On the Absorption Lines of Hydrogen in be Stars

1932 ◽  
Vol 76 ◽  
pp. 309 ◽  
Author(s):  
O. Struve
Keyword(s):  
Absorption Lines ◽  
Be Stars

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 The Onset of Quasi-Periodic Variations in Be Stars

1993 ◽  
Vol 134 ◽  
pp. 223-225
Author(s):  
T. Kogure ◽  
M. Mon ◽  
M. Suzuki
Keyword(s):  
Sudden Onset ◽  
Radial Velocities ◽  
Emission Lines ◽  
Absorption Lines ◽  
Close Binaries ◽  
Be Stars ◽  
Early Type ◽  
Stable Period ◽  
Long Term Variations

We present some evidence of the quasi-periodic long-term variations (QPLV) in the violet-to-red ratio of double-peaked emission lines (V/R variation) and/or in the radial velocities of shell absorption lines for some Be stars. Although the V/R variations are rather prevailing phenomena among Be stars, the QPLV is remarkable by the following characteristics: (1)The QPLV appears as a sudden onset of repeated V/R variations after a long (10 years), almost stable period, and it persists for a few or several periods in ten or more years.(2)The period and amplitude of V/R variations change from cycle to cycle and from star to star. The variations of radial velocities (RV) of shell absorption lines are usually nearly parallel with the V/R variations.(3)The QPLV appears usually in early type Be stars with large rotational velocities, regardless whether the stars are normal Be or shell stars, and whether they are close-binaries or single stars.

scholarly journals The Relationship of the Oe to the Be Stars

1976 ◽  
Vol 70 ◽  
pp. 139-147 ◽  
Author(s):  
Stewart A. Frost ◽  
Peter S. Conti
Keyword(s):  
Formation Mechanism ◽  
Main Sequence ◽  
Absorption Lines ◽  
Be Stars ◽  
Line Profiles ◽  
Broad Absorption ◽  
Hydrogen Lines ◽  
Relationship Of ◽  
The Relationship ◽  
Narrow Emission

Oe stars are earlier type analogues of the better known Be class. These stars have relatively narrow emission in the hydrogen lines and sometimes in the helium lines, which often appears to be double. In several Oe stars, the emission is intermittent. Other properties of the class include relatively broad absorption lines and luminosities near the main sequence. Line profiles in three representative Oe stars are presented and discussed. The similarity of the spectra of Oe and Be stars suggests that the formation mechanism for the emitting region, whatever it is, must extend to the mid O-type stars, at least.

scholarly journals Ultraviolet Observations of Interacting Binary Be Stars

1982 ◽  
Vol 98 ◽  
pp. 405-409
Author(s):  
Geraldine J. Peters ◽  
Ronald S. Polidan
Keyword(s):  
High Resolution ◽  
Data Base ◽  
Mass Flow ◽  
Complex Structure ◽  
Absorption Lines ◽  
Be Stars ◽  
Mass Outflow ◽  
Ultraviolet Observations ◽  
Initial Results

Initial results from the analysis of a series of timed, high resolution IUE observations of HR 2142, ϕ Per, CX Dra, KX And, AU Mon, and TT Hya are presented. The data base for HR 2142 also includes Copernicus U1 and U2 observations. Variable absorption lines, indicative of mass flow in the system, are observed in all objects except ϕ Per. We also, in general, find evidence of mass outflow in the form of winds and/or discrete components. We observe variable N V absorption in CX Dra and AU Mon and emission features in KX And and ϕ Per (C IV only). U1 data reveals the presence of complex structure in the gas stream in HR 2142. These observations are compared with those of Be stars which are not thought to be interacting binaries.

scholarly journals Correlation Between Spectrum Characteristics and Photometric Behaviour of Be Stars

1982 ◽  
Vol 98 ◽  
pp. 65-67
Author(s):  
G. A. Ponomareva
Keyword(s):  
Emission Line ◽  
Variable Stars ◽  
Absorption Lines ◽  
Be Stars ◽  
Photometric Variability ◽  
Spectrum Characteristics ◽  
Statistical Relationships

Based upon a sample of 140 B0-A0 emission-line stars contained in “A Photographic Atlas of Be stars” statistical relationships between variable stars and Be stars are examined. It is found that 44 % of all the stars of the sample show some kind of photometric variations. The stars with narrow metallic absorption lines display relatively more intense photometric activity. Proceeding from this conclusion, the photometric variability of two stars HD 50138 and HD 193182 can be predicted.

scholarly journals Hα emission-line stars in molecular clouds

2019 ◽  
Vol 630 ◽  
pp. A90 ◽  
Author(s):  
Bertil Pettersson ◽  
Bo Reipurth
Keyword(s):  
Molecular Clouds ◽  
Young Stellar Objects ◽  
Be Stars ◽  
Stellar Objects ◽  
Strong Concentration ◽  
Ob Stars ◽  
Star Forming ◽  
Hα Emission ◽  
Objective Prism ◽  
Emission Stars

A deep objective-prism survey for Hα emission stars towards the Canis Major star-forming clouds was performed. A total of 398 Hα emitters were detected, 353 of which are new detections. There is a strong concentration of these Hα emitters towards the molecular clouds surrounding the CMa OB1 association, and it is likely that these stars are young stellar objects recently born in the clouds. An additional population of Hα emitters is scattered all across the region, and probably includes unrelated foreground dMe stars and background Be stars. About 90% of the Hα emitters are detected by WISE, of which 75% was detected with usable photometry. When plotted in a WISE colour–colour diagram it appears that the majority are Class II YSOs. Coordinates and finding charts are provided for all the new stars, and coordinates for all the detections. We searched the Gaia-DR2 catalogue and from 334 Hα emission stars with useful parallaxes, we selected a subset of 98 stars that have parallax errors of less than 20% and nominal distances in the interval 1050 to 1350 pc that surrounds a strong peak at 1185 pc in the distance distribution. Similarly, Gaia distances were obtained for 51 OB-stars located towards Canis Major and selected with the same parallax errors as the Hα stars. We find a median distance for the OB stars of 1182 pc, in excellent correspondence with the distance from the Hα stars. Two known runaway stars are confirmed as members of the association. Finally, two new Herbig-Haro objects are identified.

scholarly journals The Use of Terms and Definitions in the Study of Be Stars (Review Paper)

1987 ◽  
Vol 92 ◽  
pp. 3-21
Author(s):  
George W. Collins
Keyword(s):  
Review Paper ◽  
Be Stars ◽  
Basic Definition ◽  
The Subject ◽  
Definition Of ◽  
Incorrect Usage

AbstractIn this paper I shall examine the use and misuse of some astronomical terminology as it is commonly found in the literature. The incorrect usage of common terms, and sometimes the terms themselves, can lead to confusion by the reader and may well indicate misconceptions by the authors. A basic definition of the Be phenomena is suggested and other stellar characteristics whose interpretation may change when used for non-spherical stars, is discussed. Special attention is paid to a number of terms whose semantic nature is misleading when applied to the phenomena they are intended to represent. The use of model-dependent terms is discussed and some comments are offered which are intended to improve the clarity of communication within the subject.

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