Complex Phase Lag Behaviors of the 0.5 - 10 Hz Quasi-Periodic
Oscillations in GRS 1915+105
Lin, D., Smith, I. A., Liang, E. P., Böttcher, M.
Through studying the hard lags between the soft (3.3-5.8 keV) and hard
(13.0-41.0 keV) photons of the 0.5-10 Hz quasi-periodic oscillations
(QPOs) in GRS 1915+105, we have classified them into three types: 0.5-2.0,
2.0-4.5, and 4.5-10 Hz QPOs.
They are closely related to different temporal and spectral states.
The first type of QPO (0.5-2 Hz) has positive hard lags at both the QPO
fundamental and first harmonic frequencies.
These QPOs were observed in the quiescent soft state.
The second type of QPO (2-4.5 Hz) was also detected in the quiescent soft
state; these QPOs have opposite signs of hard lags at the QPO fundamental
and first harmonic frequencies.
The third type (4.5-10 Hz), which showed up in medium soft quiescent/outburst
states, does not have significant higher harmonic peaks.
There is a smooth transition between these three types of QPO behaviors.
We did not detect 0.5-10 Hz QPOs in the very soft state.
We discuss some of the implications of these results.
Status:
2000, ApJ, 543, L141.
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