Sera Markoff1, Heino Falcke2, Feng Yuan2 and Peter Biermann2
1 Massachusetts Institute of Technology, Center
Research, 77 Massachusetts Ave., Rm. NE80-6035, Cambridge, MA 02139, USA
2 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
E-mail contact: email@example.com
See: A&A, 379, L13-L16 (2001)
Last year, the X-ray mission Chandra observed a factor of 50 flaring in the Galactic Center supermassive black hole candidate Sgr A*. The smallest timescale of ~60 seconds argues for an origin within ~40 rg of the central engine, which narrows the source down to the inner regions of either the accretion flow or a jet outflow. Because the variability in the radio has never shown similar levels of flaring over its observed history, a simple jump of order 50 in the accretion rate is likely not the cause of the fluctuations. We argue that additional electron heating near the base of a jet can account for the flaring which, depending on the underlying physical mechanism, predicts significantly different simultaneous multi-wavelength behavior. For the case of direct heating of the thermal electrons by a factor of a few, the flare would be a result of increased synchrotron-self Compton emission. Non-thermal particle acceleration in the jet, on the other hand, could account for the flare via high-energy synchrotron emission. We discuss these mechanisms in the context of the jet model, and the respective signatures which would allow us to distinguish between them in future flaring events.