Wavelet analysis of low-frequency quasi-periodic oscillations in MAXI J1803$-$298 observed with Insight-HXMT and NICER

TL;DR

This study uses wavelet analysis on data from Insight-HXMT and NICER to investigate low-frequency QPOs in MAXI J1803-298, revealing distinct behaviors of Type-C and Type-B QPOs and their energy-dependent origins.

Contribution

It introduces a wavelet-based method to analyze QPOs, classifies their types based on properties, and explores their energy and count correlations, providing new insights into QPO origins.

Findings

S-factors decrease with QPO frequency for Type-C

S-factors remain stable around zero for Type-B

Different S-factor and count correlations suggest dual origins

Abstract

With data observed by the Hard X-ray Modulation Telescope (\textit{Insight}-HXMT) and the Neutron star Interior Composition Explorer (\textit {NICER}), we study low-frequency quasi-periodic oscillations (LFQPOs) of the black hole candidate MAXI J1803$-$298 during the 2021 outburst. Based on hardness intensity diagram and difference of the QPOs properties, Type-C and Type-B QPOs are found in the low-hard state and soft intermediate state, respectively. After searching for and classifying QPOs in Fourier domains, we extract the QPO component and study it with wavelet analysis. The QPO and no-QPO time intervals are separated by the confidence level, so that the S-factor, which is defined as the ratio of the QPO time interval to the total length of good time interval, is calculated. We found S-factors decrease with QPOs frequency for Type-C QPOs but stay stable around zero for Type-B QPOs. The relation of S-factor of Type-C QPOs and photon energy, the correlation of S-factor and counts are also studied. Different correlation of S-factor and counts for different energy bands indicates different origins of QPOs in high energy and low energy bands, which may be due to a dual-corona scenario.