Richard O. Gray is professor of astronomy at Appalachian State University. Christopher J. Corbally, SJ, is a vice director of the Vatican Observatory and adjunct associate professor of astronomy at the University of Arizona.

• Preface xi Important Note on Terminology and Units xv Chapter 1. The History and Philosophy of Stellar Spectral Classification 1 1.1 Early History 1 1.2 Later Developments 10 1.3 The MK Process 17 Chapter 2. An Overview of the Normal Stars 32 2.1 Introduction 32 2.2 The Spectral Sequence 32 2.3 Multicolor Photometry and Stellar Classification 44 2.4 Physical Principles Underlying the MK Sequence 50 Chapter 3. The OB Stars--Nolan R. Walborn 66 3.1 Introduction 66 3.2 The Optical 66 3.3 The Ultraviolet 75 3.4 The Infrared--Margaret M. Hanson 81 3.5 Peculiar Categories 89 3.6 X-Ray Line Spectra 102 3.7 Calibration and Astrophysical Modeling 105 Chapter 4. The B-type Stars 115 4.1 Introduction 115 4.2 Optical Classification 115 4.3 The Ultraviolet 120 4.4 Chemically Peculiar B-type Stars 123 4.5 Be Stars and B Shell Stars 135 4.6 Other B-type Emission-line Stars 143 4.7 B-type Stars in Advanced Evolutionary States 147 Chapter 5. The A-type Stars 160 5.1 Introduction 160 5.2 Optical Spectral-type Criteria 160 5.3 Ultraviolet and Infrared Classification Schemes 169 5.4 Chemically Peculiar Stars 176 5.5 Herbig Ae/Be Stars 200 5.6 A-type Stars in Advanced Evolutionary Stages 207 5.7 A-type Shell Stars 213 Chapter 6. The F-type Stars 221 6.1 Introduction 221 6.2 Optical Classification 221 6.3 Classification in the Ultraviolet and Infrared 227 6.4 Population II F-type Stars 236 6.5 Chemically Peculiar F-type Stars 244 6.6 F-type Stars in Advanced Evolutionary Stages 249 Chapter 7. The G- and K-type Stars 259 7.1 Introduction 259 7.2 Optical Classification 259 7.3 The Infrared 265 7.4 The Search for a Solar Twin; Chromospheric Activity 270 7.5 T Tauri Stars 275 7.6 Chemically Peculiar G- and K-giants 278 7.7 Population II and III Stars 281 7.8 The High Luminosity, Yellow Variables 283 Chapter 8. The M-type, S-type, and Carbon Stars 293 8.1 Introduction 293 8.2 The M-type Stars 293 8.3 The Carbon Stars 306 8.4 The S-type Stars 321 8.5 Symbiotic and Algol Stars 331 Chapter 9. M Dwarfs and L Dwarfs--J. Davy Kirkpatrick 339 9.1 Introduction 339 9.2 The Discovery of M Dwarfs and L Dwarfs 339 9.3 Spectroscopic Classification 341 9.4 Physical Interpretation of Types 362 9.4 Peculiar Objects 372 Chapter 10. The T-type Dwarfs--Adam J. Burgasser 388 10.1 Introduction 388 10.2 Recognition of the T Dwarf Class and Early Discoveries 389 10.3 T Dwarf Spectral Characteristics 391 10.4 Near-Infrared Classification 396 10.5 Optical Classification 417 10.6 Mid-Infrared Classification 425 10.7 Additional Considerations for T-Dwarf Classification 428 10.8 Beyond the T Dwarfs 434 Chapter 11. Wolf-Rayet Stars and the Luminous Blue Variables 441 11.1 The Wolf-Rayet Stars 441 11.2 Luminous Blue Variables 465 11.3 Evolutionary Connections 468 Chapter 12. Endpoints of Stellar Evolution 472 12.1 Proto-Planetary Nebulae and Planetary Nebula Nucleus Stars 472 12.2 White Dwarf Stars 472 12.3 Novae 482 12.4 Supernovae 497 Chapter 13. Further Techniques 507 13.1 Introduction 507 13.2 Composite Spectra 507 13.3 Classification Systems in the Thermal Infrared 515 13.4 Other Classification Systems 522 13.5 Automated Methods of Spectral Classification 525 13.6 Low Dispersion Techniques and Natural Groups 529 Glossary 541 Appendix A: MK Standard Stars 555 Appendix B: Calibrations of the MK System 565 Appendix C: The Book Website 571 General Index 573 Object Index 585

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