Physics of Luminous Blue Variables

A strange field of speculation is opened by this phenomenon ... here we have a star fitfully variable to an astonishing extent. and whose fluctuations are spread over centuries. apparently in no settled period. and with no regularity of progression. What origin can we ascribe to these sudden flashes and relapses? What conclusions are we to draw as to the comfort or habitability of a system depending for its supply of light and heat on so uncertain a source? -- J. F. W. Herschel! We can imagine, at least, that the study of Luminous Blue Variable stars began as the official court astrophysicists of Eridu speculated about a new 5000 years ago first-magnitude star which persisted in their southern sky for several years.2 After that the topic languished for a while, but now it has been renewed following recent observations by Blaeu (P Cygni, c.1600) and Herschel (1] Argus, c.1840) ... -- More soberly, it is only within the past few years that we have begun to understand LBV's and to recognize their coherence as a class. Thus only a minority of astronomers are familiar yet with this relatively new topic, whose potential impli­ cations are of great interest (see below). One purpose of this book, we hope, will be to provide an accessible overview of the subject for interested astronomers and astrophysicists in general.

Inhalt

Section I: Main Papers, General Discussions, and Two Panel Discussions.- A. General background.- What are LBV's? - Their characteristics and role in the upper H-R diagram.- On the evolutionary status and instability mechanism of the Luminous Blue Variables.- Evolutionary diagnostics of LBV spectra and systems in the LMC.- The distribution of types of Luminous Blue Variables.- Ages of Luminous Blue Variable candidates from their stellar and nebular environment.- An ultraviolet view of the Luminous Blue Variables.- Photometric variability of Luminous Blue Variables in quiescent state.- Model atmospheres and quantitative spectroscopy of luminous blue stars.- The H-R diagrams of the LMC and SMC.- B. Quiescent vs. eruptive states, and related matters.- ?Normal? LBV eruptions á la S Doradus.- Plinian eruptions á la Eta Carinae.- Changes in the atmospheric structure of LBV's during eruptions.- The B[e] stars.- Modeling mass loss from B[e] stars.- Luminous Blue Variables need not be blue.- Mass ejections from the G-type hypergiant HR 8752.- Mass loss from Luminous Blue Variables.- C. Circumstellar ejecta and the possibility of bipolar or axial symmetry.- Circumstellar ejecta around LBV?s.- High-resolution coronographic imaging of AG Carinae.- Infrared observations of circumstellar ejecta around Luminous Blue Variables 165.- The formation of shells in the wind from P Cygni.- Close binary models for Luminous Blue Variable stars.- D.Physical mechanisms for eruptions, and connections with other stars.- The role of radiation pressure in LBV atmospheres.- The role of rotation in Luminous Blue Variables.- Atmospheric dynamics of luminous stars.- Theoretical relations between LBV?s and other stars.- Observational connections between LBV?s and other stars, with emphasis on Wolf-Rayet stars.- Panel discussion: The instability mechanism.- Panel discussion: Observational connections and future observations.- Section II: Poster Papers, A Brief List of Catalogs, and Index.- P Cygni: The star that started it all.- The wind of P Cygni.- A source for mass-loss instabilities in LBV's - the case of P Cygni.- The ionization and thermal balance in P Cygni's wind revisited.- Variable flux of P Cygni in continuum and spectral lines.- Optical and UV investigation of the envelope of AG Carinae.- AG Carinae: Variability, extinction, distance and luminosity.- The optical micro-variations of the S Dor-type stars AG Car and HR Car.- On the periodicity of Hubble-Sandage objects in M31.- Eta Carinae: UV constraints on possible models. The close binary hypothesis.- High-resolution emission line profiles in blue luminous stars.- Analysis of LBV circumstellar envelopes using Fe II lines.- On the interpretation of emission wings of balmer lines in LBV's.- Atmospheric models for LBV's at minimum and maximum states.- Atmospheric parameters and accelerations in the outer parts of luminous hot stars.- NLTE analysis of R84.- Physics of instabilities in radiatively driven stellar winds.- Far-infrared circumstellar debris shells: Clues to the evolution of massive stars?.- High-dispersion spectroscopy of the B[e] supergiant S III.- Slash stars: Two types, two scenarios?.- Blobs in the winds of Wolf-Rayet stars.- LSS4005 and NaSt 1, two Galactic Ofpe/WN or B[e] objects 301.- Brief abstracts of additional poster papers.