HLX-1 may be an SS433 system

TL;DR

This paper proposes that HLX-1 is a stellar-mass binary system similar to SS433, observed along its X-ray beams, explaining its light curve and extreme luminosity through geometric collimation and precession.

Contribution

It introduces a new interpretation of HLX-1 as a beamed stellar-mass binary system, linking its properties to known systems like SS433 and explaining its observed features.

Findings

HLX-1's light curve is consistent with precessing X-ray beams.

The system's distance aligns with expectations for a highly-beamed source.

The model explains HLX-1 as an extreme ULX member.

Abstract

We show that the hyperluminous source HLX--1 may be a stellar--mass binary system like SS433, but seen along its X--ray beams. The precession of these beams gives the $\sim 1$~yr characteristic timescale of the light curve, while the significant X--ray duty cycle means that the precession angle must be comparable with the beam opening angle, which is of order $1.6^{\circ}$. The X--ray light curve appears to result from geometric collimation and scattering as the beam moves through the line of sight. Encouragingly, the distance $\sim 95$~Mpc suggested for HLX--1 is only a few times larger than the minimum distance at which we can expect to view such a highly--beamed system along its axis. This picture allows a simple interpretation of HLX--1 as the most extreme known member of the ULX population.