| Ever since its discovery over 30 years ago, the radio source Sgr A* has been suspected of being associated with a supermassive black hole at the center of our Galaxy. Motivated by detections of extreme variability from Sgr A* at X-ray wavelengths, this dissertation uses a variety of observational and analysis techniques to analyze twelve years of infrared observations focused on the Galactic Center using the Keck 10 m telescopes. From speckle and natural guide star adaptive optics (AO) two-micron observations collected from 1995--2004, I present detection limits for Sgr A*'s IR emission from 36 individual observations. Collectively, these detection limits establish a dereddened upper limit of 19 mJy (Kobs = 14.73 mag) for three-hour outbursts occurring on the order of once per day and rule out the possibility of the outbursts being created by a model involving direct heating of thermal electrons unless additional restrictions are applied. Additionally, the single deepest image of the data set limits Sgr A*'s quiescent dereddened IR emission to be below 2 mJy (Kobs = 17.17 mag). With advancing technology, infrared detections of Sgr A* quickly emerged and revealed a variable source with similar outburst durations as the X-ray outbursts but occurring much more frequently. Using results from the Keck laser guide star AO system, I present the first time-series of Sgr A*'s broadband infrared color measurements throughout several outbursting events, including the largest detected IR outburst to date. These observations reveal that Sgr A*'s spectral index of alpha = -0.6 +/- 0.2 (Fnu ∝ nu alpha) is independent of intensity, wavelength, time, or outburst. When coupled with X-ray observations showing a similar, and also constant, spectral index in the X-ray domain, these results imply that while the X-ray emission is most likely from synchrotron self-Compton scattering of the electron energy distribution responsible for the infrared emission, it cannot be coupled to electrons at the same energy regime and most likely originates from electrons with higher energies than those responsible for the IR outbursts. Finally, I present the results of five years of AO photometric monitoring of Sgr A* in order to study the statistical properties of IR outbursts. These results suggest that while the X-ray outbursts have been well established at ∼1 moderate-sized ( ≳ 10x quiescent level) outburst per day, the IR outburst rate is nearly a factor of 10 higher. |
