Inclination dependence of QPO phase lags in black hole X-ray binaries

Abstract

Quasi-periodic oscillations (QPOs) with frequencies from ∼ 0.05-30 Hz are a common feature in the X-ray emission of accreting black hole binaries. As the QPOs originate from the innermost accretion flow, they provide the opportunity to probe the behaviour of matter in extreme gravity. In this paper, we present a systematic analysis of the inclination dependence of phase lags associated with both Type-B and Type-C QPOs in a sample of 15 Galactic black hole binaries. We find that the phase lag at the Type-C QPO frequency strongly depends on inclination, both in evolution with QPO frequency and sign. Although we find that the Type-B QPO soft lags are associated with high inclination sources, the source sample is too small to confirm this as a significant inclination dependence. These results are consistent with a geometrical origin of Type-C QPOs and a different origin for Type-B and Type-C QPOs. We discuss the possibility that the phase lags originate from a pivoting spectral power law during each QPO cycle, while the inclination dependence arises from differences in dominant relativistic effects. We also search for energy dependences in the Type-C QPO frequency. We confirm this effect in the three known sources (GRS 1915+105, H1743-322 and XTE J1550-564) and newly detect it in XTE J1859+226. Lastly, our results indicate that the unknown inclination sources XTE J1859+226 and MAXI J1543-564 are most consistent with a high inclination.

A review of quasi-periodic oscillations from black hole X-ray binaries: Observation and theory

“…Left: Amplitude of the QPO fundamental versus the centroid frequency for many observations [159]. Right: Phase lag of the QPO fundamental between hard (∼ 7 − 13 keV) and soft (∼ 2 − 7 keV) energy bands (positive means hard photons lag soft) versus centroid frequency [233]. Individual observations of low and high inclination sources are dark and light grey respectively.…”

“…van den Eijnden et al [233] used a sample slightly extended from the Motta et al [159] analysis (with the main difference being the inclusion of data from GRS 1915+105) to study the inclination dependence of the phase lag between hard (∼ 7 − 13 keV) and soft (∼ 2 − 7 keV) photons measured at the QPO fundamental frequency and its overtones. Fig 16 (right) shows their result for the Type-C QPO fundamental.…”

Analysis of Quasi-periodic Oscillations and Time Lag in Ultraluminous X-Ray Sources with XMM-Newton

“…Finally, the p-value is 0.1679, which would not reject the null hypothesis; namely, we cannot reject the hypothesis that the the ULX QPOs are type-C QPO analogs with this small sample of sources-i.e., the ULX QPOs have a chance of being type-C QPO analogs. Recently Van den Eijnden et al (2017) analyzed the relation between the phase lags of Type-B and Type-C QPOs and the inclination of the StBH. The phase lag at the Type-C fundamental QPO frequency depends significantly on source inclination.…”

“…This is good evidence that QPO results from Lense-Thirring precession. Van den Eijnden et al (2017) discussed the lag of Type-C QPO arising from the precession. Soft lags of Type-C QPOs are associated with high-inclination objects at high frequency.…”

“…Soft X-ray lags in neutron-star XRBs (4U 1608-52, 4U 1636-53, see de Avellar et al 2013), AGNs (RE J1034+396, see De Marco et al 2013a) and StBHs (GX339-4, see Miyamoto et al 1993;Uttley et al 2011) have been observed and interpreted as due to reverberation (De Marco et al 2013b). This reverberation is the result of the reflection of X-rays by a geometrically thin and optically thick accretion disc (Shakura & Sunyaev 1973).…”