A New Evolutionary Picture for CVs and LMXBs

Abstract

We consider an alternative to the standard picture of CV and LMXB evolution, namely the idea that most CVs (and by extension LMXBs) may not yet have had time to evolve to their theoretical minimum orbital periods. We call this the Binary Age Postulate (BAP). The observed short-period cutoff in the CV histogram emerges naturally as the shortest period yet reached in the age of the Galaxy, while the post-minimum-period space density problem is removed. The idea has similar desirable consequences for LMXBs. In both cases systems with nuclear-evolved secondary stars form a prominent part of the short-period distributions. Properties such as the existence and nature of ultrashort-period systems, and the spread in mass transfer rates at a given orbital period, are naturally reproduced.