RAPID INFRARED FLARES IN GRS-1915- EVIDENCE FOR INFRARED SYNCHROTRON EMISSION(105 )

We report imaging photometry of the radio jet black hole candidate sou rce GRS 1915+105 in the infrared K band. The observations reveal rapid infrared hare events on time-scales of less than an hour. These event s are strikingly similar to those regularly observed in radio monitori ng at 15 GHz. Furthermore, when dereddened, the infrared events have c omparable amplitudes to the radio oscillations, and observations at 15 GHz made similar to 8 h after our infrared observations reveal that t he source was indeed displaying radio oscillations at this time. We su ggest that we have observed infrared synchrotron emission from this so urce. We estimate the equipartition magnetic field and power required to accelerate the particles for the repeated radio events, and find bo th to be orders of magnitude greater than those estimated for any othe r X-ray binary. Comparison of events at 15 GHz and 2.2 mu m suggests t hat the, dominant loss mechanism is adiabatic expansion, which in turn implies that each event corresponds to a small ejection of material f rom the system.