Does the Mass Accretion Rate Depend on the Radius of the Accreting Star?

In some circumstances, the mass accretion rate M^dot onto a compact star maydepend not only on external boundary conditions, but also on the radius R ofthe star. Writing the dependence as a power-law in which M^dot is proportionalto R^p, we estimate the power-law index, p, for transient binary systems in aquiescent state. We use the observed luminosities $L$ of accreting neutronstars (R=10^6 cm) in soft X-ray transients and white dwarfs (R=10^9 cm) insimilar cataclysmic variables, and estimate M^dot in each system through therelation L=(GM/R)*M^dot, where M is the mass of the star. From the availabledata we infer that p~0.9+-0.5. This radial dependence is consistent withradiatively inefficient accretion flows that either are convective or lose massvia a wind.Comment: 11 pages, 1 figure, submitted to ApJ