scholarly journals A Study of Main Sequence Early Type Stars

1979 ◽  
Vol 47 ◽  
pp. 483-490
Author(s):  
Ulf Sinnerstad
Keyword(s):  
Main Sequence ◽  
Photometric Study ◽  
Line Profiles ◽  
Early Type ◽  
Fundamental Parameters ◽  
Preliminary Results ◽  
Early Type Stars ◽  
Hydrogen Lines ◽  
Line Strengths

AbstractA spectroscopic and photometric study of 75 normal main sequence B2-B6 stars has been carried out. From the spectra (12 Å/mm, 3700-4800 Å) are determined: equivalent widths of all measurable lines, line profiles of hydrogen lines and v sin i. The photometric work includes besides uvby and β photometry, also photoelectrically determined line strengths of Hα and He I 4471 Å. Some preliminary results concerning the relation between the MK types and the atmospheric fundamental parameters (Teff, log g) of the stars are briefly discussed.

scholarly journals Comparison between model atmospheres and spectra from early-type stars

1965 ◽  
Vol 23 ◽  
pp. 147-161 ◽  
Author(s):  
E. H. Avrett ◽  
S. E. Strom
Keyword(s):  
Grey Model ◽  
Line Profiles ◽  
Early Type ◽  
Ultraviolet Continuum ◽  
Preliminary Calculation ◽  
Effective Temperatures ◽  
Early Type Stars ◽  
Hydrogen Lines ◽  
Good Agreement

To assist in the interpretation of ultraviolet continuum observations, we present observational features of a grid of non-grey model atmosphères in strict radiative equilibrium which have effective temperatures in the range 10000 °K to 20000 °K and surface gravities 103 and 104. For three models, we add the blended wings of the higher Balmer and Lyman hydrogen lines and include in an approximate way further effects of line blanketing in the ultraviolet. Finally, we present a preliminary calculation of the effect of departures from L. T. E. on the continuous flux.To examine the validity of the models, we compare the predicted continuous flux and predicted line profiles with the corresponding observed quantities for Vega and Sirius.We consider the question of discrepancies between theory and observations in the ultraviolet from the viewpoint of these new calculations, and find generally good agreement with recent observations made by T. Stecher.

scholarly journals C IV resonance line profiles in O stars

1979 ◽  
Vol 83 ◽  
pp. 95-98
Author(s):  
S. B. Parsons ◽  
J. D. Wray ◽  
K. G. Henize ◽  
G. F. Benedict
Keyword(s):  
Resonance Line ◽  
Main Sequence ◽  
Uv Spectra ◽  
Line Profiles ◽  
Early Type ◽  
Main Sequence Stars ◽  
Objective Prism ◽  
Early Type Stars

The S-019 experiment on Skylab (cf. Henize et al. 1975; “Paper I”) recorded far UV spectra in about 160 4° x 5° fields, covering 10% of the sky, on 101 film with a 15 cm aperture objective-prism telescope. Several hundred early-type stars were observed in the vicinity of 1550 Å with a resolution between 3 and 4 Å, as well as thousands of stars at longer wavelengths and correspondingly lower resolution. An atlas of spectra for types 04 to B5 is illustrated in Paper I. That figure shows that the P Cygni profile is a characteristic of all supergiants earlier than B3 and main sequence stars earlier than 08.

scholarly journals The Connection with B[e] stars

2000 ◽  
Vol 175 ◽  
pp. 26-36 ◽  
Author(s):  
Franz-Josef Zickgraf
Keyword(s):  
Common Property ◽  
Main Sequence ◽  
Emission Lines ◽  
Circumstellar Dust ◽  
Evolutionary Status ◽  
Be Stars ◽  
Early Type ◽  
Circumstellar Envelopes ◽  
Early Type Stars ◽  
Uniform Group

AbstractThe characteristics of the various types of B[e] stars are discussed and compared with those of classical Be stars. Both groups of stars are characterized by the presence of emission lines in their spectra, in particular of hydrogen. However, there are also significant differences between these classes. Classical Be stars lack hot circumstellar dust and strong forbidden low-excitation emission lines, which are typical characteristics produced by B[e]-type stars. While classical Be stars are a rather uniform group of early-type stars, B[e]-type stars form a quite heterogeneous group, very often of poorly known evolutionary status, comprising such diverse types of objects as near main-sequence objects, evolved lowmass proto-planetray nebulae and massive evolved hot supergiants. Even pre-main sequence Herbig Ae/Be stars sometimes find their way into the group of B[e] stars. However, despite these dissimilarities classical Be stars and B[e]-type stars, share a common property, namely the nonsphericity of their circumstellar envelopes.

scholarly journals A Comparison of Luminosity Calibrations for MK Classifications of OB Stars

1979 ◽  
Vol 47 ◽  
pp. 81-86
Author(s):  
Janet Rountree Lesh
Keyword(s):  
Main Sequence ◽  
Early Type ◽  
Class V ◽  
Ob Stars ◽  
Early Type Stars

It has been apparent for some time that there is a need for a single luminosity calibration to be used with modern MK types for early-type stars, at least from 0 through middle B. The widely used calibration of Blaauw (1963) has to be replaced because the refinement of the MK system - as reflected in the large collections of spectral types by Lesh (1968), Hiltner, Garrison, and Schild (1969) and Walborn (1971) - has led to a lower mean luminosity for most main sequence subgroups of early-type stars, as the higher luminosity stars tend to move out of class V. Thus the calibrations of Lesh (1968) and Walborn (1972, 1973) are systematically fainter than Blaauw’s

Problems in the Formation of Neutral Helium Lines in Early Type Stars

1970 ◽  
Vol 1 (7) ◽  
pp. 326-328
Author(s):  
R. W. Simpson
Keyword(s):  
Absorption Coefficient ◽  
Electron Scattering ◽  
Growth Analysis ◽  
Line Profiles ◽  
Early Type ◽  
Line Absorption ◽  
Early Type Stars ◽  
Made In ◽  
The Continuum

The aim of this work is to investigate certain assumptions that have been made in calculating line profiles and equivalent widths of neutral helium lines in early type stars. The effect of electron scattering on the continuum flux is investigated and a curve of growth analysis carried out to study this effect. The theories involved in calculating the line absorption coefficient are also investigated.

Hβ Line Profiles for Rapidly Rotating Early- Type Stars.

1965 ◽  
Vol 70 ◽  
pp. 320
Author(s):  
George W., II Collins ◽  
J. Patrick Harrington
Keyword(s):  
Line Profiles ◽  
Early Type ◽  
Early Type Stars
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