The accreting black holes in microquasars are considered to be scaled-down versions of active galactic nuclei since both share similar emission processes and radio jets. While their larger brethren are easily detected in the gamma-rays constituting a significant fraction of the 2FGL catalog, only a handful of microquasar candidates have been unambiguously detected above 100 MeV. First, we present results from Fermi LAT observations of one of these gamma-ray detected microquasars: Cyg X-3.
Using multi-wavelength data, we illustrate the sequence of events before and after the gamma-ray flares of May 2010 and February 2011 to show that the high-energy emission is related to the appearance and disappearance of radio emission suggesting a link between accretion and the jets. Then, we extend our analysis to search for gamma-ray emission from the microquasars Cyg X-1, GRS 1915 + 105, and GX 339 - 4. Analysis of the first four years of Fermi observations of these sources indicates no significant detections > 4 σ above 100, MeV on timescales of 0.1, 1, 10,days, and longer. Upper limits are provided on the 0.1--10-GeV flux from these sources.
We discuss the orbitalphase folded gamma-ray light curves, and what the non-detections imply in the context of leptonic/hadronic models for high-energy emission. We close with prospects for increasing the sensitivity in our search for these elusive gamma-ray transients.