Confronting the models of 3:2 QPOs with the evidence of near extreme Kerr black hole

TL;DR

This paper evaluates models explaining 3:2 high frequency QPOs in black holes, emphasizing the near-extreme spin of GRS 1915+105 and the challenges in unifying different models across microquasars.

Contribution

It compares various QPO models against observational evidence of near-extreme black hole spins, highlighting inconsistencies and favoring certain resonance models.

Findings

High black hole spin (a>0.9) challenges some QPO models.

Epicyclic resonance and discoseismic models are favored.

Discrepancies in spin estimates pose a problem for unified models.

Abstract

The black hole mass and spin estimates assuming various specific models of the 3:2 high frequency quasi-periodic oscillations (HF QPOs) have been carried out in Torok et al. (2005, 2011). Here we briefly summarize some current points. Spectral fitting of the spin a=cJ/GM^2 in the microquasar GRS 1915+105 reveals that this system can contain a near extreme rotating black hole (e.g., McClintock et al. 2011). Confirming the high value of the spin would have significant consequences for the theory of the HF QPOs. The estimate of a>0.9 is almost inconsistent with the relativistic precession (RP), tidal disruption (TD), and the warped disc (WD) model. The epicyclic resonance (Ep) and discoseismic models assuming the c- and g- modes are instead favoured. However, consideration of all three microquasars that display the 3:2 HF QPOs leads to a serious puzzle because the differences in the individual spins, such as a=0.9 compared to a=0.7, represent a generic problem almost for any unified orbital 3:2 QPO model.