scholarly journals The Estimation of the Electron Density ne with a Narrow-Band Photometric System Calibrated by Model Atmospheres

1985 ◽  
Vol 111 ◽  
pp. 557-560
Author(s):  
M. Gerbaldi ◽  
N. Morguleff
Keyword(s):  
Electron Density ◽  
Narrow Band ◽  
Photometric System ◽  
Early Type ◽  
Peculiar Stars ◽  
Early Type Stars ◽  
Definition Of

A spectrophotometer was originally designed by Barbier (1960) for the study of early-type stars. The band passes were chosen to measure the features of the hydrogen spectrum. To the first definition of the system (Barbier and Morguleff 1964), two more bands were added, specifically devoted to the peculiar stars of type Ap and Am (Gerbaldi 1972). The interpretation of these observations has already been given separately. We will concentrate here on the calibration of this spectrophotometric system in terms of Teff, log g and electron density ne.

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.

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.

Δa Photometric Survey of the Small Magellanic Cloud

2017 ◽  
Vol 14 (S339) ◽  
pp. 349-352
Author(s):  
M. Zejda ◽  
E. Paunzen ◽  
Z. Mikulášek
Keyword(s):  
Magnetic Fields ◽  
Narrow Band ◽  
Magellanic Cloud ◽  
Photometric System ◽  
Small Magellanic Cloud ◽  
Chemically Peculiar ◽  
Peculiar Stars ◽  
First Results ◽  
Bona Fide

AbstractThe narrow-band Δa photometric system measures the flux depression at λ5200 Å by comparing the flux at the band centre to adjacent regions. It has been shown that virtually all peculiar stars with magnetic fields (mCPs) have significant positive Δa values (of up to +100 mmag), whereas Be/Ae/B[e] and metal weak stars (including lambda Bootis types) exhibit significant negative values of Δa. By using this photometric system we are therefore able to detect chemically peculiar (CP), emission types and metal-weak stars in an efficient way. The poster presented the first results of our survey of the Small Magellanic Cloud. In the selected field we found only 0.5 % of bona fide CP stars against 15 % in our Galaxy.

scholarly journals Ultraviolet Spectrophotometry of Early-Type Stars

1976 ◽  
Vol 72 ◽  
pp. 161-165 ◽  
Author(s):  
K. Nandy ◽  
G. I. Thompson ◽  
C. M. Humphries
Keyword(s):  
Classification Scheme ◽  
Narrow Band ◽  
Two Dimensional ◽  
Early Type ◽  
Ultraviolet Spectrophotometry ◽  
B Stars ◽  
Preliminary Results ◽  
Ultraviolet Spectra ◽  
Dimensional Classification ◽  
Early Type Stars

The ultraviolet spectra of B stars obtained with the sky scan telescope in the TD1 satellite have been used to obtain narrow-band magnitudes at several wavelengths. These photometric bands have an effective half-width of 100 Å. We have proposed a two-dimensional classification scheme based on ultraviolet colours, and some preliminary results are presented.

scholarly journals Some Physical Parameters and UVBY β Photometry of Trapezium Type Multiple Systems

1995 ◽  
Vol 166 ◽  
pp. 391-391
Author(s):  
G.N. Salukvadze ◽  
G. Sh. Javakhishvili
Keyword(s):  
Photon Counting ◽  
Physical Parameters ◽  
Photometric System ◽  
Early Type ◽  
Multiple Systems ◽  
Early Type Stars ◽  
Absolute Magnitudes ◽  
Bolometric Correction ◽  
Semi Empirical ◽  
Mirror Telescope

The presented paper deals with the results of electrophotometric observations of 59 components of 19 trapezia in Strömgren and Crawford six-colour photometric system. The multiple systems, selected from the Abastumani Catalogue of Trapezia (Salukvadze, 1978), are: ABAO 2, 8, 34, 48, 51, 62, 75, 94, 245, 312, 313, 316, 324, 348, 356, 363, 387, 396.Observations were made on the 125-cm mirror telescope with the use of a one-channel photometer, based on photon counting, with diaphragms 10″ and 20″. Reduction was done on the Observatory computer with a procedure described by Salukvadze and Javakhishvili (1989).We calculated the indices [m1],[c1] and [u-b] as in (Strömgren 1967, Philip and Egret 1980). The unreddened indices (b-y), m1 and c1 were calculated by the formulae of Crawford (1975).Semi-empirical calibrations for effective temperature, bolometric correction and mass for early-type stars, using Strömgren photometric indices c0 and beta, are given by Balona (1984). In order to determine absolute magnitudes we used the calibration from Balona and Shobbrook (1984).

scholarly journals The Zero-Point of the Cepheid Luminosity Scale from a Calibration of the Luminosities of Early-Type Stars

1985 ◽  
Vol 82 ◽  
pp. 201-202
Author(s):  
L. A. Balona ◽  
R. R. Shobbrook
Keyword(s):  
Zero Point ◽  
Photometric System ◽  
Early Type ◽  
Early Type Stars ◽  
The Absolute ◽  
Absolute Magnitudes ◽  
Zero Points

AbstractA new calibration of the absolute magnitudes of early-type stars in terms of the (β, c0) photometric system is used to establish the distance moduli of clusters containing Cepheids. The zero points of the period – luminosity and period – luminosity – colour relations are calculated and compared to previous determinations.

scholarly journals Criteria and Applications of the MK Classification (Early Type Stars)

1979 ◽  
Vol 47 ◽  
pp. 31-38
Author(s):  
Kerstin Lodén
Keyword(s):  
Theoretical Work ◽  
Two Dimensions ◽  
Fundamental Characteristic ◽  
Spectral Classification ◽  
Early Type ◽  
Classification Problems ◽  
New Techniques ◽  
Early Type Stars ◽  
Definition Of ◽  
Optimum Dispersion

AbstractThe fundamental characteristic of the MK classification system is the definition of an array of standard stars, arranged in two dimensions. New techniques and an enormous increase in observational and theoretical work since the original catalog in 191+3 have in various ways complicated the problem of spectral classification. Problems discussed are: 1.) The re-examination of standard stars; 2.) The optimum dispersion and the limits of dispersion for MK classification; and 3.) Some groups of peculiar objects.

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