High-frequency QPOs (HFQPOs; 40–450 Hz) have been detected in seven sources (5 BHBs and 2 BHCs). These oscillations are transient and subtle (), and they attract interest primarily because their frequencies are in the expected range for matter in orbit near the ISCO for a ∼10 BH.
Source: Remillard & McClintock 2006 ┃ X-Ray Properties… ⚬𓂃
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