Timing analysis of the black hole candidate EXO 1846-031 with Insight-HXMT monitoring

TL;DR

This paper presents a detailed timing analysis of the black hole candidate EXO 1846-031 during its 2019 outburst, identifying different states and analyzing QPO properties across multiple observations and energy bands.

Contribution

It provides new insights into the QPO behavior and physical properties of EXO 1846-031, including the QPO rms-frequency relationship and its potential dependence on source inclination.

Findings

QPOs observed in 0.1-8Hz range during outburst

QPO rms-frequency relationship shows a turning point around 2 Hz

QPO properties suggest a non-thermal origin

Abstract

We present the observational results from a detailed timing analysis of the black hole candidate EXO 1846-031 during its outburst in 2019 with the observations of Insight-HXMT, NICER and MAXI. This outburst can be classfied roughly into four different states. Type-C quasi-periodic oscillations (QPOs) observed by NICER (about 0.1-6Hz) and Insight-HXMT (about 0.7-8Hz) are also reported in this work. Meanwhile, we study various physical quantities related to QPO frequency.The QPO rms-frequency relationship in three energy band 1-10 keV indicates that there is a turning pointing in frequency around 2 Hz,which is similar to that of GRS 1915+105. A possible hypothesis for the relationship above may be related to the inclination of the source, which may require a high inclination to explain it. The relationships between QPO frequency and QPO rms,hardness,total fractional rms and count rate have also been found in other transient sources, which can indicate that the origin of type-C QPOs is non-thermal.