Sagittarius A* and the Galactic Pulsar

High resolution very long baseline interferometry (VLBI) images of nearby massive black holes have the power to address fundamental questions about the physics of black holes.  This includes the most accurate constraints on the mass density of the black hole, detection of the black hole spin, and exploration of extensions to general relativity (GR).  In particular, Event Horizon Telescope (EHT) observations will probe Sgr A* and M87, the two sources with the largest angular diameter black holes on the sky, over the coming years with increasing sensitivity and accuracy in imaging.  Unfortunately, we do not fully understand the physical processes that are driving accretion and outflow in these sources.  Our lack of understanding in this domain may prevent us from separating astrophysical processes from the underlying black hole physics.  We do not know, for instance, whether a jet or outflow is present in the case of Sgr A*, what effect different modes of accretion have upon the source images that we will obtain, or how stable accretion flows are.  Therefore, to address the fundamental black hole physics questions, we need to develop a deeper knowledge of the astrophysics of these sources.  In recent years, the periastron passage of the G2 gas cloud with Sgr A* at ~1000 Schwarzschild and the discovery of the Galactic Center magnetar have provided us an unprecedented opportunity to study the GC in new ways.  I describe here observations from millimeter to X-ray wavelengths that enable us to create the necessary context for understanding physics at a few Schwarzschild radii. 

Geoffrey Bower
Chief Scientist for Hawaii Operations
KIAA-PKU Auditorium
Ran Wang
Monday, November 6, 2017 - 4:00pm to 5:00pm