The energy dependence of the three types of low-frequency quasi-periodic oscillations in the black hole candidate H1743−322

Abstract

We investigate the properties of the centroid frequency of low-frequency quasi-periodic oscillation (LF QPOs, 0.1–30 Hz) during the 2003 outburst of H1743−322, by using the observational data of the Rossi X-ray Timing Explorer. We find that the frequency shows different energy dependences for each of the sub-classes of LF QPOs: the QPO frequency is proportional to photon energy for the type C QPOs while it is ambiguous for the type A and B QPOs. For type C QPOs, the slope of the frequency–energy relation versus frequency plot can be well described by a power law with frequency till ∼7.5 Hz. Beyond ∼7.5 Hz the slope goes down. The LF QPO amplitude decreases monotonically with the frequency for the type C but increases for the other two types. These properties provide a joint diagnostic for discriminating the different types of LF QPO.