From Common Envelope to Pre-Cataclysmic Variables: An Observational Test of Common Envelope Evolution

Abstract

The generally accepted evolutionary scenario for cataclysmic variables (CVs) is common envelope (CE) evolution (Iben & Livio 1993) proposed by Paczyñski (1976). The secondary spirals towards the giant’s compact core converting orbital energy into kinetic energy of the giant’s envelope and the envelope is ejected. The dynamics of the red dwarf and red giant envelope interaction have been studied by several groups (Livio & Soker 1988; Taam & Bodenheimer 1991). After the ejection of the red giant envelope the post common envelope detached binaries (PCEBs) are formed. These can be divided into three groups:• Hot subdwarf with a red dwarf star inside a planetary nebula.• Hot subdwarf with a red dwarf star without a planetary nebula.• Hot white dwarf with a red dwarf star without a planetary nebula. Next, due to angular momentum loss by magnetic braking and/or gravitational radiation, the red dwarf component fills its Roche lobe and a cataclysmic variable is formed.