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)
· On-line Data
· References in the article
· Citations to the Article (345) (Citation History)
· Refereed Citations to the Article
· SIMBAD Objects (2012)
· Associated Articles
· Also-Read Articles (Reads History)
·
· Translate This Page
Title:
The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars
Authors:
Abt, Helmut A.; Morrell, Nidia I.
Publication:
Astrophysical Journal Supplement v.99, p.135 (ApJS Homepage)
Publication Date:
07/1995
Origin:
APJ; KNUDSEN
Astronomy Keywords:
STARS: CHEMICALLY PECULIAR, STARS: EARLY-TYPE, STARS: FUNDAMENTAL PARAMETERS, STARS: ROTATION
DOI:
10.1086/192182
Bibliographic Code:
1995ApJS...99..135A

Abstract

We obtained new data to determine whether the spectral appearance of A-type stars is entirely determined by their rotational velocities. For this purpose we derived rotational velocities for 1700 northern A-type stars from CCD coudé spectra, calibrated with the new Slettebak et al. system, and new MK classifications based on wide photographic Cassegrain spectra for 2000 northern and some southern stars in the Bright Star Catalogue. In addition we determined the equivalent widths of the lambda4481 Mg II lines in the coudé spectra. Tables and graphs show the variations of rotational velocities and lambda4481 line strengths as functions of type and luminosity, and frequencies of the normal and abnormal stars.

After deconvolutions of the rotational velocities, assuming random orientations of rotational axes, we find that all rapid rotators have normal spectra and nearly all slow rotators have abnormal spectra (Ap or Am). Those abnormalities are generally attributed to diffusion and can occur only with little rotational mixing. However at all types there are overlaps of these distributions, implying that a given intermediate rotational velocity is insufficient to determine whether the star should have a normal or abnormal spectrum. However, we realized that (1) some of our "standards," such as Vega and alpha Dra, are really abnormal, causing us to classify similar peculiar stars as "normal," (2) many of the "normal" stars near A2 IV have the characteristics of peculiar stars such as low rotational velocities and weak 4481 Mg II and K lines, and (3) the mean rotational velocities of "normal" stars are depressed just at those types where the Ap and Am stars are most frequent. Therefore we conclude that the overlaps are due to our failure to detect all the abnormal stars and that a specific rotational velocity is probably enough to determine whether a star will have a normal or abnormal spectrum.


Associated Articles

Source Paper     Catalog Description    


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)

  New!

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