On the origin of the HLX-1 outbursts

TL;DR

This paper investigates the physical mechanisms behind HLX-1's recurrent outbursts, proposing that radiation pressure instability in black hole accretion explains their evolution and properties.

Contribution

It constrains the physical parameters of HLX-1's outbursts and demonstrates that radiation pressure instability can account for their observed behavior.

Findings

Outbursts are consistent with radiation pressure instability.

The model explains the evolution of outburst recurrence times.

Properties align with black hole accretion physics.

Abstract

HLX-1, currently the best intermediate-mass black hole candidate, has undergone seven violent outbursts, each with a peak X-ray luminosity of $L_{\mathrm{peak},\mathrm{X}}\sim 10^{42}\ \rm{erg\ s^{-1}}$. Interestingly, the properties of the HLX-1 outbursts evolve with time. In this work, we aim to constrain the physical parameters of the central engine of the HLX-1 outbursts in the framework of the black hole accretion. We find that the physical properties of the HLX-1 outbursts are consistent with being driven by the radiation pressure instability. This scenario can explain the evolution of the recurrent timescales of the HLX-1 outbursts as a function of the durations.