scholarly journals Historical Remarks on the Spectroscopic Analysis of Planetary Nebulae

2003 ◽  
Vol 209 ◽  
pp. 15-22
Author(s):  
Lawrence H. Aller ◽  
Siek Hyung
Keyword(s):  
Spectroscopic Analysis ◽  
Planetary Nebulae ◽  
Spectroscopic Studies ◽  
Spectral Lines ◽  
Charge Coupled Device ◽  
The 1950S ◽  
Historical Remarks ◽  
Photographic Photometry

To record the spectral lines of stars and nebulae, photographic photometry was routinely used in the early 1900s, to be later replaced by methods employing more advanced detectors. We review the progress of planetary nebular spectroscopic studies, i.e. from the early photographic photometry, through to the 1950s photoelectric scanner observations, and finally to recent charge-coupled-device spectroscopy.

AGN evolution as seen in spectral lines: The case of narrow-line Seyfert 1s

2019 ◽  
Vol 15 (S356) ◽  
pp. 94-94
Author(s):  
Marco Berton
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Spectroscopic Studies ◽  
Spectral Lines ◽  
Narrow Line ◽  
Line Profiles ◽  
Line Shapes ◽  
Fundamental Information ◽  
Line Region ◽  
Gaussian Samples

AbstractLine profiles can provide fundamental information on the physics of active galactic nuclei (AGN). In the case of narrow-line Seyfert 1 galaxies (NLS1s) this is of particular importance since past studies revealed how their permitted line profiles are well reproduced by a Lorentzian function instead of a Gaussian. This has been explained with different properties of the broad-line region (BLR), which may present more pronounced turbulent motions in NLS1s with respect to other AGN. We investigated the line profiles in a recent large NLS1 sample classified using SDSS, and we divided the sources into two subsamples according to their line shapes, Gaussian or Lorentzian. The line profiles seem to separate all the properties of NLS1s. Black hole mass, Eddington ratio, [OIII] luminosity, and Fe II strength are all very different in the Lorentzian and Gaussian samples, as well as their position on the quasar main sequence. We interpret this in terms of evolution within the class of NLS1s. The Lorentzian sources may be the youngest objects, while Gaussian profiles may be typically associated to more evolved objects. Further detailed spectroscopic studies are needed to fully confirm our hypothesis.

scholarly journals Models of Planetary Nebulae: Generalisation of the Multiple Winds Model

1989 ◽  
Vol 131 ◽  
pp. 411-424 ◽  
Author(s):  
F. D. Kahn
Keyword(s):  
Planetary Nebula ◽  
High Speed ◽  
Planetary Nebulae ◽  
Central Star ◽  
Theoretical Description ◽  
Basic Theory ◽  
Spectral Lines ◽  
High Excitation ◽  
General Shape ◽  
Fast Wind

According to the multiple winds model a planetary nebula forms as the result of the interaction of a fast wind from the central star with the superwind that had previously been emitted by the progenitor star. The basic theory which deals with the spherically symmetrical case is briefly summarised. Various improvements are then considered in turn. A better history is clearly needed of the way that the central star becomes hotter, it is unrealistic to make the assumption that the superwind is spherically symmetrical, and finally there are likely to be important instabilities at some of the interfaces in the PN, notably that between the shocked superwind and the HII layer. These changes in the theoretical description produce a better understanding of the conditions in the outer parts of a PN and of the nature of its general shape, and they should lead to an explanation for the occurrence of high speed motions, and of highly ionized species and high excitation spectral lines.

scholarly journals Planetary Nebulae in the Magellanic Clouds

1999 ◽  
Vol 190 ◽  
pp. 332-338 ◽  
Author(s):  
Michael A. Dopita
Keyword(s):  
Hubble Space Telescope ◽  
Morphological Structure ◽  
Planetary Nebulae ◽  
Spectroscopic Studies ◽  
Magellanic Clouds ◽  
Star Formation History ◽  
Formation History ◽  
History Of ◽  
Central Stars ◽  
The Ideal

The proximity, accurately known distance and low line-of-sight reddening give the ideal circumstances to pursue studies of individual stellar populations in the Magellanic Clouds. Here we show how our understanding of the evolution and chemical composition of the planetary nebulae in the Magellanic Clouds has been impacted by imaging and UV spectroscopic studies using the Hubble Space Telescope. Images provide sizes, internal morphological structure, absolute fluxes, and dynamical ages, while spectra allow us to place the central stars accurately on the H-R Diagram, and we can also examine the details of the evolution, of mass- and age- dependent chemical dredge-up processes, and infer the star-formation history of the Magellanic Clouds.

scholarly journals ISO-SWS observations of Planetary Nebulae

1997 ◽  
Vol 180 ◽  
pp. 145-150
Author(s):  
D.A. Beintema
Keyword(s):  
Solid State ◽  
Short Wavelength ◽  
Planetary Nebulae ◽  
Spectral Lines ◽  
Ngc 7027 ◽  
First Results

First results of the ISO1 Short-Wavelength Spectrometer on three bright planetary nebulae NGC 6543, NGC 7027 and NGC 6302 provide a wealth of information on solid-state features and spectral lines. Spectra from 2.4 to 45 μm are presented, at a reduced resolution of about 600.

scholarly journals Spectroscopic studies on the interaction of hypocrellin A with myoglobin

2007 ◽  
Vol 21 (4) ◽  
pp. 235-243 ◽  
Author(s):  
J. H. Zhou ◽  
X. H. Wu ◽  
C. Yang ◽  
X. T. Gu ◽  
L. Zhou ◽  
...  
Keyword(s):  
Binding Sites ◽  
Spectroscopic Analysis ◽  
Spectroscopic Studies ◽  
Interaction Process ◽  
Quenching Mechanism ◽  
Visible Absorption ◽  
Paramagnetic Resonance ◽  
Hypocrellin A ◽  
Uv Visible ◽  
Electron Paramagnetic

Experimental results of UV-visible absorption spectroscopy and fluorescence spectroscopy indicate that hypocrellin A, which has been studied in photodynamic therapy, can interact with the surface of myoglobin through hydrophobic forces, and form a complex. Based on the Stern–Volmer equation, the quenching constants of the process can be calculated to be 4.81×1012L mol−1s−1(t=25°C) and 4.54×1012L mol−1s−1(t=42°C) respectively, and the binding constant is 5.53×104M−1(t=25°C), while the binding sites is 0.94 (t=25°C). In addition, Electron paramagnetic resonance and fluorescence spectroscopic analysis suggests that that the quenching mechanism of the interaction process occurs through the electron transfer between hypocrellin A and myoglobin.

scholarly journals Extragalactic planetary nebulae: Tracers of the chemical evolution of nearby galaxies

2011 ◽  
Vol 7 (S283) ◽  
pp. 251-258 ◽  
Author(s):  
Laura Magrini ◽  
Letizia Stanghellini ◽  
Denise R. Gonçalves
Keyword(s):  
Chemical Evolution ◽  
Stellar Evolution ◽  
Planetary Nebulae ◽  
Spectroscopic Studies ◽  
Disk Galaxies ◽  
Chemical Enrichment ◽  
History Of ◽  
External Galaxies ◽  
Low Metallicity ◽  
Nearby Galaxies

AbstractThe study of the chemical composition of Planetary Nebulae in external galaxies is of paramount importance for the fields of stellar evolution and chemical enrichment history of galaxies. In recent years a number of spectroscopic studies with 6-8m-class telescopes have been devoted to this subject improving our knowledge of, among other, the time-evolution of the radial metallicity gradient in disk galaxies, the chemical evolution of dwarf galaxies, and stellar evolution at low metallicity.

scholarly journals Thermal and spectroscopic studies of polymer protective coatings used in optical fibers technology

2018 ◽  
Vol 72 (2) ◽  
pp. 77
Author(s):  
Małgorzata Gil ◽  
Małgorzata Kuklińska ◽  
Lidia Czyżewska ◽  
Grzegorz Wójcik ◽  
Paweł Mergo
Keyword(s):  
Optical Fibers ◽  
Spectroscopic Analysis ◽  
Protective Coatings ◽  
Spectroscopic Studies ◽  
Mechanical Reliability ◽  
Fiber Technology ◽  
On Line ◽  
Uv Lamps ◽  
Thermal And Spectroscopic Studies

<p>An important factor determining the quality of optical fibers is their mechanical reliability. The control of the mechanical reliability allows define the lifetime of a fiber, which was under the stress during the work. Decisive influences on the mechanical and optical properties of the optical fibers have the protective coatings. Optical fiber technology requires that the coatings were applied on them on-line, directly after they have been drawn. So far, little attention has been paid to optimizing the conditions of coatings curing. In this work, the comparison of a thermoanalytical and spectroscopic analysis of coatings that were cured in an UV oven in which the power of the UV lamps was changed will be shown. As part of the research tasks, completed mechanical strength measurements were made with a silica fiber of 0.125 mm diameter.</p>

scholarly journals Observations of ultraviolet stellar spectra

1970 ◽  
Vol 36 ◽  
pp. 147-162
Author(s):  
R. Wilson
Keyword(s):  
Spectral Resolution ◽  
Photographic Plate ◽  
Spectroscopic Studies ◽  
Ultraviolet Spectrum ◽  
Spectral Lines ◽  
Resolution Limit ◽  
Stellar Spectra ◽  
Stellar Spectroscopy ◽  
Strong Resonance ◽  
The Many

The dividing line between photometry and spectrometry is not always obvious and for the purpose of this review, I will define ultraviolet stellar spectroscopy as observations with sufficient spectral resolution to allow the detection of individual spectral lines and their measurement in terms of wavelength and strength. From an examination of the existing observations this results in a resolution requirement of δλ < 10 Å. Since the best spectral resolution so far obtained is about 1 Å then this places the results to be discussed within the range 1–10 Å. In terms of λ/δλ this corresponds to a range of about 2000–200 and it is important to bear in mind that these represent low resolution spectra. In fact the limit of 200 that I have imposed would rarely be used for spectroscopic studies in ground based observatories where it corresponds, in the notation of the optical astronomer, to a dispersion of about 1000 Å/mm, the resolution limit being set by the photographic plate, typically taken as 20 μ. Hence, even the faintest objects like quasars are usually studied with a dispersion of a few hundred Å mm−1. The fact that such a resolution can be included here is an indication of the exceptionally strong resonance lines which occur in the ultraviolet and which can be detected with such a resolution. On the other hand, the richness of the ultraviolet spectrum is making and will continue to make, demands on improved resolution in order to separate the many features. The best achieved resolution of about 1 Å goes only part-way to solving this problem.

scholarly journals Pulsations in O Stars

1999 ◽  
Vol 169 ◽  
pp. 305-311
Author(s):  
Hubertus F. Henrichs
Keyword(s):  
Line Profile ◽  
Spectroscopic Studies ◽  
Spectral Lines ◽  
Time Dependent ◽  
Current Status ◽  
Radial Pulsation ◽  
Major Difficulty ◽  
Critical Attitude ◽  
Quantitative Results

AbstractO stars are located in a domain of the HRD where nonradial pulsations are expected. Photometric surveys did not reveal pulsating O stars, showing that the amplitudes must be very small. Intensive spectroscopic studies yielded pulsation modes for very few O stars only, although many are line-profile variables. Wind contamination of many spectral lines is a major difficulty. Future concentrated spectroscopic efforts will undoubtedly increase the number of pulsating O stars.The current status of our knowledge of pulsations in these stars is reviewed. From one specific example a critical attitude emerges towards the quantitative results reached so far. We also address the question whether non-radial pulsation can be the cause of the non-spherical time-dependent winds of these stars.

SPECTROSCOPIC STUDIES ON Ag/PVA NANOCOMPOSITE THIN FILMS PREPARED BY THERMAL ANNEALING PROCESS

2011 ◽  
Vol 10 (03) ◽  
pp. 427-432 ◽  
Author(s):  
RAJIB SAIKIA ◽  
P. GOGOI ◽  
P. K. BARUA ◽  
PRANAYEE DATTA
Keyword(s):  
Thin Films ◽  
Thermal Annealing ◽  
Spectroscopic Analysis ◽  
Spectroscopic Studies ◽  
Annealing Process ◽  
Localized Surface Plasmon ◽  
Particle Sizes ◽  
Spectral Position ◽  
Nanocomposite Thin Films ◽  
Thermal Annealing Process

In this paper, a systematic spectroscopic analysis on silver–polyvinyl alcohol ( Ag /PVA) nanocomposite thin films is reported. Ag /PVA nanocomposite thin films fabricated by thermal annealing process are shown to exhibit a strong localized surface plasmon resonance (LSPR) at wavelength around 400 nm. The effects of different fabricating parameters on the absorbance and spectral position of LSPR are also investigated. The particle sizes calculated from Mie light scattering theory are found to agree with the values obtained from SEM characterization.

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