Deriving the Geometry of Be Star Circumstellar Envelopes from Continuum Spectropolarimetry. I. The Case of ζ Tauri

1997 ◽  
Vol 477 (2) ◽  
pp. 926-939 ◽  
Author(s):  
Kenneth Wood ◽  
K. S. Bjorkman ◽  
J. E. Bjorkman
Keyword(s):  
Circumstellar Envelopes ◽  
Be Star

scholarly journals Magnetic Fields in Be Stars? (Review Paper)

1987 ◽  
Vol 92 ◽  
pp. 38-48
Author(s):  
Paul K. Barker
Keyword(s):  
Magnetic Fields ◽  
Field Strength ◽  
Review Paper ◽  
Stellar Winds ◽  
Be Stars ◽  
Circumstellar Envelopes ◽  
Star Models ◽  
Upper Limits ◽  
Be Star

AbstractNo mean longitudinal or toroidal magnetic fields have yet been detected on any classical Be star. Models of stellar winds and circumstellar envelopes around magnetic Be stars are not appreciably constrained by present observed upper limits on field strength. A few magnetic Be stars do exist among the helium strong stars, but these objects show spectral phenomenology which is unmistakably distinct from that shown by every other object known as a Be star.

scholarly journals Models for the Circumstellar Envelopes of Be Stars: (Review Paper)

1976 ◽  
Vol 70 ◽  
pp. 335-370 ◽  
Author(s):  
J. M. Marlborough
Keyword(s):  
Ad Hoc ◽  
Review Paper ◽  
Circumstellar Matter ◽  
Be Stars ◽  
Circumstellar Envelopes ◽  
Structure And Dynamics ◽  
Restricted Problems ◽  
Be Star ◽  
Physical Phenomena

A survey is presented of the theoretical attempts to determine the structure of the circumstellar matter around Be stars. The general equations describing the structure and dynamics of Be star envelopes are given. The complications introduced by various physical phenomena are briefly discussed and initial attempts to solve restricted problems are considered. The various ad hoc models proposed for Be stars are discussed and comparisons of the observations with predictions of these models are illustrated. The strengths and weaknesses of these models are evaluated and areas where progress is being or should be made are considered.

scholarly journals Recent Results from Ultraviolet and Optical Spectropolarimetry of Hot Stars

1994 ◽  
Vol 162 ◽  
pp. 219-229
Author(s):  
K.S. Bjorkman
Keyword(s):  
Linear Polarization ◽  
Optical Data ◽  
Time Variability ◽  
Be Stars ◽  
Circumstellar Envelopes ◽  
Polarization Data ◽  
Hot Stars ◽  
New Models ◽  
Be Star ◽  
The Continuum

The first comprehensive linear polarization data on hot stars covering the spectral range from 1500 to 7600Å are presented. These results are based on recent observations made with the Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE), combined with ground-based observations from the Pine Bluff Observatory. Implications of the data for models of the circumstellar envelopes of hot stars are discussed, with particular emphasis on the surprising results found for the rapidly rotating Be stars. In particular, WUPPE discovered that the continuum polarization in Be stars decreases into the ultraviolet, which was not predicted by models prior to the observations. Time variability in the optical data is also discussed. Possible interpretations of these results are examined in the light of recent new models for Be star disks.

scholarly journals Continuous spectra of circumstellar envelopes of Be stars

1994 ◽  
Vol 162 ◽  
pp. 425-426
Author(s):  
D. Rohe-Koths ◽  
J. Dachs
Keyword(s):  
Line Emission ◽  
Circumstellar Disks ◽  
Balmer Line ◽  
Be Stars ◽  
Continuous Emission ◽  
Circumstellar Envelopes ◽  
Recombination Radiation ◽  
Infrared Spectral ◽  
Be Star ◽  
Central Stars

Line emission in Be star spectra is accompanied by continuous emission both in the Balmer continuum and in the infrared spectral region, due to the same process that is responsible for Balmer line emission, i.e. to recombination radiation from ionized hydrogen in the extended circumstellar disks surrounding the hot central stars.

scholarly journals Interferometric survey of Be stars with the CHARA array

2010 ◽  
Vol 6 (S272) ◽  
pp. 634-635 ◽  
Author(s):  
Yamina N. Touhami ◽  
Douglas R. Gies ◽  
Gail H. Schaefer ◽  
Noel D. Richardson ◽  
Stephen J. Williams ◽  
...  
Keyword(s):  
Rotational Velocity ◽  
Circumstellar Disks ◽  
Geometrical Parameters ◽  
Be Stars ◽  
Circumstellar Envelopes ◽  
Disk Model ◽  
Spatially Resolved ◽  
Near Ir ◽  
Be Star ◽  
Chara Array

AbstractWe present the first spatially resolved observations of circumstellar envelopes of 25 bright northern Be stars. The survey was performed with the CHARA Array interferometer in the K-band at intermediate and long baselines. The interferometric visibilities are well fitted by a viscous disk model where the gas density steeply decreases with the radius. Physical and geometrical parameters such as the density profile, the inclination, and the position angles of the circumstellar disks are determined. We find that the density radial exponent ranges between n ≈ 2.4 − 3.2, which is consistent with previous IRAS measurements. We have also obtained simultaneous optical and near-IR spectrophotometric measurements, and found that the model reproduces well the observed disk IR-continuum excess emission. By combining the projected rotational velocity of the Be star with the disk inclination derived from interferometry, we give estimates of the equatorial rotational velocities of these Be stars.

scholarly journals Rotationally-Enhanced Stellar Winds (Review Paper)

1987 ◽  
Vol 92 ◽  
pp. 316-338
Author(s):  
J. M. Marlborough
Keyword(s):  
Mass Transfer ◽  
Stellar Wind ◽  
Review Paper ◽  
Current Status ◽  
Stellar Winds ◽  
Be Stars ◽  
Stellar Rotation ◽  
Circumstellar Envelopes ◽  
Wind Model ◽  
Be Star

The rotationally-enhanced stellar wind model for Be stars represents one attempt to understand many of the phenomena related to Be stars in terms of a stellar wind distorted and perhaps also enhanced by rapid stellar rotation. This review will concentrate exclusively on this particular approach; the current status of other attempts to model the circumstellar envelopes (CE) of Be stars are described in other reviews in this volume. It is assumed that Be stars are single stars; if a member of a multiple system, the separation of all components from the Be star is assumed to be sufficiently large that interactions due to mass transfer from any companion to the Be star are negligible.

scholarly journals Global disk oscillations: theoretical line profiles

1994 ◽  
Vol 162 ◽  
pp. 382-383
Author(s):  
W. Hummel ◽  
R.W. Hanuschik
Keyword(s):  
Emission Line ◽  
Line Profile ◽  
Line Profiles ◽  
Circumstellar Envelopes ◽  
Be Star ◽  
Hα Emission ◽  
Line Transfer ◽  
Theoretical Line

Based on 3D radiative line transfer calculations we present Hα emission line profiles of Be star circumstellar envelopes undergoing one-armed global disk oscillations. The results are in agreement with the observed line profile variability.

The circumstellar disk of the Be star 28 (ω) CMa

2003 ◽  
Vol 6 ◽  
pp. 257-257
Author(s):  
S. Štefl ◽  
W. Nowotny-Schipper ◽  
J. Reunanen
Keyword(s):  
Circumstellar Disk ◽  
Be Star

scholarly journals The chemistry of cool circumstellar envelopes

1987 ◽  
Vol 122 ◽  
pp. 551-552
Author(s):  
L.A.M. Nejad ◽  
T. J. Millar
Keyword(s):  
Kinetic Model ◽  
Chemical Kinetic ◽  
Time Dependent ◽  
Circumstellar Envelopes ◽  
Chemical Kinetic Model ◽  
Ion Molecule Reactions ◽  
Cool Stars

We have developed a time-dependent chemical kinetic model to describe the chemistry in the circumstellar envelopes of cool stars, with particular reference to IRC + 10216. Our detailed calculations show that ion-molecule reactions are important in the formation of many of the species observed in IRC + 10216.

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