45. Spectral Classifications and Multi-Band Colour Indices

1973 ◽  
Vol 15 (1) ◽  
pp. 697-716 ◽  
Author(s):  
B. E. Westerlund
Keyword(s):  
Spectral Lines ◽  
General Tendency ◽  
Spectral Classification ◽  
Visual Classification ◽  
The Past ◽  
Objective Prism ◽  
Colour Indices ◽  
Multi Band

During the past three years there has been much activity in the field of spectral classification by photographic and photoelectric techniques. The general tendency of the spectral classification has been one of refinement of the criteria applied in visual classification, the more frequent appearance of criteria based on equivalent widths measured in higher-dispersion spectra and the use of narrowband photometry on individual often rather weak spectral lines. In the area of objective prism classification important extensive programmes are under way at many observatories. Here, the increased interest in and importance of automation of data available on spectral plates is perhaps most obvious.

scholarly journals The Spectral Classification of Stars over the last 200, 100, 75 years and in the future

2018 ◽  
Vol 13 (S349) ◽  
pp. 489-493
Author(s):  
Christopher J. Corbally ◽  
Richard O. Gray
Keyword(s):  
Reggio Emilia ◽  
Spectral Classification ◽  
Stellar Spectra ◽  
Historical View ◽  
The Future ◽  
Colour Indices ◽  
Multi Band

AbstractThis year 2018 has great historical and current significance for stellar spectral classification. Two hundred years ago in Reggio Emilia, Italy, was born Angelo Secchi, a pioneer of observing and classifying the spectra of stars. At the beginning of the IAU, almost a hundred years ago, one of its original Commissions was entitled the Spectral Classification of Stars, from which was generated Commission 45, Spectral Classification and Multi-band Colour Indices. And seventy-five years ago, was published the system-changing MKK, An Atlas of Stellar Spectra. Through this necessarily brief, historical view we shall recall how spectral classification, supported internationally by the IAU, continually updated its techniques, while remaining anchored to standards. This has ensured that the MK classification process stays very relevant to the initial characterizing of stars in the 21st century era of large spectral surveys.

scholarly journals Advantages and Limitations of Quantitative Spectral Classification

1973 ◽  
Vol 50 ◽  
pp. 60-61
Author(s):  
F. Spite
Keyword(s):  
Spectral Lines ◽  
Spectral Classification ◽  
Visual Classification

The measurements of spectral lines of moderate dispersion slit spectrograms for F, G and K type stars give a large quantity of information. The measurements are time-consuming in comparison with visual classification, but the use of digitized microphotometers reduces the task, and the method is now promising. The interpretation of the measurements raises some problems, which are briefly discussed.

Novae in the Magellanic Clouds

1979 ◽  
Vol 46 ◽  
pp. 96-101
Author(s):  
J.A. Graham
Keyword(s):  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
University Of Michigan ◽  
The Past ◽  
Spectroscopic Information ◽  
Objective Prism ◽  
The University ◽  
Small Cloud ◽  
Low Dispersion

During the past several years, a systematic search for novae in the Magellanic Clouds has been carried out at Cerro Tololo Inter-American Observatory. The Curtis Schmidt telescope, on loan to CTIO from the University of Michigan is used to obtain plates every two weeks during the observing season. An objective prism is used on the telescope. This provides additional low-dispersion spectroscopic information when a nova is discovered. The plates cover an area of 5°x5°. One plate is sufficient to cover the Small Magellanic Cloud and four are taken of the Large Magellanic Cloud with an overlap so that the central bar is included on each plate. The methods used in the search have been described by Graham and Araya (1971). In the CTIO survey, 8 novae have been discovered in the Large Cloud but none in the Small Cloud. The survey was not carried out in 1974 or 1976. During 1974, one nova was discovered in the Small Cloud by MacConnell and Sanduleak (1974).

The Development of the Soil Profile in North Wales as Illustrated by the Character of the Clay Fraction

1930 ◽  
Vol 20 (4) ◽  
pp. 618-639 ◽  
Author(s):  
G. W. Robinson
Keyword(s):  
Ferric Oxide ◽  
Soil Profile ◽  
Clay Fraction ◽  
General Tendency ◽  
Surface Layers ◽  
Molecular Ratio ◽  
The Past ◽  
North Wales

1. The changes in composition of the clay fraction in different horizons of some typical North Welsh profiles have been studied.2. The changes in the molecular ratio of silica to sesquioxides (SiO2/Al2O3+ Fe2O3) throughout a soil profile afford an indication of the nature of the eluviation which has affected the mineral portion of the soil.3. The data for North Welsh soils indicate a general tendency to enrichment of the lower layers in sesquioxides, particularly ferric oxide, at the expense of the surface layers.4. The silica-sesquioxide ratio of the clay fraction is an important aid to series definition.5. The soils of North Wales, particularly in the uplands, have probably been subjected to considerable erosion in the past. The profiles are therefore considered to be more or less truncated.

An Extended Scheme of Spectral Classification for Objective Prism Spectra

1994 ◽  
pp. 255-257 ◽  
Author(s):  
P. Hantzios ◽  
E. Kontizas ◽  
F. Pasian ◽  
A. Dapergolas ◽  
M. Kontizas ◽  
...  
Keyword(s):  
Spectral Classification ◽  
Objective Prism

scholarly journals Some Lessons from the Past and Thoughts on the Future of Spectral Classification

1979 ◽  
Vol 47 ◽  
pp. 337-346 ◽  
Author(s):  
N. R. Walborn
Keyword(s):  
Magellanic Clouds ◽  
External Information ◽  
Spectral Classification ◽  
New Techniques ◽  
The Past ◽  
Spectroscopic Examination ◽  
The Galaxy ◽  
The Many ◽  
Large Telescopes ◽  
New Phenomena

AbstractThe importance of maintaining the greatest possible independence of spectral classification from theoretical or other external information is emphasized anew, with reference to some historical discussions now seen with the benefit of hindsight. This ideal requirement applies equally to the development and to the application of a classification system, although in practice some well-established information may guide one’s intuition in the initial hypothetical formulation. The fundamental position of this principle in the MK approach to classification is a major reason for the value of its spectral types, and for its continuing success in uncovering new phenomena. The ability of a particular technique to produce interesting or useful results is surely the most significant criterion of its value, and from this viewpoint it appears that new techniques and methods will complement rather than replace traditional spectral classification. Finally, the unique importance at this time of applying both new and traditional methods to spectral classification in the Magellanic Clouds is stressed; they provide the only current opportunity for detailed spectroscopic examination of numerous stars in external systems. It is essential that large telescopes be utilized for this work so that the best attainable observational quality may be maintained, and the many fascinating phenomena revealed by spectral classification in the Galaxy can be comparatively investigated to the maximum extent praticable in the Magellanic Clouds

scholarly journals Contributions and Prospects for Spectral Classification of Stars with Objective Prism Techniques

1979 ◽  
Vol 47 ◽  
pp. 127-136
Author(s):  
E. K. Kharadze
Keyword(s):  
Galactic Structure ◽  
Spectral Classification ◽  
Missing Mass ◽  
Mass Problem ◽  
Important Stage ◽  
Objective Prism ◽  
Low Dispersion

The following topics will be discussed: a) A few historical comments; b) MK classification - the most important stage of classification work; c) Recently revealed peculiarity features and the problem of further differentiation of the classification scale; d) Classification work in the USSR; e) The role of classification results with respect to galactic structure studies; f) Low dispersion spectra and faint M-type stars and the missing mass problem; g) Extraterrestrial spectral observations: new promising means for research.

scholarly journals Application of convolutional neural networks for stellar spectral classification

2019 ◽  
Vol 491 (2) ◽  
pp. 2280-2300 ◽  
Author(s):  
Kaushal Sharma ◽  
Ajit Kembhavi ◽  
Aniruddha Kembhavi ◽  
T Sivarani ◽  
Sheelu Abraham ◽  
...  
Keyword(s):  
Neural Networks ◽  
Deep Learning ◽  
Convolutional Neural Networks ◽  
Spectral Classification ◽  
Stellar Spectra ◽  
The Past ◽  
Training Samples ◽  
Optical Region ◽  
Spectral Libraries ◽  
Improved Accuracy

ABSTRACT Due to the ever-expanding volume of observed spectroscopic data from surveys such as SDSS and LAMOST, it has become important to apply artificial intelligence (AI) techniques for analysing stellar spectra to solve spectral classification and regression problems like the determination of stellar atmospheric parameters Teff, $\rm {\log g}$, and [Fe/H]. We propose an automated approach for the classification of stellar spectra in the optical region using convolutional neural networks (CNNs). Traditional machine learning (ML) methods with ‘shallow’ architecture (usually up to two hidden layers) have been trained for these purposes in the past. However, deep learning methods with a larger number of hidden layers allow the use of finer details in the spectrum which results in improved accuracy and better generalization. Studying finer spectral signatures also enables us to determine accurate differential stellar parameters and find rare objects. We examine various machine and deep learning algorithms like artificial neural networks, Random Forest, and CNN to classify stellar spectra using the Jacoby Atlas, ELODIE, and MILES spectral libraries as training samples. We test the performance of the trained networks on the Indo-U.S. Library of Coudé Feed Stellar Spectra (CFLIB). We show that using CNNs, we are able to lower the error up to 1.23 spectral subclasses as compared to that of two subclasses achieved in the past studies with ML approach. We further apply the trained model to classify stellar spectra retrieved from the SDSS data base with SNR > 20.

scholarly journals The Hamburg All-Sky Bright QSO Surveys

2002 ◽  
Vol 184 ◽  
pp. 33-42
Author(s):  
Dieter Reimers ◽  
Lutz Wisotzki
Keyword(s):  
The Past ◽  
Selection Strategies ◽  
Observational Database ◽  
Objective Prism

AbstractOver the past decade, our team has pursued a quest to search for the optically brightest quasars in the entire extragalactic sky, by means of automated quasar selection using digitised objective prism spectra. We give a brief overview over the observational database and selection strategies and present some of the major survey highlights

Properties of Magnetic Features from the Analysis of Near-Infrared Spectral Lines

1994 ◽  
Vol 154 ◽  
pp. 393-405
Author(s):  
Sami K. Solanki
Keyword(s):  
Near Infrared ◽  
Velocity Structure ◽  
Spectral Lines ◽  
The Past ◽  
Diagnostic Potential ◽  
Theoretical Predictions ◽  
Infrared Spectral ◽  
Magnetic Features

An overview is given of the structure and the physics of magnetic features in solar plages, as derived from observations of near-infrared lines. First, the diagnostic potential of near-infrared lines is compared with that of lines in the visible and at 12 μm. Then, the results on the magnetic and velocity structure of magnetic features obtained from 1.5 μm lines are described, discussed and compared with results of observations in the visible and with theoretical predictions. Finally, the past and present achievements of near-infrared investigations of Zeeman-split lines are summarized.

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