scholarly journals Spectral Classification of Early Type Stars from the Low Dispersion Ultraviolet Spectra

1977 ◽  
Vol 4 (2) ◽  
pp. 289-301 ◽  
Author(s):  
K. Nandy
Keyword(s):  
Spectral Type ◽  
Main Sequence ◽  
Photometric System ◽  
Spectral Classification ◽  
Early Type ◽  
Ultraviolet Spectra ◽  
Early Type Stars ◽  
Natural Groups ◽  
Low Dispersion

The methods of spectral classification from the low dispersion ultraviolet spectra obtained with the S2/68 experiment in the TD1 satellite have been described. The bright stars, the spectra of which are photometrically accurate, can be divided into natural groups according to the spectral appearance of the features. These features vary in strength with spectral type and luminosity, and enable separation between main sequence and luminous stars. The limits for these stars areat BO toat AO. For fainter stars the spectral data have been combined to obtain narrow band magnitudes at several wavelengths. These photometric bands have an effective width of 100 A. An ultraviolet photometric system which enables determinations of spectral type and luminosity of early type stars is described and the results for about 3000 stars is presented. The photometric system considered here consists of the ultraviolet colour indices (m2740−V,) (m2190−V) and (m1490−V).

scholarly journals Two Dimensional Spectral Classification of Early Type Stars by Narrow Band Photometry

1979 ◽  
Vol 47 ◽  
pp. 507-518
Author(s):  
M. Gerbaldi ◽  
N. Morguleff
Keyword(s):  
Narrow Band ◽  
Statistical Technique ◽  
Photometric System ◽  
Two Dimensional ◽  
Spectral Classification ◽  
Early Type ◽  
Early Type Stars ◽  
Independent Parameters ◽  
Best Parameters

AbstractSpectrophotometry data of 775 early type stars in a narrow band photometric system are analyzed, looking for the best parameters for a two dimensional spectral classification in the spectral region 3575 Å - 6000 Å. A correlation is established with the MK classification. The statistical technique of Principal Componant Analysis is applied to determine the number of linearly independent parameters among the data.

Two Dimensional Spectral Classification of Early Type Stars by Low Dispersion Spectrophotometry

1973 ◽  
Vol 50 ◽  
pp. 258-266
Author(s):  
A. Gutiérrez-Moreno ◽  
H. Moreno
Keyword(s):  
Classification Scheme ◽  
Two Dimensional ◽  
Spectral Classification ◽  
Early Type ◽  
Luminosity Class ◽  
Spectrophotometric Data ◽  
Early Type Stars ◽  
Low Dispersion ◽  
Best Parameters

Spectrophotometric data of early type stars (spectral intensity distributions from 3100 to 6000 Å and equivalent widths of Hβ, Hγ and Hδ) have been analysed, looking for the best parameters for a two dimensional spectral classification. It was found that the best correlation with MK classification is given by the equivalent width of Hβ and the Balmer discontinuity.The classification scheme is well defined for stars from B0 to A1 of luminosity classes V to III. No stars of luminosity class II were observed. Luminosity class I is clearly separated from the less luminous stars, but the number of supergiants observed is too small to give a clear separation of spectral types.

scholarly journals UV Spectral Classification of B Stars

1985 ◽  
Vol 111 ◽  
pp. 411-413
Author(s):  
Janet Rountree ◽  
George Sonneborn ◽  
Robert J. Panek
Keyword(s):  
Classification System ◽  
Classification Criteria ◽  
High Dispersion ◽  
Spectral Classification ◽  
Early Type ◽  
B Stars ◽  
Dimensional Classification ◽  
Early Type Stars ◽  
Comprehensive Classification

Previous studies of ultraviolet spectral classification have been insufficient to establish a comprehensive classification system for ultraviolet spectra of early-type stars because of inadequate spectral resolution. We have initiated a new study of ultraviolet spectral classification of B stars using high-dispersion IUE archival data. High-dispersion SWP spectra of MK standards and other B stars are retrieved from the IUE archives and numerically degraded to a uniform resolution of 0.25 or 0.50 Å. The spectra (in the form of plots or photowrites) are then visually examined with the aim of setting up a two-dimensional classification matrix. We follow the method used to create the MK classification system for visual spectra. The purpose of this work is to examine the applicability of the MK system (and in particular, the set of standard stars) in the ultraviolet, and to establish classification criteria in this spectral region.

scholarly journals Classification of Early Type Stars on the Dominion Astrophysical Observatory Photometric System

1973 ◽  
Vol 50 ◽  
pp. 152-161
Author(s):  
S. C. Morris ◽  
G. Hill ◽  
G. A. H. Walker ◽  
H. I. B. Thompson
Keyword(s):  
Classification Method ◽  
Photometric System ◽  
Early Type ◽  
Balmer Series ◽  
Early Type Stars ◽  
Independent Parameters

A classification method has been developed for early–type stars observed on the Dominion Astrophysical Observatory photometric system. Two reddening-independent parameters, Q(35) and Q(38), are used. Q(35) is a measure of the Balmer discontinuity, while Q(38) is a measure of the strength of the upper members of the Balmer series. A preliminary calibration of Q(35) and Q(38) in terms of spectral types and luminosity classes is given, and applications to several groups of stars are shown.

scholarly journals Quantitative Spectral Classification of Be Stars on Low Dispersion Spectra

1979 ◽  
Vol 47 ◽  
pp. 247-258 ◽  
Author(s):  
Lucienne Divan
Keyword(s):  
Spectral Type ◽  
Central Star ◽  
Low Pressure ◽  
Be Stars ◽  
Spectral Classification ◽  
Luminosity Class ◽  
Low Dispersion ◽  
The Continuum

AbstractTwo separate Balmer jumps are observed in some Be stars. The first one, in absorption and unchanging, is attributed to the central star and gives its spectral type and luminosity class in the λ,D system. The second one, occuring at shorter wavelengths, either in absorption or in emission, originates in layers at a low pressure. It is shown that these layers modify the colors of the central star on both sides of the Balmer jump and that they are not optically thin even in the continuum.

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