Synthetic filter photometry and evolutionary status of two Be stars in the association Per OB1

1987 ◽  
Vol 93 ◽  
pp. 654
Author(s):  
Ana V. Torres
Keyword(s):  
Evolutionary Status ◽  
Be Stars ◽  
Filter Photometry

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 O and Of Stars

1973 ◽  
Vol 49 ◽  
pp. 93-107
Author(s):  
Peter S. Conti
Keyword(s):  
Visible Spectrum ◽  
Emission Lines ◽  
Absorption Lines ◽  
Evolutionary Status ◽  
Be Stars ◽  
Type B ◽  
No Emission ◽  
Hot Stars ◽  
Hydrogen Lines ◽  
The Continuum

My intention here is to discuss the ‘high temperature’ portion of this symposium and call attention to those stars that are called Of. There are some similarities in spectral appearance to WR stars, e.g. emission lines. I should first like to define what I think are the essential differences among four groups of hot stars;O stars: Stars that have only absorption lines in the visible spectrum. Type O is distinguished from type B by the presence of He ii 4541 at MK dispersion. It may be that some (supergiants) O stars will have emission lines in the rocket UV region but this description will be primarily concerned with ground based observations.Of stars: These are O type stars that also have λλ 4634,40 N iii in emission above the continuum. In addition to normal O star absorption lines and N iii emission, they may also have other lines in emission. I will discuss this further below.Oe stars: These are O type stars that have emission in the hydrogen lines (or at least at Hα), but with no emission in N iii or in other lines. I personally think that this small class of objects is related to the Be stars in their evolutionary status and in their emission mechanism.WR stars: These stars are primarily characterized by emission lines. The only absorption lines seen are violet shifted (P Cyg type). Although in some cases emission lines appear which are similar to those found in some Of stars, the latter types always have some unshifted absorption lines present. Several Of stars have P Cyg profiles in some lines.

scholarly journals Be Phenomena in Young Early-type Stars: Various Forms of Interaction between the Star and the Circumstellar Gaseous Envelope

2000 ◽  
Vol 175 ◽  
pp. 344-347
Author(s):  
M. Pogodin
Keyword(s):  
High Resolution ◽  
Stellar Wind ◽  
Main Sequence ◽  
Stellar Surface ◽  
High Resolution Spectroscopy ◽  
Evolutionary Status ◽  
Be Stars ◽  
Early Type ◽  
Early Type Stars ◽  
Gaseous Envelope

AbstractNew results of high-resolution spectroscopy of four pre-main sequence Ae/Be stars are presented. An analysis of parameters of lines originating in different regions of the circumstellar (CS) envelope (Hα, Hβ, He I 5876, DNal) allows to reconstruct a picture of the interaction between the star and the CS environment which can be displayed in different forms. At least two separate processes seem to impact the structural and kinematical properties of the envelope: the stellar wind from the stellar surface and the matter infall onto the star from the CS media. A possible relation between these two phenomena is discussed in the framework of different models. Some similarity between observational phenomena in Herbig Ae/Be and classical Be stars is noted in spite of their difference in evolutionary status.

scholarly journals Where do Be stars stand in the picture of rotational mixing?

2010 ◽  
Vol 6 (S272) ◽  
pp. 85-86
Author(s):  
Paul R. Dunstall ◽  
Ines Brott ◽  
Philip L. Dufton ◽  
Chris J. Evans
Keyword(s):  
Critical Velocity ◽  
Rotational Velocity ◽  
Magellanic Clouds ◽  
Evolutionary Status ◽  
Evolutionary Models ◽  
Be Stars ◽  
Atmospheric Parameters ◽  
B Stars ◽  
The Absolute ◽  
Fast Rotating

AbstractAtmospheric parameters and photospheric abundances have been estimated for 60 Be-type stars located in 4 fields over the Magellanic Clouds. Particular attention has been given to the absolute nitrogen abundances to test theories of rotational mixing, an important factor in the evolutionary status of B-type stars, Hunter et al. (2008). The analysis used the non-LTE atmospheric code TLUSTY and required the implementation of a procedure to compensate for possible contamination due to the presence of a circumstellar disc. Through comparison with evolutionary models of fast rotating B-type stars and projected rotational velocity distributions our results support the theory that Be-type stars are typically faster rotators than B stars, but the measured nitrogen enhancements appear to be significantly less than expected for Be stars rotating with velocities greater than 70% of their critical velocity

scholarly journals On the evolutionary status of Be stars

2005 ◽  
Vol 441 (1) ◽  
pp. 235-248 ◽  
Author(s):  
J. Zorec ◽  
Y. Frémat ◽  
L. Cidale
Keyword(s):  
Evolutionary Status ◽  
Be Stars

scholarly journals Spectroscopy of Be stars in NGC 330

1994 ◽  
Vol 162 ◽  
pp. 269-270 ◽  
Author(s):  
Paolo A. Mazzali ◽  
F. Pasian ◽  
D.J. Lennon ◽  
P. Bonifacio ◽  
V. Castellani
Keyword(s):  
Open Cluster ◽  
Model Atmosphere ◽  
Evolutionary Status ◽  
Be Stars ◽  
Atmospheric Parameters ◽  
Medium Resolution ◽  
Young Open Cluster

Medium resolution (2Å/px) but high s/n spectra of approximately twenty of the brightest blue stars in the young open cluster NGC 330 in the SMC have been obtained with EFOSC1 on the ESO 3.6m telescope, and analyzed in order to determine the atmospheric parameters and the evolutionary status of the stars. LTE and NLTE model atmosphere calculations were used to determine the stellar parameters. The Teff values were derived from fits of the UV continua for all stars where these were available, using Robertson's (1974) B and V photometry to scale the Kurucz model fluxes for metallicity Z = 0.1Z⊙. Luminosities of the sample stars lie in the range 4.0 < log(L*/L⊙) < 5.0 and spectral types between B0 and late-B.

scholarly journals On the Percentage of Be Stars in Galactic Open Clusters

1987 ◽  
Vol 92 ◽  
pp. 503-504
Author(s):  
A. Reitermann ◽  
J. Krautter ◽  
B. Wolf ◽  
B. Bashek
Keyword(s):  
Spectroscopic Study ◽  
Open Clusters ◽  
Evolutionary Status ◽  
Be Stars ◽  
Chemical Abundance ◽  
B Stars ◽  
Knowing That ◽  
Be Star ◽  
High Fraction ◽  
Young Clusters

Knowing that especially young clusters can contain a considerable high fraction of Be stars (Mermilliod 1982, Feast 1972) we made a spectroscopic study of Hα on the ratio of B/Be stars. The aim was to select normal B stars for chemical abundance analyses.It is well known that a promising way to investigate the evolutionary status of Be stars is to study their frequency and positions in the H-R diagram of open clusters. However, these studies have not yet provided satisfactory results (cf. e.g. Slettebak 1985); observations concerning the B/Be star ratio are badly needed. Therefore we present our observations although they are only a by-product from a different program.

Spectrophotometric observations and evolutionary status of ten Be stars

1987 ◽  
Vol 129 (2) ◽  
pp. 251-260 ◽  
Author(s):  
Mahendra Singh ◽  
U. S. Chaubey
Keyword(s):  
Evolutionary Status ◽  
Be Stars

scholarly journals Synthetic uvby-β Photometry of HD 12856 and HD 13890

1987 ◽  
Vol 92 ◽  
pp. 519-522
Author(s):  
A. V. Torres ◽  
C. D. Garmany
Keyword(s):  
Evolutionary Status ◽  
Be Stars ◽  
B Stars ◽  
Color Indices

AbstractStromgren and Hβ colors have been measured from spectrophotometric observations of two Be stars without published photometry in Per OB1: HD 12856 (BO pe) and HD 13890 (B1 III:pe). Stellar parameters and improved spectral types are then derived from the color indices and the calibrations of Jakobsen (1986a,b,c). These are compared with the parameters of normal B stars and they are used to estimate the evolutionary status of the stars.

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