On the modulation of low frequency Quasi-Periodic Oscillations in black-hole transients

TL;DR

This study investigates the modulation mechanisms of low-frequency quasi-periodic oscillations in black hole transients by analyzing their spectral properties, revealing different modulation behaviors for fundamental, harmonic, and sub-harmonic peaks.

Contribution

It provides new insights into the nature of QPO modulation by comparing properties across multiple black hole candidates and previous sources, highlighting differences in amplitude and frequency modulation.

Findings

Fundamental and first harmonic widths are compatible with frequency modulation.

Sub-harmonic width appears independent of frequency, indicating amplitude modulation.

Results suggest different modulation mechanisms for various QPO components.

Abstract

We studied the properties of the low-frequency quasi-periodic oscillations detected in a sample of six black hole candidates (XTE J1550-564, H 1743-322, XTE J1859+226, 4U 1630-47,GX 339-4, XTE J1650-500) observed by the Rossi XTE satellite. We analyzed the relation between the full width half maximum and the frequency of all the narrow peaks detected in power density spectra where a type-C QPO is observed. Our goal was to understand the nature of the modulation of the signal by comparing the properties of different harmonic peaks in the power density spectrum. We find that for the sources in our sample the width of the fundamental and of the first harmonic are compatible with a frequency modulation, while that of the sub-harmonic is independent of frequency, possibly indicating the presence of an additional modulation in amplitude. We compare our results with those obtained earlier from GRS 1915+105 and XTE J1550-564.