Discovery of a 7 mHz X-Ray Quasi-periodic Oscillation from the most Massive Stellar-mass Black Hole IC 10 X-1

TL;DR

This paper reports the discovery of a 7 mHz X-ray quasi-periodic oscillation from the black hole binary IC 10 X-1, providing insights into its accretion processes and QPO classifications.

Contribution

The study presents the first detection of a 7 mHz QPO in IC 10 X-1, expanding the understanding of low-frequency QPOs in stellar-mass black hole systems.

Findings

QPO detected at > 4.33 sigma confidence

QPO fractional amplitude ~11% rms, Q factor ~4

QPO may be linked to known categories like heartbeat or dipper QPOs

Abstract

We report the discovery with XMM-Newton of an approximately 7 mHz X-ray (0.3-10.0 keV) quasi-periodic oscillation (QPO) from the eclipsing, high-inclination black hole binary IC 10 X-1. The QPO is significant at > 4.33 sigma confidence level and has a fractional amplitude (% rms) and a quality factor, Q, of approximately 11 and 4, respectively. The overall X-ray (0.3-10.0 keV) power spectrum in the frequency range 0.0001 - 0.1 Hz can be described by a power-law with an index of -2, and a QPO at 7 mHz. At frequencies > 0.02 Hz there is no evidence for significant variability. The fractional amplitude (rms) of the QPO is roughly energy-independent in the energy range of 0.3-1.5 keV. Above 1.5 keV the low signal to noise ratio of the data does not allow us to detect the QPO. By directly comparing these properties with the wide range of QPOs currently known from accreting black hole and neutron stars, we suggest that the 7 mHz QPO of IC 10 X-1 may be linked to one of the following three categories of QPOs: (1) the "heartbeat" mHz QPOs of the black hole sources GRS 1915+105 and IGR J17091-3624, or (2) the 0.6-2.4 Hz "dipper QPOs" of high-inclination neutron star systems, or (3) the mHz QPOs of Cygnus X-3.