The oEA Stars

We present the revised list of presently known oscillating massaccreting components of semi-detached Algol-type eclipsing binaries (oEA stars) and discuss the pulsation mode visibility and strategies of mode identification. On the example of the best studied oEA star RZ Cas we discuss the reasons for the observed orbital modulation of the pulsation amplitude. 1. The Group of oEA Stars The existence of a yet unrecognized new class of pulsating mass-accreting components of semi-detached eclipsing binaries was realized very recently (Mkrtichian et al. 2002b, 2003, 2004). The unique peculiarity of these so-called oEA (oscillating EA) stars consists of an ongoing mass transfer via the inner Lagrange L1 point and of the accretion of the transferred mass on the atmosphere of pulsating star. Mass accretion results in changing the mass, the radius and the density of the oEA star as well as its evolution that depends on the mass-accretion rate. Since 2000, 17 new pulsating components in Algol-type binaries have been found and studied within the framework of coordinated surveys of astronomers from Korea, Ukraine, USA, Kazakhstan, Belgium, Greece and Spain (Mkrtichian et al. 2002a, 2004, 2006; Kim et al. 2002b, 2002c, 2003, 2004a, 2004b, 2005a, 2005b, Lampens et al. 2004, Jeon et al. 2006) and by others (Lazaro et al. 2001, 2002; Caton, 2004). These increased the total number of pulsators up