On the origin of the HLX-1 outbursts

HLX-1, currently the best intermediate-mass black hole candidate, has undergone seven violent outbursts, each with a peak X-ray luminosity of $L_{\mathrm{p}\mathrm{e}\mathrm{a}\mathrm{k},\mathrm{X}}\sim {10}^{42}\mathrm{e}\mathrm{r}\mathrm{g}{\mathrm{s}}^{-1}$. 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.