Monitoring the Hard X-ray/Soft Gamma-Ray Sky with Fermi/GBM - The First Four Years

The Gamma ray Burst Monitor (GBM) on board Fermi Gamma-ray Space Telescope has been providing continuous data to the astronomical community since 2008 August 12. We have applied the Earth Occultation Technique (EOT) to monitor hard x-ray and soft gamma-ray sources in the 10-1000 keV energy range. The monitoring capability of GBM is unique in that it covers such a wide energy range, complementary to other monitoring instruments, and is the only monitoring instrument operating above about 100 keV. We recently published a 3-year catalog of 209 sources, 99 of which were positively detected above 10 keV and 9 of which were detected above 100 keV. Using the EOT, we also discovered the decrease in the Crab Nebula flux that occurred between the middle of 2008 and the middle of 2010. We continue to monitor transient and/or active sources such as Cygnus X-1, which has been in a period of increased activity for the last 2010. We have also developed an imaging technique that allows us to search for sources that need to be added to our monitoring catalog. We present highlights of the 3-yr catalog as well as an update on the current status of the monitoring catalog, an update on the Crab Nebula light curve and spectrum, light curves and spectra of Cygnus X-1 during its activity, and images from the EOT all-sky imaging.