  Accretion disks around compact objects are expected to enter an unstable
phase at high luminosity. One instability may occur when the radiation pressure
generated by accretion modifies the disk viscosity, resulting in the cyclic
depletion and refilling of the inner disk on short timescales. Such a scenario,
however, has only been quantitatively verified for a single stellar-mass black
hole. Although there are hints of these cycles in a few isolated cases, their
apparent absence in the variable emission of most bright accreting neutron
stars and black holes has been a lingering puzzle. Here we report the presence
of the same multiwavelength instability around an accreting neutron star.
Moreover, we show that the variability across the electromagnetic spectrum-from
radio to X-ray-of both black holes and neutron stars at high accretion rates
can be explained consistently if the accretion disks are unstable, producing
relativistic ejections during transitions that deplete or refill the inner
disk. Such new association allows us to identify the main physical components
responsible for the fast multiwavelength variability of highly accreting
compact objects.
