White Dwarfs: Proceedings of the 10th European Workshop on White Dwarfs, held in Blanes, Spain, 1721 June 1996 (Astrophysics and Space Science Library, 214)

The study of white dwarfs has been steadily growing during the last years and now is a mature field extending its influence over many others. Since white dwarfs are long lived objects, they can be used to obtain information about the history of the Galaxy. The simplicity of their structures enables them to act as precise particle physics laboratories and the extreme con­ ditions reached at their surfaces allow us to test the equation of state and to study the behavior of matter under conditions impossible to be reached in terrestrial laboratories. Nevertheless, white dwarfs are still challenging astrophysicists. Many questions, ranging from the determination of funda­ mental parameters to the evolution of their outer layers, are still waiting for a satisfactory answer. The European Workshop series on White Dwarfs started in 1974 as a con­ sequence of the effort and enthusiasm of Professor Volker Weidemann. The existing proceedings of these meetings, together with those corresponding to the lAU Colloquia held in Rochester (1979) and in Hanover (1988), provide a unique opportunity to follow the development of this field. We hope that the present volume will provide a representative snapshot of the state of the art in 1996. In this sense we are very indebted to all the participants that have sent their contributions according to the instructions (this clearly excludes everybody beyond three sigmas from the standards). Front Matter....Pages i-xxiii Front Matter....Pages 1-1 The Empirical White Dwarf Mass – Radius Relation....Pages 3-9 What We Have Learned about White Dwarfs from Studies of Novae....Pages 11-17 The Redistribution of Carbon and Oxygen in Crystallizing White Dwarfs....Pages 19-25 The Cooling of White Dwarfs and Their Internal Composition....Pages 27-33 Theoretical Models of White Dwarfs with Helium-Rich Interiors....Pages 35-41 The Electrostatic Screening of Thermonuclear Reactions in Astrophysical Plasmas....Pages 43-48 The Possible White Dwarf-Neutron Star Connection....Pages 49-55 The Impact of Evolutionary Envelope Masses on the Evolution of White Dwarfs....Pages 57-62 The Progenitors of High-Mass White Dwarfs....Pages 63-66 The Multiperiodic, Short-Period Variations of WZ Sge....Pages 67-70 Limits on Gravities of Evolved Stars, from Infrared Photometry and Binary Companions....Pages 71-74 Rotation: CO White Dwarfs Near the Chandrasekhar Limiting Mass....Pages 75-78 The Accretion-Induced Collapse of White Dwarfs Revisited in 3D....Pages 79-82 Front Matter....Pages 83-83 Towards a Luminosity Function of Hot DA White Dwarfs....Pages 85-89 White Dwarfs in M67....Pages 91-96 Monte Carlo Simulations of the Kinematics and Luminosity Function of White Dwarfs....Pages 97-104 Monte Carlo Simulations of the White Dwarf Population and Luminosity Function....Pages 105-111 Halo White Dwarfs: A Conservative Point of View....Pages 113-119 Halo White Dwarfs: A Non Conventional Scenario....Pages 121-127 HST Observations of White Dwarfs in the Globular Cluster NGC 6397....Pages 129-134 Front Matter....Pages 83-83 The Distance and Age of the Globular Cluster NGC6752 Measured by HST Observations of Cluster and Field White Dwarfs....Pages 135-141 DA White Dwarfs in the Montréal-Cambridge-Tololo Survey....Pages 143-147 Cool White Dwarf Survey using Stacked Digitised Schmidt Plates....Pages 149-152 Front Matter....Pages 153-153 Chemical Evolution of Cool White Dwarf’s Atmospheres....Pages 155-163 The Chemical Evolution of White Dwarf Stars: What the Observations Tell Us....Pages 165-171 A Critical Look at the Question of Thick vs Thin Hydrogen and Helium Envelopes in White Dwarfs....Pages 173-192 Polyatomic Carbon Molecules in Very Cool Helium-Rich White Dwarfs....Pages 193-198 Analysis of Optical, UV, and EUV Observations of G 191-B2B....Pages 199-205 New Results on PG 1159 Stars and Ultrahigh-Excitation DO White Dwarfs....Pages 207-212 Non-LTE Analyses of DO White Dwarfs....Pages 213-219 New Spectral Analyses of Pre-White Dwarfs....Pages 221-227 The Sphericity Effects in the NLTE Model Atmospheres of White Dwarfs....Pages 229-235 Heavy Elements in White Dwarf Envelopes....Pages 237-243 Lyman Spectra of Hot DA White Dwarfs....Pages 245-251 Diffusion of Silicon in the Envelopes of Hot DA White Dwarfs....Pages 253-258 Time-Dependent Diffusion Calculations for Hot Pre-White Dwarfs....Pages 259-263 Evolutionary Calculations of Carbon Dredge-Up in Helium Envelope White Dwarfs....Pages 265-267 Analysis of Optical and Ultraviolet Spectroscopy of the DAZ White Dwarf G74-7....Pages 269-272 Modeling Extreme Ultraviolet Spectra of White Dwarfs with High-Metallicity LTE Models....Pages 273-276 Extreme Ultraviolet Spectroscopy of EUVE J0720-317 and EUVE J0723-277....Pages 277-280 Front Matter....Pages 153-153 A New Dithered EUVE Spectrum of PG 1234+482....Pages 281-284 Line of Sight H and He Ionization Fractions in the Local Interstellar Medium....Pages 285-288 An Instrument for Observations of EUV Opacity Sources in G191-B2B....Pages 289-292 Metals in the Variable DA G29-38....Pages 293-296 Front Matter....Pages 297-297 In Search of the Double Degenerate Progenitors of Type IA Supernovae....Pages 299-305 The Double Degenerate Population....Pages 307-314 White Dwarf+M Dwarf Systems: A New Infrared Search....Pages 315-320 The EC14026 Stars: A New Class of Pulsating Star....Pages 321-327 Hot White Dwarfs in Non-Interacting Binaries from the ROSAT EUV Survey....Pages 329-335 HST Observations of AM Canum Venaticorum....Pages 337-343 Effects of Irradiation on the Secondary Star in a Tight Binary System, Exemplified by AM Canum Venaticorum....Pages 345-351 White Dwarfs in AM Herculis Systems....Pages 353-358 HST Synthetic Spectral Analysis of U Gem in Early and Late Quiescence: A Heated White Dwarf and Accretion Belt....Pages 359-366 WFPC2 Observations of Procyon B....Pages 367-373 Extreme Ultraviolet Light Curve and Phase-Resolved Spectroscopy of the Hot White Dwarf in V471 Tauri....Pages 375-381 Unique White Dwarfs Accompanying Recycled Pulsars....Pages 383-389 Merging of Different Mass Ratio White Dwarfs: First Moments of the 0.4-1.2 M ⊙ Case....Pages 391-394 Front Matter....Pages 395-395 New Results of Magnetic White Dwarf Spectroscopy....Pages 397-403 1-D and 2-D Calculations of Dynamo-Generated Magnetic Fields in White Dwarfs....Pages 405-411 Magnetic Field Survey of DC White Dwarfs....Pages 413-419 Front Matter....Pages 395-395 New IUE-Spectra of the Magnetic White Dwarf GRW +70°8247 and Their Interpretation....Pages 421-425 Front Matter....Pages 427-427 Convection and the ZZ Ceti Instability Strip....Pages 429-435 Wet Observations of the DAV Variable HL TAU 76: First Results....Pages 437-443 Preliminary Asteroseismology of G 29–38....Pages 445-450 Recent Advances in the Theoretical Determination of the ZZ Ceti Instability Strip....Pages 451-457 Cool DAV Asteroseismology....Pages 459-465 Overstability of G-Modes in ZZ Ceti Variables....Pages 467-472 A Continuing Spectroscopic Study of the Instability Strip of the Pulsating DB (V777 HER) White Dwarfs: The View in the Optical....Pages 473-476 The Potential of Asteroseimology for Hot, B Subdwarfs: A New Class of Pulsating Stars?....Pages 477-480 Modeling Time-Resolved Spectra of ZZ Ceti Stars....Pages 481-484 Discovery of Two New ZZ Ceti Variables....Pages 485-487 Non-Pulsating DA White Dwarfs in the DAV Region....Pages 489-492 White Dwarfs collects the contributions to the 10th European Workshop on White Dwarfs held in Blanes, Spain, in June 1996. This Workshop gathered together the majority of specialists working in this area of research and provided a precise and updated description of the state of the art of the field as well as its connections with other topics. This volume provides a snapshot of our current understanding of the origin, structure and evolution of white dwarf stars from both the theoretical and the observational points of view. It also takes into account the properties of white dwarfs as members of binary systems, stellar clusters and galactic populations.