Fulvio Melia is Professor of Physics and Astronomy at the University of Arizona and Associate Editor of the "Astrophysical Journal Letters". His books include "The Black Hole at the Center of Our Galaxy" (Princeton), "The Edge of Infinity: Supermassive Black Holes in the Universe", and "Electrodynamics".

• Foreword vii Preface xiii CHAPTER 1: The Galactic Center 1 1.1 Discovery of Sagittarius A* 2 1.2 Radio Morphology of the Central Region 5 1.3 X-ray Morphology of the Central Region 10 1.4 Sagittarius A East 17 CHAPTER 2: The Radio Source Sagittarius A* 25 2.1 Position of Sagittarius A* 27 2.2 Proper Motion 32 2.3 Structure as a Function of Frequency 37 CHAPTER 3: Sagittarius A*'s Spectrum 42 3.1 The Radio Spectrum 42 3.2 Linear and Circular Polarization 46 3.3 Infrared Observations 55 3.4 X-ray Observations 58 3.5 Observed High-Energy Characteristics 65 CHAPTER 4: Variability 71 4.1 Short-Term Variability in the IR and X-rays 71 4.2 Long-Term Variability in the Radio 81 CHAPTER 5: The Central Star Cluster 86 5.1 The Stellar Cusp Surrounding the Black Hole 87 5.2 Stellar Constituents and Dynamics 101 5.3 Stellar Orbits and the Enclosed Mass 109 CHAPTER 6: The Four-Dimensional Spacetime 114 6.1 The Flat Spacetime Metric 114 6.2 Relativistic Transformation of Physical Laws 126 6.3 Accelerated Frames 132 6.4 General Relativity 137 6.5 Particle Orbits and Trajectories 140 6.6 The Kerr Metric 149 CHAPTER 7: Mass Accretion and Expulsion 156 7.1 Sagittarius A*'s Gaseous Environment 158 7.2 Bondi-Hoyle Capture from Distributed Sources 162 7.3 Accretion Close to Sagittarius A* 165 7.4 Magnetic Field Dissipation 167 7.5 A Compact Magnetized Disk 176 7.6 Expulsion of Matter 204 CHAPTER 8: Flares 226 8.1 Flare Physics 226 8.2 Periodicity 234 8.3 General Relativistic Flux Modulations 240 CHAPTER 9: Strong Field Physics 245 9.1 Spin-Induced Disk Precession 246 9.2 Microlensing 251 9.3 Imaging the Shadow of the Black Hole 259 References 265 Index 287

"Combining large scale astronomical observations with the careful reasoning of physics leads to the widely encompassing field of astrophysics. Apparently, the physical laws that rule interactions on Earth also rule the actions across our university. Fulvio Melia takes this consideration to task in his book The Galactic Supermassive Black Hole. Within the book, the equations bring reason to some very murky observations and sharpen our view of the heavens."--Universe Today "Melia has prepared his book as a logically arranged and comprehensive compilation of our current knowledge...For those who wish to become familiar with the current thinking, this is the book to read; it is the only complete overview of the subject."--A. Spero, Choice