DRIPPING HANDRAILS AND THE QUASI-PERIODIC OSCILLATIONS OF THE AM-HERCULIS OBJECTS

AM Her objects exhibit periodic, quasi-periodic, and aperiodic variabi lity on timescales ranging from seconds to years. Here, we investigate a process for the production of aperiodic and quasi-periodic accretio n rate fluctuations. We consider the nonlinear dynamical model known a s the dripping handrail (DHR). The DHR, basically a model for certain types of spatially extended systems and loosely based on water condens ing on and dripping off a handrail, has recently been used as a model for the quasi-periodic oscillations and very low frequency noise of th e low-mass X-ray binary Sco X-1. Here, we show that (1) the DHR is a r obust QPO generation process in that it leads to QPO production under a wide range of conditions and assumptions; (2) the phenomenology of t he DHR is consistent with the observed aperiodic and quasi-periodic va riability of the AM Her QPO source VV Pup over timescales ranging from 16 ms to 20 a; and (3) a single DHR model can produce both broadband QPOs and features with quality Q > 20 as observed in several AM Her QP O sources.