scholarly journals Results from six multiwavelength campaigns to study short-term FUV flux variability and phase-dependent mass loss in Be stars

1994 ◽  
Vol 162 ◽  
pp. 284-286
Author(s):  
Geraldine J. Peters
Keyword(s):  
High Resolution ◽  
Mass Loss ◽  
High Resolution Spectroscopy ◽  
Be Stars ◽  
Short Term ◽  
The Past ◽  
Flux Variability ◽  
Optical Region ◽  
Dependent Mass

During the past six years we have carried through seven multiwavelength, multisite campaigns to investigate the cause for short-term (rapid) photometric and spectroscopic variability in Be stars and assess its importance in driving the mass loss in these objects. These campaigns usually included simultaneous observations in the UV with the IUE and Voyager spacecraft and optical region with ground-based telescopes worldwide (photometry, high resolution spectroscopy, and polarimetry). Typically 10–25 observers from 5–9 countries participated. Stars that have been observed include λ Eri, ω Ori, o And, ∊ Cap, 28 Cyg, η Cen, 48 Lib, ζ Tau, ψ Per, and 2 Vul. We briefly summarize some of the results from the UV study here. Additional results from the ground-based data are given in other papers in this volume by D. Gies, M. Hahula, J. Percy, and D. McDavid.

scholarly journals Probing Be star disks: new insights from Hα spectroscopy and detailed numerical models

2010 ◽  
Vol 6 (S272) ◽  
pp. 398-399 ◽  
Author(s):  
Carol E. Jones ◽  
Christopher Tycner ◽  
Jessie Silaj ◽  
Ashly Smith ◽  
T. A. Aaron Sigut
Keyword(s):  
High Resolution ◽  
Numerical Models ◽  
Analytical Tool ◽  
High Resolution Spectroscopy ◽  
Be Stars ◽  
Line Shapes ◽  
Physical Conditions ◽  
Temperature Distributions ◽  
Inclination Angles ◽  
Be Star

AbstractHα high resolution spectroscopy combined with detailed numerical models is used to probe the physical conditions, such as density, temperature, and velocity of Be star disks. Models have been constructed for Be stars over a range in spectral types and inclination angles. We find that a variety of line shapes can be obtained by keeping the inclination fixed and changing density alone. This is due to the fact that our models account for disk temperature distributions self-consistently from the requirement of radiative equilibrium. A new analytical tool, called the variability ratio, was developed to identify emission-line stars at particular stages of variability. It is used in this work to quantify changes in the Hα equivalent widths for our observed spectra.

scholarly journals Joint Discussion 4 UV astronomy: stars from birth to death

2006 ◽  
Vol 2 (14) ◽  
pp. 169-194
Author(s):  
Ana I. Gómez de Castro ◽  
Martin A. Barstow
Keyword(s):  
High Resolution ◽  
Uv Spectroscopy ◽  
Broad Band ◽  
Mission Planning ◽  
High Resolution Spectroscopy ◽  
Low Resolution ◽  
Short Term ◽  
Uv Astronomy ◽  
Optical Telescope ◽  
The Moment

AbstractThe scientific program is presented as well a the abstracts of the contributions. An extended account is published in “The Ultraviolet Universe: stars from birth to death” (Ed. Gómez de Castro) published by the Editorial Complutense de Madrid (UCM), that can be accessed by electronic format through the website of the Network for UV Astronomy (www.ucm.es/info/nuva).There are five telescopes currently in orbit that have a UV capability of some description. At the moment, only FUSE provides any medium- to high-resolution spectroscopic capability. GALEX, the XMM UV-Optical Telescope (UVOT) and the Swift. UVOT mainly delivers broad-band imaging, but with some low-resolution spectroscopy using grisms. The primary UV spectroscopic capability of HST was lost when the Space Telescope Imaging Spectrograph failed in 2004, but UV imaging is still available with the HST-WFPC2 and HST-ACS instruments.With the expected limited lifetime of sl FUSE, UV spectroscopy will be effectively unavailable in the short-term future. Even if a servicing mission of HST does go ahead, to install COS and repair STIS, the availability of high-resolution spectroscopy well into the next decade will not have been addressed. Therefore, it is important to develop new missions to complement and follow on from the legacy of FUSE and HST, as well as the smaller imaging/low resolution spectroscopy facilities. This contribution presents an outline of the UV projects, some of which are already approved for flight, while others are still at the proposal/study stage of their development.This contribution outlines the main results from Joint Discussion 04 held during the IAU General Assembly in Prague, August 2006, concerning the rationale behind the needs of the astronomical community, in particular the stellar astrophysics community, for new UV instrumentation. Recent results from UV observations were presented and future science goals were laid out. These goals will lay the framework for future mission planning.

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 Infrared spectroscopy of Be stars

1994 ◽  
Vol 162 ◽  
pp. 412-413
Author(s):  
R.M. Torres ◽  
A. Damineli-Neto ◽  
J.A. de Freitas Pacheco
Keyword(s):  
Mass Loss ◽  
Near Infrared ◽  
Uv Spectra ◽  
Emission Lines ◽  
Be Stars ◽  
B Stars ◽  
Astrophysical Objects ◽  
Optical Region ◽  
Support Excitation ◽  
Loss Rates

FeII emission lines are present in a variety of astrophysical objects and, in particular, in Be stars, where in some situations they can also be seen in absorption. Selvelli & Araujo (1984) studied a sample of classical Be stars that have FeII emission lines in the optical region. The analysis of IUE spectra of those stars revealed that, for the majority of the objects, neither absorption nor emission FeII features were present in the UV. The conclusion was that their data could not support excitation of FeII by continuum fluorescence. On the other hand, FeIII of circumstellar origin is often seen in absorption in the UV spectra of Be stars (Snow & Stalio 1987 and references therein). This could be an indication that the optical FeII emission lines are originated from recombination and cascade. However, Selvelli & Araujo (1984) argued that, since the multiplet UV 191 of FeII does not appear in emission, that mechanism is probably not relevant. In the present work we report new spectroscopic observations in the near infrared of a sample of 60 Be stars, including the prominent FeII 999.7 nm emission line. This line is also present in the spectra of superluminous B stars for which mass loss rates have recently been estimated (Lopes, Damineli-Neto & Freitas Pacheco 1992). We derived mass loss rates from the infrared line luminosities, in agreement with those derived by other methods. We also found a new evidence of the Be envelope flattening through the FeII/Paδ line ratio.

scholarly journals A First Search for Rapid Variations of Stellar and Circumstellar Balmer Discontinuity in Be Stars

1995 ◽  
Vol 155 ◽  
pp. 303-304
Author(s):  
S. Štefl ◽  
D. Baade ◽  
J. Cuypers
Keyword(s):  
High Resolution ◽  
Line Profile ◽  
Time Scale ◽  
Large Amplitude ◽  
High Resolution Spectroscopy ◽  
Be Stars ◽  
Be Star

AbstractSpectrophotometric observations of the Be star ηCen obtained in May, 1993 show smooth variations of both the stellar and circumstellar Balmer discontinuity (BD) on a time scale of hours. Simultaneous photometry and high-resolution spectroscopy suggest possible correlations with the large-amplitude brightness and line-profile variations.

scholarly journals Short-term variability and mass loss in Be stars

2016 ◽  
Vol 588 ◽  
pp. A56 ◽  
Author(s):  
D. Baade ◽  
Th. Rivinius ◽  
A. Pigulski ◽  
A. C. Carciofi ◽  
Ch. Martayan ◽  
...  
Keyword(s):  
Mass Loss ◽  
Be Stars ◽  
Short Term ◽  
Short Term Variability

scholarly journals Short-term variability and mass loss in Be stars

2016 ◽  
Vol 593 ◽  
pp. A106 ◽  
Author(s):  
Th. Rivinius ◽  
D. Baade ◽  
A. C. Carciofi
Keyword(s):  
Mass Loss ◽  
Be Stars ◽  
Short Term ◽  
Short Term Variability
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