Stream Overflow in Z Cha and OY Car during Quiescence

Abstract

Eclipses of the hot spot in Z Cha and OY Car observed by many authors during their quiescence are re-analyzed. Distances of the spot from the center of the disk r_s are determined from phases of ingress and egress. In the case of several eclipses of Z Cha and nearly all eclipses of OY Car it is found that r_s(egress) < r_s(ingress). This implies that they are not representative for the radius of the disk r_d and is interpreted as being due to the stream overflow. The r_s(ingress) - dt relations (where dt is the time since last outburst) are improved when points affected by the stream overflow are omitted.