scholarly journals The Evolutionary Status of Be Stars: Results from a Photometric Study of Southern Open Clusters

2005 ◽  
Vol 161 (1) ◽  
pp. 118-146 ◽  
Author(s):  
M. Virginia McSwain ◽  
Douglas R. Gies
Keyword(s):  
Open Clusters ◽  
Evolutionary Status ◽  
Be Stars ◽  
Photometric Study

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.

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 Search for Pulsational Instability among h Persei Stars

1995 ◽  
Vol 155 ◽  
pp. 299-300
Author(s):  
J. Krzesinski
Keyword(s):  
Northern Hemisphere ◽  
Open Clusters ◽  
Age Group ◽  
Be Stars ◽  
Double Cluster

AbstractThe northern-hemisphere double cluster h and χ Persei is one of the richest young open clusters. At least half of the brightest stars in the cluster appear to be variables and most of them axe Be stars. Till now there was no evidence for the presence of β Cephei stars in the cluster. It is remarkable that the similar age southern cluster NGC 3293 and other clusters belonging to the same age group are documented as clusters in which β Cephei stars have been observed. In this work we report finding one suspected β Cephei-like object, basing on our own observations.

scholarly journals Spectral and photometric study of Be Stars in the first exoplanet fields of CoRoT

2010 ◽  
Vol 6 (S272) ◽  
pp. 547-548
Author(s):  
Thierry Semaan ◽  
Christophe Martayan ◽  
Yves Frémat ◽  
Anne-Marie Hubert ◽  
Juan Gutiérrez Soto ◽  
...  
Keyword(s):  
Light Curves ◽  
Be Stars ◽  
Photometric Study ◽  
Fundamental Parameters ◽  
Fast Rotation ◽  
Synthetic Models ◽  
Hr Diagram

AbstractFirst we investigate the spectral and photometric properties (colours, magnitudes) of a sample of faint Be stars observed in the first exoplanet fields of CoRoT (IR1, LRA1 and LRC1). We determine the fundamental parameters by fitting ESO-FLAMES/GIRAFFE spectra with synthetic models taking account for non-LTE effects. After that we correct these parameters from fast rotation effects. We also study the location of each star in the (logL vs logT) HR diagram. Second we start to analyse the CoRoT light curves to investigate further the possible correlation between the pulsating properties and the fundamental parameters of the stars.

scholarly journals Photometric studies of Be star variability

1994 ◽  
Vol 162 ◽  
pp. 299-300
Author(s):  
John R. Percy
Keyword(s):  
Time Scales ◽  
Balmer Line ◽  
Radial Pulsation ◽  
Be Stars ◽  
Photometric Study ◽  
Short Term ◽  
Hot Stars ◽  
Be Star ◽  
Short Term Variability

Be stars are hot stars which have shown emission in at least one Balmer line on at least one occasion. As the definition implies, the Be phenomenon can be variable with time: on time scales of days to decades as the circumstellar disc develops and disperses; on time scales of days to months in a few Be stars which are interacting binaries; on time scales of 0.2 to 2 days due to non-radial pulsation or possibly rotation. The Be stars are worthy of photometric study because they are bright and numerous; the nature of the short-term variability is not yet agreed upon; the cause of the development of the disc - and its relationship to the short-term variability - is also not yet known.

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 Abundances of Be Stars in Very Young Open Clusters

2000 ◽  
Vol 175 ◽  
pp. 59-62 ◽  
Author(s):  
A. Marco ◽  
G. Bernabeu ◽  
J.M. Torrejón ◽  
J.J. Rodes ◽  
J. Fabregat
Keyword(s):  
Open Clusters ◽  
Be Stars ◽  
Ccd Photometry ◽  
The Galaxy

AbstractWe present here standard uvbyβ CCD photometry for five open clusters of the Galaxy in order to determine abundances of Be stars, as a function of age.

scholarly journals Composite Colour-Magnitude and Colour-Colour Diagrams for Be Stars in Open Clusters

1982 ◽  
Vol 98 ◽  
pp. 23-26
Author(s):  
J.-C. Mermilliod
Keyword(s):  
Age Groups ◽  
Open Clusters ◽  
Be Stars ◽  
Photoelectric Photometry ◽  
Absolute Magnitudes ◽  
Colour Indices

By the end of 1980, the total number of Be stars discovered in the field of open clusters amounted to 180 stars distributed in 60 clusters. Among these, 110 Be stars belong to 32 clusters included in the sample I studied, which contains 75 open clusters younger than the Hyades. But only 88 stars with complete UBV photoelectric photometry have been taken into consideration here. The concept of age groups, defined elsewhere (Mermilliod 1981a), is used throughout the present analysis, as well as the new estimate of the colour excesses and distance moduli I obtained for these 32 clusters. Under the assumption of uniform reddening across the clusters, absolute magnitudes and dereddened colour indices have been calculated for the 88 Be stars.

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