Discoveries of high-frequency QPOs from intermediate-mass black holes with XMM, RXTE and NICER
Abstract
Stable, twin-peak X-ray quasi-periodic oscillations (QPOs; frequency range of 100-450 Hz) in a 3:2 frequency ratio have been observed from a sample of stellar-mass black holes (e.g., Belloni et al. 2012). These frequencies scale inversely with the black hole mass as expected from general relativistic motion near a black hole. Under the black hole unification paradigm, it has been argued that intermediate-mass black holes (IMBH) should also exhibit the 3:2 ratio high-frequency QPOs, but at frequencies lower than stellar-mass black holes. Thence, such QPOs will provide an accurate measurement of IMBH masses (Abramowicz et al. 2004).Combining all the entire archival RXTE/PCA observations of the ultraluminous X-ray source (ULX) M82 X-1, we discovered stable, twin-peak X-ray QPOs at 3.3 and 5 Hz (3:2 frequency ratio). Scaling these frequencies to the oscillations of the stellar-mass black holes of known mass implies that M82 X-1's black hole is 428+-105 solar masses (Pasham, Strohmayer & Mushotzky 2014). We discovered similar 3:2 frequency ratio QPOs from another ULX NGC 1313 X-1 (0.30 and 0.45 Hz). These frequencies imply a black hole mass of 5000+-1300 solar masses in NGC 1313 X-1 (Pasham et al. 2015b). In addition to these results I will discuss some early results from NICER observations of ULXs.
- Publication:
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AAS/High Energy Astrophysics Division #16
- Pub Date:
- August 2017
- Bibcode:
- 2017HEAD...1610829R