  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.
