Accretion Rates in X--Ray Bursting Sources

Abstract

We present estimates for the accretion rates in 13 X--ray bursting sources which exhibit photospheric expansion, basing on theoretical models of stationary, radiatively driven winds from neutron stars. The relatively high values obtained, $\Mdot_{acc}\magcir 10^{-9} \MS$, are in accordance with theoretical limits for unstable helium burning, and, at the same time, almost never exceed the ``dynamical'' limit for stationary accretion, $\sim 10 \Mdot_{Edd}$. The only exceptions are 1820-30, already known to be a very peculiar object, and 1608-522; there are indications, however, that in both sources, accretion could be non--stationary.