The high-frequency QPOs in GRS 1915+105

We analyzed two 1996 observations of the Galactic Microquasar GRS 1915+105 taken with the Proportional Counter Array on board the Rossi X-ray Timing E xplorer. We focus on the properties of the high-frequency QPO as a function of the "dip" oscillations, a factor of 1000 slower. In one observation, 19 96 May 5th, we find that the energy spectrum of the QPO at similar to 65 Hz changes drastically between the high-intervals and the dips, hardening dur ing the dips to the point that the QPO peak is no longer detected at low en ergies. In the second observation, 1996 May 14th, although it has similar o verall characteristics, the 65 Hz QPO is not seen, but another broader QPO peak appears at 27 Hz, only during the dips. This peak is too weak to obtai n reliable information about its spectrum. Our results indicate that the pr esence/absence of high-frequency features in this enigmatic source are inti mately linked to the slower oscillations and variations that happen on long er time scales.