White Dwarf Atmospheres and Circumstellar Environments E-Book

• Herausgeber: Wiley-VCH
• Kategorie: Lebensstil
• Sprache: Englisch
• Veröffentlichungsjahr: 2012

Seitenzahl: 462

Beschreibung

Written by selected astronomers at the forefront of their fields, this timely and novel book compiles the latest results from research on white dwarf stars, complementing existing literature by focusing on fascinating new developments in our understanding of the atmospheric and circumstellar environments of these stellar remnants. Complete with a thorough refresher on the observational characteristics and physical basis for white dwarf classification, this is a must-have resource for researchers interested in the late stages of stellar evolution, circumstellar dust and nebulae, and the future of our own Solar System.

Leseprobe

Contents

Cover

Half Title page

Title page

Copyright page

Dedication

Preface

List of Contributors

Chapter 1: Hot White Dwarfs

1.1 Introduction

1.2 Remarks on the Spectroscopic Classification of Hot White Dwarfs

1.3 The Hot DA Stars

1.4 The PG 1159 Stars

1.5 DO White Dwarfs

1.6 DB White Dwarfs

1.7 Hot DQ White Dwarfs

1.8 Conclusion

Acknowledgments

References

Chapter 2: Cool White Dwarfs

2.1 White Dwarf Cosmochronology

2.2 Cool White Dwarf Atmospheres

2.3 Identification of Large Samples of Cool White Dwarfs

2.4 Observational Properties of Cool White Dwarfs

2.5 Spectral Evolution of Cool White Dwarfs

2.6 Ages for Individual White Dwarfs

2.7 The White Dwarf Luminosity Function

2.8 Halo White Dwarfs

2.9 Conclusions and Future Prospects

References

Chapter 3: Stars with Unusual Compositions: Carbon and Oxygen in Cool White Dwarfs

3.1 Introduction

3.2 DQ White Dwarfs

3.3 Carbon and Oxygen in DBQ White Dwarfs

3.4 Hot DQ White Dwarfs

3.5 Conclusion

Acknowledgments

References

Chapter 4: Planets Orbiting White Dwarfs

4.1 Introduction

4.2 Expectations

4.3 Detecting Radiation from the Planets

4.4 Evidence for Minor Planets

4.5 Timing

4.6 Mesolensing

4.7 Transits

4.8 Prospects for the Future

References

Chapter 5: White Dwarf Circumstellar Disks: Observations

5.1 Introduction

5.2 History and Background

5.3 Pre-Spitzer and Ground-Based Observations

5.4 The Initial Impact of Spitzer

5.5 The Next Wave of Disk Discoveries

5.6 Studies and Statistics

5.7 Related Objects

5.8 Outlook for the Present and Near Future

Acknowledgments

References

Chapter 6: The Origin and Evolution of White Dwarf Dust Disks

6.1 Introduction

6.2 Orders of Magnitude around a White Dwarf

6.3 Structure and Evolution of a White Dwarf Dust Disk

6.4 Origins of White Dwarf Dust Disks

6.5 Conclusion

References

Chapter 7: Planetary Nebulae around White Dwarfs: Revelations from the Infrared

7.1 Introduction: Expectations of Nebulae around White Dwarfs

7.2 Planetary Nebulae around White Dwarfs

7.3 High-Excitation Nebulae around Hot White Dwarfs

7.4 Mid-Infrared Emission from Circumstellar Nebulae of White Dwarfs

7.5 Conclusion

References

Acknowledgments

Index

Object Index

White Dwarf Atmospheres and Circumstellar Environments

Edited by D. W. Hoard

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The Editor

Dr. D.W. HoardSpitzer Science CenterCalifornia Institute of TechnologyPasadena, USA

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© 2011 WILEY-VCHVerlag GmbH & Co. KGaA,Boschstr. 12, 69469 Weinheim, Germany

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Where are the stars, pristine as great ideas? Behind clouds the heavens saturate with luminous dust…

(“Where Are The Stars Pristine” from Palladium by Alice Fulton. Copyright 1987 by Alice Fulton. Used with permission of the University of Illinois Press.)

Preface

White dwarf stars play a key role in a wide variety of astrophysically important scenarios. They not only provide a glimpse into the distant future of our own Sun, but are the evolutionary endpoints of the majority population of low mass stars in the Galaxy. As relic cores of normal stars, white dwarfs provide insights into stellar evolution, and expose material created during a stellar lifetime of nuclear burning to direct examination. Binary stars containing white dwarfs are linked to the chemical enrichment of the interstellar medium (via nova explosions), and are laboratories to probe the processes of mass transfer and accretion that power the central engines of quasars and govern the formation of stars and planetary systems. Type Ia supernovae, used as standard candles for measuring cosmological distances, are believed to result from accretion onto white dwarfs and/or white dwarf-white dwarf collisions.

In many ways, white dwarfs are relatively “simple” and well understood objects: partially crystallized balls of mostly electron-degenerate carbon and oxygen, with the mass of a sun packed into the volume of an earth.1) They do not produce any new energy, but slowly radiate away the trapped energy of billions of years of nuclear fusion. We can “listen” to the ringing of acoustic waves in their interiors, and produce physically realistic model spectra that are almost indistinguishable from the real thing. However, in recent years, new discoveries have made it clear that the immediate environments of white dwarfs, from their photospheres out, can be – and often are – as interesting as the white dwarfs themselves. The flotsam and detritus surrounding white dwarfs, largely undetectable or overlooked during most of the last 100 years of astronomical observations of white dwarfs, turn out to have their own tales to tell about the past, present, and future of these objects.

During approximately the last decade, advances in observational techniques and detector technology have opened up new regimes of wavelength and sensitivity to the study of white dwarfs. In particular, satellite observatories such as the Hubble and Spitzer Space Telescopes have enabled dramatic new discoveries about white dwarfs. For example, observations with Spitzer have shown that the presence of dusty debris disks around white dwarfs, which can often only be detected in the mid-infrared, is fairly common. Meanwhile, ever more sophisticated model atmosphere calculations have enabled the increasingly realistic generation of white dwarf synthetic spectra that can be used as diagnostic comparisons with observations.

The tale of Subrahmanyan Chandrasekhar is well known among those astronomers who study white dwarfs: as a 19-year-old student, on a long sea voyage to England in 1930 to begin his graduate studies at Cambridge University, he whiled away his time by modifying a theory proposed by his soon-to-be graduate advisor, the British astronomer Ralph Fowler, to include special relativistic effects. By combining quantum mechanics and Einsteinian relativity, Chandra determined that the mass of a star that can end its life as a white dwarf (and, hence, the mass of a white dwarf itself) has an upper limit, which is now named in his honor. In part for this work, Chandra was awarded the Nobel Prize in Physics in 1983 (shared with William A. Fowler) “for his theoretical studies of the physical processes of importance to the structure and evolution of the stars.”2) The preparation of this book coincided with the 100th anniversary of both the birth of Chandra and the classification of the first white dwarf, 40 Eridani B – auspicious omens for a book about white dwarf stars.

The chapters in this book will not present detailed treatises on the formation or internal structure of white dwarfs themselves, topics which have been extensively covered in other works (from Chandra onward). Nor will they focus on white dwarfs as members of detached or interacting binary star systems. Instead, the focus of this book is shifted somewhat away from the white dwarfs themselves, and onto the relatively new and fascinating topics of peculiar atmospheric compositions and the dust, nebulae, and (potentially) planets that surround white dwarfs. We will start in the geometrically thin, nondegenerate atmospheres of the white dwarfs and move outward into their circumstellar environs.

Acknowledgments

The cover of this book shows the spectral energy distribution of the dusty white dwarf GD 16 from the optical to the mid-infrared, illustrating the infrared excess, along with a depiction of the white dwarf and its circumstellar disk. Robert Hurt (Spitzer Science Center) kindly made some minor modifications to the original image from the Spitzer press release sig09-002 by Jay Farihi3) for use on this cover. The original image is courtesy of NASA/JPL-Caltech.

The rapid pace of advances in the understanding of white dwarf stars and their circumstellar environments, especially over the course of the last ten years, would not have been possible without the contributions of many theorists and researchers, as well as the availability of data from numerous surveys and data archives. On behalf of myself and the other authors, I would like to acknowledge the following facilities that have been of particular (although not exclusive) usefulness in exploring the atmospheres and circumstellar environments of white dwarfs as discussed in this book (listed in order by wavelength regime, from short to long):

1. The NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer, FUSE, which was operated for NASA by the Johns Hopkins University under NASA contract NAS5-32985.

2. The NASA Galaxy Evolution Explorer, GALEX, which is operated for NASA by the California Institute of Technology under NASA contract NAS5-98034.

3. The International Ultraviolet Explorer satellite, which was a collaboration among three groups: NASA, the European Space Agency (ESA), and the United Kingdom’s Science and Engineering Research Council (SERC; now called the Particle Physics and Astronomy Research Council, PPARC).

4. The NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

5. The Digitized Sky Surveys, which were produced at the Space Telescope Science Institute under US Government grant NAG W-2166. The images of these surveys are based on photographic data obtained using the Oschin Schmidt Telescope on Palomar Mountain and the UK Schmidt Telescope. The plates were processed into the present compressed digital form with the permission of these institutions. The National Geographic Society – Palomar Observatory Sky Atlas (POSS-I) was made by the California Institute of Technology with grants from the National Geographic Society. The Second Palomar Observatory Sky Survey (POSS-II) was made by the California Institute of Technology with funds from the National Science Foundation, the National Geographic Society, the Sloan Foundation, the Samuel Oschin Foundation, and the Eastman Kodak Corporation. The Oschin Schmidt Telescope is operated by the California Institute of Technology and Palomar Observatory. The UK Schmidt Telescope was operated by the Royal Observatory Edinburgh, with funding from the UK Science and Engineering Research Council (later the UK Particle Physics and Astronomy Research Council), until 1988 June, and thereafter by the Anglo-Australian Observatory. The blue plates of the southern Sky Atlas and its Equatorial Extension (together known as the SERC-J), as well as the Equatorial Red (ER), and the Second Epoch [red] Survey (SES) were all taken with the UK Schmidt.

6. The Sloan Digital Sky Surveys, SDSS and SDSS-II. Funding for the SDSS and SDSS-II was provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the US Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS was managed by the Astrophysical Research Consortium for the Participating Institutions.

7. The Two Micron All Sky Survey, 2MASS, which was a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation.

8. The Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA.

Pasadena, California, 2011

D. W. Hoard

1) This is an extreme physical situation that was eloquently described by Arthur Stanley Eddington in a lecture transcribed in his 1927 book Stars and Atoms (Oxford: Clarendon Press, p. 50), as “a density much transcending our terrestrial experience” and, somewhat more pithily, “a tight squeeze”. Eddington also relates the initial reaction to the inferred physical properties of the second known white dwarf, Sirius B: “We learn about the stars by receiving and interpreting the messages which their light brings to us. The message of the Companion of Sirius when it was decoded ran: ‘I am composed of material 3000 times denser than anything you have ever come across; a ton of my material would be a little nugget that you could put in a matchbox.’ What reply can one make to such a message? The reply which most of us made in 1914 was – ‘Shut up. Don’t talk nonsense.’”.

2)http://nobelprize.org (15 June 2011)

3)http://www.spitzer.caltech.edu/images/2054-sig09-002-Emission-from-the-White-Dwarf-System-GD-16 (9 May 2011)

List of Contributors

You-Hua Chu

Astronomy Department

University of Illinois at Urbana-Champaign

1002 W. Green Street

Urbana, IL 61801

USA

John H. Debes

NASA’s Goddard Space Flight Center

Greenbelt, MD 20771

USA

Rosanne Di Stefano

Harvard-Smithsonian Center for Astrophysics

60 Garden Street

Cambridge, MA 02138

USA

Patrick Dufour

Département de Physique

Université de Montréal

C.P. 6128

Succursale Centre-Ville

Montréal, QC H3C 3J7

Canada

Jay Farihi

Department of Physics and Astronomy

University of Leicester

Leicester, LE1 7RH

United Kingdom

Mukremin Kilic

Harvard-Smithsonian Center for Astrophysics

60 Garden Street

Cambridge, MA 02138

USA

Edward M. Sion

Department of Astronomy and Astrophysics

Villanova University

Villanova, PA 19085

USA