large spectroscopic surveys, namely RAVE, APOGEE, and LAMOST. In this dataset, we identify several structures using the HDBSCAN clustering algorithm. We discuss their properties and possible links using all the available chemical and dynamical information. Results. In concordance with previous work, we find that stars with [Fe/H] < −1 have more retrograde motions than those with [Fe/H] > −1. The retrograde halo contains a mixture of debris from objects like Gaia-Enceladus, Sequoia, and even the chemically defined thick disc. We find that the Sequoia has a smaller range in orbital energies than previously suggested and is confined to high energy. Sequoia could be a small galaxy in itself, but since it overlaps both in integrals-of-motion space and chemical abundance space with the less bound debris of Gaia-Enceladus, its nature cannot yet be fully settled. In the low-energy part of the halo, we find evidence for at least one more distinct structure: Thamnos. Stars in Thamnos are on low-inclination, mildly eccentric retrograde orbits, moving at vϕ ≈ −150 km s−1, and are chemically distinct from the other structures. Conclusions. Even with the excellent Gaia DR2 data, piecing together all the fragments found in the retrograde halo remains challenging. At this point, we are very much in need of large datasets with high-quality high-resolution spectra and tailored high-resolution hydrodynamical simulations of galaxy mergers.

scholarly journals The Zadko Telescope: A Southern Hemisphere Telescope for Optical Transient Searches, Multi-Messenger Astronomy and Education

2010 ◽  
Vol 27 (3) ◽  
pp. 331-339 ◽  
Author(s):  
D. M. Coward ◽  
M. Todd ◽  
T. P. Vaalsta ◽  
M. Laas-Bourez ◽  
A. Klotz ◽  
...  
Keyword(s):  
East Coast ◽  
Gamma Ray ◽  
High Energy ◽  
Pilot Program ◽  
Public Outreach ◽  
Southern Latitude ◽  
Optical Transients ◽  
Robotic Telescope ◽  
Optical Transient ◽  
Potential Tool

AbstractThe new 1 m f/4 fast-slew Zadko Telescope was installed in June 2008 about 70 km north of Perth, Western Australia. It is the only metre-class optical facility at this southern latitude between the east coast of Australia and South Africa, and can rapidly image optical transients at a longitude not monitored by other similar facilities. We report on first imaging tests of a pilot program of minor planet searches, and Target of Opportunity observations triggered by the Swift satellite. In 12 months, 6 gamma-ray burst afterglows were detected, with estimated magnitudes; two of them, GRB 090205 (z = 4.65) and GRB 090516 (z = 4.11), are among the most distant optical transients imaged by an Australian telescope. Many asteroids were observed in a systematic 3-month search. In September 2009, an automatic telescope control system was installed, which will be used to link the facility to a global robotic telescope network; future targets will include fast optical transients triggered by high-energy satellites, radio transient detections, and LIGO gravitational wave candidate events. We also outline the importance of the facility as a potential tool for education, training, and public outreach.

scholarly journals Transients from the Cataclysmic Deaths of Cataclysmic Variables

2021 ◽  
Vol 923 (1) ◽  
pp. 100
Author(s):  
Brian D. Metzger ◽  
Yossef Zenati ◽  
Laura Chomiuk ◽  
Ken J. Shen ◽  
Jay Strader
Keyword(s):  
Large Fraction ◽  
Cataclysmic Variables ◽  
Mass Star ◽  
Tidal Disruption ◽  
Classical Novae ◽  
Hydrogen Recombination ◽  
Low Mass ◽  
Hydrodynamical Simulations ◽  
Stellar Mergers ◽  
Optical Transient

Abstract We explore the observational appearance of the merger of a low-mass star with a white dwarf (WD) binary companion. We are motivated by recent work finding that multiple tensions between the observed properties of cataclysmic variables (CVs) and standard evolution models are resolved if a large fraction of CV binaries merge as a result of unstable mass transfer. Tidal disruption of the secondary forms a geometrically thick disk around the WD, which subsequently accretes at highly super-Eddington rates. Analytic estimates and numerical hydrodynamical simulations reveal that outflows from the accretion flow unbind a large fraction ≳90% of the secondary at velocities ∼500–1000 km s−1 within days of the merger. Hydrogen recombination in the expanding ejecta powers optical transient emission lasting about a month with a luminosity ≳1038 erg s−1, similar to slow classical novae and luminous red novae from ordinary stellar mergers. Over longer timescales the mass accreted by the WD undergoes hydrogen shell burning, inflating the remnant into a giant of luminosity ∼300–5000 L ⊙, effective temperature T eff ≈ 3000 K, and lifetime ∼104–105 yr. We predict that ∼103–104 Milky Way giants are CV merger products, potentially distinguishable by atypical surface abundances. We explore whether any Galactic historical slow classical novae are masquerading CV mergers by identifying four such post-nova systems with potential giant counterparts for which a CV merger origin cannot be ruled out. We address whether the historical transient CK Vul and its gaseous/dusty nebula resulted from a CV merger.

Spectrally Resolved Cathodoluminescence (SRCL) of Hydrothermal ZnO crystals

2005 ◽  
Vol 878 ◽  
Author(s):  
J. Mass ◽  
M. Avella ◽  
J. Jiménez ◽  
M. Callahan ◽  
E. Grant ◽  
...  
Keyword(s):  
High Energy ◽  
Luminescence Spectra ◽  
Growth Sector ◽  
High Energy Part ◽  
Spectral Signatures ◽  
Energy Part ◽  
Good Crystalline Quality ◽  
Recombination Centers ◽  
Band Tailing ◽  
Spectrally Resolved

AbstractLarge hydrothermal ZnO crystals were grown using 3N NaOH, 1N KOH and 0.5N Li2CO3mineralizer. The crystals were studied by cathodoluminescence (CL), showing a good crystalline quality. Different growth regions were identified by CL imaging. These regions were characterized by their corresponding luminescence spectra, showing that the incorporation of impurities and non radiative recombination centers depend on the growth sector. The surface is shown to introduce band tailing modifying the high energy part of the spectrum. The main spectral signatures of each sector are discussed.

On the High Energy Part of theK40β-Spectrum

1948 ◽  
Vol 74 (1) ◽  
pp. 102-103 ◽  
Author(s):  
S. Franchetti ◽  
M. Giovanozzi
Keyword(s):  
High Energy ◽  
High Energy Part ◽  
Energy Part

scholarly journals Новые линии в спектрах ИК люминесценции высокого разрешения монокристаллов SiC политипов 4H и 6H

2020 ◽  
Vol 128 (9) ◽  
pp. 1264
Author(s):  
К.Н. Болдырев ◽  
Д.Д. Гуценко ◽  
С.А. Климин ◽  
Н.Н. Новикова ◽  
Б.Н. Маврин ◽  
...  
Keyword(s):  
High Resolution ◽  
Low Temperature ◽  
Single Crystals ◽  
Absorption Spectra ◽  
High Energy ◽  
High Quality ◽  
High Energy Part ◽  
Infrared Luminescence ◽  
Energy Part ◽  
First Time

Low-temperature infrared luminescence and high-resolution absorption spectra of undoped high-quality SiC single crystals of hexagonal modifications 4H and 6H were investigated. Narrow lines with widths less than 0.2 cm^(-1) were detected, several of which were observed for the first time. It was found that some of the lines in the 4H and 6H modifications have a similar structure, however, the lines in SiC-4H are shifted to the high-energy part of the spectrum by ~ 180 cm^(-1). For the most intense quartet in the region of 1.3 μm, the energy scheme of the levels for both 4H and 6H modifications were constructed.

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