Sign on

SAO/NASA ADS Astronomy Abstract Service

· Find Similar Abstracts (with default settings below)
· Full Refereed Journal Article (PDF/Postscript)
· Full Refereed Scanned Article (GIF)
· References in the article
· Citations to the Article (27) (Citation History)
· Refereed Citations to the Article
· SIMBAD Objects (11)
· Also-Read Articles (Reads History)
· HEP/Spires Information
·
· Translate This Page
Title:
Central quasi-emission peaks in shell spectra and the rotation of disks of Be stars
Authors:
Rivinius, Th.; Štefl, S.; Baade, D.
Affiliation:
AA( Landessternwarte Königstuhl, D-69117 Heidelberg, Germany), AB(Astronomical Institute, Academy of Sciences, CZ-251 65 Ondřejov, Czech Republic), AC(European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei München, Germany)
Publication:
Astronomy and Astrophysics, v.348, p.831-842 (1999) (A&A Homepage)
Publication Date:
08/1999
Origin:
A&A
A&A Keywords:
LINE: PROFILES, LINE: FORMATION, STARS: EMISSION-LINE, BE, STARS: CIRCUMSTELLAR MATTER, STARS: MASS-LOSS
Bibliographic Code:
1999A&A...348..831R

Abstract

New high-resolution echelle spectra are presented for all 6 B-type stars currently known to exhibit so-called central quasi-emission peaks (CQE's). Empirical requirements are derived on the circumstances which favour the appearance of such features. The presence of a circumstellar disk seen edge-on is the most important. Furthermore, the disk should be optically thin in the continuum, have a small spatial extent, and show little line broadening. Both this set of conditions and the observed line profiles are compared to a model by Hanuschik (\cite{hanuschik95}) for the formation of shell lines in circumstellar disks with Keplerian rotation. This model predicts not only the existence of CQE's, but also the same actual circumstances of their occurrence. They result from the local minimum at zero radial velocity in the fraction of the stellar disk that is occulted by circumstellar gas in Keplerian orbital motion, i.e. by gas moving perpendicular to the line of sight. In particular, CQE's are in spite of their name not related to any emission process but are a pure absorption phenomenon. All currently available observations of CQE's are consistent with this model, which appears to have considerable diagnostic potential for the understanding of the structure and dynamics of Be star disks. Only one of the 6 stars (nu Pup) was not previously known to ever have displayed shell or only emission lines. But the new Hα and Hβ profiles clearly show the presence of variable amounts of circumstellar matter. Previously suggested photospheric explanations for CQE's are nevertheless briefly examined. In a given star, CQE's seem to appear with the highest probability at times when the innermost regions of the disk are being re-supplied with matter. With the success of Hanuschik's model, CQE's furthermore become one of the most important indicators of rotational support of disks of Be stars. Together with other evidence for rotation compiled from the literature, this leads to the conclusion that models for the formation of disks need to include a mechanism for sufficient angular momentum transfer. In the context of Hanuschik's model for CQE's, the considerable acceleration inherent to wind-compressed disks (WCD's) presents an additional difficulty for the WCD model in its basic form. Based on observations collected at the European Southern Observatory at La Silla, Chile, ESO prop.~Nos.~55.D-0502, 56.D-0381, 58.D-0697, and the German-Spanish Astronomical Centre, Calar Alto, operated by the Max-Planck-Institute for Astronomy, Heidelberg, jointly with the Spanish National Commission for Astronomy, Visiting Astronomer TR

Printing Options

Print whole paper
Print Page(s) through

Return 600 dpi PDF to Acrobat/Browser. Different resolutions (200 or 600 dpi), formats (Postscript, PDF, etc), page sizes (US Letter, European A4, etc), and compression (gzip,compress,none) can be set through the Printing Preferences


More Article Retrieval Options

HELP for Article Retrieval
Bibtex entry for this abstract   Preferred format for this abstract (see Preferences)
   

Find Similar Abstracts:

Use: Authors
Title
Keywords (in text query field)
Abstract Text
Return: Query Results Return    items starting with number
Query Form
Database: Astronomy
Physics
arXiv e-prints