Quasi-Periodic Erupters: A Stellar Mass-Transfer Model for the Radiation

TL;DR

This paper proposes a stellar mass-transfer model involving a main sequence star orbiting a supermassive black hole to explain the properties of Quasi-Periodic Erupters, linking observed radiation features to the dynamics of mass transfer and shocks.

Contribution

It introduces a novel model connecting the radiation characteristics of QPEs to a star-black hole mass transfer process, emphasizing the role of shocks and magnetic turbulence.

Findings

Luminosity and spectrum consistent with mass transfer from a star to a black hole.

Repetition period and duty cycle explained by orbital dynamics and shock interactions.

Fluctuations in flare timing attributed to magnetic turbulence and irradiation effects.

Abstract

Quasi-Periodic Erupters (QPEs) are a remarkable class of objects exhibiting very large amplitude quasi-periodic X-ray flares. Although numerous dynamical models have been proposed to explain them, relatively little attention has been given to using the properties of their radiation to constrain their dynamics. Here we show that the observed luminosity, spectrum, repetition period, duty cycle, and fluctuations in the latter two quantities point toward a model in which: a main sequence star on a moderately eccentric orbit around a supermassive black hole periodically transfers mass to the Roche lobe of the black hole; orbital dynamics lead to mildly-relativistic shocks near the black hole; and thermal X-rays at the observed temperature are emitted by the gas as it flows away from the shock. Strong X-ray irradiation of the star by the flare itself augments the mass transfer, creates fluctuations in flare timing, and stirs turbulence in the stellar atmosphere that amplifies magnetic field to a level at which magnetic stresses can accelerate infall of the transferred mass toward the black hole.