Cyclical Variability in Stellar Winds

It is well known that stellar winds are variable. Recent investigations show that the observed fluctuations are often cyclical in nature. This property seems to be shared by the winds of cool and hot stars, even though the physical mechanisms driving these winds are fundamentally different. The time was ripe for astrophysicists studying different types of stars, but applying very similar models, to present the state of the art in a concise form. The proceedings will provide a useful, up-to-date overview of the observations, interpretation, and modelling of the time-dependent mass outflows from a wide variety of stars, including young, pre-main-sequence objects, solar-type stars, red supergiants, and hot, massive stars.

Klappentext

It is well known that stellar winds are variable, and the fluctuations are often cyclical in nature. This property seems to be shared by the winds of cool and hot stars, even though their outflows are driven by fundamentally different physical mechanisms. Since very similar models have been proposed to explain the cyclical wind variations observed in a wide variety of stars, the time was ripe for astrophysicists from many different sub-disciplines to present the state of the art in a concise form. The proceedings will provide a useful, up-to-date overview of the observations, interpretation, and modelling of the time-dependent mass outflows from all sorts of stars.

Inhalt

1. Setting the Stage: Wind Acceleration Mechanisms.- Acceleration Mechanisms for Cool Star Winds.- Thirty Years of Radiation-Driven Hot Star Winds.- A Thermo-Radiatively Driven, Analytical 2-D Model for Stellar Outflows.- Using ISO to Probe the Acceleration of Wolf-Rayet Winds.- A Critical Evaluation of Mass-Loss Rates and Wind Properties of Evolved Late-Type Stars.- Variable Winds in Yellow Supergiants.- Numerical Simulations of Dust-Driven AGB Winds: A Two-Fluid Model.- YSO Winds and Jets: Mechanisms and Variability.- On the Origin of Relativistic Winds from Accreting Stars.- 2. Observations of Cyclical Wind Variability.- The Solar Wind in Three Dimensions.- Observations of Wind Variability in Cool Stars.- Variations of Winds of Cool Giants in Ha.- Variability of the Circumstellar Shell of 89 Herculis.- Wind Variability in the Hypergiant HR 8752.- Variable Dust Emission Observed in Miras.- Variable Water Maser Emission from Circumstellar Disks.- Systematic Variability in OB-Star Winds.- Cyclical Variability in O-Star Winds (The H? Project).- Cyclic Polarization Variability of Bright O Stars.- Confirmation of a 2.3-Day Periodicity in the Wolf-Rayet Star WR 134: A Twin of EZ CMa?.- No Need for a White & Becker Disk-Like Wind in WR 140.- Phase Shifts Between Cyclical Spectral Parameters of P Cygni.- Long-Term Spectroscopic Variability of ? Carinae.- A Kinematic Study of the LBV Nebula Around ? Carinae.- Cyclic Variability in BA-Type Supergiants.- Rotational Modulation of B Supergiant Winds.- Expression of Turbulence and the Variability of Stellar Winds in Resonance Line Profiles.- Understanding A-Type Supergiants: Visible and Ultraviolet Spectral Variability.- Cyclic Variability in Be Star Winds: The Observations.- Stellar Wind Variability of Be Star FY CMa.- Fundamental Parameters for Seven Be Stars.- Wind and Jets in the Be Star 4 Herculis.- Variability of Be Stars Using Hipparcos Photometry.- The Interrelation Between Long-Term Cycles and Rapid Variations in Be Stars: A Photometric View.- Long-Term Cyclical Circumstellar Changes and He I lpv in the Be Star EW Lacertae.- Wind Variability in PMS-Stars.- Wind and Accretion Variability in T Tauri Stars.- Hot Spots on Classical T Tauri Stars with High Mass-Loss Rates.- Anisotropic Outflows from Herbig Ae/Be Stars.- Variability in the Wind of the FU Ori Object Z Canis Majoris.- A Variability Study of High-Resolution Profiles of DL Tauri.- The UV Variability of T Tauri Stars.- Spectroscopic Investigations of Cyclical Variability in the Gaseous Envelopes of Early-Type Emission-Line Stars.- Polarimetric Studies of Cyclic Phenomena in the Circumstellar Envelopes of the Young Herbig Ae/Be Stars.- Comparing Observations of Cyclical Variability in Hot- and Cool-Star Winds.- Nitrogen v in the Wind of the Pre-main Sequence Herbig Ae Star AB Aurigae.- 3. Processes Affecting the Emergence of the Stellar Wind.- Line-Profile Variability as a Diagnostic for Non-radial Pulsation Mode Identification.- NRP in Light and Colour: Diagnostic Value.- Nonradial Pulsations in Relation to Wind Variability in Early-Type Stars.- Predicting the Outbursts of the Be Star ? Cen.- Surface Magnetic Fields of Non-degenerate Stars.- The Hanle Effect as a Probe of Stellar Magnetic Fields.- Photometric Monitoring of Spotted T Tauri Stars.- The Activity Cycle and Interaction of Stellar Winds in the Capella System.- H? Line-Profile Variability in Chromospherically Active Stars.- Cyclical Variability in the Solar Wind.- Luminous Magnetic Rotator Theory.- Periodic Variability of ?1 Ori C.- Rotating Loops in the Atmosphere of Rigel (? Orionis A).- Constraints on Wind Structure from the Infrared and Radio Continuum of Hot Stars.- Clumping-Corrected Mass-Loss Rates of WR Stars: Dependence on Stellar Parameters.- Formation of Clumps in the Wind of Wolf-Rayet Stars by Thermal Instability and Alfvén Waves.- 4. Modelling Cyclical Variability in Stellar Outflows.- Understanding the Solar Wind.- The Solar Wind Modelled by Exact MHD Solutions.- Time-Dependent Behavior of Cool-Star Winds.- Atmospheric Dynamics and Stellar Winds of Long-Period Variables.- Pulsation and Stellar Winds: Some Lessons Learned from Dynamical Models of the Atmospheres of Cool Stars.- The Mass-Loss Rate of C-Rich Mira Stars.- Molecular and Dust Features in Mass-Losing AGB Stars: Models and ISO Observations.- Variability of CO Line Profiles in AGB Stars.- Temporal Variations of CO Infrared Lines in Cool-Star Winds.- Cyclical Variability in MHD Disk Winds.- Accretion Mass-Loss Relation and Variability in T Tauri Stars.- The Wind of FU Orionis: Modelling the Atmosphere.- Numerical Modeling of Anisotropic Stellar Winds in Herbig Ae/Be Stars.- Modelling Variability in Hot-Star Winds.- Semi-empirical Modelling of Cyclical Ha Line Profile Variability of O Stars.- Long-Term Cyclic V/R Variations in Be Stars.- Large, Oscillating Be Star Circumstellar Disks.- Variabilities in Be-Star Disks in Be/X-Ray Binaries.- V/R Variability in Be/X-Ray Binaries.- 5. The Musicos 1996 Campaign.- MUlti-SIte COntinuous Spectroscopy: Previous MUSICOS Campaigns.- MUSICOS Observations of SU Aurigae.- Short-Term Spectroscopic Variability in the Pre-Main-Sequence Herbig Ae Star AB Aur During the MUSICOS 96 Campaign.- Flares and Circumstellar Material Around the Fast-Rotating Giant FK Comae.- First Results of the November 1996 MUSICOS Campaign on the 07.5III Star ? Persei.- MUSICOS 1996 Campaign on the ? Scuti Star V480 Tau.- 6. Future Perspective.- Metallicity Dependence of Stellar Outflows and Their Variability.- Non-LTE Departure Coefficients of Hydrogen.- Outflows in Quasars: Radiative Acceleration and Variability.- Author Index.