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 (398) (Citation History)
· Refereed Citations to the Article
· SIMBAD Objects (40)
· NED Objects (9)
· Also-Read Articles (Reads History)
·
· Translate This Page
Title:
The luminous blue variables: Astrophysical geysers
Authors:
Humphreys, Roberta M.; Davidson, Kris
Affiliation:
AA(University of Minnesota, Minneapolis, MN, US), AB(University of Minnesota, Minneapolis, MN, US)
Publication:
Astronomical Society of the Pacific, Publications (ISSN 0004-6280), vol. 106, no. 704, p. 1025-1051 (PASP Homepage)
Publication Date:
10/1994
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
BLUE STARS, BRIGHTNESS, BRIGHTNESS DISTRIBUTION, GEYSERS, STELLAR LUMINOSITY, STELLAR MAGNITUDE, STELLAR OSCILLATIONS, VARIABLE STARS, COLOR-MAGNITUDE DIAGRAM, HERTZSPRUNG-RUSSELL DIAGRAM, PHOTOSPHERE, STELLAR ACTIVITY, STELLAR MASS, STELLAR MASS EJECTION, SUPERGIANT STARS
DOI:
10.1086/133478
Bibliographic Code:
1994PASP..106.1025H

Abstract

Some of the most luminous stars have sporadic, violent mass-loss events whose causes are not understood. These evolved hot stars are called luminous blue variables (LBVs), and their instability may shape the appearance of the upper Hertzsprung-Russell (HR) diagram. LBV eruptions are interestingly reminiscent of geysers or even volcanos. They have received considerable observational attention since 1980, but theoretical work to explain the instability has been scarce. In a typical LBV eruption, the star's photosphere expands and the apparent temperature decreases to near 8000 K. During these normal eruptions the bolometric luminosity remains constant, as typified by S Doradus, AG Carinae, and R 127. A few LBV's, specifically Eta Carinae, P Cygni, V12 in NGC 2403, and SN 1961V, have giant eruptions in which the total luminosity actually increases by more than one or two magnitudes. The star may expel as much as a solar mass or more with a total luminous output rivaling a supernova. The classical LBVs have luminosities greater than MBol approximately equal to -9.6 mag, suggesting initial mass greater than 50 solar mass. These stars have very likely not been red supergiants as there are no evolved cool stars of comparable luminosity. Their instability may prevent their evolution to the red supergiant region. There is also a group of less luminous LBVs (MBol approximately equal to -8 to -9 mag) with low temperatures, smaller amplitudes, and lower mass-loss rates. These stars have probably been red supergiants and have shed a lot of mass prior to their current unstable state. Although the physical cause of the LBV instability is not yet understood, the most likely mechanisms involve radiation pressure (the opacity-modified Eddington limit) or dynamical instabilities in the outer layers as the star evolves off the main sequence. In this review, we summarize the physical characteristics and behavior of LBVs and discuss their brief but critical role in massive star evolution, and possible mechanisms for their remarkable instability.

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